Dynamic Nonlinear Droop Control (DNDC): A Novel Primary Control Method for DC Microgrids

A novel primary control method, called dynamic nonlinear droop control (DNDC) is proposed for dc microgrids to achieve voltage regulation and power sharing without communication. The proposed controller is based on nonlinear dynamics <inline-formula><tex-math notation="LaTeX">$\dot{y} = \mu y^{k-1}(1 - y^{k})$</tex-math></inline-formula>, and can be seen as a dc counterpart of dispatchable virtual oscillator control for ac microgrids. During transient events, DNDC shows inertial-like voltage dynamics and thus attenuates sudden voltage changes. In the steady state, DNDC has a nonlinear droop-like behavior with a load-dependent droop gain. Compared to droop control, DNDC achieves better power sharing under heavy load and tighter voltage regulation for all load conditions. DNDC also maintains stability for a wider range of constant power loads compared to droop control. A parameter design procedure is provided to control DNDC transient performance, steady-state performance, and stability margin. Results from hardware-in-the-loop and hardware tests validate the proposed method.