A brushless doubly-fed ac machine and a method of designing the same

Abstract

The application relates to the field of alternating current motors, and particularly provides a brushless doubly-fed alternating current motor and a design method thereof, which comprises the following steps: configuring the winding proportion of a high-voltage winding and a low-voltage winding in the brushless doubly-fed alternating current motor in advance; connecting the high-voltage winding with a power grid and supplying power to the low-voltage winding through a low-voltage frequency converter; constructing a motor constant-flux model, a motor constant-power factor model and a motor efficiency control model according to the winding proportion; determining a first control strategy of rotor-side current according to the motor constant-flux model; determining the phase of synchronous current on the stator side and the rotor side according to the motor constant-power factor model, and constructing a second control strategy under the constant power factor; loading the first control strategy and the second control strategy into the motor efficiency control model, determining a topology equation under the maximum power efficiency, and determining design parameters according to the topology equation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric machines, in particular to a brushless doubly-fed AC machine and a design method thereof. BACKGROUND

[0002] Currently, brushless doubly-fed machines (BDFM) are a kind of electric machines with special structure and functions, which have received extensive attention in academia and industry in recent years. Brushless doubly-fed machines are valued for their brushless slip rings, reliable operation, adjustable power factor, small capacity of frequency converter, etc. This type of machine is suitable for variable frequency speed regulation and variable speed constant frequency fields.

[0003] In the design of brushless doubly-fed AC machines, brushless doubly-fed machines have a relatively complex structure, including two sets of stator windings with different pole pairs and a set of rotor windings. This structure makes the manufacture and maintenance of the machine relatively difficult. Although the control strategy of brushless doubly-fed machines has made some progress, how to optimize the control strategy for different application scenarios is still a challenge. The existing control strategy may not fully meet the needs of all applications.

[0004] For example: the efficiency of the motor is different under different working conditions, which cannot guarantee high efficiency operation, and there is vibration and noise in the operation process of the motor, and the stability is insufficient. The power factor of the motor cannot be close to 1, which leads to easy harmonic pollution and insufficient efficiency. SUMMARY

[0005] The present application provides a brushless doubly-fed AC machine and a design method thereof to solve the problems in the background art.

[0006] In a first aspect, the present application provides a design method for a brushless doubly-fed AC machine, comprising:

[0007] Pre-configuring the winding ratio of the high-voltage winding and the low-voltage winding in the brushless doubly-fed AC machine;

[0008] Connecting the high-voltage winding to the power grid and supplying power to the low-voltage winding through a low-voltage frequency converter;

[0009] According to the winding ratio, constructing a motor constant flux model, a motor constant power factor model and a motor efficiency control model;

[0010] According to the motor constant flux model, determining a first control strategy for the rotor side current;

[0011] According to the motor constant power factor model, determining the phase of the synchronous current of the stator side and the rotor side, and constructing a second control strategy under constant power factor;

[0012] The first control strategy and the second control strategy are loaded into the motor efficiency control model, a topology equation under maximum power efficiency is determined, and design parameters are determined according to the topology equation.

[0013] In combination with the first aspect, the topology equations include a stator side voltage equation, a rotor side voltage equation, a stator side flux equation, a rotor side flux equation, a torque equation, a power equation, and a voltage-frequency control equation.

[0014] In combination with the first aspect, in the winding ratio, the high-voltage winding accounts for 70%; and the low-voltage winding accounts for 30%.

[0015] In combination with the first aspect, the rotor windings of the brushless doubly-fed AC motor are connected in reverse phase sequence.

[0016] In combination with the first aspect, the motor constant magnetic flux model includes the following construction steps:

[0017] Collect motor parameters of the brushless doubly-fed AC motor based on the winding ratio. The motor parameters include: stator winding high-voltage parameters, stator winding low-voltage control parameters, rotor winding parameters, magnetic flux parameters, motor structure parameters, motor torque parameters, and external load torque range.

[0018] The brushless doubly-fed AC motor is divided into input control parameters and flux conversion parameters;

[0019] Perform electromagnetic transient simulation on the magnetic flux conversion part according to constant magnetic flux to determine the discretization model under different constant magnetic flux conditions;

[0020] According to the discretization model, the parameter set of different motor parameters in the electromagnetic transient simulation process is determined. According to the parameter set and the constant magnetic flux, the alternating transformation relationship between the constant magnetic flux and the motor parameters is constructed, and the motor constant magnetic flux model is generated.

