On MPPT And Single-phase Grid-connected Inverter In Wind Power Generation System Based On Direct-drive Permanent Generator

Energy is the motive power of human society’s development, and the consumption of energy is increasing more and more. It is well known that coal, petroleum and natural gas are non-renewable energy resource, so these three kinds of major energy will be exhausted. At the same time, environment pollution is more and more serious. People have to look for new alternative energy. Because wind energy is one kind of rich and clean energy, wind power generation has been paid much attention. However, the instability of wind speed can cause that the wind energy utilization efficiency is lower, hence, improving the utilization efficiency to increase the output power has always been the goal of using wind power, which is one of research hotspots recently.This paper introduces several methods of wind power generation, and analyzes wind power system based on the direct-drive permanent magnet synchronous generator. Rectifying circuit composed of diodes and BOOST topology are chosen as front converter at turbine side, which can be used to realize the maximum power point tracking (MPPT) control. It is worth mentioning that the oscillation would usually occur near the maximum power point, as the result that the system would be instable, if common P&O MPPT control method was implemented, In view of this situation, this paper puts forward a adaptive and variable step P&O method to suppress the oscillation near the MPP. If perturbation direction of duty-cycle changed one time, the step of duty cycle rate would be decreased, this step would be changed with the oscillation number automatically. The variation of wind speed can be decided by the rate calculated by△P/P, here,△P is the difference between the two adjacent power, and P is current power, In this paper, the sliding mode control is employed to make inverter generate electricity into mains base on the ordinary exponential reaching sliding mode method, which improves the system’s dynamic response, and effectively increases the robustness of the system.In this paper, the wind power system was modeled and simulated with the aid of MATLAB/SIMULINK software. The feasibility of the proposed adaptive verifying step method is verified by simulation and the robust of sliding mode variable structure control is gotten. A2KW experimental prototype has been developed to verify. In this experimental prototype, the DSP TMS320F2812from TI is adopted and the full digital control algorithm is used to control the system. The experimental results show that, the system has good dynamic and steady response performance, the presented MPPT method can rapidly track power variations caused by wind speed, and effectively suppress the oscillation. And sliding mode control can work well to implement power generation.