Advanced Voltage Support Control Method in Grid-connected 3-level NPC Converter under Grid Fault Conditions

This paper introduces a control scheme for voltage support in a grid-connected 3-level NPC converter experiencing generalized grid fault conditions. In a grid fault conditions, the grid-connected converter must compensate for reactive power in order to stabilize the voltage in accordance with the grid code. The conventional instantaneous reactive power equation does not fit under unbalanced conditions. Therefore, smooth reactive power compensation may be difficult. In this paper, propose a new control method based on the newly defined reactive power equation. When reactive power is applied in a grid fault conditions, the proposed control method is compared with the conventional control method. It has been verified that the proposed control method has better voltage compensation capability in simulation result.