171 results about "Third harmonic" patented technology

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 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 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.

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.

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 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 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.

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.

The application discloses a low-pulsation inverse-cosine plus third-harmonic auxiliary salient pole type radial permanent magnet motor and a method for optimizing air gap harmonics, and belongs to the technical field of motor manufacturing. A novel radial permanent magnet synchronous motor with inverse-cosine plus third-harmonic auxiliary salient poles is provided, and the method can suppress air gap flux density harmonics and reduce torque ripple and average torque loss. The specific process is as follows: the rotor air gap flux density is proportional to the rotor magnetomotive force, and the main air gap flux density harmonic order affecting the torque ripple is determined. The inverse-cosine plus third-harmonic method is used to modify the auxiliary salient poles, so as to reduce the air gap flux density harmonics, especially the 9th, 11th, 19th and 21st harmonics causing the first and second order torque ripples, thereby reducing the torque ripple; since the third harmonic is not the main air gap flux density harmonic causing the torque ripple, the injection of the third harmonic can reduce the average torque loss.

This invention discloses a reconfigurable injection-locked local oscillator system, comprising a voltage-controlled oscillator (VCO), an injection-locked frequency multiplier (ILL), and an injection-locked amplifier (ILA). The first output terminal of the VCO is connected to the first input terminal of the ILL, the second output terminal of the VCO is connected to the second input terminal of the ILL, the first output terminal of the ILL is connected to the first input terminal of the ILL, and the second output terminal of the ILL is connected to the second input terminal of the ILL. The VCO generates a low-frequency fundamental wave, the ILL multiplier performs frequency multiplication on the low-frequency fundamental wave to generate a second or third harmonic wave, and the ILL amplifies the power of the second or third harmonic wave, thereby improving the accuracy of the output millimeter-wave frequency.

The invention discloses a first and third harmonic shared cavity type impedance matching mechanism for a high-frequency buncher, which is characterized in that the first and third harmonic shared cavity type impedance matching mechanism is connected with a bunching electrode to jointly form the first and third harmonic shared buncher; the shared buncher is arranged between an external ion source of the cyclotron and the cyclotron; the cavity type impedance matching mechanism shared by the first harmonic and the third harmonic comprises a cavity type matching circuit shared by the first harmonic and the third harmonic and a coupler shared by the first harmonic and the third harmonic. According to the invention, the groove which is folded for multiple times is innovatively processed in the lower cavity of the cavity, so that the integrated structure of the lower cavity and the outer conductor is ingeniously realized, and the risk of folding cracking is fundamentally eliminated. Through the first harmonic and third harmonic shared cavity design, the function of originally needing two independent bunchers is integrated into one shared cavity, the system cost is effectively reduced, meanwhile, the occupied space is remarkably reduced, and the requirement of a compact accelerator is perfectly met.

The present invention discloses a detection method for an electrical automation power supply system, which relates to the field of power supply detection technology and solves the problem that it is not possible to accurately identify whether a corresponding line is affected by harmonics and synchronously suppress the harmonics based on the detected harmonics. The present invention is aimed at relevant lines affected by harmonics, and preferentially locks the third harmonic related to it based on the fundamental waveform associated in each phase circuit, and then selects the mean value related to it based on the amplitude of several third harmonics, so as to determine the corresponding waveform based on several groups of mean values, and then compares the determined waveform with the historical waveform, selects the closest regular waveform, and subsequently regenerates the suppression wave of such regular waveform, and performs harmonic suppression on the lines affected by harmonics, so as to achieve better power supply transmission effect and improve power supply safety.

The invention discloses an electrical automation power supply system detection method, relates to the technical field of power supply detection, and solves the problems that whether a corresponding line is influenced by harmonic waves cannot be accurately identified, and synchronous suppression is not synchronously performed based on the detected harmonic waves. For a related line with harmonic influence, third harmonics related to the fundamental waveform are locked preferentially on the basis of the related fundamental waveform in each phase of circuit, then mean values related to the third harmonics are selected on the basis of the amplitudes of a plurality of third harmonics, so that the corresponding waveform is determined on the basis of a plurality of groups of mean values, and the harmonic influence is eliminated. And checking the determined waveform with a historical waveform, selecting the closest regular waveform, subsequently generating a suppression wave of the regular waveform, and performing harmonic suppression on a line with harmonic influence, thereby achieving a better power supply transmission effect and improving the power supply safety.

