126 results about "Harmonic order" patented technology

The invention discloses a harmonic wave detection method based on Fourier transformation, comprising the following steps: (1) carrying out oversampling and analog-to-digital conversion on a measured signal, and ensuring that data of two signal periods can be sampled from each group of data according to the maximum periodic value estimated by the measured signal; (2) filtering harmonic wave components outside fundamental waves by a digital low pass filter; (3) calculating a fundamental wave period by a periodic method; (4) extracting 2*N numbered data points within one period, wherein, N-1 is the highest harmonic order number; and (5) calculating the parameter of each harmonic wave component by utilizing a synchronous sample FFT. The method of the invention belongs to the signal processingtechnical field, and also can be used for spectrum analysis of other signals. Very high harmonic wave detection accuracy can be obtained by the method; the instantaneity can be doubled compared with three to five signal periods of a quasi-synchronizing method; and the time of two signal periods are only needed, and the fundamental wave frequency also can be accurately measured.

A mixing apparatus and related methods are provided. The mixing apparatus can filter out unwanted harmonic orders according to demands, to thereby increase circuit attribute performance. Regardless of the type of mixing circuit used for the mixing apparatus, the harmonic interfering phenomenon can be substantially improved.

This invention provides an infrared diffractive lens capable of focusing infrared rays within a wide range of wavelength band effectively. According to the present invention, there is provided an infrared diffractive lens including a concave-convex shape with predetermined depth defined based on a predetermined standard wavelength in a wavelength band of incident infrared rays, wherein: the incident infrared rays are within the wavelength band of 1.1-16 μm; a depth h of the concave-convex shape is defined by mλ / (n−1) with regard to a refractive index n of material of lens, the standard wavelength λ and a harmonic order m; and the harmonic order m is an integer between 2 and 10. Using the infrared diffractive lens with such a configuration makes it possible to focus infrared rays within a wide range of wavelength band effectively.

A method of monitoring health of a mechanical drive train is provided. The method includes obtaining voltage and current signals from at least one phase of an electrical machine coupled with the mechanical drive train. The method also includes representing the electrical machine having a non-sinusoidal flux distribution as a combination of a plurality of harmonic order sinusoidally distributed virtual electrical machines based on the obtained voltage and current signals. The method further includes determining a torque profile associated with one or more combinations of the sinusoidally distributed virtual electrical machines. Finally, the method includes detecting the presence of an anomaly in the mechanical drive train based on the torque profile or spectrum.

The invention discloses an arc-suppression method of a ground fault in a neutral non-grounding system and an apparatus thereof. A power supply apparatus is connected to a neutral line in the neutral non-grounding system. Through the power supply apparatus, a compensation voltage is output so as to compensate a fault current of the system so that an arc-suppression purpose is reached. An output voltage of the power supply apparatus is defined in the description, wherein omega is a fundamental wave angular frequency; ic, iR and ih are capacitive, resistive and harmonic wave currents respectively; n is a harmonic order; a zero sequence voltage on a neutral point is defined in the description and L is an equivalent inductance of a power supply system. The arc-suppression method of the ground fault in the neutral non-grounding system and the apparatus are easy to carry out and arc suppression can be effectively enforced aiming at a single-phase ground fault.

A centrifugal pendulum device with a variable rotating radius is carried in an automobile damper. The centrifugal pendulum device with the variable rotating radius comprises a driving plate, slip sheets, reset springs, rivets, centrifugal pendulums and limiting rivets, wherein the slip sheets, the reset springs, the rivets, the centrifugal pendulums and the limiting rivets are symmetrically arranged on the driving plate. The slip sheets are arranged on the driving plate in a radial sliding mode through the limiting rivets, and meanwhile, the slip sheets and the driving plate are connected through the reset springs. The centrifugal pendulums are arranged on the slip sheets in a swinging mode through the rivets. Driving plate rivet work holes are formed in the driving plate. Centrifugal pendulum arc grooves are formed in the centrifugal pendulums. Slip sheet arc grooves are formed in the slip sheets. The rivets are connected with the centrifugal pendulum arc grooves, the slip sheet arc grooves and the driving plate rivet work holes. According to the centrifugal pendulum device with the variable rotating radius, when the work rotating speed of the centrifugal pendulums is changed, the work radius of the centrifugal pendulums is changed, then engine vibration harmonic order eliminated by the centrifugal pendulums is changed, and each order of main harmonic order vibration of an automobile power drive system can be eliminated; and by being combined with the work rotating speed corresponding to vibrating of each harmonic order when an engine works, vibration in a plurality of harmonic orders is eliminated by means of suitable centrifugal pendulum design parameters

