65 results about "Frequency instability" patented technology

Embodiments of the present invention include control methods employed in multiphase distributed energy storage systems that are located behind utility meters typically located at, but not limited to, medium and large commercial and industrial locations. These distributed energy storage systems can operate semi-autonomously, and can be configured to develop energy control solutions for an electric load location based on various data inputs and communicate these energy control solutions to the distributed energy storage systems. In some embodiments, one or more distributed energy storage systems may be used to absorb and/or deliver power to the electric grid in an effort to provide assistance to or correct for power transmission and distribution problems found on the electric grid outside of an electric load location. In some cases, two or more distributed energy storage systems are used to form a controlled and coordinated response to the problems seen on the electric grid.

PCT No. PCT/AU95/00793 Sec. 371 Date Sep. 30, 1997 Sec. 102(e) Date Sep. 30, 1997 PCT Filed Nov. 28, 1995 PCT Pub. No. WO96/17435 PCT Pub. Date Jun. 6, 1996A Steered Frequency Phase Lock Loop (SFPLL) comprises a phase loop that functions like a normal phase locked loop (PLL) and locks to the input signal, and a frequency loop that uses a reference frequency to influence the phase loop and effectively confines the output frequency of the phase loop and the SFPLL to be in a range of frequencies close to the reference frequency. The reference frequency is chosen to be very close to the input signal frequency that it is desired the SFPLL lock to. The SFPLL comprises a phase detector (10), a frequency detector (22), first and second gain components (12, 24), first, second and third filter components (14, 18, 26), a summer (16) and a voltage controlled oscillator (VCP)(20). By a judicious choice of the gains in the phase and frequency loops the SFPLL can be designed so that the range of frequencies to which the SFPLL will lock can be confined to an arbitrarily small region around the reference frequency ( omega 'r). Applications of the SFPLL include demodulation in CW modulation systems and timing recovery from NRZ data. Three advantages of the SFPLL are that the output frequency is equal or close to the reference frequency when no input signal is present, and the range of frequencies to which the SFPLL can lock is confined to a region around the reference frequency, and the phase and frequency instabilities of the VCO can be reduced.

An adaptive controller for linearization of transmitters using predistortion of the input signal has reduced sensitivity to impairments such as gain variation, phase noise or modulation/demodulation frequency instability by linearizing an adaptively normalized gain provided through a separate estimation and cancellation of linear gain variations. Values of a nonlinear and a linear gain blocks, cascaded with the linearized transmitter and called respectively a predistortion block and a gain regulation block, are independently adjusted by two different adaptive controllers. In one embodiment, four banks of real gain elements compose the predistortion block and realize an arbitrary step-wise approximation of a generalized 2×2 transmit gain matrix of nonlinear functions. In a further embodiment cancellation of a DC level bias multi-channel impairment is provided by an adaptively adjusted signal adder inserted in the transmit chain between the predistortion block and the linearized transmitter.

The invention relates to a measuring device of the noise characteristics of laser, consisting of a conversion system of noise fluctuation of the laser and a detecting and processing system. The measuring device mainly comprises a circulator, a 3*3 coupler, a first photoswitch, a second photoswitch, optical fiber, a first Faraday rotation reflector, a second Faraday rotation reflector, a frequencyshifter, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector, a fourth photoelectric detector, a data acquisition card and a computer. The measuring devicedisclosed by the invention has the capability of simultaneously measuring the noise characteristics comprising the intense noise power spectral density, the phase noise power spectral density, the frequency noise power spectral density, the line width and the Allen variance with frequency instability, of the laser, has the characteristics of high integration level and simpler and more concise structure, has no any limitation to the laser to be measured without an extra active control measure, thereby increasing the measuring reliability of the noise characteristics of the laser.

The invention discloses an emergency and precise load shedding control system and method based on distributed feeder line automation. The emergency and precise load shedding control system comprises a regional power grid frequency control master station, a load shedding control master station, multiple load shedding control substations, multiple load shedding executing stations and a distributed feeder line automation subsystem. The distributed feeder line automation subsystem comprises multiple power supply stations provided with 10kV feeder lines and distributed feeder line terminals of distribution network branch circuits. The emergency and precise load shedding control system and system applies a hierarchical self-governing thought to calculate load shedding capacity layer by layer, position the capacity to the bottom-layer feeder line terminals and complete matching of required load shedding capacity and actual load shedding capacity. In addition, a centralized load shedding control thought using a 110kV line as an object of a traditional power grid safety stable-control device is changed, while 10kV interruptible load is used as a load shedding control object, millisecond-class precise load shedding control of a large-scale 10kV distribution network layer is achieved, the problem that the 110kV centralized load shedding is insufficient or excessive is solved, the problem of frequency instability after bipolar locking breakdown of multiple direct current receiving-end power grids can be relieved, and safe and stable operation of large power grids is ensured.

