152results about How to "Easy to implement digitally" patented technology

The invention belongs to the field of power converter control and relates to a model prediction control method of a voltage source type rectifier when a network voltage is unbalanced. The model prediction control method of the voltage source type rectifier when the network voltage is unbalanced comprises the steps of converting three-phase network voltage and a three-phase current into network voltage and a current which are under a two-phase static coordinate system through an abc / alpha beta coordinate, obtaining network positive sequence voltage and negative sequence voltage by carrying positive and negative sequence component separation of the network voltage under the two-phase static coordinate system, calculating reference values of active power, calculating current reference values of the rectifier under the two-phase static coordinate system, and carrying out model prediction current control and selecting an optimal on-off state. The model prediction control method of the voltage source type rectifier when the network voltage is unbalanced is capable of quickly and precisely tracing the current under the two-phase static coordinate and effectively eliminating fluctuation of direct current side voltage at the same time, power quality of the system is improved, a reliable network-connected operation of the rectifier when transient state network voltage is unbalance is achieved, and dynamics and stability of the whole system are improved.

The invention discloses a control method of a four-phase permanent magnet fault-tolerant motor. In the method, a control mode can be automatically decided according to the diagnosed situation of a system failure; when the system is at a normal state, an SVPWM control is adopted; when the system has a phase-lacking failure, a fault-tolerant torque control is adopted; different fault-tolerant control proposals are adopted according to different types of phase-lacking failures. The control method realizes that the four-phase permanent magnet fault-tolerant motor can operate with high performance under the normal condition and the phase-lacking condition, overcomes the deficiency that the stable performance of the system when in normal working is reduced in the traditional fault-tolerant control system which adopts current for regulating PWM for realizing current tracing for the convenience of fault-tolerant control, establishes a mathematical model of the four-phase permanent magnet fault-tolerant motor under a rotating coordinate system, successfully applies an SVPWM strategy to the four-phase permanent magnet fault-tolerant motor and enhances the dynamic and static performances and reliability of the control system of the four-phase permanent magnet fault-tolerant motor.

The invention relates to an idling slide protective control method of a locomotive. The method comprises the following steps of: detecting the acceleration d omega / dt of a locomotive wheel pair in real time, when the acceleration exceeds a protective threshold, i.e. domega / dt is more than ag, starting to unload a moment, and continuously searching the peak value of the acceleration, i.e. when d<2>omega / dt<2>=0 in the unloading process, searching the peak value; and instantly stopping to unload the moment when the peak value is searched, wherein the change rate of a motor torque dT / dt is 0, the adhesion of a locomotive wheel track recovers again and the change rate of the adhesive force of the locomotive wheel track dF / dt is more than 0. The invention can overcome the over-deepness unloading problem very well in the prior art, the problem cause the locomotive tractive effort loss to be great, affects the adhesion utilization of the locomotive and causes the front and back impacts of the locomotive.

The invention provides a method and a system for over-modulating three-level space vectors. The method comprises the following steps: calculating the modulation ratio and angle of a reference voltage; dividing the modulation ratio into a first setting interval and a second setting interval; positioning the modulation ratio in the first setting interval and calculating the duty cycle of a short vector, a long vector and a medium vector by intervals according to the angle of the reference voltage; correcting the duty cycle of the short vector, the long vector and the medium vector respectively according to the magnitude of the short-vector duty cycle; calculating the N-action duty cycle and the P-action duty cycle of each phase according to the corrected duty cycle; positioning the modulation ratio in the second setting interval and calculating the keeping angle of the reference voltage; calculating the N-action duty cycle and the P-action duty cycle of each phase by intervals according to the resulting of comparing the keeping angle with the angle of the reference voltage; and conversing the N-action duty cycle and the P-action duty cycle of each phase into action time and mapping the action time back to the prior sector. The method and the system have the advantage of ensuring that SVPWM over-modulation is simple in calculation steps and higher in modulation precision.

