76 results about "Neutral point voltage" patented technology

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 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 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 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 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 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.

The application discloses a four-bridge-arm driving permanent magnet synchronous motor parameter identification method based on d-axis current injection, which comprises the following steps: obtaining a q-axis current reference value according to a rotating speed ring; calculating a d-axis current reference value, an electric frequency of a base frequency required by a resonance controller and a phase compensation value, calculating a current d-axis and 0-axis control cycle resonance controller output, and injecting a d-axis current by setting the d-axis current reference value; calculating a reference voltage by FOC and performing inverter nonlinear compensation; calculating a reference value of three-phase voltage relative to a neutral point voltage, and further obtaining a driving signal; identifying resistance, inductance and a base wave flux linkage in real time based on an FFRLS algorithm; calculating a term containing third harmonic flux linkage information through a low-pass filter; and finally obtaining the third harmonic flux linkage through the FFRLS algorithm. The parameter identification method has the advantages of low cost, simplicity and the like.

A method compensates for an undesired switching state-specific change in a neutral point voltage of an intermediate circuit when an operating point-specific output voltage is modulated. The method includes determining an operating point-specific switching pattern from at least four voltage vectors, wherein at least two of the voltage vectors are produced by different switching states of a 3-level inverter redundantly but with an opposite influence on a neutral point voltage; predicting, based on the determined switching pattern, a current load of the neutral point connection causing the undesired change in the neutral point voltage; determining, based on the predicted current load, an equalization current compensating for the current load within a modulation period; and determining a temporal weighting of the redundant voltage vectors by which at least a portion of the compensating equalization current is provided when the output voltage is modulated.

This invention discloses an improved method for controlling the midpoint voltage balance of a three-level bidirectional DC-DC converter, comprising the following steps: sampling the upper arm supporting capacitor voltage, the lower arm supporting capacitor voltage, and the inductor current respectively; selecting a switching transistor with an adjusted duty cycle based on the relationship between the upper and lower arm supporting capacitor voltages and the direction of the inductor current to control the balance of the midpoint voltage of the three-level bidirectional DC-DC converter; the inductor current can also be selected from the input current or output current in the DC-DC converter circuit to control the balance of the midpoint voltage of the three-level bidirectional DC-DC converter; by reasonably selecting the switching transistor with an adjusted duty cycle, the problem of midpoint voltage runaway caused by factors such as zero drift in the current detection circuit is avoided.

The application discloses a general reconfigurable simulation system of a power electronic converter, comprising: a dynamic element module, which is used for solving a dynamic element state equation according to a forward Euler method to obtain a dynamic element state variable, and sending the dynamic element state variable to a switch module according to a preset selection instruction; the switch module is used for constructing a general matrix model for a bridge arm switch of the converter, processing the dynamic element state variable through the general matrix model, and generating a switch voltage and a switch state instruction; a neutral point voltage solving module, which is used for constructing a neutral point voltage model for a three-phase rectification or inversion circuit according to the switch voltage and the switch state instruction, and solving to obtain a neutral point voltage; and a power supply module, which is used for providing different power supply voltages for the neutral point voltage solving module, wherein the power supply voltages include three-phase alternating voltages and a direct current voltage. The technical problems that the simulation adjustment flexibility is poor in different scenes, the modeling is complicated due to the increase of system element complexity, and the simulation compilation is time-consuming in the prior art are solved.

The invention discloses a motor phase current sampling device and method, a chip and a motor controller, the device comprises a reference voltage providing unit, a sampling unit and a control unit, the reference voltage providing unit is connected with the reference ground end of the sampling unit, and the control unit is connected with the sampling unit; the reference voltage providing unit is used for outputting partial voltage of neutral point voltage of the motor; the sampling unit is used for sampling a motor phase voltage corresponding to each phase of bridge arm in the multi-phase bridge arm based on voltage division; the control unit is used for controlling the reference voltage providing unit to output the partial voltage of the voltage of the neutral point of the corresponding motor in the target sampling period of each phase of bridge arm in a pulse modulation period, and controlling the sampling unit to sample the corresponding motor phase voltage based on the partial voltage to obtain a plurality of motor phase voltage sampling values. Determining a motor phase current according to the plurality of motor phase voltage sampling values; wherein the target sampling time period is the time period from the dead time corresponding to each phase of bridge arm to the time period before follow current is completed. The phase current sampling cost of the device is low.

