Research On Virtual Space Vector Modulation Technology In Oblique Coordinate System Of Three Level Inverter

In the field of power electronics,due to the voltage stress of the power switch device,the application of the traditional two level inverters in the field of high voltage and large capacity inverters is limited.With the development of power devices,the multi-level converter technology has been an effective approach for inverters to solve this problem.The multi-level inverters not only improves the voltage capacity limitation of power devices,and more efficient,less power loss,and the output current harmonics is smaller.Therefore,the multi-level inverter has been widely studied and applied in the high voltage and large capacity applications.The diode clamped three level inverter is a simple and practical multilevel inverter which has been widely used.But this kind of inverter also has an inherent problems that the bus neutral point is imbalance,and the problem not only affects the quality of the output current of the inverter,even damage the inverter device.In order to solve the problem,in this paper has researched the working principle of the three-level inverters and the reasones of bus neutral point imbalance,base on the diode clamped three level inverter.Analyzed the traditional of SVPWM(space voltage vector pulse-width modulation)technology how to improve the problem of bus neutral point is unbalanced,and analyzed the weakness of traditional SVPWM technology.On this basis,this paper researched the working principle of VSVPWM(virtual space voltage vector pulse-width modulation)technology which can restrain the imbalance of bus neutral point by virtual mid-vector and virtual large vector with coupled small vector.In addition,this paper proposes a virtual space vector control algorithm base on 60 degree oblique coordinate,the algorithm greatly simplifies the complexity of virtual space vector control technology.This paper also build a simulation model of diode clamped three level inverter,and simulated the realization and result of virtual space control algorithm,and the relevant experiments are carried out in a 20 kW three-level inverter prototype.The simulation and experiment verify the proposed algorithm to balance the bus neutral point potential is right.