Research Of Switched Coupled-inductor Z-Source Inverter With Soft-switching Condition

As a mature and effective technology,voltage source inverter is widely used in many fields such as vehicle power supply and uninterruptible power supply.However,the traditional inverter structure has serious drawbacks,which makes it vulnerable to electromagnetic interference,resulting in serious damage to the circuit;and does not have the boosting capability.After the cascaded DC converter,the cost will be increased accordingly.If problems occured,maintenance is difficult,so its application is limited.The Z-source inverter breaks the limitation of the traditional voltage source inverter,and realizes the function of the boost inverter through the shoot-through state,and have a very broad application prospect.This paper presents a new single-stage soft-switching boost inverter—a high-gain coupled inductor soft-switched quasi-Z-source inverter.The circuit has a large boost range and high efficiency.The proposed inverter circuit can adjust the DC link voltage by adjusting the coupling inductor ratio and the shoot-through duty ratio of the inverter,and get rid of the excessive dependence of the output of the Z-source inverter on the shoot-through ratio.The two-degree-of-freedom adjustment method fully resolves the contradiction between the shoot-through duty ratio and the modulation factor,so that the circuit maintains a small duty cycle and a high modulation factor at high output gain and high boost ratio.The additional diode enables the switching transistor and the diode to operate under soft switching conditions.The reverse recovery stress of the diode is significantly reduced,and the leakage inductance energy is transmitted to the load,which effectively suppresses EMI and improves the efficiency of the circuit.The working states of the quasi-Z source inverter with soft-switching function with coupled inductor are analyzed in detail.The voltage gain expression of the proposed circuit is obtained through analysis and calculation.In the following research,the analysis and derivation The influence of different parameters(boost factor,parasitic parameter,leakage inductance)on circuit performance is based on this,which provides a theoretical basis for the design and optimization of subsequent circuit parameters.In this paper,the small-signal model of the pre-stage booster circuit of the coupled-inductor soft-switched quasi-Z source inverter is analyzed by state space averaging method.Based on this,a closed-loop control strategy applied to the circuit is proposed,and achieved stable control of the DC link voltage of the inverter.In order to verify the correctness of the theory,a model is built on the Saber to verify the correctness of the analyzed circuit theory,and a 1k W experimental prototype is built in the laboratory to further verify the feasibility of the circuit.Simulation results and experimental results prove the correctness of the theoretical analysis and the practicability of the proposed SCIZSI circuit.