The System Developing of Intelligent and High-precision
Contents
1. as well as standard and advanced communication interfaces up to two I2Cs three SPIs two I2Ss one SDIO five USARTs an USB and a CAN These properties can meet the AT7022 CFl VOUT OUT AT7022 CF3 VOUT OUT R3 R4 R5 R6 330R 10K 330R 10K Ul OUT CFI 2 OUr CR A A v YA v YA oo I Dar o Pour AT7022 CF2 VOUT OUT AT7022 CF4 VOUT OUT R11 R12 R13 R14 330R Us 10K 330R US 10K OUT CF2 OUT CF4 A A Vv VA Vv Va pap Pl GND OUT poe PI GND OUT Pl VOUT OUT 6 5 OUT CFI 4 OUT CF2 3 OUT CF3 2 __OUI CM 1 pa Header 6GND OUT control acquisition processing algorithms design requirements Besides its high performance to price ratio also is the one of reasons why we choose it ATT7022B chip is used to acquire power parameter data in our system ATT7022B is highly accurate three phase power metering chip for three phase three wire and three phase four wire applications integration of six second order sigma delta ADC voltage reference circuit and all the digital signal processing circuits of power energy voltage and current RMS power factor and frequency measurement This chip provides an SPI interface which can easily transmit the data of2. measurement parameters and table parameters between the external MCU and itself Besides its internal voltage monitoring circuit can guarantee it working properly when the chip power on and off The chip can directly measure the power parameters but accuracy is not ideal Therefore we must use power spectral density algorithm to correct acquisition parameters 9 2 2 Power Parameter Acquisition Circuit Design ATT7022B is a semiconductor integrated chip so that it cannot directly connect high voltage or high current signal for power parameters In order to measure these parameters we isolate the signal from power grid at the same time the strong signal is converted to small one and then put these converted signal into ATT7022B for measuring ATT7022B peripheral circuit is referred to the chip manual we can see it in Fig 2 Avoiding unnecessary interference we let part of unused pins disconnect or connect ground the chip SPI communication interface connect to the STM32 I O ports for transmitting command or data DGND DGN 24 S76MHZ Al HTI a 15P VBB5VO VDD3V3 D S Oz VDDSVO a anon oc A Aaa a A Salala oa tooo Re RRE lt lt DGND YA QT SD 00 MO IN AAA NON Nana aa en WB 2 33 aaa a EY ATI02 REST 1 ppg SOP BPO e 31 ATOCHA AT7022 8IG_ 2 ga cp _AT7022 0F3 VIP
3. 6 2004 pp 645 649 8 Wei J D Sun C T Constructing hysteresis memory in neural networks JEEE Transactions Systems Man Cybernetics Vol 30 Issue 4 2000 pp 601 609 9 Jang X G A CCD driver based on programmable logic device J Foreign Electronic Elements Vol 11 1996 pp 41 43 10 Ai L L Yuan F Ding ZH L Measurement of spatial object s exterior attitude based on linear CCD Chinese Optics Letters 2008 Vol 6 Issue 7 pp 505 509 11 Texas Instrument CC2430 Datasheet 200715 2014 Copyright International Frequency Sensor Association IFSA Publishing S L All rights reserved http www sensorsportal com CALL FOR PAPERS Geneva Switzerland CICG Geneva International Conference Centre Pe e gt IA 17th European Co on Power Pleci A 1 ics x and Applicatio ns i Digest deadline _ Notification deadlir TEE Te T ig ee x Final paper deadli E E ES A ade A ese my pa oe a Yet et LS T A s i ee cab Pa d oe nce Keep wy oS A O 15 N da 2014 darch 2015 ie 1 June 2015 Es En a http pr epe2015 com 180
4. OSC_IN PDO POO lt E zp PD2 34 ee To PC2 DSGND e ES a all PC3 C20 8MHz 60 _ 24 PC4 B BOOTO PC4 Ea 2 PCS NRESET T 37 LEDI 22P R29 RS te 38 LED2 10K _ a p 40 Ea DI DSGND gt o PC10 SDIO D2 USART4 TX 52 PC11 SDIO D3 USART4 RX 53 PC12 SDIO CK USART5 TX R36 PC12 lt 3 10K PC13 TAMPER RTC ul NRESET PC14 OSC32_IN ae VDD3V3 VBAT PC15 0SC32 OUT m 0H a 104 32 YDD vss 1 H H 8 vpp2 A C2 26 sides 19 VDD3 VSS3 a 6 8P VDD3V3 VDD 4 vss 4 _ L3 s DU TAY L 10mH_ C28 DSGND STM32F103R6T6 10U 0 1U L DSGND EN VDD3V3 DSGND l i 3 tu os 0 1U 0 1U 0 1U 0 1U DSGND 000000 Fig 5 Mini system circuit design of STM32 HuO0O000 Fig 6 System board layout gt gt Y O O O O O O Y 177 Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 where u n and i n are the discrete sequences which is transformed from measured voltage and current signals respectively by the sampling holding and A D conversion N is a frequency period of sampling points Single phase active power 1s P UlIcos 6 where U and are the voltage and current RMS cos is the power factor of the load Besides active power can also be calculated by the following formula pr P Oia 7 Discretizing Equation 7 we have 1 N I P u n i n 8 N rizo In the three phase four wire circuit the to
