Robust Lead-Lag Controller for Distributed Generation in Island Mode

Distributed generations that are connected to the network via a converter, employ dq current control method to control their active and reactive power components in grid-connected mode. In this paper a simple lead-lag control strategy is proposed for a distributed generation (DG) unit in island mode. When it is connected to the utility grid, the DG is controlled by a conventional dq-current control strategy for active and reactive power components. Once the islanding occurs, the dq-current controller is disabled and the proposed controller is used in order to for control of the DG unit operating with its local load. The problem of tuning of controller parameters is converted to an optimization problem with a time-domain objective function which is solved by a genetic algorithm. To achieve a robust performance ITAE criterion is used as objective function. The robustness of controller is proved by zero-pole diagram and frequency domain analysis. Simulations results under different operating conditions verify robustness of controller in comparison with a classical d-q based controller. The results reveal that the proposed control strategy has an excellent capability in achieving good robust performance and greatly enhances the dynamic stability of the system against load parameter uncertainties.