3-Phase AC Induction Motor Control with PFC
Contents
1. Part of parameter file define CPU_FREQUENCY_MHZ 40 0 CPU FREQUENCY 40 000 000 Hz define SYSTEMCLOCK FREQUENCY MHZ CPU_FREQUENCY_MHZ define BUSCLOCK FREQUENCY MHZ CPU FREQUENCY MHZ 2 0 define STATOR FREO MAX 100 0 Hz 5 7 Microcontroller Memory Usage Table shows how much memory is needed to run the 3 phase AC drive in a speed closed loop A signie cant part of the microcontroller memory is still available for other tasks Table 5 1 Application Memory Usage Memory Type Available on MC9S08MP16 Used without FreeMASTER Program Flash 16 KByte 4800 Bytes Unified Data Program RAM 1 KByte 233 Bytes 5 8 Conclusion The design of a speed closed loop drive with a 3 phase AC induction motor was described in this Design Reference Manual It is based on Freescale s MC9SO8MP16 microcontroller It illustrates the drive from a system point of view the power stage hardware around the microcontroller with sensors and finally the software The described design shows the simplicity and efficiency of using the MC9SO8MP16 microcontroller for motor control and introduces it as an appropriate candidate for different low cost applications in both industrial and appliance fields 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 12 Freescale Semiconductor2. Ts i Counter reg i l of PDB timer i PDB2DLYB l f 4 f f 1 l PDB2DLYA 1 4 ns DP tM i lx y L ii it L T i TUps Voltage V Duty cycle PWM T us Switching periode Figure 2 11 PFC PWM Generation Timing In a normal operation the PDB2 Timer is restarted by an inductor current zero crossing signal The red area in Figure 2 12 indicates the state when the inductor current zero crossing signal is lost In this case the PDB2 timer must be restarted by a software trigger because the current zero crossing signal is not available when the input line voltage signal is close to zero The red area is detected when the input voltage falls under a certain level typically 35 V This level indicates the setting of fall compare flag in HSCMP3 When the input voltage level rises again and the rise compare flag is set in HSCMP3 PDB2 is switched back to a hardware trigger HSCMP3 rise flag a zero detect is lost HSCMP3 fall flag ref Vi gt F HSCMP3 Out MN Enable PWM time ms SW TRIG E Disable PWM l 450 us time ms Figure 2 12 PFC Critical Zero Detect Area 3 Phase AC Induction Motor Control with PFC
3. Figure 2 3 Volts per Hertz Control Method Unfortunately the Volts per Hertz ramp is designed for nominal motor load conditions If the conditions are not nominal the motor does not work at the optimal level and the performance and efficiency are bad The optimal slip control algorithm resolves such disadvantages 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 4 Freescale Semiconductor Control Theory 2 2 2 Constant Slip Control From motor control theory it is known that a slip frequency exists when the motor efficiency is at its highest Close to that slip frequency there is another where the phase current is at its lowest this means that the inverter losses are the lowest The compromise between these two parameters is the constant optimal slip frequency when the system efficiency is the best This optimal slip frequency significantly depends neither on electrical sine frequency nor the motor load The optimal slip frequency can be determined by the drive efficiency measurement or by a calculation To control a drive with high efficiency this feature is applied The system concept of a constant slip speed closed loop control is shown in Figure 2 4 Speed Command Roauired MC9S08MP16 Speed Voltage FreeMASTER Speed QO c e ie AAS a E Controller Amplitude m Integrator Phase fi Optimal Slip Actual Speed Speed Tacho Signal Calculation Figure 2 4 Control Concept
4. Fault Processing The speed closed loop control is characterized by the measurement of the actual motor speed This value is compared with the reference value required speed as an output of the speed ramp and the error signal is generated The magnitude and polarity of the error signal corresponds to the difference between the actual and required speed The PI controller generates stator voltage amplitude value based on the speed error in order to compensate the error A 3 phase motor is supplied with sinusoidal voltage wave generated by the PWM unit FTM2 of the microcontroller The parameters are the frequency phase and the voltage amplitude Control algorithm calls one of the control modes depending on motor conditions Amplitude 100 VOLTAGE CONTROL see Figure 2 5 The frequency is calculated as the sum of the actual speed and the optimal slip frequency 4 Hz for the tested drive The voltage is adapted according to the load using a PI controller It means that for different loads the amplitude of the supply voltage differs 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 5 Control Theory PWM s Speed Required Command Speed Amplitude Sine PWM Output Sine Generation Frequency Sine phase Integrator _ Actual Motor Speed Optimal Slip Figure 2 5 Voltage Control Concept e Amplitude reaches 100 FREQUENCY CO
5. MC9S08MP16 HSCMP2 FTM1 Passive Capture Input Input M4 Tacho period ACIM Filter Output Input Input P1 Clk lock DAC2 System clock 8 Output Figure 2 8 Tacho System Configuration The actual rotor frequency can be expressed as speed s Eqn 3 T FTMfreq Eqn 4 4x StatorMaxFreq x p speed calculated actual rotor frequency Hz k scaling constant 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 8 Freescale Semiconductor Control Theory T period of a half motor mechanical revolution s FTMfreq FlexTMR frequency for tacho edge input capture Hz StatorMaxFreq Maximal scaling stator frequency Hz Dp motor pole pair number Hz The rotor frequency is calculated using the tacho generator frequency value per half of a motor mechanical revolution The timer FTMI running with frequency FTMfreq is employed for capturing the edges coming from the internal high speed comparator HSCMP2 The minimum rotor frequency which can be detected using the presented tacho generator is set to 1 2 Hz while the maximum measurable speed is limited to 100 Hz in the presented application 2 4 Power Factor Correction Control The boost and the buck boost topologies are popular within the field since they produce a higher DC output voltage than the peak input voltage which means lower average output currents The basic topology of a boost converter is shown in Figure 2 9 The boost topology has b
6. Conduction Mode Implementation The PFC can be incorporated as a part of every system which is supplied from the AC mains This section describes the implementation of the PFC running in Critical Conduction Mode into 3 phase ACIM V Hz control The system concept is shown in Figure 2 10 PWM signal generation for the PFC switch is performed by the on chip peripheral PDB2 set to mode ONE SHOT and the registers set to the following values e PDB2DLYA 1 constant value e PDB2DLYB duty cycle PI controller output value calculated in the 1 ms loop The variable switching frequency depends on the input voltage the level and level of output current The duty cycle of the PWM pulses is defined by the voltage PI controller the PWM period is defined by the input current zero cross detection The timing diagram shows PFC PWM signal generation see Figure 2 11 Vin Filter Rectifier km L Z AC 230V Output voltage 380 V O ero detect Power t Supply PFC Driver S08MP16 HSCMP1 Period Zero detect PDB2 PDB2DLYB PDB2DLYA EN DI Duty Cycle Enable Disable Ret DAC3 PWM Sw TRIG V DCreq ee Over voltage ADC PI controller Vpcactual Figure 2 10 PFC System Concept 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 10 Freescale Semiconductor Control Theory Voltage V Zero current detect of PFC Ext trig inductor
7. ERR CR FCR Rai 1 Lee PIOOREE pec oap ab arde d e aola dd Bee M dr He M ad od oa eR cb M ee 1 Chapter 4 Hardware Hardware Implementation 3231 C ERU ed Ree RE Oe ee ee CR 1 MC9S08MP16 Daughter Board for UHV Power Stage 00002 eee ee eee 2 3 Phase Universal High Voltage Power Stage 000 c eee eee ees 3 PEO Nt sh hg oe ee a als fio WA ee a ke a 6 Motor Specifications Example 000 ss eos da s curan kd eked Rn RR RR wen 7 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 3 Freescale Semiconductor 1 Chapter 5 Software Design mr Sie 2523 955 PER E ds ee One Rd car Oa OO RSs RPO Ree 1 52 Main Software PICO A da eR REOR EADOX M ca RRP EON OVE eee eee 1 5 3 Application Overview Luis aaa zr ees sb ido ed eee REESE RS dolce ee ee ee UR e ed 2 B Se GES aens kc Re AE aic dO ACRCRCR CR ee E bo DEOR UR TRACCE C E 3 541 IANO 6 60 09 88S deiteen shee RO ddr a a a SER 22d 5 5 4 2 Application Background Loop sisse ew rh RO RR Ran 6 ms DENIS 4354443 he Ip iip octo doc Odd hehe nh ca e od RU d Ed 6 Sas Ebrary PURUS 25 FIC oes d p ap dba RR RC CAR OR apa dida OA UP CR RN eie dr 8 5 5 FresMASTER Software 1uuuuadadasudud d ha d we ds ao Ua dense Bod ca di ene d d d 8 5 5 1 FreeMASTER Serial Communication Driver 0 00 cece eee 9 5 5 2 PIBSMASTER Record f iuslucuuusaxkbtesu ke ensis os Rx Ad A dr RR ROI 10 5 5 3 FreeMASTER Control Page iud Kane IRR dedo o XOUERCR CR anama 10 5 6 Setting