5. P P P Power gain correction Energy Epa calculation three phase active power P P P P Fig 8 Active power measurement block diagram 4 Testing When we calibrate the power meter of power parameter measurement we must provide a standard meter Compared with standard meter only the active should be calibrated and reactive power does not require calibration After calibrated accuracy of active power measurement can achieve up to 0 5s Power correction is divided into ratio error correction and phase error correction Ratio error correction removes the ratio error in transformer Nonlinear of transformer ratio error cannot be ignored when it needs precision measurement ATT7022B offers 178 register Iregchg compensation can be set based on the current size of the staging area Besides phase error correction also can be corrected segmentally In applications the segments do not need to separate too small Phase error correction should do after completing ratio error correction Ratio error correction should be performed when power factor equal to 1 0 and phase error correction should be performed at 0 5 L 10 We can read register HFConst directly from ATT7022B to know the pulse frequency of output CF which is selected to calibrate the meter HF Const cannot be written more than 0x000D00 of Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 parameter values The constant frequency puls
6. RC fL 1 where R 12k In ATT7022B each of the AC input channel requires a superposition of a DC bias voltage as shown in Fig 4 The REFO resistor is used to provide the DC bias voltage and the DC bias voltage can be obtained by the chip voltage reference voltage output or can be provided from an external reference voltage ATT7022B has a SPI serial communication interface which communicates in slave mode having two control lines and two data lines CS SCLK DIN and DOUT Considering the SPI transmission signal line may be disturbed or jitter so we put a small resistor 10Q in series with the signal line This 176 resistor and IC input parasitic capacitance C can be combined to become a low pass filter to eliminate any oscillation of SPI interface signals r a C OO AGND Fig 4 Reference voltage input interface 2 3 Processor Circuit Design Fig 5 illustrates the mini system circuit design of STM32 which includes a reset circuit clock circuit and STM32 processor circuit As we can see STM32 not only controls logic controller to send the data but also communicate with the PC via RS232 or RS485 interface 2 4 PCB Layout Design We design two layers PCB board for our system by using Altium Designer the PCB board size is supposed to meet the size requirements of external mechanical structure the system board layout shown in Fig 6 System board layout the minimum line width of 8mil the min
7. Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 www sensorsportal com Sensors 4 Transducers 2014 by IFSA Publishing S L http www sensorsportal com The System Developing of Intelligent and High precision Power Parameter Measurement in Power System Based on Power Spectral Density Algorithm Huimin ZHANG Department of Communication Chongqing College of Electronic Engineering Chongqing 401331 China Tel 8613206006614 E mail Zhuomi99 126 com Received 28 July 2014 Accepted 30 September 2014 Published 31 October 2014 Abstract In modern power systems high precision power parameter measurement has occupied an important position for power quality in power grids This paper presents a high precision intelligent power parameter measurement device which can collect parallel alternative current parameter values among 0 to 250 V in 3 channel easily and quickly and improve the measurement accuracy by using the power spectral correction algorithm for sample parameters The ATT7022B chip is used as the front end of the data acquisition and we use STM32 chip as the processor which is easy to implement the algorithm on this platform Results obtained from test application of the entire system show that the system has advantages of stable performance small size high reliability and excellent accuracy Copyright 2014 IFSA Publishing S L Keywords Power parameters Power spectral density High precisio
8. cted Acknowledgements Chongqing Vocational and Technical College Applied Technology Promotion Center Projects to promote the application of new technologies STM32 based wireless lights integrated management system Reference 1 SUN He lin Lu Yuan long TIAN Yue jun Remote power quality monitoring system based on GPRS and virtual instruments Relay Vol 35 Issue 1 2007 pp 59 62 2 Sun Guo dong Lei Zai shuan Zhou Yu guo et al Design of Comprehensive Electrical Power Monitoring Device Electrical Measureme Instrumentation Vol 44 Issue 7 2007 pp 37 40 3 Lei Yang Guang ming Huang et al The realization of automatic correction table platform Electrical Measurement amp Instrumentation Vol 44 Issue 5 2007 pp 58 60 4 Chen Tao He Wei Liu Xiao Ming et al An on line ultraviolet detecting system of EHV transmission lines Automation of Electric Power Systems Vol 29 Issue 7 2005 pp 88 92 S Liu Hai Chang Liu Hao Wang Jiao Xia et al Design and implementing of remote power quality monitoring system Power System Protection and Control Vol 37 Issue 1 2009 pp 109 111 179 Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 6 Intel Corporation Intel MCS 51 microcontroller family user s manual http www intel com 2006 05 20 7 Li Xia Sun Hui A novel divider based on dual bit algorithm Chinese Journal of Semiconductors Vol 25 Issue
