Abstract:
It provides a control system for LCC of an HVDC system and a control method therefor. The control system includes: a first measurement unit (20) being configured to provide a current magnitude measurement indicative of a magnitude of DC current of the HVDC system; and a controller (21) being configured to increase a first extinction angle at which the controlled LCC operates to a second extinction angle in response to that the current magnitude measurement exceeds a current reference level in order to avoid commutation failure of the controlled LCC. By using the solutions according to the HVDC system with increase of extinction angle of the LCC, it is possible to decrease the probability of commutation failures caused by a rapid rise of the DC current of the HVDC system. The overall AC and DC power system reliability and stability is improved.
Abstract:
A DC grid (100) comprising a plurality of AC/DC converters (105) which are interconnected via DC lines (115) is provided, wherein, in order to limit the effects of a fault in the DC grid, the DC grid is divided into at least two zones (200) by means of at least one current limiter (205) in a manner so that a current limiter is connected in each of the DC line(s) (115z) by which two zones are interconnected. A method of limiting the effects of a fault in a DC grid by dividing the DC grid into at least two zones is also provided.
Abstract:
Embodiments of present disclosure relates to a combined switch device for overvoltage protection. The combined switch device comprises a first branch and a second branch. The first branch includes a semi-controlled device and a first arrester coupled to the semi-controlled device, and configured to flow a current caused by an overvoltage of a DC link. The second branch includes a full-controlled device and coupled in parallel to the first branch, the second branch configured to commutate the current from the first branch to the second branch in response to turning on the full-controlled device. By providing the combined switch device of the present disclosure, the electrical system may be protected from overvoltage with a low cost, a small footprint and a relatively simple controlling complexity.
Abstract:
It provides an HVDC converter system, a method therefor and an HVDC system using the same. The HVDC converter system includes a plurality of VSCs (110,111,120,121) being coupled at their DC sides in series, wherein two terminals of the series connection are configured to be coupled with HVDC network; a plurality of by-pass breakers (112,113,122,123), each being in parallel coupled with the DC side of the corresponding one of the plurality of VSCs (110,111,120,121) and being closed where its corresponding VSC is blocked; and a controller (15), being adapted to control current following through the closed by-pass breaker to reach zero and subsequently control the closed by-pass breaker to open. By controlling the by-pass breaker associated with the VSC to be taken in to reach zero current in the first place and then opening the by-pass breaker and deblocking the VSC, the by-pass breaker can be opened in a reliable way independent of zero-crossing of the by-pass breaker naturally would have generated, otherwise, by using converter system built up of LCCs. Therefore, a blocked VSC of converter system of a converter station for HVDC transmission system can be reliably taken into operation, while the other VSC is still operating.
Abstract:
It provides a power conversion circuit for interfacing an AC grid to an HVDC transmission line in islanding condition, a power system and the method thereof. The power conversion circuit includes: a current source conversion circuit configured to supply a power output from the AC grid to a load through the HVDC transmission line; a voltage source conversion circuit configured to compensate a reactive AC power of the AC grid; a measurement unit configured to provide a voltage magnitude measurement and a voltage frequency measurement indicative of the AC grid voltage magnitude and the AC grid voltage frequency; and a controller configured to control the current source conversion circuit to adjust an active power balance between the AC grid and the load based on a voltage magnitude deviation of the voltage magnitude measurement from a predetermined voltage magnitude command and control the voltage source conversion circuit to adjust a reactive power balance between the AC grid and the load based on a voltage frequency deviation of the voltage frequency measurement from a predetermined voltage frequency command. This makes it possible for reducing the complexity of the control for distributed system and thus increasing the power system stability.
Abstract:
A current-limitation system for limiting a current through an DC connection in case of a fault occurring in a DC grid of which the DC connection forms a part is provided, as well as a method of operating a current-limitation system for limiting a current through an DC connection in case of a fault occurring in a DC grid of which the DC connection forms a part.
Abstract:
A current-limitation system for limiting a current through an DC connection in case of a fault occurring in a DC grid of which the DC connection forms a part is provided, as well as a method of operating a current-limitation system for limiting a current through an DC connection in case of a fault occurring in a DC grid of which the DC connection forms a part.