Application Of Voltage Source Converter Based HVDC To Grid Integration Of Wind Farm

Voltage Source Converter based HVDC(VSC-HVDC) enjoyes broad prospective application in power systems. This paper focuses on VSC-HVDC application to wind farm grid integration. The main contents of the thesis cover the following:1. The steady-state and transient models of induction-generator(IG) based fixed-speed wind turbine (FSWT) are described. Its steady-state and transient voltage stability are analyzed and verified by simulation.2. VSC-HVDC steady-state and transient models are established. VSC-HVDC steady-state control strategies and control system used in wind farm integration are designed and set up in the integrated power system simulation program DIgSILENT/Power Factory in this paper. Feedforward decoupling control used to fulfill the active and reactive power decoupling control is verified by simulation. The protection strategy of shunt resistor plus VSC blocking during large disturbance is performed to protect the VSC is carried out. The short circuit current contribution of the wind farm integration based VSC-HVDC is analyzed.3. The voltage instability mechanism of wind farms consisting of FSWT is investigated. The steady-state and transient voltage stability improved by VSC-HVDC are analyzed and verified by simulation.4. For a wind farm integrated into power system via VSC-HVDC, the inertia of induction generator and its impacts on frequency stability is always a concern. The additional frequency control loop is established for VSC-HVDC, by which wind farm can improve the grid frequency stability. The simulation results show that the additional frequency control loop can adjust the active power of wind farm according to frequency fluctuation of the power system, so it can reduces frequency deviation.