A novel low-voltage current-limiting control strategy with improved voltage compensation

Abstract

By optimizing the design of the conventional low-voltage current limiting controller (VDCOL), the continuous commutation failure on the receiving end of the traditional LCC-HVDC transmission system is effectively suppressed. In order to overcome low insensitivity of conventional VDCOL under mild and moderate faults, the dc current deviation value is superimposed into the starting voltage of the VDCOL in the form of a compensation voltage to enhance sensitivity of the VDCOL to the dynamic changes of the dc current during mild and moderate faults. In the face of severe faults, the conventional VDCOL adopts a linear adjustment method with a fixed slope, which is bad for suppressing continuous commutation failure. Aiming at this problem, a nonlinear VDCOL strategy is adopted, which the dc current command and the dc voltage are a nonlinear function relationship with a variable slope with the increasing or decreasing of the dc voltage. In the PSCAD/EMTDC simulation platform, the proposed control strategy is verified using the International Council on Large Electric Systems (CIGRE) standard model. Simulation results reveal that the proposed nonlinear VDCOL strategy with improved voltage compensation method can well suppress continuous commutation failures in the case of single-phase and three-phase short-circuit faults, and it is beneficial to restore dc voltage and transmission power and ensure the normal operation of the HVDC transmission system.

Keywords

• LCC-HVDC
• Commutation failure
• VDCOL
• Nonlinearity
• Voltage compensation