397results about How to "Harmonic suppression" patented technology

A harmonic cantilever for use in a tapping-mode atomic force microscope includes a cantilever arm and a probe tip. The cantilever arm has a shape selected to tune the fundamental resonance frequency or a resonance frequency of a selected higher order mode so that the fundamental and higher-order resonance frequencies have an integer ratio or near integer ratio. In one embodiment, the cantilever arm can be shaped to tune the fundamental resonance frequency. Alternately, the cantilever arm can include a geometric feature for tuning the resonance frequency of the fundamental mode or the selected higher order mode. An imaging method using the harmonic cantilever is disclosed whereby signals at the higher harmonics are measured to determine the material properties of a sample. In other embodiment, a cantilever includes a probe tip positioned at a location of minimum displacement of unwanted harmonics for suppressing signals associated with the unwanted harmonics.

Systems and methods of identifying molecules of polymers such as, for example, a nucleic acid, are described. The method involves centering a bias voltage across a pair of nano-electrodes separated by a channel that corresponds to one of any of the energy differences between any two internal energy levels of a molecule of interest, and modulating the bias voltage with a modulation waveform while the molecule of interest is in the channel. An electrical signal characteristic of the molecule of interest is derived from the tunneling current between the nano-electrodes, and the characteristic electrical signal is compared with known values of the signal for chemically-known molecules in order to identify the molecule of interest. Multiple pairs of nano-electrodes may be employed to identify more reliably a single molecule or multiple molecules.

A circuit for frequency translating a radio frequency signal comprises a plurality of mixer stages, each stage associated with a particular range of frequencies of a radio frequency signal. The circuit further comprises a switching circuit that communicates the radio frequency signal to a selected one of the plurality of mixer stages in response to a control signal. The selected mixer stage comprises a phase generation circuit that generates a plurality of phase signals, and at least one mixer that combines the radio frequency signal with one of the plurality of phase signals to generate at least a portion of an intermediate frequency signal.

The invention belongs to the technical field of controlling of power converters of driving motors, and relates to a current control method for improving the output torque of a permanent magnet synchronous motor overmodulation area. The method includes the steps that a PI controller is adopted to a rotating speed loop; a current controller based on resonance control is used for a dq shaft electric current loop, and parameter setting is carried out on the current controller; the PI controller is adopted in a field-weakening control link, and output of the PI controller serves as a d shaft current set value through an amplitude limiting link; according to set voltage vector dq shaft components output by the current controller, the duty ratio is calculated through an SVPWM overmodulation link, and a PWM signal driving motor is produced. The method suppresses current harmonics caused by flux weakening overmodulation, open-loop gains of the current loop are increased, and current, harmonic and torque fluctuation caused by overmodulation can be effectively suppressed.

A magnetic particle imaging apparatus includes magnets [106,107] that produce a gradient magnetic field having a field free region (FFR), excitation field electromagnets [102,114] that produce a radiofrequency magnetic field within the field free region, high-Q receiving coils [112] that detect a response of magnetic particles in the field free region to the excitation field. Field translation electromagnets create a homogeneous magnetic field displacing the field-free region through the field of view (FOV) allowing the imaging region to be scanned to optimize scan time, scanning power, amplifier heating, SAR, dB / dt, and / or slew rate. Efficient multi-resolution scanning techniques are also provided. Intermodulated low and radio-frequency excitation signals are processed to produce an image of a distribution of the magnetic nanoparticles within the imaging region. A single composite image is computed using deconvolution of multiple signals at different harmonics.

An antenna for suppressing harmonics of a signal transmitted from the antenna, the signal having a carrier with an imposed modulated data signal, the antenna including a modulator associated with a controlled variable impedance in series, the modulator being operable to modulate in accordance with the data signal, and being configured to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

The invention relates to an LED (Light Emitting Diode) illumination intelligent control system which comprises a synchronous rectification unit used for providing direct-current power for at least two intelligent power control units, wherein the output end of each intelligent power control unit is connected with a corresponding LED light group unit via an electric wire; and the synchronous rectification unit is connected with each intelligent power control unit by a high-voltage direct-current bus. In the intelligent control system, stable constant-voltage direct current is provided for an LED illumination system by the synchronous rectification unit, so that the whole illumination system can operate under high power factor with less harmonic wave. the corresponding LED light group units are dynamically and precisely dimmed by the intelligent power control units, and the LED operation situation is detected in real time and communication with an external control center is carried out. The intelligent control system has the characteristic of reasonable structure, and is convenient to control, the working environment temperature of an LED light group can be improved, and the reliability and the service life of an LED illumination light can be improved.

