Behaviour of microgrids in the presence of unbalanced loads

In a low voltage distribution network there is the increased likelihood of significant load imbalance between phases. This is undesirable as the resulting voltage imbalance can cause damage to equipment such as motors. This paper presents simulations of the behaviour of a microgrid employing droop type controllers in combination with unbalanced loads, showing that significantly unbalanced voltages can occur in the system. The paper details a controller which addresses this problem by controlling the negative sequence components associated with load imbalance. This concept is then integrated into a droop controller and is shown to significantly reduce voltage imbalance across the load.