2623 results about "Frequency deviation" patented technology

A means is provided to estimate the amount of frequency deviation experienced in a precision resonator resulting from the effects of previous thermal history, acceleration, or aging by determining the differential effect of the perturbing condition on different resonant modes in the same resonator or on different resonators exposed to the same environment. The measurements may be made simultaneously, or sequentially against an independent frequency source. Residual frequency hysteresis effects may be determined in connection with an independent temperature sensor if the exact temperature in not known.

Methods, systems and computer program products are provided for synchronizing clocks in a computer network. A first node clock is synchronized to a second node clock by establishing an initial value of a virtual second node clock at the first node. The initial value may be established based on the first node clock and a timing record received from the second node. A frequency bias adjustment factor is determined for the virtual second node clock based on a plurality of clock requests from the first node and a plurality of corresponding responses from the second node spaced apart in time. The responses from the second node include the timing record based on the second node clock. A time of the virtual second node clock is provided based on the frequency bias adjustment factor responsive to requests for the virtual second node clock at a time between requests.

The invention discloses a controller and method for simulating the active power frequency of a double-fed induction generator (DFIG) in combination with inertia and over speed. The controller comprises a frequency deviation detecting module, a blocking module, a regulating variable setting module, a time delay module and a speed protecting module which are connected in sequence, wherein a real-time grid frequency signal and a frequency setting value are respectively input in the frequency deviation detecting module to obtain the frequency deviation signal of the grid at that time; the frequency deviation signal enters the regulating variable setting module through the blocking module, and the regulating variable setting module obtains a speed regulating variable according to the frequency deviation signal; and the speed protecting module enables the DFIG unit to exit frequency modulation under an abnormal speed condition, and can put into the frequency modulation again after time delay for a period of time. The controller has the beneficial effects that large-scale double-fed wind power integration takes the place of a conventional synchronous generator to cause that the system inertia is reduced and thus the transient stability of system frequency is worsened, and the comprehensive frequency controller provided by the invention can effectively solve the problem.

The invention belongs to an electric energy quality monitoring technology, particularly a ship electric energy quality monitoring system. The system comprises a data analysis evaluation subsystem and data acquisition processing subsystems distributed on each node. The data acquisition processing subsystems are used for acquiring three-phase voltage and current signals of a ship power grid in real time and providing the three-phase voltage and current signals for the data analysis evaluation subsystem by the Ethernet; the data analysis evaluation subsystem is used for completing calculation of steady-state electric energy quality indexes in an on-line mode and giving an electric energy quality comprehensive evaluation according to an index weight; the detection of transient-state electric energy quality perturbation parameters is completed in an off-time mode; the steady-state electric energy quality indexes comprise a voltage deviation, a frequency deviation, harmonic waves, three-phase unbalance, voltage fluctuation and flicker; and the transient-state electric energy quality perturbation parameters comprise short duration voltage variation, time varying harmonic waves and inter-harmonics. According to the system, all the nodes on the power grid can be simultaneously monitored, the factors influencing the electric energy quality can be analyzed by a plurality of indexes and the level of the electric energy quality of the power grid is timely known.

The invention discloses a method for timing and synchronizing wireless communication, a method for searching districts and a system thereof. The method fully utilizes the time domain repetitiveness of a main synchronizing signal in a 5ms period and comprises: firstly, adopting predetermined step length sliding time domain cross-correlation to realize blind timing coarse synchronization with low complexity and without local synchronizing signal reconstruction, simultaneously, using normalized correlation processing to resist strong interference, finally, realizing timing fine synchronization with high precision, and correcting receiver integer multiple residual frequency deviation simultaneously. The method can realize timing and synchronization rapidly and accurately in particular in environment with low signal to interference and noise ratio, thereby realizing district searching in a long term evolution wireless communication system. The method can realize downlink timing and synchronization when the signal quality is in the sensitivity position of a terminal receiver and in the environment with strong interference.

A digital cordless telecommunication system capable of maintaining the enhanced frequency stability of radio transmission signals from stationary base stations by use of a specific clock signal including either a high-precision clock or a reference clock as generated by main equipment. In this system the main equipment is provided with a high-precision oscillator that generates and issues a clock signal with increased pulse-phase accuracy, whist a respective one of the base stations is with a line interface for extraction of such high-precision clock signal from the high-precision oscillator, a reference oscillator which supplies a reference clock to a frequency synthesizer that generates a local oscillation signal, a frequency error detector operable to detect a difference or "error" in frequency between the reference clock of the reference oscillator and the high-precision clock of the line interface, and a reference oscillator controller which is responsive to receipt of the error signal from the frequency error detector for adjusting any possible frequency deviation of the reference oscillator causing the reference clock frequency of the reference oscillator to keep track of the frequency of the high-precision clock signal.

