Application And Research On Control Strategies Of Voltage Source Converter

Insulated-Gate Bipolar Transistor (IGBT) which combines advantages of GTR and MOSFET is becoming the dominant switching component composing power electronic devices of small and medium-sized power gradually, so voltage source converter (VSC) based on IGBT is being applied in different fields widely. Especially, in order to coordinate effective implementation of chinese the twelfth five-year plan for development and utilization of new energy resources, people speed up the research on application of VSC in new energy resources distributed generation systems. The main researching work on application of VSC in grid-connected photovoltaic(PV) generation system, single-phase inverter system and VSC-MTDC(multi-terminal direct current based on VSC) transmission system is shown as follows:Firstly, according to the mathematical model of PV array, a control model component of PV array is compiled in electromagnetic transient simulation software PSCAD/EMTDC, whose output signal is used to trigger a constant current source, so a electrical model component of PV array can be simulated by this method. This method provides a feasibility base for simulation research on grid-connected PV generation system. On this basis, the mathematical model of three-phase grid-connected PV inverter in the three-phase stationary abc reference frame, the two-phase stationaryαβreference frame and the two-phase synchronous rotating dq reference frame is derived respectively, then a corresponding feedforward decoupling control method with independent active power and reactive power control is introduced. And both a three-phase single-stage grid-connected PV generation system and a two-stage grid-connected PV generation system are simulated in pscad/emtdc.Secondly, a fuzzy self-tuning PI control is introduced into grid-connected PV generation system on the base of previous research, which will effectively improve the grid current waveform.Thirdly, this paper puts forward a new compound control algorithm which combines advantages of discrete repetitive control and zero-phase-error adaptive control algorithm, and improves dynamic and static characteristics of the control system. According to the mathematical model of single-phase inverter system, zero-phase-error adaptive control algorithm is derived, and the proposed compound control algorithm is applied in the single-phase inverter system which is simulated using PSCAD / EMTDC and MATLAB / SIMULINK interface.Finally, in order to reduce construction cost of VSC-MTDC, this paper presents a virtual grid flux-linkage oriented vector control algorithm. The algorithm replaces the traditional power grid voltage oriented vector control, and eliminates the voltage sensors needed by each converter station control, so it can reduce the cost of large-scale multi-terminal DC transmission system.