The invention relates to an asynchronous starting permanent magnet synchronous motor rotor based on permanent magnets with different residual magnetic densities, and belongs to the field of permanent magnet motors. The asynchronous starting permanent magnet synchronous motor rotor comprises a rotating shaft, a starting cage, a rotor iron core and the permanent magnets, wherein 2p VVV-shaped permanent magnet slots encircling the rotating shaft are uniformly formed in the rotor iron core; a first permanent magnet and a second permanent magnet are arranged in a first V-shaped slot; a third permanent magnet and a fourth permanent magnet are arranged in a second V-shaped slot; a fifth permanent magnet and a sixth permanent magnet are arranged in a third V-shaped slot; and magnetism isolation slots are reserved between the permanent magnets. On the premise that the stable-state running performance is not reduced, the cost of an asynchronous starting permanent magnet synchronous motor is effectively reduced, and the no-load air gap magnetic density waveform sine distortion rate is reduced; harmonic waves are effectively suppressed; the efficiency of the motor is improved; the torque ripple is reduced; and the vibration noise is reduced.

The invention relates to a remote meter reading system, which adopts meter reading modules provided with electric energy metering chips; the voltage, the frequency, the active power, the power and the like can be measured, calculated and stored on the premise of inhibiting the harmonic waves and preventing the impact of overcurrent on the system; the data is processed under the control of a microprocessor and is then sent to a superior system. Meanwhile, respective meter reading modules form a sensor node for wireless networking, so that the integrated uploading of the data can be realized; the system maintenance, the fault overhaul and the expansion are easier. Finally, terminal electricity meter data is stored into a main database server; special system software is matched; the functions of automatic meter reading, data processing, information analysis statistics and the like are realized.

A power converter includes a rectifier section, an inverter section, a capacitance element connected between inverter section input ends, an inductance element forming part of an LC filter with the capacitance element, a voltage detector detecting an inductance element voltage, and a controller controlling the inverter section based on the detected voltage. The LC filter has a resonance frequency set such that ripple current components contained in DC current outputted from the rectifier section passes through, and current components of a frequency equal to a carrier frequency of the inverter section are dampened. The controller controls the inverter section so that a transfer characteristic of input voltage of the inverter section versus the DC voltage from the rectifier section becomes a damping characteristic given by a phase lead element and a second-order lag element connected in series, and a damping coefficient of the transfer characteristic is set larger than 1.

The invention provides a test platform for large energy storage converters, comprising an energy storage converter connected with an upper computer monitoring system. The input end and the output end of the energy storage converter are respectively connected with a power grid through a battery simulation system and an anti-islanding detection device. An energy storage converter detection device is connected across the two ends of the energy storage converter. The battery simulation system includes an energy management device. Compared with the prior art, the test platform for large energy storage converters, provided by the invention, is strong in applicability and stable in performance and can effectively improve the test accuracy of electric performance and grid connection performance of large energy storage converters.

The invention relates to an electric power electronic transformer applied to a distribution network, which is divided into an input level, an isolation level and an output level. The isolation level uses a power converter with a bridge topology structure to adapt to the requirement of different voltage levels of input; the isolation level uses a form that a plurality of high-frequency transformers respectively carry out isolation, transformation and energy transmission; and the output level has two topology structures, wherein the first structure is formed by parallel connection of the power converter with the bridge topology structure, and the second structure is formed by cascade connection of the power converter with the bridge topology structure, and simultaneously an LC wave filter is connected to improve the voltage-current waveform quality. The complete appliance totally uses mature power devices, is formed by combining basic power units and can be flexibly applied to distribution network lines with different voltage levels. The transformer can automatically regulate line output voltage to stably output voltage, thereby inhibiting voltage quality problems of voltage falling, rising as well as flickering, overvoltage, undervoltage and the like.

