The presence of injected DC has harmful consequences for a power grid system. A piecewise sinusoidal ripple voltage wave at the line-frequency that rides on the main capacitor bank of the power converter is observed. This observation leads to a new DC detection elimination method. Three DC elimination methods for this ripple component are disclosed to allow dissipation of DC energy through heat and/or electromagnetic wave, or to allow transformation of this energy into usable power that is fed back into the power grid.

The presence of injected DC has harmful consequences for a power grid system. A piecewise sinusoidal ripple voltage wave at the line-frequency that rides on the main capacitor bank of the power converter is observed. This observation leads to a new detection method and mitigation method. A two-stage control circuit is added to the operation of a power converter that controls power line impedance in order to mitigate the injected DC and to block DC circulation. This control computes a correction angle to adjust the timing of generated pulsed square waves to counter-balance the ripple. A functional solution and the results of experiments are presented. Furthermore, an extraction method and three elimination methods for this ripple component are presented to allow dissipation of DC energy through heat and/or electronic magnetic wave, or to allow transformation of this energy into usable power that is fed back into the power grid.

Various examples are provided for isolated voltage optimization and control. In one example, a stackable isolated voltage optimization module (SIVOM) includes a transformer having a turns ratio between a primary winding and a secondary winding; a switching circuit configured to energize the secondary winding with a voltage provided from the three-phase power system or short the secondary winding; and a connection block configured to couple the switching circuitry to the first phase and a neutral, or to second and third phases of the three-phase power system. In another example, a system includes a SIVOM coupled to each phase of a three-phase power system, where each SIVOM comprises: a transformer and a switching circuit configured to boost or buck a voltage or change a phase angle of the phase coupled to that SIVOM by energizing a secondary winding of the transformer with a voltage provided from the three-phase power system.

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 grid voltage from a direct current (DC) voltage input modified with the DC bus voltage modified with a notch filter to balance the voltage input and further reduced with the q-axis current. The method modifies the estimated d-axis grid voltage and the q-axis grid voltage by selectively removing second-order harmonics. The method further determines a d-axis voltage output and a q-axis voltage output as a function of the modified estimated d-axis grid voltage and the modified q-axis grid voltage.

A load balancing apparatus for balancing the current supplied on each phase of a multiple phase supply, Each supply phase feeds an AC load, as well as an AC-DC converter. The apparatus measures the current supplied from each phase of the supply as well as the power consumed by each of the AC loads. The power consumed by each of the AC-DC converters is adjusted so that the sum of the current drawn by any one of the AC loads, plus the current drawn by the AC-DC converter on the same supply phase, is substantially balanced between the supply phases. Typically the AC-DC converters supply a common DC battery. In some embodiments each AC load includes a DC-AC converter configured to supply power from the common DC battery to one or more of the AC loads.

A system and method for managing and distributing power is provided, wherein the system includes an electrical power input for receiving three-phase power from an external power source, a first electrical power outlet and a second electrical power outlet. The system further includes current measuring components configured to measure the current on all phases of electrical power being drawn by electrical loads connected to the first electrical power outlet and the second electrical power outlet. The system also includes a processing device to analyze measured current for all phases of electrical power being drawn by the electrical loads. Furthermore, the system includes phase balancing components configured to modify the current for each of the phases of the electrical power being drawn by the electrical loads connected to the first electrical power outlet and the second electrical power outlet such that the current for each phase is substantially balanced.

Various embodiments relate to power distribution systems. A power distribution system may include a switching unit configured to receive power from a plurality of sources, each source of the plurality of sources configured to supply power at a phase offset from a phase of every other source. The power distribution system may also include a plurality of loads. Furthermore, the power distribution system may include at least one monitoring unit configured to selectively couple, via the switching unit, each load of the plurality of loads to a source of the plurality of sources based on at least one of a current power demand of the plurality of loads and a predicted demand of the plurality of loads.

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.

Waveforms in power grids typically reveal a certain pattern with specific features and peculiarities driven by the system operating conditions, internal and external uncertainties, etc. This prompts an observation of different types of waveforms at the measurement points (substations). An innovative next-generation smart sensor technology includes a measurement unit embedded with sophisticated analytics for power grid online surveillance and situational awareness. The smart sensor brings additional levels of smartness into the existing phasor measurement units (PMUs) and intelligent electronic devices (IEDs). It unlocks the full potential of advanced signal processing and machine learning for online power grid monitoring in a distributed paradigm. Within the smart sensor are several interconnected units for signal acquisition, feature extraction, machine learning-based event detection, and a suite of multiple measurement algorithms where the best-fit algorithm is selected in real-time based on the detected operating condition. Embedding such analytics within the sensors and closer to where the data is generated, the distributed intelligence mechanism mitigates the potential risks to communication failures and latencies, as well as malicious cyber threats, which would otherwise compromise the trustworthiness of the end-use applications in distant control centers. The smart sensor achieves a promising classification accuracy on multiple classes of prevailing conditions in the power grid and accordingly improves the measurement quality across the power grid.

Systems and methods are provided for a three-phase compensation system, whereby an electric circuit is configured to be connected with three input phases of a power source and to supply three respective output phases, said electric circuit further configured to compensate for one or two malfunctioning input phases of said three input phases by supplying current from a functioning input phase of said three input phases to replace a malfunctioning input phase.