Research Of A New Soft-Switching Quasi-Z-Source Inverter

Power electronics technology penetrates into all fields of industrial production and national economy,and its development has changed the contemporary society extensively and profoundly.Voltage source inverter is one of the most representative topologies in traditional power electronics technology.However,due to its own limitations,it is difficult to meet the current needs: 1.Mistriggering caused by it poor electromagnetic interference resistance will lead to short-circuit of inverters,damage switches and even DC power supply,which will have a fatal impact on the work of inverters.2.The threephase AC output voltage of voltage source inverters can not be larger than the DC-link bus voltage,so they can only be used as step-down inverters.The introduction of Z-source inverters provides a new theory for power conversion topology.Based on the quasi-Z-source inverters which derived from Z-source inverters,this paper has analysed the shortcomings of quasi-Z-source inverters compared with traditional two-stage Buck-Boost inverters,that is,the power loss mainly caused by hard switching.Based on this shortcoming,a new soft-switching quasi-Z-source inverter is proposed in this paper.On the basis of quasi-Z-source inverter,a resonant network including coupling inductor,resonant capacitor and diode is added.Through resonant circuit,all active devices in the circuit work in soft switching state,which reduces switching loss,improves the problem of EMI and improves converter’s performance.The efficiency of the converter is improved,the safety of the converter is increased,the practical value of the converter is higher,and the converter is easier to be high frequency.Compared with the traditional voltage source inverters which prohibit the bridge arm shoot-through,the new inverters regard the shoot-through state as one of its working modes.The shoot-through state enhances the reliability of the circuit,the resonant network can store energy in the shoot-through state and regulate the DC link voltage in a wide range.At the same time,compared with Z-source inverters,the new inverters proposed in this paper have continuous input current and lower capacitor voltage stress,so the circuit performance is improved and the device selection is more flexible.In this paper,the working modes of the new resonant soft-switching quasi-Z-source inverter at different stages are analyzed,the soft-switching mechanism is described,and a series of suitable topologies for the resonant network are introduced.On this basis,the small signal model of the front stage of the new inverter is established by using the state space averaging method,and the transfer functions of input and output signals of each part of the system under the influence of parasitic parameters are derived.Then the schematic diagram and PCB of the new inverter are designed,and the working principle of each part of the hardware is described in detail.The software design of the inverter is completed with DSP28335 as the controller.All modules involved in the software are introduced,and the functions of control,sampling and closed-loop are completed.Saber is used to simulate the current and voltage waveforms of the key components of the new soft-switching quasi-Z-source inverters.The feasibility of the proposed new inverters is verified theoretically.An experimental prototype with a power of 1k W is built in the laboratory to verify the results.The experimental results are consistent with the theoretical analysis,which verifies the correctness of the theoretical analysis and proves the new type proposed in this paper.Feasibility of soft-switching quasi-Z-source inverters.