Research On SVPWM Algorithm And Neutral Point Voltage Balance Strategy Based On Three Level NPC Inverter

In recent years,multi-level inverter in the field of high-voltage high-power power electronics has been widely used,it is a new type of change,no need to increase the step-up transformer and step-down transformer and voltage equalization circuit and other hardware equipment,Mainly by changing the topology of the circuit to get high-voltage high-power output.Compared with two-level inverters,with low switching frequency,harmonic content is small,low voltage stress advantage.In this paper,the more common diode-clamped three-level inverter as a research object,the related spatial vector modulation technique and the midpoint voltage imbalance are studied deeply.Multi-level inverter is a very critical technology is PWM modulation technology,the advantages and disadvantages of the modulation method directly affect the output performance of the inverter.In this paper,the steps of three-level space vector modulation are studied in detail,including the division and selection of sectors,the selection of the basic vector and the calculation of the respective action time,the vector optimization and so on.At the same time,for its calculation process is too complex issues,two SVPWM simplified algorithms are proposed,and the correctness of the two algorithms is verified by theoretical derivation and simulation.eliminating the need for the calculation of many trigonometric functions,more conducive to the realization of real-time control of the inverter.To solve the DC side of the point of the voltage balance problem to ensure that the NPC three-level inverter normal work.In this paper,the causes and deviations of the fluctuation and offset of the mid-point voltage of the NPC three-level are briefly introduced.And the common elimination of the mid-point voltage imbalance strategy for a detailed analysis,the simulation results verifies the effect,but also analyzes the shortcomings of the existence.In view of the shortcomings of the traditional midpoint voltage control method,introduced the concept of virtual space vector VSVPWM,to do a detailed description of it,at the same time,a midpoint voltage control method and an adjustable vector control method based on VSVPWM are proposed,and according to the relevant principles,using Matlab / simulink to build the corresponding simulation model,verify its correctness and the superiority of traditional control methods.