Design And Application Of A Control System For DC Motors Over Power Line

Transcription

1 Design And Application Of A Control System For DC Motors Over Power Line Alperen Mustafa Colak Electronic and Communication Engineering Cankaya University Ankara, Turkey alperenmustafacolak@gmail.com Ilhan Garip Strategy and Development Department TRT Ankara, Turkey milhangarip@hotmail.com Sevki Demirbas Electrical and Electronics Engineering Gazi University Ankara, Turkey demirbas@gazi.edu.tr AbstractCommunicating high frequency control signals over a power lines is well known and getting popular day by day. This technique is known as power line communication (PLC) and mostly used to control the loads in short distance. In this study, authors present to control a DC motor over a power line. For this purpose, a transmitter and receiver have been used on the power line. High frequency control signals are sent by the transmitter and received by the receiver at other side of the line. In this way, DC motors is run and stop. This whole system is controlled by a microprocessor PIC16F877A at 33 khz. Experimental results show that the proposed system is successful and can be applicable for controlling of other loads. Keywords- communication; PLC; transmitter; receiver I. INTRODUCTION Transmission of any electrical information (signal) from one point to another point over any power line is known as Power Line Communication (PLC) technology. PLC technology does not require any wired or wireless installation. PLC techniques are suitable for automation and control of different loads. Power lines have normally 50 Hz or 60 Hz low frequency as the transmitted signals on these power lines have high frequency of khz ranges. This frequency level is quite important and named as bandwidth of the system. [2]. An important problem in high bandwidth communication frequency is that interfering of signals to each other using the same frequency. In this case, serious communication problems can occur. Therefore, most of the recent studies have been concentrated on standardizations of maximum power levels and differences between communication frequencies [3]. These standards are named as Committee Europe ELECTROTECHNIQUE-the Normalization (CENELEC) in Europe and FCC in USA. Power line communication is determined by the rules of these two standards. These standards communication over power lines in the frequency range are divided into a certain band [4, 5]. Impedance compatibility is very important in communication systems. However, the energy line of communication is not appropriate for this, because the line impedance will vary according to region for different loads and different times. This change in impedance can be a few milliohms up to a few hundred ohms [6]. However, the power line communication has some difficulties. The most important of these difficulties are frequency changes in high voltage and its effects on the data transmitted. The power line causes these effects and that the attenuation of the data signal in the communication errors are formed [7]. Despite this drawback, due to the use of power line without additional cost, the development of communications networks, discount on the costs for renovation or re-installation, the electricity grid infrastructure constitutes an alternative. Power line communication used in most of the areas such as home automation, meter reading, heating and cooling systems control, fire and alarm systems, power management and control systems, internet sharing and in-house data communication (Home Plug) [8]. Many service provider stay away from high-voltage transmission lines, however if it is need to go through with this, fiber optic cable is used. The repeater is installed on medium and low voltage power lines to carry the signals over long distance. For this purpose, some companies produce cables with repeaters in it at certain distances. Another handicap is also seen in the step down center [9]. As it is known, high and low voltage electricity is step down at transformer center and then carried to homes and factories. Therefore a data signal on the power line does not pass through the transformer, because the transformer located has inductance, which acts as a filter and blocks the signal to go through. In order to bypass the transformer "Coupler" devices are used to pass the data signal to the next stage [10]. In this study, a DC motor control is achieved via a power line. The study is conducted in accordance with international standards. The system is designed as a transceiver. Microcontroller based transmitter and receiver is performed in this system. In addition, a variable filter circuit operating between 33 khz-140 khz, the coupling circuit, the signal amplification circuit, and the zero crossing detectors are added in to this system. Software for transmitter and receiver are written in CCS C programming language. Obtained results are gathered together in a table /14/$ IEEE PEMC

2 II. SIMULATION OF TRANSMITTER AND RECEIVER MODULES ON ISIS In this study, first of all simulation of the system has been done in PROTEUS and CCS C programming languages. Simulation is done based on the circuit given in Fig.1, which includes two different sections as transmitter and receiver. Transmitter section consists of data production units, coupling circuit to transfer these data from transmitter to receiver. On the other hand, receiver section is designed to receive and control the data sent by the transmitter. ZERO PASS CROSSING PIC 16F877A AMPL. COUPLING POWER LINE POWER LINE COUPLING HIGH PASS FILTER AMPL. PIC 16F877A MOTOR CONTROL Figure 2. System Block Diagram a.) Transmitter circuit b.) Receiver circuit A. Zero crossing detectors Zero crossing detectors are designed to detect signal at zero crossing points. These zero crossing points are then used by the microprocessor to start producing control signals. Zero crossing detectors consist of a capacitor, a diode and several resistances as illustrated in Fig. 3. The main component of zero crossing detectors is the operational amplifier, which requires 12 volts power supply. +12V Figure 1. System circuit diagram used for simulation a.) Transmitter circuit b.) Receiver circuit IN R1 - R3 OUT III. IMPLEMENTATION OF TRANSMISSION AND RECEIVER MODULE ON POWER LINE In this study, a prototype for Power Line Communication based on microcontroller has been developed. Block diagram of the implemented circuit is depicted in Fig. 2. In addition to above explanation of transmitter and receiver circuits; a control circuit, a coupling circuit and a filter circuit are included in to receiver circuit. Data signal received by coupling circuit is sent to microcontroller via high pass filter circuit and signal amplifying circuit. Then microcontroller produces the necessary control signals for the DC motor. R V C1 Figure 3. Zero crossing detection circuits B. Transmitter circuit based on microcontroller Microcontroller uses the data from zero crossing detectors and produces 33 khz high frequency PWM control signals. Block diagram of microcontroller is given in Fig. 4. All operations D1 R4 PEMC

