级联型电力电子变压器三相电压暂降隔离能力分析

级联型电力电子变压器(PET)在中低压配电网应用前景广泛,深入研究其电压暂降隔离能力,对于其器件参数选择、储能容量配置、减少电压暂降治理装置配置等工作具有重要价值。文中通过理论推导,研究了级联型PET电压暂降隔离能力的限制因素:针对输入级,深入研究了调制比、直流链电容电压波动以及开关器件电流有效值限制对其电压暂降隔离能力的影响;针对隔离级,详细分析了移相比、开关器件电流有效值及峰值限制对其隔离直流链电压跌落能力的影响;明确了不同设计参数下输入级和隔离级电压暂降隔离能力的主要限制因素,并建立了级联型PET电压暂降有效隔离区域。最后,通过仿真验证了研究结果的正确性。

Analysis on Three-phase Voltage Sag Isolation Capability of Cascaded Power Electronic Transformer

Cascaded power electronic transformer (PET) has broad application prospect in medium and low voltage distribution networks. In-depth study of voltage sag isolation capability of cascaded PET is of great value for parameter selection of cascaded PET device, energy storage capacity configuration and reduction of voltage sag treatment devices. Through theoretical deduction, the limiting factors of voltage sag isolation capability of cascaded PET are studied. At the input stage, the effects of modulation ratio, voltage fluctuation of DC link capacitor and RMS limit of switching device current on its voltage sag isolation capability are deeply studied. At the isolation stage, the effects of the phase-shift ratio, RMS and peak limit of switching device on the voltage sag isolation capability of DC link are analyzed in detail. The main limiting factors of the voltage sage isolation capability at the input and isolation stages with different design parameters are clarified. And the effective isolation area of cascaded PET is established. Finally, the correctness of research results is verified by simulation.