163 results about "Subharmonic" patented technology

The invention provides a fault line selection method of a low current grounding system using a time-frequency atom decomposition theory. The method comprises the following steps of: based on the time-frequency atom decomposition theory, performing sparse decomposition on zero-sequence current data in a Gabor over-complete dictionary, and then obtaining matched attenuation sinusoidal quantity atoms through optimizing and solving relevant parameters. By the time-frequency atom decomposition method, the disturbance characteristics such as start/stop moments, amplitudes, frequencies and change rules of fundamental wave and each subharmonic can be exactly obtained, and interference signals can be effectively filtered. Energy entropies of the atoms decomposed by time-frequency atoms are arranged from large to small; except from the zero-sequence transient current fundamental wave atom, atom phase angles (polarity) similar with zero-sequence current frequency of each line are compared; if the atom phase angle (polarity) similar with the zero-sequence transient frequency of the line is opposite to that of other lines, the line is the fault line; and if the atom phase angle (polarity) of each line is the same, the fault is bus fault, and the fault line is determined by the comparison result of each frequency phase angle.

The invention discloses a wireless terminal transceiver of a 60GHz RoF (Radio over Fiber) access system. Secondary subharmonic frequency mixing is adopted, and the frequency of a needed local oscillation signal is reduced in a frequency multiplication frequency mixing way, so that the problem of leakage of the local oscillation signal to an antenna, i.e., a radiofrequency transmitting end in the conventional wireless terminal transceiver scheme is solved, and the circuit modulation performance is improved. Meanwhile, a downlink medium frequency analog signal obtained after secondary subharmonic down-conversion is subjected to downlink medium frequency digital signal processing after ADC (Analog to Digital Conversion) to obtain a needed downlink digital baseband signal; and an uplink digital baseband signal is subjected to uplink medium frequency digital signal processing to obtain an uplink medium frequency digital signal. A series of medium frequency digital signal processing such as odd-even extraction or interpolation, symbol modulation, delay filtering, demodulation or modulation and the like is performed in a digital domain, so that the problem of IQ orthogonal mismatch caused by 90-degree phase change on a local oscillation signal for obtaining two paths of analog signals in an analog frequency domain of the conventional receiver is solved.

The invention discloses a surface-mount permanent magnet synchronous motor rotor initial position detection method. The method includes the steps that a high-frequency voltage injection method is adopted for achieving d-axis positive direction judging by extracting d-axis positive direction information included in double injection signal frequency subharmonic in d-axis current responses on the basis of achieving the estimation of an initial position. According to the method, the action of injecting positive and negative pulses additionally and then comparing values of amplitude of the current response is not needed, estimation time is shortened, the estimation process is simplified, the requirement for the precision of current detection is lowered, in addition, tender moving of a rotor can be avoided, and application occasions are broadened.

Harmonics and subharmonics of acoustic measurements made during rotation of a sensor on a downhole are processed to estimate the location of the imager, and size and shape of the borehole. A piecewise elliptical fitting procedure may be used. These estimates may be used to correct measurements made by a standoff-sensitive formation evaluation sensor such as a neutron porosity tool.

The invention discloses a modularized multi-machine parallel-connection large-power APF (active power filter) control system and a realization method. By coordinating an upper layer controller and a lower layer controller, an effect for reasonably allocating the compensative capacity and improving the compensation precision can be realized; the upper layer controller is used for carrying out the coordination and switching control on each power module, for example, the upper layer controller is used for operating and monitoring the quantity of the power modules to be put into use according to a load requirement, numbering the power modules according to a rule and eliminating the switching subharmonic by utilizing the carrier phase shifting; the lower layer controller is used for receiving a compensation order of the upper layer controller and a synchronous signal of a previous sequence number controller and feeding back state information of the power module to the upper layer controller. By adopting the modularized multi-machine parallel-connection large-power APF control system, the compensation capacity of the power module and the computation of an upper layer and a lower layer of the control system are reasonably allocated, the entire system can be enabled to run stably and orderly, the stopping of the entire system caused by the malfunction of one power module can be avoided, and the feasibility and practical value are good.