9. e is EC rated input voltage is Un rated input current 1s Ib voltage of sampling voltage channel is Vu voltage of sampling current channel is Vi ATT7022B gain is G Therefore we calculate the value of HF Const 2 HF INT 5760000000421 aD U_ XI xEC where INT means to take the integer part When Uzain 0 voltage correction register can be read directly from ATT7022B by SPI interface the value is DataU Then we can read the actual input voltage RMS U from standard meter We know actual input voltage RMS is U measuring voltage RMS is U DataU x a Omg so we have oe e oan 1 13 If UU INT UL DOE U3 OU HINT SU x The RMS output register of ATT7022B is supplementary code the highest bit is the sign bit RMS is always greater than or equal to 0 so the maximum sign bit is always equal to 0 The 24 bit data Vins convert to actual voltage RMS is Ua A CO ts 14 The reference power spectral density correction algorithm to correct for acquisition parameters the main process of calibration Parameter settings A phase correction B phase correction C phase correction Where the parameter set is divided into the voltage channel ADC gain select high frequency pulse output setting ratio error compensated area setting phase compensation area setting loss of pressure threshold setting the starting current setting energy accumulation mode setting and the other parameters of the phase correction
10. ilap Ne Ly VIN 4 an CE 28 AT7022 CF 5 REFCAP cri 2 AT1022 CFI V3P 6 26 AT7022 SEL je ok V3P SEL ms C10 _V3N TN NB 10uF 16y 104 a EP AGND TEST gt DGND 1 eno PB g an DGND gt REFO 11 VSN gt IO E gt EER a REFOUT lt gt gt lt gt gt gt gt gt gt AGND Cll ATT7022D 104 ea e Se esi A aa eS ss gt gt gt gt gt oaz AGND a VDD5V0 Fig 2 ATT7022B peripheral circuit 175 Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 ATT7022B analog input circuit shown in Fig 3 Firstly the voltage directly access into circuit through the voltage divider and then superimposed on a reference voltage signal Finally this signal will be transmit into A D converter for sampling c4 001 AGND II AGND 0 01U Ql AIN b Fig 3 a The measured voltage input interface b current detection input interface From ATT7022B chip manual we know that ATT7022B voltage channel input range from 0 V to 1 V the current channel input range from 2 mV to 1 V And its sampling rate is 3 2 kHz therefore the input frequency greater than 1 6 kHz will form aliasing frequency at low frequency band we usually choose a simple RC filter to filter these high frequency components For power chip the useful signal only near by the sampling frequency of the signal so the bandwidth is generally from 0 to 2 KHz The filter cutoff frequency is fL 1 3k by the formula are 1 2 I
11. imum line spacing 8mil smallest hole is 16mil is a high wiring density on the PCB board 3 Power Spectral Density Correction Algorithm According to electrical theory valid values of periodically changing voltage and current signals lr U irae u t dt 2 eS l t t where T is the period of the signals We discretize Equation 2 and Equation 3 we have U a 4 N 20 I ES 5 N m0 Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 U6 PA0 U2 CTS 14 26 PBO AT7022 REST RI y 15 a n 27 PBI PA2 U2_TX TH oo PB2 PA3 U2 RX 7 iS PB3 TDO AT7022 CS 0 CR 20 oe es DES PB4 TRST R24 AT7022 SCK 0 CR3 21 Dz PBS 10K AT7022 DOU 0 CR4 22 O ES PB6 I2C1 SCL AT7022 DIN 0 CR5 2 Me PB7 I2C1 SDA i DSGND AT7022 SIG 0 CR6 41 61 PB8 PA9 Ul_ TX 42 te no 62 PB9 PA10 U RX ra we PB10 U3 TX AT7022 SEL_ R7 y 44 oa ee PB11 U3_RX AT7022 REVP 0 45 O PB12 U3 CK ar PA13 TMS mE a ries ie PB13 U3 CTS PA14 TCK 49 35 PB14 U3 RTS L go PAI4 ITCK SWCLK PB14 lt E PA1S JTDI PBIS C18 2
12. n Measurement ATT7022B 1 Introduction Electrical energy has become a part of our life therefore and power quality is related to all aspects of our social life The measurements of these parameters are directly reflected in the power quality of the power supply therefore monitoring power parameters in power grids has important practical significance 2 Due to the wide coverage of power grids there is a considerable number of disperse nodes need to detect Therefore that how to monitor the power parameters in real time effectively is still required to be continually studied According to this situation we designed a high precision intelligent power parameter measurement device which can quickly and easily achieve a single system of parallel acquiring parameter values from O to 250 V in 3 channel the power parameter measurement in this paper mainly discusses the measurements of voltage 174 RMS URMS the current RMS IRMS the apparent power S the active power P the power factor o and other parameters of alternative current working at 50 Hz then correct the sampled parameters by using power spectral algorithm to improve the electric parameter measurement accuracy The results show that the system has advantages of stable performance small size high reliability and excellent accuracy 2 Hardware Design 2 1 System Design According to the demand for measuring power parameter we build a wireless network monit
