D-STATCOM Modet for Restoration of Distribution System Stability

Abstract

Due to complexity of electrical power system netvvork, the assurance of uninterrupted supply of electrici,ty and quality power has become the main challenge for the diiiribution system. The fluctuation of system voltage, frequency as well as real and reactive power hampers the system stability which jeopardizes uninterrupted supply of electricity to the consumers. Utility distribution netvvorks, sensitivity industrial loads and critical commercial operations suffer from various types of outages and service interruptions which can cost significant financial losses. The voltage sag and swell are the most important power quality problems which are seen in industrial and commercial installations. For improving power quality at the distribution network, various FACTS (/texible AC transmission system) deyices like D-STATCOM (dynamic static synchronous compensator), DI/R (dynamtc voltage restorer), SVC (static YAR compensator) and others are used. The D-STATCOM (distribution static compensator) is now replacing other FACTS devices in the distribution system for its better performance than others. The D-STATCOM has the capability of instantaneous system voltage improvement in case of voltage sag andflicker within the distribution system. The design of the control system is the main aspect of the D-STATCOM. In this paper, a 6 pulse D-STATCOM model is designed and simulated by using PSCAD/EMTDC for improving of distribution system stability by mitigation of uoltage dips. The PI controller is used for controlling the voltage and reactive power flow to and from the DC capacitor of the D-STATCOM. The PLL (phase locked loop) is usedfor controlling the gate triggering pulses ofIGBT based VSC (voltage source converter) of the D-STATCOM by using PWM (pulse width modulation)