A Hybrid Control Strategy to Support Voltage in Industrial Active Distribution Networks

Asymmetric voltage sags often occur at the point of common coupling, which connects industrial active distribution networks to the utility grid. Distributed generations face the challenges of riding through and supporting the voltage under the grid faults. In order to tackle these challenges, a hybrid control strategy, combined with the frequency droop with passivity-based switch function, is proposed. By adopting the proposed strategy, the positive/negative sequence active/reactive power is injected to recover the voltage. The novel PBSF is enhanced by including both control components of inverter's output current and output voltage based on the Euler-Lagrange model. The novel frequency droop is applied to achieve the positive/negative sequence active/reactive power injection with a satisfied sharing accuracy among the coordinated operation of parallel connected multiple inverters. Extensive simulation and experimental results have validated the effectiveness of the proposed strategy with an effective dynamic response performance and stability.