The invention provides a method for extracting the resistive current of a metal oxide arrester (MOA). The technical scheme comprises the following steps of: acquiring a voltage signal applied to the arrester and leakage current flowing through the MOA and performing fast Fourier transform on the voltage signal to acquire the amplitude and phase of each subharmonic; acquiring a capacitive current signal of which the waveform is the same as that of capacitive current of the arrester and the amplitude is in proportion to that of the capacitive current of the arrester according to a phase relationship between a voltage signal and a current signal on a capacitor and the acquired amplitude and phase of each subharmonic of voltage; and acquiring the resistive current of the arrester according to the principle that the resistive current is orthogonal to the capacitive current of the arrester. The method has a rigorous principle and is convenient to implement; a digital signal has high anti-jamming capability; phase shift is processed by the fast Fourier transform, so even if each subharmonic exists theoretically, errors cannot be generated; and the measurement accuracy of the resistive current can be effectively improved in practical application.

The invention belongs to the technical field of ultrasonic cavitation detection and signal analysis, and relates to a method and a device for separating and detecting focused ultrasonic cavitation signals. An ultrasonic transducer of a device emits cavitation detecting signals in a pulse-inversion mode, and another ultrasonic transducer receives acoustic signals diffused by ultrasonic cavitation and movement of microbubbles; a transducer of another device generates cavitation signals in the pulse-inversion mode; for each cavitation detecting experiment, the detection method extracts background signals when the cavitation does not happen, respectively calculates power spectrums of the acquired cavitation acoustic signals and the background signals, calculates the subtracted power spectrum estimation and phase position estimation, and converts the power spectrum estimation and the phase position estimation into time domain signals to filter noise of a system; and an ICA method separates target signals such as broadband noise component, subharmonic and the like in cavitation acoustic signals from other signal components and extracts characteristic parameters of the cavitation acoustic signals. The detection method has high sensitivity and can perform quantitative analysis.

The invention discloses an inter-harmonics measuring method for the power grid. The inter-harmonics measuring method includes: 1) sampling three-phase current and three-phase voltage of the power grid by sampling frequency fs and sampling points N in real time, and transmitting sampled signals to a DSP (digital signal processor) processing module; and 2) detecting inter-harmonics by means of FFT (fast fourier transform algorithm) according to the current and voltage signals sampled in the step 1). The step 2) includes: 21) utilizing the sampled signals obtained in the step 1) as original signals; 22) calculating amplitude, phase and frequency of fundamental harmonics and harmonics; 23) calculating frequency domain signals of the fundamental harmonics and harmonics; 24) subtracting frequency signals of the fundamental harmonics and harmonics obtained in the step 23) from the original signals to obtain windowed frequency domain signals of the inter-harmonics; and 25) calculating amplitude, phase and frequency of the inter-harmonics obtained in the step 24). On the basis of results obtained by conventional integral subharmonics measuring method, a Hanning window is selected as window function, and inter-harmonics measuring instantaneity is improved by filtering components of fundamental harmonics and integral subharmonics by frequency domain.

Circuits and methods for a switched power converter providing charge power for at least one battery and at the same time delivering current to operate an electronic device, wherein the converter is enabled to operate out of current limit mode, for the maximum possible range of system load requirements, have been achieved. The input current of the power converter is measured within each cycle-by-cycle, i.e. within each cycle of an external clock reference and the charge current is reduced if the input current exceeds a defined portion, e.g. 80% of the maximum allowable input current. The power converter may only enter current limited operation after the charge current has been already reduced to zero. Operating out of current limit mode ensures a maximum efficiency of the converter, maximize the current deliverable to a given load and minimizes subharmonics in the output current and voltage, thereby minimizing interference with other system component.

A method for identifying an unfolded non-synchronous blade vibration frequency in blades on a rotating rotor using a plurality of probes spaced from each other about the rotor. A set of data is acquired from the probes during a predetermined number of rotor revolutions and is processed using a Fourier analysis to generate an output representative of frequencies and phase shift angles corresponding to blade vibrations. The phase shift angles are used to identify a subharmonic for a blade vibration frequency to provide an output identifying the vibration frequency. A space dispersion and time dispersion of probes is described to increase the accuracy of the subharmonic determination using the phase shift angles.