The invention provides a pseudo code capturing method and device using multiple antennae of a direct sequence spread spectrum system. The method comprises the following steps: (1) each antenna uses one capture branch to determine self-adaptive weight vector by combining capture branch output according to the space correlation matrix of the received signal acquired by each antennae; (2) the capture branch output is subjected to weighted sum by using the self-adaptive weight vector in the step (1) so as to output decision statistics; and (3) the captured decision statistics is compared with a threshold to make a decision, if the captured decision statistics is more than or equal to the threshold, a tracking phase is carried out; otherwise, the PN code phase position of a local PN code relatively to the received signal is converted and the above processes are repeatedly carried out. The device comprises an analog digital conversion unit, digital down-conversion unit, a correlator unit, a captured decision statistic calculation unit and a threshold comparison unit. The device has the advantages of simple structure, strong interference resistance, independent decision threshold to signal-to-interference and noise ratio and the like.

The invention discloses a multi-level inverter grid-connection method and apparatus based on fixed frequency finite set model prediction. The multi-level inverter grid-connection method comprises thesteps of performing sampling on a three-phase network-in current and a three-phase network voltage, and performing Clark conversion on the sampled values; and next, by adopting a fixed frequency modelprediction algorithm, performing tracking control on the three-phase network-in current and direct current side neutral-point voltage suppression in a condition of maintaining constant switching frequency. The apparatus comprises a main power circuit, a control circuit and a detection circuit, wherein the main power circuit comprises an NPC three-phase three-level inverter and an L-shaped low-pass filter; and the detection circuit comprises a network-in current detection circuit, a network voltage detection circuit and a direct current side neutral-point voltage detection circuit. The finiteset model prediction grid-connection control of the multi-level inverter can be realized in a condition of maintaining constant switching frequency.

The invention discloses a control method for a permanent magnet synchronous motor based on current prediction and belongs to the field of control over permanent magnet synchronous motors. The method mainly comprises the steps of predicting the improved current and identifying the sensorless rotating speed and a corner based on a phase-locked ring idea combined with the predicting step. According to the control method, the current of a motor stator is predicted ahead of a switch period according to the detected current of the motor stator and a current instruction; corresponding control voltage is predicted; and motor rotating speed and corner position information is identified according to the estimated counter electromotive force of the motor. The invention further provides a control system for realizing the control method. The control system comprises a rotating speed regulator, a current predicting unit, a counter electromotive force estimation unit, a controller and a space vector modulating unit. According to the control method and the control system disclosed by the invention, the permanent magnet synchronous motor can be enabled to still safely operate at high efficiency when the parameters change; and the control method and the control system have a favorable application prospect in the field of control over the permanent magnet synchronous motor.

The invention discloses a model prediction control method and apparatus of a NPC three-phase three-level grid-connected inverter. The method includes the following steps: conducting Clark transformation on sampling values of a three-phase networking current and a three-phase grid voltage; using a DOSGI-SPLL module and a grid voltage feature value extraction module to obtain a grid voltage feature value which is required in computing a networking reference current; using the two-step prediction method to conduct tracking control and DC side neutral-point voltage suppression on the three-phase networking current so as to compensate the delay which is caused by sampling and computing. The apparatus includes a master power circuit, a control circuit and a detection circuit. The master power circuit includes a NPC three-phase three-level inverter and an L-shaped low pass filter. The detection circuit includes a networking current detection circuit, a grid voltage detection circuit and a DC side neutral-point voltage detection circuit. According to the invention, the method can realize excellent grid-connected control of the NPC three-phase three-level inverter under non-ideal grid conditions, can greatly increase networking electricity quality and at the same time effectively suppresses fluctuation of DC side neutral-point voltage.

