Research On The Series-Parallel Comprehensive Compensation Device For Wind Turbines

Promoted by China's surging economy, the demand for energy is increasing these days. Wind power is a clean and pollution-free new energy. It is of great significance to develop wind power for energy conservation and low-carbon economy. For the power quality and safe operation of power system's point of view, requirements were made for wind turbines manufacturers. On the one hand, Most of variable speed constant frequency wind turbines use grid-connected inverter, which results in low harmonic current increase and severe output power quality deterioration of the power system. On the other hand, the voltage drop of grid connection caused by the grid failure may leads to wind turbines to take off the gird. It brings a great challenge to the stability of power system, the research on the low voltage ride through of the wind turbines has important theoretical and practical significance. Combined with Active power filter and Dynamic voltage restorer, this paper proposed a series-parallel comprehensive compensator to realize the grid harmonic current compensation and low voltage ride through for wind turbines. The work of this paper can be listed as follows:(1) Based on the requirement of harmonic current compensation and low voltage ride through for wind turbines, this paper proposed a series-parallel comprehensive compensator. This compensator is designed to be a comprehensive compensation device integrated with active power filter and dynamic voltage restorer. The topological structure and the working principle of the device were introduced, and the working principle for different compensation mode of the device was analyzed in this paper.(2) For the study of Active power filter, this paper analyzed from three different aspects:harmonic current detection, compensation current tracking control and DC voltage control. The working principle of the novel ip-iq harmonics detection, the adaptive-hysteresis current controller and the DC voltage PI regulation were presented respectively. The model of Active Power Filter using this new control method was built on the MATLAB. The simulation results verified the validity of this control method.(3) For the study of low voltage ride through for wind turbines, series coupled Dynamic voltage restorer was used to assist the wind generator to realize the LVRT in this paper. The control method was designed for this topological structure of Dynamic voltage restorer. Based on different power grid failure situations, the model of three phase series coupled dynamic voltage restorer control system was built on PSCAD The simulation results verified the validity of this method.(4) In order to verify the control strategy designed for the shunt active filter, an experimental platform of three-phase three-wire parallel APF system was built. The hardware system which are components of the platform were detailed introduced in this paper. The experimental results verified the advantages of the convergence speed and steady state performance of the control method.