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.

An electric charging system for a vessel, vehicle, or aircraft includes one or more energy storage modules on the vessel, vehicle, or aircraft; a pulse rectifier; a converter; and a voltage control transformer. The one or more energy storage modules are connected to outputs of the pulse rectifier. The voltage control transformer is connected to inputs of the pulse rectifier. The voltage control transformer includes a serial transformer having a plurality of pairs of transformer windings, connected together in series, one winding of each pair being adapted to be connected between the pulse rectifier and an input from an energy source and the other winding is connected to the converter.

An air conditioner is connected to an AC power source. The air conditioner includes an adjustment unit and a control unit. The adjustment unit adjusts apparent power at a power source input terminal of the air conditioner. The control unit controls the adjustment unit, based on information according to a target value of apparent power to be supplied to the AC power source from the air conditioner.

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.

An active filter device includes a power module configured to generate a compensating current to suppress a harmonic current generated from a load device and a controller configured to control the power module. The controller includes a current command calculation unit configured to calculate a compensating current command to suppress the harmonic current, a control variable calculation unit configured to calculate a control variable based on a deviation between the compensating current command and an actual compensating current, a duty cycle calculation unit configured to calculate duty cycle of each of three phases based on the control variable, a duty cycle modulation unit configured to perform two-phase modulation on the duty cycle of each of three phases, and a control signal generation unit configured to, after the two-phase modulation, generate, from the duty cycle of each of three phases, a control signal to drive the power module.

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.

An arrangement for reactive power compensation at an electric energy transmission line includes at least one first reactive power compensation device including a first type of power electronic switches, at least one second reactive power compensation device including a second type of power electronic switches and a transformer having a first secondary coil connected to the first device, a second secondary coil connected to the second device and a primary coil connectable to the electric energy transmission line. The primary coil has more windings than any of the first and second secondary coils.

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.