Methods, systems, and apparatus, including computer programs encoded on a storage device, for identifying phases of electrical grid wires are disclosed. A method includes identifying, within an image of a utility pole, a cross-arm supporting multiple wires; identifying a cardinal orientation of the cross-arm based on characteristics of the image; and determining, based on the cardinal orientation of the cross-arm, an electrical phase for each of the wires supported by the cross-arm. Identifying the cardinal orientation of the cross-arm includes: determining an orientation of the cross-arm relative to an axis of a field of view of the image; determining a cardinal orientation of the axis of the field of view; and estimating the cardinal orientation of the cross-arm based on an angular difference between the orientation of the cross-arm relative to the axis of a field of view and the cardinal orientation of the axis of the field of view.

A method comprises, at a power balancing circuit for three-phase AC power: feeding three power phases to respective loads; measuring power drain on the three power phases by the respective loads; based on measuring, detecting an unbalanced power drain across the three power phases due to a relatively light power drain on one or more lightly loaded power phases and a relatively high power drain on one or more heavily loaded power phases; computing an amount of power to be drained from the one or more lightly loaded power phases and to be fed to the one or more heavily loaded power phases to balance the power drain across the three power phases; and transferring the amount of power from the one or more lightly loaded power phases to the one or more heavily loaded power phases to balance the power drain across the three power phases.

Disclosed is a method for operating a three-phase inverter on a three-phase load. The three-phase inverter has a direct voltage intermediate circuit, at least one three-phase bridge circuit, and at least one control unit for controlling the bridge circuit. In the at least one bridge circuit, at least two power switches per phase are provided, which are connected in series parallel to the direct voltage intermediate circuit. Depending on predefined target voltage values of the three phases of the inverter, the power switches of each individual phase are actuated via the control unit such that a three-phase alternating voltage is generated on the three-phase load via switching operations of the power switches. Very good dynamic control behaviour can be achieved despite cost-effective dimensioning of the IGBT power switches of the three-phase bridge circuit.

A method for stabilising a power grid by at least one backup battery of a network element for use in a communications network. The method comprises determining (402) future power consumption of the network element, determining (404) a required backup energy level of said at least one backup battery based on said determined future power consumption for operation of the network element for a defined period and providing (406) a fraction of capacity of said at least one backup battery to stabilise a power grid.

A device, for a low-voltage circuit, includes a four-pole input connection for a three-phase AC circuit having a neutral conductor, including a first, second and third input phase pole, and an input neutral conductor pole; a two-pole output connection; a first connection between the between the input and output neutral conductor pole; a first, second and third electronic switch unit to carry out opening and closing of an electrical connection; a voltage sensor for determining the voltage level of the input phase poles; and a controller connected to the voltage sensor and the electronic switch units, designed such that, depending on the voltage level of the input phase poles, the first, second or third input phase pole is connected to the first output phase pole via the respective electronic switch unit, the first output phase pole being connected to the respective input phase pole having the highest voltage level.

The present disclosure provides an exemplary three-phase multi-tap balancing distribution transformer capable of operation with both balanced and unbalanced loads and that provides a wide range of incremental voltages to compensate for the varying voltage drops and imbalances as the attached conductor length increases and allows users the ability to incrementally and independently adjust the voltage specifically feeding a specific phase. Incremental adjustment is achieved via the transformer and without any fragile or other external devices or components between the power source and load-side equipment terminals. The transformer, through the use of at least one phase-specific tap-change switch is capable of directly controlling the secondary voltage of the applicable phase independently from the other phases and, thus, does not affect the voltage on the other phases.

A power conversion device includes a power conversion circuit and a power conversion control circuit. The power conversion control circuit is configured to calculate a positive-phase sequence current command signal based on a positive-phase sequence voltage of the three-phase AC output voltage and a positive-phase sequence current of the three-phase AC output current, calculate a negative-phase sequence current command signal based on the first axis negative-phase sequence current command value, the second axis negative-phase sequence current command value, the first axis negative-phase sequence current value, and the second axis negative-phase sequence current value, and generate the switching control signal based on the positive-phase sequence current command signal and the negative-phase sequence current command signal.

A method for providing grid-forming control of an inverter-based resource includes receiving a negative-sequence voltage feedback of the inverter-based resource. The method also includes receiving at least one negative-sequence feedback signal of the inverter-based resource. The method also includes determining, via a negative-sequence regulator, one or more control signals indicative of a desired negative-sequence impedance of the inverter-based resource using the at least one negative-sequence feedback signal. Further, the method includes generating, via the negative-sequence regulator, a control command for the inverter-based resource based on the one or more control signals. Moreover, the method includes controlling the inverter-based resource based on the control command to achieve the desired negative-sequence impedance of the inverter-based resource.

A three-level power converter includes a direct current power supply unit including a filter capacitor connected between a high potential line and an intermediate potential line and a filter capacitor connected between the intermediate potential line and a low potential line, and a power conversion circuit that converts a three-level direct current voltage output from the high potential line, the intermediate potential line, and the low potential line into a three-phase alternating current voltage. A controller generates an imbalance signal representing an imbalance between a first capacitor voltage and a second capacitor voltage on the basis of values detected by voltage sensors, and generates a modulation signal for causing the power conversion circuit to perform a two-phase modulation operation on the basis of a superimposed signal obtained by superimposing the imbalance signal on a reference signal of the three-phase alternating current voltage.

A method for controlling a chain-link power converter including three phase legs, each of which phase legs includes a plurality of series-connected converter cells, each of the cells including a DC capacitor, the phase legs being connected in a delta configuration. The method includes detecting an unsymmetrical voltage condition at a terminal of the converter; determining a ratio between a zero sequence and a negative sequence component of a compound current to be injected into the converter, based on the detected unsymmetrical voltage condition; calculating the compound current comprising the zero sequence component and the negative sequence component in accordance with the determined ratio; and injecting the compound current into the converter to control the converter in view of the detected unsymmetrical voltage condition.