An Adaptive Phase Locked Oscillator to Improve the Performance of Fault Recovery from Commutation Failure in LCC-Based HVDC Systems

Abstract

An adaptive control of phase lock oscillator (PLO) is proposed to increase the ability of LCC-based HVDC systems to successfully recover from commutation failure, where the dynamic performance during the recovery process is improved. The phase lock oscillator is one of the most important parts of the control system, which is used to trace the phase angle of commutating voltage. However, the PLO with constant parameters cannot provide accurate information under both steady-state operation and large disturbances. In our work, the control parameters of PLO can be adaptively adjusted, following the states of commutating voltage. When the system is operating in a steady state, the PLO selects parameters that exhibit improved small-signal stability, while parameters prioritizing dynamic behaviors with high-tracing accuracy are adopted during large disturbances. Case studies based on simulations in PSCAD/EMTDC and RT-LAB show that the proposed control strategy can improve the performance of fault recovery from CF.