This invention discloses a millimeter-wave broadband high harmonic suppression tripler, comprising an input matching network, a time-domain shaping tripler unit, and a differential common-source output stage. The proposed time-domain shaping tripler unit employs transistor pairs with different gate widths and bias voltages to superimpose two sets of voltage signals of different amplitudes in the time domain, thereby enhancing the inherent harmonic suppression of the tripler unit. Furthermore, by connecting a common-mode impedance control in series at the center tap of the primary inductor coil of the output transformer of the tripler unit, the output power of the third harmonic is further improved. The input matching network achieves single-ended to differential conversion, with its primary and secondary coil center taps grounded and open-circuited respectively in a counterintuitive manner, improving differential-mode balance and common-mode stability. Simultaneously, by using a series-coupled inductor, the quality factor of the transistor input impedance is reduced, improving the bandwidth performance of the tripler.

The application discloses a high-efficiency omnidirectional rectenna based on a class-F harmonic suppression structure and belongs to the rectenna field, comprising: a plurality of rectenna units which are arranged at equal intervals and rotate around the same center and are used for receiving radio frequency energy; the rectenna unit comprises a receiving antenna and a rectifier circuit; the receiving antenna comprises an antenna radiation structure, a metal floor and a feed microstrip line; a U-shaped groove is arranged on a region of the antenna radiation structure which is close to the metal floor, and a rectangular groove is arranged in the U-shaped groove; the U-shaped groove and the rectangular groove are used for suppressing the radiation of the second harmonic and the third harmonic; the rectifier circuit is arranged on the upper surface of a PCB and is used for rectifying the output signal of the antenna radiation structure by the microstrip line and electronic components; and the plurality of rectenna units are connected through a direct current synthesis network, so that the size of the rectenna can be reduced and the efficiency of the rectenna can be improved.

The invention discloses a power amplifier for improving amplitude phase distortion, relates to the technical field of power amplifiers, and solves the technical problems that the improvement of the amplitude phase distortion of the power amplifier is limited, the gain is greatly reduced, and the performance of the power amplifier is influenced in the prior art. The power amplifier comprises a first-stage input matching circuit, a first-stage driving amplifier circuit, a first-stage inter-stage matching circuit, a second-stage power amplifier circuit, a second-stage output matching circuit and a linearization structure, the second-stage power amplifier circuit adopts a fully differential structure to suppress the output of a common-mode signal, and performs power output based on an A-type working state of a CASCODE structure; the linearization structure introduces a third harmonic signal of the power amplifier into the alternating current ground through a capacitor, prevents fundamental waves from flowing in, and adjusts the opening degree through an MOS tube. The CASCODE structure is connected with a linear structure, amplitude phase distortion is improved, the linearity of the circuit is improved, and gain reduction is little.

An amplifier includes a signal input terminal for inputting an input signal; a voltage input terminal for inputting a power supply voltage; an amplification circuit for generating an amplified input signal based on the input signal, wherein the amplified input signal has a fundamental frequency, a first harmonic, and a second harmonic, wherein the first harmonic is the second harmonic of the fundamental frequency, and the second harmonic is the third harmonic of the fundamental frequency; a harmonic filter circuit coupled between the voltage input terminal and the amplification circuit for filtering the first harmonic and the second harmonic; and a signal output terminal coupled to the harmonic filter circuit for outputting an output signal based on the amplified input signal.

The present invention relates to the field of (digitally controlled) electric motors, (digital) control systems, (electric) motor-based systems, including those (digital) control systems, and methods relating thereto. The present invention addresses the complexity of dynamic switching between two or more different modulation algorithms, such as SVPWM (Space Vector Pulse Width Modulation), SPWM (Sinusoidal Pulse Width Modulation), THIPWM (Third Harmonic Pulse Width Modulation), DPWM (Discontinuous Pulse Width Modulation), OPP (Optimized Pulse Pattern).

The invention relates to the field of integrated circuits, and discloses a low-phase noise signal source circuit and radar equipment, and the low-phase noise signal source circuit comprises a four-core F23 type voltage-controlled oscillator which is used for generating a fundamental frequency, a second harmonic and a third harmonic; the harmonic self-mixer is connected with the quad-core F23 type voltage-controlled oscillator, and is used for mixing the fundamental frequency and the third harmonic into a quadruplicated frequency signal and outputting the quadruplicated frequency signal, and mixing the fundamental frequency and the fundamental frequency into a secondary frequency multiplication signal and outputting the secondary frequency multiplication signal; and the amplifier is connected with the harmonic self-mixer and is used for amplifying the quadruplicated frequency signal and outputting the amplified quadruplicated frequency signal. The signal source circuit can generate quadruplicated frequency signals.

The application discloses a kind of ultra-wideband high harmonic suppression power amplifier, including low-frequency power amplification branch, high-frequency power amplification branch, harmonic suppression matching network, the harmonic suppression matching network includes low-frequency harmonic suppression matching network, high-frequency harmonic suppression matching network and common output end;The low-frequency power amplification branch, high-frequency power amplification branch respectively to the frequency different low-frequency band signal, high-frequency band signal in work wideband is carried out power amplification, the low-frequency harmonic suppression matching network, high-frequency harmonic suppression matching network respectively to the impedance matching of fundamental wave in low-frequency band signal, high-frequency band signal after power amplification, while inhibiting second and third harmonic signals.The application solves the problem of low power efficiency and poor high-order harmonic suppression in the prior art.

