A power transmission network including a single-phase or multi-phase AC electrical system, a converter including an AC terminal, a point of common coupling, a phase reactance connecting the common coupling to each AC terminal, and a transmission medium to interconnect the common coupling and the electrical system. The network includes a controller to: process the voltage and current at the common coupling to compute a state vector; derive a converter demand by combining the state vector with control parameters, including the capacitance of the power transmission medium presented at the common coupling and the impedance of the phase reactance; and operate the converter according to demand controlling the voltage at each terminal and/or the common coupling to inhibit any perturbation in the converter voltage from a target converter voltage or range resulting from the interaction between the capacitance of the power transmission medium and the impedance of the phase reactance.

A technology that can reduce the influence of variations in the reference potential of each current output device on the operation of multiple current output devices, when using the multiple current output devices to reduce the distortion of the load current, is provided. A plurality of active filters 41 to 43 are configured to reduce distortion of a load current supplied from the AC power supply 10 to the load device 20, based on a detection signal output from the load current sensor 30, the detection signal relating to the distortion of the load current; and the signal transmitting unit 44 configured to cause the plurality of active filters 41 to 43 to acquire a signal relating to the distortion of the load current, to reduce influence due to variation of a standard potential of the plurality of active filters 41 to 43, based on the detection signal output from the load current sensor 30.

A converter circuit is configured to output a first reactive current to a power grid when a voltage value of an output port of the converter circuit decreases from a first working voltage value to a second working voltage value. The drive control circuit is configured to: in a process in which the converter circuit outputs the first reactive current to the power grid, when it is detected that the voltage value of the output port of the converter circuit increases to a third working voltage value and the third working voltage value is greater than or equal to a first recovery voltage value, control the converter circuit to output a second reactive current to the power grid, to recover the voltage value of the output port of the converter circuit to the first working voltage value.

An improved management of an electrical power transmission network is obtained by providing at each of the subscriber premises a load control device which includes a power correction system for applying a capacitive load and/or a switched reactor for voltage correction across the input voltage and a sensing system defined by a pair of meters one at the supply and the second downstream of the voltage correction for detecting variations in power factor. A control system operates to control the power correction system in response to variations detected by the sensing system and to communicate between the load control device and the network control system so as to provide a bi-directional interactive system.

A power conversion device that converts input power into AC power and outputs the converted power, the power conversion device including: an active and reactive output current calculator configured to calculate an active output current value and a reactive output current value based on a detected output current value; an active and reactive output voltage value calculator configured to calculate an active output voltage value and a reactive output voltage value based on a detected output voltage value; a reactive output voltage controller configured to adjust a reactive output voltage target value based on an active output current target value, the active output current value, and the reactive output voltage value; and an active output voltage controller configured to adjust an active output voltage target value based on a reactive output current target value, the reactive output current value, and the active output voltage value.

A distributed energy resource (DER) may store electrical power from an AC circuit and discharge stored electrical power to the AC circuit. A DER may be coupled to the AC circuit via a plug inserted into a receptacle coupled to the AC circuit, and a load device may be plugged into the DER via a receptacle of the DER. The DER may pass AC power from the AC circuit to the load device, and may draw additional power from the AC circuit to charge an energy storage circuit of the DER. The DER may also discharge stored energy into the AC circuit and/or power the load device directly.

A filter apparatus, which includes a feedback active common-mode filter and a feed-forward active common-mode filter, the feedback active common-mode filter includes a common-mode noise detection component and a first filter circuit, and the feed-forward active common-mode filter includes the common-mode noise detection component and a second filter circuit, where the first filter circuit is connected between the common-mode noise detection component and the device, and performs feedback filtering on a first common-mode noise signal, to obtain a second common-mode noise signal; the common-mode noise detection component is connected between the first filter circuit and the second filter circuit, detects the second common-mode noise signal, and provides the second filter circuit with the second common-mode noise signal; and the second filter circuit is connected between an external power source and the common-mode noise detection component, and performs feed-forward filtering on the second common-mode noise signal.

A device includes at least one processor configured to determine a reference quantity based on a difference between a reference output power for a power inverter and an actual output power of the power inverter and cause the power inverter to control its power output based on the reference quantity. The at least one processor may be further configured to, responsive to the power inverter entering current-limiting operation, determine a non-zero power term that represents an additional amount of power that the inverter would have outputted if not current-limited; and determine the reference quantity based further on the non-zero power term.

An assembly has a multilevel converter for outputting reactive power to a power supply network. The multilevel converter contains three module branches arranged in a delta circuit. Each module branch contains a plurality of submodules in an electrical series circuit. Each module branch contains a first group of the submodules and a second group of the submodules. The submodules of the first group each contain a first electrical energy storage unit, a first electronic switching element and a second electronic switching element. The first electronic switching element and the second electronic switching element are arranged so that the first electrical energy storage unit is connected into the series circuit at a first polarity.

A power conversion device includes a conversion circuit, a grid forming control circuit, a grid following control circuit, a modulation circuit, a switching circuit, a phase synchronization processing circuit, an initial value computing circuit, and a synchronization adjusting circuit. When a switching signal instructing switching from grid forming control to grid following control is received, the phase synchronization processing circuit computes a synchronous phase by phase synchronization processing for which an amplitude of a grid voltage is used as input. The initial value computing circuit computes an initial amplitude command value based on the amplitude of the grid voltage and the synchronous phase. The synchronization adjusting circuit sets the initial amplitude command value to be an initial value of a command value of an amplitude of an output voltage in the grid following control after switching from the grid forming control.