119 results about "Neutral point voltage" patented technology

The invention discloses a dual-electric brake boosting system, which belongs to the technical field of vehicle brake control and comprises the following steps: S1, dynamically calculating quadrature-axis inductance parameters, generating a synchronous magnetic field signal and inhibiting electromagnetic interference of dual motors; s2, extracting a harmonic-rotating speed mapping relation, and dynamically correcting an observation equation to control a parameter error; s3, reconstructing neutral point voltage to counteract high-frequency jitter, and reducing residual harmonic interference through adaptive filtering; s4, establishing a three-dimensional thermal field to predict copper and iron loss, dynamically adjusting current and generating an inverse time limit protection curve; s5, splitting the hot parameters into parity check frames, optimizing a communication protocol and compressing a refresh cycle to 10ms; s6, overlapping response of the white noise excitation system, and performing closed-loop calibration on the filtering weight to improve the observation precision; s7, triggering an audible and visual alarm and synthesizing a directional voiceprint and a tactile pulse to ensure safety regulations and perception intensity; the method has the beneficial effects that the method has remarkable advantages in a high-temperature and high-vibration severe environment, and the reliability and the safety of a system can be improved.

The invention discloses an open-phase self-fault-tolerant control method for a phase-shift-free dual three-phase permanent magnet synchronous motor. The method can automatically adjust a current distribution relation in the case of an open-phase fault and suppress torque pulsation in combination with neutral point voltage compensation. Comprising the following steps: driving two pairs of three-phase winding modules of the phase-shift-free DTP-PMSM in parallel by adopting two two-level three-phase voltage source inverters, and providing a mathematical model of the motor; current distribution is automatically adjusted; compensating the voltage of the neutral point, and calculating the offset of the fault module; the current is redistributed to suppress the torque ripple after the fault, and the secondary oblique wave component generated by the phase failure fault is eliminated; a current loop controller is improved through dead-beat predictive control; the speed ring controller is optimally designed into an improved sliding mode controller; an improved double-loop controller system is formed by combining improved sliding mode control and dead-beat prediction control, high-gain parameters are set to improve the dynamic response performance of the system, and a new self-fault-tolerant control system is formed.

The invention discloses a power distribution network grounding fault research and judgment analysis method, relates to the technical field of power distribution network fault analysis, and solves the technical problem that fault analysis is not accurate and deep enough due to the fact that fault features in a neutral point grounding complex fault scene cannot be comprehensively considered. According to the method, single-phase grounding fault models of a neutral point ungrounded system, an arc suppression coil grounded system and a small resistor grounded system are respectively constructed, grounding current, phase voltage and neutral point voltage expressions under the models are detailedly deduced, and characteristics of voltage and current before and after a fault point in the steady-state and transient-state processes are deeply analyzed; the method comprehensively considers various complex fault scenes, can more accurately grasp essential characteristics of faults in different grounding modes, and provides a more comprehensive and accurate basis for fault diagnosis and processing.

A direct-current conversion circuit, which is used for providing direct-current conversion between a first direct-current voltage and a second direct-current voltage is described. The direct-current conversion circuit comprises: a transformer, which comprises a primary-side winding and a secondary-side winding, wherein the primary-side winding comprises a center tap, and a first primary-side winding and a second primary-side winding, which are respectively connected to the center tap; a primary-side circuit, wherein a first side of the primary-side circuit is connected to the primary-side winding, a second side of the primary-side circuit comprises a first end, a second end, and a third end, and a first direct-current voltage is provided between the first end and the second end of the primary-side circuit; and a secondary-side circuit, wherein a first side of the secondary-side circuit is connected to the secondary side winding.

The invention discloses a multi-vector model predictive control method and system based on fast vector selection, relates to the technical field of power control, and solves the problem that neutral-point potential balance cannot be effectively solved while the common-mode voltage amplitude is reduced in the prior art. The method comprises the steps of simplifying sectors based on the condition that each sector causes common-mode voltage, and eliminating vectors causing serious common-mode voltage; designing a cost function, and combining the cost function with a Nelder-Mead algorithm to determine an optimal medium vector and an optimal large vector; the action time of the optimal large vector, the action time of the optimal medium vector and the action time of the zero vector are calculated, so that the optimal large vector, the optimal medium vector and the zero vector act according to the corresponding action time, and common-mode voltage suppression is achieved; introducing a negative small vector to carry out neutral point potential compensation to realize active balance; the neutral point voltage is controlled through vector synthesis, the fluctuation of the neutral point voltage is suppressed, and the problem that common-mode voltage suppression and neutral point voltage control are difficult to achieve at the same time is solved.

