357 results about "Shaft voltage" patented technology

The invention relates to the technical field of servo control, in particular to a high-precision current closed-loop control system and method for a servo driver, and the method comprises the steps: collecting three-phase current, rotor position, winding temperature and bus voltage, and constructing a state data set; constructing a parameter identification model fusing physical prior and an attention mechanism, deducing inductance and flux linkage parameters influenced by temperature, saturation and cross coupling, and correcting a motor model in real time; the correction parameters are injected into an FOC decoupling and feedforward link, and a self-adaptive PI regulator is linked to set the gain of a current loop on line; calculating a d-q axis voltage command according to the update model to respectively control excitation and torque components; an extended state observer is introduced to estimate load abrupt change and parameter disturbance, feed-forward compensation is carried out, and three-phase PWM is generated through anti-Parker and SVPWM; and an inverter nonlinear compensation model of a dead zone and switch delay is constructed, PWM is pre-distorted and output to a power device, and robust and low-ripple current closed-loop control of the servo motor is realized.

The invention belongs to the technical field of industrial control, and particularly relates to a brushless direct current motor high-efficiency control method and system based on an FOC algorithm, and the method comprises the steps: superposing high-frequency sine disturbance in a voltage instruction, extracting a response component, achieving the online identification of the equivalent impedance of a motor, and dynamically solving and updating the estimated values of resistance and inductance; and correcting d-axis and q-axis voltage feed-forward items in real time by using the updated parameters, and correspondingly adjusting a current loop proportion and an integral gain. The method can adapt to the time-varying characteristics of motor parameters in an industrial field, so that the accuracy of feed-forward compensation and the stability of current loop bandwidth are effectively guaranteed, and the robustness and the control precision of a control system under complicated industrial working conditions such as variable temperature and variable load are remarkably improved; and the requirements of high-end industrial equipment on high performance and high reliability of the motor driving system are met.

A system for measuring generator shaft voltage and shaft current, which system relates to the technical field of power systems. The system comprises a mounting component (100), which is used for mounting grounding carbon brushes (200) on a rotating shaft of a generator at the end that is close to an exciter and at the end that is close to a steam turbine, wherein the grounding carbon brushes (200) include a first grounding carbon brush (201) and a second grounding carbon brush (202) which are located at the steam turbine end of the generator, and a third grounding carbon brush (203) at the exciter end thereof; and by means of monitoring shaft voltage and shaft current in real time, a processing module (303) calculates key parameters and performs real-time analysis and spectrum analysis. When a monitored value exceeds a threshold value, the system immediately issues an alarm, thereby effectively realizing the real-time determination of the operating state of a generator and fault early warning. Moreover, the system has the functions of storing and querying historical data, by means of which operators can evaluate the insulation performance of a generator shaft and predict potential problems, and thus prevent insulation accidents caused by an overly high shaft current, thereby prolonging the service life of devices, and ensuring the continuity and stability of a power production process.

The invention discloses a VSG transient stability control method based on PSS power angle compensation and integral reactive loop cooperation, and the method comprises the steps: constructing an improved rotor motion equation compensation mechanism based on a power system stabilizer, and based on the dynamic parameters of the voltages vabc and pcc at a PCC point and the currents iabc and pcc flowing into the PCC point which are collected in real time, carrying out the compensation of the current iabc and pcc at the PCC point under the condition that the working condition is that the voltage of a power grid drops greatly. The dynamic characteristic of active power is ensured; constructing a PSS parameter optimization method based on zero point position constraint; an integral link is embedded in the traditional voltage-reactive droop characteristic, integral reactive loop control is constructed, and steady-state voltage deviation is eliminated; the output compensation power angle delta and the output voltage amplitude E are cooperatively applied and converted into dq-axis voltage components Ed and Eq, the dq-axis voltage components Ed and Eq are sent to a voltage and current double closed loop, a driving signal is generated through SVPWM, and the stability of the system is enhanced.

