CROSS-REFERENCE TO PRIOR APPLICATION

Priority is claimed to British Patent Application No. GB 2009938.8, filed on Jun. 30, 2020, the entire disclosure of which is hereby incorporated by reference herein.

FIELD

The invention relates to an arrangement, which comprises a direct current power network (“DC power network” for short) with a plus pole and a minus pole, two series capacitors, wherein a first outer tap is connected to the plus pole via a first power line, wherein a second outer tap is connected to the minus pole via a second power line and wherein a middle tap is connected to ground. Furthermore, the arrangement comprises a circuit switch arranged in at least one of the first and the second power line and a circuit switch control unit, which is designed to open the circuit switch in case of overcurrent and/or upon manual intervention. Moreover, the invention relates to a circuit breaker, which comprises a first breaker input terminal for connecting a plus pole of a direct current power network and a second breaker input terminal for connecting a minus pole of said direct current power network as well as a first breaker output terminal for connecting a first outer tap of two series capacitors and a second breaker output terminal for connecting a second outer tap of the two series capacitors. A first breaker current path of the circuit breaker connects the first breaker input terminal and the first breaker output terminal, and a second breaker current path of the circuit breaker connects the second breaker input terminal and the second breaker output terminal. Furthermore, the circuit breaker comprises a circuit switch arranged in at least one of the first and the second breaker current paths and a circuit switch control unit, which is designed to open the circuit switch in case of overcurrent and/or upon manual intervention. Finally, the invention relates to a precharging device, which comprises a first precharger input terminal for connecting a plus pole of a direct current power network and a second precharger input terminal for connecting a minus pole of said direct current power network as well as a first precharger output terminal for connecting a first outer tap of two series capacitors and a second precharger output terminal for connecting a second outer tap of the two series capacitors. Furthermore, the precharging device comprises a first precharger current path connecting the first precharger input terminal and the first precharger output terminal and a second precharger current path connecting the second precharger input terminal and the second precharger output terminal.

BACKGROUND

An arrangement, a circuit breaker and a precharging circuit of the kind disclosed hereinbefore is known in principle. The capacitors are used as energy buffers what may cause problems in transition phases between different operating states. In particular, an overcurrent condition in the circuit breaker can be caused, which in turn leads to disconnection from the DC power network. In addition, in prior art, solutions for (floating) DC power networks are missing and more generally solutions, which cover all necessary aspects of connecting capacitors to a DC power network via a circuit breaker.

SUMMARY

In an embodiment, the present invention provides an arrangement, comprising: a direct current power network with a plus pole and a minus pole; two series capacitors, a first outer tap being connected to the plus pole via a first power line, a second outer tap being connected to the minus pole via a second power line and a middle tap is connected to ground; a circuit switch arranged in at least one of the first and the second power line; a circuit switch control unit configured to open the circuit switch upon overcurrent and/or upon manual intervention; a switchable high ohmic path in at least one of the first and the second power line, which bypasses a) a switchable low ohmic path in the least one of the first and the second power line or b) the circuit switch; a load control unit configured to measure a total voltage of the two series capacitors as a measured total voltage and to switch on the high ohmic path and to switch off the low ohmic path in case a) or to switch on the high ohmic path and to switch off the circuit switch in case b) if the measured total voltage is below a first threshold voltage, and to switch on the low ohmic path in case a) or to switch on the circuit switch in case b) if the measured total voltage is equal or above the first threshold voltage or above a higher second threshold voltage, the first threshold voltage and the second threshold voltage being set below a voltage of the direct current power network between the plus pole and minus pole; and a balance control unit configured to measure a capacitor voltage of each of the two series capacitors and detect an imbalance of the capacitor voltages and to individually control currents through the two series capacitors by first current influencing means, a current through a first capacitor of the two series capacitors being higher than a current through a second capacitor of the two series capacitors if the first capacitor voltage of the first capacitor is lower than the second capacitor voltage of the second capacitor and vice versa.