The invention provides a method for eliminating time-domain narrowband interference of a direct sequence spread spectrum communication system, which comprises the following steps of: 1) dividing received spread spectrum signals into two paths of same signals, wherein one path of signals are delayed and then output to an interference estimating module, and the other path of signals are taken as reference signals; 2) estimating interference signals in the first path of the spread spectrum signals by a transverse filter with unequal interval taps through a time-domain arithmetic, and outputting the interference signals; and 3) subtracting the interference signals from the reference signals, and obtaining the spread spectrum signals of which the narrowband interference is eliminated. In addition, the invention also provides a device for eliminating the time-domain narrowband interference of the direct sequence spread spectrum communication system. The method and the device have the advantages of little computation workload, no need of complicated hardware structure and easy digitalization. The transverse filter with the unequal interval taps can adapt to estimating more types of narrowband interference, and solves the problems of complicated realization of variable tap intervals and poor system continuous work performance at the same time.

The invention discloses a sensorless control method of a permanent magnet synchronous motor, and belongs to the field of motor control. In the method, a pulsating high frequency voltage signal is injected, and the position and rotating speed of a motor rotor are estimated from high frequency current response. The method comprises the following steps of: generating a high frequency voltage signal vh and injecting the high frequency voltage signal in an estimated (the formula is described in the specification) shaft system, generating a signal modulation array Am; sampling the current of a stator winding by a current sensor, performing coordinate transformation, and extracting high frequency components (the formula is described in the specification) and (the formula is described in the specification); multiplying (the formula is described in the specification) with the signal modulation array Am to obtain a target value Pv1, and obtaining a magnetic pole position estimated value (the formula is described in the specification) and a rotating speed estimated value (the formula is described in the specification); multiplying (the formula is described in the specification) with the signal modulation array Am to obtain a target value Pv2, judging the polarity of a magnetic pole, compensating (the formula is described in the specification), and outputting a rotor position estimated value (the formula is described in the specification). By virtue of the method, the position identification during zero speed and low speed can be realized, no filter is used in the identification process, the system stability and the identification precision are improved, and the dynamic performance is improved; a saturated working point is selected according to the motor power, and the reliability of polarity judgment is improved; the algorithm complexity is low, and digital realization is easy.

The invention discloses an active power filter for detecting a harmonic wave and a wattless current and a detecting method thereof. The active power filter comprises a harmonic wave and wattless current detecting circuit and a compensating current generating circuit, wherein the harmonic wave and wattless current detecting circuit and the compensating current generating circuit are successively connected in series at the current side of a power grid. The compensating current generating circuit comprises a current tracking control module, a driving circuit module and a main circuit module, wherein the current tracking control module, the driving circuit module and the main circuit module are successively connected in series. The topological structure of the main circuit module is a three-phase four-leg PWM converter. Compared with prior art, a novel harmonic wave detecting algorithm according to the invention does not require a phase-locked loop or matrix transform, thereby effectively prevent a zero-sequence harmonic leakage error caused by coordinate conversion, greatly improving detecting precision and greatly improving compensation effect.

The invention discloses a carrier offset-based control method for the mid-point voltage balance of a multilevel inverter. The method comprises the following steps: detecting a capacitance transient voltage between the midpoint and the anode and a capacitance transient voltage between the midpoint and the cathode of a direct-current bus of the multilevel inverter by a sampling unit of a digital processing control module, and determining the bias of the two capacitance transient voltages; regulating the carrier offset of the current moment through a carrier offset control regulating unit; outputting a control regulating signal of the carrier offset control regulating unit to an SVPWM (space vector pulse width modulation) vector control unit; outputting a PWM signal through a drive circuit to control the working condition of the multilevel inverter, and meanwhile, controlling the mid-point voltage balance of a multilevel inverter. According to the carrier offset-based control method disclosed by the invention, on the basis that an original SVPWM control method is kept, the mid-point voltage balance is controlled only by changing the carrier offset without increasing the complexity of the control method, so that output voltage and current harmonics can be reduced, and the output waveform quality is increased. The carrier offset-based control method has the advantages that the real-time performance is good, the processing procedure is simple and realization is easy.

