Control of a Dynamic Voltage Restorer to compensate single phase voltage sags

University essay from KTH/Elektriska energisystem

Author: Mampe Vithanage Kasuni Perera; [2007]

Keywords: ;

Abstract:

Quality of the output power delivered from the utilities has become a major concern of the modern industries for the last decade. These power quality associated problems are voltage sag, surge, flicker, voltage imbalance, interruptions and harmonic problems. These power quality issues may cause problems to the industries ranging from malfunctioning of equipments to complete plant shut downs. Those power quality problems affect the microprocessor based loads, process equipments, sensitive electric components which are highly sensitive to voltage level fluctuations.

It has been identified that power quality can be degraded both due to utility side abnormalities as well as the customer side abnormalities. To overcome the problems caused by customer side abnormalities so called custom power devices are connected closer to the load end.

One such reliable customer power device used to address the voltage sag, swell problem is the Dynamic Voltage Restorer (DVR). It is a series connected custom power device, which is considered to be a cost effective alternative when compared with other commercially available voltage sag compensation devices.

The main function of the DVR is to monitor the load voltage waveform constantly and if any sag or surge occurs, the balance (or excess) voltage is injected to (or absorbed from) the load voltage. To achieve the above functionality a reference voltage waveform has to be created which is similar in magnitude and phase angle to that of the supply voltage. Thereby during any abnormality of the voltage waveform it can be detected by comparing the reference and the actual voltage waveforms.

A new control technique to detect and compensate for the single phase voltage sags is designed in this project. The simulation was checked in the EMTDC/PSCAD simulation software and has shown reliable results.

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