The invention relates to a voltage unbalanced mathematical model-based control strategy for a brushless double-feed motor grid-side converter. Unbalanced voltage vectors are decomposed into balanced positive sequence components, negative sequence components and zero sequence components by utilizing a symmetrical component method; a mathematical model of the grid-side converter is created when the voltage is unbalanced; and the problems of coupling terms and external disturbance existing in the grid-side converter are observed and compensated by utilizing an expansion state observer and a self anti-interference control theory. A nonlinear control method designed in the invention can inhibit the harmonic wave problem of the grid-side converter under the voltage unbalanced condition very well, and has the advantages of strong anti-interference capability, favorable robustness, and the like.

The invention discloses a voltage and power regulator based on the composite energy storage of a storage battery and a super capacitor. The regulator comprises an energy storage module, an electricity-electron transformation module and a transformer; the energy storage module comprises a plurality of composite energy storage units and the electricity-electron transformation module comprises a plurality of electricity-electron transformers; all the composite energy storage units are connected at the direct current bus side of the electricity-electron transformers in parallel and the alternating current side of each electricity-electron transformer is connected with the auxiliary-side winding of a voltage transformer correspondingly while the original-side winding thereof is connected into a power network. When in normal operation, the regulator can provide reactive power compensation for the power network to effectively stabilize the active power fluctuation; when failure or switching load transmission operation occurs in the power supply line, the regulator provides short-time power supply for load so as to avoid load power supply interruption and further rapidly traces the voltage magnitude and phase of spare lines, thereby realizing that no impact is made in a spare power circuit.

A front end circuit and a wireless communication device capable of achieving matching with an antenna across a wide frequency band and capable of suppressing degradation in high-frequency characteristics caused by the influence of transmission signal harmonics is provided. A front end circuit includes a variable matching circuit connected to a low-frequency band transmission port side of a diplexer and a harmonic filter connected between the variable matching circuit and the diplexer. The harmonic filter has a pass band that overlaps with a low-frequency band-side communication band and a stop band that overlaps with a harmonic frequency of the low-frequency band-side communication band.

The invention relates to a 60-degree coordinate system-based three-phase VIENNA rectifier and a control method, and specifically relates to a three-level VIENNA rectifier and a control method thereof. The invention aims to solve the problems of low power grid power factor, high grid side harmonic component and poor system stability in the prior art. The 60-degree coordinate system-based three-phase VIENNA rectifier includes an inductor group, a main circuit, a DSP control system, a drive module, a grid side voltage signal processing circuit, a grid side current signal processing circuit, a direct voltage sampling module and a load, the inductor group includes a first inductor, a second inductor and a third inductor, the main circuit includes a three-phase VIENNA rectifier circuit, a power grid is connected with an input end of the three-phase VIENNA rectifier circuit through the first inductor, the second inductor and the third inductor, and an output end of the three-phase VIENNA rectifier circuit is connected with the load. The device and the method provided by the invention improve the power factor of the power grid, improve system response speed, and enhance system stability.

The invention discloses a dual-frequency receiving antenna and a dual-frequency rectifying antenna. The dual-frequency receiving antenna and the dual-frequency rectifying antenna are used for solving the problems that an existing dual-frequency receiving antenna is large in size and small in gain, an existing dual-frequency rectifying antenna is large in size, can not receive weak energy and is not suitable for remote transmission, and a rectifying circuit is poor in reliability. The dual-frequency receiving antenna comprises a rectangular radiating patch. A Z-type groove used for achieving dual-frequency characteristics is formed in the radiation patch. The lower end of the radiation patch is sequentially connected with a dielectric substrate layer and a metal earth plate through a coaxial line. The coaxial line is in circuit connection with the rear end of the radiation patch. An air dielectric layer is formed between the radiation patch and the dielectric substrate layer. The portions, arranged between the radiation patch and the dielectric substrate layer, outside the coaxial line are provided with metal sheets in a bilaterally-symmetric mode. The upper ends of the metal sheets are connected with the radiation patch. The lower ends of the metal sheets are connected with the dielectric substrate layer. One end face of the radiation patch is further connected with the metal sheets connected with the dielectric substrate layer. The dual-frequency receiving antenna and the dual-frequency rectifying antenna can be widely applied in the fields of communication, medical treatment, industry and the like, for microwave power transmission.

