Impact of DC-Link Voltage Loop on Active Damper Stability

The active damper (AD) is considered to be an effective and feasible solution to address the oscillation issues in the modern power system caused by high penetration of power-electronics-interfaced resources. However, in current literature the impedance modeling of AD, which is widely used to study the stability of AD, neglects the impacts of the DC-link voltage loop, resulting in incomplete impedance model and reducing the accuracy of stability analysis. Hence, this paper proposes an improved impedance model of AD, which enhances the modeling accuracy by including the DC-link voltage loop. The dq-axis coupling impedance method is used in this paper to investigate the coupling effect of phase-locked loop (PLL) and its impacts on the stability of AD. The dq-axis impedance modeling results show that the DC-link voltage loop reshapes the output admittance and expands the active region of AD, which may lead to oscillation issues. The simulation and OPAL-RT-based test results validate the accuracy of the proposed modeling method.