Various embodiments of the teachings herein include a grid influencing system for a power supply grid comprising: a current-conducting grid influencing component; and a vacuum circuit breaker including a vacuum circuit breaker tube containing an at least partly integrated pre-arcing device for actively generating an arc between two contacts.

The present invention provides a power control circuit connectable to a load adapted to receive a power supply, the power control circuit adapted to absorb power from the power supply and adapted to deliver power to the power supply to stabilize at least one electrical parameter of the power supply. The present invention also provides an associated method of stabilizing at least one electrical parameter of a power supply connectable to a load, the method including absorbing power from the power supply or delivering power to the power supply. The at least one electrical parameter of the power supply includes parameters such as voltage and frequency.

A method and associated apparatus for feeding electric power from a photovoltaic system via a grid connection point into an AC grid having a low short-circuit power is disclosed. The method includes connecting a DC voltage side of at least one first inverter of the photovoltaic system to a photovoltaic generator and an AC voltage side of the at least one first inverter to the grid connection point, wherein the at least one first inverter is operated as a current source, and connecting an AC voltage side of a second inverter of the photovoltaic system to the grid connection point, wherein the second inverter is operated as a voltage source based on measurement values of an AC voltage measured in the region of the photovoltaic system and a predefined characteristic curve. For a first total short-circuit power of all first inverters operated as a current source, and a second total short-circuit power of the AC grid and of the second inverter operated as a voltage source, a ratio of the second total short-circuit power to the first total short-circuit power is greater than or equal to 2.

An intelligent impedance injection module is for use with transmission lines in a power grid. The intelligent impedance injection module has a plurality of transformer-less impedance injector units and a controller. The controller changes injector gain of the impedance injector units to compensate for current swings in a transmission line.

Methods include, in response to a line frequency variation of a power grid, adjusting a voltage setpoint of a voltage regulator coupled to the power grid at a grid edge to maintain a voltage at the grid edge, wherein the adjusting the regulated voltage setpoint is configured to reduce the line frequency variation to stabilize the line frequency of the power grid. Apparatus include a voltage regulator configured to couple to a power grid at a grid edge and to maintain a voltage at the grid edge, wherein the voltage regulator is further configured to adjust a voltage setpoint of a voltage regulator in response to a line frequency variation of the power grid to reduce the line frequency variation and stabilize the line frequency of the power grid.

There is provided a transformer system (10) for converting a grid voltage (V.sub.grid) to a regulated voltage (V.sub.regulated) and output the regulated voltage (V.sub.regulated) to a power line (30), the transformer system (10) comprising: a first transformer (40) configured to step down the grid voltage (V.sub.grid) to an unregulated voltage (V.sub.unregulated) and provide the unregulated voltage (V.sub.unregulated) at an output of the first transformer (40); a shunt coupling transformer (50) connected in parallel with the output of the first transformer (40) and further connected to power electronics circuitry (60); and a series coupling transformer (70) connected in series with the output of the first transformer (40) and further connected to the power electronics circuitry (60). The power electronics circuitry (60) adds, via the series coupling transformer, a conditioning voltage (V.sub.conditioning) in series to the unregulated voltage (V.sub.unregulated) to generate the regulated voltage (V.sub.regulated). The first transformer, the series coupling transformer and the shunt coupling transformer are housed in a single transformer tank (80), and the power electronics circuitry is housed in a power electronics enclosure (90) separate from the transformer tank. Each of the transformer tank and the power electronics enclosure comprises one or more openings (95) through which electrical connections (97) between the shunt coupling transformer (50), the series coupling transformer (70) and the power electronics circuitry (60) pass.

In the field of high voltage direct current (HVDC) power transmission networks there is a need for an improved power converter. A power converter, for use in a HVDC power transmission network, comprises first and second DC terminals, for connection in use to a DC network and between which extends at least one converter limb. The or each converter limb includes first and second limb portions which are separated by an AC terminal, for connection in use to an AC network. Each limb portion includes a switching valve, and the power converter including a controller programmed to control switching of the switching valves to control the flow of a converter current (I.sub.max) through the power converter and thereby in-use transfer power between the power converter and the AC network. The power transferred between the power converter and the AC network has an active component and a reactive component. The controller is further programmed in use to: (i) prioritize to a first extent the transfer of reactive power between the power converter and the AC network during a first operating condition, when the AC voltage (V) of the AC network lies outside a desired operating range, by allowing up to a first amount of the converter current (I.sub.max) to be a reactive current; and (ii) prioritize to a second extent, less than the first extent, the transfer of reactive power between the power converter and the AC network during a second operating condition, when the AC voltage (V) of the AC network lies within the desired operating range, by limiting the amount of converter current (I.sub.max) that can be a reactive current to a second amount, less than the first amount, the second amount being determined according to a measured operating frequency of the AC network.

Legacy automatic variable capacitor KVAR compensation systems typically use either electromechanical devices such as relays or contactors of various forms and types to switch the selected capacitors in and out of the electrical system under some form of electronic control. These systems are slow and discontinuous in their ability to closely regulate the exact value of compensatory capacitance needed to compensate the variable and rapidly changing reactive power KVAR in the electrical power transmission and distribution networks. The present invention provides a fast response active KVAR compensator based on a variable transimpedance topology.

A flexible alternating current transmission system (FACTS)-based shunt system is described for use in a hierarchy in a high-voltage or medium-voltage power grid. The shunt system includes a FACTS-based shunt device, a communication link, and a shunt controller. A hierarchy in the power grid includes a supervisory utility communicably coupled to localized intelligence centers (LINCs). Each LINC is communicably coupled to one or more impedance injection modules (IIMs) that are coupled to the power grid. The hierarchy has an optimization engine. The shunt controller, of the shunt system, is to communicate and cooperate with one or more of the LINCs in the hierarchy. The shunt controller is to operate the FACTS-based shunt device in accordance with such communication and cooperation with the LINCs, to provide voltage stability to the power grid through hierarchical control according to the supervisory utility, the LINCs and the optimization engine.

The present invention provides a series compensator and a control method. The series compensator includes a series transformer, a series transformer bypass device, a voltage source converter, a high-speed converter bypass device, a high-speed switch, and a reactor. The reactor and the high-speed switch are connected in parallel to form a current limiting module; one winding of the series transformer has two ends connected in series to a line, and the other winding thereof is sequentially connected to the current limiting module and the high-speed converter bypass device; the voltage source converter and the high-speed converter bypass device are connected in parallel; and at least one winding of the series transformer are connected in parallel to at least one series transformer bypass device. The series compensator of the present invention indirectly provides the current limiting module, so as to effectively limit the short-circuit current of a system, reduce the fault current to which the compensator is subjected, and improve the reliability of an alternating current system and the series compensator. Moreover, the current limiting module has a low voltage level, and the high-speed switch has a small breaking current, thereby providing good industrial applicability.