Maximum Virtual Inertia From DC-Link Capacitors Considering System Stability at Voltage Control Timescale

In power electronics-dominant systems (PEDSs), the declining-inertia issue is one of the most significant challenges to tackle. The inertia emulation from DC-link capacitors is one cost-effective and application-friendly solution to enhance the system inertia. Although the virtual inertia control of the DC-link capacitor supports the grid frequency with a relatively long-term effect, it affects the dynamic of the power converter at multiple timescales. In turn, the maximum effective virtual inertia from the DC-link capacitor is limited by the operation condition of the converter. Thus, to properly design the virtual inertia control, the dynamics of the faster timescale than the inertia emulation should be addressed. With the above, this article analyzes the maximum virtual inertia of DC-link capacitors based on a multi-timescale model of power converters. First, the system stability considering virtual inertia control of DC-link capacitors is analyzed in the submodel at the voltage control timescale (VCT), where the virtual inertia control parameters are accordingly tuned on a pre-designed converter. Then, the maximum effective virtual inertia is identified in the submodel at the rotor motion timescale (RMT). The exploration and findings in this article are beneficial to the power converter design and future inertia placement optimization in PEDSs. Case studies on a hardware-in-the-loop platform are conducted to validate the proposed model and the analysis method.