108 results about "Three phase short circuit" patented technology

The invention relates to the technical field of permanent magnet motors, in particular to a winding connection selection method and device for reducing the short-circuit demagnetization risk of a permanent magnet motor, and the method comprises the steps: when the permanent magnet motor is in a three-phase short-circuit state, taking the relation between the torque loss ratio of star connection and delta connection at different permanent magnet temperatures and different starting rotor positions as the basis; finding a target permanent magnet temperature threshold value; if the permanent magnet temperature is higher than a target permanent magnet temperature threshold value, triangular connection is selected, and otherwise, star connection is selected; when the permanent magnet motor is in a two-phase short-circuit state, a first intersection rotor position and a second intersection rotor position at the current permanent magnet temperature are found on the basis of the relation between the torque loss ratio of star connection and triangular connection at the current permanent magnet temperature and different starting rotor positions, and then the two-phase short-circuit state of the permanent magnet motor is determined according to the intersection rotor positions. And a proper winding connection mode is selected. The operation reliability of the permanent magnet motor can be improved, and it is ensured that the short-circuit demagnetization risk of the permanent magnet motor is effectively reduced.

The invention discloses a new energy transmission line inter-phase fault distance measurement method and system, and the method comprises the steps: starting an element to act after a fault occurs, and inputting low-voltage ride-through control and complex-frequency signal injection control; fault phase selection is realized according to a voltage phase selection element, and fault phase voltages and currents under two characteristic frequencies are extracted through filtering; if the fault is a two-phase short-circuit fault, extracting and replacing the fault phase-to-phase voltage, and replacing the transition resistor with Rf / 2; if the fault is a three-phase short-circuit fault, the phasors of the phase voltage and current difference of any two phases are brought in; according to the equivalent circuit under the characteristic frequency, a frequency domain parameter equation about the fault distance is obtained; respectively splitting a real part and an imaginary part of the frequency domain parameter equation of the fault distance to obtain a real coefficient equation set about the fault distance; when the non-power-frequency electrical quantity is extracted, the real coefficient equation set is expanded into an overdetermined equation with the equation number of 4N, and the solution of the overdetermined equation in the least square meaning is solved; and obtaining a distance measurement result of the new energy transmission line.

The embodiment of the invention provides a rotor and a motor. The rotor comprises a rotor iron core and magnetic steel pieces. The rotor core is provided with a plurality of magnetic steel groove groups along the circumferential direction of the rotor core. And each magnetic steel groove group at least comprises two magnetic steel grooves which are arranged in a V shape with outward openings. The two magnetic steel grooves are symmetrical along the first axis of the rotor. One end of each magnetic steel groove is close to the first axis and the other end is close to the side wall of the rotor core. The magnetic steel pieces are arranged in the magnetic steel grooves. The magnetic steel piece comprises a main body part and magnetic steel end parts arranged at the two ends of the main body part in the width direction, and the thickness of the magnetic steel end parts is larger than that of the main body part. Wherein the width direction of the magnetic steel piece is perpendicular to the axial direction of the rotor. According to the rotor provided by the embodiment of the invention, the thickness of the magnetic steel end part of the magnetic steel piece is greater than that of the middle main body part, so that the demagnetization resistance of the magnetic steel piece at the magnetic steel end part is improved, the magnetic resistance of the magnetic steel piece is reduced, the D-axis inductance is increased, the three-phase short-circuit current is reduced, and the continuous operation capability of a motor under fault working conditions such as three-phase short circuit is improved.

The utility model discloses a three-phase short-circuit ground wire for a mobile power supply, which comprises a clamping device and a ground wire, the clamping device comprises a clamp and a spring, the clamp is divided into a chuck and handles by taking a hinge point as a boundary, and the spring is arranged between the two handles so that the chuck is always kept in a clamping state. The handles are sleeved with elastic insulating layers wrapping the conductor ends and the insulating ends, one end of the grounding wire is connected with a wiring nose in a pressing mode, the other end of the grounding wire is fixed through a thermal shrinkable sleeve, and the wiring nose is connected with the conductor end at the hinge point of any handle through a bolt. The other end of the grounding wire extends towards the insulating end along the handle, penetrates through the elastic insulating layer and then is suspended to form a clamping section; the grounding wire is connected on the basis of an existing clamp, leading-out of a grounding device is achieved, a three-phase wire is clamped on the grounding wire to form a short circuit, if the three-phase wire is electrified in the wiring process, step-by-step power transmission operation is carried out by utilizing the protection characteristic of a superior power supply, and personal injury accidents caused by mistaken power transmission or device damage are avoided.

