A Novel Three-phase Current Type Sepic Inverter Capable Of Suppressing Common Mode Current

The common mode current problem is one of the problems to be solved in the application and promotion process of non-isolated photovoltaic inverters.In this paper,three-phase non-isolated photovoltaic inverters were taken as research objects.The three-phase non-isolated photovoltaic inverters that can achieve common-mode current suppression were briefly described from the perspective of improving system modulation and changing the topology.And in view of the shortcomings of traditional voltage-type inverters and current-type inverters that can only achieve step-up or step-down output,several three-phase non-isolated photovoltaic inverters that were applicable to a wide range of voltage changes were introduced.Based on the related literature,a new three-phase current type Sepic inverter was proposed in this paper through the method of topology construction.The inverter can realize the single-stage buck-boost function,and the use of a smaller inductance and a small-capacity electrolytic capacitor within a certain power range can achieve the system common mode current suppression and was suitable for a wide range of voltage fluctuations.The inverter was formed by multiplexing the Sepic circuit and the three-phase bridge arm switch tube,and the electrical isolation between the solar panel and the power grid was achieved by constructing a DC bypass,which can effectively perform the common mode of the system Suppression of current.This inverter can be divided into two different working modes according to the flow direction of the intermediate inductor L₂ current,and the operating principle of the two different modes was introduced.Secondly,it combined the sinusoidal pulse width modulation?SPWM?technology,the common-mode voltage expression of the inverter in any switching state was derived,and the system's model was built to analyze the two different operating modes of the inverter Derivation of mathematical relations.Based on this,this paper through modeling analysis of the new three-phase current type Sepic inverter,determined the closed-loop control strategy of the inverter under passive load and grid connection conditions,and designed the corresponding regulator Then,for two different operating modes of the inverter,the simulation verification under open loop,passive load and grid-connected conditions were performed,and corresponding verifications were performed with theoretical analysis.Finally,the device selection and the DSP?TMS320F2812?+FPGA?XC6SLX9?digital control experimental platform were set up.The new three-phase current type Sepic inverter was tested on the experimental platform in open loop,passive load and grid connection.The experimental resulted verify the correctness and feasibility of the theoretical analysis.