Control Strategy For Improved T-type Three-level Direct-drive Wind Power System With Pmsg Based On Direct Power Control

Recently energy crisis and environmental pollution restrict the economic development,so the development of clean energy is imperative.As a kind of clean energy,wind power has become one of the most development value energy since it is inexhaustible,not harmful to environment in exploitation process.Because of its low rotational speed,low cost and low noise,the direct-drive wind turbine without increasing gearbox has become the mainstream model of wind power generation.The paper discusses improved T-type three-level inverter which is composed of the generator side rectifier and the grid connected inverter.Permanent magnet direct drive wind power grid system direct power control strategy was studied.Firstly,the paper introduces the characteristics of the wind turbine and establishes mathematical models of wind machine and permanent magnet synchronous generator.This paper uses improved T-type three-level converter structure that reduces the conduction loss greatly.The SVPWM control algorithm based on 60°coordinate system simplifies the calculation of trigonometric functions greatly,and simulation comparison is given.In addition,the SVPWM algorithm is used to control the midpoint potential balance based on the positive and negative small vector redistribution and achieve good results.Secondly,Predictive direct power control is adopted for the generator side rectifier,and the theoretical analysis and mathematical modeling are carried out.The SVPWM control strategy can obtain the fixed switching frequency and control the system’s active power and reactive power instantaneously.The PI regulator is nonessential in power inner loop control;the system parameters is simple and dynamic effect is good.The control strategy which based on direct power control(DPC)with virtual flux(VF)is introduced to the grid connected inverter.The active power and reactive power of the grid side are directly estimated by the DC voltage and the switching function.No AC voltage sensor can simplify the system structure,reduce system cost,improve system efficiency.The results of MATLAB / Simulink simulation are consistent with theoretical analysis.Thirdly,experimental experiments were carried out on the TMS320F2812experimental platform,based on the theoretical analysis and simulation results.The experiment realizes direct-drive wind power system direct power control.The results show that the proposed scheme is feasible and correct.