The high-accuracy synchronous phasor measurement method belongs to the field of automatic measurement technology of power system. On the basis of spaced sampling circulation DFT, when the system frequency is deviated from rated frequency, the influence of frequency deviation can be calculated to make the frequency and phasor measurement have higher accuracy. The field tests show that when the sampling frequency is 4800 Hz and phasor correction calculation frequency is 200 Hz, its static accuracy indexes are: phasor magnitude error is less than 0.5%, phasor phase angle error is less than 1 deg.C and frequency calculation error is less than 0.01 Hz, and its dynamic accuracy indexes are: phosar magnitude error is less than 1%, phasor phase angle error is less than 1 deg. and frequency calculation error is less than 0.01 Hz.

The invention discloses a strategy for controlling matching of a traditional unit and an energy storage system in an AGC system. The strategy comprises the following steps: obtaining the frequency deviation and the call wire switching power deviation from a data acquisition and supervisory control system, and computing area control deviation; computing system adjustment required power according to the area control deviation; distributing the system adjustment required power to the traditional unit, and computing target output of the traditional unit; computing the largest adjustment capability of the traditional unit in the current AGC period; distributing remaining adjustment power to the energy storage system to be borne; checking and issuing a command, and finishing the current AGC period. The strategy is beneficial to rapidly restraining fluctuation of the frequency of an electric system and fluctuation of the call wire switching power, and can reduce the requirement of the electric system for the frequency modulation capacity, or improve the frequency modulation control effect under the situation that the frequency modulation capacity is changeless. The achieved method is simple, the operation amount is barely added, meanwhile, the requirement for the hardware environment of a control system is low, and larger changes for an existing AGC system is not required.

A method for receiving radio pulse signal includes applying high sampling rate ADC after frequency is mixed under orthogonality and applying flexible and match-correlated master plate being able to regulate adaptively and being set with different shifting positions in digital master plate-match.

A method for reducing current drain in a communication device includes a first step of detecting interference including intermodulation and crossmodulation products. A next step includes determining a frequency offset of the interference with reference to the operating receiver band. A next step includes measuring a power level of the interference. A next step includes calculating a receiver linearity required to achieve a desired signal-to-interference ratio. A next step includes adjusting the receiver linearity in order to achieve the desired signal-to-interference ratio. Optionally, the receiver dynamic range can be adjusted to suit the reduced signal swing due to the reduced linearity.

In an optical transmission system, a multiplexer frequency-division-multiplexes a plurality of signals, and outputs the resultant signal to an FM modulator. The FM modulator converts the frequency-division-multiplexed signal into an FM modulated signal through frequency modulation using the frequency-division-multiplexed signal as an original signal. A frequency-divider converts the FM modulated signal into a frequency-divided FM modulated signal whose frequency is ½n (n is an integer of not less than 1) the frequency of the FM modulated signal. An optical modulator has a predetermined input-voltage vs. output-optical-power characteristic, and is biased at the minimum point (voltage) about the output optical power. The optical modulator modulates an unmodulated light fed from a light source with the applied frequency-divided FM modulated signal to produce an optical signal whose optical carrier component is suppressed, and sends the optical signal to an optical transmission line. An optical receiver receives the optical signal, and square-law detects the signal to convert into an FM modulated signal. A FM demodulator demodulates the FM modulated signal to reproduce the original frequency-division-multiplexed signal. This configuration makes it possible to narrow the bandwidth of an FM modulated signal while increasing the frequency deviation thereof, and realize high-quality signal transmission as a result.

The invention discloses a synchronous realizing method in the orthogonal frequency-division multiplying system, which comprises the following steps: constructing front / synchronous sequence at the transmitting end to frame and transmit; combining the CP information to do one-time synchronization; utilizing front symbol to estimate the integral times and decimal time-domain frequency deviation; compensating the frequency deviation; using front symbol to do secondary time synchronization; proceeding disposal after synchronizing. The invention improves the synchronous precision to modify the system property as well as the received signal-to-noise ratio, which reduces the calculating quantity without adding the burden of system.

A frequency regulation system includes a sensor to detect a power grid signal and a frequency deviation identification module to determine a power grid frequency deviation from the power grid signal. A demand response module identifies an operating schedule for available demand response resources based on frequency deviation set points and ramp rates and a load control module controls the available demand response resources based on the operating schedule.

