Carrier-based pulse-width modulation control strategy of five-phase six-bridge indirect matrix converter under unbalanced load

What is it about?

To solve the problem three-to-five phase matrix converter (MC) cannot operate under unbalanced load, a topology of five-phase six-bridge indirect matrix converter (IMC) and applies carrier-based pulse width modulation (PWM) method are proposed. An N-phase bridge is added to the neutral point of five-phase loads in inverter stage. Use space vector pulse width modulation (SVPWM) method to analyze and deduce the voltage of neutral point, and then calculate the duty ratio of N-phase bridge. Calculations of other bridge duty ratios remains SVPWM method unchanged. All of the duty ratios are used to calculate modulation waves of rectifier stage and inverter stage. Compare the modulation waves with a carrier to generate modulation signals of two-stage power switches. Use the modulation signals to control the five-phase six-bridge IMC for controlling the neutral voltage of loads as corresponding zero-sequence voltage, and five symmetrical sinusoidal output voltages are obtained under both balanced and unbalanced loads.

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Why is it important?

In this paper, a carrier-based PWM method of five-phase six-bridge IMC is proposed. The five-phase bridges are seen as a module separated from the midline bridge. Regardless of loads balanced or unbalanced, the five-phase bridges operate in the same way. When the loads are balanced, there are only five-phase bridges running with the midline bridge locked. The midline bridge is unlocked and put into operation when the loads are unbalanced. And the duty ratio of the midline bridge can be derived by the operation of five-phase bridges. This method can decrease the complexity by solving the problem in two-dimensional coordinate system, and can be widely used with low switching loss.

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