A method and system for measuring distribution network system parameters based on harmonic injection, for use in a low-current grounding system containing an arc suppression coil. The system injects currents of multiple frequencies into the neutral point of the low-current grounding system through an injection source and measures the neutral point voltage. The system uses formulas to calculate and obtain the line capacitance, arc suppression coil inductance, and damping resistance parameter values ​​in the distribution network system. This application can accurately measure line capacitance, arc suppression coil damping resistance, and reactance by injecting only two frequencies of current. This method has little impact on grid operation, high measurement accuracy, and broad application prospects.

The invention discloses a ground fault positioning and multi-solution screening method for a stator winding of a pumped storage unit, and belongs to the field of relay protection. The method is combined with a special structure of a stator winding of a variable-speed pumped storage unit, and a function relationship between a fault winding potential and a fault position is established by taking a slot potential as an analysis unit. In a phasor plane, by drawing a three-phase ground voltage phasor and a neutral point voltage phasor, an included angle relation between a fault point voltage phasor and the neutral point voltage phasor and a phasor triangle relation are utilized to determine an alternative fault point. And then, an optimization model for fault positioning is established, and a homonuclear molecule optimization algorithm is adopted for solving, so that accurate positioning of a plurality of alternative fault points is realized. And finally, third harmonic voltage information is introduced as auxiliary information, and a unique solution is screened out from the plurality of alternative fault points. The method is high in reliability, small in positioning result error and suitable for the positioning requirement of the variable-speed pumped storage unit stator grounding fault.

The invention discloses a self-voltage-stabilizing system and method for a power distribution network active and passive integrated ground fault regulation and control device, and the system comprises a fault judgment module, the active and passive integrated ground fault regulation and control device, an arc extinction reactive energy output module and a fault elimination module based on the active and passive integrated ground fault regulation and control device. The method comprises the following steps: measuring resistance to ground and capacitance to ground of a line during normal operation of a system, and judging whether a single-phase ground fault occurs or not; if the grounding fault does not occur, measuring the three-phase voltage and current of the load and performing split-phase injection of reactive compensation current; after the system has a single-phase earth fault, controlling the active and passive integrated earth fault regulation and control device to output active energy to be 0, and outputting reactive energy required by arc extinction according to reactive compensation current injected into the power distribution network at present; and reducing the injected arc extinction current after the time period t, and observing whether the neutral point voltage changes proportionally.

The invention is suitable for the technical field of arc extinction of a power distribution network, and provides a self-adaptive composite arc extinction method based on a zero-sequence voltage threshold value of the power distribution network, which comprises the following steps: monitoring the neutral point voltage of the power distribution network, and judging whether the power distribution network has a single-phase earth fault or not; when the single-phase earth fault does not occur in the power distribution network, injecting a first current into the neutral point of the power distribution network, and calculating an earth parameter of the power distribution network and an earth capacitance current when the voltage of the neutral point of the power distribution network is zero; when a single-phase earth fault occurs in the power distribution network, injecting a second current into the neutral point of the power distribution network, and calculating a fault point offset voltage of the power distribution network; and calculating a voltage threshold value and a corrected current arc extinction reference value based on the ground parameter, the ground capacitance current and the fault point offset voltage, if the neutral point voltage of the power distribution network is smaller than the voltage threshold value when the single-phase ground fault occurs, adopting voltage arc extinction, otherwise, adopting the corrected current arc extinction reference value to implement current arc extinction. According to the invention, the reliability of single-phase earth fault arc extinction can be improved.

The invention discloses a motor phase current sampling method and device, a chip and a motor controller, and the method comprises the steps: obtaining the duty ratio of a multi-phase bridge arm in a pulse modulation period; determining a to-be-sampled bridge arm according to the duty ratio; sampling a motor phase voltage corresponding to the to-be-sampled bridge arm in a target sampling time period corresponding to the to-be-sampled bridge arm, and determining a corresponding motor neutral point voltage; wherein the target sampling time period is a time period from the start of a dead zone corresponding to the to-be-sampled bridge arm to the completion of follow current; and determining a motor phase current corresponding to the to-be-sampled bridge arm according to the motor phase voltage corresponding to the to-be-sampled bridge arm and the corresponding motor neutral point voltage. According to the method, the sampling function of the motor phase current can be realized without phase shift and sampling point calculation, the algorithm is simple, harmonic waves are not generated, and the phase current sampling cost is relatively low.

