263 results about "Third harmonic" patented technology

The invention discloses an operation state fault monitoring method, system and device for a heavy-load overhead line, and relates to the technical field of electrical fault detection of the heavy-load overhead line. The method comprises the following steps: injecting a high-frequency test signal into a heavy-load overhead line to carry out predefined fault detection so as to obtain a total harmonic distortion rate; performing first harmonic optimization adjustment according to comparative analysis of the total harmonic distortion rate and a threshold value; performing harmonic second optimization adjustment according to the monitoring analysis result of the external load fluctuation of the heavy-load overhead line; and performing harmonic third optimization adjustment according to the monitoring analysis result of the external environment fluctuation of the heavy-load overhead line. According to the invention, through multi-stage distribution adjustment, the effect of improving the dynamic regulation and control accuracy of the high-frequency test signal injection fault monitoring method of the heavy-load overhead line in extreme weather is achieved; the problem of insufficient dynamic regulation and control accuracy of a high-frequency test signal injection fault monitoring method of a heavy-load overhead line in extreme weather exists.

The invention discloses a low-cost high reactive overload energy storage converter topology and a modulation strategy thereof, is used for improving the reactive overload capacity of an energy storage converter, and belongs to the technical field of alternating current-direct current converters. According to the invention, the auxiliary diode is additionally arranged on the traditional ANPC bridge arm, so that the reverse current of the IGBT module is shared during high-proportion reactive output of the converter, and the reactive overload capacity of the converter can be efficiently improved with low cost on the basis of fully utilizing the existing equipment. Besides, a reactive overload capacity enhancement modulation strategy based on third harmonic injection is provided for the topology, and third harmonics are injected into modulation waves, so that the utilization rate of an auxiliary diode is improved, and the output capacity of reactive current is further enhanced. According to the method, a 100kVA prototype is tested and verified in Simulink / Plecs, the device cost of the proposed topology is only increased by 5.45% on the basis of a traditional ANPC, the reactive overload capacity is increased by 22%, and the power grid voltage supporting capacity of the energy storage converter can be effectively enhanced.

The invention discloses an automatic control method and system for a bias point of a photoelectric modulator, and relates to the field of signal processing, and the method comprises the steps: generating a composite disturbance voltage signal through a digital signal processor; the bias electrode is injected into the photoelectric modulator and used for collecting the optical signal output by the photoelectric modulator and converting the optical signal into an electric signal; extracting a fundamental component amplitude and phase difference data of a second harmonic component, a third harmonic component and a fundamental wave; dynamic characteristic parameters are calculated through spectral analysis, and the mapping relation between the characteristic parameters and the offset of the offset points is established; outputting the offset direction and the offset level of the offset point through a deep learning model; a bias voltage compensation amount is generated through a fuzzy PID (Proportion Integration Differentiation) controller; and adjusting the bias electrode voltage, smoothing the filter, and eliminating high-frequency jitter. The method has the advantages that high-precision and stable bias point adjustment is realized through the composite disturbance signal, real-time spectrum analysis and deep learning optimization decision in combination with fuzzy PID control and a dynamic closed-loop mechanism, and the system performance and stability are remarkably improved.

The invention discloses an ultra-low phase noise harmonic wave type four-core voltage-controlled oscillator. The ultra-low phase noise harmonic wave type four-core voltage-controlled oscillator is composed of a transformer T1, a transformer T2, a transformer T3, a transformer T4, a head oscillator HR1, a head oscillator HR2, a head oscillator HR3, a head oscillator HR4, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a plurality of decoupling capacitors Cecap. According to the voltage-controlled oscillator, noise is prevented from being converted into phase noise by means of second and third harmonic impedance broadening, inductance loss reduction, reduction of the sensitive time of the resonant cavity to the noise and the like, the phase noise generated by the voltage-controlled oscillator can be effectively reduced, and excellent noise performance is obtained.

