Anthesis Journal of Applied and Basic Sciences, 2013, 1(2): 72-77 Copyright © 2013, Available online at www.ajabsci.com Published by Anthesis Journals
Comparison of the Performance of Reactive Power Compensation Structure Parallel to Reduce Voltage Fluctuations on Three-Phase Induction Motor Start up Mehrdad AHMADI KAMARPOSHTI1*, Mohammad SHAKER2 , Toraj TAYEBBIFAR 2 1 2
Department of Electrical Engineering, Jouybar Branch, Islamic Azad University, Jouybar, Iran Department of Electrical Engineering, Rouzbahan University College, Sari, Iran
ABSTRACT: In this paper, solutions to the problem of voltage fluctuations in the distribution system, power companies have to offer. These solutions include parallel reactive compensation laws. In this paper, we review two solutions which are parallel capacitors and SVC. Both solutions are modeled and simulated using PSCAD software. Results obtained by analyzing their performance when subjected to changes on the system are performed and the problems that occur when connecting to the system are compared. Keywords: Power quality, reactive power compensation, SVC, capacitor.
INTRODUCTION Due to its features and power electronics technology to convert electric power from one form having the other is known. Range of power electronics applications in low-power portable devices such as laptop batteries, mobile charger and ... Power levels that are too high to be used in the transmission and distribution systems (Edris, 2002). However, power companies to take advantage of the power electronics are used in the transmission and distribution systems and power electronics are used most often in these cases. Power electronics and their advantages, but it's completely not used to maximum capacity. On (Bradshaw, 2004) is not supported in need of a quick supply voltage source, the power grid of the United States can be dangerous. Low reactive power compensation instruments, especially compensator dynamic reactive power like what occurred on 14 August 2003 in North America and a global blackout came (Bradshaw, 2004). Therefore, this example is particularly relevant to the transmission systems to compensate for the lack of support instruments or effects of reactive power can be put on the distribution system. Instruments to offset the shortage of reactive power on the transmission that occurs when the supply of large units such as industrial motors, large air conditioning units, water pumps, engines and ... Circuits are connected to the distribution system (Hsu, 1999). Sometimes, in a day, an engine with high power and heavy industry sectors on a distribution circuit will be launched. Attack of the motor voltage fluctuation, local consumer and industrial factory buildings on the distribution lines are connected to it, that is. Surge voltage, a disadvantage for the use of local disturbances, but also cause more landslides engine is based on the low voltage level of the power plant is made. Resulting in production losses, any unplanned action plan may be off. Fluctuations in voltage that occurs when a heavy load, such as the air conditioning system is a great time to enter the circuit. So there is a heavy industrial motor and a lack of instruments to compensate reactive power, what effects will be on the distribution system, and these cases are presented here. Furthermore, two methods for reducing the effect of large induction motors that operate on a small part of an electrical distribution system at startup occurs, is used. First, a common industrial method in which the capacitors are used in parallel. While the second method, a method was developed that uses power electronics. In the conventional method, the reactive power compensator using the constant capacitance, to reduce the impact on the power system is used to start the engine. However, advanced techniques, control electronics, power Received: 29 July 2013; Accepted: 27 August 2013 Corresponding author: Mehrdad Ahmadi KAMARPOSHTI (
[email protected])
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systems have been replaced, failed to reduce the amount of voltage that occurs during engine startup. Here, the advantages and disadvantages of using power electronic voltage fluctuation problems, is presented. For modeling and simulation of power systems and power electronic controllers and parallel capacitance effects of software called Power Systems Computers Aided Design or PSCAD is called for short, is used. The basic model of the power system, once the engine has a heavy load, is developed. Hence, the parallel capacitor equipment and tools and then SVC, was set up. An empirical study, including transient response, time settings, and is stable for both methods will be presented. METHODS OF REACTIVE POWER COMPENSATION Parallel capacitor, reactive power in power system is a typical supplier. Capacitor in parallel with its reactive power, improve power factor source to the load will be. This will reduce losses and reduce the voltage drop and allow for more real power transfer on the line. The end result is that the efficiency and voltage regulation can be improved (Glover and Mulukutla, 2002). Static Var power compensator (SVC), another type of compensator is parallel. Thyristor The compensator of the key reactions in parallel with the capacitor is used. Thyristors are arranged in a position that allows flow in both directions, to find the flow. This way, shape or constant power factor correction and reactive power changes, is right. Reactive power during light load and a heavy load during use, it is absorbed. Automatic control system with SVC with the supply or consume reactive power Thyristor switches, can be specified. So therefore, it reduces the voltage fluctuations and increases the flexibility of the side bar. Figure one shows the SVC system. TCR, permanent and continuous reactive power is displayed on the system and changing the flow through the reactor, the operation will perform equalization. Furthermore, TSC, capacitor banks to on or off, depending on the amount of compensation required to be attached to. Also AFC (current filter AC), harmonics are generated by the TCR will absorb and filter (Toshiba, 2001). Figure 1 below shows the SVC system is a sort of arrangement.
Fig.1: A sort of arrangement SVC system
MODELS OF DISTRIBUTED SYSTEMS To analyze the performance of reactive power compensation using PSCAD software model of the power system simulation have been developed and expanded. In Figure 2, a compensator system into an electric car and a radial network is shown.
