Research On High Efficiency Single Phase Inverter Based On Critical Conduction Mode

With the introduction of the carbon peaking and carbon neutrality goals,China has embarked on the transformation of its energy industry,and new energy sources such as solar,wind,tidal and nuclear energy are gradually coming into the public view.Among many new energy types,solar energy is the most ideal one.It has many advantages such as abundant reserves,safety and reliability,long service life and low operating cost.Therefore,solar energy has been recognized as the most promising new energy in the world,and solar photovoltaic power generation has become a research hotspot all over the world.It can be seen that the research on solar photovoltaic power generation has important academic value and social significance.In this paper,the core component of solar photovoltaic power generation system DC-AC converter is taken as the research object.Through the investigation of off-grid inverter circuit topology and soft switching mode,the power topology of single-phase full-bridge inverter is determined,and the soft switching mode based on critical on-mode(CRM)is adopted.The working principle and characteristics of soft switch under unipolar and bipolar modulation of CRM are analyzed in detail.According to the characteristics of the two modulation modes,the improvement direction of CRM modulation is explained and the modulation scheme of CRM is optimized.The CRM control method based on hysteresis control is introduced first,and the problem of high-frequency instantaneous current detection when the hardware circuit is designed with high operating frequency is pointed out.Finally,the CRM control method based on ZCD is adopted.At the same time,the hardware delay problem existed in direct application of ZCD to reset is pointed out and the corresponding time compensation method is given.In order to verify the rationality of the closed-loop design,the closed-loop control system is simulated by MATLAB simulation platform.Then,according to the design index,the key components such as filter inductor,filter capacitor,and switch device are selected and the experimental prototype is built.Finally,in order to compare the efficiency before and after the optimization of the control mode of the design prototype,the loss estimation model of the CRM inverter is established.The switching loss,on-going loss,drive loss and inductor loss of the selected devices are calculated respectively,and the converter efficiency is estimated.The designed CRM modulation scheme is verified by experiments.The experimental results show that ZVS of the full output voltage range of the full-bridge inverter can be realized according to the optimized CRM modulation strategy,and the experimental testing efficiency is basically consistent with the predicted efficiency.