| Summary: | The separating pole connection (SPC) mode of ultra-high-voltage direct current (UHVDC) can significantly improve the power stability, but when the AC bus of one pole is failed and two receiving systems are near, it may cause subsequent commutation failure. In order to restrain subsequent commutation failure and accelerate system's recovery, an adaptive voltage-dependent current order limiter (VDCOL) control strategy based on granular computing is proposed. According to this VDCOL control strategy, VDCOL, which uses fuzzy rules to separate and granulate a different voltage level, can adjust DC current dynamically in a variety of environments. Also, some modifications on VDCOL characteristics are applied to reduce reactive power consumption during low-voltage situations. Then based on the MATLAB simulation platform, the simulation systems for 800 kV the UHVDC SPC system are built. Finally, the simulation example of the SPC mode with the adaptive VDCOL control strategy showed that this VDCOL control strategy can reduce the risk of subsequent commutation failure and improve the stability of the AC/DC interconnection system.
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