Neutral point voltage balance control system and method based on power factor angle

Abstract

The invention discloses a midpoint voltage balance control system and method based on power factor angle. The system includes a multilevel inverter and a digital processing control module, wherein the digital processing control module includes a sampling unit, a closed-loop control unit, a digital phase-locked loop unit, a midpoint voltage control unit and a SPWM pulse width modulation unit. The sampling unit collects the DC bus voltage signal of the multilevel inverter, the midpoint voltage signal of the DC bus, and the three-phase voltage and three-phase current signals output by the multilevel inverter, and the three-phase modulation wave, The power factor angle is obtained through the operation of the digital phase-locked loop unit; the three-phase modulation wave, the power factor angle and the midpoint voltage signal of the DC bus are processed by the midpoint voltage control unit to obtain a new three-phase modulation wave, and then processed by the SPWM pulse width modulation unit A pulse width modulation control signal is obtained, and the signal controls the working state of each phase switch tube of the multilevel inverter through a driving circuit. The method of the invention can reduce the low-frequency pulsation amplitude of the midpoint voltage and realize the balance of the midpoint voltage.

Description

Technical field [0001] The invention belongs to the field of control technology in power electronic conversion technology, in particular to a midpoint voltage balance control system and method based on a power factor angle. Background technique [0002] In recent years, multi-level inverters have been widely used in high-voltage, medium and high-power conversion occasions; its circuit topology and control methods have become current research hotspots. Compared with the two-level inverter, the multi-level inverter has more output levels, and the obtained step wave platform has more orders, so that the closer to the standard sine wave, the less harmonic components. [0003] The topology of multi-level inverters can be roughly divided into three categories: diode clamp type, cascade type, and flying capacitor type. Among them, diode clamp type inverters are the most widely used. Taking a three-level inverter as an example, a three-level diode clamped inverter can be divided into a mi...

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Problems solved by technology

For example: Literature 1 (Gong Bo, Cheng Shanmei, Qin Yi. Carrier-based three-level neutral point voltage balance control strategy [J]. Journal of Electrotechnical Society, 2013,28(6):172-177.) and patent 1( Cheng Shanmei, Gong Bo, Ning Bowen, Liu Jiang. A mid-point voltage control method for NPC type three-level inverter based on carrier amplitude shift: China, CN201210140269.0.2012-09-19.) A carrier-based The variable-amplitude SPWM control scheme realizes midpoint voltage balance by sampling the midpoint voltage and changing the carrier amplitude in real time. The low-frequency pulsation has no control effect, and the adjustment period is long and the adjustment accuracy is not high

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