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 subsystem having multiple configurations is described. The subsystem is three-way configurable: as a transportable configuration, as a deployable configuration, and as a transmission line configuration. The transportable configuration includes a collection of impedance injection modules and at least one bypass module carried on a wheeled vehicle such as a trailer. The deployable configuration is an assembly of the collection of impedance injection modules and at least one bypass module, operable to perform power flow operations. The transmission line configuration includes connection of a deployable configuration to a phase of a high voltage transmission line for performing power flow control. The deployable configuration may be open or closed frame. The deployable configurations may be mounted on one or more wheeled vehicles in a mobile subsystem, or semi-permanently mounted at a ground site.

In an impedance injection module in which multiple converter units are placed in series to realize a high level of impedance injection, switches, preferably vacuum interrupters, are connected to short the input and the output terminals of each individual unit. Unlike the fault-protecting switch across the entire module, these switches at the individual converter unit level serve several purposes, overload and surge protection of a unit, insertion loss minimization of an idle unit when the required impedance injection is small, and electrically removing a defective injection unit from the power flow to increase the overall reliability of the impedance injection module in the face of the failure of one unit or a few units. For more rapid response, particularly in response to faults, the vacuum interrupter at the unit level may be accompanied by an SCR switch in parallel with it.

In an impedance injection module in which multiple converter units are placed in series to realize a high level of impedance injection, switches, preferably vacuum interrupters, are connected to short the input and the output terminals of each individual unit. Unlike the fault-protecting switch across the entire module, these switches at the individual converter unit level serve several purposes, overload and surge protection of a unit, insertion loss minimization of an idle unit when the required impedance injection is small, and electrically removing a defective injection unit from the power flow to increase the overall reliability of the impedance injection module in the face of the failure of one unit or a few units. For more rapid response, particularly in response to faults, the vacuum interrupter at the unit level may be accompanied by an SCR switch in parallel with it.

A method and a device control a voltage of a power grid by use of a reactive power device connected to the power grid. The method includes: determining a change over time of a previous voltage of the power grid, determining a change over time of a reactive power previously output into the power grid by the reactive power device, and subsequently outputting reactive power into the power grid by the reactive power device, which reactive power is determined in dependence on the changes over time.

A method and a device control a voltage of a power grid by use of a reactive power device connected to the power grid. The method includes: determining a change over time of a previous voltage of the power grid, determining a change over time of a reactive power previously output into the power grid by the reactive power device, and subsequently outputting reactive power into the power grid by the reactive power device, which reactive power is determined in dependence on the changes over time.

This invention relates to a method and apparatus for power factor adjustment in a waveguide circuit or a transmission line circuit. In this invention, it is shown that, in a waveguide circuit or a transmission line circuit, the power supplied by the source and the impedance can be adjusted by controlling the amount of the phase change of the signal when it propagates through the (equivalent) transmission line once the medium, the structure, and the load of the waveguide circuit or the transmission line circuit are chosen. It is also shown that, by choosing an appropriate frequency, transmission line, and load, one can achieve the negative power factor of the (equivalent) transmission line circuit, and also make the power delivered from the source be lesser than that consumed at the load.

This invention relates to a method and apparatus for power factor adjustment in a waveguide circuit or a transmission line circuit. In this invention, it is shown that, in a waveguide circuit or a transmission line circuit, the power supplied by the source and the impedance can be adjusted by controlling the amount of the phase change of the signal when it propagates through the (equivalent) transmission line once the medium, the structure, and the load of the waveguide circuit or the transmission line circuit are chosen. It is also shown that, by choosing an appropriate frequency, transmission line, and load, one can achieve the negative power factor of the (equivalent) transmission line circuit, and also make the power delivered from the source be lesser than that consumed at the load.

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.

A modular power flow control system is described for optimizing power flow control in a multi-phase power transmission system. Identical impedance injection modules are arranged in an mn matrix, where m is the number of series-connected modules inserted into each phase (forming a leg of the installed bank of modules), and n is the number of parallel-connected legs per phase. Each impedance injection module in a phase is configurable to collectively insert a pre-determined (controllable) power control waveform into the phase to which it is attached. The modular flow control system is agile with respect to configurability, reconfigurability, maintenance, size, weight, and cost.