Method and device for optimizing farthest vector PWM (Pulse Width Modulation) of two-level converter

Abstract

The invention provides a farthest vector PWM optimization method for a two-level converter. According to the method, for a two-level converter, a specific offset is injected into a three-phase sine wave in a preset space angle region, and a three-phase dual-modulation wave expression for optimizing farthest vector PWM is obtained; an initial rising direction triangular carrier is used in a first reference space angle region, and an initial falling direction triangular carrier is used in a second reference space angle region, so that a single carrier expression for optimizing the farthest vector PWM is obtained; and a control signal of each switching device is obtained by comparing a three-phase dual-modulation wave with a single carrier, so that the farthest vector PWM is optimized based on the carrier. The invention further provides a farthest vector PWM optimization device for the two-level converter, compared with a traditional farthest vector PWM method, the farthest vector PWM optimization device for the two-level converter has the advantages that the three-phase switching frequency can be balanced while the common-mode voltage amplitude and frequency are reduced, three-phase simultaneous action is prevented, and the farthest vector PWM optimization device is simple in calculation and convenient to implement.

Description

technical field [0001] The invention relates to a PWM control method, in particular to a method for optimizing the farthest vector PWM of a two-level converter. Background technique [0002] The topology of the main circuit of the two-level converter is as follows: figure 1 , by controlling the turn-on and turn-off of the two switching devices of each phase from top to bottom, the two-level converter can output two different level states. Due to the advantages of simple structure, convenient control and fast dynamic response, two-level converters are widely used in new energy power generation, metallurgical mining and rail transportation and other fields. [0003] Define the two level states of the two-level converter output from high to low as P and N, and the DC side voltage is 2E, then the space vector of the two-level converter can be summarized in figure 2 . Among them, the switch states and amplitudes corresponding to each space vector are listed in Table 1. [00...

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Problems solved by technology

[0010] In addition, the above two farthest vector PWM methods are both based on space vector synthesis reference voltage, which needs to calculate the action time of each space vector and preset the switching action mode in each space angle area, the steps are cumbersome and the calculation is complicated , is not conducive to engineering promotion and application

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