A detached island effect test method and a device based on active frequency deviation relate to a test method and a device to test distributive new energy grid integration power supply, in particular to a detached island effect test method and a device based on active frequency deviation. Regarding the utility model, 25 cyclic waves form a major cycle. Chopped wave rate cf of the first 15 cyclic waves is 0, and variance trend of the frequency is tested. Under the circumstance that frequency tends to rise, frequency disturbance with the chopped wave rate of cf is added in the grid frequency in the last ten cyclic waves, and initial value cfmax of the chopped wave rate cf is positive. Under the circumstance that the frequency tends to reduce, frequency disturbance with the chopped wave rate of cf is added in the grid frequency in the last ten cyclic waves, and initial value cfmin of the chopped wave rate cf is negative. By adopting the invention, not only the operation probability of the detached island tested is improved; but also testing time is reduced, and current harmonics injected into the grid is reduced.

A system and method for independently controlling the collimation and lateral positioning of a light beam comprises at least one acousto-optic deflector and a pair of counter propagating acoustic waves with offset frequencies. While the frequency offset controls the lateral positioning of the light beam, a frequency gradient across the acousto-optic deflectors controls the collimation of the light beam.

The invention discloses a broadband wireless sensor network transmission scheme based on amplify-and-forward single-node cooperation communication. The scheme is as follows: a source node is firstly used to make an orthogonal space-frequency coding to an original signal, two time slots are respectively used to transmit orthogonal signal frames, then a pilot frequency is inserted and coded signals are subject to IFFT operation to fight against the multi-path attenuation, the coded signals are converted onto a time domain, and the serial data flow is broadcast and sent after the insertion of a cyclic prefix and a training sequence. A first time slot relay node receives signals of the source node, makes frequency deviation and phase compensation, then adopts an amplify-and-forward protocol to synchronously send the processed signals to an information sink node at a second time slot and the source node; an information sink receiver receives a mixed signal from two independent channels, firstly detects a frame head of the signal of the second time slot, then synchronizes with the frame head, then carries out FFT operation to the signal part, converts the signal back to the frequency domain, and performs space-frequency decoding to obtain an original sending symbol. The scheme is simple and easy to operate, can effectively improve the error code rate performance of the system, has strong practicability, and is convenient for the realization of the hardware.

The invention provides a precise time synchronization method for an industrial wireless network, relating to the industrial wireless network communication technology. Aiming at the characteristics of the industrial wireless network, such as limited energy supply, dynamic and variable network environment, the openness of the wireless network media, and the like, the invention provides a unique precise time synchronization method, wherein, a layering and grading synchronization strategy is adopted to divide the industrial wireless network according to a hierarchical structure; an MAC layer of a parent device generates beacon frames, sends the beacon frames periodically, obtains a time stamp in the processes of sending and receiving beacon frames, obtains the frequency deviation and time deviation of the equipment clock and the universal time clock by fitting the time stamps sent and received in most recently N times, compensates the local clock, realizes the time clock synchronization of a child device and the parent device; time synchronization is carried out in a grade-wise manner and finally the time synchronization of the whole network is realized. On the premise of meeting the performance requirements on the industrial wireless network, the precise time synchronization method of the invention can ensure that the whole network runs within a uniform time scale and guarantee the normal operation of the system.

An UKF based channel and carrier wave frequency shift estimation method in OFDM system is applied in the technique field of wireless transmission. Said channel estimation method starts from a frequency domain, to get cursory estimated values at pilot channels firstly by using a LS method, and then to get accurate estimated values by utilizing path capturing method and UKF method in time domain. According to the UKF based carrier wave frequency shift estimation method in OFDM system in accordance with the present invention, wave frequency shift is estimated in time domain through UKF filtering method, and then ICI is eliminated through carrier wave frequency shift correction. Aiming at OFDM system in which disturbances between sub-carriers exist and which passes through time-varying wireless channel, the present invention further provides an UKF based channel and carrier wave frequency combination estimation method which is capable of eliminating ICI and improving veracity of channel estimation and exhibits excellent astringency and robustness by utilizing specific pilot frequency structure and convolutional change forms of a matrix.