The invention discloses a complex wave-based permanent magnet synchronous motor all-electrical parameter online identification method and device. The method comprises the following steps: analyzing the influence of a voltage error caused by dead zone time on parameter identification, and performing corresponding dead zone compensation; a bias complex wave with a certain amplitude and frequency is injected into the d-axis current, so that the d-axis current meets a parameter identification continuous excitation condition; constructing three groups of effective current slopes through four groups of different input data stored in the steady state of the motor, and identifying three groups of parameters of resistance, direct-axis inductance and quadrature-axis inductance by referring to a d-axis voltage equation and adopting a least square method with a forgetting factor; and finally, updating the identified three groups of parameters as known quantities in a q-axis voltage equation in real time, storing two groups of different input data to construct a group of effective current slopes, and identifying flux linkage parameters by adopting a least square method with a forgetting factor. According to the method, the under-rank problem of all-electrical parameter identification of the motor is solved, the identification precision is high, and the identification error of each parameter is about 3%.

The invention relates to an optimal power capturing method for a wave energy power generation device of a mixed-flow type air turbine, and belongs to the field of wave energy power generation. The optimal power capturing method comprises the steps that the change condition of the average output power of the turbine under different sea conditions along with the rotating speed is tested, and the maximum average output power point of the turbine under each sea condition is obtained; fitting the maximum average output power point under each sea condition to obtain a control law of the electromagnetic power of the motor; the quadrature-axis current reference value of the stator is made to be equal to zero, and the direct-axis current reference value of the stator is calculated; calculating a stator quadrature-direct axis current error term, and establishing a positive definite Lyapunov function; deriving the Lyapunov function, substituting the Lyapunov function into a stator quadrature-direct axis current state equation, and then performing transformation according to a first stability theorem to obtain a stator quadrature-direct axis voltage control law; and generating a corresponding SVPWM (Space Vector Pulse Width Modulation) switching signal according to a stator quadrature-axis voltage control law so as to control a motor-side converter and realize control on a turbine. The wave energy capturing efficiency can be improved.

The invention discloses a motor multi-parameter identification method based on sampling noise excitation and bias compensation, and the method comprises the steps: firstly obtaining the voltage and sampling current of a motor, and enabling the sampling current to comprise sampling noise; then constructing an information evaluation index, and adjusting a proportional parameter of a current controller to improve the identification information amount; then, shaft voltage feed-forward compensation is constructed to suppress electromagnetic torque pulsation; recursion is carried out by adopting a least square method based on the discrete linear parameterization model to obtain a parameter initial value and a covariance matrix; secondly, estimating offset-containing parameters on line, and calculating a sampling noise variance by using an estimated residual error; and finally, obtaining unbiased parameter estimation according to bias compensation iteration updating so as to output online estimation values of stator resistance, direct-axis inductance Ld, quadrature-axis inductance Lq and permanent magnet flux linkage.

The invention discloses a permanent magnet synchronous motor model prediction control method based on multi-target Pareto optimum, which comprises the following steps: measuring two-phase current, motor rotating speed and rotor position of a permanent magnet synchronous motor, converting the two-phase current into d-axis current and q-axis current according to the rotor position, and converting an alternative voltage vector of an inverter into d-axis voltage and q-axis voltage at the same time; inputting the d-axis current, the q-axis current, the d-axis voltage, the q-axis voltage and the rotating speed of the motor into a current prediction model of the permanent magnet synchronous motor, and predicting a future current state value; establishing a multi-target optimization model including torque ripple, current total harmonic distortion, switching frequency and power loss, calculating by using a multi-target particle swarm algorithm in combination with non-dominated sorting and congestion distance to obtain a Pareto optimal solution set, obtaining an optimal weight factor, and automatically adjusting target weights according to motor operation states under different operation conditions; and constructing a cost function based on the optimal weight factor, and selecting a voltage vector enabling the cost function to be minimum as optimal control output.