A method of controlling a wind power plant, the wind power plant having a plurality of wind turbines and being connected to a power grid is provided. The method includes (a) detecting a grid frequency instability, (b) selecting a subset of wind turbines, (c) modifying a power reference for each wind turbine in the selected subset of wind turbines to respond to the grid frequency instability, and (d) applying the modified power references to the corresponding wind turbines in the selected subset of wind turbines. A wind power plant controller, a wind power plant, a computer program, and a computer program product are also provided.

The invention discloses a multi-control-surface aircraft modal calculation and verification method. An aircraft control surface transmission mechanism finite element model is established with an equivalent-rigidity method, a full-aircraft finite element model is established with a finite element model assembly method, and main modal characteristics of an aircraft are predicted; a stepping sine scanning method is adopted for carrying out modal tests for verification, and the problem that in a multi-control-surface aircraft modal test, because connecting gaps exist between control surface mechanisms, modal stability is influenced is solved. A control surface loading method is adopted in the method, control surface mechanical gaps are eliminated, and modal frequency instability and modal resonance instability are eliminated. The method effectively verifies scientificity of a modal prediction method, and meanwhile, the modal instability is effectively eliminated through the control surface gradual loading method.

An acoustic wave sensing apparatus includes a substrate having a polished piezoelectric surface. An acoustic wave sensing device (filter, resonator, or delay line) is generally configured from the substrate, such that the polished piezoelectric surface is attachable to a polished metal shaft utilizing an adhesive that reduces hysteresis and creep and improves the performance of the acoustic wave sensing device. The metal shaft is preferably polished in order to reduce the localized stress and contact area associated with the piezoelectric surface of the acoustic wave sensing device and the metal shaft. The adhesive can be implemented as an epoxy adhesive that avoids direct-contact induced frequency instability associated with the contact area.

The invention relates to a wind fire bundling system control device and a method thereof. The method includes the following steps that a direct current emergency frequency control strategy is made aiming at wind fire bundling system frequency stability problems under two conditions of wind power plant power fluctuation and fault shutdown respectively; when a wind power plant runs normally, high wind power fluctuation can cause frequency instability easily, direct current double-side frequency modulation is utilized as the emergency control, and the thermal power generating unit frequency modulation is utilized as the auxiliary strategy; when the wind power plant runs abnormally, the wind power plant fault shutdown can cause frequency temporary state instability easily, a direct current emergency lifting/dropping control strategy is provided, and the thermal power generating frequency modulation fluctuation is utilized as the auxiliary strategy. The device and the method meet the frequency modulation requirement of a wind fire bundling direct current islet outgoing system, can effectively solve the wind fire bundling sending end system frequency stability problem caused by wind power fluctuation and wind power plant fault shutdown, avoids action of the wind power plant or a thermal power generating unit protection device, and improves system operation reliability.

The invention provides an equal-arm-length heterodyne laser interferometry ranging system at least comprising a vibration isolation system, a vacuum system, a light source system, an interference system, and a phase monitoring and data analysis system. The vibration isolation system is used for isolating and filtering external low-frequency noise to eliminate system vibration noise. The vacuum system is used for reducing thermal noise caused by system temperature fluctuation. The light source system is used for providing two high-stability high-stable-frequency laser beams which have corresponding differential frequencies. The interference system is used for generating two equal-arm-length heterodyne interference signals and acquiring the information of displacement change between two tested objects according to the displacement and phase relationship. The phase monitoring and data analysis system is used for phase detection for the interference signals, acquiring phase information, inverting displacement, and indicating ranging precision of the interference system under each frequency. The equal-arm-length heterodyne laser interferometry ranging system has the advantages that frequency instability of the laser can be eliminated, the influence of various noise sources upon the ranging precision can be eliminated, and long-period picometer-level measurement precision is realized.