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Ahmadi Kamarposhti et.al, 2013; Comparison of the Performance of Reactive Power Compensation Structure Parallel to Reduce Voltage Fluctuations on Three-Phase Induction Motor Start up
THE SIMULATION RESULTS Simulation Results without the Use of a Capacitor and with Using Capacitance Figure 3, the motor current, voltage, time, and displays the current time. Here we consider only the first 5 seconds, the input voltage and current levels due to the invasiveness of the motor show. With a nominal voltage of 120 volt line voltage 4 V voltages drop several times that period, after the engine has run. Initially, the slope of the first menstrual period, 111.5 volts. This is when the engine will start. Observed at ground voltage, single phase, and assuming on the three-phase oscillations occur for the duration of 2.5 seconds, the voltage from 120 volts to be diverted. The current setup has a high value and is about 1050 amps. Done so consistently for 5 to 8 times the amount of current drawn by the motor is to be expected. Also during the time, 0.5 amps will change when the engine reaches its nominal speed range is 15 amps. Figure 4, a parallel system in which the capacitor has been added to show. Capacitor in parallel with the 0.2 MVAR reactive powers per phase is selected. Because of this, the voltage drop for any period of time, the engine will start, is correct. Causing voltage problems over the engine speed is reached.
Figure 2: A basic model of distributed power system
Fig. 3: (a) Motor current, (b) load voltage and (c) current load
At first it seemed that this method is an acceptable method. But after further studies, it was found that this method is the best method. Because when there is no compensator, capacitors should be on line and should not be left connected. As this may result in over-compensation circuit is that it can be acceptable and not acceptable. Figure 5, the voltage and current waveforms show that the parallel capacitor. Now voltage is 2.75 volts. This value is significantly lower than that in the linear
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voltage drop compensator is used. Once this plan is better than the linear motor startup is no compensator is. The oscillation is shown for a short period of time. For more than 2 seconds, still below the voltage range is 120 V nominal. The Compared with values calculated from the voltage drop to 1.79 volts. Figure 2 below shows the basic model of the power distribution system. In Figure 3, the armature current waveform, voltage, time and current time in the base model of the power distribution system is seen. Figure 4, which is the case of parallel capacitors in the power distribution system model, is used.
Fig. 4: Model of power distribution systems using parallel capacitors
In Figure 5, the waveform of the motor current, voltage, time and current time in the power distribution system model in which the capacitors are used in parallel.
Fig. 5: (a) Motor current, (b) load voltage and (c) current load
Simulation Results Using SVC Figure 6 shows a model of the distribution system in which the SVC is used. Using this method, it is clear that the voltage is zero volts. This value is significantly less than the value at which the compensator is not used and a system that is less than that of the parallel capacitor is used. SVC, designed to keep the motor current at 215 mA. SVC system where no voltage drop in the load model shown, not manufactured. The three models described before, under extreme circumstances, that will change the engine load torque, have been tested. Simulations results again show that the performance of the SVC pressure during engine run great, wonderful. SVC system is only a very slight increase from 120 V nominal input voltages when the engine is at its lowest point is over. In all three scenarios, and simulation of the model turns out to be superior to SVC system. 75
Ahmadi Kamarposhti et.al, 2013; Comparison of the Performance of Reactive Power Compensation Structure Parallel to Reduce Voltage Fluctuations on Three-Phase Induction Motor Start up
The advantage is that the continued and permanent SVC system with power electronics, control is achieved. Several times a day when the engine load is connected or disconnected, parallel capacitance method is appropriate. Because the motor characteristics and the effects it is easily predictable. Also a mechanical key to reducing voltage fluctuations can be determined.
Fig. 6: Model for Distribution System Using SVC
Figure 7, the voltage and current waveforms using SVC flow system attacks the motor show.
Fig. 7: (a) Motor current, (b) load voltage and (c) the current load on the system with SVC
CONCLUSION In this paper, the performance of the two methods of reactive power compensation in power systems development has explained today. Reactive power compensation instrument for awareness and understanding of the voltage fluctuation results in heavy attack from an electric motor, are used. This model includes the equalization model using PSCAD software modeling and simulation has been. The solution uses a parallel capacitor, the voltage quality residential load, just a simple electric motor, has improved. Hence, the voltage swing for several terms and was not yet known and the unexpected volatility observed over time. Modeling of power system with SVC with better results can be explained. Power system gradually over time, is more complicated. Modeling and
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simulation of power systems using software PSCAD, as was shown in the paper, the performance of the power system would be very useful. REFERENCES Bradshaw D T. 2004. It’s Time to Address the Critical Issue of VAR Compensation, Transmission and Distribution World, PRIMEDIA, Inc., April 1. Edris A. 2002. Power Electronic-Based Controllers at Technological Crossroad, EPRI Journal Online. Palo Alto, August 21. Glover J D and Mulukutla S S. 2002. Power System Analysis and Design, 3rd ed., Brooks/Cole, Hsu S. 1999.Using a Static VAR Compensator to Balance a Distribution System, IEEE Transactions on Industry Applications, Vol. 35, No.5. Toshiba Corporation and Toshiba International Corp. 2001. SVC Operation Principles, Sydney. Short CV of Authors Mehrdad Ahmadi Kamarposhti received his B.Sc. in power electrical engineering from Babol Noshirvani University of Technology, Iran, in 2006. In 2008, he received his M.Sc. in electrical engineering from Faculty of Electrical Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran. He is currently a Ph.D. candidate in power electrical engineering from Faculty of Electrical Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran. His fields of interests include reactive power, power operation, voltage stability and reliability.
[email protected]
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