The invention discloses a method and a system for estimating direct-current bus current of an electric vehicle. The method comprises the following steps: acquiring a d-axis voltage instruction, a d-axis current, a q-axis voltage instruction and a q-axis current of a motor side; compensating the d-axis voltage instruction and the q-axis voltage instruction based on parameters including voltage delay time to obtain a compensated voltage value; calculating the electromagnetic power of the motor based on the compensated voltage and current; the loss power of hardware in the motor controller is obtained, and the direct current side power is calculated in combination with the electromagnetic power; and calculating a direct current bus current estimation value based on the direct current bus voltage and the direct current side power. According to the method, processing is carried out under the dq coordinate system, the operation requirement of the controller is reduced, the power calculation error is corrected through voltage compensation and system loss compensation, high-precision and low-cost direct current bus current estimation is achieved under the condition that an additional hardware sensor is not needed, and the control precision and reliability of an electric drive system are improved.

The invention discloses an SOP and feeder automation cooperative local fault self-healing method and system, relates to the field of distribution line fault self-healing, and can enable a section switch to lose voltage without opening when an interphase short circuit fault occurs in an SOP-containing distribution line, and firstly starts a fault current-limiting control measure to enable the fault to extinguish arc; secondly, a detection signal is injected in a fixed d-axis voltage mode, and permanent fault recognition is carried out; and finally, on the basis of a fault property identification result, constructing an SOP and feeder automation cooperative local fault self-healing scheme. The method can effectively discriminate the fault property and accelerate the power recovery speed, and facilitates the improvement of the power supply reliability of a power distribution system.

The invention discloses a rotor turn-to-turn short circuit diagnosis method based on an exciting current-shaft voltage harmonic nonlinear correlation coefficient. The method comprises the following steps: synchronously collecting parameters, and preprocessing the collected parameters through wavelet threshold denoising and temperature normalization; extracting harmonic analysis according to the shaft voltage harmonic characteristics; identifying magnetic saturation, temperature and load nonlinear factors and calculating corresponding coefficients; performing dynamic correction on the Pearson's correlation coefficient through the nonlinear correction coefficient, and combining with fuzzy logic weighting to obtain fuzzy logic weighting; defining a working condition feature vector, and constructing a working condition adaptive dynamic model comprising a linear regression basic model and an LSTM neural network; and calculating a dynamic threshold value based on the basic threshold value and the nonlinear factor, and judging the turn-to-turn short circuit trend of the rotor according to the comparison of the correlation coefficient and the dynamic threshold value and a prediction result. According to the invention, through combination of the nonlinear correction correlation coefficient and the LSTM neural network, dynamic compensation of nonlinear factors is realized, and the accuracy and reliability of rotor turn-to-turn short circuit fault diagnosis are improved.

A method is for adaptively controlling a charging module that converts three-phase AC input to DC output with improved power factor correction. The method includes performing Clarke and Park transforms on input three-phase AC voltages to obtain d-q axis components, measuring and transforming boost inductor currents to obtain current axis components, generating control values through current-loop and voltage-loop modules based on target and measured values, and synthesizing PWM signals to control switching operations. The method features adaptive phase angle computation using a proportional-integral controller that responds to load variations in real-time. The control system maintains high power factor under varying load conditions by continuously adjusting the phase reference based on the q-axis voltage error. This approach minimizes power losses, reduces harmonic distortion, and ensures stable operation across the full operating range of the charging module while maintaining unity power factor.