The invention discloses a method, a system, equipment and a medium based on a multi-composite ultrasonic penetration technology, and the method comprises the steps: generating high-frequency fundamental ultrasonic waves through a piezoelectric transducer array, and adjusting the frequency range to match the acoustic impedance characteristic of target soil; first, second and third harmonics are generated through the induction of a nonlinear medium in the fundamental wave propagation process, the phases of the harmonics are adjusted to realize coherent superposition, and the fundamental wave and the first, second and third harmonics are guided into a composite waveguide device for focusing and delay compensation to form a high-energy composite wave beam; a pulse interval is adjusted by adopting an intermittent emission strategy so as to inhibit energy attenuation in the soil; reflected wave spectrum components are monitored through an embedded acoustic sensor array, and driving parameters are dynamically adjusted; and residual ultrasonic energy is captured and fed back to a driving circuit to form a closed-loop energy utilization system. By integrating multi-order harmonic resonance and a dynamic frequency tuning technology, efficient transmission and deep penetration of ultrasonic energy in a complex medium are realized.

The invention discloses a fault diagnosis method and a fault diagnosis system for an electric valve actuating mechanism. The method comprises the following steps: synchronously acquiring signals through an anti-EMI (Electro-Magnetic Interference) multi-source sensor; adopting complex Morlet wavelet packet decomposition to extract a 1.2-2.4 kHz energy entropy minimum frequency band, and calculating a kurtosis index; separating the third harmonic of the current through variational mode decomposition, and calculating the total distortion rate of the third harmonic; a graph attention network with 12-dimensional features is constructed, and weighted fusion is carried out through a multi-head attention mechanism; the lightweight CNN outputs a fault type, and when the confidence coefficient is less than 0.9, a knowledge graph rule engine is triggered; and updating a threshold value based on a historical diagnosis clustering result, and aggregating edge model parameters by federal learning. The system comprises a wafer-level micro-strain sensing layer, an FPGA accelerated edge computing layer, a cloud platform supporting federated learning, and an AR maintenance guidance and block chain evidence storage module. The early fault detection rate is improved, the false alarm rate under strong EMI is reduced, and the average repair time is shortened.

The invention provides a switch cabinet contact temperature rise wireless sensing method and system based on surface acoustic wave resonance, and relates to the technical field of power system switch cabinet detection, and the method comprises the steps: calculating the real-time offset of a fundamental frequency and a third harmonic relative to a reference frequency, and obtaining the fundamental frequency offset and the third harmonic offset; in combination with the fundamental frequency offset and the equivalent acoustic impedance variable quantity of the oxide film, surface acoustic wave propagation path deformation caused by thermal expansion of the contact material is compensated by using a thermal-acoustic coupling partial differential equation, and the fundamental frequency net offset after temperature decoupling is obtained; sparse reconstruction is carried out on the temperature field of the contact area of the contact by adopting a compressed sensing algorithm, and three-dimensional temperature gradient distribution of the contact area of the contact is output; and inputting the three-dimensional temperature gradient distribution and historical time sequence data thereof into an intrinsic mode decomposition model for processing, and generating a dynamic self-adaptive early warning threshold value. The system has the advantages that passive, wireless, high-precision and full-space temperature rise monitoring is achieved, and intelligent operation and maintenance decision making of the switch cabinet is directly driven.

The invention relates to the technical field of radio frequency integrated circuits, in particular to a harmonic suppression power amplifier combining a matching network and a feed network, which comprises a transistor, an input matching module, an output matching module, a stabilizing module and a bias module, the input matching module comprises a first parallel resonance unit, the first parallel resonance unit is used for second harmonic suppression, the output matching module comprises a series resonance unit and a second parallel resonance unit, the series resonance unit is used for resonating at a second harmonic frequency and performing low-impedance grounding on the second harmonic, and the second parallel resonance unit is used for resonating at a second harmonic frequency and performing low-impedance grounding on the second harmonic. The second parallel resonance unit is used for resonating at a third harmonic frequency and forms a high-impedance open circuit for the third harmonic, the output matching module is coupled to a drain electrode of the transistor, and the bias module comprises a grid bias sub-module and a drain bias sub-module. The grid bias sub-module is coupled to a connection node of the input matching module and the grid of the transistor, the drain bias sub-module is coupled to the output matching module, and the bias voltage of the transistor is jointly determined by the grid bias sub-module and the drain bias sub-module. The power amplifier has the effect of improving the efficiency level of the power amplifier while realizing harmonic suppression optimization.