8. Manual Freescale Semiconductor 2008 5 Code Warrior Development Studio for Freescale Microcontrollers V6 2 Freescale Semiconductor 2008 6 AN2395 PC Master Software Usage Freescale Semiconductor 2002 7 3 Phase PM Synchronous Motor Vector Control AN1931 by Prokop L Grasblum P 2005 8 Embedded Software Library for S08 User s Manual Freescale Semiconductor 2009 For a current list of documentation refer to www freescale com 1 3 1 Acronyms and Abbreviations Table 1 1 contains sample acronyms and abbreviations used in a document Table 1 1 Acronyms and Abbreviated Terms Term Meaning AC Alternating current ACIM AC Induction Motor ADC Analog to digital converter BDM Background Debug Mode COP Computer Operating Properly watchdog timer CSC Constant Slip Control DT Dead time a short time that must be inserted between the turning off of one transistor in the inverter half bridge and turning on of the complementary transistor due to the limited switching speed of the transistors GPIO General purpose input output y o Input output interfaces between a computer system and the external world a CPU reads an input to sense the level of an external signal and writes to an output to change the level of an external signal LED Light emitting diode MC9S08MP16 A Freescale family of HCS08 dedicated to motor control PFC Power Factor Correction PLL Phase locked loop a clock generator
9. circuit in which a voltage controlled oscillator produces an oscillation that is synchronized to a reference signal PWM Pulse width modulation RPM Revolutions per minute 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor Introduction Table 1 1 Acronyms and Abbreviated Terms continued Term Meaning SCI Serial communication interface module a module that supports asynchronous communication V Hz Volts per Hertz 1 3 2 Glossary of Symbols Table 1 2 shows a glossary of symbols used in this document Table 1 2 Glossary of Symbols Term Definition Ns synchronous stator speed fs synchronous stator frequency Pp stator pole pair number p stator pole number slip relative angular velocity Os flux wave velocity Or mechanical angular velocity 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 7 Introduction 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 8 Freescale Semiconductor Chapter 2 Control Theory 2 1 3 Phase AC Induction Motor The AC induction motor is a rotating electric machine designed to operate from a 3 phase source of alternating voltage For variable speed drives the source is normally an inverter that uses power switches to produce approximately sinusoidal voltages and currents of controllable magnitude and frequency The
10. enable e PDBI ADC triggering using the FTM2 trigger e PDB2 output pulse generation software trigger enabled e ADC enabled hardware trigger from PDB1 12 bit conversion short time sample three ADC channels enabled Vip DC bus current and voltage e MTIM compare mode ms enabled interrupt e HSCMPx all comparators set to compare an external signal zero cross tacho signal input voltage with an internal reference signal set by DACx e DACx internal reference for HSCMPx e O port enable the pullup resistor for Txd and Rxd set the PWM pads to low in the case where the FTM2 module is disabled e SCI 9600 bauds FreeMASTER FMSTR Init Finally interrupts are enabled and the FAULT state is set 5 4 2 Application Background Loop The endless application background loop executes the following functions e FreeMASTER polling function FMSTR Poll e Watchdog periodic feeding The main application control tasks are executed in the interrupt service routines which interrupt the background loop 5 4 3 Interrupts There are two periodic interrupt service routines executing the major motor control tasks Control tasks are split into fast and slow control loops Each loop has a corresponding priority The interrupt service routines and control tasks executed by each interrupt are described in the following subsections 5 4 3 1 FTM2 Overflow Interrupt The function FTM2 Overflow i
11. is defined as a Volts per Hertz control because the voltage applied command is calculated directly from the applied frequency in order to maintain the air gap flux of the machine constant In a steady state operation if it is assumed that there is a negligible voltage drop across the stator resistor the machine air gap flux is approximately proportional to the ratio V f where V is the amplitude of a motor phase voltage and f is the synchronous electrical frequency applied to the motor However when the frequency and voltage are low the voltage drop across the stator resistance cannot be neglected and has to be compensated for The control system is illustrated in Figure 2 3 The characteristic is defined by the base point usually 50 Hz or 60 Hz of the motor Below the base point the motor operates at optimum excitation called constant torque operation because of the constant V f ratio Above this point the motor operates under excited called constant power operation because of the rated voltage limit Since the air gap flux is a maintained constant constant V f ratio independent of the applied synchronous electrical frequency the torque produced depends on the slip frequency only Thus regulating the slip frequency the torque and speed of the ACIM can be controlled with the constant V Hz technique Volt per Hertz Characteristic Motor Base Point Amplitude Base Frequency Frequency Frequency Frequency
12. of the programmable gain amplifiers and ADC 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 4 Freescale Semiconductor The PDB2 features used in the application e Single shot mode Output PWM PFC pulse generation with precisely controlled rising and falling times e Both hardware and software triggering The HSCMPI1 High speed comparator features used in the application Input current zero cross detection for PFC Compare level set by the DACI e Inversion on comparator output e Output used for hardware trigger The HSCMP2 features used in the application e Comparator of tacho signal Compare level set by DAC2 e Output used for period measurement The HSCMP3 features used in the application e Input low voltage level detection Compare level set by DAC3 The DACX features used in the application e Set compare level for each HSCCMPx The MTIM Modulo timer features used in the application e 8 bit modulo limit running Set time base for a 1 ms loop e Overflow interrupt generation 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Introduction Freescale Semiconductor Introduction 1 3 Bibliography 1 3 Phase Universal High Voltage Power Stage User s Manual Freescale Semiconductor 2009 MC9SOSMP16 Daughter Board for UHV Power Stage User s Manual Freescale Semiconductor 2009 3 PFC Board User s Manual Freescale Semiconductor 2009 MC9SOSMP 16 Reference
13. picture of the data processing functions within the developed software The variable names related to environmental information flow appear in normal text on the following diagram whilst the variable names related to information flow between functional elements appear in bold text and will be explained in the following The benefits of a structured modular software design are well perceived This is especially true for complex motor control systems with many interacting software sub blocks Due to these factors the Freescale library set for the HCSOS8 has been developed including for example a V Hz profile Ramp and a 3 phase sinus generator The application software is interrupt driven when running in real time There are two periodic interrupt service routines executing the major motor control tasks see Figure 5 2 The application supports two speed control algortihms V Hz and CSC Switching between algorithms can be done from both the FreeMASTER control page in the motor STOP state or in the source code main c using define for a permanent change of control routine 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 2 Freescale Semiconductor Software Design The V Hz ACIM control process provides most of the motor control functionality It is regularly executed mainly in the speed processing interrupt MTIM Overflow It performs the state machine speed control loop and the PFC control loop with a
14. poll driven communication mode It does not require the setting of interrupts for SCI Both communication and protocol decoding are handled in the application background loop The polling mode requires a periodic call of the FMSTR Poll function in the application main The driver is configured using the appconfig h header file Changes to the file are preferably made through the provided Quick Start graphical configuration tool in CodeWarrior toolbar Project Configuration Tool The user has to modify this file to configure the FreeMASTER driver The FreeMASTER driver C source files include the configuration file and use the macros defined there for conditional and parameter compilation A detailed description of the FreeMASTER Serial Communication Driver is provided in AN2471 PC Master Software Communication Protocol Specification 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 9 Software Design 5 5 2 FreeMASTER Recorder Part of the FreeMASTER software is also a recorder which is able to sample the application variables at a specified sample rate The samples are stored in a buffer and read by the PC via an RS 232 serial port The sampled data can be displayed in a graph or the data can be stored The recorder behaves like a simple on chip oscilloscope with trigger pretrigger capabilities The size of the recorder buffer and the FreeMASTER recorder time base can be defined in the ap
