不平衡工况下交直流配电网非隔离变换器

Transformerless Converter for AC/DC Distribution Network Under Unbalanced Conditions

非隔离变换器具有高效、经济的优势,因此在低压交直流配电网中具有广阔的应用前景,但漏电流及供电质量低的问题限制了非隔离变换器的推广应用。为此,通过构建变换器的共模等效电路,对传统四桥臂变换器进行改进,得到一种无漏电流的共地型四桥臂变换器。在此基础上,分析不平衡工况下直流侧二倍频波动及基频共模波动机理,并提出共地型四桥臂拓扑的多目标复合控制策略。最后,经dSPACE实验平台进行对比验证,研究结果表明:采用所提共地型四桥臂拓扑及复合控制策略,漏电流得到了有效抑制,双极直流母线电压保持稳定,实现了低压交直流配电网的安全稳定运行。研究结果证明了所提策略的有效性。

Transformerless converter has higher transmission efficiency and lower cost,thus it has broad prospects for application in low-voltage AC/DC distribution networks.However,the problems of leakage current and low quality of power supply limit the application of transformerless converters.Therefore,we constructed a common-mode equivalent circuit,and improved the traditional four-leg converter to obtain a common-ground four-leg converter without leakage current.Then,we analyzed the mechanism of DC-side diode and fundamental-frequency common-mode fluctuations under the condition of unbalanced load,and proposed the multi-objective composite control strategy of common-ground four-leg topology.Finally,the dSPACE experimental platform was used for comparison and verification.The results show that the proposed common-ground four-leg topology and composite control strategy can effectively suppress the leakage current and keep the bipolar DC bus voltage stable,thus realizing the safe and stable operation of the low-voltage AC/DC distribution network.The results prove the effectiveness of the proposed strategy.