The invention discloses a multi-branch hydro-generator stator grounding fault active arc extinction method, which comprises the following steps: S1, constructing an analytic function of a double-frequency fault potential by using a neutral point and a generator end voltage after a generator fault and combining a winding connection sequence; s2, deriving a linear constraint relation between a third harmonic fault potential real part and an imaginary part; s3, according to the linear constraint relation, in combination with the potential expression of each branch winding of the third harmonic, constructing a target function for fault solution, and solving a solution set based on the third harmonic characteristic quantity; s4, according to the fundamental wave fault characteristic equation, constructing a fundamental wave difference coefficient multi-solution screening criterion, and obtaining a unique solution of the double-frequency fault potential; s5, aiming at the multi-branch hydro-generator, constructing a neutral point dual-frequency power supply injection amount calculation formula; and correctly adjusting the injection amount of the neutral point double-frequency controllable power supply by using the screened double-frequency fault potential unique solution, and suppressing the voltage of the fault point to be 0 to realize arc extinction. According to the invention, reliable arc extinction of the multi-branch hydraulic generator can be realized.

The invention discloses a full-power variable-speed pumped storage unit stator winding insulation state online monitoring method, and provides a high-capacity generator unit stator winding insulation state online monitoring method which can be applied to a network side transformer neutral point ungrounded system. According to the method, an effective common-mode monitoring loop can be established, and monitoring is carried out by utilizing the third harmonic of the motor stator winding and is not interfered by the high-frequency switch harmonic of the frequency converter. In order to solve the problem that a full-power variable-speed pumped storage unit generally has large capacity and is not easy to realize online measurement, the invention provides a method for measuring on a neutral point outgoing line, which can realize online measurement of the insulation state of a stator winding when the load current is relatively large. The method is suitable for a full-power variable-speed pumped storage high-capacity unit, leakage current measurement can be carried out under the condition of large load current, and stator insulation information online monitoring is achieved.

Method for compensating angular errors in the determination of angular values ​​by an arrangement with a permanent magnet and at least two magnetic field sensors, with a distance formed between the permanent magnet and the magnetic field sensors, in which a sinusoidal signal and a cosine signal are generated in the magnetic field sensors, and from the two signals an evaluation signal corresponding to the angular values ​​is formed by means of an arctangent function, wherein arrangement errors and errors of a measuring and evaluation unit change the shape of the evaluation signal and lead to an angular deviation in the evaluation signal, and in order to minimize the angular deviation, values ​​for correcting the gain errors and / or values ​​for correcting the orthogonality errors are changed from the signals and values ​​for correcting the gain errors and / or values ​​for correcting the orthogonality errors are determined.in which a second harmonic is determined for the evaluation signal and / or a third harmonic is determined for the signals and / or density differences of measurement points of a Lissajous plot.

The invention discloses a neutral line breakage detection and positioning method and system based on third harmonic energy characteristics, and the method comprises the steps: firstly, extracting the current and voltage of a load, calculating the third harmonic component through Fourier decomposition, obtaining the third harmonic energy through calculation, sequentially calculating the third harmonic energy ratio of two adjacent regions, and calculating the third harmonic energy ratio of the two adjacent regions; and comparing the calculated third harmonic energy ratio of each position with a set threshold value, and judging whether a neutral line breaking fault occurs or not and judging a line breaking position according to a result. According to the method, the neutral line breakage fault can be correctly distinguished and positioned, and the neutral line breakage detection capability is effectively improved.

The invention discloses an Internet of Things flowmeter data compression sensing transmission optimization method and system, particularly relates to the field of low-power-consumption wireless communication networks, and is used for solving the problem of compressed sensing signal distortion caused by sampling time sequence misalignment in an LPWAN bandwidth limited environment. Constructing a local phase reference by extracting a pipeline vibration fundamental frequency component, and receiving a cloud synchronization reference timestamp alignment signal; fundamental frequency and third harmonic components are separated to calculate arrival time difference, and a phase-locked loop is triggered to dynamically adjust the phase of a sampling clock based on a pipeline material threshold value; after the stability of the zero crossing point time variance is verified, compressed sensing sampling is performed on the flow signal by adopting a phase synchronous clock, and an optimized compressed measurement value is generated and transmitted to the cloud through the LPWAN; through closed-loop cooperation of physical characteristics and a communication clock, complete capture of a signal sparse structure is guaranteed under a low-bandwidth condition, and cloud reconstruction precision is significantly improved.