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16. states is shown in Figure 5 3 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 3 Software Design RESET FAULT udtAppStatus Bits FaultSet INIT udtAppStatus Bits InitDone CALIB udtAppStatus Bits CalibDone EXECUTE Figure 5 3 Application State Diagram After reset the application is set to the fault state where over current over voltage and under voltage fault bit states are tested If there is no fault detected the application goes to the next state Once any of them are set the fault state is immediately entered The application states are described in the following sections 5 4 0 1 State FAULT The application goes to this state immediately after reset or when a fault is detected The system allows all the states to pass on to the FAULT state Faults detected in the application called function TaskFault are e Over current e Over voltage e Under voltage The next state INIT is set once all fault bits are cleared This means that no fault has been detected udtAppStatus Bits FaultSet 0 5 4 0 2 State INIT This transient state is entered from the FAULT state The application variable initialization is performed calling function TaskInit where all variables are initialized to their default values speed PI controller speed ramp increments phase increment and so on The system waits until the udtAppStatus Bits InitDone is set Then t
17. 1 PM Synchronous Motor Cross Section As the sinusoidally distributed flux density wave produced by the stator magnetizing currents sweeps past the rotor conductors it generates voltage in them The result is a sinusoidally distributed set of currents in the short circuited rotor bars Because of the low resistance of these shorted bars only a small relative angular velocity between the angular velocity of the flux wave and the mechanical angular velocity of the two pole rotor is required to produce the necessary rotor current The relative angular velocity is called the slip velocity oii Oslip 0 0 rad s 1 Eqn 2 2 The interaction of the sinusoidally distributed air gap flux density and induced rotor currents produces a torque in the rotor The typical induction motor speed torque characteristic is shown in Figure 2 2 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 2 Freescale Semiconductor Control Theory Torque p ree eee Braking Motor region region Generator region Generator TV lL l l lL 100 80 60 40 0 0 20 40 60 80 100 120 140 160 180 200 220 Speed in percent of synchronous speed 2 0 1 8 1 6 14 12 10 08 O6 04 02 O 02 04 0 6 0 8 1 0 1 2 Slip as a fraction of synchronous speed Figure 2 2 AC Induction Motor Speed Torque Characteristic Squirrel cage AC induction motors are popular because of their simple const
18. 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Design Reference Manual Devices Supported MC9SO8MP16 Document Number DRM115 Rev 0 11 2009 How to Reach Us Home Page www freescale com E mail support freescale com USA Europe or Locations Not Listed Freescale Semiconductor Technical Information Center CH370 1300 N Alma School Road Chandler Arizona 85224 1 800 521 6274 or 1 480 768 2130 support freescale com Europe Middle East and Africa Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen Germany 44 1296 380 456 English 46 8 52200080 English 49 89 92103 559 German 33 1 69 35 48 48 French support freescale com Japan Freescale Semiconductor Japan Ltd Headquarters ARCO Tower 15F 1 8 1 Shimo Meguro Meguro ku Tokyo 153 0064 Japan 0120 191014 or 81 3 5437 9125 support japan Q freescale com Asia Pacific Freescale Semiconductor China Ltd Exchange Building 23F No 118 Jianguo Road Chaoyang District Beijing 100022 China 86 10 5879 8000 support asia 9 freescale com For Literature Requests Only Freescale Semiconductor Literature Distribution Center 1 800 441 2447 or 303 675 2140 Fax 303 675 2150 LDCForFreescaleSemiconductor hibbertgroup com Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductor products There are no express or i
19. Current Sense Offset lottset VnEr V Bus Voltage Sense Voltage VBus 8 2 mV V Bus Voltage Sense Offset Vofiset 0 V Continuous Output Current Ic 15 A Deadtime built in power module tort 1500 ns Range set according 3 3 VA 5 VA power supply The values are measured at 25 C for other temperatures the values may be different heatsink 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Depends on used power module and Freescale Semiconductor Hardware 4 4 PFC Board The PFC board incorporates an input EMI filter PFC inductance PFC switch two diodes and input voltage sensing circuitry The design of the other components such as the DC bus capacitors input capacitor C1 fuse varistor thermistor current sensing circuitry and output voltage sensing circuitry will not be mentioned here because they are parts of the 3 phase Universal High Voltage Power Stage rather than the PFC itself I pa D n EW o D Figure 4 5 PFC Board with EMI Filter The PFC hardware is shown in Figure 4 5 The presented PFC concept is assigned to run in Critical Conduction Mode in a boost converter topology It is targeted at medium power range 250 W 750 W applications PFC main features e Critical conduction mode PFC Boost Converter Topology Input voltage Vi 90 265 V AC 50 60 Hz Regulation output voltage 380 V approximately 5 rip
20. Frequency Amplitude PWMO 5 V Hz or CSC Algorithm Tacho Speed Calculation _LF 1 Tacho t Motor Application State Machine FreeMASTER E B ils Figure 3 1 System Concept 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 3 System Concept 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 4 Freescale Semiconductor Chapter 4 Hardware 4 1 Hardware Implementation This application is designed to drive a three phase AC motor in a speed closed loop The application hardware system configuration is shown in Figure 4 1 Generator Motor Phases 90 260V Power Input Terminal 3 Phase Universal High Voltage Power Stage MC9S08MP16 Daughter Board for UHVPS J12 J6 2 l Opto Isolation amp J2 I d J1 o e 2 o di O A USB BDM Figure 4 1 Hardware System Configuration All system parts are supplied and documented High Voltage Daughter Board MC9S08MP16 Uses Freescale s MC9SO8MP16 as the controller Described in 4 2 MC9SO8MP16 Daughter Board for UHV Power Stage 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor Hardware e 3 Phase Universal High Voltage Power Stage High voltage 3 phase power board with single phase input 115 230 V AC and 1 000 VA variable voltage 3 phase IGBT bridge output D
21. Hila esa 11 eee po s ely EE ACIM VHz CSC PFC 3 1 OPEN LOOP voltage control Ha speed Designed by Ramay CSC EHS 2 ADC module A 4 DC Bus Voltage Transportation and Standard Products Group EME 4 CLOSED LOOP speed control Roznov pod Radhostem Czech Republic 5 Speed 4t Speed Controller 3 Phase ACIM V Hz Constant Slip Control 0 Mg M y 5 a 7 10 20 3m DC Bus Voltage v Z wey WM NN py Application Status Fault 9 Fault Clear e Manual Manual Control Figure 5 4 FreeMASTER Control Screen The following FreeMASTER software control page actions are supported e Setting the required speed of the motor e Switch running motor on off Switch between V Hz and CSC algorithms The FreeMASTER software control page displays Actual and required speed e DC bus current and voltage e Application fault status 5 6 Setting the Software Parameters for a Specific Motor The default software parameter settings have been tuned for a default hardware setup with the ATAS NT4C82 motor When another motor and hardware are used the software settings need to be changed according to their specific parameters All application parameters are defined in file main h and commented to help users modify parameters according to their requirements 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 11 Software Design
22. NTROL see Figure 2 6 For higher speeds and heavy loads when the amplitude given by the PI output reaches the maximum value it is necessary to increase the slip of the motor in order to achieve the desired speed The output voltage amplitude is a maintained constant maximal The machine transits to the field weakening region In this region the efficiency of the drive is decreased due to the slip increase PWM s Amplitude AMPLITUDE_MAX Output Sine PI Frequency Sine phase Controller Integrator Actual Motor Speed Figure 2 6 Frequency Control Concept In the case of an inertial load the motor can work like a generator during deceleration In opposite to a simple V Hz drive the generator mode must be detected and the control algorithm adapted The control error of the PI controller E n has to be calculated differently The generator region is sensed using following condition IF Actual rotor frequency Generated stator frequency THEN generator region ELSE gt motor region 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 6 Freescale Semiconductor Control Theory In the MOTOR region the control error E n is calculated as follows Error RequiredSpeed ActualSpeed In the GENERATOR region the control error E n is calculated as follows Error ActualSpeed RequiredSpeed 2 x OptimalSlip The rest of the control strategy is the same for b