An analogue-to-digital converter includes a summing element for combining an analogue input signal of the analogue-to-digital converter with a feedback signal in order to generate a fault signal, a quantizer which has comparators for comparing the fault signal with reference voltages in order to generate a digital output signal, a digital-to-analogue converter for converting the digital output signal into the feedback signal, a control device for generating a control signal from the digital output signal in order to control the use of elements of the digital-to-analogue converter in such a way that mismatching of the elements is compensated, a random number generating device for generating random numbers which are used in the quantizer to interchange the assignment of the reference voltages to the comparators in order to eliminate an effect of offset voltages at inputs of the comparators, and a compensation device for generating a compensated control signal from the control signal as a function of the random numbers in order to compensate the interchanging of the assignment of the reference voltages.

The invention relates to an inverter parallel control method based on controllable virtual impedance. The method comprises the steps that (S1) datum reference frequency omega co and a feedback inverter capacitor voltage Vfil generate a reference voltage amplitude angle theta i through a phase-locked loop module; (S2) a reference voltage Vref is obtained through the reference voltage amplitude angle theta i and a datum reference amplitude Eco; (3) state quantity J(s) is obtained after the feedback inverter capacitor voltage Vfil is subtracted from the reference voltage Vref through a PI controller; (S4) after an output current feedforward value beta Isp is subtracted from the state quantity J(s), feedback compensation is carried out through the inverter capacitor voltage, and a current Ip is then obtained through a P controller; (S5) after an output current Isp is subtracted from the current Ip, the inverter capacitor voltage Vfil is obtained through a filter controller; (S6) equivalent virtual impedance Z0 is obtained, output impedance is adjusted according to a formula, and output currents of multiple parallel inverters are made to be balanced. Compared with the prior art, the output impedance of the inverters is accurate and controllable, and balanced operation of the inverters of a parallel system is achieved.

The invention provides a power-frequency online anti-icing de-icing method for an electrified railway contact network. The method comprises the steps as follows: A, the head end and the tail end of any power-supply arm of an electrified railway traction substation are respectively connected with a head-end dynamic reactive compensation device and a tail-end dynamic reactive compensation device; and a temperature sensor is arranged on a contact network and connected with a controller of the head-end dynamic reactive compensation device and the tail-end dynamic reactive compensation device; and B, the temperature sensor monitors the temperature of the contact network, and when the detected temperature is lower than 0 DEG C, the controller controls the head-end and the tail-end dynamic reactive compensation devices to enter into an anti-icing de-icing working state and specific current is generated on a contact net for anti-icing and de-icing. The method is used to carry out automatic online anti-icing and de-icing under the condition that the railway is in a continuous running state and the power supply is not influenced, so that the contact network is not frozen in freezing rain, ice and snow and extreme weathers, thereby ensuring the safety of train operation.

The invention discloses a brushless double-feedback motor of a winding rotor, which belongs to winding rotor motors. The problems of low slot space utilization rate, effective conductor utilization rate of a rotor winding and winding coefficient of a traditional brushless double-feedback motor of the winding rotor are solved. A power winding and a control winding which are mutually independent are arranged on a stator; Z rotor slots and m phase rotor windings are distributed on a rotor core; each phase rotor winding is provided with a parallel branches; each parallel branch consists of two or three coil groups; first, second and third pitches which are different are respectively adopted in coils with different turn numbers in the first, second and third coil groups; the coils in each coil group are connected in series; and each coil group is in short-circuit connection. The turn number of each winding coil can be flexibly adjusted; the slot space utilization rate, the effective conductor utilization rate of the rotor winding and the winding coefficient can be improved by 5 to 15 percent; and other harmonic waves are inhibited and the content of the harmonic waves is reduced to the maximal degree.