The present application relates to a kind of considering the analysis method of transformer neutral point voltage of inverter type distributed light storage capacity, first, obtain the transformer neutral point voltage formula expressed in line parameters and transformer rated phase voltage;Second, obtain the neutral point voltage only with the short-circuit current of distributed power output and load impedance is related;Then, according to the ratio of distributed photovoltaic capacity and load, the short-circuit current of distributed power output is divided into two cases, namely constant output maximum short-circuit current and the short-circuit current that changes with load;Respectively, the neutral point voltage formula is obtained, after setting gap breakdown voltage, the load proportion critical value that can cause neutral point overvoltage can be obtained;Finally, function about inverter type distributed photovoltaic capacity, energy storage proportion and load proportion is established, and the load proportion critical value that can cause neutral point overvoltage under certain energy storage proportion is solved.

The invention discloses a method and a system for measuring ground parameters of a power distribution system with a neutral point grounded through an active arc suppression device, which are applied to the ground parameter measurement of a single-phase injection transformer or an arc suppression coil grounded generator or a power distribution network of which the neutral point is injected into a power supply through a secondary winding. Power frequency signal injection is realized by regulating and controlling the size and / or phase of a power signal output by the power supply and / or regulating and controlling the output impedance of the power supply; measuring neutral point ground voltage before and after the regulation and control power supply, primary ground current of a single-phase injection transformer and ground current of each arc suppression coil; and calculating power distribution system ground parameters according to the measurement data. Power frequency signal injection is realized by directly utilizing the active arc extinguishing device without additional power supply injection equipment, so that the measurement signal is large, and the anti-interference capability is strong; the method does not affect the structure of a power distribution network system, eliminates the influence of the neutral point voltage offset of the system on the measurement precision, is safe and reliable in measurement process, is high in precision, and can be used for ground fault detection, arc extinction and protection.

The invention discloses a ground parameter measurement method and system for a power distribution system with a neutral point grounded through an arc suppression coil, and is applied to ground parameter measurement of a generator or a power distribution network with the neutral point grounded through a damping resistor connected in series through the arc suppression coil, and the method comprises the steps: injecting a power supply signal into the neutral point through a power supply connected in parallel to the two ends of the damping resistor; measuring neutral point voltage signals before and after the injection of the power supply signal and grounding current signals of each arc suppression coil; and calculating the ground parameters of the power distribution system according to the measured data. Signals are injected through the power supplies connected to the two ends of the damping resistor in parallel, gear shifting testing does not need to be carried out on the arc suppression coil, safe and stable operation of a power distribution network is not affected, influences caused by power frequency signals and additional equipment can be eliminated, the precision of ground parameter measurement of a power distribution system is greatly improved, and the method can be used for ground fault detection, arc suppression and protection.

The invention provides a three-level converter neutral-point imbalance seven-segment control method and electronic equipment, and relates to the technical field of power equipment. The three-level converter midpoint imbalance seven-segment control method comprises the following steps: acquiring three-phase power grid voltage and three-phase power grid current, and determining reference voltage vector coordinates according to the three-phase power grid voltage and the three-phase power grid current; determining a small sector where the reference voltage vector coordinates are located; and positive bus capacitor voltage and negative bus capacitor voltage are obtained, the action duration of each target control vector is determined according to the positive bus capacitor voltage, the negative bus capacitor voltage and the small sector where the reference voltage vector coordinates are located, and seven-segment SVPWM control is carried out. According to the method, the redundant small vector is reasonably selected, the neutral point voltage is adjusted through the redundant vector by adopting the seven-section SVPWM, the current ripple is smaller, and the control is simple.

