基于部分功率变换器的电力系统接地故障诊断方法

Partial power converters (PPCs) have proven to be efficient, high-density solutions that reduce electrical stress. However, due to their lack of maturity, PPCs still require an extensive analysis of their reliability. Despite their capability of varying the voltage level between its terminals, similarly to a power transformer, they cannot provide galvanic isolation between both sides. Then, in the event of a ground fault, the entire system becomes highly exposed. Therefore, this paper presents a ground fault detection method for PPC-based solutions. The approach relies on a grounding resistor that is sequentially linked between the positive, negative, and midpoint terminals of the DC systems, grounded by three different switches. The paper provides a detailed explanation of the methodology and the necessary components to perform the diagnosis. A simulation setup conducted in MATLAB-Simulink is presented, along with its results. Afterwards, an experimental 50-kW Input-Series-Output-Parallel PPC test bench is used under both healthy and faulty scenarios to validate the methodology. The results conclude that this method not only detects the ground faults, but it also discerns its location, reducing the maintenance work.