The invention discloses a dual-channel wireless energy supply system and a communication-free power control method thereof, and relates to the technical field of wireless power transmission, the system comprises a primary side transmitting end and a secondary side receiving end, the primary side transmitting end and the secondary side receiving end jointly construct a fundamental wave main power channel CH1 and a third harmonic channel CH2, energy and signal coupling transmission is realized between the primary side transmitting end and the secondary side receiving end through a dual-channel magnetic coupling structure. According to the method, the phase of third harmonic current is adjusted through an active rectification circuit of a secondary side receiving end, the load state is transmitted to a primary side transmitting end in a phase deviation mode, and after the primary side transmitting end detects phase information, the duty ratio of a full-bridge inverter is adjusted through a closed loop, and self-adaptive control over the output power of the system is achieved. According to the invention, non-communication transmission of a load state is completed by using a harmonic channel, closed-loop adjustment is carried out and the power range of the ZVS is expanded in combination with phase information, and stable and efficient wireless power transmission control is realized.

The invention provides a power distribution network fault detection method and system based on distortion center point recognition, and the method comprises the steps: building a nonlinear fault waveform simplified mathematical model through a piecewise function, carrying out the fitting of a nonlinear fault waveform of a power distribution network based on the model, and obtaining a fitted nonlinear fault waveform curve function; solving the fitted non-linear fault waveform curve function through Fourier transform to obtain a characteristic interval in which the phase difference between the fundamental wave and the third harmonic of the non-linear fault waveform at the distortion center point has regular distribution; processing an input fault signal to be recognized based on a similarity principle, and recognizing a nonlinear fault waveform distortion center point; processing a nonlinear fault waveform distortion center point to obtain a fundamental wave and third harmonic phase difference; designing a fault detection criterion based on the fundamental wave and third harmonic phase difference; and when the continuous set times in the set duration meet the fault detection criterion, determining that the distribution network fault with the nonlinear waveform characteristic occurs.

The invention discloses a broadband power amplifier with an output reconfigurable network, and relates to the technical field of microelectronics, the broadband power amplifier with the output reconfigurable network adopts a three-stage amplification circuit with a gate width ratio of 1: 2: 8, and signal pre-amplification and gain improvement are realized through the first two stages of amplifiers; the last-stage eight-tracheid parallel structure outputs saturated power under high-voltage power supply and realizes power additional efficiency; the output reconfigurable network is controlled by a first switch and a second switch, the first switch is turned off and the second switch is turned on in a high-power mode, so that a compensation microstrip line is grounded to form a fundamental wave matching branch knot, the loss of a harmonic suppression network is avoided, and high-efficiency output is guaranteed; in a low-power mode, the first switch is switched on, the second switch is switched off, the first LC resonance unit and the second LC resonance unit jointly form a band-stop filtering network, secondary and third harmonic impedance is adjusted to be in a near-short-circuit state, so that generation of higher harmonics is restrained, phase distortion is offset through the compensation microstrip line, and the integrity of fundamental wave signals is maintained.

The invention relates to the technical field of sensing detection, and discloses a quartz crystal microbalance based on a triple overtone resonance mode and a sensibilization method thereof, the sensibilization method comprises the following steps: using a triple harmonic drive circuit to drive a quartz crystal resonator sensing unit, enabling the quartz crystal resonator sensing unit to generate bridge oscillation in the triple overtone resonance mode, outputting a first electric signal containing a third harmonic frequency sweeping signal; detecting the third harmonic frequency sweep signal to obtain third resonance information, and performing inversion based on the change of the third resonance information to obtain to-be-detected micro-mass change information; wherein the tertiary resonance information comprises tertiary resonance frequency and tertiary resonance bandwidth. By adopting the third harmonic drive circuit, the quartz crystal microbalance works in a third overtone resonant mode, the third overtone resonant frequency of the quartz crystal microbalance is obviously higher than the fundamental frequency resonant frequency, and the sensitivity of the quartz crystal microbalance in the third overtone resonant mode is obviously improved as the sensitivity is in direct proportion to the resonant frequency.