A circulating current suppression method of a power system having a plurality of power modules is provided. Each power module includes a high-voltage bus, a low-voltage bus and a balance circuit having a neutral voltage. The circulating current suppression method includes: in each balance circuit, disposing a first capacitor electrically coupled between the high-voltage bus and the neutral voltage, and disposing a second capacitor electrically coupled between the neutral voltage and the low-voltage bus; acquiring a current effective value of an input of each power module; if detecting that the current effective value of at least one power module doesn't remain at a current reference value, determining that a circulating current occurs in the at least one power module; and operating the balance circuit of the at least one power module to charge the first capacitor or the second capacitor to regulate the neutral voltage for suppressing the circulating current.

This application relates to the field of three-level inverter technology, and provides a three-level inverter circuit and its control method. The circuit includes a first half-bridge circuit, a second half-bridge circuit, a first capacitor, a second capacitor, a three-phase inverter circuit, and a controller. The controller is used to acquire at least one first vector, at least one second vector, a first zero vector, and a second zero vector forming a reference voltage vector. Between adjacent first and second vectors, a first zero vector and a second zero vector are inserted to form a vector sequence in which the first and second vectors are switched via zero vectors. Based on this vector sequence, the on / off state of each device in the first half-bridge circuit, the second half-bridge circuit, and the three-phase inverter circuit is controlled. The three-level inverter circuit provided in this application can reduce losses on switching devices while maintaining neutral point voltage balance.

The application discloses a non-isolated flexible interconnection equipment control method and system, and belongs to the technical field of power system distribution network fault control. The method comprises the following steps: starting fault detection based on zero sequence voltage ratio; distinguishing the fault side and the healthy side through zero sequence instantaneous power; inputting a zero sequence suppression strategy of the healthy side converter to eliminate cross-zone interference; injecting a 300Hz high-frequency signal into the fault side converter to realize parameter-independent fault phase selection; switching a proportional-resonance controller based on the phase selection result to execute an arc extinction strategy, controlling the neutral point voltage to be the negative value of the fault phase voltage, and reducing the fault point voltage to below 0.2kV. The application breaks through the limitation of traditional arc extinction devices relying on the neutral point, solves the zero sequence transmission problem of the non-isolated topology, realizes the full-automatic and rapid disposal of single-phase grounding faults, and has a 100% arc extinction success rate, and is suitable for intelligent distribution network construction.

The application provides a three-level converter neutral point potential control method and system, relates to the technical field of intelligent control, samples positive bus voltage and negative bus voltage, calculates voltage deviation, and generates an additional control quantity according to the voltage deviation and the sign of alternating current, wherein the additional control quantity is obtained through sign function and proportional control processing; the additional control quantity is subjected to amplitude limiting processing to obtain an amplitude-limited additional control quantity; the amplitude-limited additional control quantity is superimposed on a positive modulation wave, and the amplitude-limited additional control quantity is inverted and superimposed on a negative modulation wave to obtain final positive and negative modulation waves; the final positive and negative modulation waves are compared with a carrier wave to generate a driving signal of a power device; and the driving signal is used to control the on-off of the switching device, so that corresponding levels are output to realize neutral point potential balance. The application can simultaneously realize low-frequency fluctuation and DC offset suppression of the neutral point voltage.

A charging system for an electric vehicle and a method for controlling it are disclosed, wherein the charging system comprises a control unit that controls the duty cycles of a plurality of switching elements in an inverter based on a duty cycle command that causes the voltage of a neutral point of the motor to follow a preset neutral point voltage command when a charging current from an external current source is applied to the neutral point, and the duty cycle command is selectively compensated based on an error between the neutral point voltage command and the neutral point voltage.