The invention discloses an integrated device of high efficiency photovoltaic grid-connection and hybrid active power filter, belonging to the technical fields of the electrical engineering and the solar photovoltaic utilization. The integrated device is basically characterized in that: through utilizing solar battery array, the device absorbs sunshine energy and converts the sunshine energy into electric energy, then changes the electric energy into alternating current through a power converter, and the alternating current is transferred to a power network through a passive power filter formed by inductance and capacitance after filtered by a low pass filter. The passive power filter and a photovoltaic grid-connection inverter are connected in series, the passive power filter bears primary fundamental voltage, the voltage of the direct current side of the photovoltaic grid-connection inverter is very low, thus a photovoltaic array can be directly connected with the photovoltaic grid-connection inverter without a boosted circuit, the generating efficiency of the photovoltaic grid-connection is improved. In addition, the integrated device of high efficiency photovoltaic grid-connection and hybrid active power filter also has the functions of an active power filter at the same time, makes the power network carry out reactive power compensation and controls the harmonic of the power network, reduces the power network loss and improves the quality of power supply. The integrated device of high efficiency photovoltaic grid-connection and hybrid active power filter has the advantages of simple structure, high efficiency and multi-function.

The invention discloses a harmonic and inter-harmonic separation detecting method and device suitable for a vessel electric power system, and belongs to the technical field of vessel electrical engineering. The device comprises a voltage transducer, a current sensor, a chassis wiring terminal, a signal conditioning circuit, a data acquisition card and an industrial control computer, wherein the wiring terminal, the data acquisition card and the signal conditioning circuit are mounted inside the industrial control computer; the industrial control computer acquires input data through a standard serial port, and LabVIEW software of a virtual instrument is used for restoring collected signals according to the transformation ratio, and original signals are recorded; the comprehensive detection on parameters such as frequency, amplitude value and phase of fundamental wave, harmonic and inter-harmonic can be completed; the detection result can be directly displayed on the liquid crystal display of the industrial control computer. According to the invention, a frequency tracking algorithm, a fundamental wave and harmonic extraction algorithm and an inter-harmonic detection algorithm are adopted to implement the fundamental wave, harmonic and inter-harmonic separation detection.

The invention discloses a reactive capacitance compensation cabinet which comprises a cabinet body, wherein the cabinet body is internally provided with a plurality of three-phase compensation units, a plurality of split phase compensation units, a breaker and a controller; each the three-phase compensation unit comprises three compensation single-phase circuits; the compensation single-phase circuits comprise fuses, reactors, switching switches and capacitors that are electrically connected sequentially; the three compensation single-phase circuits adopt delta connection; each split phase compensation unit comprises three split compensation single-phase circuits; the three split compensation single-phase circuits adopt star connection; the three-phase compensation units and the split phase compensation units are connected with an outside three-phrase power grid by the breaker; the switching switches are connected with the controller; and the controller is connected with a detection unit for detecting current signals and voltage signals of the three-phrase power grid. The compensation cabinet combines three-phase compensation and split phase compensation, and can conduct intelligent switching conversion and automatic combined configuration, and inhibit and filter harmonic waves.

A power factor correction converter includes a diode bridge that rectifies an alternating-current voltage input from an alternating-current input power supply Vac, a series circuit including an inductor and a switching element, a rectifying smoothing circuit connected in parallel with the switching element and including a diode and a smoothing capacitor, and a digital signal processing circuit that controls turning on and off of the switching element such that the input current input from the alternating-current input power supply Vac comes to have a similar shape to the alternating-current voltage. The current flowing through the inductor in the off period of the switching element is detected by using a current detection resistor, the operation mode is determined on the basis of the inductor current IL at a predetermined timing and the switching element is optimally controlled in accordance with the operation mode.

The invention provides a micro-grid inverter control method based on an improved virtual synchronous generator, which relates to the technical field of micro-grid inverter control. The method includesthe following steps: collecting the output parameters of a micro-grid inverter, converting the output parameters into corresponding values under a d-q coordinate system, and obtaining a mathematicalmodel of the micro-grid inverter under the d-q coordinate system; calculating the active power and reactive power output by the micro-grid inverter; using a virtual speed governor and a virtual excitation regulator to obtain the virtual mechanical power and terminal voltage of a virtual synchronous generator; obtaining a reference voltage through an improved VSG rotational inertia control algorithm; and finally, using the obtained reference voltage as the input of an improved voltage and current loop, and outputting a pulse width modulation signal to drive a power device of the micro-grid inverter so as to control the micro-grid inverter. The micro-grid inverter control method based on an improved virtual synchronous generator provided by the invention enables a micro-grid inverter under islanded operation conditions to have the ability to support the grid voltage stability and make fast frequency response.