Abstract: A method, an apparatus and a device for suppressing a first HVDC commutation failure under an AC system fault are provided. The method includes: obtaining a three-phase voltage of a converter bus, and calculating a zero-sequence component amplitude and an ?? component amplitude; calculating a first trigger-angle command for a single-phase fault and a second trigger-angle command for a three-phase fault; selecting a smaller one of the first trigger angle command and the second trigger angle command as a trigger-angle command for an extinction-angle controller; and adjusting a trigger angle of the HVDC transmission system by using the trigger-angle command as an upper limit value for an output of the extinction-angle controller of the HVDC transmission system.

Abstract: A voltage source type direct-current ice melting apparatus, a flexible interconnection system and a control method are provided. The voltage source type direct-current ice melting apparatus includes a starting unit, a modular multi-level converter and a measurement control unit. The flexible interconnection system includes two voltage source type direct-current ice melting apparatuses having the same circuit structure. The measurement control unit acquires set values, that are input by a user, of relevant parameters and then processes the set values, that are input by the user, of the relevant parameters and measured values, measured in real time by the measurement control unit, of the relevant parameters, thereby determining and sending a control signal, so as to control an operating state of the modular multi-level converter in the apparatus or system.

Abstract: A method and a system for determining a direct current (DC) loop impedance are provided. The method includes: establishing an impedance model for a DC loop of a high-voltage direct current (HVDC) system; scanning parameters in the HVDC system based on the impedance model, to obtain a feasible region of each of the parameters; substituting, for each of the parameters, the parameter in the feasible region into a DC loop impedance equation, to obtain an impedance corresponding to the parameter, the DC loop impedance equation being obtained by transforming the impedance model; and comparing, for each of the parameters, the impedance corresponding to the parameter with a target impedance value, and determining the impedance that meets the target impedance value and the parameter corresponding to the impedance as an optimal impedance and an optimal parameter of the DC loop.

Abstract: A method, an apparatus and a device for suppressing a first HVDC commutation failure under an AC system fault are provided. The method includes: obtaining a three-phase voltage of a converter bus, and calculating a zero-sequence component amplitude and an ?? component amplitude; calculating a first trigger-angle command for a single-phase fault and a second trigger-angle command for a three-phase fault selecting a smaller one of the first trigger angle command and the second trigger angle command as a trigger-angle command for an extinction-angle controller; and adjusting a trigger angle of the HVDC transmission system by using the trigger-angle command as an upper limit value for an output of the extinction-angle controller of the HVDC transmission system.

Abstract: A voltage source converter based DC deicer and its control method are provided. The voltage source converter based DC deicer includes a connecting reactor, a modular multilevel voltage source converter based on a full H-bridge submodule, smoothing reactors, deicing disconnectors, a deicing bus, and a deicing AC line. The AC side of the modular multilevel voltage source converter is connected to an AC side bus through the connecting reactor, an isolation disconnector and a breaker. The DC side of the modular multilevel voltage source converter is connected to the deicing AC line through the smoothing reactors, the deicing disconnectors, and the deicing bus.

Abstract: A multi-functional automatic switching circuit for direct current ice melting and a switching method thereof are provided. The automatic switching circuit comprises at least one sub-switching circuit. The sub-switching circuit comprises a six-pulse current converter (R) with no saturable reactor, six reactors (L1a, L1b, L1c, L2a, L2b, and L2c), three three-phase knife switches (Sac1, Sac2, and Sac3), and five single-phase knife switches (SV1, SV2, SV3, SV4, and SV5). The sub-switching circuits in series connection or parallel connection, four direct current side switching knife switches (Sdc1, Sdc2, Sdc3, and Sdc4), an isolation knife switch (K), a breaker (QF) and a control and protection system (CP) may form an automatic switching circuit for six-pulse or twelve-pulse direct current ice melting.

Abstract: A voltage source converter based DC deicer and its control method are provided. The voltage source converter based DC deicer includes a connecting reactor, a modular multilevel voltage source converter based on a full H-bridge submodule, smoothing reactors, deicing disconnectors, a deicing bus, and a deicing AC line. The AC side of the modular multilevel voltage source converter is connected to an AC side bus through the connecting reactor, an isolation disconnector and a breaker. The DC side of the modular multilevel voltage source converter is connected to the deicing AC line through the smoothing reactors, the deicing disconnectors, and the deicing bus.

Abstract: A multi-functional automatic switching circuit for direct current ice melting and a switching method thereof are provided. The automatic switching circuit comprises at least one sub-switching circuit. The sub-switching circuit comprises a six-pulse current converter (R) with no saturable reactor, six reactors (L1a, L1b, L1c, L2a, L2b, and L2c), three three-phase knife switches (Sac1, Sac2, and Sac3), and five single-phase knife switches (SV1, SV2, SV3, SV4, and SV5). The sub-switching circuits in series connection or parallel connection, four direct current side switching knife switches (Sdc1, Sdc2, Sdc3, and Sdc4), an isolation knife switch (K), a breaker (QF) and a control and protection system (CP) may form an automatic switching circuit for six-pulse or twelve-pulse direct current ice melting.