Small-Signal Model and Stability Analysis of DC Microgrids with Master-Slave Control Strategy

As an effective solution for managing the high penetration of renewable energy, DC microgrids have been motivated under the circumstances of increasing energy crisis and environmental problems. This paper focuses on the small-signal stability of DC microgrid with master-slave control strategy. A new small-signal model considering three types of power modules and their control systems is proposed. Small-signal stability of the DC microgrid is then analyzed through eigenvalues of the characteristic matrix, based on Lyapunov first method. Stability simulations in PSCAD and numerical calculations by MATLAB programming are performed to verify the model. To address the influences of both of the initial value and microgrid parameters on the eigenvalues, an iterative method is proposed to calculate the initial value of the operating point required. Accordingly, the impact of distribution cable impedance parameter on DC microgrid stability is discussed. The simulation results in PSCAD confirm that larger distribution cables impedance will slightly increase the stability margin and decrease the oscillation frequency of the microgrid.