23. PFC Automatic input voltage detection 110 V 60 Hz and 230 V 50 Hz DC bus voltage regulation 390 V DC 5 ripple for Pout 300 W Over voltage protection Power factor gt 0 94 230 V AC e Three phase high voltage 230 115 V power board e High voltage daughter controller board e PEC board with input filter e FreeMASTER software control interface motor start stop speed setup 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 1 Introduction e FreeMASTER software monitor FreeMASTER software graphical control page required speed actual motor speed start stop status DC bus voltage level motor current system status FreeMASTER software speed scope actual and desired speeds DC bus voltage and motor current Application ACIM V Hz CSC Design Reference Close Speed Loop with PFC ex Manual A43 Hardware implementation happiest deed w dioc a ese hunc AC metu eod e Figure 1 1 3 Phase AC Motor Control with V Hz CSC Speed Close Loop and PFC using MC9S08MP16 The main application components available for customers are e Software written in C code using some library algorithms available for the HCSOS8 Hardware based on the Freescale universal motor control hardware modules Documentation this document 1 1 2 Overview of Variable Speed Drives The design of cost effe
24. Using MC9S08MP16 Rev 0 Freescale Semiconductor 11 Control Theory 2 5 Current Sensing Flex Timer and ADC Synchronization This optional configuration shows how the AD converter module can by synchronized with the Flex Timer using a PDB It enables sensing the proper quantities of the phase or DC bus currents at the instant when current flows via the sensing shunt The sensed current is only an informative value and is not required in the presented control algorithm The over current state is detected by the power module and the fault signal is detected as an FTM fault trigger Other quantity sensing DC bus and input voltage can be triggered by the ADC software trigger without the necessity of a synchronization with the Flex Timer The FTM2 module is configured to run in combined center aligned mode with counter modulo FTM2MOD 1249 and the counter initialization register FTM2CNTIN 1250 which enable a center aligned mode with a switching frequency of 16 kHz at a 40 MHz system clock PWM cycle period 62 5 us The synchronization signal is generated every PWM cycle with a 62 5 us period The synchronization signal is connected to the PDB1 module program delay block to synchronize the PWM signal with analog quantity sensing The PDB1 module is configured in triggered mode synchronized with a FTM2 rollover event Delayed output triggers the AD converter to read the DC bus current samples in predefined time instants An over
25. age waves are shifted 120 to each another thus a 3 phase motor can be supplied 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 7 Control Theory 2 3 Speed Sensing Using AC Tacho Generator A tacho generator is a precision shaft mounted generator used to sense mechanical speed of motor rotation It generates an AC voltage which is highly linear in proportion to the actual motor speed and is used as a feedback signal required for a speed control loop The precision of speed measurement depends on the tacho generator pole pair number In the application the 8 pole pair tacho generator is used This generates eight periods of sinusoidal signal per each mechanical revolution The biggest problem of using a tacho as a motor speed transducer is that it does not work at zero and low speed operations which have to be compensated for by software The actual speed is calculated in the 10 ms loop As a comparator the on chip HSCMP2 High Speed Comparator is used The analog signal is limited to 3 3 V and connected to HSCMP2 positive input P1 The compared value is set by the internal DAC2 and connected to HCSCMP2 minus input M4 The comparator output is internally connected to the FTM1 input and using a capture event the period between the two comparator signal edges is obtained The actual motor speed is then evaluated from the captured tacho period System configuration is shown in Figure 2 8
26. annels One analog to digital converter ADC 13 channel 12 bit resolution 2 5 us conversion time One 8 bit modulo counter with an 8 bit prescaler and overflow interrupt e Interrupt Priority Controller IPC with four programmable interrupt priority levels Onedifferential Programmable Gain Amplifier PGA with programmable gain x1 x2 x4 x8 x16 or x32 e Three fast analog comparators HSCMP1 HSCMP2 and HSCMP3 with both positive and negative inputs e Three 5 bit digital to analog converters DAC used as a 32 tap voltage reference Two programmable delay blocks PDB PDB1 synchronizes the PWM with samples of the ADC PDB2 synchronizes the PWM with comparing window of analog comparators PWM output synchronizes with FTM PWM output e One serial peripheral interface SPI e One serial communications interface SCI with LIN slave functionality 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 3 Introduction e One inter integrated circuit PC port Onboard 3 3 V to 2 5 V voltage regulator for powering internal logic and memories Integrated power on reset and low voltage interrupt module e Multiplexing of all pins with general purpose input output GPIO pins e Computer operating properly COP watchdog timer e External reset input pin for hardware reset e Single wire background debug interface BDM e Internal Clock Source ICS Containing a freque
27. ctive variable speed 3 phase motor control drives has become a prime focus point for the appliance designers and semiconductor suppliers Replacing variable speed universal motors by maintenance free low noise asynchronous induction motors is a trend that supposes total system costs being equivalent The big push in this direction is given by several factors The new IEC555 1 European Community regulations dealing with electrical noise in power distribution Lines and low power consumption e The flexibility that can be achieved in using asynchronous motors with variable frequency 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 2 Freescale Semiconductor Introduction e The maturity level and affordable price trend of power devices e The system efficiency optimization that microprocessor controlled drives can provide e The size weight and dissipated power reduction of the motors for a given mechanical power Most usual variable speed ac induction motor drive designs contain a full bridge rectifier and a large DC bus capacitor at the input Such a circuit draws a peak current from the wall socket which provokes a high content of harmonics The low power factor PF as described in the present circuit reduces the necessary power from the mains and increases the efficiency of the mains supply network The international standard IEC1000 3 2 defines the limits of the harmonic content of the input current for
28. ductor 1 System Concept The power factor correction loop keeps a constant DC bus voltage using the PI controller The controller output provides the required duty cycle of the PFC PWM signal which is generated by the PDB module The application can be controlled via a FreeMASTER control page from a host PC The FreeMASTER communicates via the USB interface The USB connector is opto isolated to achieve safety isolation from high voltage The application state machine of the drive manages the operating states of the drive FAULT INIT CALIBRATION and EXECUTE The actual operating state is indicated by the FreeMASTER control page In the case of over voltage under voltage or over current the signals for the three phase inverter are disabled and the fault state is displayed 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 2 Freescale Semiconductor System Concept Power Line Input EMI Filter Vin Signal Conditioning Zero detect Zero Cross Detection Boost Converter 3PHUHVPS PFC Board MC9S08MP16 Vin Vin PWM Disable PDB PFC PWM PFC PWM EN Power Line In Vdcb required pur FreeMASTER AC to DC Input PFC Connection Connection Current amp E 5 Voltage B s Signal Processing EN tdcb ETUR IEEE Idcb FAULTO Over current Fault Power Module OC Fault Processing Sine PWM Generation FTM2
