<p>The equivalent impedance of a voltage source converter (VSC) imposes a significant influence on the stability of AC/DC hybrid systems. A positive-damping compensation method, which is equivalent to introducing a feedforward loop, is proposed in this paper. The proposed method aims to compensate for the negative damping region in the VSC DC-side impedance, suppressing the resonance of systems with non-negligible line impedance. The expression for the real component of the VSC DC-side impedance is derived via small-signal modeling and rigorous mathematical analysis. Based on this analytical expression, it is further verified that DC-side resonance arises under both power inflow conditions and power outflow conditions. The impacts of control loop parameters, power flow characteristics, and grid inductance on the formation of negative damping and the occurrence of resonance are theoretically deduced in this paper. Notably, a counterintuitive phenomenon is revealed that under power outflow conditions, the negative damping region expands when the grid inductance and power level decrease. This corresponds to the scenario where the short-circuit ratio (SCR) increases when the AC public grid is regarded as a weak grid. Experimental results under bidirectional power flow conditions further validate the resonance analysis and the effectiveness of the proposed positive-damping compensation method.</p>