MAS-Based Hierarchical Distributed Coordinate Control Strategy of Virtual Power Source Voltage in Low-Voltage Microgrid

To settle reactive power sharing inaccuracy among distributed generations (DGs) associated with mismatched lines impedance, a hierarchical control strategy in the framework of multi-agent system (MAS) is proposed. Replace DG by virtual power source (VPS) in droop control and synchronize VPSs voltages by a hierarchical control. Initially, in primary control, improve line feature by defining virtual impedance value, so that VPSs voltages are roughly consistent. Then, design a VPS voltage evaluation index based on reactive power outputs, whose trigger determines whether secondary control is activated. Finally, in secondary control, consensus protocol is used to strictly synchronize actual VPSs voltages with limited voltages information exchange by the sparse communication network. Therefore, MAS is used to provide an appropriate DGs interaction manner and hierarchical control frame. Each DG is associated with a first-level distributed agent to execute primary control. Coordination part is regarded as secondary-level agents to realize secondary control. Hierarchical control provides double safeguards of VPSs voltages synchronization. To verify the effects of control strategy, simulations are carried out on RTLAB and MATLAB/Simulink.