Virtual synchronous control is widely studied in port shore power sources to enhance system inertia and damping, but there may be control interaction between the port shore power source and the ship PWM rectifier load. Thus, firstly, according to the multi-time scale control characteristics, a frequency-division dq-frame impe- dance model of the port shore power source with virtual synchronous control is proposed. Secondly, the stability analyses based on the established dq-frame impedance and generalized Nyquist stability criterion show that there is a control interaction between the AC voltage loop of port shore power source and the DC voltage loop of ship PWM rectifier load, inducing the system oscillation. Increasing the AC voltage proportional and resonance gain of port shore power source or reducing the DC voltage proportional gain of ship PWM rectifier load can enhance the stability of the port shore power supply system. Finally, the effectiveness of the impedance model and stability analysis results are verified by the experimental results based on the hardware in the loop experimental platform.