Inertia Droop Control and Stability Mechanism Analysis of Energy Storage Systems for DC-Busbar Electric Vehicle Charging Station

Although the photovoltaic (PV) integrated dc-busbar electric vehicle charging station (EVCS) is a promising energy supply form for EVs, its inertialess and poor damping always lead to the potential system instability. In this article, inertia droop control (IDC) strategies are, thus, proposed for a bidirectional dc converter (Bi-C) to improve dynamic stability and provide a high-quality power supply for EVs. Compared with the virtual inertia and damping control (VIDC), the proposed IDC can be implemented by easily modifying conventional droop control, avoiding complex control structures. First, virtual inertia is achieved in the proposed IDC strategies in two ways: 1) dynamic virtual impedance and 2) adaptive droop algorithm. Damping support comes from the redesigned damping term featuring secondary voltage regulation to eliminate the voltage deviation. Then, a feedback analytic method is proposed to comprehend stability mechanisms from multiview, and a double-coordinate-based phasor diagram is developed as its analytical tool to observe the interaction among variables intuitively. Accordingly, IDC’s negative feedback property is revealed, and the impactors of system inertia, stiffness, and dissipation properties are explored. Dynamic performance and small-signal stability analysis are also presented to guide parameter selection and optimize the transient response. Experiment results verify that IDC has similar effects to VIDC while simplifying the control structure.