3 implemented by microcontroller can be seen on screen based on CCs programming language. +12V C1 R3 ON/OFF IN ZERO CROSSING IN ,34,35,37 38,39,40 S OUT 220V 33KhZ R1 C2 R2 C3 C4 C5 RV1 RV2 Q1 R4 C6 FILTER OUT PIC 16F 877A 17 33kHz PWM OUT Figure 6. Coupling and filter circuit COUPLING Figure 4. Block diagram of transmitter circuit based on microcontroller C. Amplifying and coupling circuit High frequency controlled signal produced by microprocessor at 33 khz is sent to power line via coupling and amplifying circuits as seen in Fig. 5, which is also used to block harmonics and other unwanted signals in the circuit. The frequency value is calculated in (1). 1 1 f 33kHz 6 2. R. C Signal amplifying circuit includes op-amps, capacitors, resistors, one diode and one potentiometer as seen in Fig. 7. This circuit is used to amplify the control signals produced by the microprocessor. Signal in C6 D1 D2 C7 R5 RV3 R6 +5V + - MC input Vcc Figure 7. Signal amplifying circuit 33KhZ R1 R2 Q1 R3 C1 R4 220V E. Receiver circuit based on microcontroller This circuit controls DC motor by using the signal comes from filter circuit. As seen in Fig. 8, all operations in this circuit is written on the screen based on the software written in CCS C programming language. Q2 CONTROL IN 7 33,34,35,37 38,39,40 S OUT Figure 5. Signal amplifying and coupling circuit D. Receiver, coupling and high pass filter circuit The coupling circuit at the input of receiver consists of a capacitor and resistor connected in parallel and is responsible to collect the data sent by transmitter on the power line as depicted in Fig. 6. Depending on the frequency used in the system, filter impedance is calculated as in (2), using the frequency obtained from (1). X k C 2.. f. C (2) 6 PIC 16F 877A Figure 8. Block diagram of receiver and motor control circuit based on microcontroller IV. SYSTEM OPERATION In this study, two sections have been formed as transmitters and receivers. On the transmitter side, PIC16F877A microcontrollers generate PWM control signals first and then send to the power line via signal amplifying and coupling circuits. Flowchart of the computer program written for transmitter circuit is given in Fig DC MOTOR PEMC

4 START START WRITE STARTUP SCREEN WRITE STARTUP SCREEN PWM PRODUCT INPUT 33 khz? NO SYNC. YES READ ZERO CROSSING PWM & ZERO CROS. SYNC? NO WAIT FOR SYNC. START DC MOTOR YES SEND OF COUPLING Figure 10. Flow chart of receiver program V. EXPERIMENTAL STUDIES PLC system performed based on microcontroller has been tested on the network. A DC motor has been run and stopped using PLC systems successfully. The graphical images prepared in the experimental setup for transmitter is depicted in Fig. 11.a and for receiver and motor control circuit is shown in Fig. 11.b. Figure 9. Flow chart of transmitter program The network receiver circuit detects the signal sent by transmitter on the power line by coupling circuit and then sends it to filter circuit. Later on, filter circuit, an amplifier circuit is used to increase the signal to the appropriate value suitable for the input of PIC 16F877A. After that, microcontroller produces motor control signals depending on the commands sent. All programs for the system have been written in CCS C programming language. Flowchart of the computer program written for receiver circuit is illustrated in Fig. 10 PEMC

5 Figure 11. Experimental setup a) Transmitter circuit b) Receiver and motor control circuits The transmitter circuit of the waveform of PWM signal generated by transmitter is given in Fig. 12 as oscilloscope view. Operation frequency steps are depicted in Table 1. (c) Figure 12. Experimental results a.) 33 khz PWM signal b.) PWM signal coupled to sinusoidal signal c.) Zero crossing signal PEMC

6 TABLE I. RECEIVING DISTANCE DEPENDING ON THE OPERATION FREQUENCY Frequency (khz) Empedans (k) Sensing frequency 0-9 No yes yes yes yes yes No No No No VI. RESULTS In this study, a data transmitting and receiving system has been performed on the power line to control a DC motor. Software for real time application has been written in PROTEUS-ISIS programming language. This system has two units as transmitter and receiver based on microprocessor. On transmitter unit, 33 khz control signal is produced and sent to receiver through a filter and a coupling circuit over the power line. On the receiver unit, the control signal sent over the power line is detected and converted to a suitable signal for DC motor control. These studies have been carried out with great success and proposed as an alternative PLC application. REFERENCES [1] Based Temperature Measurement and Control System Using Power line Engineering, Energy and Electrical Drivers, Turkey, pp , 2013, [2] R. Richard, J. James, "A Pragmatic Approach to Setting Limits to Radiation from Power Line Communication Systems", 3rd International Symposium on Power line Communications and its Applications, Lancaster, UK, [3] Harsha nal Symposium on Power Line Communications and Its Applications, Italy, pp. 16, 2011 [4] Consumer.Vol 44.pp , [D.O.I., / p..268, 2002]. [5] -Line Carrier an National Standards Institute, pp (1992). [6] D. Lauder, Y. Sun, "Modelling and Measurement of Radiated Emission Characteristics of Power Line Communication Systems for Standards Development", Proc. 3rd International Symposium on Power-line Communications and its Applications, Lancaster, UK, [7] orporation, 2008 [8] Australia, February [9] automation system through powe EEE International Symposium on Power Line Communications and Its Applications, Korea, 2008 [10] -Line Communication - Regulation Introduction, Systems Laboratories,2003 [11] Q. Al-Zobik, I.Al-Power-Line Communication System Devices, Vol. 3, pp , 2008 PEMC