An islanding operation detection device for a distributed power supply comprising an inverter connected to a commercial system power supply comprises: a commercial system frequency measurement circuitry; a reactive power injection amount calculation circuitry to calculate an amount of reactive power injection; a feedback signal generation circuitry; a reactive current control circuitry to feedback-control an output current command value to the inverter; an output current control circuitry to update the reactive current command value when a phase angle of the commercial system voltage is in the range of 90N so as to control an output current value of the inverter to follow the output current command value; and an islanding operation detection circuitry to detect whether or not the distributed power supply is in islanding mode, based on a commercial system frequency when the reactive power corresponding to the calculated amount of reactive power injection is injected.

There is provided a system and method for determining active and reactive currents during asymmetrical low-voltage ride through (LVRT) conditions at an inverter. The method including: receiving an indication of an LVRT condition; and where the largest phase current magnitude does not exceed a phase current limit, determining a maximum active current for associated positive-sequence and negative-sequence reactive currents by determining a largest active current magnitude and outputting the largest active current and associated positive-sequence and negative-sequence reactive currents to the inverter, otherwise: scaling down each of the positive-sequence and negative-sequence reactive currents, or superimposed positive-sequence and negative-sequence reactive currents, uniformly or non-uniformly to determine revised positive-sequence and negative-sequence reactive currents; where the magnitudes of all of the phase currents are below the phase current limit, determining a non-zero positive-sequence revised active current; and outputting the revised active current and the revised positive-sequence and negative-sequence reactive currents to the inverter.

A real current meter reads current from a current probe coupled around power lines of a transformer-based UPS system coupled to a transformer having a high resistance ground with a HRG resistance and determines a real current component of the current read from the current probe.

A real current meter reads current from a current probe coupled around power lines of a transformer-based UPS system coupled to a transformer having a high resistance ground with a HRG resistance and determines a real current component of the current read from the current probe.

The invention is based on an electrical current measuring device for measuring at least one alternating current, with at least one inductive coupling unit, which is intended to convert at least one electrical primary signal into at least one electrical secondary signal, and with a computing unit, which is intended to determine the primary signal from the secondary signal. The computing unit is intended to take into account at least one higher harmonic of the secondary signal when determining the primary signal.

An apparatus for AC physical signals measurement and data acquisition and the method for the same are provided. The apparatus for AC physical signals measurement and data acquisition comprises an analog sampling channel for inputting an AC signal and outputting an analog sampling value; a sampling switch for performing re-sampling to obtain data frequency as required by the receiving side; a register for storing a re-sampling value from the sampling switch; a bus for outputting the re-sampling value in the register to the receiving side; a timing controller for controlling the analog sampling channel and the re-sampling frequency of the sampling switch; and a digital low-pass filter, which has an input connected with the analog sampling value outputted by the analog sampling channel and an output connected with the sampling switch, filters out high frequency components from the sampling value, and has a cut-off frequency that should be lower than 0.5 times the re-sampling frequency of the sampling switch. The apparatus and method for AC physical signals measurement and data acquisition improve accuracy of remote measurement for electric power physical quantities. Not only waveform values are outputted by re-sampling, effective values, steady state values and their fundamental/harmonic wave effective values and steady state values are also outputted. Thus, various requirements by the receiving side on remote measurement data are satisfied.

An apparatus for AC physical signals measurement and data acquisition and the method for the same are provided. The apparatus for AC physical signals measurement and data acquisition comprises an analog sampling channel for inputting an AC signal and outputting an analog sampling value; a sampling switch for performing re-sampling to obtain data frequency as required by the receiving side; a register for storing a re-sampling value from the sampling switch; a bus for outputting the re-sampling value in the register to the receiving side; a timing controller for controlling the analog sampling channel and the re-sampling frequency of the sampling switch; and a digital low-pass filter, which has an input connected with the analog sampling value outputted by the analog sampling channel and an output connected with the sampling switch, filters out high frequency components from the sampling value, and has a cut-off frequency that should be lower than 0.5 times the re-sampling frequency of the sampling switch. The apparatus and method for AC physical signals measurement and data acquisition improve accuracy of remote measurement for electric power physical quantities. Not only waveform values are outputted by re-sampling, effective values, steady state values and their fundamental/harmonic wave effective values and steady state values are also outputted. Thus, various requirements by the receiving side on remote measurement data are satisfied.

A method of diagnosing a fault in a home appliance may include applying, to a plurality of switches included in an inverter, switching control signals that change on and off states of the plurality of switches; obtaining, through a current sensor, current peak value information about the motor based on the switching control signals; and identifying the fault in the home appliance by applying the obtained current peak value information to a fault diagnosis model that is pre-trained to infer the fault in the home appliance.

A voltage management device according to the present disclosure includes a communication unit that obtains, for each of sections in a power system, a measurement value of a voltage measured by a smart meter connected to that section, where the sections are generated by segmentation between monitoring points, and a voltage estimation unit that estimates, for each of the sections, a voltage drop quantity and a voltage rise quantity in that section using the measurement value.

A voltage management device according to the present disclosure includes a communication unit that obtains, for each of sections in a power system, a measurement value of a voltage measured by a smart meter connected to that section, where the sections are generated by segmentation between monitoring points, and a voltage estimation unit that estimates, for each of the sections, a voltage drop quantity and a voltage rise quantity in that section using the measurement value.