The invention discloses a zinc oxide arrester aging fault monitoring method and system based on fifth harmonics, and belongs to the technical field of high-voltage electrical equipment protection. The method comprises the following steps: acquiring the total leakage current of the zinc oxide arrester under different applied voltages; the different applied voltages comprise pure sine wave voltages and voltages with harmonic components; according to the total leakage current, obtaining leakage resistance current and third harmonic and fifth harmonic thereof; comparing the total leakage current, the leakage resistance current, the third harmonic and the fifth harmonic to obtain a monitoring index of the aging fault of the zinc oxide arrester; and obtaining a monitoring result of the aging fault of the zinc oxide arrester according to the monitoring index of the aging fault of the zinc oxide arrester and the applied voltage. According to the invention, the harmonic component is added into the applied voltage to simulate the harmonic interference of the power grid voltage, and the leakage current of the lightning arrester is analyzed to monitor whether the aging fault of the zinc oxide lightning arrester occurs.

For example, a transmitter, e.g., for a wireless communication device, may be configured to transmit a wideband Radio Frequency (RF) Transmit (Tx) signal having a wide bandwidth of at least 80 Megahertz (MHz). For example, the transmitter may be configured to generate the wideband RF Tx signal having the wide bandwidth based on a baseband signal. The transmitter may be configured to generate the wideband RF Tx signal including a suppressed third harmonic and a suppressed fifth harmonic.

The invention discloses a balanced frequency tripling structure and terahertz equipment, which are applied to the technical field of terahertz, and comprise an odd-mode excitation structure connected with an input waveguide, a waveguide mode excitation structure connected with an output waveguide, and two coupling lines connected with the odd-mode excitation structure and the waveguide mode excitation structure, the two coupling lines are arranged in parallel to transmit differential signals; one coupling line is connected with a frequency doubling diode, the other coupling line is connected with another frequency doubling diode, and the two frequency doubling diodes form a balanced frequency doubling diode pair. Through the odd-mode excitation structure, electromagnetic waves can be converted into coupling line odd-mode work, so that radio frequency reverse excitation is carried out on the two frequency doubling diodes, and basic conditions for realizing idle harmonic suppression are constructed. And meanwhile, the odd mode excitation structure and the waveguide mode excitation structure can lock even harmonics generated by the frequency doubling diode in a nonlinear manner in the coupling line to form a high-integration-level idle harmonic loop, so that high efficiency of third harmonics can be ensured.

The invention discloses a three-phase alternating-current motor low-harmonic winding design method, which comprises the following steps of: determining the equivalent slot number qe of each pole and each phase of a three-phase low-harmonic winding according to basic parameters of a motor, dividing an area in an iron core slot of the motor into an upper layer, a middle layer and a lower layer, placing a phase coil of the three-phase winding in a single layer, and determining a phase belt distribution table and a winding connection diagram of the winding; according to the principle that slot current is distributed along the surface of an iron core in a sine mode, the numerical relation of the number of turns of all coils in a phase belt is determined, the turn ratio of all the coils is n1: n2: n3... nqe, the symmetry axis of slot electromotive force in the phase belt is determined, the electrical angles of slot electromotive force phasors relative to the symmetry line are respectively alpha1, alpha2, alpha3... alphaqe, and the range of the number of effective series turns of each phase meeting the motor performance is determined; in consideration of the design principle of the minimum harmonic magnetic potential and the limited slot filling rate, the actual number of turns of the coil in the phase belt is N1, N2, N3... Nqe. According to the invention, the third harmonic electromotive force amplitude of each phase of the motor is reduced, and the motor efficiency is improved.

The invention provides an axial skewed pole motor eccentricity detection method based on asymmetric layered Hall, and the method comprises the following steps: respectively installing a first group of linear Hall sensors and a second group of linear Hall sensors on a first axial layer and a second axial layer of a stator notch of an axial skewed pole motor in an asymmetric manner; after analog-to-digital conversion is carried out on the voltage signals detected by the linear Hall sensor, a pair of orthogonal third harmonic sinusoidal signals is obtained through grouping signal superposition, and the eccentric direction is determined; and based on a complex factor filter and a synchronous reference system phase-locked loop, extracting amplitudes of a positive sequence signal, a negative sequence signal and a sideband signal from the third harmonic sinusoidal signal, and further calculating a static eccentricity rate and a dynamic eccentricity rate. According to the axial skewed pole motor eccentricity detection method, two groups of linear Hall sensors are mounted in a layered and asymmetric manner, so that the eccentricity detection sensitivity and precision are effectively improved, the eccentricity state change in the motor operation process can be quickly responded, and the dynamic and static eccentricity rates and the eccentricity direction are output.

