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IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 11, Issue 1 Ver. III (Jan. – Feb. 2016), PP 82-86 www.iosrjournals.org Microcontroller Based Digital Power Factor and Phase Angle Meter Kareem A. Hamad B.Sc, M.Sc, Ph.D AL – Rafidain University College, Computer Communication Eng. Dept Baghdad – Iraq Abstract: This paper deals with the development of an electronic power factor and phase angle meter using pic Microcontroller. The design is based on generating two signal values, the first is proportional to the peak value (Im) of the line current i(t), the second is proportional to the instantaneous value of the line current at the instant of v(t)=Vm , i.e. Imcosø, where Im is the peak value of the line current and ø is the phase angle between line voltage and line current. These two components are inserted into PIC16F877A by means of analog circuit. The power factor is calculated by division of these two components and the phase angle is then calculated as Cos-1ø.The calculated values will provide a realization and displayable form on LCD screen. Keywords: Microcontroller, Power factor, Phase angle Measurements. I. Introduction It is usually necessary to measure the power factor and phase angle of a power distribution system to assess its economy of transmission. The electro – dynamic power meters are sensitive to reliance on flux variation. The electronic design suffers from the problem of analog multiplication and division[1]. There are a lot of studies in this subject. M.F. Wagdy et al presents very simple method in phase measurement error compensation technique for automation [2]. Shu-Chen Wang and Chi-Jui Wu present accurate power factor measurement approach using FPGA [3]. Claudia A. da Silva et al. presents Power Factor Calculation by the Finite Element Method [4]. Mr. A Kumar Tiwari et al illustrates development of power factor controller using pic microcontroller [5]. Md. Shohe Rana et al proposes automatic power factor improvement by using ATmega8 microcontroller [6]. Ren Kaichun et al. presents Matlab simulations for power factor correction of switching power. The digital power factor and phase angle meters described in this paper employs generation of two values by means of analog circuit, these values are proportional to I m and Imcosø thus division by using microcontroller will result in cosø i.e power factor, the phase angle is then calculated as Phase angle = Cos-1ø. II. Principle of Operation Assuming the voltage and current waveforms are purely sinusoidal. Thus the instantaneous voltage v(t) and current i(t) are given as follows: v(t) Vm sin ωt And the power factor of the load is (1) i(t ) I m sin t (2) P.F cos (3) Where Vm is the peak value of the line voltage, I m is the peak value of line current, and ø is the phase angle between line voltage and line current (leading or lagging). Fig (1) Voltage and current signals DOI: 10.9790/1676-11138286 www.iosrjournals.org 82 | Page Microcontroller Based Power Factor and Phase Angle Meter Thus division of eqn. (4) by Im will give cos ø, i.e. power factor, Then III. Hardware description The design aims to monitor power factor and phase angle on LCD display continuously. The circuit diagram and corresponding timing waveforms of the system are shown in Figs. 2 and 3 respectively. The basic point in the proposed technique is to generate two values using ADC contained in the microcontroller, these values are proportional to Im and Imcosø. This has been achieved by taking the ADC values from current signals at its maximum value, i.e Im and at the instant of peak voltage V m , i.e. Imcosø. To achieve this aim electronically, We have used the step down arrangement of the transformer for voltage. Current signal can be acquired by using current transformer connected at main AC line. The line voltage V1 and line current I1 are shifted 90o, squared V2 and V3 respectively and reduced ON time with monostable V 4 and V5. Both Im and I1 current signals are converted in to digital signals with ADC of microcontroller, at the positive edges of V4 and V5, both signals of i(t) i.e Im and Imcosø are held, providing two components. Thus a division scheme between these two components is implemented to perform digital power factor (P.F = I mcosø/Im). The required division has been achieved with microcontroller PIC16F877A, the phase angle is then calculated as Cos -1ø. These two outputs is digitized and displayed on LCD accordingly. LM016L A LCD2 B C D3 U2(V-) 1N4148 10k 1k 1k 2 6 C1 D2 3 R3 2 3 LM741 7 1 RV2 0.22uF LM741 7 1 D2(A) 2 3 4 5 6 7 6 1k 1N4148 41% 100k U2(V+) 8 9 10 1 D12 3 4 5 9 11 RD0/PSP0 RD1/PSP1 RD2/PSP2 RD3/PSP3 RD4/PSP4 RD5/PSP5 RD6/PSP6 RD7/PSP7 74121 6 U20(V-) 15 16 17 18 23 24 25 26 19 20 21 22 27 28 29 30 6 1 33 34 35 36 37 38 39 40 PIC16F877A Q Q 6 R4 7 1 R5 LM741 Q U4 3 Q 10k RB0/INT RB1 RB2 RB3/PGM RB4 RB5 RB6/PGC RB7/PGD RA0/AN0 RA1/AN1 RA2/AN2/VREF-/CVREF RA3/AN3/VREF+ RA4/T0CKI/C1OUT RA5/AN4/SS/C2OUT RC0/T1OSO/T1CKI RE0/AN5/RD RC1/T1OSI/CCP2 RE1/AN6/WR RC2/CCP1 RE2/AN7/CS RC3/SCK/SCL RC4/SDI/SDA MCLR/Vpp/THV RC5/SDO RC6/TX/CK RC7/RX/DT 2 1N4148 D12(A) 10k