The invention discloses a compound control method of a photovoltaic grid-connected inverter, relating to a photovoltaic grid-connected inverter. The control method of the traditional inverter has the defects of larger harmonic distortion of the output current of the inverter and poor wave form quality. The compound control method is characterized by comprising the steps of: detecting a DC busbar voltage and a three-phase current outputted by an inverter, calculating a d shaft current reference value according to the DC busbar voltage; converting the three-phase current output by the inverter into a d shaft current measured value and a q shaft current measured value; obtaining a current difference; respectively calculating according to the current difference to obtain a PI control voltage compensating value, a resonance control voltage compensating value and a repeating control voltage compensating value by a PI control module, a resonance control module and a repeating control module; and generating a PWM (Pulse Width Modulation) wave by the PWM control module according to a composition result of the PI control voltage compensating value, a resonance control voltage compensating value and a repeating control voltage compensating value. According to the invention, specific subharmonics and periodic disturbance are inhibited, stability of the inverter is ensured, and dynamic property of the inverter is improved.

A mixer design is described that permits greater integration on standard silicon chips with an improvement in power and linearity compared to previous mixer designs, enabling low-power, high performance RF reception.

The invention relates to a subharmonic detection method suitable for an APF (Active Power Filter) under a load unbalance system, relating to the field of subharmonic detection under the load unbalance system and solving the problem of inaccurate detection result because of leaving out of consideration of load unbalance and compensation condition of the active power filter when an existing harmonic detection method is used for detecting a harmonic current. The subharmonic detection method provided by the invention is capable of detecting a positive-sequence harmonic and a negative-sequence harmonic in the load unbalance system to simultaneously obtain a positive-sequence component and a negative-sequence component of the positive-sequence harmonic and the negative-sequence harmonic, and is capable of detecting any subharmonics; and meanwhile, in order to improve the compensation precision of the APF, any subharmonics are subjected to lead compensation to realize lead prediction of current instantaneous values of any subharmonics and compensate the phase delay caused by a control system, an APF output filter and the like, so that a detection result is more accurate. The subharmonic detection method is suitable for performing the subharmonic detection under the load unbalance system.

A quadrature subharmonic mixer comprises a polyphase filter configured to generate quadrature components of a local oscillator (LO) reference signal, a summing and scaling element configured to create additional components of the LO reference signal, and a plurality of mixer elements configured to multiply the quadrature components of the LO reference signal and the additional components of the LO reference signal with a radio frequency (RF) signal to obtain a downconverted version of the RF signal.

The invention relates to a particles-impact damper with an elastic support. The inner part of the particles-impact damper is provided with an elastic energy-storage component and a plastic impact energy-dissipation component. The invention is characterized in that the particles-impact damper is connected with a controlled main system through the elastic support and the natural vibration frequency of the particles-impact damper is not greater than that of the controlled main system. The elastic support can be a spiral spring, a plate spring or an elastic cushion; and free movement direction of the elastic support is identical to the vibration direction of the controlled main system. The particles-impact damper can effectively reduce acceleration in impact process and decrease impact on the controlled main system so as to consume vibration energy of the controlled main system to the maximum extent, reduce the energy retransmission to the controlled main system and alleviate the impact of ultraharmonics and subharmonic. The particles-impact damper can be applied to the vibration control of nonlinear systems with low frequency and dense modes.

A method and an apparatus for detecting a pitch in input voice signals by using a subharmonic-to-harmonic ratio (SHR). The pitch detection method includes performing a Fourier transform on the input voice signals after performing a pre-processing on the input voice signals, performing an interpolation on the transformed voice signals, calculating a normalized local center of gravity (NLCG) on a spectrum of the interpolated voice signals, calculating a cumulated sum of the calculated NLCG, calculating an SHR from the spectrum based on the calculated cumulated sum, and extracting the pitch based on the calculated SHR.