The invention relates to the technical field of power systems, and discloses a null line disconnection detection method and device, and the method comprises the steps: calculating a three-phase voltage unbalance degree according to a negative sequence voltage and a zero sequence voltage; judging whether the three-phase voltage unbalance degree exceeds a first preset threshold value or not; if the three-phase voltage unbalance degree exceeds the first preset threshold value, whether the difference value between the third harmonic content and the second harmonic content in the three-phase voltage exceeds a second preset threshold value or not continues to be judged; and if the difference value between the third harmonic content and the second harmonic content exceeds a second preset threshold value, determining that the zero line is disconnected. As the null line is disconnected, the third harmonic is obviously increased, and the second harmonic is slightly changed, the neutral line fault and other disturbances can be effectively distinguished through the difference between the third harmonic and the second harmonic. The zero-sequence component and the negative-sequence component are coupled, the three-phase voltage unbalance degree is calculated, the unbalance state of a three-phase system is represented more comprehensively and accurately, and the harmonic characteristic difference of each split-phase voltage is combined and can be effectively applied to neutral line fault detection.

The invention provides an alternating-current side third harmonic weakening modulation method of a railway power regulator under the condition that direct-current bus voltage contains frequency doubling ripples. The method comprises the following steps: constructing a bus voltage state space model of the railway power regulator, and designing a non-delay adaptive state observer to extract direct current component information of bus voltage; separating information of a direct current component and a double frequency ripple component of the bus voltage through a self-adaptive state observer; introducing the direct-current component information into voltage and current double-closed-loop control; designing a secondary pulse modulation ratio opposite to a ripple voltage phase through the extracted ripple pulse parameters; the third harmonic on the alternating current side of the RPC is weakened by injecting an opposite pulsation modulation ratio into a modulation coefficient; according to the method, under the condition that circuit topology and control strategy complexity are not increased, output voltage third harmonics are effectively weakened, direct current side voltage double frequency fluctuation is reduced, meanwhile, power coupling between the alternating current side and the direct current side can be compensated, the requirement for the capacitance value of a bus capacitor is reduced, the total harmonic distortion rate is reduced, and the service life of the bus is prolonged. And long-term stable operation of the system is guaranteed.

The invention provides a power distribution network early fault section identification method and system based on multi-dimensional feature probability mapping, and belongs to the technical field of power system power distribution network fault detection. The method comprises the following steps: collecting zero-sequence voltage of a power distribution network bus and zero-sequence current signals of head ends of all feeder lines, and obtaining derivative signals of the zero-sequence voltage and the zero-sequence current signals; calculating the third harmonic energy of the zero-sequence current of each feeder line, and when the third harmonic energy exceeds a set threshold value, judging that the feeder line has an early fault; processing the zero-sequence current signal, and extracting an IMF1 component; calculating a correlation characteristic quantity and a dot product characteristic quantity for each section formed by the current difference values of the adjacent measuring devices based on the IMF1 component; and respectively carrying out standardized transformation on the correlation characteristic quantity and the dot product characteristic quantity, substituting the correlation characteristic quantity and the dot product characteristic quantity into a Laplacian cumulative distribution function, calculating a probability value of a fault in each section, and judging a fault section according to a set probability threshold value. The method can effectively and reliably identify the early fault section of the power distribution network.

The invention belongs to the technical field of power electronics, and particularly discloses a phase-locked loop based on multistage filtering and compensation and a control method. According to the invention, the method comprises the steps: firstly collecting the voltage when a power grid is unbalanced or abnormal, then obtaining the d-axis and q-axis components of a positive sequence, a negative sequence, a third harmonic and a fifth harmonic through the positive and negative sequence separation, then designing a high-pass filter to filter out the negative sequence, the third harmonic and the fifth harmonic, and finally carrying out the amplitude and phase compensation of the filtered d-axis and q-axis components. And the information is sent to a traditional phase-locked loop for phase locking control, so that more accurate power grid phase information can be quickly obtained. According to the invention, under the conditions of unbalanced power grid voltage, harmonic interference and phase and frequency abrupt change, interference signals of third and fifth harmonics can be filtered out only by designing a set of filtering and compensation parameters, the phase locking speed is not slowed down while the phase locking precision is improved, and in practical application, the application has a wide application prospect. The method has the advantages of high dynamic response speed, simple parameter design, high reliability and the like.

