Research on a Three-Phase Energy Mutual-Aid Strategy for a Grid-Connected Inverter Based on Constructed Negative Sequence Current Control

With the increased grid-connected capacity of a single-phase distributed power supply, three-phase power unbalance is more likely to occur in a power grid. Three-phase power unbalance can further lead to three-phase voltage unbalance, which can have adverse effects on power quality and power supply reliability. Therefore, there is a need to build a three-phase power transmission channel to realize power exchanging among phases. In this paper, a novel grid-connected inverter control strategy for three-phase power exchanging is proposed based on constructed negative sequence current control. A completed negative sequence current control loop is added to a conventional three-bridge inverter to realize the decoupling control of three-phase grid current, and then three-phase power exchanging is realized. On this basis, this paper further puts forward a strategy for three-phase power exchanging aimed at three-phase voltage balance. Correspondingly, the three-phase grid current is controlled according to the feedback of the three-phase voltage. Then, three-phase voltage balance is achieved by three-phase power exchanging. The simulation and experimental results show that the proposed strategy is suitable for a three-phase unbalanced power grid, which can realize three-phase power exchanging, and further, can achieve three-phase voltage balance. The proposed strategy can help to improve power quality and supply reliability.