Research For Inverter Loss Reduction And Noise Reduction Key Technology Of Direct-drive Wind Power System

With the increasing depletion of fossil energy,wind energy is becoming a hotspot, so that in the power system, the proportion of wind power is being larger and larger. With the increase of wind turbine unit capacity, appropriate converter must be developed in time; with the increase of the total wind power capacity, wind power qualities have a significant impact on the power system. For large capacity and high voltage levels of the direct-drive wind power system, the high switching frequency of the converter will cause switching devices generate losses and Highfrequency noise. Therefore the research of inverter loss reduction and noise reduction is a meaningful thing.In this paper, the study is for the direct-drive wind power system, Topology of direct-drive wind power system and mathematical model of wind turbines, PMSG,PWM converter all have been analyzed, and converter control strategy has been proposed, at the same time the Simulation results verified the control strategy. The LLCL filter was proposed to be adopted to suppress harmonic near the high switching frequency, filter characteristics and structure of L filters, LCL filters and LLCL filters were analyzed, in order to suppress harmonic near the high switching frequency as well as possible, the constraints of parameter about LLCL filters were discussed, the simulation results of typical system model showed that LLCL filter can suppress harmonic near the switching frequency more effectively.In order to reduce the loss of switching device, ZVT soft-switching is proposed to be adopted. The topology of ZVT soft switching inverter is researched; ten modes are used to analyze its single-phase equivalent circuit. Current and voltage values of resonant circuit are showed by mathematical formulas, and its trend is showed in diagram. Finally, for different load current value, the results of simulation in PSCAD verified the theoretical derivation. In the main circuit and resonant auxiliary circuit, so the switch does not generate losses.