Research Of DPC Technology In DFIG

It is a focus of attention of energy industry for improving energy structure in our country, utilization of renewable energy, reducing environmental pollution and improving power quality. Wind power is one of new and renewable resources that has most favorable development prospect and technologies are most advanced at present time. With development of exploitation and utilization of wind energy, wind energy technology also have marked progress, and become an embranchment of technology.Doubly-fed VSCF wind power technology is a new type of highly efficient technology, when wind speed changes, rotor side access frequency, amplitude, phase-controlled low-frequency excitation current, can guarantee double-fed generator of constant output frequency, VSCF implementation. As a result of research by many scholars and engineers, vector control technology is now widely used, vector control technology has complex coordinate transformation, is very complex to control. For the shortcomings of Vector control technology, direct power control strategy is proposed by a Japanese scholar, which is robustness to parameters, has simple structure, and a high power factor, is high dynamic to follow, in recent years has been rapid development.This paper analyzes and establish mathematical model of doubly-fed induction generator ,described detail characteristics of doubly-fed induction generator, and study the application of direct power control strategy in the field of doubly-fed induction generator, through power hysteretic comparator to track reference value to control generator's output. DPC is simulated by MATLAB/Simulink in wind DFIG, simulation results show that direct power control strategy has simple structure, a high power factor, achieve independent regulator of active power and reactive power, has good dynamic performance, and no overshoot.Switching frequency is not constant in Direct power control strategy traditionally, it causes problems for filters design, to compensate shortcomings caused by the use of DPC, we adopted space vector modulation technique to control output of rotor voltage with constant switching frequency, can control ac excitation of rotor. Simulation results show that direct power control strategy with a fixed switching frequency simplifies system structure, improving system static and dynamic performance, but also the impact of electrical parameters is relatively small..