Power flow analysis in stand-alone 4-wire, 4-leg inverter microgrid with unbalanced loads

Three phase 3-leg inverters are the most common interfaces for forming distributed generation and microgrids. However, in low voltage systems, loads are often 3-phase, 4-wire with frequent unbalances. The question of unbalanced loads on stand-alone microgrids can be handled in two ways. First, unbalanced load compensators can be provided near each unbalanced load. Second, unbalanced loads can be fed by 4-leg inverter interfaces via a 4-wire microgrid. This paper is concerned with the second approach. Detailed analysis of power flow dynamics and stability for a 3-phase, 4-wire microgrid with 4-leg inverters catering to unbalanced loads is carried out for the first time. The analysis is supported by simulations and laboratory experiments. The proposed microgrid shows stable operation and maintains balanced voltages at unbalanced load terminals without any load compensators.