Optimal control strategy for VSC-based systems under unbalanced network conditions

Abstract

This study presents an optimization control strategy to improve the ride-through capability of voltage source converter-based high voltage direct current (VSC-HVDC) systems under unbalanced network conditions. To facilitate simple implementation and flexible operation, the current references are derived and synthesized into one generalized equation that introduces two individually adaptable parameters. The two parameters can be adapted to eliminate the oscillations of instantaneous active and reactive power, as well as the currents at the grid side under unbalanced network conditions. The optimal parameters model of VSC-HVDC is established aiming to minimize integrated fluctuation amplitude of the active and reactive power while the restriction of output current harmonic distortion is taken into account. Through the optimization method based on particle swarm optimization algorithm, the parameters can be determined. The simulation is conducted with PSCAD/EMTDC. The results show that the proposed strategy is effective and feasible.