The invention provides a neutral-point potential control method and system for a three-level converter, and relates to the technical field of intelligent control, positive bus voltage and negative bus voltage are sampled, a voltage deviation value is calculated, an additional control quantity is generated according to the voltage deviation value and a symbol of alternating current, and the additional control quantity is obtained through a symbol function and proportional control processing; performing amplitude limiting processing on the additional control quantity to obtain an amplitude-limited additional control quantity; superposing the amplitude-limited additional control quantity on the positive modulation wave, negating the amplitude-limited additional control quantity, and superposing the negated amplitude-limited additional control quantity on the negative modulation wave to obtain a final positive modulation wave and a final negative modulation wave; comparing the final positive modulation wave and the final negative modulation wave with a carrier wave, and generating a driving signal of the power device; and the on-off of the switching device is controlled according to the driving signal, so that a corresponding level is output to realize neutral-point potential balance. According to the invention, neutral-point voltage low-frequency fluctuation and direct-current offset suppression can be realized at the same time.

The invention provides a data-driven multi-target control method, device and system based on model prediction, is applied to a three-phase three-level neutral point clamped converter, and aims to realize dual accurate control of switching frequency and neutral point voltage. According to the method, a switch weight factor and a neutral point voltage weight factor are used as inputs, and an average switch frequency in a fixed sliding window time and a neutral point voltage maximum value in another fixed sliding window time are used as outputs; and constructing an equivalent dynamic linearization data model under each dynamic working point of the closed-loop system by adopting a tight-format dynamic linearization method. Based on the data model, a data driving controller is elaborately designed to realize accurate regulation and control of the switching frequency and the maximum value of the neutral point voltage. The method has a high practical value and a wide application prospect in typical application scenes of power electronics and power transmission, such as grid connection and motor driving.

The invention discloses a modulation method for a three-phase four-leg three-level inverter to eliminate the neutral point current, belonging to the field of power electronic conversion and control. The method includes: calculating the differential-mode component of the modulation waves of the three-phase bridge legs and the modulation wave of the fourth bridge leg before common-mode voltage compensation according to the voltages of the AC filter capacitors of each phase and the currents of the AC filter inductors of each phase; calculating the duty ratio of the 0 level before correction of the three-phase bridge legs according to the differential-mode component of the modulation waves of the three-phase bridge legs and determining the phase where the maximum duty ratio is located; calculating the common-mode component of the modulation waves of the three-phase bridge legs according to the phase; calculating the modulation waves of the three-phase bridge legs and the fourth bridge leg according to the common-mode component of the modulation waves of the three-phase bridge legs, and determining the actual duty ratios of the +1, -1, and 0 levels of each bridge leg; the modulation waves of the three-phase bridge legs and the modulation wave of the fourth bridge leg are respectively intercepted with the stacked carrier waves to generate the driving signals of the inverter. This method can achieve the neutral point voltage balance in the full power factor range and eliminate the low-frequency pulsating component in the neutral point voltage.

The invention discloses a control method of a current converter and a power grid system, the control method is applied to control of the current converter in the power grid system, and the control method comprises the following steps: constructing a self-adaptive hyper-local model which comprises a self-adaptive input gain and a hyper-local model, the hyper-local model comprises physical parameters in a controlled system and disturbance factors in a power grid system; an online neural network estimator is adopted to estimate the hyper-local model and the adaptive input gain, and dependence of the hyper-local model and the adaptive input gain on system parameters is eliminated; and predicting an output current of the converter based on the super-local model and the adaptive input gain, generating a voltage vector of the converter based on the predicted current of the converter, and controlling the converter by using the voltage vector. According to the invention, current tracking and neutral point voltage balance of the converter can be realized, and parameter-free operation of the control system is realized.