[0021] In combination with the first aspect, the motor constant power factor model is constructed by the following steps:

[0022] Determine the motor power, high-voltage winding input voltage, and low-voltage winding supply voltage of the brushless double-fed AC motor;

[0023] Construct the BDFIM motor equivalent circuit model, which includes high-voltage winding, low-voltage winding, low-voltage inverter, and MC compensation network.

[0024] Import the motor power, high-voltage winding input voltage, and low-voltage winding supply voltage into the motor equivalent circuit model to determine the frequency conversion conditions of the low-voltage inverter;

[0025] According to the frequency conversion conditions, a constant power factor model of the motor based on the power factor is established.

[0026] In combination with the first aspect, the motor efficiency control model includes the following steps of constructing:

[0027] Perform motor efficiency simulation based on the motor constant magnetic flux model and the motor constant power factor model to determine the motor efficiency MAP diagram; wherein the motor efficiency MAP diagram includes: a torque speed diagram and a power efficiency diagram;

[0028] According to the motor efficiency MAP diagram, a motor efficiency evaluation model is built; the motor efficiency evaluation model consists of efficiency expression, output power expression, input power expression, loss expression, copper loss expression, iron loss expression and mechanical loss expression;

[0029] Determine the correlation factors of motor efficiency based on the motor efficiency evaluation model;

[0030] The point correlation factor and the motor constant power factor model are integrated to generate a motor efficiency control model.

[0031] In combination with the first aspect, the first control strategy includes: proportional-integral control of constant magnetic flux, phase-locked loop control of synchronous rotor side current phase, and current amplitude feedforward control of current amplitude adjustment.

[0032] In combination with the first aspect, the second control strategy includes: phase difference closed-loop control, current amplitude closed-loop control, frequency synchronization control and feedforward and feedback synchronization control.

[0033] In a second aspect, the present invention provides a brushless doubly-fed AC motor, applicable to the design method of the brushless doubly-fed AC motor described above, the motor comprising:

[0034] The motor comprises:

[0035] Stator winding, including high-voltage winding and low-voltage winding;

[0036] High-voltage winding, used to connect to the grid power supply; the number of turns of the high-voltage winding accounts for 70% of the total number of turns of the motor winding;

[0037] The low-voltage winding is used to connect the output terminal of the low-voltage inverter, which is connected to the output terminal of the controller. The number of turns of the low-voltage winding accounts for 30% of the total number of turns of the motor winding.

[0038] The rotor winding is used for reverse phase sequence connection with an external frequency converter and is connected to the controller through a low-voltage frequency converter; wherein the rotor winding rotates after the stator winding is energized.

[0039] The controller is loaded with the motor efficiency control model, and the motor efficiency control model conforms to the topology equation under maximum power efficiency.

[0040] The beneficial effects of the present invention are:

[0041] By optimizing the control strategy, this invention enables the motor to maintain high efficiency under varying operating conditions. Constant magnetic flux control helps reduce vibration and noise during motor operation, improving overall stability. A constant power factor model helps reduce harmonic pollution in the power grid and improve power quality.

[0042] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0043] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0045] Figure 1 A flow chart of a method for designing a brushless doubly-fed AC motor according to an embodiment of the present invention;

[0046] Figure 2 This is a wiring diagram of a 72-slot, 2-pole, 3-phase stator winding in an embodiment of the present invention;

[0047] Figure 3 This is a wiring diagram of a 72-slot, 6-pole, 3-phase stator winding in an embodiment of the present invention;

[0048] Figure 4 This is a 72-slot, 2-pole, 3-phase circuit according to the embodiment of the present invention;

[0049] Figure 5 This is the wiring diagram of the 96-slot rotor winding in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0051] like Figure 1 As shown, in the specific implementation process of the present invention, the present invention proposes a design method of a brushless double-fed AC motor, including:

[0052] Pre-configure the winding ratio of high-voltage winding and low-voltage winding in brushless double-fed AC motor;

[0053] Connect the high-voltage winding to the grid and power the low-voltage winding through low-voltage frequency conversion;

[0054] According to the winding ratio, the motor constant magnetic flux model, motor constant power factor model and motor efficiency control model are constructed;

[0055] Determining a first control strategy for rotor-side current according to a constant magnetic flux model of the motor;

[0056] According to the constant power factor model of the motor, the synchronous current phases of the stator side and the rotor side are determined, and a second control strategy under the constant power factor is constructed;

[0057] The first control strategy and the second control strategy are loaded into the motor efficiency control model, a topology equation under maximum power efficiency is determined, and design parameters are determined according to the topology equation.