The invention discloses a frequency wide-range self-adaptive repetition control method of an active power filter. First of all, voltage frequency signals of a power network are tracked in real time through a phase-locked loop, under the condition that a switch frequency is unchanged, the ratio of the switch frequency to a real-time power network frequency is calculated, finally, the integer portion of the ratio is taken as a number of beats of a fundamental wave lag of an improved repetition controller, and the decimal portion of the ratio forms a time-delay link which is approximated by use of a one-order inertia link, such that under the condition that the power network frequency fluctuates, it is ensured that the resonance frequency of the repetition controller is consistent with the actual fundamental wave and harmonic frequency of the power network, and thus the compensation effect of the active power filter in case of fluctuations of the power network frequency is not reduced.

The invention discloses a method for controlling quasi-Z resource inverter DC bus voltage based on straight-through duty ratio prediction. Through measuring values of inductor current and capacitor voltage of a current control cycle, combined with an expected DC bus voltage value, based on an established prediction model, a straight-through duty ratio needed by a next control cycle is directly predicted for a modulator, a corresponding switching function is outputted to an inverter bridge under the modulation strategy of a quasi-Z source inverter, and a fixed switching frequency is obtained. Since the evaluation of an evaluation function for each switching state is not needed, the computational load is greatly reduced, and the corresponding control can be completed without a high switchingfrequency. Since the switching function is obtained through the modulator, the switching frequency is fixed, and the switching function and a PI adjustor can use the same modulator. The control strategy instantly responds to the state of the next control cycle based on the voltage and current at the moment, and the dynamic response for a system is quick.

The invention discloses an NPC three-level inverter optimal sequence model prediction control device and method. The device comprises an NPC three-phase three-level inverter, a digital processing control module and a driving circuit, wherein the digital processing control module comprises a sampling unit, a sector pre-selection unit, a vector action time calculation unit, a prediction calculationunit and a modulation unit. The method comprises the following steps of: calculating a reference voltage vector and carrying out sector selection on a pre-generated three-vector sequence, calculatingincrements of the current and the neutral-point voltage according to the sampling information, calculating vector action time and correcting the vector action time, predicting, calculating and selecting an optimal vector sequence and action time, and generating a switching signal by the modulation unit to drive the NPC three-phase three-level inverter to work. The method is low in hardware cost, accurate in control and wide in application range, fixed switching frequency grid-connected control over the NPC three-phase three-level inverter can be achieved, the total harmonic distortion rate ofthe network access current is reduced, and meanwhile fluctuation of the midpoint voltage of the direct-current side is effectively restrained.

The invention discloses a permanent magnet synchronous motor sensorless control method with pulse high-frequency injection, and belongs to the motor control field. The high-frequency signal generatorgenerates a high-frequency voltage signal and injects the high-frequency voltage signal into an estimated d-axis coordinate system. The stator winding currents ia, ib and ic are sampled by the currentsensor and transformed into a coordinate system rotating synchronously with the estimated position to obtain d-q-axis currents id and iq; According to the obtained iq, the position error informationis extracted by using the moving average filter, and the rotor position estimation value is calculated. Based on the obtained id, the magnitude of the current is calculated using the moving average filter, and the polarity of the rotor magnetic pole is determined. This method can realize the position identification at zero speed and low speed. The bandpass filter and low pass filter are omitted inthe signal processing process, and the stability and dynamic and static performance of the system are improved. The sliding average filter is easy to realize digitally and only needs to complete thewindow length design, thus simplifying the signal processing process.

