Inertial-Response Preserved Active Damping of Grid-Forming Voltage-Source Converters Using Fractional-Order Regulators

Emulating a synchronous machine (SM), the grid-forming (GFM) voltage-source converter (VSC) has the capability to contribute inertial response to support the frequency; however, in scenarios with insufficient damping, the SM emulation may lead to significant power oscillations in the active power control (APC). To attenuate power oscillations, numerous modifications have been incorporated into the APC law. The existing APC law modifications may totally alter the inertial response derived from the SM emulation. This alteration inevitably poses difficulties in estimating the equivalent inertia constant which is specified by certain grid codes. To address this challenge, a scheme using the fractional-order regulator has been developed to simultaneously realize a well-damped APC as well as a quantitatively measurable inertial response. The effectiveness of the proposed APC law and the design approach have been validated through both theoretical analyses and experimental results.