24-04-2012, 02:34 PM
MITIGATION OF VOLTAGE SAGS/SWELLS USING DYNAMIC VOLTAGE RESTORER (DVR)
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INTRODUCTION
Power quality phenomena or power quality disturbance can be defined as the deviation of the voltage and the current from its ideal waveform voltage and the current its ideal waveform. [1].
Voltage sags last until network faults are cleared and typically range from a few milliseconds to several seconds [3]. Voltage swell, on the other hand, is defined as a swell is defined as an increase in rms voltage or current at the power frequency for durations from 0.5 cycles to 1 min. typical magnitudes are between 1.1 and 1.8 up. Swell magnitude is also is also described by its remaining voltage, in this case, always greater than 1.0. [2].
POWER CIRCUIT OF DYNAMIC VOLTAGERESTORER
The DVR is a custom power device that is connected in series with the distribution system as shown in figure 1. The main components of the DVR consists of
an injection transformer, harmonic filter, series VSI (VSC) , an energy storage and control system (as shown in Figure-1).
The basic function of the DVR is to inject a dynamically controlled voltage VDVR generated by a forced commutated converter in series to the bus voltage by means of a booster transformer. The momentary amplitudes of the three injected phase voltages are controlled such as to eliminate any detrimental effects of a bus fault to the load voltage VL. This means that any differential voltages caused by transient disturbances in the ac feeder will be compensated by an equivalent voltage generated by the converter and injected on the medium voltage level through the booster transformer.
SIMULATION RESULTS AND DISCUSSIONS
A detailed simulation of the DVR control system was performing using MATLAB/SIMULINK program in order to verify the operation. The parameters of the DVR system are as follows (Table-1):
CONCLUSIONS
The modeling and simulation of a DVR using MATLAB/SIMULINK has been presented. A control system based on dqo technique which is a scaled error of the between source side of the DVR and its reference for sags/swell correction has been presented. The simulation shows that the DVR performance is satisfactory in mitigating voltage sags/swells.