An optimized strategy to control DC bus voltage decline for three-phase VSR

In three-phase VSR systems, the decline of DC bus voltage may lead voltage at AC side to saturation, thus AC side current will be distorted and the dynamic response will be undesirable. The paper puts forward an optimized strategy both to improve the control ability of DC bus voltage and at the same time to enhance the dynamic response of the system by absorbing reactive power from the grid or pouring reactive power into the grid based on the analysis of vector relation of three-phase VSR at AC side as well as the influence exerted on the AC side current by the decline of DC bus voltage. Reactive current selective principles as well as corresponding method are also provided. Experimental results indicate that voltage at AC side could be restricted to the linear modulation zone by absorbing reactive power from the grid or pouring reactive power into the grid when the DC bus voltage declines which results in the saturation of voltage at AC side. Moreover, the THD of AC current could be decreased, and the improvement of system dynamic response can be achieved.