OSC1/CLKIN OSC2/CLKOUT 10k U5 A1 A2 B RINT 10k RX/CX CX U4(V-) 1 1N4148 R2 BZX284C5V1 R17 4 5 D14 10 D5 D14(A) D0 D1 D2 D3 D4 D5 D6 D7 U1 13 14 U3 4 5 R1 D1 U2 4 5 R7 BZX284C5V1 R12 D3(A) 1N4148 7 8 9 10 11 12 13 14 1 2 3 5K 10k D4 RS RW E 52% R8 4 5 6 R8(1) VSS VDD VEE RV1 D U4(V+) U6 74121 3 CX RX/CX B A2 A1 6 10 C110 U20 11 2 9 1k 5 4 3 4 5 1k RINT R120 R110 RV20 0.22uF 39% 100k 7 1 LM741 U20(V+) Fig (2) Schematic diagram of measuring system DOI: 10.9790/1676-11138286 www.iosrjournals.org 83 | Page Microcontroller Based Power Factor and Phase Angle Meter Fig (3) Timing waveforms PIC16F877A Microcontroller The PIC16F877A is a microcontroller from Microchip in a chip type of 40-pin DIP packages. The principal characteristics by which this PIC was used are: digital I/O ports, analog inputs, analog to digital converter of 10 or 8-bit resolution, serial communication USART, memory storage EEPROM [7]. The PIC16F877A, has programmed routines process or features, such as analog to digital conversion to get the values from the sensors, storage of historic data in the internal EEPROM when an alert happened generates a detection range of values which can determinate whether the system suffered acceleration that cause an alert [8]. The circuit used in this work operates of 20 MHz clock frequency and runs each instruction as fast as 200 ns. The program for the PIC16F877A microcontroller is written in Micro C and is compiled into Hex program. Microcontroller is programmed to calculate power factor and phase angle. The flow chart of this calculation in Hex is shown in Fig. 4. The input of the current and voltage signals are connected to pin 4, 8 and 9 as shown in Fig. 2. IV. Software Components This section presents the software’s used in the design of the measuring system A. Micro C: Micro C is powerful, feature rich development tool for PIC micros. It designed to provide the programmer with the easiest possible for developing applications for embedded systems, without compromising performance or control [8]. B. Proteus 7 Professional: is an interactive system level simulator. Which combines mixed mode circuit simulation, micro-processor models and interactive component models to allow the simulation of complete micro-controller based designs [9]. DOI: 10.9790/1676-11138286 www.iosrjournals.org 84 | Page Microcontroller Based Power Factor and Phase Angle Meter Start Configure LCD port connections Configure ports directions Configure A / D converter Read I1 V5 =1 11 Y N V4 =1 N 1 Y I1 = Im I1 = Imcosø Calculate & Calibrate PF I m Cos Cos Im Phase angle Cos -1 Clear LCD Write PF on line 1 & value of Phase angle on line 2 of LCD Fig (4) Flowchart of power factor and phase angle measurement. Hex program Fig (5) The microcontroller inputs of the current and voltage signals DOI: 10.9790/1676-11138286 www.iosrjournals.org t 85 | Page Microcontroller Based Power Factor and Phase Angle Meter Fig (6) System linearity curve V. Conclusion This paper presented a simple approach to realize a digital power factor and phase angle meter based on PIC microcontroller. Which can be implemented in the various fields of industry and education. The circuit is designed to display PF and phase angle of the load connected the network. Calculation process is achieved by PIC16F877A. This approach is so straight forward that the hardware is very simple. The system has been tested under different loading conditions using proteus simulator and has shown linear behavior under those conditions, as shown in Fig.6 References [1]. [2]. [3]. [4]. [5]. [6]. [7]. [8]. [9]. Al – Ani. M. S. M. , and Abdul – Karim. M.A.H. , 1982, A digital power factor meter design based on voltage – to – frequency conversion. INT. Journal. Electronics. 52, 463 – 470. M.F. Wagdy, M.S.P. Lucas, 1986, A Phase-measurement error compensation technique suitable for automation, IEEE Transactions on Instrumentation and Measurement, IM-35 Vol.1, MARCH 1986. Shu-Chen Wang and Chi-Jui Wu, 2010, Design of accurate power factor measurement approach using fpga-based chip. Wseas Transactions on Circuits and Systems, Issue 7, Volume 9, July Claudia A. da Silva, Francis Bidaud, Philippe Herbet, and José R. Cardoso, 2010, power factor calculation by the finite element method. IEEE Transactions on Magnetics, Vol. 46, No. 8, August Mr. Anant Kumar Tiwari, Mrs. Durga Sharma, Mr.Vijay Kumar Sharma, 2014, automatic power factor correction using capacitive bank, Journal Of Engineering Research and Applications, Vol. 4, Issue 2( Version 1), February, pp.393-395 Md. Shohel Rana, Md. Naim Miah & Habibur Rahman,2013, automatic power factor improvement by using microcontroller, Global Journal of Researches in Engineering Electrical and Electronics Engineering, Volume 13 Issue 6 Version 1.0 Year 2013 Microchip 2001, PIC 16F87X Data Sheet, USA. Basil A., 2012, Alerting system design using PIC16F877a for power distribution system, The 4th International Engineering Conference –Towards engineering of 21st century. Kareem A. Hamad, 2014, Microcontroller based active and reactive power measurement, IJCER, Vol, 04, Issue, 7, July DOI: 10.9790/1676-11138286 www.iosrjournals.org 86 | Page