Journals Proceedings

Abstract

Interfacing technique of dc renewable energy sources like photovoltaic (pv) solar generators with ac distribution line employs inverter, producing higher cost and Power Quality (PQ) problems. A standalone pv generator also needs battery support for energy storage. In an earlier paper [1] it was proposed to utilize two zigzag transformers to interface any dc power source with an ac distribution line fed from a delta connected 3-phase supply. Ac and dc power simultaneously flows through the 3-phase line. The return path of dc is through the ground. Existing substation batteries are used as energy storage device and no inverters are required. It has been established earlier that zigzag transformer with the neutral grounded regenerates open phase voltage during 1-pole auto reclosing in distribution feeders [2]. This distribution feeder may supply 3-phase unbalanced and 1-phase load. The presence of dc voltage in the three phase wires along with the ac voltage may create disturbance in the flow of load current. The load may carry not only alternating current but also unwanted direct current. To avoid the dc current flow through the load, it is proposed to connect a separate wire from negative of the substation battery to the negative of the dc renewable energy source.