Research On Single-phase Dual-mode Two-stage Full-bridge Dual-Buck Photovoltaic Inverter

Single-phase two-stage inverter in photovoltaic power generation system has the characteristics of high efficiency,high voltage utilization and flexible system configuration.The traditional single-phase two-stage inverter usually uses the traditional Boost to improve the input voltage level in the first stage,and the traditional bridge inverter structure is used in the second stage.The traditional two-stage inverter used in new energy power generation has a large optimization space.In this paper,the structure improvement and efficiency improvement of the traditional single-phase two-stage inverter topology are studied based on the single-phase two-stage inverter in photovoltaic distributed household applications.Firstly,the background of the topic and the current research status of single-phase photovoltaic inverter are introduced.Starting from the existing architecture in this field,the circuit topology working principle and advantages and disadvantages of the existing singlephase two-stage inverter framework are discussed.On this basis,the optimization idea of single-phase two-stage dual-mode full-bridge dual-Buck inverter topology studied in this paper is formed.Secondly,the specific optimization method of the traditional “Boost + Full-Bridge”two-stage inverter is illustrated.Aiming at the situation that the output voltage of the new energy power generation is insufficient,the boosting capability of a traditional Boost circuit is limited,the working current is large,and a switch tube is often required to be in a limit duty ratio,three-phase coupled-inductor parallel Boost topology is used into a front stage boosting unit to replace the traditional Boost circuit;Aiming at the straight-through problem of the bridge arm in the traditional bridge inverter circuit,the full-bridge dual-Buck inverter topology is adopted in the rear stage;The traditional two-stage inverter usually works in the mode of constant DC bus voltage,the input voltage will rise first and then drop,which will cause unnecessary switching losses to the switches of the first stage working at high frequency.Combined with the multi-level idea,the dual-mode switching mode is adopted.By optimizing the front and rear stages of the two-stage inverter,the single-phase two-stage full-bridge dual-Buck inverter topology is given.Then the working principle and state of the improved single-phase two-stage inverter topology are analyzed theoretically.The state space average mathematical model of the system is established,and its dynamic model is further constructed by introducing small perturbation.The system control network is designed by combining the system mathematical model and modulation strategy.Subsequently,the actual hardware parameters and software implementation of the system main circuit and control circuit are designed,and the selection of improved single-phase two-stage inverter topology device parameters and software implementation process are given.Based on the improved singlephase two-stage inverter topology analysis and design,further use of PSIM to build circuit simulation model,through the simulation analysis to verify the single-phase two-stage inverter topology improvement optimization effect.Finally,a single-phase two-stage dual-mode full-bridge dual-Buck inverter topology prototype is built for physical experiments.Through the experiments,the correctness of the topology and dual-mode switching mode is verified.