A port-Hamiltonian approach to secondary voltage control of microgrids

This paper presents a secondary voltage control scheme for microgrids based on the port-Hamiltonian modeling framework. The proposed secondary controller compensates the deviations of voltage amplitudes from their nominal values using the concept of energy shaping, which is the essence of passivity-based control in port-Hamiltonian systems. We shape the energy function and define a new Hamiltonian function such that the new potential energy function has a strict local minimum at the desired equilibrium point. Next, a feedback control is designed such that the closed-loop system preserves the port-Hamiltonian structure. The Hamiltonian in this case is the sum of the plant and the controllers energy functions. The stability analysis is performed and sufficient conditions on the controller gains to achieve voltage regulation are derived. The effectiveness of the proposed control methodology is evaluated using simulation for a benchmark microgrid system.