The invention provides a coordination control method capable of enabling a super-capacitor energy storage system to participate in electric power primary frequency modulation, wherein the super-capacitor energy storage system is arranged on the bus side of a generator set which needs cooperation. A decision optimizing module obtains a frequency from a synchronous vector measurement unit, and the frequency deviation is obtained through the difference between the frequency and a 50Hz frequency. If the deviation exceeds a frequency dead band, the same motion instructions are simultaneously sent to a traditional generator set and the super-capacitor energy storage system. When the super-capacitor energy storage system participates in primary frequency modulation, the opportunity motion and the motion depth of the super-capacitor energy storage system are determined through the decision optimizing module according to partition of typical working conditions, the conversion from the frequency deviation to the power is achieved through a power-frequency conversion module, the charging / discharging control of the super-capacitor energy storage system is achieved through a PCS control module, and finally the traditional generator set is assisted in participating in the primary frequency modulation process. According to the coordination control scheme, the transient state performance and the steady-state performance of the primary frequency modulation can be obviously improved, frequent starting of the traditional generator set is reduced, and the power system frequency can be rapidly kept stable.

In a system for measuring a time difference of arrival of signals for positioning, an accurate time difference is measured by a receiver which is reduced in power consumption, size, and cost. The system comprises a node (under measurement) for transmitting a positioning signal, a reference station for transmitting a reference signal, and a plurality of access points for receiving the positioning signal and reference signal, and a server connected to the plurality of access points through a network. Each of the plurality of access points measures a time difference between the reception of the positioning signal and the reception of the reference signal, and a frequency deviation from the reference station, using a clock signal and a signal for shifting the clock signal, and the server calculates the position of the node based on the measured time difference and frequency deviation.

A downhole crystal-based clock that is substantially insensitive to the factors that may cause frequency deviation as a result of downhole temperature. The clock may include a plurality of crystals, where a first crystal may be more stable, with respect to temperature, than a second crystal. The crystals may be thermally coupled together so that they may have substantially the same temperature. An error detector may monitor the differences between the frequencies associated with each crystal and provide this information to a storage device. This information may be determined prior to deploying the clock downhole. When deployed downhole, the signal from the error detector may be interpreted in light of the information in the storage device to provide a temperature measurement of the two crystals. The downhole temperature measurement then may be used to reduce frequency deviations in the downhole clock that may result from downhole temperatures.

The invention discloses a digital electrohydraulic control system of a steam turbine with isolated network operation, comprising a control hardware part and a software logical operation part, wherein the control hardware part includes a speed measuring protection part, a one-time frequency modulation module, a servo control module, a man-machine interface part, a control unit and an input / output module; and the software logical operation part includes a first frequency modulation operation and secondary frequency modulation operation unit based on frequency deviation, an overspeed limit unit based on an actual rotating speed measuring signal and a logical judgment unit based on an actual power measuring signal. The control system carries out logical processing and operation on the frequency deviation and outputs a control signal to control an electrohydraulic servo valve through the servo control module to drive a servomotor so as to drive a valve to move, thereby controlling the steam admission quantity of the steam turbine to keep the balance between the output of a steam turbine generator unit and the receiving load of the steam turbine generator unit; in addition, the speed measuring protection part takes an accelerated speed signal as a trigger condition of overspeed limit, thereby effectively limiting the rotating speed overshoot generated by the steam turbine generator unit because of load shedding.

A central site, using grid operator requirements to reduce portfolio power according to frequency decreases within a frequency band, determines the optimal frequency triggers at which each load within a portfolio should reduce power and by how much power. Power availability of each load is optimized. These triggers and individual load power reductions are periodically dispatched from the central site to the individual loads. Each load detects when a frequency deviation occurs and is able to independently and rapidly reduce its power consumption according to the triggers and corresponding power reductions it received previous to the frequency deviation. Reliance upon the central site to detect a frequency deviation and then to dispatch power reductions in real time is not needed. The system also detects frequency increases and directs a portfolio of loads to consume more power. The system applies to energy loads and detection of a grid signal in general.

A downhole crystal-based clock that is substantially insensitive to the factors that may cause frequency deviation as a result of downhole temperature. The clock may include a plurality of crystals, where a first crystal may be more stable, with respect to temperature, than a second crystal. The crystals may be thermally coupled together so that they may have substantially the same temperature. An error detector may monitor the differences between the frequencies associated with each crystal and provide this information to a storage device. This information may be determined prior to deploying the clock downhole. When deployed downhole, the signal from the error detector may be interpreted in light of the information in the storage device to provide a temperature measurement of the two crystals. The downhole temperature measurement then may be used to reduce frequency deviations in the downhole clock that may result from downhole temperatures.