The invention relates to the technical field of power distribution network protection, and discloses a power distribution network fault scene constant value verification method based on reinforcement learning, and the method comprises the steps: constructing a hierarchical multi-agent verification system; a hierarchical multi-agent verification system is constructed, a high-level agent performs fault situation awareness and decomposes a global constant value verification target, sub-tasks are allocated to a low-level agent for execution, and task allocation and execution are realized through collaborative optimization; after a large number of distributed photovoltaics are connected into the power distribution network, the complexity and uncertainty of a power distribution network fault scene are enhanced, fault types comprise two-phase short circuit, two-phase grounding short circuit and three-phase short circuit, the protection behavior difference under different fault positions is obvious, the fault characteristics are changed, the increasing assisting and drawing-out effects are generated, and the reliability of the power distribution network fault scene is improved. Therefore, over-current protection range changes, protection mismatch, override trip and maloperation are caused, and power failure range is expanded. For a complex fault scene, a layered multi-agent architecture is adopted, and efficient task allocation and execution are realized through high-level coordination and bottom-level negotiation.

The invention relates to the technical field of new energy power systems, in particular to an offshore wind power integration aid decision-making method, system and device considering power grid strength coupling constraints and a medium. Calculating a power grid mutual impedance matrix of the offshore wind power cluster and the three-phase short-circuit capacity of each wind power plant grid-connected point, and generating a power grid strength evaluation index according to a calculation result; sorting the node wind power plants according to the power grid strength, and screening out other wind power plants having a strong coupling relationship with weak nodes based on a sorting result and an interaction influence factor between the weak node wind power plants to form a to-be-optimized wind power plant set; establishing a multi-objective optimization model, taking the power grid strength evaluation index as a constraint condition into the multi-objective optimization model, and executing output scheduling optimization calculation; the method can provide technical support for weak node power grid strength improvement and regulation and control decision after large-scale offshore wind power is connected into the power grid.

The utility model discloses a stator three-phase short circuit device, and belongs to the field of stator three-phase short circuit mechanisms. Three sets of conductive clamps and driving clamping pieces are arranged in the device, and an elastic element is arranged between a fixed conductive clamping arm and a movable clamping arm which are hinged to each other in each conductive clamp. Therefore, the driving clamping piece can drive the conductive clamp to the stator phase end after clamping the fixed conductive clamping arm in the conductive clamp, and enables the cambered surface of the protruding part in the movable clamping arm to be in contact with the stator phase end and to continuously move towards the direction close to the stator phase end. And embedding and clamping of the stator phase end A and the conductive clamp are realized under the action of automatic guiding of the lug boss and elastic deformation of the elastic element. The conducting strip does not need to be manually connected to the stator phase end in related technologies, so that the efficiency of stator three-phase short circuit is improved, and the production efficiency of a stator mass production line integrated with the device is improved.

The application discloses an inverter power three-phase short-circuit fault current analytic method considering a phase-locked loop and a current inner loop transient process, and belongs to the technical field of photovoltaic grid-connected system fault analysis. The application studies the transient process of SRF-PLL under different damping ratios, analyzes the influence of the transient process of SRF-PLL on the coordinate transformation of PCC point voltage and current, finally considers the influence of the transient process of SRF-PLL and the current inner loop on the fault current, introduces a correction coefficient, and decomposes the phase current component expressions of the inverter port fault current into the phase current components of the inverter port current under the first influence condition and the phase current components of the inverter port current under the second influence condition. Through the application, the transient characteristics of the IIDG can be more accurately analyzed, the short-circuit characteristic analysis of the IIDG is perfected, and a reference basis is provided for the fault characteristic analysis of the IIDG.