The invention discloses a receiving end power grid phase modifier dispatching method considering short-circuit current and system frequency voltage risks, and belongs to the technical field of electric power systems and automation thereof. During direct-current long-term non-full-power operation, receiving end power grid frequency voltage risks are greatly reduced than risks during direct-currentfull-power operation, and possibility is provided for exiting a phase modifier. System frequency instability risks generated after the phase modifier on a direct-current inverter side exits are quantitatively evaluated, a voltage instability risk index of the product of a voltage weak region power receiving rate and a voltage instability fault set change after the phase modifier exits is defined,and a comprehensive scheduling sequence and strategies of exiting the phase modifier under a typical operation mode are obtained by considering contributions of phase modifier exiting to the short-circuit current and maintenance loss cost. By means of the method, power system planning operation personnel can control safe stable operation risks of alternating-current and direct-current power gridsafter exiting the phase modifier in advance easily, and the flexibility of operation mode arrangement is improved.

The invention provides a large-scale energy storage and permanent magnet wind power generation coordination control system and a method thereof, wherein the system comprises a direct-drive permanent magnet wind power generator, a machine side converter, a machine side converter control system, a machine side torque controller, a network side converter, a network side converter control system, a large-scale energy storage and control system, a battery management system and a double coordination control layer; according to the method, the rotational kinetic energy stored in a turbine blade is released, staged inertia control is provided through a torque limit curve, the problem of frequency instability caused by the fact that a wind power plant is connected to a power grid is solved, and temporary adjustment of system frequency is achieved; wind energy captured by the blades is utilized, and the DC-DC controller realizes bidirectional energy circulation; an energy storage system and a wind power generation system are coordinated and controlled, the problem of secondary frequency reduction is solved, the rotor speed recovery of the wind power generator is accelerated, the temporary frequency modulation capacity and the system inertia response capacity are improved, and the power grid fluctuation caused by wind power generation is stabilized to the maximum extent; and a energy storage unit is kept in a reasonable operation range.

A Time-Average-Frequency direct period synthesizer is used to improve crystal-less frequency generator's frequency stability. It includes (a) a temperature sensor circuit to compensate temperature-induced frequency instability; (b) a voltage sensor circuit to compensate voltage-induced frequency instability; (c) a calibration circuit to correct manufacture-related frequency error; (d) a frequency control word update circuit to receive the temperature- and voltage-related frequency adjustments, and the calibration-related adjustment, to generate the corresponding frequency control word in a predetermined schedule; (f) a Time-Average-Frequency direct period synthesizer to receive said frequency control word in the predetermined schedule and produce a clock signal with a frequency that is stable and accurate by counteracting the frequency variation caused by crystal-less oscillators' temperature and voltage dependence and correcting the frequency error introduced in manufacture process. Methods of correcting crystal-less oscillators' frequency error and compensating its frequency variation are also disclosed.

The invention discloses an ultra-high-voltage AC/DC hybrid grid stability analysis method based on risk assessment in the technical field of electric power system reliability. The method, on the basis of reasonably setting system fault and carrying out analog simulation, introduces risk assessment indexes, comprising important components of low-voltage risk, power angle difference risk and frequency instability risk and the like. The method is characterized by, after determining a component outage model, selecting system failure states and calculating probability thereof; carrying out simulated assessment on the consequence of each selected state; and finally, calculating risk indexes and analyzing stability of a power grid. Compared with a conventional power grid stability analysis method, the method combines the accident occurring probability and the consequence of each index loss and combines risk and benefit, and quantitatively reflects system safety indexes, so that the method is more suitable for stability analysis of a complex hybrid grid when having cascading failure or large-area blackout.

The invention provides a power system dispatching operation method and system considering a synchronous rotation inertia level, and belongs to the technical field of electric power system operation. The method comprises the following steps: firstly, establishing a power system dispatching operation model considering the synchronous rotation inertia level, and then linearizing a frequency responsecharacteristic function by adopting a piecewise linearization algorithm to obtain a linearization coefficient of a frequency safety constraint in the model; and solving the model to obtain an optimaldispatching operation result of the power system. According to the method, the problem of frequency stability of the power system caused by high-proportion renewable grid connection can be relieved, the synchronous rotation inertia level of the power system is maintained, the risk of frequency instability caused by access of a large number of renewable energy sources is reduced, and the safety andreliability of the power system under large disturbance are improved.

A transient stable control method for power system with superconductive energy-stroage device pertains to a transient stable control technique field based on current type inverter in a power system, characterized in that it puts forward a power system dynamic model with superconductive energy-stroage device; it obtains a robust control model of this system by leading into an external interference, then uses a linearization method and a linear H>=[infinity] control theory to restraint the external interference on the foundation that concerns the nonlinear essence in the system; and it may greatly raise transmission limit of the power system and its safety, strengthens transient stability of the systemat, and decreases the frequency instability of the power system or the accident of voltage collapse induced by a fault or other reason.

