The Research On HVDC-Flexible Used In Wind Farm Grid Connection

As energy and environment problem is increasingly severe, the development of new renewable energy is a necessary way to realize the sustainable development of human society. Wind power is the most development potential renewable energy, since last century till now, it has been the focus of scholars'research both at home and abroad. Along with wind power energy is getting mature, more and more offshore wind power grid connection engineering applications have been implemented, the exploit area of wind power has been changed from land to sea. However, due to offshore wind power has the characteristic of long distance, output random etc. HVDC-Flexible adopting controllable shut-off power electronic devices and PWM (Pulse Width Modulation) technology, which can realize the active power and reactive power independent control, and do not need to communicate with each station. Thus, in the new energy sources such as wind power and solar power grid connection, it has very good application prospect. This paper researches on HVDC-Flexible technology used for offshore wind farms grid connection, the main content include:(1) The operation principal of the doubly-fed wind power generator, which contains maximum wind power capture, mathematical model, control strategy based on the stator flux vector and so on. The simulation model has been established in MATLAB/SIMULINK to research the output characteristics of DFIG under different wind conditions.(2) Introduces the basic principle of HVDC-Flexible and its topology structure, establishes it's mathematical model, a vector control strategy based on inner control loop and outer control loop has been proposed. And controllers for dc voltage, active power, reactive power, active voltage, frequency control have been designed, it has also analyzed the inner loop control loop d-q axis current decoupling control method.(3) HVDC-Flexible and offshore wind power grid connection coordinated control strategy has been studied. For wind farm output characteristics, proposes a control strategy of active power and alternating voltage control in send end station, dc voltage and reactive power control in receive end station. And the control scheme of both ends have been designed. A simulation model has been established in MATLAB/SIMULINK, researches dynamic response characteristic of the system, the simulation results show the system has good performance in improving the output of wind farms, maintain the voltage stability, enhance the system anti-jamming, and fault recovery...