【目的】交流微网背靠背直流互联变流器在功率双向传输时，交、直流两侧存在明显的功率稳定性差异，这可能导致系统稳定性降低，并易导致系统失稳。【方法】通过小信号建模分析了各端口阻抗的特性，结合阻抗表达式和奈奎斯特稳定性判据，对比分析了系统交、直流侧双向功率稳定性。针对传统控制下存在的负阻抗及双向功率稳定性差异问题，提出了一种端口阻抗协同优化控制策略，同时优化系统内三个端口的阻抗。针对交流侧负阻抗,引入电压功率协同调节机制，通过多变量动态耦合作用实现等效阻抗特性的自适应矫正。【结果】搭建了Matlab/Simulink仿真模型和低功率原型样机试验平台。仿真和试验结果表明,所提优化控制不仅将系统交、直流双侧的负阻抗均优化为正阻抗，还将直流侧阻抗间相位差降低至零，大大提高系统的稳定裕度，增强系统双向功率稳定性。【结论】所提端口阻抗协同优化控制策略能有效解决背靠背变流器系统双向功率稳定性差异问题。

[Objective] AC microgrid back-to-back DC interconnect converters have significant power stability differences between the AC and DC sides in bidirectional power transmission, which may lead to a decrease in system stability and easily cause system instability. [Methods] The impedance characteristics of each port were analyzed through small signal modeling, and the bidirectional power stability of the AC and DC sides of the system was compared and analyzed by combining impedance expressions and Nyquist stability criteria. Aiming at the problems of negative impedance and bidirectional power stability differences under the traditional control, a port impedance coordinated optimization control strategy was proposed to simultaneously optimize the impedance of the three ports in the system. A voltage-power cooperative adjustment mechanism was introduced for the negative impedance on the AC side to achieve adaptive correction of the equivalent impedance characteristics through multivariate dynamic coupling. [Results] A Matlab/Simulink simulation model and a low-power prototype experimental platform were constructed, the simulation and experimental results showed that the proposed optimization control not only optimized the negative impedance of both the AC and DC sides of the system to the positive impedance, but also reduced the phase difference between the impedances on the DC side to zero, which greatly improved the stability margin of the system and enhanced the system bidirectional power stability. [Conclusion] The proposed port impedance coordinated optimization control strategy can effectively solve the problem of bidirectional power stability differences in back-to-back converter systems.

河北省自然科学基金(E2022502032); 国家自然科学基金(51707067)