Four-Leg Voltage Source Converter With Independent Phase Control for Ground Fault Compensation

Electrical faults are a frequent occurrence in medium voltage (MV) distribution grids, often affecting or completely interrupting the electrical supply. Among these, single-phase faults are the most common type and passive elements such as Peterson coils have been traditionally employed to mitigate their impact and maintain a reliable power supply. However, these solutions come with inherent drawbacks, including limited flexibility and functionality, which hinder their effectiveness in dynamic grid scenarios. This work presents a novel system designed to ensure high-quality power supply continuity before, during, and after single-phase faults. The proposed approach uses already installed four-leg power converters in the grid, eliminating the need for additional passive equipment. A new control strategy is developed in the natural <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$abc$</tex-math></inline-formula> reference frame, which enables the use of classical control techniques in the MIMO system and simplifies the analysis of the output voltage loops without changing the reference frame. Simulations and experimental results confirm that the proposed control framework effectively compensates for faults and maintains grid stability, improving fault resilience in MV distribution networks.