An uninterruptible power supply (UPS) system operable in an energy saver mode includes: a static bypass switch connected between an input connector and an output connector of the UPS system and being activatable to operate the UPS system in the energy saver mode; a plurality power modules, each of the plurality of power modules being connected between the input connector and the output connector of the UPS system and at least some of the plurality of power modules being controllable for a reactive power compensation; and a controller for controlling one or more of the controllable power modules depending on a data input related to a reactive power compensation. The controller controls one or more of the controllable power modules depending on the data input such that a reactive power flow via the UPS system is adjusted.

A device for controlling a load flow in an alternating-voltage network includes first and second modular series connections of double-pole switching modules interconnected in a parallel circuit to be inserted in series into a phase line of the alternating-voltage network. At least one switching module of each connection has an energy store and semiconductor switches to be switched on and off. The semiconductor switches can be controlled in such a way that a switching module voltage can be generated at terminals of the switching module. The switching module voltage corresponds to a positive or negative storage voltage or a zero voltage. A control apparatus for controlling the switching modules is configured to generate an equalizing current between the modular series connections. A method for controlling a load flow by using the device is also provided.

Transients occur on power transmission lines for unpredictable reasons including breakers opening and closing, load variations, and inputs to the grid from renewable energy sources turning on and off. A recursive technique allows a linear function to be fitted to a non-linear grid dynamic of the power line transients. The technique is adaptive and helps to stabilize an impedance injection unit while it injects correcting impedance into a transmission line for the purpose of achieving power flow control. When applied to many injection units the technique may also help to stabilize the overall grid. The stabilization system using the recursive technique provides real-time monitoring of the associated power line and stabilization with respect to power line transients.

A power flow control unit has one or more impedance injection units. The impedance injection unit has high current drivers and capacitors forming a capacitor bank, and a cooling plate. The cooling plate is thermally coupled to the high current drivers and thermally decoupled from the capacitor bank. Bus bars connect the impedance injection units in series with a power transmission line. The power flow control unit is configurable to inject into the power transmission line a reactive power of at least one MVAr (mega volt-ampere reactive).

An impedance injection unit (IIU) system is coupled to a high-voltage (HV) transmission line. The IIUs are activated in sequences of activation in successive time periods. This injects an impedance waveform onto the HV transmission line. The ordering of IIUs in the sequences of activation is repeatedly changed in successive time periods. This equalizes electrical stress across the IIUs used, leading to overall improvement in IIU system lifetimes.

A device controls a power flow in an AC network and has a series converter with a DC side to connect to a DC link and an AC side to connect to the AC network via a series transformer. The device further has a bridging arrangement between the series transformer and the series converter configured to bridge the series converter. The bridging arrangement contains at least one bridging branch having a switching unit with antiparallel thyristors and a resistance in series with the switching unit. Furthermore, a method of operation operates the device.

A control system of a wind power installation and/or a wind farm is provided. The control system has a plurality of operating modes and has an interface. The interface is configured for providing maximum adjustability of the wind power installation and/or the wind farm in critical power grid situations. The interface is configured to receive a signal of a power grid operator, as a result of which all of the plurality of operating modes are released and made available to the power grid operator.

A system and a method for locally controlling delivery of electrical power along the distribution feeder by measuring certain electricity parameters of a distribution feeder line using a substation phasor measurement unit (PMU) electrically coupled to a substation distribution bus at a first node on the feeder line, and at least one customer site PMU electrically coupled to a low voltage end of a transformer at a customer site, wherein the transformer is coupled by a drop line to a second node on the distribution feeder line and the customer site is coupled by another drop line to the transformer, and by controlling at least one controllable reactive power resource and optionally a real power resource connected to the second node or at the customer site. Related apparatus, systems, articles, and techniques are also described.

A control module controls impedance injection units (IIUs) to form multiple connection configurations in sequence. Each connection configuration has one IIU, or multiple IIUs in series, parallel or combination of series and parallel. The connection configurations of IIUs are coupled to a high-voltage transmission line. The control module and the IIUs generate rectangular impedance injection waveforms. When the waveforms are combined and injected to the high-voltage transmission line, this produces a pseudo-sinusoidal waveform.

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.