The application discloses a multi-port impedance optimization-based harmonic suppression method for a non-electrolytic capacitor permanent magnet synchronous motor driving system, and belongs to the technical field of motor control. The application is aimed at the problem that active damping control will cause the increase of machine-side harmonics when used for the network-side current harmonic suppression of a non-electrolytic capacitor motor system. The machine-side port impedance regulation voltage and the network-side port impedance regulation voltage are calculated. The entropy weight TOPSIS method is used to calculate the optimal angle of the machine-side and network-side port impedance regulation voltage, and the machine-side and network-side port impedance regulation voltage is synthesized into a cooperative voltage. The cooperative voltage is decomposed into a d-axis component and a q-axis component, and then is superimposed on the dq-axis voltage given value, so that the controlled dq-axis voltage given value is obtained. The regulated alpha-beta axis voltage given value is obtained through the inverse Park transformation link, and then the pulse control signal of the inverter is obtained through the SVPWM control, so that the machine-side and network-side harmonic suppression of the driving system is realized. The application is used for the cooperative suppression of machine-side and network-side harmonics.

The invention discloses a model-free predictive control method and system for a permanent magnet motor with an embedded generalized integral observer, and belongs to the field of permanent magnet motor control. A hyper-local model of the permanent magnet motor is constructed, disturbance variables of mechanical angular velocity and q-axis current are integrated to form lumped disturbance by introducing a new variable, and model reconstruction is performed to obtain a model-free predictive control model of the permanent magnet motor; observing disturbance of the reconstructed model through a third-order extended state observer embedded with a quasi-second-order generalized integrator to obtain a rotating speed prediction model; observing disturbance on the d-axis current model through an observer to obtain a d-axis current prediction model; based on the two prediction models, establishing a control rate equation of the d-axis voltage and the q-axis voltage; and based on the acquired system parameters, through a control rate equation, voltage of d and q axes is calculated to control motor driving. By integrating the disturbance of the rotating speed outer ring and the q-axis current ring into lumped disturbance, the design cost is reduced, and the dynamic response is improved. Through the TESO architecture embedded with the QGI, both dynamic disturbance rejection and periodic disturbance suppression are considered, and the stability of the system is guaranteed.

The invention discloses a whole vehicle electric drive resolver zero position identification and whole vehicle electric drive resolver zero position self-inspection method, and relates to the field of new energy electric drive control systems.The whole vehicle electric drive resolver zero position identification method comprises the steps that a direct-axis current instruction and a quadrature-axis current instruction are generated by receiving a torque instruction of a whole vehicle controller; sampling a motor phase current and performing coordinate transformation to obtain a feedback current; inputting the current instruction and the feedback current into a current regulator, and outputting direct-axis and quadrature-axis voltage components; injecting a high-frequency square-wave voltage signal into the direct-axis voltage component to generate a synthesized direct-axis voltage component, and performing PWM (Pulse-Width Modulation) to generate a driving signal; sampling the phase current again, extracting the high-frequency quadrature-axis response current, calculating the rotor position deviation, and inputting the rotor position deviation into the position observer to obtain the absolute position information of the rotor; wherein the PWM wave sending time sequence is aligned with the phase current sampling time sequence. According to the invention, the precision and efficiency of whole vehicle electric-drive rotary transformer zero position identification can be improved.

To provide a method for estimating an axis error between a d-q axis and a γ-δ axis in a synchronous motor.SOLUTION: In a control method for driving a synchronous motor by sensorless vector control, a magnetic axis of a permanent magnet of the synchronous motor is defined as a d-axis, a direction orthogonal to the d-axis is defined as a q-axis, a designated magnetic axis of the synchronous motor is defined as a γ-axis, and a direction orthogonal to the γ-axis is defined as a δ-axis, and when vγ iγ+vδ iδ=P / 2 ωR ΦM iδ+R (iδ^2+iγ^2) is established, it is estimated that the d-q axis and the γ-δ axis coincide with each other without an error, and when the above expression is not established, an amount of the error is estimated from a difference between the left side and the right side. vγ represents a γ-axis voltage [V], iγ represents a γ-axis current [A], vδ represents a δ-axis voltage [V], iδ represents a δ-axis current [A], P represents a motor pole number, R represents a motor one-phase resistance value [Ω], ωR represents a motor electrical angular speed [rad / s], and ΦM represents a magnet flux [wb].SELECTED DRAWING: Figure 2

The present disclosure relates to an electric motor assembly configured to mitigate electrically induced bearing damage (EIBD). More specifically, the electric motor assembly includes a chassis, a stator, a winding coil, a rotor, a shaft, conductors, a circuit, and insulators. The circuit can include one or more transformers capable of generating an injection voltage, which can mitigate shaft voltages that cause EIBD.

