Improvements in Bidirectional Power-Flow Balancing and Electric Power Quality of a Microgrid with Unbalanced Distributed Generators and Loads by Using Shunt Compensators

Abstract

Improper connections of unbalanced distributed generators (DGs) and loads in a three-phase microgrid cause unbalanced and bidirectional power flow problems. The unbalanced DGs and loads may also aggravate the electric power quality (EPQ), such as voltage regulation, power factor, and unbalanced current and voltage. This increases the difficulty of operation in a microgrid. In this study, a three-phase, delta-connected, shunt-type universal compensator was employed for achieving the bidirectional power-flow balancing and improving the EPQ of a three-phase, distribution-level microgrid with unbalanced DGs and loads. A feedforward compensation scheme was derived for the compensator by using the symmetrical components method. In practical applications, the universal compensator can be implemented as static var compensators (SVCs), static synchronous compensators (STATCOMs), or an additional function of active filters. With the on-line compensation of the proposed compensator, the bidirectional power-flow balancing and EPQ improvement in the microgrid were achieved. A demonstration system was proposed to present the effectiveness of the compensator.

Keywords

• bidirectional power flow
• distributed generator
• electric power quality
• microgrid
• performance index
• shunt compensator