Research On High-frequency Isolated Single-phase Inverter And Its Soft Switching Technology

High-frequency isolated single-phase inverters are popular in many applications because of their small size,such as photovoltaic generation,UPS,electric vehicles,aerospace and other fields.The traditional high-frequency isolated single-phase inverter only improves the switching frequency of the DC/DC stage,thereby reducing the size of the transformer,while the DC/AC stage is still in the low-frequency hard switching state.Therefore,this article will improve the switching frequency of the DC/AC stage based on the traditional high-frequency isolated single-phase inverter,and then study the true high-frequency isolated single-phase inverter.The DC/DC stage of the high-frequency isolated single-phase inverter in this paper adopted a zero-voltage and zero-current switching(ZVZCS)phase-shifted full-bridge(PSFB)converter and its principle and parameter design was given.Aiming at the problems of common mode noise of the traditional single-phase inverter in DC/AC stage,a new double-ground inverter that substantially reduces common mode noise was proposed.In the current research on inverter soft switching technology,most of them require auxiliary circuits or critical conduction mode(CRM)control methods that require zero crossing detection circuit.This paper proposed a simple soft-switching scheme that does not require auxiliary circuits and zero-crossing detection circuit.It uses the method of calculating the frequency to make the inductor current flow bidirectionally during the switching cycle,which provides the conditions for the zero-voltage switching(ZVS)of the upper and lower switches of each bridge arm.In this paper,the working modal analysis and mathematical modeling of the new circuit were provided,which provides a mathematical basis for the ZVS of the switches accurately.And the parameters of the new circuit was calculated and the scheme was simulated by MATLAB.Then the theoretical loss analysis and actual efficiency measurement of the DC/AC stage were carried out.Finally,the device selection and magnetic component design of the entire high-frequency isolated single-phase inverter,as well as the design of the DSP controller based on the TMS320F28335 were given,and a high-frequency isolated single-phase inverter experimental platform was built.The control scheme and modulation strategy of the system had been verified by experiments.The final experimental result was that the high frequency isolated single-phase inverter achieved ZVZCS of the switches in the DC/DC circuit and ZVS of the switches in the DC/AC circuit while its output was normal.This also verified the correctness of the theoretical analysis of the new circuit and the feasibility and effectiveness of the new ZVS scheme of the inverter.