摘要：由于负载的不对称、输电线路的老化、电网电压的不对称故障等原因，并网变流器的接入端常出现电网电压不对称的现象。若电网电压不对称故障下不采取一定控制策略，并网变流器的直流侧端电压、交流侧电流和有功无功功率将出现二倍频振荡。这将严重影响到并网变流器的稳定运行。因此研究不对称电网电压下并网变流器的控制十分有必要。本文以并网变流器为研究对象，对其在不对称电网电压下的运行特性进行理论分析与仿真验证。首先建立了并网变流器在不对称电网电压下的数学模型，理论分析了电容电流谐振闭环对直流侧电压二倍频脉动抑制、无功功率谐振闭环对网侧无功功率二倍频脉动抑制的合理性，并通过仿真验证了本文所提出控制策略的有效性。通过对直流侧电压和网侧无功功率二倍频振荡的抑制，提高了并网变流器在不对称电网电压下安全稳定运行能力。
关键词：并网变流器；电网电压不对称；直流侧端电压；无功功率；二倍频脉动
Abstract: Because of the asymmetry of load, the aging of transmission line, the asymmetry of power grid voltage and so on, grid connected converter often appears grid voltage unbalance at the point of common coupling. If the unbalanced conditions is ignored, the DClink voltage, the AC current and the active and reactive power of grid connected converter will appear doublefrequency ripple. That will affect the stable operation of grid connected converter, even ruin it. Therefore, it is necessary to study the control of grid connected converter under unbalanced grid voltage. In this paper, grid connected converter is the research object. Theoretical analysis and simulation of its operating characteristics were done under unbalanced grid voltage. Firstly, the mathematical model of grid connected converter was established. Theoretical analysis was made on the suppression of the two harmonic ripple of the DC side voltage through the capacitor current resonant closed loop and the reactive power through the reactive power resonant closed loop. And by Matlab/Simulation the proposed control strategy was proved to be effective. The security and stability of grid connected converter under unbalanced grid voltage was improved through the suppression of the two harmonic ripple of DC side voltage and reactive power.
Key words: grid connected converter; grid voltage asymmetry; DCvoltage; reactive power; doublefrequency ripple