The increasing global penetration of renewable energy sources based on power electronic converters has raised significant concerns regarding resonance phenomena and small-signal instabilities, which pose critical threats to power system stability and reliable operation. Recent incidents, including widespread blackouts and equipment failures resulting from harmonic interactions involving inverters in modern power systems, underscore the severity of these issues. A primary cause of such instabilities is the interaction between the grid and the control systems of the power converters.

Recent studies indicate that the impact of inverters on system stability is directly related to the direction of power flow. When operating in rectifier mode, the converter’s AC-side admittance may exhibit non-passive behavior in the low-frequency range. This analysis is particularly relevant when integrating battery energy storage systems into the grid, as the converter operates as a rectifier during the charging process.

This study presents a detailed evaluation of the impact of the dc/dc converter on the small-signal stability analysis of a grid-connected battery storage system. For this end, both the ac/dc and dc/dc converters are modeled in state-space representation, as a set of nonlinear algebraic-differential equations. For the state-space modeling, the CCM (Component Connection Method) is adopted due to its modularity and scalability, which allow large and complex systems to be decomposed into smaller blocks. The nonlinear system is linearized and validated by Electromagnetic Transients (EMT) simulations in the MATLAB/Simulink environment. The linearized model is then used to conduct eigenanalyses for a thorough parametric evaluation of the dc-side control and a large set of operating points. Among the operating points, both the battery charging and discharging are included, as different instability phenomena can arise from each operation mode, in several frequency spectra. Through participation factor, sensitivity, and modal analyses, the influence of each dc/dc control parameter on the resonance frequencies and overall stability is assessed, separately for the charging and discharging scenarios.

The obtained results contribute to the ongoing discussions on the instability and resonance issues in power systems with high insertion of power converters. Among the paper’s results and conclusions, the following points are summarized: the dc-link voltage control, mainly in the battery charging operation mode, can introduce negative damping of oscillations in the low-frequency range; and both the battery dc-side controller and the dc-link control bandwidth may introduce modes with resonance frequencies in the same range as other existing control loops, leading to instability. These points highlight the importance of proper tuning of the dc-side controllers in preventing resonance instability phenomena in modern power systems.