The invention relates to a low-rotation-noise cooling fan for an automobile engine. The cooling fan comprises a fan body and a protection ring, the fan body comprises a plurality of fan blades in non-uniform distribution, and the protection ring connected with the fan body is provided with a plurality of guide blades in non-uniform distribution. Due to non-uniform distribution of the fan blades of the cooling fan, superposition of rotation noise of the fan at a harmonic order is avoided, the rotation noise and harmonic components thereof are urged to move to a non-critical order to realize reasonable distribution at each order of rotation frequency of the fan, and consequently the rotation noise can be weakened. Due to non-uniform distribution of the guide blades, time sequence uniformity in striking of the guide blades struck by trailing edge airflow of the fan blades is avoided, concentration of pressure fluctuation frequency and harmonic components at a certain specific order is avoided as well, and consequently the rotation noise of the fan is further reduced. By the guide blades for rectification of flow passing through a space behind the fan blades, rotation noise at partial orders can be reduced.

The invention discloses a multi-target selected harmonics suppression pulse width modulation method of a modular multilevel converter. The method includes: determining a target harmonics order and an upper suppression limit value of selected harmonics suppression of the modular multilevel converter according to actual engineering application requirements, establishing a multi-target optimization function and constraint conditions of selected harmonics suppression of the modular multilevel converter based on 1 / 4 cyclic symmetry through a Fourier transform algorithm, designing a multi-target adaptive extremal optimization solver to acquire a group of non-dominated switch angles, transmitting the switch angles to a pulse width modulation module of the modular multilevel converter, and detecting output voltage waves and corresponding total harmonic distortion of the modular multilevel converter through an oscilloscope. Multi-target selected harmonics suppression pulse width modulation effect of the modular multilevel converter meeting multi-performance index compromise optimization can be realized, the output voltage waves of the modular multilevel converter have more superior harmonic characteristics, corresponding total harmonic distortion is lower, and switching loss is lower.

The invention discloses a field programmable gate array (FPGA)-driving-generation-based cascaded multilevel converter, which comprises a frequency conversion controller and an FPGA connected with the frequency conversion controller. The FPGA comprises a bus interface module, a frequency division module, a sinusoidal wave generation module, a carrier generation module and a driving signal generation module. A phase shift carrier sinusoidal pulse width modulation (SPWM) technology is adopted, and N carriers are compared with a three-phase modulated wave respectively, so that N bi-level three-phase SPWM signals are obtained. The characteristics of the FPGA are fully utilized, and a data storage circuit, an address generation circuit, a control circuit and the like which are required by the generation of the SPWM signals are all integrated into a chip, so that a frequency conversion system has a high integration level, low cost and high reliability, and comprises a few parts; and a device resource utilization rate is high, switching frequency is reduced, a sideband harmonic order is increased, and the frequency conversion system is low in switching loss and low in harmonic content.

The invention discloses a method for extracting harmonic components in a dynamic sinusoidal distortion signal. The method comprises: determining a data length N and a sampling frequency for performingFourier transform; constructing a second-order cosine combining window to obtain a novel second-order cosine combined self-convolution window; acquiring a weighted sinusoidal distortion signal; carrying out discrete Fourier transform with the data length of N on the weighted sinusoidal distortion signal to obtain a spectral function; searching for the spectral function, searching peak spectral lines in the frequency range, marking the peak spectral lines; according to the harmonic order, calculating additional spectral lines numbers required by correcting all peak spectral lines; according tothe additional spectral line of the m-th harmonic, correcting the peak spectral lines and calculating a corrected accurate frequency; and on the basis of the calculated m-th harmonic frequency, calculating a correction amount of the harmonic spectral line and acquiring the amplitude of the m-th harmonic component in the sinusoidal distortion signal. Therefore, the accuracy of the harmonic component extraction in the dynamic sinusoidal distortion signal is improved.

The invention relates to a method for diagnosing deterioration by comparing indicated values. An indicated value is obtained by the relative harmonic component of each order current harmonic flowing into a motor and a converter dividing the total harmonic distortion of a preset order of the current harmonic, a standard value is obtained by a calculated value multiplied by a harmonic function of each formation order of the indicated value, to be used to diagnose each order found by calculation from the relative harmonic component of each order. In the method, the deterioration degrees of the motor and the converter are distinguished through a weighted standard value, and deterioration parts are determined through the concrete harmonic order of the current harmonic.

