Distributed Coordinated Control for Stabilization of Multi-Inverter Power Plant

For a power plant integrated with multiple parallel inverters, the impedance variation of the power grid and the natural plug-and-play property of the inverters bring stability challenges. One of the issues is nonlinear wideband oscillations of the grid current and voltage. This article proposes a distributed coordinated control for the stabilization of the multi-inverter power plant. The passivity-based control (PBC) scheme designs the controller of a single grid-connected inverter from the perspective of energy reshaping, which ensures the stability of the entire system when it is extended to multiple inverters in parallel. A nonlinear observer is proposed to discover the changeable frequency drifting of wideband oscillations so that the PBC scheme can adapt to nonlinear disturbances, such as inverter plug-and-play and fluctuated grid impedance. Moreover, to achieve mutual coordination and distributed control of damping characteristics among multi-inverters to ensure the good dynamic performance of the system, an adaptive dynamic coordination loop based on grid impedance identification is incorporated in the PBC scheme. The Lyapunov stability of the system with the proposed PBC controller is proven in the article. The effectiveness of the proposed scheme is verified by simulation and experimental results.