Design and implementation of flexible power interfaces for distributed generators

This paper describes a novel design concept of power interfaces connecting distributed generators (DG) to the distribution networks. The proposed power interface is able to perform multiple compensating functions besides regulating the real power fed from DG systems. The hardware structure used in the proposed system is similar to the conventional static synchronous compensator (STATCOM), a converter-based flexible ac transmission systems (FACTS) device; however, its power rating is designed at the distribution level to facilitate the used of pulse width modulation techniques. With the proposed control scheme, the key control functions of distribution STATCOM and active power filters (APF) can be integrated into a single DG hardware system. To demonstrate the feasibility of the proposed control scheme, performances in compensating load current harmonics and the reactive power compensation of the system are investigated. The feasibility and effectiveness of the proposed flexible power interface are verified by simulations and laboratory tests.