13. oring system The structure is shown in Fig 1 http www sensorsportal com HTML DIGEST P_2456 htm Sensors amp Transducers Vol 180 Issue 10 October 2014 pp 174 180 Channel CPU STM32F 103RET6 ATT7022B Voltage Input Channel DATA Interface Fig 1 Measurement error characteristics of sensor As is shown in Fig 1 the system uses STM32F103RET6 as the main module which has rich on chip resources of peripheral module to expand trunk RS232 UART Power Measurement Module SPI and other functions The main function of the system is to complete the parameter measurement of power equipment in operation in real time and reach the target of real time monitoring Therefore the module of power parameter measurement is an important part of the system In order to getting more comprehensive parameters of power equipment operation we decided to use specific single chip solution with digital signal processing methods simultaneously capture three wire power line voltage current and other parameters 5 We choose STM32F103RET chip as the processor which based on the ARM Cortex M3 32 bit RISC core operating at a 72 MHz frequency high speed embedded memories Flash memory up to 512 Kbytes and SRAM up to 64 Kbytes and an extensive range of enhanced I Os and peripherals connected to two APB buses All devices offer three 12 bit ADCs four general purpose 16 bit timers plus two PWM timers 8
14. steps Power gain correction P 1 0 phase error correction P 0 5 L voltage correction rated voltage current correction rated current Test environment Laboratory temperature Test objects 220 V 25 W incandescent 220 V 60 W incandescent transformers power supply As we can see from the Table 1 the power parameters which correct by power spectral density power correction algorithm differ from the nominal value But the result is same with the test values of standard correction meter indicating that the system is able to achieve high precision measurement of power parameters 11 Table 1 Test Results Voltage Current 220 V 25 W 213 3V 012A incandescent 9 W transformers power supply PAN uals 212 5V 027A incandescent 5 Conclusion This paper presents a developing method of high precision power parameter measurement equipment based on power spectral density correction This method can correct power parameter error and has high precision in correction Besides the algorithm is simple and is very suitable for high precision measurement of power parameters However because the power parameter measurement device itself can only collect three voltage and current values the accuracy of the data must be referred to standard measuring instruments and it cannot achieve self correcting which leads to the range of application of high precision power parameter measurement devices in some extent will be restri
15. tal active power equal to sum of each phase of active power can be written as PHP ri elas 9 In three phase three wire circuit the total active power can be measured by two Wattmeter method P P Pr 10 Voltage sampled values High pass filter Voltage sampled values High pass Phase filter correction Power parameters of the sampling system can provide fundamental harmonics and voltage of each phase and three phase full wave RMS voltage vector and a full wave current RMS and RMS phase current vector Grid voltage signal is converted to the sampling values by ADC of ATT7022B chip and then 1t can be sent to the STM32 processor family unit operation finally we can get its RMS value After reading the corresponding value of the register we right 13 bit to obtain the required measurements Measurement block diagram shown in Fig 7 Voltage sampled i T values High pass ii Square Urmsa i filter x Digital iter Root gt Fig 7 RMS measurement block diagram When we remove the DC component from the voltage or current signals after a series of multiplications additions and digital filtering we can get the active power of each phase Voltage and current sampling data contains 21 order harmonic and based formula is 1 N P 2U 2 1 n gt 11 N n 0 Calculating active power contains at least 21 order harmonic information Active power measurement block diagram shown in Fig 8 is P
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