Equivalent Model And Reactive Power Compensation For Offshore Wind Farm On PSCAD/EMTDC

Development and utilization of wind power and other renewable energy have got more and more attention from each country. With the gradual saturation of onshore wind resource development, offshore wind power has become the focus of the future use and development of wind energy. The immature offshore wind power technology restricts the large-scale development of offshore wind power greatly. Therefore, carrying out a comprehensive study of offshore wind farm is very urgent and significant.In this thesis, the composition of offshore wind farm is illustrated, including the wind turbines, the collection systems, the offshore booster substation and the electric power transmission. The wind turbines improve the wind utilization efficiency by capturing the maximum wind energy with variable speed constant frequency Double-Fed Induction Generator. In order to achieve the lower cost, the appropriate voltage levels, cable types and arrangement of wind turbines are chosen in the collection system. With the offshore booster substation, the electric power pooled by the collection system is integrated to the HVAC(High Voltage Alternative Current) power system.The complete model of offshore wind farm with high number of wind turbines, including the modeling of all the wind turbines and the internal electrical network, presents high-order and costs long computation time when simulation. The paralleled transformation method for the internal radial collector network of wind farm is applied in this paper, which can make any two wind turbines in parallel and then make it possible to aggregate the wind turbines in any positions according to the wind situation. The semi-aggregated equivalent model not only reduces the model order and computation time, but also ensures the accuracy of the equivalent model. SVC(Static Var Compensator) is applied in the internal branch of offshore wind farm to absorb the reactive power. Thus, the offshore wind farm can export the maximum active power, resulting in the improved economic benefit. STATCOM(Static Synchronous Compensator) is implemented at PCC(Point of Common Coupling) to compensate the reactive power under fault conditions. The proper reactive power generated by STATCOM can reduce the voltage fluctuation caused by faults. The stability of the offshore wind farm system is improved with SVC and STATCOM. Simulated systems are developed in PSCAD/EMTDC(Power Systems Computer Aided Design). Simulation results show that the equivalent model can represent the collective response of the offshore wind farm well, and the SVC and STATCOM can compensate the reactive power effectively.