The invention discloses an integer slot distribution winding virtual pole spoke type permanent magnet synchronous motor and a low pulsation design method thereof. A virtual pole structure is additionally arranged on the outer edge of the spoke type permanent magnet synchronous motor, and a low-pulse virtual pole spoke type permanent magnet synchronous motor can be obtained through asymmetric and offset pole design of the virtual pole. The method for restraining torque pulsation can be divided into the following steps of firstly, starting from a principle of torque pulsation generation, determining the rotor magnetomotive force harmonic order affecting torque pulsation; secondly, according to the relation that the rotor air gap flux density is in direct proportion to the rotor magnetomotiveforce, determining the harmonic order of the rotor air gap flux density influencing the torque pulsation; and then carrying out derivation of a fourier expression of the rotor air gap flux density inunequal virtual magnetic pole arc coefficients, and then obtaining a formula between an unequal-pole arc coefficient angle difference value and a specific torque pulsation main harmonic order; and finally, eliminating the secondary torque pulsation through the unequal-pole arc coefficients, wherein the magnetic pole offset is used for eliminating primary torque pulsation.

The invention relates to a method for assessing occurrence of commutation failure based on the harmonic comprehensive commutation coefficient. The corresponding AC bus voltage of a certain extinctionangle drop moment of operation to the inverter station converter valve is acquired, and the phase offset of the voltage amplitude of each harmonic and the fundamental phase relative to the normal commutation situation and the corresponding leading trigger angle and the extinction angle of the moment under normal operation of the system are obtained after Fourier transform of the AC bus voltage ofthe moment; the harmonic voltage comprehensive influence factor and the harmonic phase comprehensive influence factor are calculated, the two factors are added to obtain the harmonic comprehensive commutation coefficient, and the DC system commutation failure is judged according to the situation of whether the harmonic comprehensive commutation coefficient is greater than the maximum commutation area margin. The calculation method is low in calculation dimension and fast in speed; the method comprehensively considers the harmonic order, the harmonic voltage amplitude and the fundamental offsetcaused by the harmonic waves so that the calculation and judgment result is enabled to be more accurate; and the method is suitable for evaluation of continuous commutation failure.

The invention discloses a parallel control method employing selective harmonic elimination pulse width modulation (SHEPWM) for multiple T-type three-level inverters. The parallel control method comprises the following steps of determining the quantity of switching angles of each period according to the quantity of harmonic orders needed to be eliminated; figuring out a switching angle of SHEPWM based on a multi-object particle swarm optimization method, and generating a corresponding SHEPWM signal; acquiring a neutral-point voltage and a zero-sequence loop current of a T-type three-level inverter parallel system; setting a time sequence, carrying out small vector control on the SHEPWM signal according to the neutral-point voltage or the zero-sequence loop current and the time sequence, and rewriting the SHEPWM signal. The neutral-point voltage or the zero-sequence loop current is controlled according to the set time sequence. Since the neutral points of the multiple inverters are connected, the neutral-point voltage of the system is balanced only by controlling the neutral-point voltage of an arbitrary inverter at a certain moment.

The invention discloses a device and method for protection of electric reactors in series connection. The method is realized based on a protection device, the reactors in series connection and the capacity ratio of capacitors are determined according to harmonic order which is required to be inhibited; normal impedance ratio and impedance ratio error are further obtained; actual impedance ratio is calculated through collecting busbar voltage value, shunt capacitance voltage value, and loop current value; whether the actual impedance ratio exceeds the set impedance ratio error or not is determined; if the absolute value of the difference between the actual impedance ratio and the normal impedance ratio exceeds the set impedance ratio error, an alarm is sent, and the reactors in series connection is drawn back from the system. The device and the method overcome the problem of safety in operation of reactors in series connection in a conventional shunt capacitance compensation device, solve the short circuit problem of a winding wire compartment in the reactors in series connection, and solve the problems of turn-to-turn short circuit and layer short circuit of the reactors in series connection, so as to guarantee the safety in operation of the reactors in series connection.

The invention discloses a low-resistance and high-pass filter. The low-resistance and high-pass filter is composed of a first capacitor (C1), an electric reactor (L), a second capacitor (C2), a resistor (R), a first switch (K1) and a second switch (K2); the first capacitor (C1) and the electric reactor (L) form a first parallel connection body (P1), the second capacitor (C2) and the second switch (K2) are connected in series and then are connected with the resistor (R) to form a second parallel connection body (P2), and the first parallel connection body (P1) and the second parallel connection body (P2) are connected in series. The filter can generate impedance lower than a resistance value of an existing high-pass filter along with increasing of harmonic orders (frequency), the filtering effect is better, and the capacity for restraining high-frequency resonance is higher.

