Research On The Control Strategy Of Chain STATCOM

With the rapid development of modern industry, the power quality demand is higher and higher, the existence of the reactive power in the power system load increases the system loss, affect the power quality. So we need to adopt reactive compensation technology to improve the quality of power grid electricity. Because static reactive power compensator(STATCOM) with other compensation device incomparable advantages, so it become the main research direction.This article use the cascaded H bridge multilevel inverter constitute the main circuit of STATCOM, analyzes the working principle of the chain of STATCOM. Combined with carrier phase vertical(CPD-SPWM) modulation technology, with low switching frequency to obtain high equivalent switching frequency, so as to reducing the harmonic content of output current.This paper firstly introduces the development background of STATCOM in the field of reactive power compensation, then analyzes its working principle and establish the mathematical model, and analyze the system stability. Modulation methods using single frequency doubling carrier phase-vertical CPD-SPWM modulation method, the simulation results show the feasibility of main circuit structure.In the aspect of current detection, this paper introduces the reactive current based on the p-q and ip-iq operation mode real-time detection technology, this paper select current detection method based on instantaneous reactive power theory.The direct control of the STATCOM method and indirect control method are introduced, by analyzing the working principle, compare both advantages and disadvantages, this article choose direct current control method.On the analysis of the capacitor voltage unbalance factor, thought of the balance control and the research of DC capacitor voltage to make sure the system is reliable and continuous, using the balance control to realize voltage low voltage high voltage based on the pursuit of ideas,and it has made the simulation in MATLAB/simulink environment.Finally, using the MATLAB simulation software to build the whole simulation model of STATCOM, the simulation results indicate that the system has good compensation effect and the system response has a foster speed.