The invention discloses a signal rapid-capturing device and method in the high-dynamic satellite navigational receiver based on segmented mated filter, which comprises the following parts: frequency converter, low-pass filter, extractor, segmented mated filter, envelope calculator, incoherent signal accumulated tester and central controller, wherein the mated filter searches the entire code phase within time T in relative to integral, which obtains a relative result of all code phases under one Doppler frequency deviation to improve signal-to-noise ratio through incoherent signal accumulated tester, in order to judge whether the signal exists; the central frequency is changed by frequency converter to do frequency shaft stepping research. The invention can transmit two-dimensional research on the traditional code phase and Doppler frequency deviation into one-dimensional research on the Doppler frequency deviation, which improves the capture speed of signal greatly to save hardware resource through the design of the segmented mated filter.

The invention discloses a method and corresponding device for taming crystal oscillation frequency of a time-keeping device, which comprises the following steps of: step 1, acquiring the standard time pulse A that is located and output by a navigation satellite; step 2, acquiring the standard time pulse B output by device crystal oscillation fractional frequency; step 3, measuring the clock difference between the standard time pulse A and the standard time pulse B; and step 4, if clock difference exists between A and B, adjusting the crystal oscillation frequency of the device to make the clock difference be in the allowed scope. For the time-keeping equipment with pressure control and temperature compensating crystal oscillation or pressure control crystal oscillation, the frequency deviation of the corrected crystal oscillation can be detected in real time by the method provided by the invention to eliminate the time-keeping error caused by crystal oscillation frequency deviation and avoid accumulation of error. Therefore, the invention is suitable for various satellite navigation systems, such as GPS, Beidou first generation navigation satellite, Beidou second generation navigation satellite, GLONASS, GALILEO and other satellite navigation systems.

The invention provides an information transmission method and apparatus. The information transmission method includes the steps: network equipment determines the frequency deviation information or frequency domain positional information, determines a narrowband for transmitting the transmission information according to the frequency deviation information or frequency domain positional information, and transmits the information on the narrowband. The technical scheme of the information transmission method and apparatus can solve the problem that how to determine the narrowband of a transmission channel on LTE system bandwidth, and can determine the narrowband of the transmission channel.

The invention discloses a synchronous detection device applied to a narrowband wireless communication system terminal. The device comprises a down-sampling module, a sliding autocorrelation module and a difference cross-correlation module. A received 1.92 MHz time-domain signal is subjected to down sampling to a 240 kHz signal through the down-sampling module in terms of OFDM symbol time periods and a fixed down-sampling pattern. Through the sliding autocorrelation module, sampling point data in a 10 ms wireless frame processing window is moved bit by bit as an initial position t, date of which the length is eleven OFDM symbol time periods is taken as a sliding window, and the eleven groups of sample points in the sliding window are correlatively accumulated at intervals of two groups. Through the difference cross-correlation module, an obtained primary synchronizing sequence is subjected to differencing to form two approximately equal parts and is correlatively accumulated with a main synchronizing sequence generated locally. According to the invention, by employing the synchronous detection device, main synchronizing signals are detected well in the narrowband-wireless-communication-system application scenario in which the signal-to-noise ratio is low and the frequency deviation is large, and the implementation complexity is low so that the low-cost requirement of the narrowband wireless communication terminal is met.

The invention belongs to the technical field of digital communication, and in particular relates to a frame synchronization method adopting cross-correlation operation. The frame synchronization method based on sectional cross-correlation provided by the invention increases several arithmetic units used for solving squares of signal modulus; when large carrier frequency deviation exists, a path of correlator is only needed as usual, and a plurality paths of cross-correlators are not needed for the cross-correlation operation on different frequency points; and moreover, after completion of the estimation and compensation on the carrier frequency deviation, the method still can utilize the same arithmetic units for frame synchronization, and accurately estimate a frame start position. Therefore, the sectional cross-correlation method provided by the invention greatly saves the consumption of hardware resources, and improves the utilization rate of the hardware resources.

The invention provides a Doppler velocity metering laser radar echoed signal processing unit and a method. The processing unit mainly comprises a signal storage module and a DSP module; wherein, the signal storage module is used for storing the echoed signals of a tested object; the echoed signals are digital signals which are converted by A / D; the DSP module is used for reading the echoed signals in the signal storage module and carrying out the FFT to obtain the power spectrum of the signals, and then the rough estimated frequency value is obtained according to the power spectrum; the power spectrum is carried out the inverse FFT and then the self correlation functions of the echoed signals are obtained, the correction frequency value is obtained according to the self correlation functions, the rough estimated frequency value and the correction frequency value are added to obtain the Doppler frequency of the echoed signals, and the movement velocity of the tested object is calculated according to the Doppler frequency. The device and the method combine the self correlation technology with the frequency deviation estimation improvement algorithm which is based on the frequency deviation correction, and the velocity of the test object can be effectively worked out.