[0058] The principle of the above technical solution is:

[0059] like Figures 1 to 5 As shown, the present invention pre-configures the ratio of high-voltage and low-voltage windings, then determines the motor's control strategy and design parameters by constructing a constant magnetic flux model, a constant power factor model, and an efficiency control model for the motor, optimizing the motor's performance by controlling the current and phase of the high-voltage and low-voltage windings. The constant magnetic flux model of the present invention ensures that the magnetic flux of the motor remains constant during operation, thereby improving efficiency and stability. The constant power factor model ensures that the motor maintains a stable power factor under different loads, improving the power quality of the power grid and the operating efficiency of the motor.

[0060] In specific implementations, for example, in a wind turbine, the ratio of high-voltage to low-voltage windings is determined. For example, the high-voltage winding may account for 70% of the total motor power, while the low-voltage winding accounts for 30%. The high-voltage winding is directly connected to the grid, while the low-voltage winding is powered by a frequency converter. The frequency converter adjusts the supply frequency according to wind speed changes, thereby controlling the motor speed. Based on the winding ratio, a constant magnetic flux model is constructed for the motor. This model ensures that the motor maintains a constant magnetic flux despite varying wind speeds, thereby improving efficiency and stability. A constant power factor model is constructed for the motor to ensure a stable power factor at varying wind speeds, minimizing the impact on the grid. Combining these two models, an efficiency control model is constructed to determine the motor operating parameters for maximum power efficiency. Based on the constant magnetic flux model, a first control strategy for the rotor current is determined to maintain a constant magnetic flux. Based on the constant power factor model, the phase of the synchronous currents on the stator and rotor sides is determined, and a second control strategy is constructed. The first and second control strategies are integrated into the efficiency control model to determine the topology equation for maximum power efficiency. Based on this equation, motor design parameters such as the number of winding turns and magnet size are determined.

[0061] The beneficial effects of the above technical solution are:

[0062] By optimizing the control strategy, the motor can maintain high efficiency under different operating conditions. Constant magnetic flux control helps reduce vibration and noise during motor operation, improving overall stability. The constant power factor model helps reduce harmonic pollution in the power grid and improve the power quality of the grid.

[0063] In the specific implementation process of the present invention, the topology equations include the stator side voltage equation, the rotor side voltage equation, the stator side flux equation, the rotor side flux equation, the torque equation, the power equation and the voltage-frequency control equation.

[0064] The principle of the above technical solution is:

[0065] During the design process, the present invention constructs multiple equations based on the rotor and stator of the brushless doubly-fed AC motor, establishes a detailed mathematical model of the motor, predicts the performance of the motor under different working conditions, and evaluates the stability and response characteristics of the system.

[0066] In the specific implementation of the present invention, in the winding ratio, the high-voltage winding accounts for 70%; and the low-voltage winding accounts for 30%.

[0067] The principle of the above technical solution is:

[0068] like Figure 2 and Figure 3 As shown, the present invention effectively distributes the motor's input power by varying the ratio of high-voltage and low-voltage windings, enabling the high-voltage side to handle more power and making it suitable for applications requiring higher power output. The larger proportion of high-voltage windings provides greater control range and flexibility, particularly when adjusting motor speed and torque.

[0069] In the specific implementation process of the present invention, Figure 5 As shown, the rotor windings of the brushless double-fed AC motor are connected in reverse phase sequence.

[0070] The principle of the above technical solution is:

[0071] In this invention, reverse phase sequence coupling can reduce harmonic content in the rotor winding to a certain extent, improving the electromagnetic compatibility of the motor. Reverse phase sequence coupling can also make the magnetomotive force in the rotor winding more uniform, reduce torque fluctuations, and improve the smoothness of motor operation. Reverse phase sequence coupling can also make the motor easier to control under certain operating conditions, thereby simplifying the control strategy.

[0072] In the specific implementation of the present invention, the motor constant magnetic flux model includes the following construction steps:

[0073] Collect motor parameters of the brushless doubly-fed AC motor based on the winding ratio. The motor parameters include: stator winding high-voltage parameters, stator winding low-voltage control parameters, rotor winding parameters, magnetic flux parameters, motor structure parameters, motor torque parameters, and external load torque range.

