A method and apparatus for secondary control in a power network. In one embodiment, the method comprises determining a frequency area controller error (ACE) equation for an area and a voltage ACE for the area; decomposing the frequency ACE equation and the voltage ACE equation to generate a first set of symmetric sequences for the frequency ACE equation and a second set of symmetric sequences for the voltage ACE equation, respectively, wherein the first and second sets of symmetric sequences represent positive and negative sequences; and implementing, by an area controller for the area, secondary control on each sequence in the first and second sets of symmetric sequences separately.

Systems and methods may include balancing an unbalanced power cable using a transformer that has one or more phases by selecting a voltage on a tap handle; disposing a first bushing on one or more phases at a different voltage than the selected voltage; and balancing the unbalanced power cable based on the disposition of the first bushing on the one or more phases at the different voltage.

A sensor assembly system and method for providing good voltage accuracy for monitoring a three phase high voltage power line without connecting to ground. The sensor assembly system comprises three sensor assemblies having reference point ends not connected to ground. All three sensor assemblies are connected together at the reference point ends to create a neutral common reference point not connected to ground potential that is at zero volts when all of the three phases are at the same line voltage.

In a three-phase, four-wire electrical distribution system, a zig-zag transformer and at least one Cascade Multilevel Modular Inverter (CMMI) is coupled between the distribution system and the neutral. A controller modulates the states of the H-bridges in the CMMI to build an AC waveform. The voltage is chosen by the controller in order to control an equivalent impedance that draws an appropriate neutral current through the transformer. This neutral current is generally chosen to cancel the neutral current sensed in the line. The chosen neutral current may be based on a remotely sensed imbalance, rather than on a local value, determined by the power utility as a critical load point in the system. The desired injection current is then translated by the controller into a desired zero-sequence reactive impedance, based on measurement of the local terminal voltage, allowing the controller to regulate the current without generating or consuming real power.

Systems and methods may include balancing an unbalanced power cable using a transformer that has one or more phases by selecting a voltage on a tap handle; disposing a first bushing on one or more phases at a different voltage than the selected voltage; and balancing the unbalanced power cable based on the disposition of the first bushing on the one or more phases at the different voltage.

The disclosure relates to a power electronics device having at least two inverters and a transformer apparatus having a core arrangement, at least one primary winding and at least one secondary winding that wind around the core arrangement at least in sections.

A method for identifying an assignment of phase lines of an electrical distribution grid to connections of an electrical device capable of unbalanced-load operation, wherein the device is connected to a plurality of phase lines of the electrical distribution grid, includes setting target parameters assigned to an unbalanced load profile at each of the connections of the electrical device, detecting a temporal profile of a measurement parameter on each of the plurality of phase lines using a detection circuit, comparing the detected temporal profiles of the measurement parameters with the target parameters of the unbalanced load profile for each of the plurality of phase lines, respectively, and identifying the assignment of the phase lines to the connections on the basis of the comparison.

In a power storage system, a three-phase AC wire is connected to a three-phase AC power system. Power storage blocks, each of which includes a power storage module and a power conditioner, are connected in parallel to the three-phase AC wire. A system controller individually controls power storage blocks. The power storage modules each includes: a power storage unit; and a management unit that manages the power storage unit. The power conditioner includes a power converter and a controller. The power converter converts DC power discharged into single-phase AC power and outputs the converted AC power to two lines of the three-phase AC wire, or converts single-phase AC power received from the two lines of the three-phase AC wire into DC power and charges the power storage unit. The controller is connected to the system controller via a communication line and the management unit via a communication line.

In a three-phase, four-wire electrical distribution system, a zig-zag transformer and at least one Cascade Multilevel Modular Inverter (CMMI) is coupled between the distribution system and the neutral. A controller modulates the states of the H-bridges in the CMMI to build an AC waveform. The voltage is chosen by the controller in order to control an equivalent impedance that draws an appropriate neutral current through the zig-zag transformer. This neutral current is generally chosen to cancel the neutral current sensed in the line. In other embodiments, the chosen neutral current may be based on a remotely sensed imbalance, rather than on a local value, determined by the power utility as a critical load point in the system. The desired injection current is then translated by the controller into a desired zero-sequence reactive impedance, based on measurement of the local terminal voltage, allowing the controller to regulate the current without generating or consuming real power. In some embodiments, the zig-zag transformer is omitted.

In a multiphase electrical power construction and assignment, a processor: determines a phase and voltage configuration for bi-directional power device pairs; determines a given bi-directional power device pair is to be coupled to a given phase connection based on the configuration; determines whether the given bi-directional power devices in the given bi-directional power device pair are to be coupled to each other; confirms that the given bi-directional power device pair is not coupled to any of the plurality of phase connections; couples the given bi-directional power device pair to the given phase connections, where power signals of the given bi-directional power device pair are synchronized with a power signal of the given phase connection; and in response to determining that the given bi-directional power devices are to be coupled to each other, couples each of the bi-directional power devices to a short bus.