A reactive power optimization method for integrated transmission and distribution networks related to a field of operation and control technology of an electric power system is provided. The reactive power optimization method includes: establishing a reactive power optimization model for a transmission and distribution network consisting of a transmission network and a plurality of distribution networks, in which the reactive power optimization model includes an objective function and a plurality of constraints; performing a second order cone relaxation on a non-convex constraint of a plurality of distribution network constraints of the plurality of constraints; and solving the reactive power optimization model by using a generalized Benders decomposition method so as to control each generator in the transmission network and each generator in the plurality of distribution networks.

A reactive power optimization method for integrated transmission and distribution networks related to a field of operation and control technology of an electric power system is provided. The reactive power optimization method includes: establishing a reactive power optimization model for a transmission and distribution network consisting of a transmission network and a plurality of distribution networks, in which the reactive power optimization model includes an objective function and a plurality of constraints; performing a second order cone relaxation on a non-convex constraint of a plurality of distribution network constraints of the plurality of constraints; and solving the reactive power optimization model by using a generalized Benders decomposition method so as to control each generator in the transmission network and each generator in the plurality of distribution networks.

A multi-mode power supply is described for providing power to an impedance injection unit that is operable to inject reactive power into a power transmission line. The impedance injection unit is configured to operate safely in the presence of switching states of the impedance injection unit, and in the presence of disturbances such as surge currents in the power transmission line, by the multi-mode power supply clamping a potential overvoltage to a safe level. The power supply contains analog and digital circuits and can recover automatically from a surge current in the transmission line, or from a condition of zero line current. Power harvesting may be achieved via a line connected current transformer, via an internal current transformer, via a DC link capacitor, or from combinations of these.

A multi-mode power supply is described for providing power to an impedance injection unit that is operable to inject reactive power into a power transmission line. The impedance injection unit is configured to operate safely in the presence of switching states of the impedance injection unit, and in the presence of disturbances such as surge currents in the power transmission line, by the multi-mode power supply clamping a potential overvoltage to a safe level. The power supply contains analog and digital circuits and can recover automatically from a surge current in the transmission line, or from a condition of zero line current. Power harvesting may be achieved via a line connected current transformer, via an internal current transformer, via a DC link capacitor, or from combinations of these.

Disclosed is a method for reducing the variation in voltage, due to Ferranti effect, using the impedance injection capability of distributed impedance injection modules. The Ferranti effect is an increase in voltage occurring at the receiving end of a long transmission line in comparison to the voltage at the sending end. This effect is more pronounced on longer lies and underground lines when the high-voltage power lines are energized with a very low load, when there is a change from a high load to a very light load, or the load is disconnected from the high-voltage power lines of the power grid. This effect creates a problem for voltage control at the distribution end of the power grid.

This patent discloses an active impedance-injection module for dynamic line balancing of a high-voltage (HV) transmission line. The impedance-injection module comprises a plurality of transformers each having a primary winding in series with a HV transmission line. Each transformer also has secondary windings, each connected to an individual electronic converter. The plurality of secondary windings are electrically isolated from the associated primary winding and extract power from the HV transmission line for operation of the converters and other circuits connected to the secondary windings. The active impedance-injection module is enabled to generate a controlled impedance, inductive or capacitive, to be impressed on the HV transmission line. A plurality of active impedance-injection modules spatially distributed on a HV transmission line are enabled to inject a controlled cumulative impedance on a HV transmission line while limiting the capacity of individual converters to that achievable with practical electronic components.

A switched capacitor bank system including a switched capacitor bank assembly having a switch between a capacitor and a phase line, a first voltage sensor to sense a phase line voltage, and a second voltage sensor to sense a capacitor voltage. The switched capacitor bank system includes a wireless current sensor to sense a current of the phase line and an electronic controller configured to receive a first voltage signal from the first voltage sensor, a second voltage signal from the second voltage sensor, a current signal from the wireless current sensor, determine a phase shift calculation for the voltage of the phase line based on the current signal, determine when the voltage of the phase line is at zero by comparing the first voltage signal, the second voltage signal, and the phase shift calculation, and close the switch when the voltage of the phase line is at zero.

A switched capacitor bank system including a switched capacitor bank assembly having a switch between a capacitor and a phase line, a first voltage sensor to sense a phase line voltage, and a second voltage sensor to sense a capacitor voltage. The switched capacitor bank system includes a wireless current sensor to sense a current of the phase line and an electronic controller configured to receive a first voltage signal from the first voltage sensor, a second voltage signal from the second voltage sensor, a current signal from the wireless current sensor, determine a phase shift calculation for the voltage of the phase line based on the current signal, determine when the voltage of the phase line is at zero by comparing the first voltage signal, the second voltage signal, and the phase shift calculation, and close the switch when the voltage of the phase line is at zero.

A method for detecting high-frequency traveling waves in an electrical system by use of current sensors, the method including arranging association of at least one current detection sensor with at least one conductor in the electrical system, where the at least one conductor is associated with at least one parasitic capacitance; receiving at least one measurement from the at least one current detection sensor, where the at least one measurement is based on flow of stray current through the at least one parasitic capacitance; and detecting, based on the at least one measurement, a traveling wave that corresponds to the stray current, where the flow of the stray current through the at least one parasitic capacitance is based on propagation of the traveling wave through the at least one conductor. Disclosed is also an arrangement for detecting high-frequency traveling waves in an electrical system.