Study On Direct Power Control For Hybrid Rotor Open Winding Brushless Doubly-fed Wind Power Generator

Wind energy which is clean and renewable is widespread concerned by researchers in order to solve the problems, such as the worsening weather of haze, and the emergency supply of fossil energy. There are also difficult problems that the current generators need maintenance frequently which cost a lot and a high capacity inverter is necessary. In this paper, a direct power control (DPC) method applies to a new type machine, which is called hybrid rotor open windings brushless doubly-fed wind power generator(BDFG) is proposed to solve these problems.First, the new BDFG with a special stator structure and rotor structure, the rotor can perform magnetic field modulation effect make BDFG work steady. The working principle and power flow in different work methods are analyzed. The mathematical model in the rotating coordinate system for BDFG is proposed for power control. Equivalent circuit of BDFG is also shown in this paper.Secondly, an improve DPC method is proposed according to the special structure of BDFG. The DPC can make quickly power response without complex coordinate transformation calculation or the effect of parameter changing. A method to make the output voltage of BDFG stable is proposed to ensure the BDFG connect to the grid successfully.Thirdly, the voltage vectors of open winding are analyzed, it has three different amplitudes vectors, are called long vector, middle vector and short vector. Using different kinds of vectors to build DPC method and making a simulation in Matlab/Simulink program. Then find their advantage by compare the power waves and current waves. In order to improve the control effect, the mix vector DPC and power error compare DPC have been studied. The active power and reactive power can be controlled independently by this two way, furthermore, the power also perform stably in variable speed situation. When the reference power is changing, the practical power can closely follow the changing. The mix vector DPC and power error compare DPC also have a current with low THD, which is good for grid connect.At last, the experimental platform of hybrid rotor open winding BDFG DPC system has been set up with TMS320F28335DSP. Signal conditioning circuit, current sampling circuit, IGBT drivers have been designed. PWM and QEP are programmed in C language. Two inverters and prototype have been made for the experiment. The experiment results verify that the open winding control method of BDFG is feasibility.