Research On The Coordinated Control Strategy For Voltage And Reactive Power Of DFIG-Based Wind Farm

With rising concerns on the environmental pollution and fossil energy shortage, there has been a rapid increase in renewable energy sources in the past decade.Among various renewable energy sources, wind power is the most rapidly growing one. As one of the most important types of wind generators,doubly fed induction generators (DFIG) are widely used for their flexibility in active/reactive power control and low cost.With the increase of wind power penetration, the integration of wind farm into grids introduces a set of serious challenges, in which the reactive power and voltage control become more significant. Reactive power control of doubly fed induction generators has been a heated topic in stability control of power systems in recent years. Nowadays, power systems use FACTS devices for the control of real and reactive power in the system. The shunt FACTS devices such as Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM) have been used in most wind farms to provide rapid and smooth reactive compensation and voltage control. The coordinated control of these FACTS devices with the generator is essential for the control of voltage at the Point of Common Coupling (PCC). Therefore, reactive power coordinated control strategy for wind farm with doubly-fed wind turbines and STATCOM is studied. The objective is to find the settings of these reactive power sources in order to take advantage of each DFIG’s reactive power generating ability and improve the reactive power margin of STATCOM, improve the stability of the voltage at the PCC.Firstly, the reactive power generation ability and control method of wind turbine with DFIG, is analyzed in detail. Secondly, the operation principle of STATCOM, which has a wide adjusting range to compensate the reactive power rapidly, is introduced. Thirdly, the voltage sensitivity of the double fed induction generator and the static synchronous generator is analyzed, and the reactive power margin index is defined. On this basis, the objective function is set up and the coordinated control strategy among DFIGs and STATCOM is proposed. Finally, a grid-connected wind farm model is built in MATLAB/SIMULINK and the proposed strategy is simulated, and results show the effectiveness of the control strategy proposed.