29. e as a sum of the actual speed and optimal slip Calculation of the maximal amplitude using the lookup table Limit the voltage amplitude utilizing the maximal amplitude Open loop startup up to the minimal measurable rotor speed e Calculate the voltage error as the difference between the required and sensed DC bus voltages e Execute the PFC PI controller which provides the duty cycle processed in PDB2 for PFC PWM signal generation e Perform software trigger for PDB2 in the case where a zero cross cannot be detected due to low input voltage 5 4 1 Initialization Application initialization is entered after a reset When the application main is entered a low level initialization is called The MCU registers are initialized according to the peripherals and the CPU This is the first function which has to be called in the application main As the next step the FreeMASTER embedded driver is initialized according to settings in the freemaster cfg h configuration file 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 5 Software Design The routine initializes the following modules and peripherals System init system clock 40 MHz watchdog clock e FTMI capture mode HSCMP2 output to timer input enabled interrupt e FTM2 combine mode output compare deadtime enabled enabled fault control synchronization on overflow external trigger generation to PDB interrupt
30. ecome the most popular topology A low side power switch enables utilizing a simple control technique Its only restriction is that the DC output voltage is higher than the highest expected AC voltage amplitude Filter Rectifier Output voltage 380 V Figure 2 9 Boost PFC Converter Concept Control of the power factor correction stage is a point of discussion and patent battling There are three general methods of control fixed on time mode critical conduction mode discontinuous continuous mode Fixed on time mode conversion consists of the minimum amount of circuitry but output current is limited to lower values Critical conduction mode conversion incorporates no output rectifier reverse recovery losses but output power is limited to the range of 300 to 600 W Continuous mode boost PFC circuits can achieve much higher output power but this brings significant rectifier reverse recovery losses However some zero transition loss circuits are implemented and the overall system cost is increased Additional cost is very important in this area since the power factor correction is an invisible benefit to the customers who do not want to pay for anything which cannot be seen directly The critical conduction mode is considered as most suitable for the presented application concept 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 9 Control Theory 2 4 1 PFC Critical
31. ector J11 Current measuring circuitry can be set up for 4 or 8 A full scale Both bus and phase leg currents are measured An over current trip point is set at 5 respective 10 A The high voltage power board provides an opto isolated SCI USB interface for communication with the FreeMASTER control application running on the host PC 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 4 Freescale Semiconductor INPUT PFC POWER VOLT DOUBLER MOTOR BRAKE RESISTOR 031 289 40 33 2 1 PH RECTIFIER PFC CONTROL POWER SUPPLY 15V_D 5V_D 3 3V_D 3 3V_A PCI Exp 64 BRAKE IGBT DIODE ENCODER HALL SENSORS POWER MODULE IGBT DRIVERS 3 PH IGBT BRIDGE SIGNAL CONDITIONING INPUT DC BUS PHASE voltages and currents ZERO cross temperature USB SCI with MC9S08JS16 Figure 4 4 3 Phase Universal High Voltage Power Stage Block Diagram Hardware Table 4 1 Electrical Characteristics of the 3 Phase Universal High Voltage Power Stage Characteristic Symbol Min Typ Max Units DC input voltage Vac 140 I 325 V AC input voltage Vac 100 240 V Logic 1 Input Voltage Vin 2 8 a V Logic 0 Input Voltage ViL 0 8 V Input Resistance Rin 5 kQ Analog Output Range Vout 0 3 3 V Bus Current Sense Voltage 8 amp scaling ISense 206 25 mV A Bus
32. escribed in 4 3 3 Phase Universal High Voltage Power Stage e Power factor correction board Input line filter and power factor correction implemented on one board Described in 4 4 PFC Board A detailed description of each individual board can be found in the appropriate user manual or on the Freescale web site www freescale com The user manuals include a schematic of the board a description of individual function blocks and a bill of materials parts list 4 2 _MC9S08MP16 Daughter Board for UHV Power Stage The MC9SO8MP 16 daughter board is based on an optimized PCB with an edge connector It demonstrates the abilities of the 8 bit MC9SO8MP16 MCU and provides a hardware tool to help in the development of applications that use the MC9SO8MP16 and are targeted at motor control applications The presented daughter board is a plug module type of board it includes the MC9SO8MP16 part the BDM interface and a power supply connector 9 12 V DC The interface between the power board and daughter board is provided via a 64 pin PCI express connector The MC9SO8MP16 Daughter Board for the UHV Power Stage is designed for these purposes e New users can become familiar with the features of the MC9SO8MP16 architecture e The board can serve as a platform for real time software development The tool suite allows developing and simulating routines the download of software to the on chip memory running the software and debugging it
33. he capture flag 5 4 4 Library Functions The application source code is based on the new Freescale Embedded Software Library for the S08 family of microcontrollers The library consists of two packs The basic math primitives S08 math and embedded control functions ECLIB For detailed information follow Embedded Software Library for S08 User s Manual Freescale Semiconductor 2009 Control routines incorporate the following library functions e ECLIB_Ramp16 for speed ramping the required speed obtained from the speed command e ECLIB 3phaseGen16 generates a 3 phase sine signal based on input amplitude and phase e ECLIB_VHzProfile16 lookup table for amplitude calculation using frequency e ECLIB ControllerPI16 16 bit Proportional Integral controller with limitation Plcontroller parameters consist of the gain and the gain scale parameters of the proportional and integral constants The proportional or integral gain parameter is the 8 bit unsigned number in the range of 0 to 255 representing 0 to 100 and the gain scale parameter shifts the particular gain to the left if positive The gain scale number represents the number of shifts The limit parameters represent the minimum and maximum outputs from the PI controller The output will be within these limits 5 5 FreeMASTER Software FreeMASTER software was designed to provide a debugging diagnostic and demonstration tool for the development of algorithms and a
34. he next state is entered 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 4 Freescale Semiconductor Software Design 5 4 0 3 State CALIB This transient state between the INIT and EXECUTE states enables the PWM pads to be set with fifty percent duty cycle and to measure the DC bus current quantity to set the offset value performed in the function TaskCalibration After udtAppStatus Bits CalibDone is set the next state is entered 5 4 0 4 State EXECUTE This is the most complex state and it performs the majority of tasks All necessary procedures for motor startup and rotation are processed in this state When the speed command is set to a non zero value the motor starts to run Otherwise the motor is in the stop state and the PWM signals are disabled Because the tacho generator cannot recognize motor rotation direction the state variables udtAppStatus Bits MotorDirFWD and udtAppStatus Bits MotorDirRWD reflect the motor direction accordingly Tasks performed in function TaskExecute e Count a 10 ms loop and calculate Actual rotor speed using the measured tacho period Required speed obtained using the Ramp function Speed command and Ramp increment as input parameters Speed error as the difference between the actual and required speeds Execute the PI speed controller Output of the controller is the required voltage amplitude Speed for the V Hz lookup tabl
35. ing the so called TSA Safety option the application memory can be protected from illegal or invalid memory accesses To include the new FreeMASTER Serial Communication Driver in the application the user has to manually include the driver files in the CodeWarrior project For the presented application the driver has already been included The FreeMASTER driver files are located in the following folders e Project sources contains freemaster cfg h freemaster h e Project sources freemaster contains platform dependent driver C source and header files All C files included in the freemaster folders are added to the project for compilation and linking see support group in the project The master header file freemaster h declares the common data types macros and prototypes of the FreeMASTER driver API functions This should be included in your application using include directive wherever you need to call any of the FreeMASTER driver API functions Note that the FreeMASTER driver does not perform any initialization or configuration of the SCI module it uses to communicate Therefore it is the user s responsibility to configure the communication module before the FreeMASTER driver is initialized by the FMSTR_Init call The default baud rate of the SCI communication is set to 9600 baud NOTE Higher communication speeds than 9600 baud can cause communication instability mainly when the Recorder function is used FreeMASTER uses a
