Research Of A Novel Quasi-Z-Source Inverte With Voltage Multiplier Cells

With the gradual consumption of traditional fossil energy,the environmental pollution problems caused by it have gradually become serious.As a renewable energy source,the use of solar energy does not produce harmful substances,and its utilization can effectively alleviate energy problems.Between the photovoltaic module and the grid,an inverter is required to implement the DC-AC conversion.The conventional voltage-type inverter belongs to a buck converter.In order to achieve the required inverter output voltage level,the voltage needs to be first increased by the DC-DC converter,which increases the complexity of control and the number of components.The upper and lower arms of the voltage type inverter are not allowed to be turned on at the same time,otherwise a short circuit will occur on the DC side,which will cause damage to the inverter.Therefore,in the driving signals of the upper and lower arms,the dead time is injected to prevent Mis-conduction,but the dead time causes the output sinusoidal voltage to be distorted and the DC link voltage utilization rate to decrease.Single-stage boost inverter—Z source inverter overcomes the shortcomings of traditional voltage-type inverter.The Z source inverter adds a shoot-through signal to the control signal of the inverter switches,and the shoot-through signal controls the front stage circuit to complete the state switching,thereby realizing the boost function without affecting the normal inverter,thereby greatly improving the security of system.However,Z-source inverter has shortcomings such as input current is discontinuous,poor boosting capability,and high capacitance voltage stress,which limits the application range of Z-source inverter.This paper proposes a novel quasi-Z-source inverter with voltage multiplier cells(VMC-q ZSI).The inverter combines the characteristics of the voltage doubler unit and the quasi-Z source inverter,and effectively improves the boosting capability of the inverter.The input current of the VMC-q ZSI is continuous,which reduces the capacity of the input filter capacitor and facilitates the detection and control of the input current.Due to the inherited quasi-Z-source inerter structure,the voltage overshoot at switches of the VMC-q ZSI inverter bridge is effectively suppressed,and the energy feedback of the leakage inductance and parasitic inductance is realized,which can achieve higher efficiency of the inverter.The quasi-Z source inverter with voltage multiplier cells is subordinate to the impedance source inverter in topology,and can adjust the voltage gain by the shoot-through duty ratio and the turns ratio,and has high flexibility,and can realize high voltage gain even when the small shoot-through duty ratio and improving the maximum value of the inverter modulation factor effectively,and improving the utilization of the DC link voltage,and reducing harmonic distortion.The article first introduces the workflow of several classic Z-source inverter,expounds its performance defects,and calculates its voltage relationship.Analyze the working mode of VMC-q ZSI in one cycle and calculate its voltage-current relationship.Furthermore,the performance impact of VMC-q ZSI with parasitic parameters is analyzed.Then,using the VMC-q ZSI topology structure to derive its equivalent boost circuit,the discrete-time model of the equivalent boost circuit is established,and the stable orbit parameter range is analyzed according to its nonlinear dynamic behavior and Jacobian matrix.The state space model of VMC-q ZSI is established.The small signal model suitable for closed-loop control is obtained by small signal disturbance.The closed-loop control is designed according to the small signal model.The Saber was used to verify the working process of the VMC-q ZSI and the fastness and stability of the closed-loop controller,and to design a 1000 W experimental prototype.Simulation and experiments verify the effectiveness and practicability of the quasi-Z-source inverter with voltage multiplier cells.