Multi-Stage Damping Control Scheme for VSG-Enabled Inverter-Based Resources to Stabilize Low-Inertia Power Grids

This paper presents the impact of Inverter-Based Resources (IBRs) controlled through the Grid-Forming (GFM) scheme on Low-Frequency Oscillations (LFOs) and power system dynamic behavior. These IBRs are integrated at low-inertia buses, where their effect on stability is critical. The study employs the Virtual Synchronous Generator (VSG) control-based GFM scheme for IBRs. The dynamic interaction between the power system and the active and reactive power control loops of VSG-controlled IBRs has a significant impact on the system’s LFOs. This impact becomes more pronounced as the VSG control loop parameters are increased, particularly the virtual inertia constant <inline-formula><tex-math notation="LaTeX">$(H)$</tex-math><alternatives><mml:math><mml:mrow><mml:mo>(</mml:mo><mml:mi>H</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href="kumar-ieq1-3665981.gif"/></alternatives></inline-formula>, the virtual damping coefficient <inline-formula><tex-math notation="LaTeX">$(D_{p})$</tex-math><alternatives><mml:math><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>D</mml:mi><mml:mi>p</mml:mi></mml:msub><mml:mo>)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href="kumar-ieq2-3665981.gif"/></alternatives></inline-formula>, and the virtual voltage gain coefficient <inline-formula><tex-math notation="LaTeX">$(K_{q})$</tex-math><alternatives><mml:math><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>K</mml:mi><mml:mi>q</mml:mi></mml:msub><mml:mo>)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href="kumar-ieq3-3665981.gif"/></alternatives></inline-formula>. These dynamic interactions can introduce new, weakly damped LFOs, negatively impacting the system’s dynamic behavior. To address this challenge, a Supplementary Damping Control (SDC) scheme is proposed for IBRs. This scheme aims to improve LFO damping and mitigate power oscillations of IBRs. The SDC comprises a multi-stage mixed <inline-formula><tex-math notation="LaTeX">$H_{2}/H_\infty$</tex-math><alternatives><mml:math><mml:mrow><mml:msub><mml:mi>H</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mi>H</mml:mi><mml:mi>∞</mml:mi></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href="kumar-ieq4-3665981.gif"/></alternatives></inline-formula> decentralized damping controller integrated with the IBR’s reactive control loop. The parameter variation uncertainty and explicit modelling of disturbance input have been considered in the design process of this SDC scheme. Further, the robustness of the proposed SDC is validated on the IEEE 39-bus system. The system is tested under various operating conditions, such as load increments, changes in network topology, and integration of renewable sources. Eigenvalue analysis is conducted using MATLAB, while dynamic simulations are performed using the Real-Time Digital Simulator (RTDS). Simulation results confirm that the proposed SDC effectively mitigates system LFOs dynamic behavior.