36. ithms for both AC induction and brushless DC BLDC motors The 3 Phase Universal High Voltage Power Stage has a printed circuit board The printed circuit board contains an input rectifier brake IGBT and a diode a power module including an IGBT bridge and an IGBT gate drive circuit analog signal conditioning low voltage power supplies an SCI USB optically isolated interface and some large passive power components All of the power devices need to dissipate heat Thus the heatsink with required parameters is mounted on the bottom board side and the power devices are fixed to it 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 3 Hardware Sm SSS YV um T 5sy m y rp r E eer v Np A ee i OY 8 Figure 4 3 Universal 3 Phase High Voltage Power Stage Figure 4 4 shows a block diagram Input connections are made via the 64 pin PCI express connector J12 Power connections to the motor are made on the output connector J3 Phase A phase B and phase C are labelled Ph A Ph B and Ph C on the board Power requirements are met by a single external 140 to 325 V DC power supply or an 100 to 240 V AC line voltage Either input is supplied through connector J1 An external brake resistor can be connected via connector J2 The power stage can be extended by an external PFC board The PFC board connection is made via the power connectors J8 J9 and signal conn
37. mains supplied equipment To meet the norms the design requires a power factor correction at the input The present design allows simultaneous driving of the power factor correction algorithm and the AC induction motor This way significant cost reductions of the design can be achieved Moreover a wide range of input voltages from 90 V to 265 V AC and regulation of DC bus voltage can be achieved Another benefit of the design is the possibility of an easy modification of the system by software updates Two key requirements of the described design are that it has to be cost effective and highly reliable This design reference manual describes the basic motor theory system design concept hardware implementation and software design including the FreeMASTER software visualization tool 1 2 Freescale Controller Advantages and Features The MC9SO8MP16 is a member of the low cost high performance HCS08 Family of 8 bit microcontroller units MCUs All MCUs in this family use the enhanced HCS08 core and are available with a variety of modules memory sizes memory types and package types The Freescale MC9SO8MP16 microcontroller is well suited for digital motor control offering many dedicated peripherals such as Flextimer FTM modules analog to digital converters ADC timers communications peripherals SCI SPI PO and onboard flash and RAM The MC9S08MP16 device provides the following features Two Flextimer modules with a total of eight ch
38. mplied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Freescale Semiconductor reserves the right to make changes without further notice to any products herein Freescale Semiconductor makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Freescale Semiconductor assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability including without limitation consequential or incidental damages Typical parameters that may be provided in Freescale Semiconductor data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts Freescale Semiconductor does not convey any license under its patent rights nor the rights of others Freescale Semiconductor products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the Freescale Semiconductor product could create a situation where personal injury or death may occur Should Buyer purchase or use Freescale Semiconductor
39. ncy locked loop FLL controlled by internal or external reference 1 2 1 Peripheral Application Usage The ACIM V Hz and CSC with PFC benefits greatly from the flexible PWM module fast ADC high speed comparators HSCMP program delay block PDB and modulo timer MTIM The Flex Timer offers flexibility in its configuration enabling efficient three phase motor control Each FTM module supports an initialization trigger function which is used to trigger both PDBs The FTM1 Flex Timer module features used in the application e Input capture mode for tacho period signal measurement e HSCMP output connected to the FTM1 input The FTM2 Flex Timer module features used in the application Generation of six PWM signals Set combine mode with complementary outputs e Dead time inserted Fault protection enabled for external over current fault trigger e Synchronized PWM register update on timer overflow event Hardware trigger generation for ADC synchronization with the PWM signal optional feature not required for application functionality The ADC features used in the application Hardware trigger for the ADC start generated by the PDB1 e Linear successive approximation algorithm with 12 bit resolution e High speed conversion e 5 MHz module clock The PDBI Program delay block features used in the application optional not required e The controllable delay from the Flextimer module s SYNC output to the sample trigger input
40. oth motor and generator regions 2 2 3 Open Loop Startup The application utilizes an open loop startup from zero up to the minimal measurable rotor speed The generated tacho voltage is proportional to motor rotation and it generates an incomparable voltage signal from a zero speed up to the minimal measurable rotor speed see 2 3 Speed Sensing Using AC Tacho Generator Because of this speed sensor drawback during the motor startup the actual tacho speed is set to a minimal measurable speed which enables generating a speed error for the PI controller When the rotor speed can be sensed the speed control loop is closed 2 2 4 Digital Control of an AC Induction Motor In adjustable speed applications AC motors are powered by inverters The inverter converts a DC power to an AC power at the required frequency and amplitude Figure 2 7 illustrates a typical 3 phase inverter 3 Phase ES AC Motor Figure 2 7 Power Stage Schematic Diagram The inverter consists of three half bridge units where the upper and lower switches are controlled complementarily meaning when the upper one is turned on the lower one must be turned off and vice versa Because the power device s turn off time is longer than its turn on time some dead time must be inserted between turning off one transistor of the half bridge and turning on its complementary device The output voltage is mostly created by a pulse width modulation PWM technique The 3 phase volt
41. ow chart see Figure 5 1 incorporates the main routine entered from the reset state The main routine includes the microcontroller initialization FreeMASTER and state machine The microcontroller enters the reset processing state when a hardware reset signal is asserted Upon exiting the reset state the core enters the normal processing state and starts to execute the internal code The power on reset POR procedure is followed by the standard microprocessor startup sequence It is necessary to set up the occupied peripherals to their application correct initial values Application control is a software mechanism incorporating a state machine which governs the overall application operation and upon available data runs appropriate software states In run time conditions the hardware status is monitored such as power supply IC devices status and so on 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 1 Software Design Power on reset MCU Initialization Enable Interrupts State Machine FreeMASTER Poll Figure 5 1 Main Data Flow Q 5 3 Application Overview The top level diagram after the context diagram is created to show the main functional elements that occur within the developed software and to the information flows among these functional elements including the information that is either coming from or going to the environmental entities This diagram shows the wider
42. pconfig h configuration The recorder routine must be called periodically from the loop in which you want to take the samples The following line must be added to the loop code FMSTR Recorder FreeMASTER recorder routine call In this application the FreeMASTER recorder is called from the FTM2 Overflow interrupt which creates a 62 5 us time base for the recorder function A detailed description of the FreeMASTER software is provided in AN2395 PC Master Software Usage 5 5 3 FreeMASTER Control Page The FreeMASTER control page creates a graphical user interface GUI for the ACIM V Hz CSC control with the PFC Start the FreeMASTER software window s project by clicking on the ACIM VHz PFC pmp file Figure 5 4 illustrates the FreeMASTER software control window after this project has been launched To switch to the control page click on the control page tag A user is able to monitor all the important quantities of the motor By clicking the speed gauge the motor is started and the desired speed is set The actual motor speed motor currents and voltages are displayed on the control page gauges The application status is displayed A status fault LED indicates the occurrence of an application fault 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 10 Freescale Semiconductor Software Design F ACIM_ HZ_PFC_DRM pmp FreeMASTER la x Eile Edit Yiew Explorer Item Project Tools Help zuon
