The Research On STATCOM Technology Based On Circuit Source Inverter

Reactive power control has been an important issue since the emergence of the ac transmission system, because the most loads consume are reactive power (for example induction motors). The load and load power factor change can cause large amplitude variation in receiving end voltage, which will degrade the performance of the load due to the undervoltage or cause insulation damage to the load due to the overvoltage. So the compensation on proper location is necessary. Traditional reactive power compensation equipment, such as rotary condenser, capacitor, electric reactor, can suffice the demand of compensation, but it has many shortcoming, for example slow response speed and difficult maintenance of accident. So it is difficult for traditional reactive power compensation equipment to meet the demand of modern fast control. STATCOM is a static synchronous generator operated as shunt-connected static var compensator whose capacitive or inductive output current can be controlled independent of the ac system voltage. It has faster dynamic response than the SVC. Presently most of these commercialized STATCOMs are based on the voltage source inverter (VSI). Another potential topology that can be applied to STATCOM is current source inverter (CSI). It can absorb and generate reactive power through the current produced by converter. Compared with the voltage source converter STATCOM, it can control the compensation current and needn't has magnetic Field Coupling with ac system.In this chapter, some work would be done as followed:(1) Derive the mathematical model of the STATCOM on the fundamental frequency model. We want to build the mathematical model that can reflect main character of CSC STATCOM and don't pay attention to some device current at some time. So we use input and output modeling method to built the mathematical model of CSI STATCOM.(2) Design of control for CSI STATCOM. The control is based on the fundamental model of the CSI based STATCOM. There are two control objectives: one is to regulate the dc inductor current; the other is to design a controller to regulate the bus voltage. We decide to use open-loop control strategy or close-loop control strategy according to what CSI STATCOM function. (3) Do some simulation and experimental work on CSI STACOM and Simulation of the dynamics using SimuLink. According to the mathematical model have been built, we can do some simulation and experimental work using MATLAB and SimuLink.In this chapter, The advantage of the CSI topology is the direct control of the current for shunt compensation. No coupling magnetics are needed for this topology. Due to the configuration of semiconductors in series, the conduction loss is relatively high. If better semiconductors are available, this topology can be potentially widely used.