A three-phase power supply system includes three phase branches forming a delta connection. Each of the phase branches includes at least one power conversion cell of at least two stages. The at least one power conversion cell of each of the phase branches is connected in parallel to the at least one power conversion cell of the respective other two phase branches. When one of the phase branches stops operating, the other two phase branches keep operating, and three phase current of the three-phase power supply system can be balanced by regulating active powers and reactive powers of the other two phase branches. Through the invention, when one of the phase branches stops operating, the other two phase branches may keep operating, and three phase current of the three-phase power supply system are balanced.

A three-phase power supply system includes three phase branches forming a delta connection. Each of the phase branches includes at least one power conversion cell of at least two stages. The at least one power conversion cell of each of the phase branches is connected in parallel to the at least one power conversion cell of the respective other two phase branches. When one of the phase branches stops operating, the other two phase branches keep operating, and three phase current of the three-phase power supply system can be balanced by regulating active powers and reactive powers of the other two phase branches. Through the invention, when one of the phase branches stops operating, the other two phase branches may keep operating, and three phase current of the three-phase power supply system are balanced.

The disclosure discloses a system and method for suppressing unbalanced voltage at the Point of Common Coupling (PCC) of dispersed wind farm. According to the disclosure, the wind farm comprising a STATCOM and plurality of wind turbines, dispersed wind farm controller, STATCOM controller, wind turbine controller. The dispersed wind farm controller decides that whether the STATCOM or the wind turbines inject negative-sequence current or not. Adaptive virtual negative-sequence output admittance controller is incorporated into the STATCOM controller and wind turbine controller, which can provide the negative-sequence current reference according to their participation factor. The compensation efforts of STATCOM and wind turbines can be flexibly controlled by changing their participation factor, which is related to the voltage unbalance voltage reference and the remaining capacity. The disclosure has significant advantages in cost and effectiveness to suppress the unbalanced voltage of PCC and improve the wind farm Low voltage fault recovery capability.

Systems and methods for controlling power flow to and from an energy storage system are provided. One energy storage system includes an energy storage device and a bidirectional inverter configured to control a flow of power into or out of the energy storage device via a plurality of phases. The energy storage system further includes a controller configured to control the bidirectional inverter based on a load condition on one or more phases. The controller is configured to control the bidirectional inverter to store power generated by a generator set in the energy storage device and transmit power from the energy storage device to a load driven by the generator set in response to detecting a load imbalance between the phases.

Systems and methods for controlling power flow to and from an energy storage system are provided. One energy storage system includes an energy storage device and a bidirectional inverter configured to control a flow of power into or out of the energy storage device via a plurality of phases. The energy storage system further includes a controller configured to control the bidirectional inverter based on a load condition on one or more phases. The controller is configured to control the bidirectional inverter to store power generated by a generator set in the energy storage device and transmit power from the energy storage device to a load driven by the generator set in response to detecting a load imbalance between the phases.

The present invention relates to a method for power balancing a power grid (10) having multiple phases (12:1,2 3) and a common ground (0). The power grid (10) is connected to at least one load (13, 17) causing a non-uniform power consumption between the multiple phases (12: 1, 2, 3) of the power grid (10). The method comprises: monitoring power provided to the power grid (10) in controller (18), storing available energy in the power grid (10) in an energy storage (16) using multiple inverters (I1, 12, 13), each inverter (I1, 12, 13) is connected between the energy storage (16) and each phase (12: 1, 2, 3) of the power grid (10), and redistributing power between phases (12: 1, 2, 3) based on power available in the energy storage (16) by controlling power flow through the inverters (I1, 12, 13) by the controller (18) based on the non-uniform power consumption.

Aspects of the subject disclosure may include, for example, embodiments detecting and correcting load imbalance on power supply phases within a managed scope using a software controlled power switch matrix that is resident in each power distribution unit supplying power in the managed scope. Managed scope could include a plurality of power distribution units supplying a plurality of circuit or equipment loads in a plurality of premises. On each PDU, the software controlled switch matrix maintains and changes physical coupling of power supply phases to circuit and equipment loads. Further embodiments include correcting power supply phase load imbalances through software commands to adjust the coupling of power supply phases to circuit or equipment loads. Embodiments are intended to help power administrators maintain power supply phase load balance effectively in a managed scope. Other embodiments are disclosed.

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 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 device for controlling a load flow in an alternating-voltage network includes first and second modular series connections of double-pole switching modules interconnected in a parallel circuit to be inserted in series into a phase line of the alternating-voltage network. At least one switching module of each connection has an energy store and semiconductor switches to be switched on and off. The semiconductor switches can be controlled in such a way that a switching module voltage can be generated at terminals of the switching module. The switching module voltage corresponds to a positive or negative storage voltage or a zero voltage. A control apparatus for controlling the switching modules is configured to generate an equalizing current between the modular series connections. A method for controlling a load flow by using the device is also provided.