Shut-down control with energy feedback and energy dissipation for MMC-HVDC systems

摘要

This paper presents a complete shut-down control scheme for modular multilevel converter-based highvoltage direct current (MMC-HVDC) transmission systems for scheduled shut-down scenario. The shutdown control scheme is divided into three parts according to the discharge mechanism: the energy feedbackrnstage, the controllable energy dissipation stage, and the uncontrollable energy dissipation stage. To make thernbest use of the sub-module (SM) capacitor energy, the SM capacitor voltage is reduced by modifying thernmodulation strategy in the energy feedback stage. Therefore, some part of the SM capacitor energy canrnbe fed back into the connected alternating current systems. In the controllable energy dissipation stage,rnthe SM capacitor energy is mostly consumed by the direct current line. Lastly, the SM capacitor isrndischarged through the SM internal resistor in the uncontrollable energy dissipation stage. The case studiesrnare performed on a two-terminal 400 MW/±200 kV MMC-HVDC system. From the simulation results, it isrnnoted that the MMC-HVDC system can be rapidly and reliably discharged without any severe over-currentsrnor over-voltages, which proves the feasibility of the proposed control scheme. Copyright © 2015 JohnrnWiley & Sons, Ltd.