Abstract: Method and apparatus for determining relative value of loads. In one embodiment the method comprises determining, for a load in a plurality of loads where (i) each load in the plurality has a weight and a value associated with it and (ii) the plurality is operating according to a primary solution where a net weight of all loads with an activated state satisfies a primary threshold, a change in operating state; determining a secondary solution for a subset of loads not including the load having the change, such that a net weight of all loads in the subset with an activated state satisfies a secondary threshold based on the primary threshold; and determining, based on the values of loads in the subset that have operating states in the secondary solution different from their operating states in the primary solution, an updated value for the load having the change.

Abstract: Method and apparatus for controlling power conditioners in a distributed resource island. In one embodiment, the method comprises comparing, at a power conditioner operating in a de-energized state, an input of the power conditioner to an input threshold, wherein the power conditioner is coupled to an islanded grid; operating the power conditioner, when the input exceeds the input threshold, in a soft-grid mode to generate a touch-safe AC voltage that is coupled to the islanded grid; and activating the power conditioner, based on an impedance of the islanded grid and load demand for the power conditioner, to operate proximate its nominal output voltage.

Abstract: A method and apparatus for power converter current control. In one embodiment, the method comprises controlling an instantaneous current generated by a power converter such that that power converter appears, from the perspective of an AC line coupled to the power converter, as a virtual AC voltage source in series with a virtual impedance.

Abstract: 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.

Abstract: A system and apparatus for autonomous charge balancing of an energy storage device of the microgrid. In one embodiment the apparatus comprises a power conditioner, coupled to the energy storage device, comprising a droop control module for operating the power conditioner, during an autonomous mode of operation, such that the state of charge of the energy storage device is autonomously driven toward the state of charge of at least one other energy storage device of the microgrid.

Abstract: A method and apparatus for power converter current control. In one embodiment, the method comprises controlling an instantaneous current generated by a power converter that is part of an AC battery such that the power converter appears, from the perspective of an AC line coupled to the power converter, as a virtual AC voltage source in series with a virtual impedance, wherein real and reactive phasor currents for the power converter are indirectly controlled by modifying amplitude and phase of a virtual AC voltage waveform that defines the virtual AC voltage source.

Abstract: A method and apparatus for minimizing circulating currents on a power distribution line. In one embodiment, the method comprises dynamically adjusting a turns ratio of a tap changing transformer, the tap changing transformer coupled to a power grid distribution line that is also coupled to a plurality of microgrid branches wherein at least one microgrid branch of the plurality of microgrid branches comprises a distributed energy resource (DER), based on a reactive power measured locally to the tap changing transformer, to minimize current circulating on the power grid distribution line.

Abstract: A method and apparatus for controlling a microgrid load. In one embodiment, the method comprises measuring at least one grid parameter of a microgrid transmission line coupled to a load in a microgrid; computing, using the at least one grid parameter and a droop control technique, at least one virtual set-point; determining a modification to operation of the load based on the at least one virtual set-point; and modifying operation of the load based on the modification.

Abstract: Method and apparatus for load-based primary regulation in a power system. In one embodiment the method comprises receiving information pertaining to each load of a plurality of loads in a power distribution system; generating, using the information, a plurality of combinations of operating states for the plurality of loads that provides a pseudo-linear response for all the plurality of loads; generating a look up table (LUT) that comprises the plurality of combinations of operating states; and transmitting the LUT to each load of the plurality of loads for use by the plurality of loads in primary regulation.

Abstract: A method and apparatus for tertiary control with over-current protection. In one embodiment, the method comprises calculating at least one unconstrained optimal net intertie target for an area of a power network; calculating, for each resource within the area, optimal scheduled current to achieve the at least one unconstrained optimal net intertie target; calculating, using the optimal scheduled currents and a plurality of stress coefficients, net scheduled current for each power line segment within the area; comparing the net scheduled currents to corresponding stress thresholds to identify any stress violations; reducing, when the comparing step identifies one or more stress violations, the optimal scheduled current for one or more resources contributing to the one or more stress violations; and calculating, when the comparing step identifies the one or more stress violations, updated optimal scheduled current for one or more resources not contributing to the one or more stress violations.

Abstract: A method and apparatus for power converter current control. In one embodiment, the method comprises controlling an instantaneous current generated by a power converter such that that power converter appears, from the perspective of an AC line coupled to the power converter, as a virtual AC voltage source in series with a virtual impedance.

