A control device for an active filter connected in parallel with a load at an installation point with respect to an AC power supply provided in a power system includes a harmonic voltage detector to detect an m-order harmonic voltage (m is an integer not less than two) included in a voltage of the installation point, a phase corrector to correct a phase of the detected m-order harmonic voltage in accordance with whether an m-order harmonic impedance when an AC power supply side is seen from the installation point is capacitive or inductive, a command value generator to generate a first compensation command value for compensating for the m-order harmonic voltage included in the voltage of the installation point based on the m-order harmonic voltage after the correction, and an output controller to control an output of the active filter based on a first compensation command value.

The invention relates to an apparatus for regulating electrical power in an electricity transmission network, the apparatus including: a DC contactor; a transmission network connector including live terminal(s) connected to live connection(s) and a neutral terminal connected to a neutral or earth of the electricity transmission network; switches connected to the DC contactor; electronic controlling devices coupled to the switches and control the switches to independently regulate electrical power on each of the live connection(s) and the neutral connection, the electronic controlling devices receive voltage reading of the live connection(s); calculate average of the voltage reading for the live connection(s); if the average is larger than an upper value, control the switches to reduce voltage on the live connection; if the average is less than a lower value, control the switches to increase voltage supplied on the live connection(s).

A zero-sequence current balancer for a controlling zero-sequence current in a three-phase power system includes a cascade multilevel modular inverter (CMMI) coupled to the three-phase power system, wherein the CMMI has a plurality of modules, each module having a module capacitor, and a real power injector circuit provided between the three-phase power system and the CMMI, wherein the real power injector circuit is structured and configured to cause real power to injected into and/or absorbed from the CMMI to regulate a voltage of one or more of the module capacitors.

A multi-mode uninterruptible power supply (UPS) is provided. The multi-mode UPS includes a first path including a rectifier and an inverter, and a second path in parallel with the first path, wherein the multi-mode UPS is operable in an economy mode in which power flows from a utility to a load through the second path while at least one of the rectifier and the inverter is activated, the at least one of the rectifier and the inverter operable to perform at least one of DC voltage regulation, reactive power compensation, and active damping.

A device is for reactive power compensation in a high-voltage network having a phase conductor. The device has a first high-voltage terminal, which is configured to be connected to the phase conductor. For each first high-voltage terminal, a first and a second core section, which are part of a magnetic circuit, a first high-voltage winding, which encloses the first core section, and a second high-voltage winding are provided. Moreover, the device has a saturation switching branch, which saturates the core sections and has controllable power semiconductor switches. A control unit is used to control the power semiconductor switches. The first and the second high-voltage windings are connected by the high-voltage end to the associated first high-voltage terminal and on the low-voltage side can be connected to one or the saturation switching branch. To be able to be connected in series into the high-voltage network, a second high-voltage terminal is provided.

A zero-sequence current balancer for a controlling zero-sequence current in a three-phase power system includes a cascade multilevel modular inverter (CMMI) coupled to the three-phase power system, wherein the CMMI has a plurality of modules, each module having a module capacitor, and a real power injector circuit provided between the three-phase power system and the CMMI, wherein the real power injector circuit is structured and configured to cause real power to injected into and/or absorbed from the CMMI to regulate a voltage of one or more of the module capacitors.

A system and method to selectively pass and damp oscillations in an electric power grid via a controller of a power electronic device irrespective of the modes of the power oscillations. The system and method includes multiple limiters having dynamic limits that are openable and closeable to control the response of the controller, damping ratio dynamic gain control logic that determines a dynamic gain for a control signal based on the oscillation characteristics of one or more input signals, and pulse counter logic to selectively control at least one of the limiters based on the pulse count of the control signal.

A system of reactive power compensators for a wind farm includes a multi-winding transformer and a plurality of modular reactive power compensators (MVBs). The multi-winding transformer includes a primary winding and a plurality of secondary windings. The primary winding is configured to be coupled to a point of common coupling (POCC) for the wind farm. The plurality of MVBs are each coupled to a corresponding winding of the plurality of secondary windings.

For grid-connected power converter control, a method estimates a d-axis grid voltage from a d-axis reference current modified with a d-axis current and a q-axis current modified with a filter inductive reactance. The method generates a q-axis current error from a direct current (DC) voltage input and a DC bus voltage. The method estimates an observer q-axis grid voltage from a q-axis voltage output. The q-axis grid voltage observer estimates the q-axis grid voltage in a direct/quadrature (dq) reference frame equivalent to an ABC to DQ reference frame transform. The method determines a d-axis voltage output as a function of a d-axis current error and a q-axis current modified with a filter inductive reactance. The method determines a q-axis voltage output as a sum of the q-axis current controller output and the observer q-axis grid voltage.

A measurement device that performs a predetermined measurement task together with a plurality of other measurement devices is provided. This measurement device is provided with a sampling phase generator for generating a sampling phase for instructing a timing of sampling, and a communication unit for communicating with at least one of the plurality of other measurement devices. The communication unit transmits the sampling phase generated by the sampling phase generator to at least one of the plurality of other measurement devices. The sampling phase generator is configured to generate a third sampling phase, using an operation that is based on a generated first sampling phase and a second sampling phase received by the communication unit from at least one of the plurality of other measurement devices.