A space vector modulation method for dual three-level inverter system zero sequence voltage elimination

Abstract

A space vector modulation method for dual three-level inverter system zero sequence voltage elimination belongs to inverter system space vector modulation methods. Action time of a zero vector in each switch period is adjusted to make an average zero sequence voltage of a dual three-level inverter system to be 0. A reference voltage vector is decomposed in to two equivalent reference voltage vectors. The magnitudes of the equivalent reference voltage vectors are the same and the angle between the directions of the equivalent reference voltage vectors is 60 degrees. The amplitudes of the two equivalent reference voltage vectors are 1 / the square root of 3 of the amplitude of the reference voltage vector, and are respectively and individually produced by two diode clamping type three-level inverters to realize elimination of an instantaneous value of a zero sequence voltage of the dual three-level inverter system. The method and the principle are simple. The structure is clear. The two three-level inverters in the three-level inverter system are made to work in a power supply mode of a single direct voltage source through a unified high-speed algorithm and space voltage vector decoupling, so that the topological structure can be effectively simplified and the cost can be reduced. The four-quadrant operation of open winding asynchronous motor can be realized.

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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