Design Of Back To Back Pwm Converters For Double-fed Wind Power System

As today's shortage of energy and pollution of environment is very serious, it is meaningful to exploit renewable and clean wind energy. Countries all over the world have been competing to develop the technology of this field. Among all these technologies, variable speed fixed frequency double-fed wind power system is the most widely used. Based on this system, the back to back PWM converters could enable maximum energy capture from the wind.Compared with traditional converters, back to back PWM converters as the core part of the variable speed fixed frequency power generation system has better input, output, low harmonic wave and wide speed regulation range characteristics. The rotor side converter is responsible for the vector control of double-fed machine to capture the maximum wind power based on the given speed and interdentally coordinate the reactive power. Grid side converter is responsible for power exchange between rotor side converter and grid side.This paper firstly analyses several aspects including the speed control theory of double-fed machine and its math model, maximum wind power capture based on given active and reactive and some vector control schemes. A few regulation rules such as power regulation, torque regulation, speed regulation are compared, moreover based on which a control scheme about independent control of active power and reactive power is established. Meanwhile, a new idea that using the DTC (Direct Torque Control) in the variable speed wind energy generation is put forward, which is more directly to control the double-fed machine and improve the whole system. Then also through the analysis of math model of three phase PWM converter in d-q reference, double closed loop PI control system about stabilization of DC voltage and unit power factor operation could be established. Under the Matlab/Simulink software surrounding, simulation is made to testify the researched theory, which shows the design of the grid side converter and rotor side converter is applied to variable speed wind-energy generation.At last, this paper introduces the dSPACE real time development system used in wind power test platform, including the software and hardware configuration. Through the equipment of dSPACE, the control scheme about the grid side converter and the rotor side converter could be convenient to be embedded into the experiment platform to testify the feasibility of the design, which is beneficial for the progress of the research about variable speed wind energy generation.