[0074] The brushless doubly-fed AC motor is divided into input control parameters and flux conversion parameters;

[0075] Perform electromagnetic transient simulation on the magnetic flux conversion part according to constant magnetic flux to determine the discretization model under different constant magnetic flux conditions;

[0076] According to the discretization model, the parameter set of different motor parameters in the electromagnetic transient simulation process is determined. According to the parameter set and the constant magnetic flux, the alternating transformation relationship between the constant magnetic flux and the motor parameters is constructed, and the motor constant magnetic flux model is generated.

[0077] The principle of the above technical solution is:

[0078] In the specific implementation of the present invention, first, various parameters of the motor are collected according to the winding ratio, including high-voltage and low-voltage parameters of the stator winding, rotor winding parameters, flux parameters, motor structure parameters, torque parameters and external load torque range.

[0079] In a specific implementation, the collected parameters may be: stator winding high voltage parameters: resistance R1, inductance L1.

[0080] Stator winding low voltage control parameters: resistance R2, inductance L2.

[0081] Rotor winding parameters: resistance Rr, inductance Lr.

[0082] Magnetic flux parameter: magnetic flux Φ.

[0083] Motor structural parameters: such as pole pair number, air gap length, etc.

[0084] Motor torque parameters: such as rated torque Tn.

[0085] External load torque range: Tload_min to Tload_max.

[0086] Then, the motor parameters are divided into two parts: input control parameters and flux conversion parameters. For example: Input control parameters: R2, L2, Tload. Flux conversion parameters: R1, L1, Rr, Lr, Φ.

[0087] The present invention performs electromagnetic transient simulation on the magnetic flux conversion part, assuming that the magnetic flux is constant, to determine the discretization model under different constant magnetic fluxes. The magnetic flux conversion part is simulated using simulation software (such as MATLAB / Simulink), assuming that the magnetic flux Φ is constant. According to the simulation results, the parameter set of different motor parameters in the electromagnetic transient simulation process is determined. The parameter set under different magnetic fluxes is obtained by simulation, such as current I1, I2, Ir, and the corresponding torque T. Finally, based on the relationship between the parameter set and the constant magnetic flux, an alternating constant magnetic flux-motor parameter model is constructed. The relationship between the magnetic flux Φ and the motor parameters (such as current, torque) is alternating, that is, how the performance parameters of the motor change under different magnetic fluxes.

[0088] The beneficial effects of the above technical solution are:

[0089] The present invention improves the accuracy of motor performance prediction through the constant magnetic flux model. The model can optimize the motor control strategy and improve the motor efficiency and stability.

[0090] In the specific implementation process of the present invention, the motor constant power factor model includes the following steps to construct:

[0091] Determine the motor power, high-voltage winding input voltage, and low-voltage winding supply voltage of the brushless double-fed AC motor;

[0092] Construct the BDFIM motor equivalent circuit model; the motor equivalent circuit model includes: high-voltage winding, low-voltage winding, low-voltage inverter and MC compensation network;

[0093] Import the motor power, high-voltage winding input voltage, and low-voltage winding supply voltage into the motor equivalent circuit model to determine the frequency conversion conditions of the low-voltage inverter;

[0094] According to the variable frequency conditions, a constant power factor model of the motor based on the power factor is established.

[0095] The principle of the above technical solution is:

[0096] In the specific implementation process of the present invention, first, the power of the motor, the input voltage of the high-voltage winding and the supply voltage of the low-voltage winding are determined. For example:

[0097] Motor power: P=100kW.

[0098] High voltage winding input voltage: VHV=690V.

[0099] Low voltage winding supply voltage: VLV=380V.

[0100] Next, an equivalent circuit model of the motor is constructed, which includes a high-voltage winding, a low-voltage winding, a low-voltage frequency converter, and a MC (Motor Controller) compensation network. For example, an equivalent circuit model of the BDFIM is constructed using circuit simulation software (such as PSpice), including a high-voltage winding (R1, L1), a low-voltage winding (R2, L2), a low-voltage frequency converter, and a MC compensation network.

[0101] The determined motor power, high-voltage winding input voltage, and low-voltage winding supply voltage are imported into the equivalent circuit model. For example, the motor power P, the high-voltage winding input voltage VHV, and the low-voltage winding supply voltage VLV are set in the equivalent circuit model.