Abstract: A method and apparatus for autonomous, automatic interleaving of cycled loads coupled to a grid. In one or more embodiments, the method comprises (i) determining, by a smart load coupled to a grid, a first grid stress value; (ii) comparing, by the smart load, the first grid stress value to an activation threshold; (iii) waiting, by the smart load, when the first grid stress value is less than the activation threshold, a delay period; (iv) determining, by the smart load and after the delay period ends, a second grid stress value; (v) comparing, by the smart load, the second grid stress value to the activation threshold; and (iv) activating, by the smart load, when the second grid stress value is less than the activation threshold.

Abstract: A method and apparatus for power converter current control. In one embodiment, the method comprises controlling an instantaneous current generated by a power converter that is part of an AC battery such that the power converter appears, from the perspective of an AC line coupled to the power converter, as a virtual AC voltage source in series with a virtual impedance, wherein real and reactive phasor currents for the power converter are indirectly controlled by modifying amplitude and phase of a virtual AC voltage waveform that defines the virtual AC voltage source.

Abstract: A method and apparatus for minimizing circulating currents on a power distribution line. In one embodiment, the method comprises dynamically adjusting a turns ratio of a tap changing transformer, the tap changing transformer coupled to a power grid distribution line that is also coupled to a plurality of microgrid branches wherein at least one microgrid branch of the plurality of microgrid branches comprises a distributed energy resource (DER), based on a reactive power measured locally to the tap changing transformer, to minimize current circulating on the power grid distribution line.

Abstract: A method and apparatus for setting an impedance of a power conditioning unit (PCU). In one embodiment, the method comprises applying a disturbance to a virtual AC voltage produced by a power conditioning unit (PCU) that is coupled to a power grid, where the disturbance has a first phase; measuring a second phase of the applied disturbance on the power grid; comparing the second phase of the applied disturbance to the first phase of the disturbance; and adjusting, when the second phase differs from the first phase by more than a threshold amount, an impedance of the PCU.

Abstract: Method and apparatus for controlling power conditioners in a distributed resource island. In one embodiment, the method comprises comparing, at a power conditioner operating in a de-energized state, an input of the power conditioner to an input threshold, wherein the power conditioner is coupled to an islanded grid; operating the power conditioner, when the input exceeds the input threshold, in a soft-grid mode to generate a touch-safe AC voltage that is coupled to the islanded grid; and activating the power conditioner, based on an impedance of the islanded grid and load demand for the power conditioner, to operate proximate its nominal output voltage.

Abstract: A method and apparatus for multi phase shift control of a power converter. In one embodiment, the method comprises controlling a phase shift between a left leg and a right leg of a first bridge of the power converter during operation of the power converter; and controlling a phase shift between the first bridge and a second bridge of the power converter during the operation of the power converter, wherein the phase shift between the left and the right legs and the phase shift between the first and the second bridges are controlled based on an input voltage of the power converter and a required output voltage of the power converter.

Abstract: A method and apparatus for setting a virtual impedance ratio of a power conditioning unit (PCU). In one embodiment, the method comprises applying a disturbance to a virtual AC voltage of a power conditioning unit (PCU) operating in a virtual impedance droop control mode in which the PCU appears, from the perspective of a power grid coupled to the PCU, as a virtual AC voltage source in series with a virtual impedance; measuring the phase of the applied disturbance on the power grid; comparing the measured phase of the applied disturbance on the power grid to the phase of the disturbance; and adjusting, when the measured phase of the applied disturbance on the power grid differs from the phase of the disturbance by more than a threshold amount, a ratio of a resistive impedance of the virtual impedance to an inductive impedance of the virtual impedance.

Abstract: Method and apparatus for controlling power conditioners in a distributed resource island. In one embodiment, the method comprises comparing, at a power conditioner operating in a de-energized state, an input of the power conditioner to an input threshold, wherein the power conditioner is coupled to an islanded grid; operating the power conditioner, when the input exceeds the input threshold, in a soft-grid mode to generate a touch-safe AC voltage that is coupled to the islanded grid; comparing, by the power conditioner, an impedance of the islanded grid to a grid impedance range; comparing, by the power conditioner, load demand of the power conditioner to an activate threshold; and activating the power conditioner, when the impedance is within the grid impedance range and the load demand exceeds the activate threshold, to operate proximate its nominal output voltage.

Abstract: A method and apparatus for autonomously operating a microgrid power generator. In one embodiment, the method comprises obtaining a first measurement of at least one grid parameter of a microgrid transmission line coupled to a power generator in a microgrid; comparing the first measurement to a turn-on threshold; initiating, when the first measurement satisfies the turn-on threshold, power generation by the power generator; obtaining, after initiation of the energy generation, a second measurement of the at least one grid parameter of the microgrid transmission line; comparing the second measurement to a shut-down threshold that is greater than the turn-on threshold; and stopping, when the second measurement satisfies the shut-down threshold, the power generation by the power generator.