A calculation for the compensation voltages in dynamic voltage restorers by use of PQR power theory

This paper discusses how to calculate the compensation voltages in dynamic voltage restorers (DVR) by use of PQR power theory. Directly sensed three-phase voltages are transformed to p-q-r coordinates without time delay, then the reference voltages in p-q-r coordinates have very simple form: dc values. The controller in p-q-r coordinates is very simple and clear, has better steady state and dynamic performance than conventional controllers. The controlled variables in p-q-r coordinates are then inversely transformed to the original a-b-c coordinates instantaneously, generating reference compensation voltages to a DVR. The control algorithm can be used for various kinds of series compensators such as dynamic voltage restorers (DVR), series active filters (SAP), synchronous static series compensators (SSSC), and bootstrap variable inductances (BVI). The control algorithm was applied to an experimental DVR system. The experimental results verified the performance of the proposed control algorithm.