Space Vector Modulation Method for Zero Sequence Voltage Elimination in Dual Three Level Inverter System

Abstract

The invention relates to a space vector modulation method for zero-sequence voltage elimination of a double three-level inverter system, which belongs to the space vector modulation method of an inverter system. Adjust the action time of the zero vector in each switching cycle so that the average zero-sequence voltage of the dual three-level inverter system is 0, and use the unified fast algorithm and space voltage vector decoupling to decompose the reference voltage vector into two equal-sized, Equivalent reference voltage vectors whose direction is 60° to each other, and the amplitude of the two equivalent reference voltage vectors is twice the amplitude of the reference voltage vector, and are separately generated by two diode-clamped three-level inverters , to realize the elimination of the instantaneous value of the zero-sequence voltage of the dual three-level inverter system. The principle of the method is simple and the structure is clear. Using the unified fast algorithm and space voltage vector decoupling, the two three-level inverters in the dual three-level inverter system work in the power supply mode of a single DC voltage source, which effectively simplifies the topology. structure and cost reduction, and realize the four-quadrant operation of the open-winding asynchronous motor.

Description

technical field [0001] The invention relates to a space vector modulation method for an inverter system, in particular to a space vector modulation method for zero-sequence voltage elimination in a double-three-level inverter system. Background technique [0002] In recent years, the harmonic content of the output voltage of the multilevel inverter is low, and the switching stress on the semiconductor device is small, and it has been more and more widely used in the medium, high voltage and high power occasions. Compared with diode clamp type, flying capacitor type and H-bridge cascaded inverters, when the number of switching devices is equal, the open-winding asynchronous motor double-ended cascaded inverter can provide more power to the load. The number of levels produces less output voltage and current harmonics, so its application potential in the field of multi-level inverters and drives is more prominent. However, the problem of zero-sequence voltage generated by this...

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Problems solved by technology

[0004] The analysis of the above control methods shows that the independent DC voltage source used in method (1) supplies power to two three-level inverters. Although the zero sequence voltage of the system is not zero at this time, there is a large zero in the system sequence voltage, but because the DC voltage sources of the two inverters are isolated and no loop is formed inside the system, the zero-sequence current of the system is 0 at this time, which has no effect on the operation of the system, but this method will increase the equipment of the system cost, and it is difficult to realize the four-quadrant operation of the motor; methods (2) and (3) only dynamically eliminate the zero-sequence voltage of the dual-three-level inverter system in an average sense, and the zero-sequence voltage in the inverter system The amplitude of the voltage is still high

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