Modified Control Algorithm for Detection and Correction of Incorrect Phase Sequence Connections of Grid-feeding Inverter

Three-phase grid-feeding inverters are widely used to inject active and reactive power into the utility grid. It is important to ensure positive phase sequence of connections because these inverters have specific control structure. Use of phase rotation indicator is a popular method to manually determine the correct phase sequence of connections. This paper proposes a modified control algorithm for three-phase grid-feeding inverters. Using this method, during black-start of the inverter, it can distinguish between correct and incorrect phase sequence connections and automatically modify control structure to ensure the proper functioning. The proposed algorithm consists of two parts: (a) identification of incorrect phase sequence connections and (b) corrections in the control structure. Current controller and switching pulses are not activated during execution of identification algorithm. After the identification of correct/incorrect sequence connections, regular/corrected current controller structure and switching pulses are activated. Simulation and experimental results are presented to establish the effectiveness of the proposed method, showing that inverters can feed power to the utility grid irrespective of correct or incorrect phase sequence connections.