A transmit / receive switch for magnetic resonance imaging (MRI) of a 1H atomic nucleus at 3T (tesla) and 7T magnetic field strengths includes a first and second dielectric substrate and a first and a second microstripline hybrid coupler formed on the first and second dielectric substrates respectively. A first port and a second port are connected to a first junction and a second junction respectively of the first microstripline hybrid coupler, a third port and a fourth port are connected to a third junction and a fourth junction of the second microstripline hybrid coupler respectively. Each port is connected by a matching network embodied by a microstripline wire to a pair of parallel resonant circuits. The transmit / receive switch is configured to operate at a fundamental frequency of about 127.8 MHz at 3T and at a third harmonic frequency of about 298 MHz at 7T.

The invention provides a third harmonic suppression film microstrip filter based on a mixed structure. Comprising a substrate, a pair of coplanar waveguide feeder lines used for being connected with an external circuit and playing a role in impedance matching, and a plurality of interdigital resonators used for generating passband characteristics of the filter, the hairpin resonator is used for generating a transmission zero point at the low end of the filter to improve low-end stop-band suppression, the 1 / 4 wavelength open-circuit lines are used for suppressing third harmonics of the filter, and the pair of coplanar waveguide feeder lines, the interdigital resonators, the hairpin resonator and the 1 / 4 wavelength open-circuit lines are all laid on the substrate. The plurality of interdigital resonators are located between the pair of coplanar waveguide feeders, the hairpin resonator is located between the plurality of interdigital resonators, the pair of coplanar waveguide feeders is connected with the interdigital resonators at two sides of the plurality of interdigital resonators, and the plurality of 1 / 4 wavelength open-circuit lines are connected with the pair of coplanar waveguide feeders in parallel.

The invention discloses a single-stage multi-port motor driver power distribution control method based on modulation wave splitting. The method comprises the following steps: firstly, obtaining a three-phase reference voltage of a single-stage multi-port motor driver under a natural coordinate system; under a virtual two-level framework, carrier pulse width modulation of third harmonic injection is used to generate a three-phase duty ratio; according to the first direct current source port reference power, a zero-sequence component is obtained through calculation; injecting the calculated zero-sequence component into a three-phase duty ratio of the motor, obtaining three-phase duty ratios of a first switch tube and a second switch tube under a virtual two-level frame based on modulation wave splitting, and obtaining three-phase duty ratios of the first switch tube and the second switch tube under an actual three-level frame through normalization; and finally, comparing the three-phase duty ratio of the motor under the actual three-level framework with a carrier wave to generate a driving signal to control each bridge arm switch tube.

The invention relates to the technical field of current converters, in particular to a method and system for adjusting the number of sub-modules in a modular multilevel current converter and electronic equipment. The method comprises the steps that target third harmonic zero-sequence voltage corresponding to each operation point in the operation range of the modular multilevel converter to be adjusted is determined, and the target third harmonic zero-sequence voltage is the third harmonic zero-sequence voltage enabling the bridge arm output voltage peak value of the modular multilevel converter to be adjusted to be minimum; under the condition that the modular multilevel converter to be adjusted is in a running state, determining a bridge arm voltage reference value of the modular multilevel converter to be adjusted under the current running point according to the target third harmonic zero sequence voltage corresponding to the current running point, and adjusting the number of sub-modules adopted in the modular multilevel converter to be adjusted according to the bridge arm voltage reference value. By adopting the scheme, the compactness and low cost of the modular multilevel converter can be realized.

The invention discloses a motor stator winding fault diagnosis method based on quadrature-axis current second harmonic components, belongs to the field of motors, and aims to solve the problems of low open-circuit fault diagnosis speed and low accuracy of a part of conductors of a five-phase permanent magnet synchronous motor. The method comprises the following steps: step 1, collecting a five-phase current signal of a motor, and separating quadrature-direct axis current of a fundamental wave space and quadrature-direct axis current of a third harmonic space through Clark transformation and Park transformation; step 2, Fourier decomposition is carried out on the quadrature-axis current of the fundamental wave space, a second harmonic component is extracted, and Fourier decomposition is carried out on the five-phase current to obtain a fundamental wave component; 3, calculating the change rate delta of a second harmonic component, and judging the number of fault strands according to a preset segmentation threshold value; and step 4, positioning a fault phase through the amplitude drop amplitude of the fundamental current amplitude of the five-phase current.