A method for controlling a wind farm to damp low-frequency electrical oscillations, in particular subsynchronous resonances, in an electrical supply grid having a grid voltage with a nominal grid frequency is provided. The wind farm comprises at least one wind turbine connected to the electrical supply grid. The method includes sensing at least one low-frequency electrical oscillation of the electrical supply grid; determining an oscillation characteristic of each of the at least one sensed oscillation, the oscillation characteristic describing at least one property of the sensed oscillation; specifying an active-power damping signal and/or a reactive-power damping signal for damping the at least one low-frequency oscillation; feeding in an active power component in accordance with the active-power damping signal or a reactive power component in accordance with the reactive-power damping signal, the active-power damping signal and the reactive-power damping signal being specified in dependence on the determined oscillation characteristic.

A method for controlling a wind farm to damp low-frequency electrical oscillations, in particular subsynchronous resonances, in an electrical supply grid having a grid voltage with a nominal grid frequency is provided. The wind farm comprises at least one wind turbine connected to the electrical supply grid. The method includes sensing at least one low-frequency electrical oscillation of the electrical supply grid; determining an oscillation characteristic of each of the at least one sensed oscillation, the oscillation characteristic describing at least one property of the sensed oscillation; specifying an active-power damping signal and/or a reactive-power damping signal for damping the at least one low-frequency oscillation; feeding in an active power component in accordance with the active-power damping signal or a reactive power component in accordance with the reactive-power damping signal, the active-power damping signal and the reactive-power damping signal being specified in dependence on the determined oscillation characteristic.

A method for generating an inductive reactive power for a public grid by an electrical load apparatus, in which, in a first operating mode of the electrical load apparatus, an alternating current of the public grid is transformed by a transformer device and the transformed alternating current is provided for an electrical load of the electrical load apparatus. In a second operating mode of the electrical load apparatus that is different from the first operating mode, the transformer device is short-circuited in a phase-controlled manner by a switching device of the electrical load apparatus, wherein the switching device is phase-controlled such that, depending on a phase angle of the phase control of the switching device by the transformed alternating current, the inductive reactive power for the public grid is generated by the switching device.

A method for generating an inductive reactive power for a public grid by an electrical load apparatus, in which, in a first operating mode of the electrical load apparatus, an alternating current of the public grid is transformed by a transformer device and the transformed alternating current is provided for an electrical load of the electrical load apparatus. In a second operating mode of the electrical load apparatus that is different from the first operating mode, the transformer device is short-circuited in a phase-controlled manner by a switching device of the electrical load apparatus, wherein the switching device is phase-controlled such that, depending on a phase angle of the phase control of the switching device by the transformed alternating current, the inductive reactive power for the public grid is generated by the switching device.

A method for determining when a connection of a power system to a grid has been disconnected. The method includes the power system supplying a first amount of reactive power to the grid to which the power system is connected, and the power system determining if there is a frequency change within the grid. This includes if the frequency change does not exceed a predetermined threshold, the power system supplying a second amount of reactive power to the grid, and if the frequency exceeds a predetermined threshold, the power system supplying a first amount of reactive power to the grid.

A method for determining when a connection of a power system to a grid has been disconnected. The method includes the power system supplying a first amount of reactive power to the grid to which the power system is connected, and the power system determining if there is a frequency change within the grid. This includes if the frequency change does not exceed a predetermined threshold, the power system supplying a second amount of reactive power to the grid, and if the frequency exceeds a predetermined threshold, the power system supplying a first amount of reactive power to the grid.

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.

Systems and methods herein automate detection of switched-capacitor bank operation on a power grid. At least one power line sensor (106) may be positioned on a power line to measure electric field strength and current. A processor may be in communication with the power line sensor and memory storing a capacitor bank analyzer as computer readable instructions that, when executed by the processor, control the processor to: receive electric field data and current data from the power line sensor. The processor may extract key characteristics from the electric field data and the current data, compare the key characteristics to a library of key characteristics of a predictive model, and output, based on the predictive model, a label indicating presence of, or lack of, a capacitor switching event. E-field and current data from multiple line sensors may be aggregated to provide additional insight to capacitor bank operation.

Systems and methods herein automate detection of switched-capacitor bank operation on a power grid. At least one power line sensor (106) may be positioned on a power line to measure electric field strength and current. A processor may be in communication with the power line sensor and memory storing a capacitor bank analyzer as computer readable instructions that, when executed by the processor, control the processor to: receive electric field data and current data from the power line sensor. The processor may extract key characteristics from the electric field data and the current data, compare the key characteristics to a library of key characteristics of a predictive model, and output, based on the predictive model, a label indicating presence of, or lack of, a capacitor switching event. E-field and current data from multiple line sensors may be aggregated to provide additional insight to capacitor bank operation.

A method and an apparatus are presented which enable the identification of a capacitor fault in a given string of a capacitor bank, based on the computation of the string impedance by measuring the string AC current and voltages, where each string includes a plurality of capacitor elements connected in series. The method consists of measuring the string capacitive impedance and comparing this value with a previously measured capacitive impedance of the same string. If a difference between these two values is obtained, which exceeds a given threshold for a certain duration, a fault is recorded.