The Design Of LCL Filtered Three-level PWM Rectifier Control System

In recent years,with the development of new energy industry,the three-level PWM rectifier is widely applied.As an interface between various power electronic systems and the grid,there are harmonic waves in the rectifier.If the harmonic waves are not controlled,they will seriously affect the quality of the grid.Therefore,it is necessary to replace single inductance filter with the LCL filter,which can suppress high order harmonics and make the system respond quickly.However,there are resonances in the LCL filter.Thus,how to improve the filter performance through parameter design becomes the main problem in this thesis.The three-level PWM rectifier is the research object in this thesis,and its mathematical model in the two-phase rotating coordinate system is derived through the principle of coordinate transformation.The principle and implementation process of the three-level SVPWM modulation method are analyzed in detail.Then,the resonance suppression method is discussed for the resonance problem brought by the LCL filter.An improved derivation method of LCL filter parameters is proposed and the actual calculation example is given.In order to obtain a good control effect,a double closed loop structure composed of a voltage outer loop controller and a current inner loop controller is designed.The voltage oriented vector control strategy is used to realize the unit power factor operation of the rectifier and stabilize the DC voltage.The MATLAB/SIMULINK is used to conduct simulation experiments on the designed control strategy and modulation strategy.Finally,the physical experiments arc carried out on the rectifier control system platform with the TMS320F2812 DSP as the main control core.The experimental results show that the LCL filter resonance is effectively suppressed,the voltage on the DC side is stable,the grid side current has a fast dynamic response,and the anti-disturbance capability is strong.