43. period of 1 ms The FTM2 Overflow FTM channel 2 interrupt service routine is executed on a PWM reload every 62 5 us It performs a PWM register update and analog values sensing Additionally there might be a FreeMASTER software recorder FMSTR Recorder routine used to monitor the application The background loop is executed in the application main It handles non critical timing tasks such as FreeMASTER communication polling The MC9SO8MP16 microcontroller provides programmable fault protection where a fault protection can disable any combination of PWM pins These faults are generated by logic one on any of the fault pins The fault pins are assigned to both Flex Timer modules When the fault protection hardware disables the PWM pins the PWM generator continues to run and only the output pins are deactivated If a fault is latched in it must be cleared and the fault state is invoked prior to enabling the PWM to prevent an unexpected interrupt Periodically 62 5us FTM2 Overflow DONE Periodically 1ms MTIM Overflow Initialization Background loop EVENT DRIVEN Comparator output IFTM1 _InputCapture DONE Tacho period Figure 5 2 Main Data Flow The individual processes of the control routines are described in the following sections 5 4 Software States The main application state machine has four application states FAULT INIT CALIB and EXECUTE Transition between the
44. ple for Pout 250 W e Variable switching frequency 50 kHz 350 kHz e Power factor gt 0 95 at 230 V AC THD 11 9 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 6 Freescale Semiconductor Hardware 4 5 Motor Specifications Example The motor used in this application is a standard production 3 phase AC induction motor with a tacho generator mounted on the shaft The motor is star connected The motor and sensor have these specifications Table 4 2 Specifications of the Motor and Speed Transducer Motor Type Three Phase AC Induction Motor ATAS NT4C82 Nominal Voltage line to line 400 V RMS Nominal Speed 2650 RPM Motor Specification Nominal Current phase 0 6 ARMS Nominal Power 180 Watts Number of Pole Pairs Type Alternate voltage Speed Transducer Specification Output 2 V AC 15 V AC Number of Pole Pairs 8 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor Hardware 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 8 Freescale Semiconductor Chapter 5 Software Design 5 1 Introduction This section describes the design of the drive s software blocks The software will be described in terms of Main Software Flowchart e Application Overview Software States e FreeMASTER Software e Application Parameters 5 2 Main Software Flowchart The main software fl
45. pplications Moreover it s very useful for tuning the application for different power stages and motors because almost all of the application parameters can be changed via the FreeMaster interface This consists of a component running on a PC and another part running on the target MCU connected via an RS 232 serial port A small program is resident in the MCU that communicates with the FreeMASTER software to parse commands return status information to the PC and process control information from the PC FreeMASTER software executing on the PC uses Microsoft Internet Explorer as the user interface 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 8 Freescale Semiconductor Software Design 5 5 1 FreeMASTER Serial Communication Driver The presented application includes the FreeMASTER Serial Communication Driver The FreeMASTER Serial Communication Driver fully replaces the former PC Master driver The new FreeMASTER driver remains fully compatible with the communication interface provided by the old PC Master drivers It brings however many useful enhancements and optimizations The main advantage of the new driver is a unification across all supported Freescale processor products as well as several new features that were added One of the key features implemented in the new driver is target side addressing TSA which enables an embedded application to describe the memory objects it grants the host access to By enabl
46. ruction low cost per horsepower and low maintenance they contain no brushes as do DC motors They are available in a wide range of power ratings With field oriented vector control methods AC induction motors can fully replace the standard DC motors even in high performance applications 2 2 AC Induction Motor Scalar Control Two speed control algorithms are incorporated in the presented application Volts per Hertz and Constant Slip Control The user can choose one of them using either definitions in the source code located at the beginning of the main c file or the FreeMASTER control page Both control methods are described in the following chapters 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 3 Control Theory 2 2 1 Volts per Hertz Control The Volts per Hertz control method is the most popular method of Scalar Control which controls the magnitude of variables such as frequency voltage or current The command and feedback signals are DC quantities that are proportional to the respective variables A simple open loop Volts Hertz speed control for an induction motor is the control technique targeted at low cost low performance drives This basic scheme is unsatisfactory for more demanding applications where torque control is required This drawback can be partly compensated for by implementing a closed loop speed control with a speed sensor as a feedback quantity This scheme
47. rved DRM115 Rev 0 11 2009 2 1 3 1 3 2 Chapter 1 Introduction lius ciis TRITT TP Terre 1 1 1 1 Application Features and Components 000 cece eee eens 1 1 1 2 Overview of Variable Speed Drives 0 00 ees 2 Freescale Controller Advantages and Features 000 cc cece eee eee 3 1 2 1 Peripheral Application Usage iiuccoca cu awake reside di daca dase eeees es 4 BDO E e ee kaa ek ead ada e 6 1 3 1 Acronyms and Abbreviations uua cc onde koe ORO CK 9 Ea o ORO ee OR RR E 6 1 3 2 Glossary of D50 219192 251 2 257 17 eck oes eee a e a 7 Chapter 2 Control Theory 3 Phase AC Induction MGI 2222 nada aan Rd eb Era dada xc RC RERE Rada 1 AC Induction Motor Scalar Control uuu dpa nou dre area Qe RC ed OR Cc ec cic 3 2 2 1 Vols per Herz COG i iaceo obo cor ees peccando d doe deed doc 4 22 2 Gonstant Slip Control 6 as id py 3r dab e PR Rea ode o oit ca od a dU d e 5 2283 DOSNPLOSD SAMUD usd hE KREG KR ER ERROR MER ERO OC e C POR QU eR RO 7 2 2 4 Digital Control of an AC Induction Motor 20 aaaeeeaa 7 Speed Sensing Using AC Tacho Generator aana 8 Power Factor Correction C BPPO auc qua escari dc rae eee ee bed dence OR EN ases dagud 9 2 4 1 PFC Critical Conduction Mode Implementation sss 10 Current Sensing Flex Timer and ADC Synchronization Ls 12 Chapter 3 System Concept Application CON 11424 eR RC 2 VERE CR RR eO
48. s FTM2 Counter Trigger 5 PDB1 Counter PDB1 Compare ADC Conversion FTM2 Overflow Figure 2 14 ADC Synchronization with FTM2 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 13 Control Theory 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 14 Freescale Semiconductor Chapter 3 System Concept 3 1 Application Description A standard system concept is chosen for the drive see Figure 3 1 The system incorporates these hardware boards e 3 Phase Universal High Voltage Power Stage e MC9S08MPI6 Daughter Board for UHV Power Stage e PFC board with input line filter e 3 phase AC induction motor default configuration for ATAS NT4C82 motor The MC9S08M16 populated on the controller daughter board executes the control algorithm In response to the user interface and feedback signals it generates PWM signals for the three phase high voltage power board High voltage waveforms generated by the DC to AC inverter are applied to the motor Input voltage is connected to the AC DC converter utilizing the Power Factor Correction Board in order to provide sinusoidal input current and to increase the PF power factor and THD Total Harmonic Distortion 3 2 Control Process The state of the speed transducer tacho generator is scanned periodically by the software timer loop while the speed of the motor is calculated utilizing the Input Cap
