Study On Analyse And Control Strategy Of STATCOM In Power Distribution Systems

With the improvement of automation industry, the power customers are more and more particular about the power supply quality and dependability. At present, the power system lacks var compensation, and the reactive load, especially the impulsive reactive load, which not only increases power loss, but also seriously deteriorates the power quality of customers'. In order to improve power quality and reduce costs of power system, it is meaningful to use immediate reactive power compensation. With wider operation range and faster response time, the Static Synchronous Compensator (STATCOM) possesses better performance than other reactive compensate devices used before. But most of the studies and applications about STATCOM deal with high voltage transmit network with large capability. This paper aims at STATCOM in low-voltage power distribution systems (D-STATCOM). The main works are as follows:At first, the development of reactive power compensation technology and the application of STATCOM at home and abroad were introduced. Then a three-phase voltage source inverter was chosen as the main circuit of D-STATCOM to meet the requirement of the task. Based on the theory of dq reference frame transformation the dynamic mathematical model of D-STATCOM in dq reference frame was deduced by introducing switch function. A few kinds of control strategy for both device-level and element-level were analyzed and compared, which is the keystone of this paper. Based on time-varying characteristic of D-STATCOM's equivalent resistance, a simple no resistance feedback control strategy was proposed at device-level control strategy. The result of simulations shows the steady-state performance of simple no resistance feedback control strategy is superior to that of Differential Geometry control strategy, and its decoupling performance is superior to that of Inverse System control strategy. In accordance with the requirements of full use of DC side voltage and facility, space vector PWM was chosen as the element -level control strategy. And then the stability of the chosen control system was discussed by using small signal perturbation...