According to a method of the present invention, a method of operating a wind turbine comprising a power generator, a generator side converter connected to the power generator, a line side converter connected to a power grid through power components, and a DC-link connected between the generator side converter and the line side converter is provided, the method comprising: monitoring the grid voltages on the power grid for overvoltage events; if an overvoltage event is detected, operating the line side converter in an overmodulation range for at least a part of the duration of the overvoltage event.

A method of operating a wind turbine as well as a system suitable therefore

It is described a method for controlling a DC-transmission link (3) for transmitting electric power from a power production unit (3) connected to a AC-DC converter (47) at a first side of the DC-transmission link to a utility grid (5) connected to a DC-AC converter (55) at a second side of the DC-transmission link, the method comprising: obtaining a DC voltage signal (Vdc) indicative of a DC voltage at the DC transmission link; controlling the AC-DC converter such that a AC voltage (V1) at a AC side (40) of the AC-DC converter (47) is adjusted based on the DC voltage signal (Vdc). Further, an apparatus (57) for controlling a DC-transmission link (3) is described.

Method and apparatus for controlling a dc-transmission link

Multi-terminal HVDC systems and control methods therefore are disclosed. Methods for controlling multi-terminal HVDC systems having a plurality of converter stations may include receiving a plurality of measurements from a plurality of measurement units disposed on the HVDC system, identifying from the measurements a disruption within the HVDC system, monitoring the measurements to identify a steady-state disrupted condition for the HVDC system, calculating a new set point for at least one of the plurality of converter stations, which new set point may be based on the steady-state disrupted condition and the measurements, and transmitting the new set point to the at least one of the plurality of converter stations. In some examples, the HVDC systems may include an HVDC grid interconnecting the plurality of converter stations and a controller communicatively linked to the plurality of measurement units and the plurality of converter stations.

Coordinated control of multi-terminal hvdc systems

A method and a device (102) for protecting an electric system (104) against overvoltage occurrences, the electric system (104) being adapted to be subjected to voltages The device (102) comprises a plurality of surge arresters (106, 108) and comprises detection means (112) for detecting overvoltage occurrences in the electric system (104) The surge arresters (106, 108) of said plurality of surge arresters are connected in series, said plurality of surge arresters comprising a first surge (106) arrester which is connectable to ground (110) and a second surge arrester (108) which is connectable to the electric system (104) which is to be protected The device (102) comprises a switching means (116) connected in parallel with at least one surge arrester (106, 108) of said plurality of surge arresters, and the switching means (116) is adapted to be open when no overvoltage occurrence is detected and adapted to close upon overvoltage occurrence detection and short-circuit the surge arrester (106, 108) with which it is connected in parallel An electric system comprising at least one such device (102)

A method and a device for overvoltage protection, and an electric system with such a device

Disclosed is a method of controlling the power input to a HVDC transmission link, which HVDC transmission link is connected to an AC power plant via a first voltage source converter and to AC grid via a second voltage source converter, which method includes using the second voltage source converter to perform voltage control of the HVDC transmission link during a no-fault mode of operation of the grid; monitoring a HVDC transmission link parameter to detect an unbalanced fault; and using the first voltage source converter to regulate the output of the AC power plant on the basis of the monitored HVDC transmission link parameter in the event of an unbalanced fault. Also described are a control module for controlling the power input to a HVDC transmission link; a voltage source converter for a power plant; and a power generation and transmission arrangement.

Method of controlling the power input to a HVDC transmission link

A method and a system to influence the power generation of at least one adjustable speed generator (9) are presented. The system comprises a first voltage source converter (4) connected to a local AC bus (2), where the local AC bus (2) is provided with power by the at least one adjustable speed generator (9), a second voltage source converter (6) connected to an AC grid (8), a DC link (5) connected between the first (4) and the second (6) voltage source converter, and at least one control unit (18) to control the first (4) and the second (6) voltage source converters. The at least one control unit (18) performs the method to control the AC voltage (Vloc) in the local AC bus (2) via the first voltage source converter (4) and to modify a reference value for the AC voltage magnitude (Vloc,ref) of the local AC bus (2) in dependence on the AC voltage magnitude (Vgrid) of the AC grid (8).

Ying Jiang-Häfner

Papers

Method and system to influence the power generation of an adjustable speed generator