Comparative Research on Compensation Controls for a Novel Three-Port Dynamic Voltage Restorer

Abstract

Dynamic voltage restorer (DVR) is an economical compensation device used to support grid voltage. A DC-DC converter is usually inserted to interface the energy storage with wide voltage range. However, the active power flows through two power conversion stages, which significantly reduces the efficiency. To address this issue, a three-port DVR (TPDVR) with dual DC ports is presented in this paper. As for the TPDVR, partial active power can be transferred within only one power conversion stage, thus increasing the efficiency. Compared with pre-sag control and in-phase control, minimum-energy control is always preferred for a DVR because it reduces the amount of active power needed from the DC-link. Nevertheless, once the sag is deep, the compensated voltage amplitude may be higher which claims higher DC-link voltage and the DC-DC converter cannot be avoided. Based on TPDVR, a detailed comparative research of different control strategies has been done. And the research shows that in-phase control is more suitable for TPDVR since it can restore grid voltage without using DC-DC converter over a wider range of sags. The characteristics of different controls for TPDVR are investigated and verified by experimental results.