Study On The PWM Rectifiers For Doubly-fed Wind Power Generation

Due to the huge consume of global energy and heavy pollution of environment which non-renewable source causes day by day, as a green, clean and renewable source, wind power gains more and more attention by governments from different countries in the world.The content of this paper is organized around doubly-fed wind power generation system used in the doubly-fed machine and control technology of PWM rectifiers to research and simulate.This paper introduces the current development situation about the world wind power generation and VSCF wind power generation technology. First BDFM is studied mainly, which then discusses operating principle and deduces the rotor speed d-q mathematical model of BDFM in details, and simulation model of BDFM has been set up and analyzed in the SIMULINK environment.Direct power control strategy relatives to other control with a higher power factor and the advantages of simple structure. In the paper, operation principle of PWM rectifiers and mathematical model of three-phase voltage source PWM rectifiers are discussed. And the control structure of VO-DPC are introduced, Mainly including power calculation, switch table, sector breakdown, and hysteresis comparator and the principle of functional modules, such as analysis and mathematical modeling. The control algorithm is analyzed by simulation. Based on tradition switch table, improved on switch table, this paper presents the three switch state control stratagem to achieve better control performance.In the paper, the stator flux concept is introduced to three-phase PWM rectifier, which is defined as virtual flux: VF. And the instantaneous power can be estimated using of virtual flux. With virtual flux orientation, a new method of direct power control is gotten, called VF-DPC. This novel method has attractive merits, such as: saving voltage sensor and the low-pass filter behave of the integral. In order to achieve a direct power control strategy with constant switching frequency, a combining DPC and the space vector control is proposed. Its feasibility is verified.The paper also simply introduces the voltage-oriented control which is analyzed in the SIMULINK environment. At last this paper compares these two strategies: DPC and VOC.