Research On Anti-load Disturbance Of Three Level Dual PWM Converter Based On DC Bus Current

Three level NPC(diode neutral point clamped)dual-PWM converter is widely used in middle high voltage and power variable speed drive field for its double power flow,higher DC bus voltage,lower current harmonic distortion and other advantages.However the inverter running status and the load carried changes will cause the DC bus voltage fluctuation,and impact the safe operation of the system.This paper mainly researches on anti-load disturbance of three level dual PWM converter.The content of the paper can be divided into the following parts:The working principle was analyzed and function model and space vector pulse width modulation method was built.Generally,rectifier and inverter sides are controlled independently for its different function and different goal in three level dual PWM converter.The voltage and current double closed-loop controlling method based on grid voltage-oriented was applied in rectifier and VVVF(variable voltage variable frequency)in inverter.The load current feed forward control based on power balance was added in inner current closed-loop to improve anti-load disturbance of DC bus.Considering the difficulty of getting DC bus load current in dual PWM converter system,the high frequency DC bus current is reconstituted and the components of it are analyzed.The DC bus load current which reflect the power consumption of inverter load is extracted from high frequency DC bus load current based on active power conservation and a great deal of simulation data analyzed.The method of getting DC bus load current which can reflect the operation status and load balancing of the inverter in time is easy.The DC bus load current is used in feed forward control,which can availably restrain the system anti-disturbance.Lastly the software and hardware of of feed forward control based on DC bus load current which can improve DC bus voltage anti-load disturbance were designed in test platform of three level dual PWM converter which base on the controller of TMS32028335 core controller.The result verified the algorithm is validity and efficiency.