The invention belongs to the field of controlling power converters of wind power generation systems and relates to a deadbeat power control method for a grid-side converter under network voltage unbalance. The deadbeat power control method comprises the steps that three-phase network voltage, a three-phase alternating side current and direct current side voltage of the grid-side converter are detected, a network voltage sampling value and an alternating side current sampling value under a two-phase rest frame through 3 / 2 coordinate transformation, and network voltage retardation is obtained by delaying one fourth of a power grid period of the network voltage sampling value; an active power reference value is calculated, and an alternating side current reference value is calculated and obtained; transformer alternating current side voltage controlled by the deadbeat power is calculated; in order to compensate for time delay in the calculation and control process, the transformer alternating current side voltage at the next moment is predicted and serves as control voltage; a switch signal controlling a power switch component is obtained and is used for controlling on-off sequence and on-off time of the power switch component. According to the deadbeat power control method for the grid-side converter under network voltage unbalance, the grid-side converter can be effectively controlled to have good dynamic and static characteristics under the condition of network voltage unbalance, and reliable grid connection operation of a wind generating set is ensured.

The invention belongs to the technical field of microelectronics, and in particular relates to a VCO (voltage controlled oscillator), and a test system and a test method for detecting technological fluctuation. The VCO comprises a ring oscillator and a current controlled MOS (Metal Oxide Semiconductor) tube, wherein the ring oscillator comprises odd number of CMOS (Complementary Metal-Oxide-Semiconductor Transistor) phase inverters; a bias voltage is input at a grid end of the current controlled MOS tube so that the current controlled MOS tube is worked in a sub-threshold region, the current flowing through one CMOS phase inverter is further controlled, and therefore the output frequency of the VCO reflects the threshold voltage of the current controlled MOS tube. The test system is formed based the VCO. The random fluctuation value of the threshold voltage among different MOS tubes inside a chip is tested by using the test method provided by the invention. The VCO has the advantages that a circuit is simple and the digitization is easy to achieve. When the technological fluctuation is tested by using the testing system based on the VCO, the random fluctuation value of the threshold voltage with high sensitivity can be obtained, and the test accuracy is good.

The invention relates to an iteration demodulation decoding method of encoded modulation signals based on climax frequency deviation compensation, effectively solving the problem of iteration demodulation decoding of an LDPC (Low Density Parity Check Codes) encoded BPSK (Binary Phase Shift Keying) modulation system under frequency deviation and an unknown-phase channel. The method comprises the following steps of: receiving one frame of a full frame of encoded modulation signals, and dividing the full frame into a plurality of signal subblocks; initializing the external information of encodedbits; carrying out frequency deviation estimation by adopting a revised M&M arithmetic according to the external information of the encoded bits and the sample value of the received one-frame signals; carrying out a Tikhonov demodulation arithmetic to complete signal demodulation according to the structure of the signal subblocks and the frequency deviation estimation, and outputting a demodulation soft value of the encoded bits; receiving the demodulation soft value by a decoder, completing decoding once according to a confidence coefficient transmission decoding arithmetic, and outputting the external information of the encoded bits; and outputting a decoded value when the iteration demodulation times reach the preset times, and otherwise, increasing the length of the signal subblocks and repeating the operation until decoding is successful or iteration times achieve the regulated value.

The invention discloses a novel sampling method for generating SPWM (sinusoidal pulse width modulation) control signals. The method includes: constructing virtual sampling points according to the linear combination mode in mathematics to reduce the number of sampling points in reality; getting an appropriate value of a natural intersection time of a carrier wave and a modulated wave by the linear extrapolation operation method to obtain higher pulse width control accuracy; and completing control on opening and closing of each power tube in a rectifier (inverter). The number of the sampling points in the sampling method is consistent with that in conventional symmetric regular sampling methods, but pulse width accuracy of the sampling method is higher than that of conventional regular sampling methods, variable-polarity regular sampling, two-point-type regular sampling, four-point-type regular sampling, linear combination sampling, linear extrapolation sampling and the like which are commonly used, and harmonic content of output voltage in the sampling method is small; on the basis of a DSP (digital signal processor), hardware designing is easy to program and good in man-machine interactivity, a program can be flexibly modified to meet requirements under various occasions, and the novel sampling method is mainly applied to rectifiers and inverters.

