Research On New Z-source Asymmetric Inverter And Its SVPWM Control Method

Three-level inverter because of its flexible control mode,high inverter efficiency,low voltage harmonic output,etc.,in the high-voltage high-power AC motor frequency control,active power filtering,wind power and solar Power generation and other fields have been widely used.But the three-level inverter is a step-down converter,in order to obtain a higher output voltage,in practical engineering applications,the need to add a circuit to improve the DC side voltage,no doubt this will increase the system hardware costs,Reduce the efficiency of the system.In order to overcome the above shortcomings,this paper presents a Z-source asymmetric three-level inverter.The Z-source network is no longer a morbid state when the inverter bridge is in a straight-through state.By controlling the duty cycle,the purpose of increasing the output voltage can be achieved,and the introduction of the Z source network enhances the reliability of the system,eliminating the adverse effects of the inverter on the dead zone effect.And asymmetrical bridge structure compared to the traditional NPC structure in the same power device case,do not need to clamp the diode,reducing the inverter size,saving system hardware costs.Three-level inverter DC side of the capacitor in the form of partial pressure,resulting in the inverter midpoint potential offset problem can not be avoided.This problem will cause the lower harmonics of the system to increase,and the voltage on some power switching devices will increase,and the life of the DC side capacitor and the power switching device will be shortened.Therefore,this paper deeply studies the causes of the midpoint potential offset and the method of controlling the midpoint potential balance.According to its unique upper and lower pass state insertion rule and the influence on the midpoint potential,an optimal space vector pulse width modulation(SVPWM)control strategy is proposed.By adjusting the up-and-down time,the DC boost is effectively suppressed The offset of the potential and minimizes the switching losses caused by the direct-acting operation.The feasibility and validity of the method are verified by MATLAB / Simulink simulation.