Large-Signal Stability Analysis and Shunt Active Damper Compensation for DC Microgrid with Multiple Constant Power Loads

The various impedances of DC microgrid are easy to cause the deterioration of system stability, especially the influence of the negative incremental resistance characteristic of constant power load (CPL). In this paper, the stability of large-signal disturbances in DC microgrid with multiple constant power loads is studied. The Takagi-Sugeno (T-S) fuzzy model and the Lyapunov stability theorem are used to analyzed the large-signal stability of the system, and the region of asymptotic stability (RAS) and the power boundary of each load are estimated. To enhance the stability of DC microgrid, a shunt active damper is introduced to serve as a virtual passive element by controlling the active damper, which can be set either at the bus-side capacitor or the input-side of CPL or the source converter side. The effect of compensation positions of the active damper in a DC microgrid are analyzed and compared, and as a result the active damper set on the input-side of CPL is more efficient than set on the others. Finally, the effectiveness of the active damper to improve the stability of DC microgrid is verified by simulation.