Voltage Stability Control For Direct Drive Wind Power System With STATCOM

With the proportion of wind power growing year on year in the power system, theimpact of large-scale wind farm is on the grid growing. Therefore, the study of voltagecontrol and reactive power characteristics when a large-scale wind farms is connectedto the grid, is one the technical problems in China’s wind power that need to solveurgently. A simulation model of "direct-drive wind farm-infinite system" is establishedin this paper, and the study is focused on the action of voltage and reactive powercontrol when the direct-drive wind farms and it includes static synchronouscompensator (STATCOM). Then the smart algorithm is used to tune and optimizeSTATCOM controller parameter. The main contents include:The simulation model of direct-drive permanent magnet synchronous generatorand wind turbine model are established by using MATLAB/Simulink software. Themaximum tracking control that the main way is to track the optimum speed ratio wasapplied in wind turbine generator-side. After studied the simulation model, the resultsshow that the speed of wind turbines can be controlled at optimum speed ratio undervarious wind conditions, so that capture the best wind energy coefficient. Based on theabove model,102MW direct drive wind turbine is made to be equivalent to a20MWgenerator by using a wind farm equivalent method. Equivalent wind turbine grid-sideemploys a constant voltage control method, and this control strategy is simulated andanalyzed. The simulation results show that the strategy proves to be effective fortransient stability control, suppress voltage fluctuations, etc.Reactive compensation devices, such as STATCOM, were considered to beconnect the grid to control reactive power and voltage when lack of wind farm reactivepower, etc. The traditional PI controller was replaced by the fractionalPI controllerto control STATCOM. It is very uncertain and difficult to tune fractional controllerparameter that the Chaos Particle Swarm Optimization algorithm (CPSO) are appliedto tune controller parameter. The results showed that fractional orderPI controllercan effectively improve the control performance, and the robustness of the system.Finally, the simulation model of "wind farm-the infinite system with STATCOM"is built based on the previous operation. The steady-state and transient voltage stabilitymodel were simulated under different active and reactive load situations. The resultsshow that wind farms need a lot of reactive power to maintain a constant voltage at lowgrid voltage, and can reduce reactive power output of wind farms after STATCOM is accessed, and improve the power system static and transient voltage stability.