The present invention provides a method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method, which relates to the technical field of motors. The method includes constructing a finite element model, setting the rotor angular frequency, and calculating the back electromotive force amplitude and synchronous reactance under specific working conditions; performing at least two groups of parameter settings on the model, short-circuiting the three-phase winding circuit, and calculating the three-phase short-circuit current waveform; for the three-phase short-circuit current waveforms under different groups of parameters, selecting a specific phase to calculate the waveform difference; performing a spectral analysis on the waveform difference, and calculating the subtransient reactance parameter under the initial rotor position condition according to the relevant parameters of specific spectral components, the back electromotive force amplitude, and the synchronous reactance; changing the initial rotor position, and taking the average value of the subtransient reactance parameters at multiple positions as the final result. The present invention considers the influence of rotor eddy currents, and based on the finite element method, accurately and efficiently estimates the subtransient reactance through multi-step calculations and parameter adjustments, helping to optimize the power system.

The invention provides a flexible direct-current transmission short-circuit current control strategy multi-objective optimization solving method, which specifically comprises the following steps of: 1, constructing a receiving end fault two-port model, and solving parallel fault transition impedance in a receiving end power grid fault model; step 2, in combination with parallel fault transition impedance, deriving a minimum reactive current reference value constraint required by AC voltage support in a fault period and an active current constraint allowed by DC side energy balance and DC voltage upper limit; and step 3, obtaining the short-circuit current safety domain under the three-phase short-circuit fault by combining the minimum reactive current required for reducing the voltage drop when the short-circuit fault occurs, the active current which can be provided by the receiving-end converter station MMC and the amplitude constraint condition of the short-circuit current output by the receiving-end converter station MMC. According to the invention, adaptive analysis and optimization are carried out on an existing short-circuit current control strategy, and it is ensured that the optimized control strategy not only can reduce unbalanced power accumulation, but also can be used for supporting alternating-current power grid voltage through reserved capacity.

The invention discloses a complex electromagnetic looped network partition optimization planning method based on a Louvain algorithm, and the method comprises the steps: simplifying a receiving-end power grid model into a weighted undirected topological graph, dividing the nodes of the weighted undirected topological graph into a plurality of communities based on the Louvain algorithm, and allocating each node to the community where the adjacent node is located until the modularity of each community is the maximum value. And when the community formed after all the nodes finish moving and the three-phase short-circuit current of each partition meet judgment conditions, outputting partition schemes, performing index evaluation on all the partition schemes, and selecting an optimal partition scheme. According to the method provided by the invention, the operation efficiency and stability of the power grid are improved, and the complexity in planning and operation of the power grid is reduced.

This invention proposes a multi-objective optimization solution method for short-circuit current control strategy in flexible DC transmission, specifically including: Step 1, constructing a two-port model of the receiving-end fault and solving for the parallel fault transition impedance in the receiving-end grid fault model; Step 2, combining the parallel fault transition impedance, deriving the minimum reactive current reference value constraint required to support AC voltage during the fault, and the active current constraint allowed by the DC side energy balance and DC voltage upper limit; Step 3, combining the minimum reactive current required to reduce voltage drop during a short-circuit fault, the active current that the receiving-end converter station MMC can provide, and the short-circuit current amplitude constraint condition output by the receiving-end converter station MMC, obtaining the short-circuit current safety domain under three-phase short-circuit faults. This invention adaptively analyzes and optimizes existing short-circuit current control strategies, ensuring that the optimized control strategy can both reduce unbalanced power accumulation and support AC grid voltage through reserved capacity.

