Based on the inertia synchronization control (ISynC) method, the three-phase PWM converter can exhibit damping characteristics on the grid frequency while achieving DC voltage control, attracting attention and application in new energy generation units. Current research on the ISynC of PWM converters mostly focuses on grid-connected power generation scenarios, lacking studies and analysis on its four-quadrant control characteristics and system control parameter design methods. To address this issue, a linearized model of the inertia synchronization PWM converter is established. Frequency domain analytical expressions for DC voltage-phase angle, and reactive power-AC voltage are derived. The design method for key parameters of DC voltage and reactive power control loops is provided. The effectiveness of the design method is verified through simulation and experimentation, the four-quadrant control characteristics and the ability to damp the grid frequency variations are analyzed in parallel.