Abstract: Distributed generations are usually connected to the power grid through inverters, but the traditional current control strategy based on phase-locked loop (PLL) is likely to cause instability under weak grid connection. Therefore, this paper proposes the concept of "compound power synchronized (CPS) inverter", which replaced the traditional PLL with a CPS method. The proposed CPS inverter combined active and reactive power to improve the transient response under weak grid scenario and effectively improved the stability of grid connection. Based on the harmonic linearization method, this paper derives and establishes the sequence impedance model of the CPS inverter, and conducts a theoretical analysis of the mechanism of the synchronization coefficient and steady-state operation point on the stability of the grid-connected inverter system. The impedance analysis results show that the fundamental frequency amplitude of the output impedance of the CPS inverter proposed in this paper is mainly affected by the synchronization coefficient in a wide operation range. An experimental prototype is built at the same time, and the hardware experiment results proves the effectiveness of the CPS method proposed in this paper and the correctness of impedance analysis.