The embodiment of the invention discloses a distribution transformer operation gear synchronization vector online detection method and device, and the method comprises the steps: obtaining a nameplate parameter of a distribution transformer, and carrying out the calculation to obtain a short-circuit impedance value of a low-voltage side to a high-voltage side under each gear; synchronously measuring a voltage vector of the low-voltage side of the distribution transformer, an output current vector and a neutral point voltage vector; when the amplitude of the low-voltage-side zero-sequence current reaches a current detection threshold value or the module value of the low-voltage-side neutral point voltage vector reaches a voltage detection threshold value, obtaining a detection loop and combining a circuit principle and a low-voltage-side synchronous voltage vector, a synchronous current vector output by the low-voltage side and a low-voltage-side neutral point synchronous voltage vector of the distribution transformer; calculating to obtain a short-circuit impedance value of the low-voltage side to the high-voltage side; calculating to obtain the absolute value of the impedance difference value of each gear; determining the gear corresponding to the minimum absolute value of the impedance difference value of each gear as the current operation gear of the distribution transformer; the operation gear of the transformer can be accurately detected on the low-voltage side in the operation state.

The invention discloses a power transformer winding fault complex frequency domain diagnosis method and device, and the method comprises the steps: employing a neutral point voltage or current applying method, and obtaining the broadband short-circuit complex impedance of each phase of different windings of a transformer at different frequencies; according to the broadband short-circuit complex impedance of each phase of different windings under different frequencies, determining a complex frequency domain first correlation coefficient of broadband short-circuit complex impedance between different phases of different windings of the transformer under different frequencies; and performing winding fault diagnosis of the transformer according to the complex frequency domain first correlation coefficient. According to the method, the consistency of the alternating current power transformer and the converter transformer winding is detected through the correlation of the transformer winding and the complex impedance of different phases of the winding in the broadband range, weak winding faults such as winding deformation and turn-to-turn short circuit of the transformer can be found, and technical support is provided for evaluating the health state of the transformer.

The present application relates to a kind of power distribution network ground parameter and grounding transition conductance online identification method, this method utilizes the neutral point voltage during the single-phase ground fault of power distribution network and the compensation current information injected by active inverter (active inverter in abstract drawing is taken as an example with cascaded H bridge), combined with recursive least square method and limit approximation idea, obtain the online measurement formula of power distribution network ground capacitance, ground resistance, grounding transition conductance, simultaneously introduce variable forgetting factor strategy on the basis of recursive least square method, improve the anti-interference ability of algorithm.The method of the present application can realize the integration of active inverter parameter measurement and arc extinction, using the ground parameter and grounding transition conductance information of online identification, adapt to line operating condition change and improve the arc extinction effect under the ground fault of power distribution line change, quickly judge the moment when ground fault disappears, reduce the overvoltage risk of non-fault phase equipment caused by long time input of active inverter during arc extinction.

The invention provides an inverter output electric power regulation and control method, device and equipment and a storage medium, and particularly relates to the technical field of inverter output electric power regulation and control. The method comprises the following steps: a processor obtains a direct current bus voltage of an nth switching mode of the inverter, a floating ground capacitor voltage of the nth switching mode at a (k + 1) th moment and an inverter neutral point voltage of the nth switching mode at the (k + 1) th moment; calculating to obtain a cost value of the nth switching mode; comparing the cost values of every two switching modes in the cost values of the first n switching modes to obtain a minimum cost value; and regulating and controlling the output electric power of the inverter according to the floating ground capacitor voltage corresponding to the minimum cost value and the neutral point voltage of the inverter. According to the method, the harmonic content of the output voltage of the inverter is reduced, the fluctuation of the output voltage of the inverter is reduced, the stability of the output voltage of the inverter is improved, and the accuracy and stability of the output electric power of the inverter are further improved.

Adjustable frequency drives (AFDs) and methods of operating the same are described. An AFD includes a plurality of inverters having first terminals that are coupled to respective phases of a motor and having AC output terminals connected to one another at an AC neutral node. A voltage at the AC neutral node is detected. A root-mean-squared (RMS) voltage measurement is generated from the detected voltage. A potential ground fault is identified responsive to the generated RMS measurement. The AFD is controlled responsive to identification of the ground fault. Identifying a potential ground fault responsive to the generated RMS voltage measurement may include comparing the RMS voltage measurement to a reference value.

