Abstract: The connection of a distributed generation (DG) unit to a weak power grid is challenging due to stability issues resulted from the uncertainty of system impedance. This paper designs controller to improve the performance of grid-connected current feedback control based on μ method. In order to decouple active and reactive components in control system, a multi-input multi-output model reflecting the interaction between the components of d and q is established. The decoupling requirement, together with steady-state error and overshoot is transformed into the design problem of controller. By employing the μ method, the paper designs a robust feedback controller to meet the all requirements. Simulations show that the controller not only guarantees the robust stability and robustness of the system under the uncertainty of the inductance of the power grid, but also realizes the decoupling of the d and q components of the current.

Key words: weak grid, grid-connected inverter, μ method, decoupling control, robustness