The invention proposes a method for measuring harmonic interaction strength of an AC side of an inversion station of a multi-fed DC system. The method comprises the steps of 1) determining harmonic order k of a to-be-researched inversion station in the multi-fed DC system, and assuming total number of the to-be researched inversion station as n; 2) calculating k-order harmonic self-impedance Z<ii(k)> of a conversion bus i in a to-be-researched system, k-order harmonic mutual impedance Z<ij(k)> between the conversion bus i and a conversion bus j and equivalent harmonic impedance z<i(k)> and z<j(k) after Thevenin equivalent on an AC system connected with the conversion bus i and the conversion bus j, wherein I is equal to 1, 2 until n, and j is equal to 1, 2 until n; and 3) calculating a harmonic interaction effect factor HEIIF<ji(k)>, wherein the size of the HEIIF<ji(k)> and the interaction effect intensity of direct current i on direct current j are in positive proportion relation. TheHEIIF<ji(k)> is rapidly obtained by a harmonic impedance matrix, and reference is provided for estimating intensity of harmonic interaction effect of the AC side between inversion stations in the multi-fed DC system.

The invention relates to a passive power filter structure, which is composed of a power supply, a balance reactor, a capacitor, a reactor and a load. A filter branch of a specific harmonic order is formed by resonance analysis and calculation of the inductance value of a specific reactor and the capacitance value of a corresponding capacitor. The order of high harmonic can be checked out by harmonic detection. A variety of specific harmonic filter branches are connected in parallel to form a filter circuit group, which can filter multiple harmonics. The problem of multiple harmonics generatedby a nonlinear load is solved. The roles of the balance reactor are to reduce the difficulty of tuning and compensate for voltage drop. The structure has the characteristics of high safety, long service life and convenient operation. The balance reactor also plays a role in power compensation.

The invention discloses a control method of a duplex-winding high-power explosion-proof electric machine system based on IGCT five electrical levels. The control method of the duplex-winding high-power explosion-proof electric machine system based on the IGCT five electrical levels includes the steps: setting set values of a rotating speed and a flux linkage, computing set values of a d-axis and a q-axis under a synchronous rotating coordinate system through a PI adjuster of the rotating speed and the flux linkage, accordingly acquiring an amplitude value of a reference voltage vector, and then acquiring a rotary reference voltage vector through transformation of coordinates; acquiring six-phase voltage needed by a duplex-winding motor through a five-electrical-level space vector pulse width modulation algorithm according to a set rotary reference voltage vector; and acquiring needed information of voltages, currents and the rotating speeds through a voltage, current and rotating speed detecting module, and acquiring information of the flux linkage and rotating angles through flux linkage observing. According to the control method of the duplex-winding high-power explosion-proof electric machine system based on the IGCT five electrical levels, compared with an inverter with two electrical levels and three electrical levels, the inverter has the advantages that harmonic content of voltages and currents is greatly reduced and harmonic orders are increased, wherein the voltages and the currents are output by the inverter, and the phenomenon that imbalance of two set winding currents is caused by inconsistency of winding parameters is avoided.

The present invention relates to a method of diagnosing deterioration by comparing an index value which is obtained by dividing the relative harmonic content of each order of the current harmonics flowing into an electric motor and inverter by the total harmonic distortion of the current harmonics up to the predetermined order, with a criteria value which is obtained by multiplying a harmonic function of each order formed of the index value by a calculated value for diagnosis of each order found through calculation from the relative harmonic content of each order. In the method, the degrees of deterioration of the electric motor and inverter are distinguished from each other by weighting the criteria value, and the deteriorated part is determined by a specific harmonic order of the current harmonics.

The invention discloses an SHEPWM (selective harmonic elimination pulse width modulation) adopted T type three-level inverter neutral-point voltage balance control method. The number of switching angles in each period is determined according to the number of harmonic orders needing to be eliminated; a selective harmonic elimination pulse width modulation switching angle is solved based on a multi-objective particle swarm optimization method to generate a corresponding selective harmonic elimination pulse width modulation signal; the T type three-level inverter neutral-point voltage is collected; the signal is optimized; if the T type three-level inverter neutral-point voltage is within a threshold value range, the T type three-level inverter is not changed and the signal directly enters the three-level inverter; and or otherwise, the switching state is replaced by a corresponding low-vector signal to modify the selective harmonic elimination pulse width modulation signal. The control method provided by the invention has the same function of eliminating low-order harmonics as the conventional SHEPWM; and in addition, the control method can maintain the neutral-point voltage balance and can enable the T type three-level inverter to operate stably and efficiently.

