A distribution feeder of an electricity grid comprises a substation and a plurality of nodes with at least one controllable reactive power resource. A method is provided for locally controlling delivery of electrical power along the distribution feeder, wherein for a feeder segment in the distribution feeder the method comprises: obtaining an actual voltage magnitude at an upstream node and at a downstream node of the feeder segment, and a real power value at the upstream node; setting a target voltage phasor at the downstream node as a value when a power flow across the feeder segment is maintained, and when equal reactive power is injected at the upstream and downstream nodes that consumes all the reactive power in the feeder segment; and adjusting operation of the at least one controllable reactive power resource so that the actual voltage magnitude at the downstream node moves towards a target voltage magnitude of the target voltage phasor.

A control unit for an active filter for reducing resonance in an electric system is provided. The electric system comprises a power source distributing an alternating current to an AC conductor connected to a power consuming unit for distributing the AC to the power consuming unit. The active filter comprises a DC power source and a DC conductor connecting the DC power source to the AC conductor. The control unit comprises: a voltage measurement unit adapter to create a voltage signal on the basis of a measured voltage; a computing unit adapted to compute, using a biquadratic filter, a first compensating current on the basis of the voltage signal for reducing resonance in the electric system and a switching system placed between the DC power source and the DC conductor for creating the calculated first compensating current.

The invention provides a method and system for operating an inverter based distributed power generation source with energy storage system, as a Flexible AC Transmission System (FACTS) device—a STATCOM. The inverter based distributed power generation source can provide reactive power compensation, voltage regulation, damping enhancement, stability improvement and other benefits provided by FACTS devices. These STATCOM functions are provided when the said energy storage based distributed power generation source is doing at least one of: i) not exchanging active power with said power grid system, or ii) exchanging active power less than a maximum inverter capacity with said power grid system. The present invention thus provides a technological improvement that opens up a new set of applications and potential revenue earning opportunities for energy storage based distributed power generation sources other than simply from exchanging (injecting or absorbing) active power.

Aspects of the disclosure include a power system comprising at least one three-wire active harmonic filter (AHF) configured to be coupled to, and provide compensation current to, a three-phase load, at least one four-wire AHF configured to be coupled to, and provide compensation current to, the three-phase load, and a controller configured to determine a total compensation current to provide to the three-phase load, the total compensation current including a zero component and a non-zero component, determine an output capacity of the at least one three-wire AHF and the at least one four-wire AHF, calculate a current-compensation ratio based on the output capacity of the at least one three-wire AHF and the at least one four-wire AHF, and control the at least one four-wire AHF to provide at least a portion of the non-zero component of the total compensation current to the three-phase load based on the current-compensation ratio.

Techniques are described for testing whether an end effector, or component thereof, is correctly or incorrectly installed to a manipulation system. In an example, a manipulation system can include a manipulator arm configured to receive an end effector having a first moveable jaw, a transducer configured to provide first effort information of the end effector as the end effector moves, and a processor configured to provide a command signal to effect a first test move of the first moveable jaw, and to provide an installation status of the of the end effector using the first effort information of the first test move.

Methods and systems for a synchronverter power control during unbalanced grid conditions is disclosed. The system includes a synchronverter coupled with a power supply grid, a power reference generator, configured to receive a terminal voltage measurement vector v.sub.t and a current measurement vector i from the synchronverter, and generate an active power P.sub.f and a reactive power Q.sub.f, a synchronverter control unit connected to the power reference generator and configured to process the active power P.sub.f and the reactive power Q.sub.f and generate an electromotive force (EMF) vector e, and an active and reactive power control unit, connected between the synchronverter control unit and the synchronverter, configured to receive the electromotive force (EMF) vector e and the terminal voltage measurement vector v.sub.t, and regulate the current measurement vector i to eliminate power oscillations and current harmonics in the synchronverter during unbalanced grid conditions.

A power converter controller for virtual impedance realization is provided that comprises: a sampling circuit configured to sample a real grid interface voltage at terminals of the power converter; a first operation block, which may be a subtractor, for performing a first operation on a reference voltage signal and the sampled real grid interface voltage signal of the power converter to generate a first voltage signal; a second operation block that may consist of a divider for dividing the first voltage signal by an amplification factor to generate a second voltage signal; and third operation block, which may be an adder, for adding the sampled real grid interface voltage signal to the second voltage signal, and a third voltage signal to generate a command voltage signal for realization at the DC-to-AC voltage conversion output, wherein the amplification factor is a real number greater than or equal to 1.

A method operates an arrangement having a DC transmission link or a DC transmission grid to which at least two converters each having an AC voltage side and a DC voltage side are connected. A grid stabilization device is connected to the AC voltage side of one of the converters, subsequently referred to as near converter. The grid stabilization device has for the purpose of grid stabilization an energy store for the buffer storage of energy and/or an energy consumer for the consumption of electrical energy, and the grid stabilization device is isolated on the grid side from at least one other of the at least two converters, subsequently referred to as a remote converter, by way of the near converter. The grid stabilization device is actuated by at least one control signal that is produced and transmitted to the grid stabilization device by the near or the remote converter.

A method and apparatus include a primary transformer coil, a secondary transformer coil, and a center tapped inductor coupled to the secondary transformer coil. A first switch may be in electrical communication with the center tapped inductor and may be configured to affect the first output voltage. A second switch may be in electrical communication with the center tapped inductor and may be configured to affect the second output voltage. In a particular example with an analog current (AC) output voltage, the two output voltages are out of phase to each other. In a direct current (DC) implementation, the transformer may be operated to output a positive and a negative output voltage. The apparatus may function as a resonant converter, or may operate in non-resonant mode. In one implementation, an H bridge may provide reactive power support. An inductor filter may be in electrical communication with the secondary transformer coil. Where desired, a diode bridge may be in electrical communication with the primary transformer coil.

The invention provides a method and system for operating an inverter based distributed power generation source with energy storage system, as a Flexible AC Transmission System (FACTS) device—a STATCOM. The inverter based distributed power generation source can provide reactive power compensation, voltage regulation, damping enhancement, stability improvement and other benefits provided by FACTS devices. These STATCOM functions are provided when the said energy storage based distributed power generation source is doing at least one of: i) not exchanging active power with said power grid system, or ii) exchanging active power less than a maximum inverter capacity with said power grid system. The present invention thus provides a technological improvement that opens up a new set of applications and potential revenue earning opportunities for energy storage based distributed power generation sources other than simply from exchanging (injecting or absorbing) active power.