The invention discloses a self-adaptive current quick-break protection method considering a distributed photovoltaic access position, belongs to the field of circuit protection, and solves the problems that a traditional protection method is poor in selectivity and adaptability in a multi-power-supply scene, and the technical scheme comprises the steps: S1, building a three-phase short-circuit fault mathematical model containing a distributed photovoltaic DPV based on a power distribution network topological structure, and building a three-phase short-circuit fault mathematical model; fault occurrence positions are divided into three types of fault scenes according to the DPV access points; s2, for the three types of fault scenes, analyzing the distribution rule of three-phase short-circuit current, and constructing and normalizing a position influence factor Kpos based on the influence of DPV access on the short-circuit current; and S3, based on the position influence factor Kpos, designing a protection criterion containing a position correction item through a setting principle of avoiding the maximum short-circuit current at the tail end of the line in current quick-break protection, and dynamically adjusting an action current setting value of the protection device according to the protection criterion. According to the invention, the protection reliability of the photovoltaic power distribution network is improved.

The invention discloses a power grid data processing method and device for offshore wind power, terminal equipment and a storage medium, and belongs to the field of offshore wind power, and the method comprises the steps: obtaining a topological structure, a thermal power and wind power output curve, line transmission capacity limitation, a target line and a target node of a receiving-end power grid; calculating the static bearing margin of the AC line; performing cascading failure simulation based on the target line to obtain line transmission capacity after the failure, and calculating a cascading failure toughness margin based on the line transmission capacity after the failure; calculating a three-phase short-circuit current for the target node, and calculating a short-circuit capacity adaptation degree based on the three-phase short-circuit current; and carrying out weighted calculation on the static bearing margin, the cascading failure toughness margin and the short-circuit capacity adaptation degree of the alternating-current line to obtain an adaptability evaluation value, and determining the running state of the receiving-end power grid, so that the problem of low safety of an offshore wind power and conventional power generation combined power transmission system in the prior art can be solved.

The invention provides a photovoltaic accessible capacity evaluation method and device considering network construction type energy storage, and relates to the technical field of power system analysis and new energy grid connection. The method comprises the following steps: constructing a power grid model, and constructing a system impedance matrix based on a network topology structure of the power grid model; a Thevenin equivalent model of the network construction type energy storage device is established, after the Thevenin equivalent model is connected to a power grid node, the system impedance matrix is corrected, a corrected equivalent system impedance matrix is obtained, and the power grid node comprises at least one photovoltaic load access node; when a three-phase short-circuit fault occurs in a target node, the short-circuit ratio and the photovoltaic permeability of the target node are calculated based on the corrected equivalent system impedance matrix, and the target node is any node in the power grid nodes; and determining the increased maximum accessible capacity of the target node according to the short-circuit ratio and the photovoltaic permeability of the target node. The transmission efficiency and reliability of the power grid can be improved.

The present invention belongs to the technical field of electric power tools and discloses a special discharge device for power capacitors, which has a short-circuit component, an insulating grip component, a grounding component, and an adjustable universal joint (7). It is characterized in that the short-circuit component is composed of a short-circuit telescopic rod (1), a finger contact part, and a finger contact connection part (3), and the insulating grip component is composed of a telescopic insulating rod (8) and a handheld insulating handle (9); the grounding component is composed of a discharge resistance component (5), a grounding wire, and a grounding terminal clamp. This application solves the requirements stipulated in Article 7.4.2 of the State Grid Safety Regulations: after verifying that the equipment is indeed without voltage, the equipment under repair should be immediately grounded and three-phase short-circuited. And the requirement that the full discharge time of each 10 kV capacitor bank is controlled within 5 minutes. The present invention has the following beneficial effects: the charge in the capacitor is released more thoroughly, the personal safety of power workers is ensured, the operation of related equipment is safer, and the man-hours for capacitor maintenance operations are shortened.

The present application discloses a short-circuit impedance adjustment device and method for an MMC converter transformer. The short-circuit impedance adjustment device includes a short-circuit impedance adjustment circuit electrically connected to the secondary winding of the converter transformer. The short-circuit impedance adjustment circuit is a three-phase short-circuit impedance adjustment sub-circuit, and the short-circuit impedance adjustment sub-circuit includes a first bidirectional IGBT component, a second bidirectional IGBT component, a third bidirectional IGBT component, a first adjustment inductor, and a second adjustment inductor. According to different operating states of the MCC, the conduction states of the three IGBT components are controlled. When the MMC is operating normally, the short-circuit impedance is adjusted to a smaller value, so that the system reduces the consumption of reactive power and at the same time meets the control response requirements. When a short-circuit fault occurs on the DC side of the MMC, it instantaneously switches to the large-impedance mode of operation to limit the rise of the short-circuit current. According to different operating modes, the inductance value input is flexibly switched, improving the stability of the system.