The invention relates to a filtering cabinet, and in particular relates to a filtering device of an intermediate frequency smelting furnace. The filtering cabinet comprises a controller, a switching execution mechanism and a plurality of passive filtering branches of principal character harmonic order, wherein the controller comprises a current sampling unit, a real-time current sampling value storage unit, a switching current threshold storage unit, a comparator and a data processing unit; and the controller controls step-by-step switching-on or switching-off of each passive filtering branchin accordance with the comparison result of the comparator and also controls the switching execution mechanism to switch on the passive filtering branches from low order to high order and switch off on the passive filtering branches from high order to low order. A switching strategy of the controller is determined by a load current, so all designed harmonic passive filtering branches can be ensured to switch on in a full load state, and the filtering effects are preferable.

The invention provides a closed loop compensation method and system based on DFT rotation transformation, and a medium. The method comprises steps that selected harmonic frequency signal generating steps are as follows, a grid voltage is acquired, a sampling signal is obtained, the obtained sampling signal is inputted into a phase locked loop to generate a sinusoidal sin (kwft) signal and a cosinecos (kwft) signal of the selected harmonic frequency, k is the selected harmonic order, wf is the fundamental angle frequency, and t is the time; selected harmonic current acquisition steps are as follows, the grid current is acquired, through kth DFT transformation, kth synchronous rotation transformation, kth regulation and kth rotation inverse transformation, a real part of the transformationresult is extracted as the kth harmonic reference current and is taken as the selected harmonic current obtained. The method is advantaged in that combining advantages of DFT frequency domain transformation and synchronous rotation transformation, the response speed of a simple frequency domain transformation method is improved.

The invention discloses a permanent magnet synchronous motor back potential harmonic suppressing method. The method comprises the steps that a function containing a sine forms a salient pole; the salient pole forms the excircle of a motor rotor through a circumferential array, or the excircle of the motor rotor is composed of a line which cannot be described by a function; the back potential waveform of a motor is tested; the harmonic order and amplitude are decomposed through Fourier transform; the sinusoidal function subtracts a harmonic function to form a new salient pole; and the new salient pole finally forms the excircle of the motor rotor through the circumferential array. Motor air gaps made by the method are sinusoidally distributed. An excircle function subtracts the back potential harmonic function. The back potential harmonic result is suppressed. The method has the advantages of simple and effective principle, strong operability, low motor back potential harmonic content,small torque fluctuation and low vibration noise.

The invention relates to a method for constructing a harmonic wave impedance characteristic function. The method comprises the steps that voltages at a common coupling point of distributed grid-connection power generation systems and currents connected into the distributed grid-connection power generation systems are collected; the fundamental wave impedance amplitude |Z1| at the common coupling point of the distributed grid-connection power generation systems and the harmonic wave impedance amplitude |Zk| at the common coupling point of the distributed grid-connection power generation systems are calculated, wherein k is a natural number larger than 1 and represents a corresponding harmonic order; according to a function (please see the specific formula in the specification), the harmonic wave impedance characteristic quantity phi (k) at the common coupling point is obtained. The method for constructing the harmonic wave impedance characteristic function is capable of obtaining the characteristic quantity for reflecting island load characteristics and lowering island error judgment occurring when grid frequency or voltages change or the multiple grid-connection power generation systems operate in parallel, and is wide in application range.

The invention relates to a power system harmonic flow algorithm giving consideration to uncertainty and three-phase unbalance, and the algorithm comprises the steps: selecting a harmonic order h; calculating an h-th order harmonic current value of a harmonic source injection system connected with a nonlinear load node; building an h-th order harmonic model of system elements comprising all circuits and a transformer; initializing a harmonic voltage and phase angle of each node; setting the number of interaction times, and calculating the equivalent injection harmonic current value of each linear load node in each iteration process; solving the sum of the branch harmonic currents from a tail node, and obtaining the harmonic current value of each phase of each branch circuit; sequentially calculating the harmonic voltage values of the nodes from the head end of a feed line to the tail end of the feed line, wherein an iteration ending criterion is that the deviation of the harmonic voltage of each node at each phase relative to the value at the last iteration is less than an allowed value; and solving the distortion rate of the harmonic voltage of each node at each phase according to an obtained fundamental wave voltage value and the value of each harmonic voltage.