The invention provides an electric energy meter harmonic test device and a method thereof. The device comprises a three-phase program-controlled AC source, a current harmonic generator, a standard meter and an error calculator, wherein the three-phase program-controlled AC source, the current harmonic generator, the standard meter and the error calculator are connected in sequence. The method comprises the following steps: (1) the three-phase program-controlled AC source and the current harmonic generator generating desired parameters; (2) providing the desired parameters to a calibrated meter and the standard meter; (3) calculating error by comparing electric energy pulses of the calibrated meter and the standard meter; (4) comparing the error with an error of a power supply generating sine waves, and detecting the error influence quantity. The electric energy meter harmonic test device provided by the invention can effectively realize output of voltage, current higher harmonics, DC even harmonics, subharmonics and odd harmonics, and can switch among the DC even harmonics, subharmonics and odd harmonics, so that the device can carry out a plurality of harmonic tests by a single wiring operation.

The invention discloses an appointed subharmonic compensation APF (active power filter) and a harmonic detection and control method thereof. The APF comprises a signal sampling module (1), a human-computer interaction interface (2), an appointed subharmonic current detection module (3), a current tracking control module (4) and a power circuit module (5), wherein the signal sampling module transmits a collected signal to the appointed subharmonic current detection module; the human-computer interaction interface is connected with the appointed subharmonic current detection module; the appointed subharmonic current detection module is connected with the power circuit module via the current tracking control module. According to the APF, one or multiple times of harmonic of the harmonic current generated by load in a power grid can be appointed to carry out harmonic separation detection and compensation by the human-computer interaction interface, and various different working condition requirements can be satisfied in a flexible working mode. With the method, the stability and the reliability of harmonic detection and compensation current are enhanced so as to enhance the system stability and improve the system reliability.

In a method for the control of thermoacoustic instabilities or oscillations in a combustion system (15), pressure oscillations and/or heat release oscillations in the combustion system (15), which are linked to the thermoacoustic instabilities, are measured, the resulting measurement signal is filtered, time-delayed and amplified, and, according to the filtered, delayed and amplified measurement signal, the fuel stream to or the combustion air for the combustion system (15) is modulated. In such a method, the use of more cost-effective modulation devices is achieved in that modulation takes place at a subharmonic of a dominant instability frequency in the combustion system (15).

The invention provides a current-mode current induction circuit externally connected with a power MOS (metal oxide semiconductor) transistor and a method for realizing the current mode. The current induction circuit further comprises a current sampling circuit, an adjustable external compensating resistor and a superposed circuit, wherein the current sampling circuit is used for converting the current flowing through the MOS transistor into voltage on the external resistor; the superposed circuit is used for superposing the voltage on the external resistor with the slope compensation voltage;and the resistance value of the external compensating resistor is set according to the on resistance of the external MOS transistor. The circuit and method provided by the invention have the following advantages and positive effects: sampling of the output current of the external MOS transistor can be realized under the current mode and the adjustable external compensating resistor is used for setting the value of the transfer resistance as a fixed value, thus the fixed current compensation slope can be designed to eliminate instability of subharmonics; the technical problem that the technicians in the field can only adopt voltage mode during externally connecting the MOS transistor before is solved; the complexity of loop compensation is reduced; and adjustment is more flexible.

The invention discloses a high-dynamic-response pulse width modulation method at a low switching frequency. The method comprises the steps that (1) in the offline state, an optimization algorithm is adopted for calculation with the modulation ratio as a variable for the purpose of eliminating specific secondary current harmonics, so that switching angles corresponding to all frequency division numbers are calculated; (2) judgment and rejection principles are put forward for the calculated switching angles, wherein if the shape of an obtained stator flux link is a regular hexagon or a regular octadecagon or a regular shape with 30 edges, namely the difference of the numbers of the edges is 12, the switching angles are adopted, and the switching angles are abandoned otherwise; (3) the switching angles corresponding to the modulation ratio are sequentially stored at fixed positions in hardware, or curve fitting is conducted on the switching angles, so that the corresponding relation between the modulation ratio and the switching angles is obtained; (4) in the actual operation process of a system, table look-up or calculation is conducted according to the modulation ratio and the frequency division numbers, so that all the switching angles are obtained. The high-dynamic-response pulse width modulation method at the low switching frequency has the advantages that the specific subharmonics can be effectively eliminated, so that system noise and torque pulsation are lowered, and the dynamic responsiveness of the system can be greatly improved at the same time.