Research Of Novel Single-Phase Multi-Cell Voltage Source Inverter

In order to deal with the grim situation of the shortage of fossil fuels and the worsening of environment,renewable energy generation has developed rapidly,such as wind energy,solar energy,biological energy,geothermal energy and wave energy,etc.In the meantime,the PWM converter,as the key component to convert the electrical energy,has been variously used in the renewable energy generation.The use of traditional voltage source inverter is limited on account of its strict requirements for the battery voltage in DC side,which couldn't meet interconnection requirements when the DC voltage is lower than the AC peak voltage.The promotion and usefulness of traditional current source inverter is also limited for the large loss of reactor,bulk mass and high cost,etc.Therefore,the converter which is the use of more diversified and more flexible,has become one of innovative and challenging research directions in renewable energy generation.Firstly,this paper proposed a novel single-phase multi-cell voltage source converter topology,which is very suitable for low voltage,and the operation principle and voltage output characteristic are studied.The unipolar PWM control strategy is adopted for hybrid DC/AC modulation signal in this proposed novel single-phase multi-cell VSI topology,and the relationship between output AC voltage and AC modulation signal,which lay the foundation for subsequent VSI system analysis.Secondly,VSI working modes and arm currents change regulation under unipolar PWM control strategy are analyzed in detail.Based on the energy conservation of AC side and DC side,the design method for H-bridge capacitor is studied,beside,through analyzing typical equivalent circuit of different modal,the design method for loop inductance is proposed.In the end,2kW PSIM simulation system and experimental prototype are fabricated and tested,and VSI system operate with steady-state load,step load and induction load are verified.The simulation and experimental results verify that the change regulation of arm current is in accordance with theoretical analysis,the design methods of capacitor and loop inductor are reasonable,the proposed single-phase multi-cell converter system can realize power conversion from low DC voltage to high AC voltage,even with the step load and induction load,the good performance also could be obtained.