A Control Stage for Parallel-Connected Interlinking Converters in Hybrid AC–DC Microgrids

Abstract

Having two or more interlinking converters connected in parallel in hybrid microgrids has some benefits, like modularity, flexibility, and redundancy. However, the parallelization of the inverters leads to circulating currents that can cause system malfunctions. This work uses a method for suppressing low-frequency circulating currents in interlinking converters by controlling the zero-sequence component of the phase currents, showing that the control structure is valid for interlinking converters. The proposed control scheme has been applied to two parallel interlinking inverters of 5 kW and 2.5 kW, respectively. The interlinking inverters are connected to the grid, and they control the voltage in the DC bus of the hybrid microgrid. To validate the concept, simulation and experimental results are shown.

Keywords

• Circulating currents
• hybrid microgrid
• interlinking converters
• parallel inverters