In accordance with an example embodiment of the invention, a three-phase power control device is configured to synchronize firing thyristor or SCR sets in consecutive combinations of two of the three phases, to supply current to consecutive combinations of two of the three loads in a three-phase load configuration, to determine real branch impedance of each load from three combinations of two supplied loads, without need of any electrical neutral reference.

The accuracy of photovoltaic simulation modeling is predicated upon the selection of a type of solar resource data appropriate to the form of simulation desired. Photovoltaic power simulation requires irradiance data. Photovoltaic energy simulation requires normalized irradiation data. Normalized irradiation is not always available, such as in photovoltaic plant installations where only point measurements of irradiance are sporadically collected or even entirely absent. Normalized irradiation can be estimated through several methodologies, including assuming that normalized irradiation simply equals irradiance, directly estimating normalized irradiation, applying linear interpolation to irradiance, applying linear interpolation to clearness index values, and empirically deriving irradiance weights. The normalized irradiation can then be used to forecast photovoltaic fleet energy production.

Online estimation of area-level inertia can be used for frequency stability control in low-inertia power systems. This disclosure provides an area-level inertia online estimation method considering inter-area equivalent frequency dynamics. The disclosed method only needs one phasor measurement unit placed at any bus within each area. The inter-area equivalent frequency dynamics model for the multi-area power system is developed, which is employed to estimate area-level inertia under the small disturbance situation. Then, the area-level inertia estimation model boils down to a nonlinear parameter identification problem. The other boundary conditions of the disclosed method are derived by parameter identifiability.

The example embodiments are directed to a system and method for determining an improvement to an asset created by installation of a software application associated with the asset. In one example, the method includes determining an operating performance of an asset operating based on a performance modifying application being installed, establishing a baseline operating performance of the asset from a virtual model of the asset which is running without the performance modifying application installed, determining a change in an operating characteristic of the asset in response to the performance modifying application being installed based on the operating performance of the asset determined from the asset and the baseline operating performance of the asset determined from the virtual model of the asset, and outputting information about the determined change in the operating characteristic of the asset for display on a display device.

The invention relates to a PoE system, which comprises a powered device (2) and a power sourcing device (1). The power sourcing device comprises one or more ports (12) and the powered device is connectable to a port of the power sourcing device by an electrical conductor (13) for conveying the sourced power along with data. The powered device comprises an interface for providing a measure of its energy consumption within the PoE system and, if it does not have the ability to measure its energy consumption, is adapted to negotiate with the power sourcing device whether the power sourcing device has the ability to measure the energy consumption of the powered device and to provide the measured energy consumption to the powered device for provision via the interface. This can make the PoE system more flexible and allow for a single point of contact for providing energy usage feedback.

A method and apparatus generate an energy pulse output while improving the accuracy of energy pulse output. Specifically, an Intelligent Electronic Device employs a method in which a processor receives digital electrical parameter data to at least two buffers alternately; compute a power value in a full zero-crossing cycle in accordance with the digital electrical parameter data when one of the at least two buffers gets fully filled and storing the power value; divide a period that each buffer takes from empty to getting fully filled into a series of intervals; calculate energy consumption in each interval based on the power value stored; totalize the energy consumption; generate an energy pulse output according to a pre-determined threshold and the totalized energy consumption.

A general load flow calculation method for power systems with unified power flow controller (UPFC). On the premise of satisfying the control objectives of UPFC, the calculation method combines the power injection model with the Newton-Raphson algorithm to solve the load flow of the power systems by iteration. It is applicable not only to a conventional UPFC structure, but also to a novel UPFC structure wherein the series and shunt transformers of a UPFC are connected to different AC buses or there are more than one series branch connected to a UPFC. The present invention provides the detailed process for performing a load flow evaluation, and it shows that it is unnecessary to add new state variables when solving the load flow by this method, the dimension of the Jacobian matrix will not increase during the iteration.

A DC/AC converter apparatus is disclosed for converting DC power of a DC energy source into AC power for supplying a load and or the utility grid. The DC/AC converter apparatus is adapted to automatically control the amount of both active and reactive electrical power that is exchanged with the utility grid in order to optimize the electrical power usage of the micro grid.

An electrical measurement device for monitoring the current and power taken by a plurality of electrical loads that may be powered by a selected one of multiple AC power sources comprises sampling the voltage of said sources and the current taken by said loads at a integral number of samples per cycle at sample times determined by an independent processor clock. The integral number of samples of each measured parameter for each cycle are processed to determine a complex number for each parameter representative of the amplitude and the phase relative to the independent processor clock. The phase drift of the substantially constant source voltages may be determined as a measure of frequency of the sources, and may be used to cancel drift of the current measurement to enable averaging. When the source feeding a load is changed, the phase drift is removed from its current measurement by selecting the voltage samples of the source now feeding it to use for drift cancellation or for average power computation and cumulative energy computation.

A system and a method for determining the power loss of a transformer. The method includes measuring voltage and current at the primary side of the transformer, calculating input power by multiplying the measured current and voltage on the primary side of the transformer; measuring voltage and current at the secondary side of the transformer, calculate a nominal error ratio, calculating output power by multiplying the measured current and voltage on the secondary side of the transformer. The method further involves calculating a first corrected power loss by means of multiplying the input power with the nominal error ratio and subtract the output power.