The invention provides a grid connected inverter power distributing method based on virtual synchronous control to mainly solve the problem that the classical droop control strategy can not effectively improve the stability of a system when the voltage and frequency of the grid fluctuate greatly and the capacity of an inverter is insufficient. A constant-speed regulation mode is employed by taking into account the frequency instability and voltage instability of the power grid, so that the speed of frequency and voltage instability trend is consistent. Excessively fast voltage instability due to excessive inverter active power compensation and excessively fast frequency instability due to excessive reactive compensation can be prevented, thereby prolonging the relative time length of power grid instability. Compared with a classic control method, the control method can effective improve the stability of a power grid, and ensure safety and stability of the power grid.

The invention provides an MEMS piezoresistive resonator which comprises a substrate, input electrodes, an input offset voltage electrode, output electrodes, a first anchor structure, a second anchor structure and a vibrator. The input electrodes are used for providing AC voltage signals for the vibrator so as to enable the vibrator to vibrate. The input offset voltage electrode is formed on the substrate and located on a vibrating wave node portion and is used for providing DC offset voltage signals for the vibrator so as to enable the sensing current to flow through the vibrator, wherein the sensing current is generated by resistance change of the vibrator due to response to the AC voltage signals. The output electrodes are located on the vibrating wave node portion and arranged opposite to the input offset voltage electrode and is used for responding to the sensing current and outputting frequency signals. The first anchor structure is used for sending the DC offset voltage signals to the vibrator. The second anchor structure is used for sending the sensing current to the output electrodes. The vibrator is arranged between the input electrodes and suspended above the substrate through the first anchor structure and the second anchor structure. The vibrator comprises a first region and a second region, wherein the sensing current flows through the first region and does not flow through the second region, so frequency instability caused by spontaneous heating can be reduced.

The invention provides a wideband linear frequency modulated microwave signal generator. A voltage controlled oscillator generates linear frequency modulated signals; the linear frequency modulated signals are divided into three paths through a power divider, wherein the A path of signals are outputted directly, the B path of signals are directly inputted into the first input port of a frequency mixer, and the C path of signals are subjected to time delay of a delay line and then are inputted into the second input port of the frequency mixer; the output signals of the frequency mixer are subjected to analog-to-digital conversion, so that digital signals can be generated; the digital signals are inputted into an FPGA signal processing module for analysis and processing, so that fine modulating signals in a digital form are generated; the fine modulating signals are subjected to digital-to-analog conversion, so that fine modulating signals in an analog form can be generated; and the fine modulating signals in the analog form are inputted into the voltage controlled oscillator so as to control the frequency of the output signals of the voltage controlled oscillator. According to the wideband linear frequency modulated microwave signal generator of the invention, the advantage of large bandwidth of an original analog technology is reserved, and by means of the powerful data processing ability of an FPGA, a feedback loop is built, and therefore, the defects of frequency instability and poor linearity of a traditional analog method can be eliminated.

The invention discloses an energy dissipation system applied to a flexible direct current power transmission system. The energy dissipation system is composed of an electronic power switch and a loadresistor, and the electronic power switch and the load resistor are connected in series to an alternating current power grid of a rectifier side of a flexible direct current power transmission system.The invention also provides a corresponding control method. The energy dissipation system is used for consuming transient energy accumulation caused by faults of the flexible direct current power transmission system, prevents overvoltage of a power module of the flexible direct current power transmission system, and also prevents frequency instability and voltage instability of an alternating current system.

The invention discloses a range hood. The range hood comprises a fan system, a control module and a motor driving module which drives the fan system according to a signal of the control module; the fan system comprises a motor; the motor is a direct current motor; the range hood is characterized by further comprising a sound sensor used for acquiring a sound signal of the range hood and a vibration sensor used for acquiring a vibration signal of the motor; and the vibration sensor and the sound sensor are both connected to the control module. The invention further discloses a resonance abnormal noise eliminating method of the range hood. Compared with the prior art, the range hood and the resonance abnormal noise eliminating method thereof have the advantages that the working state of therange hood is identified through cooperative work of the vibration sensor and the sound sensor, and resonance abnormal noise of the range hood is eliminated by changing the rotating speed of the direct current motor by means of changing a current value in a failure state of the resonance abnormal noise; and the range hood and the resonance abnormal noise eliminating method thereof have very good adaptability to the problem of inherent frequency instability caused by indetermination of back pressure and process problems.