The Suppression Of Three-phase Transformerless Inverter Leakage Current

In the context of innovation-driven,the transfoermation and upgrading of energy industry is imminent.In renewable energy sphere which is represented by solar energy utilization is going through the technical improvement,with the constant deeping of researching on photovoltaic power connection.Traditional photovoltaic inverters are cumbersome and ineffective because of its huge transformers.Transformerless photovoltaic inverters are liked by many scholars and photovoltaic power workers because of its advantage in volume weight and efficiency.While further study shows that the leakage current which comes from the transformerless photovoltaic inverters system and grid would hurt electricity workers and power grid.This paper proposed a new ten-switch three-phase transformerless inverter based on so many deeply research.The proposed inverter topology and its method could restrain the leakage current into safety standard,which provide a solution for grid-connected photovoltaic inverter system.Firstly,this paper introduces development of PV inverters and grid connected standard.Some cross-sectional transformerless inverters topologies are listed.Secondly,it builds a math modeling based on typical three-phase inverter to explain the source of leakage current and elicit that reducing commom mode voltage changing rates could control the leakage current.An improved topology was proposed after the simulation result shows that traditional transformerless invters could not reduce the leakage current effectively.The capability in limiting commom mode voltage changing rates of proposed topology depends on four extra switches in DC side.Then simulation result shows that the ten-switch topology with corresponding control method has better suppression results in reducing the leakage current.After analysing working principles,the hardware circuit including main circuitand control circuit are designed specifically.Next,the PCB schematic diagram is graphed in drawing board which is preparing for building experimental platform.Finally,the experimental prototype is produced according to the requirements and its power level is three-phase total 600 VA.The experimental results are similar to simulations which prove that the proposed ten-switches inverter could restrain the leakage current effectively.