Bidirectional power flow occurs in AC/DC hybrid transmission network. There is a significant difference in system stability between the forward and reverse power flow

that is

the bidirectional power stability difference. In this paper

the bidirectional power stability difference of grid-connected converters in AC/DC hybrid transmission systems is studied. In order to solve the problem of bidirectional power stability difference and improve the system stability

through small-signal modeling of AC-side impedance of power-controlled inverter in d-q frame

the impedance characteristics of forward and reverse power flow are compared

firstly. In addition

combined with the impedance stability criterion

the stability difference of the grid-connected converter system caused by the bidirectional power flow is revealed. Moreover

an impedance optimization control strategy is proposed. Without changing the forward impedance characteristics

the reverse impedance characteristics are optimized and unified. Finally

the effectiveness of the proposed control strategy was verified by the Matlab/Simulink simulation model. The results show that the converter system can maintain a relatively uniform stability characteristic under the bidirectional power flow

and the oscillation problem caused by the change of the power transmission direction can be effectively suppressed at the same time. The research results prove the effectiveness of the proposed strategy.