Method for switching an operating current
View Patent ↗A method for switching an operating current in a meshed DC voltage network enables operating currents in a DC voltage network to be switched economically in both directions. At least one converter connected to the DC voltage network is controlled in such a way that a zero current is generated in a switching branch having a mechanical switch and the mechanical switch is actuated in accordance with the generated zero current.
1. A method for switching an operating current in a meshed DC voltage network, the method comprising the following steps:
connecting converters to respective AC voltage networks;
connecting the converters together on their DC voltage sides using the meshed DC voltage network;
transmitting electrical power using each converter between the AC voltage network to which it is connected and the DC voltage network;
providing the DC voltage network with a switching branch having a mechanical switch;
regulating at least one of the converters to generate a zero current crossover in the switching branch;
actuating the mechanical switch in dependence on the generated zero current crossover;
causing the zero current crossover by a voltage drop generated at a DC voltage terminal of at least one of the converters;
inducing a first voltage drop by using at least one of the converters and subsequently detecting and evaluating a curve of a switching current flowing in the switching branch; and
then inducing a second voltage drop using the same at least one of the converters having a magnitude determined in dependence on the evaluation of the curve of the switching current.
2. The method according to claim 1 , which further comprises carrying out the step of actuating the mechanical switch before reaching the zero current crossover.
3. The method according to claim 1 , which further comprises:
connecting at least one power semiconductor switch in series with the mechanical switch in the switching branch;
holding the at least one power semiconductor switch in normal operation continuously in its conductive state; and
transferring the at least one power semiconductor switch into its non-conducting blocking state to switch an operating current of the power semiconductor switch.
4. The method according to claim 1 , which further comprises:
detecting a switching current flowing in the switching branch by using measuring sensors; and
carrying out the step of regulating at least one of the converters in dependence on the detected switching current.