The application discloses a kind of static excitation generator shaft voltage component analysis method and device, the method is applied to generator, the method includes: measuring the shaft voltage component parameter of generator under different measurement state;Whether the shaft voltage component parameter reaches dangerous value is detected;If yes, then output classification alarm.The device includes rotor body, one end of the rotor body is steam end large shaft, the other end of the rotor body is excitation end large shaft, steam end carbon brush is connected on the steam end large shaft, excitation end carbon brush is connected on the excitation end large shaft, shaft voltage suppressor is connected on the excitation end carbon brush, the steam end carbon brush and the shaft voltage suppressor are electrically connected with relay.The application adopts the above method, with the advantages of high measurement accuracy, sensitive and effective, high degree of automation, guide repair.

The invention discloses a fault component compensation type low-voltage ride-through control method and system of a distributed power generation system and a storage medium, and the method comprises the steps: introducing a difference value between a d-axis voltage instantaneous component of a common coupling point and a system rated voltage into a quadrature-axis voltage compensation branch during the voltage drop period of a power grid, and obtaining a quadrature-axis voltage compensation amount through compensation coefficient calculation, the calculation result is added to the phase-locked loop control link, the q-axis voltage of the common coupling point tracked by the phase-locked loop is adjusted in real time, and the problem that the phase angle of the distributed power generation system is prone to loss stability during the transient state is effectively solved without any additional control information. And the low-voltage ride-through capability of the distributed power generation system under the extreme working condition is obviously enhanced.

The application discloses an online permanent magnet flux identification method of a permanent magnet synchronous motor considering cross coupling effect and belongs to the permanent magnet flux identification technology of the permanent magnet synchronous motor. The application aims at solving the problem that the existing permanent magnet synchronous motor flux identification method does not consider the cross coupling influence of the motor, thereby causing the error of the flux observation result to be large. The application comprises the following steps: under the online stable working condition of the motor, injecting a sinusoidal current signal into the dq axis of the motor to realize three-phase direct current signal injection; calculating the motor stator resistance; injecting two groups of direct current bias voltage into the d-axis of the motor through the current loop, establishing three motor voltage equations, and then obtaining two motor voltage difference equations which eliminate the flux terms; solving to obtain the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq ; establishing the dq-axis voltage equation considering the cross coupling, calculating the motor permanent magnet flux based on the motor stator resistance, the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq . The application is used for the online identification of the permanent magnet flux of the permanent magnet synchronous motor.

The invention discloses a quadratic programming-based permanent magnet synchronous motor model prediction field weakening control method and system. The method comprises the following steps of: giving a rotating speed reference value of a current motor, calculating a reference rotating speed of the motor, making a difference between the rotating speed reference value and the reference rotating speed, and obtaining a direct-axis current reference value according to a difference value relationship; according to the current value, the voltage value and the rotating speed value at the current moment, the current value and the rotating speed value at the next moment are calculated, and a current cross term is ignored in the calculation process; establishing a target function of a voltage instruction by combining the current value of the next moment, the rotating speed value of the next moment, the direct-axis current reference value and the rotating speed reference value; the objective function of the voltage instruction is converted into a quadratic optimization problem model with constraints, solving is carried out through a Karush-Kuhn-Tucker optimality condition, and an optimal voltage instruction is obtained; the optimal voltage instruction serves as reference quadrature-axis voltage and reference direct-axis voltage, and a duty ratio control signal used for controlling three-phase output is obtained through calculation; according to the invention, the dynamic response capability, the energy efficiency and the system stability of a weak magnetic region can be improved, and the urgent demand of a modern electric drive system for high-performance control is met.

