Stability Analysis and Compensation Methods to Improve Stability for DC Microgrid with Constant Power Loads

In order to solve the system instability issue caused by a large number of constant power loads in DC microgrid, two compensation methods, active damping compensation and virtual negative inductor compensation, are introduced to improve the stability of DC microgrid in this paper. The small-signal mathematical model of the DC microgrid can be established by designing the Boost converter with voltage and current double closed-loop and the DC-DC converter, which can be regarded as a constant power load. Based on the principle of system dominant pole distribution, the Lyapunov eigenvalue method is used to estimate the power boundary of the DC microgrid. To improve the system stability, active damping compensation method is adopted directly in the control loop of source, and in contrast, a virtual negative inductor method is adopted on the source converter by droop control method, the principle and realization of two compensation methods are right after studied in detail. The power boundary values obtained before and after different compensation methods are compared. Finally, the effectiveness of the active damping compensation and virtual negative inductor compensation methods to improve the stability of DC microgrid is verified by Matlab/Simulink simulation.