一种增强型单相无变压器型逆变器的漏电流抑制拓扑

无变压器型逆变器相比变压器隔离型逆变器,具有更高的效率和更低的成本,已广泛应用于光伏并网系统。由于去除了变压器隔离,其共模漏电流问题会进一步带来严重的EMI和安全问题。针对上述问题,提出了一种增强型单相无变压器型漏电流抑制拓扑。首先,研究了经典交直流解耦方案中仍然存在的漏电流问题;继而提出了新的拓扑和相应的调制策略;最后,搭建了2 k W的实验平台,对提出新拓扑的有效性进行了验证,并与HERIC逆变器进行了对比分析。

Enhanced Single Phase Transformerless Topology for Leakage Current Elimination

The transformerless inverters are widely employed in grid-tied PV systems, since they feature higher efficiency and lower cost compared to the transformer based inverters. One of the critical problems for transformerless inverters is the common-mode leakage current issue, which leads to serious safety and EMI problems. This paper proposed an enhanced single-phase transformerless inverter with hybrid voltage clamping to further eliminate the common-mode leakage current. Firstly, the leakage current problem caused by the parasitic parameters in the AC-decoupling and DC-decoupling based inverters is explored. Then, an enhanced transformerless topology is proposed with its modulation and leakage current elimination principle. Through hybrid voltage clamping, the common-mode voltage can be kept constant, which helps reduce the leakage current and achieve excellent differential-mode characteristics. Finally, a 2kW test bench is built to verify the effectiveness of the proposed enhanced inverter by comparing its performance with the HERIC inverter.Key words: PV grid-connected system; transformerless inverters; leakage current.