A control system for an electric motor of an electrified vehicle includes an inverter of the electrified vehicle, the inverter comprising a set of switches and being configured to receive three pulse-width modulation (PWM) signals and to control the set of switches to generate an alternating current (AC) output voltage from a direct current (DC) link voltage provided by a battery system of the electrified vehicle, and a control system configured to determine a torque command for the electric motor, determine commanded d-axis and q-axis voltages based on the torque command, generate a trapezoidal wave modulating signal for carrier-based PWM based on the commanded d-axis and q-axis voltages, generate the three PWM signals by performing carrier-based PWM using the trapezoidal wave modulating signal, and control the electric motor using the AC output voltage generated by the inverter.

The application discloses a motor control method, a controller, a motor, a refrigerator, a medium and a program product. A direct-current bus voltage and a cross-axis current of a motor are acquired, and a direct-axis voltage and a cross-axis voltage are acquired. An initial direct-axis current is generated through field weakening control according to the direct-axis voltage, the cross-axis voltage and the direct-current bus voltage. A target frequency disturbance component caused by direct-current bus voltage fluctuation and a direct-current component used for field weakening control are separated from the initial direct-axis current. A phase of the target frequency disturbance component is calculated and optimized to obtain a target alternating current component, with minimization of a harmonic component of the target frequency in the cross-axis current as an optimization target. A direct-axis reference current is synthesized according to the target alternating current component and the direct-current component, and the motor is controlled according to the direct-axis reference current. In the working condition of the direct-current bus voltage fluctuation, energy backflow can be effectively inhibited, current harmonics can be reduced, torque pulsation can be reduced, and the running stability of the motor can be improved.

The present invention discloses a feedforward control method for enhancing system stability and filtering out high-order background harmonics of a power grid, comprising an LCL topology and a control loop, wherein a decoupling term and a capacitor current feedback active damping are connected in the control loop; the feedforward control method comprises the following steps: collecting a grid-connected current, a common coupling point voltage, and a capacitor current; obtaining a voltage phase angle of the common coupling point voltage through a phase-locked loop, and transforming the grid-connected current, the common coupling point voltage, and the capacitor current into dq axes through the voltage phase angle; indicating an angle difference between the dq axes of the system and the dq axes of the control loop; adopting a full feedforward strategy for the grid d-axis voltage feedforward and a full feedforward strategy for the grid q-axis voltage feedforward, deriving a duty cycle signal of the control system based on a transfer function of the d-axis and q-axis voltage feedforwards, and further controlling the on and off of a bridge arm through SVPWM.

The application belongs to the technical field of power electronic control, and particularly relates to a kind of energy storage converter parallel control method and system.The method comprises: after Clark transformation, Park transformation of three-phase voltage signal and three-phase current signal output by inverter, active power and reactive power are calculated;Reference value of voltage loop and current loop is calculated, and prediction value is superimposed on current loop to obtain direct axis front end voltage and cross axis front end voltage, and then direct axis voltage and cross axis voltage are calculated;Direct axis voltage and cross axis voltage are subjected to SPWM modulation, and inverter bridge arm switch tube is driven to turn on and off to control inverter output.The prediction value superimposed in the application can quickly compensate the reference value required by current loop when load mutates, and then maintain the stability of voltage.

This application discloses a motor harmonic suppression method based on parallel PR controllers. The method includes: acquiring the real-time speed of the motor, the D-axis error current, and the Q-axis error current; determining the switching status of each PR controller based on the real-time speed and the corresponding lower and upper speed limits; inputting the D-axis error current and Q-axis error current into the activated PR controller to obtain the D-axis harmonic compensation voltage and Q-axis harmonic compensation voltage; inputting the D-axis error current and Q-axis error current into the corresponding D-axis current loop controller and Q-axis current loop controller to obtain the D-axis voltage and Q-axis voltage; adding the D-axis harmonic compensation voltage and the D-axis voltage to obtain the D-axis target voltage; adding the Q-axis harmonic compensation voltage and the Q-axis voltage to obtain the Q-axis target voltage; and generating a control signal for driving the motor based on the D-axis target voltage and the Q-axis target voltage. This effectively reduces torque ripple and noise caused by motor current harmonics.