The invention discloses a fault detection method and system for a permanent magnet synchronous motor, and relates to the technical field of permanent magnet synchronous motor fault detection.The method comprises the steps that stator three-phase current during operation of the permanent magnet synchronous motor is collected in real time, and zero-sequence current is calculated; carrying out multi-band frequency spectrum analysis based on the zero sequence current, respectively detecting a third harmonic amplitude and a sixth harmonic amplitude by adopting a parallel dual-channel FFT (Fast Fourier Transform) processor, and calculating a harmonic amplitude ratio; correcting the third harmonic amplitude and the sixth harmonic amplitude through a preset compensation coefficient matrix, and recalculating the corrected harmonic amplitude ratio; and performing fault classification on the corrected harmonic amplitude ratio based on a preset threshold value in combination with a time accumulation counter, and outputting a final fault code after continuous three times of consistent detection, thereby completing fault detection of the permanent magnet synchronous motor. The fault type can be rapidly positioned, the fault diagnosis precision is improved, it is ensured that an alarm is given after real faults are accumulated to the confirmable level, and the diagnosis reliability and stability are improved.

According to the auxiliary inverter control method under the secondary pulsation condition, the actual voltage value of a direct current bus is detected, a feedforward coefficient is calculated and obtained, the feedforward coefficient is multiplied by the output modulation ratio under voltage and current double closed loops, the modulation ratio is corrected, and therefore the influence of the secondary pulsation of the voltage of the direct current bus on the modulation process of the auxiliary inverter is eliminated, and the control accuracy of the auxiliary inverter is improved. And the output voltage THD and the three-phase unbalance degree of the auxiliary inverter are ensured to meet the requirements. After a passive LC resonant filter is cancelled, through voltage and current double-closed-loop control with direct-current bus voltage feedforward, the third harmonic component and the three-phase unbalance degree of output voltage of the auxiliary inverter under the rated load condition are reduced, stable operation of the auxiliary inverter under the secondary pulse condition is ensured, improvement is conducted through a software algorithm, and the stability of the auxiliary inverter is improved. The power density of the whole vehicle is improved, and equipment cost is reduced.

The invention discloses a space decoupling TBM cutterhead multi-phase motor sensorless field weakening control method, which comprises the following steps of: converting five-phase current of a TBM cutterhead FP-FIPM motor into alpha-beta axis and dq axis fundamental wave current and third harmonic current, calculating an estimated electrical angle and an estimated rotating speed by adopting a sensorless space decoupling strategy for estimating a rotor position, and calculating the position of the TBM cutterhead FP-FIPM according to the estimated electrical angle and the estimated rotating speed. Weak magnetic control is distributed to a fundamental wave space, sensorless control is distributed to a third harmonic space, a self-adaptive third harmonic current injection weak magnetic control method is adopted, and the torque output capacity of a weak magnetic area is improved through the weak magnetic control of the fundamental wave space and third harmonic current with a controllable injection ratio. The problem of space coupling brought by existing position-sensorless flux-weakening control in the fundamental wave space implementation process is solved, the estimation precision of position-sensorless control under flux-weakening operation is effectively improved, and the motor keeps low coupling, high precision, high robustness and high reliability in a complex multi-disturbance environment. And long-term stable high-efficiency operation of the TBM cutterhead driving system is ensured.

The invention discloses a grid-connected inverter and a control method thereof, and belongs to the technical field of power electronics and new energy grid-connected control, and the method comprises the steps: obtaining voltage and current signals of the grid-connected inverter and a grid-side three-phase voltage; performing coordinate transformation on the acquired voltage and current signals, and performing voltage and current double-closed-loop decoupling control to obtain a d-axis modulation signal and a q-axis modulation signal; generating a three-phase fundamental wave modulation signal according to the d-axis modulation signal and the q-axis modulation signal; calculating a fundamental wave modulation degree; calculating a zero-sequence current component of the grid-side three-phase current; taking the fundamental wave modulation degree and the zero-sequence current component as input quantities, and outputting a third harmonic injection proportionality coefficient through a fuzzy controller; generating a third harmonic injection amount according to the third harmonic injection proportionality coefficient; and subtracting the third harmonic injection amount from the three-phase fundamental wave modulation signal to generate a third harmonic injection type modulation signal. According to the invention, dynamic adjustment along with power grid disturbance, load change or modulation degree fluctuation can be realized.