A secondary strategy for unbalance consensus in an islanded voltage source converter-based microgrid using cooperative gain control.

• Unbalance load sharing in islanded microgrids using negative sequence power droop. • New consensus-based secondary-level control scheme for cooperative adjustment of droop gains. • Cooperative controller reduces voltage unbalance at sensitive load buses. • Small signal analysis of the consensus dynamics for a converter-based Microgrid. • Simulation model demonstration for a 4-bus microgrid power system. It is common for industrial and commercial microgrids to experience high levels of load unbalance when operating in islanded mode, which degrades the real output power capability of inverters, causes power quality problems, and impacts on the protection regime. Conventional droop control methods are not designed for sharing of unbalance power where multiple inverters are used, and existing proposals for negative sequence power sharing have several practical disadvantages which are identified. This paper proposes a novel secondary scheme for cooperative adjustment of negative sequence droop gains for voltage source converters. The new design provides an option for sharing of unbalance power, while also correcting voltage unbalance at sensitive buses. In contrast to other designs, the scheme proposes hierarchical unbalance control using a fully distributed architecture. It is robust to communication network failure and adapts to impedance changes in the electrical network. A simulation model of the proposed scheme is demonstrated using MATLAB/Simulink for a reference case. [ABSTRACT FROM AUTHOR]