Application of Fixed Frequency Sliding Mode Control for D-STATCOM in Power Systems

D-STATCOM is a Flexible AC Transmission System (FACT) device used to control the reactive power flow in the distribution system. It can be operated in inductive/capacitive operation modes to inject/absorb reactive power. In this paper, a fixed frequency sliding mode control (FFSMC) is designed for the application in a D-STATCOM. To realize the proposed FFSMC, two test cases are performed. In the first case, the voltage sag/swell of the main grid is considered. Meanwhile, in the second case, an unbalanced load condition is considered. The D-STATCOM is situated at the point of common coupling (PCC) to mitigate these issues as well as to improve the voltage stability and power quality. The proposed FFSMC design is based on a constant switching frequency operation and Gao's reaching law is used to eliminate the chattering phenomenon. The stability of the proposed controller is proved as well. The real-time simulation is carried out by using the MATLAB/Simulink environment to examine the performance of the proposed control. Moreover, the simulation results of the proposed FFSMC are compared with conventional proportional-integral (PI) control. The results indicate the advantages of proposed FFSMC in terms of low THD, robustness, and fast-tracking.