CN-122029716-A - DC switching station

Abstract

The present disclosure relates to a dc switchyard configured for a bipolar high voltage dc system, the dc switchyard comprising a common bus bar being an anode, a cathode and a neutral, respectively, a number of sub bus bars of the anode, a number of sub bus bars of the cathode, a number of sub bus bars of the neutral, a number of high speed dc circuit breakers with high current interruption capability, and a number of dc switches with non current interruption capability, wherein each sub bus bar of the anode and the cathode is connected to its respective common bus bar via a respective one of the number of high speed dc circuit breakers, and wherein each sub bus bar of the anode and the cathode is connected to at least one high voltage dc transmission medium via a respective one of the number of dc switches, wherein each high voltage dc transmission medium is further connected to the high voltage dc converter station.

Inventors

• J. Hefner
• A. Abdulrahman
• V. Kanan

Assignees

• 日立能源有限公司

Dates

Publication Date

20260512

Application Date

20241011

Priority Date

20231012

Claims (7)

1. 1. A dc switchyard configured for a bipolar high voltage dc system, the dc switchyard comprising a common bus, a number of sub-buses, a number of high speed dc circuit breakers with high current interruption capability, and a number of dc switches with non-current interruption capability, respectively, of a positive pole, a negative pole and a neutral portion, wherein each sub-bus of a positive pole and a negative pole is connected to its respective common bus via a respective one of the number of high speed dc circuit breakers, and wherein each sub-bus of a positive pole and a negative pole is connected to at least one high voltage dc transmission medium via a respective one of the number of dc switches, wherein each high voltage dc transmission medium is also connected to a high voltage dc converter station.
2. 2. The dc switchyard of claim 1, wherein each sub-bus of the neutral is connected to a common bus of the neutral and to at least one high voltage dc transmission medium via a respective dc switch of the number of dc switches, wherein each hvdc transmission medium is also connected to a hvdc converter.
3. 3. The dc switchyard according to any of the preceding claims, further comprising a ground switch between each sub-bus of the neutral and ground, and a ground switch between the common bus of the neutral and ground, wherein the ground switch is a low speed switch with limited current interruption capability.
4. 4. A dc switchyard according to claim 3, wherein the ground switch comprises a resonant circuit.
5. 5. A dc switchyard according to any of the preceding claims, wherein the dc switch between each sub-bus of positive or negative pole and the respective high voltage dc transmission medium comprises two series connected dc switches and a resistor connected in parallel with one of the series connected dc switches.
6. 6. A dc switchyard according to any of the preceding claims, wherein the high speed dc circuit breaker is a hybrid dc breaker.
7. 7. A dc switchyard according to any of the preceding claims, wherein each common bus is connected via a high-speed dc circuit breaker to a further high-voltage dc transmission medium, which in turn is connected to a corresponding common bus of another dc switchyard.

Description

DC switching station Technical Field The present disclosure relates to a Direct Current (DC) switchyard configured for a bipolar High Voltage Direct Current (HVDC) system. Background The growth of global energy demand and the utilization of renewable energy generation place new demands on future power grid connections. The development of renewable energy sources and the improvement of power supply safety require large-scale integration of offshore and onshore networks, resulting in the transmission of large amounts of power over long distances. HVDC is a more preferred option in transmitting large amounts of power over long distances due to transmission losses and smaller cable sizes for a given power level when compared to conventional HVAC transmission systems. Multi-terminal HVDC systems (MTDC) using Voltage Source Converter (VSC) technology have greater flexibility for large-scale renewable energy integration and power transmission network connection due to their ability to independently power control both active and reactive power, AC voltage support, and black start capability. However, there are significant challenges with respect to protection (including fault protection) of MTDC systems in the event of a fault at the DC side of the network. Hybrid DC circuit breakers have proven useful in MTDC systems due to their low losses and high speed. In particular, they are used in DC switchyards, wherein a terminal (including a VSC, such as a multi-modular converter (MMC)) is connected to two or more HVDC transmission media (such as overhead lines or cables), each HVDC transmission medium having the other terminal connected at its remote end (typically via another DC switchyard). However, there remains a desire to find the most appropriate way to build an MTDC system arranged to avoid DC fault spread so that the fault-free part can remain in operation. Disclosure of Invention The present disclosure seeks to at least partially remedy the problems discussed above. To achieve this, a dc switchyard as defined by the independent claims is provided. Embodiments thereof are provided in the dependent claims. According to aspects of the present disclosure, a DC switchyard configured for a bipolar HVDC system is provided, the DC switchyard comprising a common busbar (common busbar) being respectively a positive pole, a negative pole and a neutral, a number of sub-busbars of the positive pole, a number of sub-busbars of the negative pole, a number of sub-busbars of the neutral, a number of high speed DC circuit breakers with high current interruption capability, and a number of DC switches with non current interruption capability, wherein each sub-busbar of the positive pole and the negative pole is connected to its respective common busbar via a respective high speed DC circuit breaker of the number of high speed DC circuit breakers, and wherein each sub-busbar of the positive pole and the negative pole is connected to at least one HVDC power transmission medium via a respective DC switch of the number of DC switches, wherein each HVDC power transmission medium is also connected to the HVDC converter station. With such an arrangement of busbars, sub-busbars, circuit breakers and switches it is possible to quickly disconnect the faulty part of the system while letting the rest of the system continue to operate and to achieve this with a small number of circuit breakers and switches. Additionally, the DC switchyard may be considered as providing a radial grid of HVDC transmission medium through sub-buses connected to a common bus, which provides flexibility with respect to the number of interconnected converter stations in the radial grid. It should be noted that the term "high-speed DC circuit breaker with large current interruption capability" will be understood by those skilled in the art as a DC circuit breaker that is significantly fast and is capable of breaking a DC current when an operating current or even an extremely high fault current flows through the DC circuit breaker during full operation. Further, the term "DC switch with non-current interruption capability" will be understood by those skilled in the art as a switch that is capable of opening when the current through it is approximately zero (i.e., zero or close to zero). Those circuit breaker and switch terms are common in the art and those skilled in the art are familiar with these terms. From a cost-effective perspective, it is particularly advantageous to be able to use such DC switches with non-current interruption capability instead of high-speed DC circuit breakers with large current interruption capability, when possible. According to an embodiment, each sub-line (sub-bar) of the neutral is connected to a common bus of the neutral and to at least one high voltage direct current transmission medium via a respective DC switch of the number of DC switches, wherein each HVDC transmission medium is also connected to an HVDC converter station. Accordi