The invention discloses a method for acquiring three-phase short-circuit current of a doubly-fed fan by considering the feed-out current of a grid-side converter GSC, and the method comprises the steps: when a three-phase short circuit occurs in a power grid, under the condition of considering RSC control, power fluctuation exists between RSC and GSC; solving the DC bus voltage fluctuation between the RSC and the GSC according to the power fluctuation of the DC side; obtaining a reference value of the current of the grid-side converter according to the voltage fluctuation of the direct-current bus; and obtaining the feed-out current of the grid-side converter according to the d-axis current reference value and the q-axis current reference value. And adding the stator short-circuit current under the static coordinate system considering RSC control and the feed-out current of the GSC to obtain the double-fed fan three-phase short-circuit current of the DFIG considering the feed-out current of the GSC. According to the method, the transient characteristics of the DFIG can be analyzed more accurately, the short-circuit characteristic analysis of the DFIG is perfected, and a basis reference is provided for the fault characteristic analysis of the DFIG.

A motor control device of the present application controls a motor using a detected value of a rotation angle of the motor, based on a measurement result of a magnetic pole position of a magnetic pole position sensor, the motor being driven by a three-phase alternating current and being provided with the magnetic pole position sensor that measures the magnetic pole position of a rotor, in which the motor control device sets any one of the three-phase alternating current when the motor is in a three-phase short circuit as an object phase, compares a current peak time rotation angle that indicates the detected value of the rotation angle when a current value of the object phase is a peak value with a reference rotation angle that indicates the rotation angle when a prescribed current waveform of the object phase is a peak value, and corrects the detected value of the rotation angle based on a comparison result.

This document provides systems and methods for protecting a motor magnet during a three-phase short circuit. A system includes power electronics configured to energize a three-phase electric motor using a plurality of switches, and control switching logic configured to transition the three-phase electric motor into a three-phase short-circuit state using the plurality of switches, and to switch between the three-phase short-circuit state and a three-phase open-circuit state based on a transient current of the three-phase electric motor using the plurality of switches. In some embodiments, the transition from the three-phase short-circuit state to the three-phase open-circuit state occurs in response to the transient current exceeding a threshold value.In some embodiments, the transition to a three-phase short-circuit state occurs in response to at least one of the multiple switches being damaged.

An object of the present invention is to provide a control device for a synchronous machine that suppresses an overcurrent and a torque fluctuation when a three-phase open mode or a short-circuit mode is switched to a torque mode (PWM mode).To solve the above problem, a control device for a synchronous machine according to the present invention is a control device for a synchronous machine that controls a power converter that supplies power to a synchronous machine, the control device for a synchronous machine comprising: a first magnetic flux command value calculation unit that calculates a first magnetic flux command value from a current command value of the synchronous machine; a magnetic flux estimation unit that estimates a magnetic flux value of the synchronous machine from a current detection value of the synchronous machine; and a second magnetic flux command value calculation unit that uses an integration controller to calculate a second magnetic flux command value so that the first magnetic flux command value and the magnetic flux value agree.When the power converter is switched from three-phase short-circuit to PWM control, the integrator on the d-axis side is initialized to a d-axis magnetic flux value, and the integrator on the q-axis side is initialized to a q-axis magnetic flux value.

