Methods for determining a line fault of a power system. The methods include obtaining sampled values of voltages and currents of phases of a power line in the power system, determining a phase compensation voltage of a first phase and an interphase compensation voltage of an interphase loop between a second phase and a third phase, and detecting the line fault in the first phase and/or the interphase loop by comparing the phase compensation voltage and the interphase compensation voltage.

The present invention belongs to the technical field of aviation electrics and electric power, and provides an aircraft grid phase angle tracker based on nonlinear active disturbance rejection, which is used to estimate the grid phase angle on AC side of an aircraft grid. A embedded generator in the aircraft grid is arranged inside a compressor of an aviation gas turbine engine, and the embedded generator is directly coupled with the aviation gas turbine engine so that the AC frequency of the embedded generator varies with the speed of the aviation gas turbine engine. The present invention applies the nonlinear active disturbance rejection technology to the phase angle tracking of the more electric aircraft grid, is simple in operation and high in accuracy, and can realize high-accuracy tracking of the grid phase angle. The method has certain extensibility and can be extended to other fields.

A load abnormality detecting circuit for an inverter to detect abnormality of a load during an operation of the inverter which has a switching element and a phase synchronizing loop controlling an output frequency to be a resonance frequency of the load, the load abnormality detecting circuit includes a phase shift detection part that detects a phase shift between an output voltage and an output current which are applied from the inverter to the load and sends an abnormal load signal based on the detected phase shift. The switching element including a self-arc-extinguishing element and a reflux diode connected in reversely parallel to the self-arc-extinguishing element. The phase shift detection part detects advance and delay of a phase of the output current with respect to the output voltage.

The invention involves a multimeter with a meter probe module and phasing probe module capable of wireless communication, proximity measurements, and accurately reading phase degrees. The meter probe module and the phasing probe module can communicate wirelessly, via a wired cable interface, or any combination thereof. The meter probe module and phasing probe module have unique radio frequency serial numbers that allow the probe modules to only communicate with its paired partner probe module while ignoring all other probe modules. The multimeter has a measurement point capable of taking direct contact measurements. The multimeter also has a measurement point capable of taking a voltage measurement without directly contacting the object to be measured. This is accomplished by taking voltage readings from the electric field of the air surrounding said object. The improved multimeter may allow an operator to more safely gather accurate information about an object being measured.

An induction heating device includes a working coil, an inverter including a first switching element and a second switching element that are configured to perform a switching operation and to apply a resonance current to the working coil, a snubber capacitor including a first snubber capacitor connected to the first switching element, and a second snubber capacitor connected to the second switching element, a phase detector configured to detect a phase difference between the resonance current applied to the working coil and a switching voltage applied to the second switching element, and a controller configured to receive, from the phase detector, phase information including the phase difference, provide the inverter with a switching signal to thereby control the switching operation, and adjust an operating frequency of the switching signal based on the phase information to thereby control an output of the working coil.

A method for simple measurement of phase shift between a first clock signal and a second clock signal is described, each clock signal having a period T.sub.0. The method includes: feeding the first clock signal into a first input of a mixer; feeding the second clock signal into a second input of the mixer; feeding the output signal of the mixer into a low pass filter; and measuring the output signal of the low pass filter, with the aid of an output voltage that is normalized to operating voltage of the mixer. A circuit for implementing the method includes a mixer and a low pass filter. The mixer includes a first input for feeding in the first clock signal, and a second input for feeding in the second clock signal. The output of the mixer is connected to the input of the low pass filter.

Methods and systems are disclosed for determining active and/or reactive power flows in a distribution line of a distribution network. The determined power flows may be linear in nature, and they may further be used to determine an overall network power flow for the distribution network. Further, the network power flow can be used to determine a voltage magnitude for any distribution bus in the distribution network. The methods and systems are capable of considering a plurality of sensitivity factors that may affect one or more distribution buses.

The present invention provides a quadrature phase detector including a detection circuit. The detection circuit includes a first switch, a second switch and a first filter, wherein the first switch is controlled by a second clock signal to selectively couple a first clock signal to a first node, the second switch is controlled by the second clock signal to selectively coupled the first node to a reference voltage, and the first filter is configured to filter voltages at the first node to generate a first detection result.

The invention relates to a method for determining a state of at least one cell of a battery, wherein the battery has a plurality of cells, which are connected in series with each other, the method comprising at least the following steps: a) applying an alternating current to the plurality of cells; b) measuring the alternating voltage produced thereby at at least a first cell and a second cell; c) analyzing a phase position of the measured alternating voltage of each cell; wherein a difference at least between a first phase position of a first alternating voltage measured at the first cell and a second phase position of a second alternating voltage measured at the second cell forms a conclusion about a difference between the states of at least the first cell and the second cell.

A wideband digital phase meter and phase detection method are disclosed. The device measures a phase difference between 2 signals and is suitable for integration into a single MMIC. The input signals are compared digitally by using two EXOR gates and integrated over a phase comparison period. The resultant analogue signals are digitised using an Analogue to Digital convertor. Additionally, 2×D-Type registers are used to resolve the (0° to 180°) or (180° to 360°) ambiguity of the EXOR phase detector.