Inverter coupling evaluation and decoupling method based on dynamic relative gain

The output active power and reactive power of new energy inverter can be controlled independently using vector control, but there are degrees of coupling between them under the influence of transmission line parameters. In this setting, an overall evaluation of the coupling degree of power is vital to achieve decoupling control. This paper indicates the root cause of inverter power coupling and necessity of decoupling them. Here a quantitative method to evaluate inverter power coupling degree in full frequency-domain is proposed by applying dynamic relative gain method. The new scheme is different from traditional relative gain method, which can evaluate power coupling degree completely and accurately. Advantage of this evaluation scheme is established through a case study. Droop control scheme obtained from calculating result are shown to be consistent with that derived analytically. A power decoupling control method based on diagonal matrix is then applied to eliminate the coupling. Finally, a model is designed in MATLAB/SIMULINK. Results for both island mode and parallel mode show good decoupling performance.