The present invention discloses a method, a system and a storage medium for discriminating TV disconnection of factory branch complex overcurrent. The method includes the following steps: 1) When the protection operates normally, the TV disconnection operates normally, and the TV disconnection is judged as "no", and the protection export is not blocked; 2) When the protection operates normally and turns to a three-phase short-circuit fault, the TV disconnection is judged as "no", the protection export is not blocked, and at the same time, the main protection criterion is satisfied, and the protection reliably operates and exports; 3) When the protection operates normally and turns to a TV three-phase disconnection, the TV disconnection is judged as "yes", the TV disconnection blocks the protection export, and the protection reliably does not malfunction. The method of the present invention can effectively solve the deficiencies of the existing solutions that cannot take into account the anti-misoperation of the protection device during the starting overcurrent of the factory branch motor and the reliable operation of the protection device during the three-phase short-circuit fault.

The utility model relates to a three-phase power frequency double-loop electromagnetic induction and short circuit heating device for liquid. The heating device is provided with an iron core, and a three-phase primary winding is wound on a core column of the iron core; and the metal shell is arranged along the three-phase closed magnetic loop to form a double-loop shell structure which surrounds the iron core and the three-phase primary winding and is provided with ten secondary side short-circuit metal rings. During operation, short-circuit large current is induced and generated in the metal rings with the short-circuited secondary sides; each secondary side is conducted through the same metal shell to generate phase-to-phase and three-phase short-circuit heavy current; the short-circuit current directions of the inner and outer secondary sides of each phase are the same, and the magnetic leakage directions of the adjacent secondary sides are opposite to form a strong and stable three-phase power frequency alternating N-S magnetic field, so that the leakage magnetism is greatly reduced, and the temperature rise of the protective shell is greatly reduced; a medium flows through the heating device, and is magnetized by a strong alternating magnetic field without scaling while being heated; the surface load parameter is greatly reduced, and the single-machine design power is effectively expanded.

The invention provides a method and a system for matching the following network capacity of a new energy station considering transient overvoltage, and belongs to the technical field of following network capacity calculation, and the method comprises the following steps: simplifying a following network hybrid station to obtain an equivalent model; based on the obtained equivalent model, calculating to obtain a network following and constructing ratio initial value of each station; solving a phase-locked loop stability condition; when a network construction type converter is configured for any station according to the calculated network construction matching initial value, whether a phase-locked loop can be kept stable or not after the station encounters a three-phase short-circuit fault is judged according to a phase-locked loop stability condition, and the transient overvoltage of the station is calculated if the phase-locked loop is unstable; when the transient overvoltage is lower than a safety threshold value, the initial value of the network construction proportion is kept; and when the requirements are not met, deducing to obtain a network construction type capacity ratio expression meeting the transient overvoltage constraint, and correcting the network construction ratio of the station to obtain the network construction type capacity ratio and the following network type capacity ratio in any station.

Systems and methods for protecting a motor magnet during a three-phase short condition are provided herein. A system includes power electronics configured to provide current to a three-phase electric motor using a plurality of switches, and control circuitry configured to transition the three-phase electric motor to a three-phase short condition using the plurality of switches, and alternate between the three-phase short condition and a three-phase open condition using the plurality of switches based on a transient current of the three-phase electric motor. In some embodiments, transitioning from the three-phase short condition to the three-phase open condition is in response to the transient current exceeding a threshold. In some embodiments, the transition to a three-phase short condition is in response to at least one of the plurality of switches being damaged.

The invention relates to a large-scale wind power plant sending-out line phase selection method based on transient current waveform characteristics, and belongs to the technical field of power system relay protection. Firstly, transient current of a wind power plant side is collected, and whether a fault is a grounding fault is judged according to the magnitude of zero-mode current; if the fault is a ground fault, absolute values of integral value ratios of transient current fault components of all phases and 1 difference values are calculated, judgment is carried out according to a ratio corresponding to the minimum value delta kmin in the absolute values, if the ratio is smaller than the other two ratios, the fault phase is one phase except the two corresponding phases in the ratios, and if the ratio is larger than the other two values, the fault phase is one phase except the two corresponding phases in the ratios. The fault phase is the corresponding two phases in the ratio; if the fault is a two-phase short-circuit fault or a three-phase short-circuit fault, the ratio of the integral value corresponding to the delta kmin is judged, if the ratio is larger than the other two ratios, the fault is the two-phase short-circuit fault, and otherwise, the fault is the three-phase short-circuit fault. According to the method, the required time window is short, and the problem that fault phase selection is inaccurate when a traditional phase selection method is used for recognizing far-end high resistance is solved.

