A Novel VSG Control Strategy With Droop Compensation for Improved Oscillation Damping and Guaranteed Steady-State Performance in Microgrids
Erico Gurski, Rôman Kuiava, Gilney Damm
Abstract
The Virtual Synchronous Generator (VSG) is a widely studied control strategy for Grid-Forming (GFM) converters, enabling frequency support by implementing virtual inertia and damping. In GFM converters, the VSG damping coefficient serves a dual purpose: damping the power and frequency oscillations and acting as the droop gain in frequency control. This duality restricts the ability to achieve the desired damping and steady-state performance simultaneously. Existing methods addressed this by adding transient damping loops, which are effective when the droop gain remains constant. However, in islanded microgrids, the droop gain may vary in real-time, possibly leading to poorly damped behavior. To contribute to this matter, this paper proposes a Droop-Compensation VSG control (DC-VSG), which incorporates an improved virtual governor, allowing the damping coefficient to be tuned independently from the steady-state response. A tuning procedure is also developed to enhance oscillation damping and speed up the transient response. With its improved governor and proposed tuning, the DC-VSG maintains adequate performance despite variations in droop gain. The DC-VSG is compared to two existing VSG techniques. Each strategy is tuned to maximize the oscillation damping. The performance of each strategy is assessed through time-domain simulations and eigenanalysis at various operating points and droop gain settings. The DC-VSG consistently outperformed existing strategies across all the investigated scenarios.