The application relates to the technical field of wind driven generators, in particular to a semi-direct-drive wind driven generator set. The semi-direct-drive wind driven generator set comprises a generator, a gear box, a high-frequency grounding belt and a conductive component. The generator comprises a stator base, a stator winding and a rotor component. The gear box comprises a box body and an output shaft. The box body is connected with the stator base, and the output shaft is rotationally arranged in the box body and is in transmission connection with the rotor component. The box body and the stator base are respectively grounded through the high-frequency grounding belt. The output shaft is provided with a plurality of conductive components along the circumferential direction, so that the output shaft is respectively conducted with the high-frequency grounding belt through the plurality of conductive components. The output shaft is provided with the plurality of conductive components along the circumferential direction, so that the output shaft is respectively conducted with the high-frequency grounding belt through the plurality of conductive components, the grounding discharge amount of the current is increased, the shaft voltage on the output shaft is reduced, the electric corrosion of the bearing and the tooth surface on the output shaft is avoided, the protection of the output shaft is improved, and the vibration and noise of the gear box are reduced.

The invention discloses a preheating control method for a carbon dioxide asynchronous motor compressor, which comprises the following steps of: 1, connecting a U phase, a V phase and a W phase output by a frequency converter into a motor of the compressor, and simultaneously collecting the temperature of the compressor in real time; 2, acquiring an input signal; 3, judging whether the temperature of the compressor reaches the preheating temperature or not; 4, judging whether the compressor is in a shutdown state or not; 5, judging whether the shutdown time reaches the preheating shutdown switching time or not; 6, whether the preheating one-way duration time is reached or not is judged; 7, calculating actual target current according to the temperature of the IGBT module; 8, calculating a preheating output voltage through an IP controller of a current loop according to the actual target current, and generating a corresponding output current; and 9, calculating an alpha-axis voltage and a beta-axis voltage, and outputting an SVPWM signal. According to the invention, the preheating voltage can be accurately controlled, customized current control is realized, single-phase overheating is avoided through systematic phase switching, and a safety protection mechanism is provided.

According to the present invention, a power conversion unit converts a DC voltage of a DC power supply into an AC voltage and applies the AC voltage to a rotary machine, a current detection unit detects a current supplied from the power conversion unit to the rotary machine, and a power conversion control unit issues a switching command to the power conversion unit, generates a first voltage command to be applied to the rotary machine on the basis of the detected current, calculates, on the basis of a d-axis voltage on a d-axis and a q-axis voltage on a q-axis, which are synchronized with the rotation of the rotary machine, the phase of a second voltage command so as to be equal to the phase of the first voltage command, and determines, as the amplitude of the second voltage command, a voltage limit value corresponding to the DC voltage of the DC power supply.

The utility model discloses a shaft voltage and shaft current on-line monitoring system, which relates to generator shaft voltage and shaft current monitoring and comprises a signal acquisition module, a signal processing module, a display module, an alarm module and a storage module. The signal acquisition module acquires a shaft voltage signal and a shaft current signal of the generator and sends the signals to the signal processing module, the storage module and the display module respectively; the signal processing module performs fast Fourier transform and filtering on the shaft voltage signal and the shaft current signal to obtain a processed voltage signal and a processed current signal, and sends the processed voltage signal and the processed current signal to the alarm module, the storage module and the display module; and the alarm module gives an alarm according to the processed voltage signal, the processed current signal and a preset threshold value, and sends an alarm moment signal to the storage module. According to the utility model, the monitoring accuracy of shaft voltage and shaft current can be improved, accurate fault alarm can be carried out, and safe operation of a generator can be ensured.