The present application relates to the technical field of small current grounding line selection, and provides a small current grounding line selection auxiliary increment device and method, a grounding transformer module for providing a neutral point for a target power system; the target power system is a system without grounding of the neutral point; a neutral point voltage detection module for detecting the voltage of the neutral point when a grounding fault occurs; an auxiliary increment module for selecting a corresponding input resistor according to the size of the voltage of the neutral point when the grounding fault occurs, so as to obtain an increment current matched with the voltage of the neutral point; the input resistor is used for connecting the neutral point; and a zero sequence current detection module for judging the grounding fault according to the increment current matched with the voltage of the neutral point. Through the above technical solution, the problem that the grounding line selection cannot be accurately judged according to the zero sequence current in the related art is solved.

The present invention relates to the technical field of multilevel inverters, and specifically relates to a modulation method for a multilevel inverter with active control and common-mode voltage suppression. This method changes the sector division method based on the SVPWM space vector diagram, determines the large sectors and small regions by calculating the amplitude and angle of the reference vector; synthesizes the virtual vectors required for each sector based on the virtual vector synthesis principle; selects different virtual vector synthesis schemes based on the neutral point voltage deviation; calculates the action time of the virtual voltage vector according to the volt-second balance equation and distributes it to each basic voltage vector. The present invention can perform neutral point voltage balance control for any large sector and small region, and all controls are implemented through software without adding any hardware facilities, greatly reducing the control cost.

The invention belongs to the field of regulation and control of standby power supply loop devices, and provides a low-cost converter regulation and control method and system for a standby power supply system, and the method comprises the steps: sampling load voltage and current, inductive current, and DC side upper and lower capacitor voltage; selecting inductive current to perform decoupling operation, calculating expected output voltage of the converter based on a dead-beat control principle, and performing normalization processing; determining a sector with an optimal size according to an amplitude condition and a boundary condition of the expected output voltage; based on discrete space vector modulation, selecting a low common-mode voltage vector to synthesize a virtual small vector and a virtual medium vector, and expanding a candidate vector set; determining a switching sequence at the next moment according to the large and small sectors where the expected output voltage is located and the voltage difference value of the upper and lower capacitors on the direct current side to balance the neutral point voltage and the fixed switching frequency; and calculating the action time of the voltage vector according to the value function, outputting the duty ratio of the voltage vector, and applying the duty ratio to a switching device of the converter.

The invention relates to a power distribution network fault identification method and device, computer equipment and a storage medium. The method comprises the following steps: acquiring bus voltage of a bus on a power distribution network; determining the fault condition of the power distribution network according to the bus voltage; under the condition that the power distribution network breaks down, neutral point voltages of a neutral point on the power distribution network under different power frequency currents are obtained; the neutral point is a common point of three-phase connection on the power distribution network; and determining the fault type of the power distribution network according to the neutral point voltage under different power frequency currents. By adopting the method, the fault type of the power distribution network can be effectively and accurately identified, so that the troubleshooting time is shortened.

The invention provides an overvoltage tuning method and system based on parallel cooperation of a resistor and an arc suppression coil. The method comprises the following steps: judging an event type according to a neutral point voltage; when the event type is that the operation mode is changed, performing first tuning based on a first preset rule, and judging whether the neutral point voltage after the first tuning is greater than a threshold value or not; if the neutral point voltage after the first tuning is greater than the threshold value, performing secondary tuning based on a second preset rule, and judging whether the neutral point voltage after the secondary tuning is less than the threshold value; if the voltage of the neutral point after secondary tuning is larger than or equal to the threshold value, a second preset rule continues to be executed until the voltage of the neutral point after secondary tuning is smaller than the threshold value, and if the voltage of the neutral point after secondary tuning is smaller than the threshold value, it is judged that damping succeeds, and the resistance grounding device is reset. According to the invention, a unified zero-sequence impedance regulation and control strategy is established through cooperation of arc suppression coil operation and damping, so that the probability of occurrence of tuning overvoltage is reduced.

The present invention discloses a method and device for model predictive control of rectifier harmonic suppression based on current variance. This method realizes the indirect control of current harmonics by controlling the current variance. Through offline experiments, the relationship between the load current and the current variance under different current harmonics is measured, and the functional relationship between the two is obtained by curve fitting, avoiding the harmonic calculation link and reducing the computational load. This method can achieve the equivalent control of current harmonics with a relatively small computational load. In addition, in model predictive control, through hierarchical control, the computational complexity is reduced, the design of weight coefficients is avoided, and the balanced control of the neutral point voltage is achieved. By setting a satisfaction interval, the control target is limited within a certain fluctuation range, enabling the control strategy to obtain a higher control freedom and achieving the global optimum of the control effect.