The invention discloses a current stress optimization double-phase-shift control method for a double active full-bridge DC-DC converter, including the following steps: constructing a state average space equation of the output voltage of a double active full-bridge DC-DC converter according to an average model of the output voltage; discretizing the differential term of the output voltage in the state average space equation of the output voltage to obtain a predicted value of the output voltage of the converter; obtaining the internal phase shift D1 of the converter under a current stress optimization control strategy according to the Lagrange function and a power model of the double active full-bridge DC-DC converter under double-phase-shift control; constructing an evaluation function J according to the predicted output voltage and a reference voltage; and taking the derivative of the evaluation function J to obtain the external phase shift D2 of the double active full-bridge DC-DC converter under a current stress optimization double-phase-shift predictive control strategy. The method of the invention has the advantages of fast dynamic response, high efficiency, simple control process, easy digital realization and the like, and has strong practicability.

The invention discloses a quasi frequency peak current control method applied to a BUCK circuit. Output voltage and inductive current signals are acquired, switch on time and off time are obtained by a quasi frequency control method, switch control signals are generated, and a BUCK converter is controlled. A control system comprises a data acquisition module 01, an outer ring voltage PI (proportional-integral) controller module 02, a slope calculation module 03, an on and off time calculation module 04 and a modulation module 05. The slope of inductive current is calculated when a switch is turned on and off, the on time and the off time are calculated, the switch control signals are acquired by the modulation module, the BUCK converter is controlled, and steady and transient performances of the BUCK converter are improved by the quasi frequency control method.

The invention discloses a novel five-level inverter seven-segment type SVPWM modulation method. The method mainly comprises the steps of sector distinguishing, sector rotating and normalizing, small triangular area distinguishing, vector function time calculating, seven-segment vector output signal control signal generating, seven-segment three-phase voltage space-vector outputting and dead zone controlling and decoding. The novel five-level inverter seven-segment type SVPWM modulation method has the advantages that a five-level inverter SVPWM algorithm is easy to understand, calculation is simplified greatly through the sector normalizing processing, and due to the fact that no trigonometric function calculation is contained in the whole achieving process of the algorithm, digitization is convenient to achieve. The algorithm is easy to achieve regardless of whether a DSP or an FPGA is adopted, the algorithm can be expanded to the SVPWM modulation of more level inverters easily, and the novel five-level inverter seven-segment type SVPWM modulation method has important practical value to an alternating current variable frequency system.

The invention discloses a predictive control-based permanent magnet synchronous motor composite current control system and method. According to the system and method of the invention, the actual angular speed omega of a motor and the given reference rotational speed omegar of the motor, adopted as variables, are inputted to a PI rotational speed loop control module; the PI rotational speed loop control module calculates the difference of the actual angular speed and the reference rotational speed; by means of the proportional plus integral action of a rotational speed loop, the output currenti<*>q of the module is adopted as a q-axis reference current value; the three-phase output current of the motor is subjected to Clark transformation, the current of the motor in a two-phase stationaryalphabeta coordinate system is obtained, and the current is subjected to Park coordinate transformation, so that two-phase current under a dq rotating coordinate system is obtained; and reference current under a motor dq coordinate system and the two-phase current under the dq rotating coordinate system are inputted to a predictive current controller. According to the system and method of the invention, deadbeat predictive control and equivalent interference input are adopted. The current controller of the method can be applied to a PMSM torque or rotational speed driving system, has high current tracking performance and can quickly adjust the system when the system is subject to disturbance, so that the system will not be affected by a variety of disturbance factors.

