The Study And Design Of Double PWM Convertor For Double Fed Induction Wind Generator

Variable speed constant frequency (VSCF) for double fed induction wind generator (DFIG) is a high efficiency and low cost generate electricity technology recently. It has a great application prospect in the area of wind power generation. Double PWM convertor which supplies the ac excitation for rotor of double fed induction wind generator is becoming a very important part of VSCF technology.First, the operation principle of DFIG has been discussed in this paper. The math model has been build. It also analyses the steady equivalent circuit and the power flow relation of DFIG. On basis of this, it establishes the vector control strategy based on the stator flux oriented for rotor-side convertor and the vector control strategy based on the grid voltage oriented for grid-side convertor.And then,it designs the hardware and software of double PWM convertor. The hardware circuit consists such as the main circuit which composed by input filter inductor, intelligent power model and DC-side filter capacitance, the control circuit using DSP as the core control chip, the serial communications interface between PC and DSP, detective circuit driver circuit for IPM, switching power supply circuit, protection circuit et al. The software compiles the control procedure by using C language in CCS3.3. It illustrates the whole program flow and some important subprogram flows for double PWM convertor.At last, it establishes the simulation model of the vector control strategy for rotor-side convertor and grid-side convertor. There are two kind of conditions in rotor-side convertor,one is after connecting the grid,the other is grid connection process. In the condition of after connecting the grid, rotor speed changing from low to high has been simulated. Double PWM convertor could alter the amplitude,frequency and phase of rotor current output to make VSCF. In the condition of grid connection process, stator voltage has been simulated to satisfy the request for connecting the grid which means to make the same as grid voltage in amplitude, frequency and phase. The simulation results validates that the vector control strategy for double PWM convertor is correct. It shows that the control strategy has certain practical application worth.