A High Power Density Single-Phase Inverter Based On Boundry Current Mode

Inverter is one of the important parts in distributed new energy generation system.It is very meaningful to realize the miniaturization and portability of the medium and small inverter.This paper is to realize the high power density of inverter under the premise of high efficiency.In this paper,the principle of soft switching based on critical current continuous control strategy is analyzed in detail.The control method is to achieve the soft switching at the expense of the conduction loss,which is suitable for small power applications.Therefore,we proposed two parallel full bridge topology.Sharing low frequency bridge arm can reduce the number of MOSFET which can reduce the volume of the inverter and improve power density.The continuous control strategy based on critical current can be realized by unipolar,bipolar and modified bipolar modulation.In this paper,we use unipolar and bipolar modulation.The advantages of the modulation method are illustrated by the switching frequency,efficiency and the THD of output voltage and current.The feasibility of unipolar and bipolar hybrid modulation strategy is verified by PSIM simulation.The volume of the inverter is mainly determined by the power decoupling circuit,the MOSFETs and the passive filter.In this paper,the volume optimization is carried out from the two aspects,the inductor and capacitor of the filter.For inductance,the material and the shape of magnetic core are selected and compared,and the core is determined by the space volume.The integration of low reluctance magnetic circuit is selected to confirm the advantage of inductance coupling.For capacitance,by comparing the advantages and disadvantages of different material of capacitors,and taking use of the space volume into account,The MLCC capacitor is connected in series and parallel.The heat treatment of inverter is an important part of high power density.In this paper,the loss of power devices is confirmed by loss analysis.Based on the first edition of the layout structure,we proposed the flat structure and hierarchical structure.The thermal simulation model was established by ANSYS Icepak,and the advantages of the hierarchical structure were confirmed from two aspects of normal temperature and extreme room temperature.According to the design index,this paper gives the design results of inverter parameters,and builds a 2k W high power density inverter experimental prototype.Using the layered structure,through the experiment,control strategy of BCM is verified,and it can realize ZVS.The coupling mode is proved validity.In light load,two parallel full bridge topology has only one road,the peak efficiency almost reach 98.4%,and CEC efficiency can reach 97.9%.The thermal simulation analysis of the layered structure is basically the same as the temperature of the thermal imager.