One circuit includes first and second primary terminals for connection to first and second power transmission lines and a current transmission path extending between the primary terminals and having current transmission path portions separated by a third primary terminal. A first current transmission path portion includes at least one primary switching element connected in series between the first and third primary terminals, the second current transmission path portion includes an energy conversion block connected between the second and third primary terminals, and the energy conversion block includes at least one primary energy conversion element for removing energy from the power transmission lines. The control circuit further includes a converter limb connected across the second and third primary terminals that includes an auxiliary converter. The control circuit further includes a control unit which controls the auxiliary converter to selectively provide a voltage source.

A method of controlling a modular multilevel converter, MMC, of a full-bridge or mixed arm type in case of a DC line disturbance is provided. The method includes determining whether a magnitude of a DC voltage (Udp) of the MMC has fallen below an upper voltage threshold (Ud_max_lim), and, if determining that the magnitude of the DC voltage has fallen below the upper voltage threshold, reducing both a magnitude of an AC active current reference (IVD_ORD) and a magnitude of a DC voltage reference (UDC_REF) for the MMC based on the DC pole voltage. An MMC with a controller implementing the method, a converter station including at least one such MMC, and a power transfer system including at least one such converter station, are also provided.

A changeover method of a high voltage direct current (HVDC) transmission system is provided. A first system is set to an active state. A ready signal is transmitted from the first system to a first COL. A ready detection signal and an active signal are transmitted to the first system, in response to the ready signal. A confirm signal is transmitted to the first system in response to the active signal when the ready detection signal matches the ready signal.

Disclosed is an HVAC control device for controlling a vehicle climate control sys-tem having a plurality of control elements. The HVAC control device includes a housing having a common size dimensioned for installing in a complementary receptacle in the vehicle climate control panel, the size common to replacement vehicle climate control panels for vehicles made by one than on vehicle manufacturer. On the front surface of the housing is a user interface by which a user can operate the vehicle climate control system. In the housing is a controller adapted to control more than one different vehicle climate control system.

A system includes at least one pair of series adaptive clamps (SACs). Each SAC is configured to connect to a single conductor that is configured to conduct a constant current between shore-side power sources on opposite ends of the single conductor. Each SAC is configured to clamp a specified amount of power from the single conductor. Each SAC is configured to connect to one end of two ends of a power transfer bus, wherein the other end of the power transfer bus is connected to another SAC of a same pair of SACs. Each SAC is configured to provide a constant voltage to the power transfer bus at the constant current in order to supply at least some of the specified amount of power to a load connected to the power transfer bus.

Provided are a commutation control method and a commutation control apparatus. The method includes: detecting whether transient disturbance in a DC transmission system satisfies a disturbance criterion condition; when the transient disturbance satisfies the disturbance criterion condition, determining a maximum trigger delay angle used in a commutation operation performed by a current converter on an inverter side of the DC transmission system, the determined maximum trigger delay angle being smaller than a maximum trigger delay angle used before the transient disturbance; and controlling the current converter on the inverter side of the DC transmission system to perform the commutation operation based on the determined maximum trigger delay angle.

Disclosed herein is a redundant control system. The redundant control system includes a clock generation unit for generating clocks at preset periods; a first buffer for storing control data output from a first controller; a second buffer for storing control data output from a second controller; first and second state monitors for checking whether pieces of control data of the first and second controllers, stored in the first and second buffers, respectively, are present during an identical clock period among the clocks provided by the clock generation unit; a switching unit for performing switching so that any one of the pieces of control data of the first and second controllers, stored in the first and second buffers, is transmitted to lower modules; and a control unit for determining whether a fault occurs in each of the first and second controllers, based on results that are obtained by checking whether the pieces of control data of the first and second controllers are present and that are output from the first and second state monitors, and controlling the switching unit based on results of the determination.

Disclosed are a voltage source converter based high voltage direct current (VSC-HVDC) high-frequency resonance suppression method, system, and device. The method includes: when an effective value of an actually input alternating current (AC) voltage is reduced from a normal value to meet a preset condition, making the virtual electrical quantity completely equal to the actual electrical quantity, and performing full real-time tracking for the actual electrical quantity to improve dynamic characteristics of a power system at the moment of a fault; and after performing the full tracking for a period of time, if the effective value of the actual AC voltage is less than a preset threshold, performing adaptive tracking until the actual electrical quantity recovers to a stable value. The present disclosure can reduce a risk of high-frequency resonance of a VSC-HVDC, avoid deteriorating dynamic characteristics of the VSC-HVDC, and improve safety of fault ride-through of the VSC-HVDC.

The present invention discloses a fiducial node DC voltage based DC voltage droop control method with dead-band for HVDC grids. Two levels of DC voltage control e.g. primary and secondary DC voltage regulation are introduced to realize load sharing and DC voltage control in HVDC grids. In the process of primary DC voltage regulation, the power flow regulation ability of the entire HVDC grids can be significantly improved, and the DC voltage and stability of the HVDC grids will be quickly controlled and guaranteed for the benefit of droop characteristic. Secondary DC voltage regulation is achieved by by introducing the load-DC voltage controller. In the process of secondary DC voltage regulation, the burden of accommodating power imbalance by the DC voltage fiducial node will be alleviated, thus improving the ability to resist disturbances of the entire HVDC grids.

A method of operating a thyristor-based line-commutated multi-phase power converter on a multi-phase AC voltage connection point, which is supplied by an AC voltage network. Between the AC voltage connection point and an AC voltage connection of the power converter, a series circuit of modules is arranged for each phase. Each of the series circuits has a first electronic switching element, a second electronic switching element, and an electric energy storage device. The voltages of the phases of the AC voltage connection point are measured and, if an undervoltage is detected on a phase of the AC voltage connection point, an additional voltage adding to the voltage of that phase is generated by way of the series circuit of modules allocated to that phase in such a way that the voltage of that phase is increased, at least temporarily.