Zero-Vector-Regulation-Based Closed-Loop Power Distribution Strategy for Dual-DC-Port DC–AC Converter-Connected PV–Battery Hybrid Systems

Abstract

The dual-dc-port dc-ac converter-connected photovoltaic (PV)-battery hybrid systems present high-efficiency and low-cost features with single-stage power conversion as PV and battery are connected to the grid directly. However, it is challenging to achieve flexible power distribution in this configuration due to its coupled features in grid-side current tracking and power distribution. To deal with this issue, this paper proposes a zero vector regulation-based closed-loop power distribution strategy for the dual-dc-port dc-ac converter-connected PV-battery hybrid systems. By modeling the dual-dc-port dc-ac converter as an equivalent two-level one, an extra control freedom for power regulation is accessible and a closed-loop power control is adopted for flexible power distribution by zero vector regulation. With the proposed power distribution strategy, the desirable quality of the grid-side current is achieved without complicated voltage vector synthesis, along with good adaptivity to different modes/voltages and flexible power control. Besides, detailed power distribution discussion and analysis with different proportions of zero vector are carried out. Finally, the islanded microgrid experimental tests are conducted to verify its effectiveness and feasibility.