49. s an interrupt event The priority of the interrupt is set to level 3 It is executed on every PWM cycle A more detailed description of the FTM2 Overflow interrupt timing can be found in Section 5 4 3 1 FTM2 Overflow Interrupt The most time critical tasks of the V Hz control and PFC control algorithms are performed here including AD result register reading and AD channel setting The function is divided into two cases while each case is performed on every second interrupt event 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 6 Freescale Semiconductor Software Design Tasks performed by the FTM2 Overflow function Test PWMUpdate Read the ADC result register for the V quantity Set the AD channel for sampling the DCB Voltage resp DCB Current Update FTM2 compare register with the new duty cycle values and set SWSYNC bit to write new values in one Clear the PWMUpdate state bit Test NOT PWM Update Read the ADC result register for DCB Voltage resp DCB Current quantity Set the AD channel for sampling the V quantity Phase increment calculation 3 phase sinusoidal generator Duty cycle scaling Set the PWM Update state bit Test the HSCMP3 flag for falling edge Change PDB2 trigger to software trigger Clear the falling flag Test the HSCMP3 flag for rising edge Start the PDB2 using software trigger Change PDB2 trigger
50. stator is supplied by a balanced three phase AC power source The synchronous speed of the motor ns is given by 2x 60x xf n rpm Eqn 2 1 where f is the synchronous stator frequency in Hz and p is a stator pole number A cross section of a two pole induction motor is shown in Figure 2 1 Slots in the inner periphery of the stator accommodate the 3 phase windings a b c The turns in each winding are distributed so that the current in the stator winding produces an approximately sinusoidally distributed flux density around the periphery of the air gap When the three currents that are sinusoidally varying in time but displaced in phase by 120 from each other flow through the three symmetrically placed windings a radially directed air gap flux density is produced that is also sinusoidally distributed around the gap and rotates at an angular velocity equal to the angular frequency of the stator currents The most common type of an induction motor has a squirrel cage rotor in which aluminum conductors or bars are cast into the slots in the outer periphery of the rotor These conductors or bars are shorted together at both ends of the rotor by cast aluminum end rings which also can be shaped to act as fans In larger induction motors copper or copper alloy bars are used to fabricate the rotor cage winding 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 1 Control Theory Figure 2
51. the Software Parameters for a Specific Motor n nanana anaana nan 11 5 7 Microcontroller Memory Usage iu aao ce por a edhe eee dL RR wee EERE RR RC 12 56 SU 6 Jaslene 61 55 Tren 12 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 3 2 Freescale Semiconductor Chapter 1 Introduction 1 1 Introduction This document describes the cost effective design of a three phase AC induction motor V Hz and CSC constant slip control closed loop speed control and digital power factor correction PFC using the MC9SO8MP16 The design is targeted at consumer and industrial applications This cost effective solution benefits from the dedicated motor control features in the Freescale Semiconductor MC9SO8MP16 device 1 1 1 Application Features and Components The system is designed to drive a three phase AC induction motor The application features Targeted at the MC9SO8MP16 8 bit microcontroller e Three phase ACIM control using tacho generator as a rotary transducer Two control algorithms incorporating optionally set from FreeMASTER V Hz closed speed loop Constant optimal slip control in nominal speed range Controlled acceleration and deceleration Bidirectional rotation Both motor and generator modes PWM frequency 16 kHz Operation in FreeMASTER or demo operating mode Software over voltage and under voltage protection Hardware over current protection e Power Factor Correction
52. to H W trigger Clear the rising flag Call the FreeMASTER recorder routine Clear the overflow flag 5 4 3 2 Modulo Timer MTIM Compare Interrupt The function MTIM Overflow is assigned to this interrupt event The interrupt is executed periodically with a 1 ms period The priority of the interrupt is set to level 1 The MTIM_Overflow function executes the main state machine see Section 5 4 Software States which calls the state function accordingly Tasks performed by the MTIM Overflow function Select the actual state Execute the TaskFault function to check for fault occurrence Filter the DC bus voltage and DC bus current quantities Call the task function according to the actual application state Clear the overflow flag 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semiconductor 7 Software Design 5 4 3 3 FTM1 Capture Interrupt The function FTMI InputCapture is assigned to this interrupt event The interrupt is executed on an event When the HSCMP2 edge rising or falling is detected the actual FTMI counter value is captured and an interrupt event is generated The priority of the interrupt is set to level 2 Tasks performed by the FTMI InputCapture function Read the FTMI capture register e Calculate the period as the difference between previous and latest captured values Test the minimal measurable period e Save the period to a buffer e Clear t
53. ture interrupt The speed command is calculated according to the state of the control signals Start Stop Required Speed from FreeMASTER Then the speed command is processed by means of the speed ramp algorithm The comparison between the actual speed command obtained from the ramp algorithm output and the measured speed generates a speed error The speed error is processed by the speed PI controller that generates either a new corrected motor voltage amplitude or stator frequency depending on the control algorithm utilized Using a V Hz ramp the corresponding maximal voltage is calculated The PWM generation process calculates a system of 3 phase voltages of the required amplitude and frequency including dead time and finally the 3 phase PWM motor control signals are generated The input voltage DC bus voltage and DC bus current optional informative value are measured during the control process They are used for PFC control input voltage over voltage under voltage protection DC bus voltage and over current protection DC bus current of the drive The voltage protection is performed by means of software whilst the over current fault signal utilizes a fault input of the microcontroller If any of the above mentioned faults occur the motor control PWM outputs are disabled in order to protect the drive and the fault state of the system is displayed 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 Freescale Semicon
54. using a debugger via the BDM port a single wire background debugging interface that supports in circuit programming of on chip non volatile memory and sophisticated non intrusive debug capabilities The board facilitates the evaluation of various features present in the MC9SO8MP16 and can be used to develop real time software and hardware products based on the device It provides the features necessary to write and debug software demonstrate the functionality of that software and to interface with the customer s application specific device s 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 2 Freescale Semiconductor Hardware gt m E 3 a E a 6002 90 Figure 4 2 MC9S08MP16 Daughter Board for UHV Power Stage The MC9SO8MP16 daughter board provides all available MCU signal termination Hence the PCI express interface can provide connection with a corresponding power board see Figure 4 2 4 3 3 Phase Universal High Voltage Power Stage Freescale s 3 Phase Universal High Voltage Power Stage 3PHUHVPS shown in Figure 4 3 is a 1 000 voltamps 3 phase power stage that will operate off DC input voltages from 140 to 325 V and AC line voltages from 90 to 240 V In combination with one of the high voltage daughter boards it provides a software development platform that allows algorithms to be written and tested without the need to design and build a power stage It supports a wide variety of algor
55. view of the module interconnections is shown in Figure 2 13 PDB1 HW trigger Trigger 5 ADC Figure 2 13 ADC Triggering The timing diagram in Figure 2 14 shows how the triggered ADC conversion is performed The events are executed in the following steps which are numbered in the figure 1 The FTM2 counter reaches the MODULO value The FTM2 overflow occurs and the counter is set to zero The FTM2 overflow flag FTM2SC TOF is set to one and pending The synchronization signal TRIGGER 5 is generated by the FTM2 module 2 PDB channel 1 count is triggered by the TRIGGER 5 signal which is connected to its source input The timer starts counting up from zero 3 A compare on the PDB DELAYB register occurs The PDB1 output generates a synchronization pulse for the ADC 4 Arising edge on the hardware trigger input of the ADC module starts the ADC conversion 3 Phase AC Induction Motor Control with PFC Using MC9S08MP16 Rev 0 12 Freescale Semiconductor Control Theory 5 The FTM2 ISR is pending Previous AD conversion data is read a new AD channel for the next conversion is set In one FTM2 ISR the actual duty cycles are calculated and in the following FTM2 ISR the values of the PWM register are updated This means that the PWM register is updated every second FTM2 period 2 x 62 5 125 us For a detailed description of the FTM2 ISR follow 5 4 3 1 FTM2 Overflow Interrupt 125us PWM Cycle 62 5u
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