The present invention provides a method and system for determining a short-circuit fault protection strategy for a permanent magnet motor considering load characteristics. The method includes constructing a finite element model of the permanent magnet motor; determining the critical torque of the finite element model considering the potential constant torque load under single-phase short circuit; determining the short-circuit peak current ratio of the finite element model under the potential constant torque load as the first short-circuit peak current ratio; determining the short-circuit peak current ratio of the finite element model under the counteractive constant torque load as the second short-circuit peak current ratio; and determining the short-circuit fault protection strategy of the permanent magnet motor in different load torque and inertia intervals according to the first short-circuit peak current ratio and the second short-circuit peak current ratio. The present invention considers the influence of load characteristics on short-circuit current, obtains the variation characteristics of single-phase short circuit and three-phase short circuit of the permanent magnet motor under different load characteristics, and selects the protection strategy according to the ratio of peak current and short-circuit characteristics, avoiding the situation of misselecting the protection strategy.

This invention discloses a method and apparatus for three-phase short-circuit transient modeling of a permanent magnet synchronous motor. The method includes: acquiring the parameter values ​​of the motor body, the initial values ​​of the synchronous motor during a short circuit, and the constraints; determining the dq-axis current value based on the motor body parameters, the initial values ​​during the short circuit, and the constraints; and establishing a three-phase short-circuit transient model based on the dq-axis current value. This invention establishes motor equations and electromagnetic torque equations based on the motor body parameters, and derives an analytical transient model of active short circuit by determining the initial conditions during a short circuit. This allows for the acquisition of the dq-axis current and torque at any given time, providing a precise data foundation for realizing active short circuits. Furthermore, the analytical model helps the controller set reasonable compensation and achieve precise adjustment.

The invention relates to a liquid three-phase power frequency double-loop electromagnetic induction and short circuit heating device and a heating method. The heating device is provided with an iron core, and a three-phase primary winding is wound on a core column of the iron core; and the metal shell is arranged along the three-phase closed magnetic loop to form a double-loop shell structure which surrounds the iron core and the three-phase primary winding and is provided with ten secondary side short-circuit metal rings. During operation, short-circuit large current is induced and generated in the metal rings with the short-circuited secondary sides; each secondary side is conducted through the same metal shell to generate phase-to-phase and three-phase short-circuit heavy current; the short-circuit current directions of the inner and outer secondary sides of each phase are the same, and the magnetic leakage directions of the adjacent secondary sides are opposite to form a strong and stable three-phase power frequency alternating N-S magnetic field, so that the leakage magnetism is greatly reduced, and the temperature rise of the protective shell is greatly reduced; a medium flows through the heating device, and is magnetized by a strong alternating magnetic field without scaling while being heated; the surface load parameter is greatly reduced, and the single-machine design power is effectively expanded.

The invention provides an auxiliary handcart of a high-voltage switch cabinet, which comprises a handcart body, three moving contacts and three test terminals, and is characterized in that the three moving contacts are mounted at the front end of the handcart body in an insulating manner, and the three moving contacts are used for being in contact with the three static contacts when the handcart body is pushed into the high-voltage switch cabinet; the rear end of the vehicle body is provided with three test terminals in an insulated manner. Pressing wheels are arranged at the bottom of the trolley body and used for opening a lifting curtain for shielding a static contact when the trolley body is pushed into the high-voltage switch cabinet. According to the implementation mode, when insulation is measured, the three moving contacts are connected with the three test terminals through the insulated wires, and after the vehicle body is pushed into the high-voltage switch cabinet, the insulation is measured through the test terminals; during grounding, the three test terminals are detached, the three moving contacts and the grounding device are connected through a three-phase short-circuit grounding wire, and grounding is completed after the vehicle body is pushed into the high-voltage switch cabinet. During electricity testing, the three moving contacts and the three testing terminals are detached, and after the vehicle body is pushed into the high-voltage switch cabinet, electricity testing is completed.