The invention relates to the field of control of induction motors and discloses a control method and device for directly controlling a torque of the induction motor. In the method, an electrical signal of a given torque angle and a feedback torque angle reaches a space vector modulation generator (SVM) for processing through a difference controller via an expect voltage vector generated by a voltage space vector estimator and then a switch signal of an inverter is transmitted for driving the induction motor. The device is connected with a given torque angle controller through a first input end of a difference controller; a second input end of the difference controller is connected with a first path of output end of a corner magnetic chain observer; and the difference controller is connected with the inverter through the voltage space vector estimator and the space vector modulation generator (SVM). According to the method, the torque control of the induction motor is realized and two adjustors for a magnetic chain and torque control are omitted, so that a control system has a simple structure; in addition, the design difficulty is reduced and the production cost is low.

The invention is concerned with the harmonic current prediction method for compensating the controlling time-lapse, belongs to the harmonic current compensation technique field. Firstly, it measures the loading current instantaneous value in real time and low passes the filtering, and gets the phase corner of the electric-net voltage by phase-locked loop at the same time; predicts the current volume of the sampling time currently according to the electricity-net current phase corner and the fitting parameter vector; adjusts the fitting parameter vector according to the predicted error; then, according to the adjusted fitting parameter vector, the electricity-net voltage phase corner and the requested compensatory controlling time-lapse, it can predict the loading current volume of the tk+DeltaT time; and predicts the request compensatory harmonic current signal of the tk+DeltaT at last.

This invention relates to an iterative demodulation method and the device for the coding modulation system with output foreign information. An initial phase estimation module estimates an initial value of the phase and M2M4 evaluator gets the rough estimation of the amplitude and noise variance, the two values of which start a phase / offset tracing module outputting a tracing phase to a channel signal rectifier to be output to the amplitude / noise variance estimation module which starts its work to get a more accurate variance estimation sent to the iterative decoder to finish a process of iterative demodulation and decode to start the two modules for the next time iterative demodulation and decode to its foreign information.

The split signal received in the channel is transferred to two sub decoders. With the channel receiving signal being received, the subdecoder 1 calculates out the external information and the information bits size of the equivalent system by using the module in soft-in and sort-out. The sub decoder 2 receives the said information from the output of the decoder 1. Then, the sub decoder 2 calculates and outputs the external information, transferring the information to the decoder 1. Thus, one time of iteration is completed. When the number of iteration reaches a preset value, with the interlacement of the external information output from the decoder 2 being removed, the hard decision is carried out to obtain a estimate value for each information bit, and the decoding procedure is completed.The invention features simple, practical and easy to implement in digital format, suitable to wireless and satellite communications area.

The invention discloses a neutral-point voltage control system for parameter on-line tuning and a neutral-point voltage control method for parameter on-line tuning. The neutral-point voltage control system comprises a three-level inverter and a digital processing control module, wherein the digital processing control module comprises a sampling unit, a digital phase-locked loop unit, an output loop-closed control unit, a PI parameter online tuning unit, a neutral-point voltage PI control unit and an SVPWM (Space Vector Pulse Width Modulation) vector control unit; the output end of the SVPWM vector control unit is connected with each phase bridge arm of the three-level inverter through a driving circuit. The direct-current bias of the neutral-point voltage and the neutral-point voltage fluctuation can be restrained by the system and the method, so that the neutral-point voltage balance control can be realized.

The invention provides a three-phase voltage type PWM inverter control method. The three-phase voltage type PWM inverter control method includes following steps: firstly, a three-phase voltage type PWM inverter mathematical model is established; secondly, the three-phase voltage type PWM mathematical model is analyzed based on a synthetic vector via the introduction of the thought of the synthetic vector; thirdly, a control strategy obtained by analysis based on the synthetic vector is converted to a synchronous rotation d-q coordinate system, and a decoupling control method of a current inner loop of the three-phase voltage type PWM inverter without inductance parameters is obtained; and fourthly, a voltage outer loop control strategy of the three-phase voltage type PWM inverter is designed. According to the three-phase voltage type PWM inverter control method, no-inductance-parameter complete decoupling of the current inner loop is realized, and the control performance is guaranteed.