The present invention discloses a method and system for neutral point balance and circulating current control of an interleaved parallel three-level converter. By equally distributing the neutral point voltage balance control quantity to the first three-phase converter and the second three-phase converter connected in parallel between the bridge arms of at least one interleaved parallel three-level converter, and equally and reversely distributing the zero-sequence circulating current control output to the first three-phase converter and the second three-phase converter, and on this basis, correcting the amplitude of the injected zero-sequence voltage, the coordinated control of zero-sequence circulating current and neutral point balance can be ensured, which is of great significance for the development of converter parallel connection.

The present invention provides an inverter fault-tolerant and neutral-point voltage balance control method based on modulation wave decomposition, which generates an initial modulation wave and injects a zero-sequence component into the initial modulation wave; analyzes the current path in the case of a switch tube fault, and divides a fundamental wave period into a healthy half-cycle and a fault half-cycle according to the fault-phase current direction; in the healthy half-cycle, decomposes the modulation wave of the middle phase and calculates the control quantity; in the fault half-cycle, performs carrier reconstruction, does not use non-existent switching states, selects the optimal decomposition phase according to the neutral-point voltage, the non-fault-phase current direction, and the control force, and calculates the control quantity, and decomposes the modulation wave according to the calculated control quantity. The present invention reconstructs the carrier according to the fault-phase current direction to achieve fault-tolerant control, and reasonably selects one of the three-phase modulation waves for decomposition to adjust the neutral-point current, realizes the decoupling of fault-tolerant control and neutral-point voltage balance control, and ensures the safe and reliable operation of the inverter system.

The application discloses an asymmetric medium-voltage three-phase distribution network probability power flow calculation method containing single-phase photovoltaic access, and comprises the following steps: 1, based on historical power data of photovoltaic, weight values are obtained by an improved entropy weight method, and then the output probability density function of distributed photovoltaic is obtained by LightGBM prediction; 2, for the medium-voltage three-phase distribution network with single-phase photovoltaic access, the uncertainty of photovoltaic output and access position is considered, the neutral point voltage is alternately iterated with Newton method, and a three-phase distribution network power flow model is constructed; 3, integral points and weights of point estimation method are determined, space transformation is carried out by Nataf inverse transformation, and power flow distribution is obtained from the three-phase distribution network power flow model; each order statistical moment is calculated, Gram-Charlier series fitting is adopted, and the probability distribution of the distribution network system is obtained. The application considers the influence of uncertain single-phase photovoltaic access to obtain the probability power flow distribution, and has positive significance for the study of power flow, probability optimization problem, system operation and safety evaluation of the neutral point not directly grounded distribution network system.

The present application relates to a kind of small current grounding fault active arc extinguishing when fault point arc extinguishing detection method, comprising the following steps: after detecting that small current grounding fault occurs, gradually increase the amplitude of neutral point voltage by active inverter control, make the voltage of fault phase gradually reduce;During the process of gradually increasing the amplitude of neutral point voltage, the injection current of active inverter and the corresponding bus zero sequence voltage at different time are measured and recorded in real time, the change value of injection current and bus zero sequence voltage are obtained by calculating the change of adjacent two different time measurement values, and the power frequency component is extracted by the change value of injection current and bus zero sequence voltage;Based on power frequency component, the admittance and impedance angle of system are calculated;According to impedance angle and the preset impedance angle threshold value, whether the fault point is arc extinguished is judged.

The application provides a calibration method, device and equipment of a brushless direct current motor and a storage medium, and relates to the technical field of direct current motors. The method comprises the following steps: determining whether the comparison threshold of each phase winding is calibrated according to the calibration data of the phase windings, the comparison threshold of each phase winding being used for back electromotive force zero-crossing detection of the phase windings; if the comparison threshold corresponding to each phase winding is calibrated, input voltage parameters of the phase windings are obtained; according to the input voltage parameters of the phase windings and corresponding neutral point correction constants, target neutral point voltage parameters corresponding to the phase windings are determined, so that the comparison threshold of the phase windings is set according to the target neutral point voltage parameters. Compared with the prior art, the control error caused by the parameter imbalance between the phase windings of the motor is avoided, and the problem of affecting the control efficiency of the brushless direct current motor is solved.