A metal detector for buried and abandoned chemical weapons is provided, comprising: a transmitting circuit to transmit a detection signal; a frequency selection unit electrically connected to the transmitting circuit and configured to regulate a frequency of the detection signal; a receiving circuit to receive a reflected signal returned from the substance detected; an analog-digital conversion unit electrically connected to the receiving circuit and configured to convert the reflected signal into a digital signal; and a control unit electrically connected to the analog-digital conversion unit. In the present disclosure, the frequency of the detection signal can be regulated by changing a current frequency of the transmitting circuit, so that several forms of iron compound can be detected, thereby increasing the detection accuracy of the ACWs.

A metal detector for buried and abandoned chemical weapons is provided, comprising: a transmitting circuit to transmit a detection signal; a frequency selection unit electrically connected to the transmitting circuit and configured to regulate a frequency of the detection signal; a receiving circuit to receive a reflected signal returned from the substance detected; an analog-digital conversion unit electrically connected to the receiving circuit and configured to convert the reflected signal into a digital signal; and a control unit electrically connected to the analog-digital conversion unit. In the present disclosure, the frequency of the detection signal can be regulated by changing a current frequency of the transmitting circuit, so that several forms of iron compound can be detected, thereby increasing the detection accuracy of the ACWs.

An insulation detecting method for the electric machine is provided. The leakage current leakage and the leakage resistance are detected and determined by the output potential waveform resulted from the inversion operation of the first switch and the second switch of the driver. Besides, the signal is amplified through the software or the amplification circuit coupled between the electric machine and the driver to detect the leakage resistance approximately to 5M.

An insulation detecting method for the electric machine is provided. The leakage current leakage and the leakage resistance are detected and determined by the output potential waveform resulted from the inversion operation of the first switch and the second switch of the driver. Besides, the signal is amplified through the software or the amplification circuit coupled between the electric machine and the driver to detect the leakage resistance approximately to 5M.

A system frequency detector includes an orthogonal coordinate signal generator generating an orthogonal two-phase voltage signal from a three-phase voltage signal of three-phase alternating current power by converting the three-phase voltage signal into a two-phase voltage signal orthogonal to the three-phase voltage signal, converting the two-phase voltage signal into a voltage signal of a rotating coordinate system, calculating a moving average of the voltage signal of the rotating coordinate system, and performing an inverse transformation of the voltage signal of the rotating coordinate system after calculating the moving average. A frequency calculator calculates an angular frequency based on the two-phase voltage signal, and an arithmetic unit calculates a system frequency of the power system from the angular frequency. The frequency calculator includes a rate limiter in series with the arithmetic unit, the rate limiter limiting a change of the system frequency equal to or greater than a prescribed change rate.

A system frequency detector includes an orthogonal coordinate signal generator generating an orthogonal two-phase voltage signal from a three-phase voltage signal of three-phase alternating current power by converting the three-phase voltage signal into a two-phase voltage signal orthogonal to the three-phase voltage signal, converting the two-phase voltage signal into a voltage signal of a rotating coordinate system, calculating a moving average of the voltage signal of the rotating coordinate system, and performing an inverse transformation of the voltage signal of the rotating coordinate system after calculating the moving average. A frequency calculator calculates an angular frequency based on the two-phase voltage signal, and an arithmetic unit calculates a system frequency of the power system from the angular frequency. The frequency calculator includes a rate limiter in series with the arithmetic unit, the rate limiter limiting a change of the system frequency equal to or greater than a prescribed change rate.

A method includes performing by a processor: receiving a first plurality of power system frequency measurements from a plurality of phasor measurement units (PMUs) in the power system over a first time interval, generating a first plurality of multi-dimensional ellipsoids based on the first plurality of power system frequency measurements, extracting a plurality of first graphic parameter values from the first plurality of multi-dimensional ellipsoids, respectively, performing a regression analysis on the plurality of first graphic parameter values to generate a predictive relationship between the plurality of first graphic parameter values and inertia values of the power system, receiving a second plurality of power system frequency measurements from the plurality of PMUs over a second time interval, generating a second plurality of multi-dimensional ellipsoids based on the second plurality of power system frequency measurements, extracting a plurality of second graphic parameter values from the second plurality of multi-dimensional ellipsoids, respectively, and estimating a current inertia value of the power system based on the plurality of second graphic parameter values by using the predictive relationship between the plurality of first graphic parameter values and the inertia values of the power system.

A method includes performing by a processor: receiving a first plurality of power system frequency measurements from a plurality of phasor measurement units (PMUs) in the power system over a first time interval, generating a first plurality of multi-dimensional ellipsoids based on the first plurality of power system frequency measurements, extracting a plurality of first graphic parameter values from the first plurality of multi-dimensional ellipsoids, respectively, performing a regression analysis on the plurality of first graphic parameter values to generate a predictive relationship between the plurality of first graphic parameter values and inertia values of the power system, receiving a second plurality of power system frequency measurements from the plurality of PMUs over a second time interval, generating a second plurality of multi-dimensional ellipsoids based on the second plurality of power system frequency measurements, extracting a plurality of second graphic parameter values from the second plurality of multi-dimensional ellipsoids, respectively, and estimating a current inertia value of the power system based on the plurality of second graphic parameter values by using the predictive relationship between the plurality of first graphic parameter values and the inertia values of the power system.

A phase frequency detector-based high-precision feedback frequency measurement apparatus and method: a Field Programmable Gate Array (FGPA) roughly measures a frequency fx of a measured time-frequency pulse by an equal-precision frequency measurement method; a Direct Digital Synthesizer (DDS) automatically synthesizes a frequency fx according to the fx roughly measured by the FPGA; the fx and the fx are sent to a phase frequency detector for performing phase frequency detection and then sent to the FPGA after passing through a charge pump, a low-pass filter circuit, and an (Analogue-to-Digital) A/D converter; the FPGA processes a frequency difference obtained by the phase frequency detector and then transmits the processed frequency difference to the DDS to form a negative feedback frequency measurement system so that the DDS continuously adjusts the fx according to a frequency difference measurement result until the output of the DDS is stable. Therefore, precise measurement of the time-frequency pulse to be measured is realized.

A measurement system and method tests for spurious emissions included in a signal transmitted from a mobile terminal in a shorter time than before. The system includes: a band division unit for dividing the measurement frequency band into a plurality of divided bands; a first spurious measurement control unit which causes a measurement device to measure the spurious emissions of the signal to be measured in each divided band and the peak power of the spear in each divided band; and a first pass/fail determination unit that determines whether or not pass determination criteria is satisfied. The first pass/fail determination unit determines whether the peak power does not exceed the threshold of the pass determination criteria in each divided band. The threshold value of the pass determination criteria is lower than the threshold of the standard determination criteria defined by the 3GPP standard.