[0102] In the equivalent circuit model, the frequency conversion condition of the low-voltage frequency converter is determined to maintain the power factor at a constant value. For example, through simulation analysis, the frequency conversion condition of the low-voltage frequency converter is determined, for example, when the power factor target is 0.95, the output frequency of the frequency converter should be f1.

[0103] Finally, a motor constant power factor model based on power factor is built according to the frequency conversion condition. According to the frequency conversion condition, the MC compensation network parameters are adjusted to ensure that the power factor of the motor remains at 1 under varying load conditions. For example, by adjusting the size of the compensation capacitor C to change the compensation of reactive power, the constant power factor is maintained.

[0104] The beneficial effects of the above technical solutions are as follows:

[0105] The present application can effectively control the power factor of the motor, maintain it constant, and improve the power quality of the power grid. By optimizing the power factor, the operating efficiency of the motor is improved. The constant power factor improves the stability and reliability of the motor system, and thus adapts to different loads and power grid conditions, maintaining the performance of the motor.

[0106] In the specific implementation process of the present application, the motor efficiency control model includes the following steps:

[0107] According to the motor constant flux model and the motor constant power factor model, motor efficiency simulation is performed to determine the motor efficiency MAP graph; wherein the motor efficiency MAP graph includes a torque speed graph and a power efficiency graph.

[0108] According to the motor efficiency MAP graph, a motor efficiency evaluation model is built; wherein the motor efficiency evaluation model is composed of an efficiency expression, an output power expression, an input power expression, a loss expression, a copper loss expression, an iron loss expression, and a mechanical loss expression.

[0109] According to the motor efficiency evaluation model, the correlation factor of the motor efficiency is determined.

[0110] The point correlation factor and the motor constant power factor model are integrated to generate a motor efficiency control model.

[0111] The principle of the above technical solution is:

[0112] When the present invention is specifically implemented, first, a simulation analysis of the motor efficiency is performed using the motor constant magnetic flux model and the motor constant power factor model. For example, simulation software is used to simulate the efficiency of the motor under different loads and speeds in combination with the motor constant magnetic flux model and the constant power factor model. A motor efficiency MAP diagram is obtained through simulation, which generally includes a torque-speed diagram and a power-efficiency diagram, showing the efficiency distribution of the motor under different working conditions. For example: the simulation results are plotted as an efficiency MAP diagram, in which the torque-speed diagram shows the efficiency distribution under different torques and speeds, and the power-efficiency diagram shows the efficiency at different power outputs. Based on the efficiency MAP diagram, a motor efficiency evaluation model is constructed, which consists of multiple expressions, including efficiency expression, output power expression, input power expression, and loss expression (including copper loss, iron loss, and mechanical loss).

[0113] For example: Efficiency expression: η=P_out / P_in;

[0114] Output power expression: P_out = Tω (T is torque, ω is angular velocity);

[0115] Input power expression: P_in = VHV*IHV+VLV*ILV (VHV and VLV are the high-voltage and low-voltage side voltages, IHX and ILV are the high-voltage and low-voltage side currents);

[0116] Loss expression: P_loss = P_in - P_out;

[0117] Copper loss expression: P_Cu=I 2 R (I is current, R is resistance);

[0118] Iron loss expression: P_Fe = loss due to flux change;

[0119] Mechanical loss expression: P_mech = no-load loss + load-related loss.

[0120] The efficiency evaluation model identifies key factors affecting motor efficiency, known as correlation factors. For example, by analyzing the efficiency evaluation model, factors influencing efficiency, such as current, voltage, and load conditions, can be identified. These correlation factors are then combined with the motor's constant power factor model to generate a motor efficiency control model for optimizing motor operating efficiency. For example, combining the correlation factors with the constant power factor model can be used to develop a control strategy that optimizes motor efficiency by adjusting the output frequency of the low-voltage inverter and the parameters of the MC compensation network.

[0121] In a specific implementation of the present invention, the first control strategy includes: proportional-integral control of constant magnetic flux, phase-locked loop control of synchronous rotor side current phase, and current amplitude feedforward control of current amplitude adjustment.

[0122] The first control strategy includes three aspects: proportional-integral control for constant magnetic flux, phase-locked loop control for synchronous rotor-side current phase, and current amplitude feedforward control for current amplitude adjustment. These three aspects are crucial for better maintaining a constant power factor in brushless doubly-fed AC motors, improving efficiency and reducing energy consumption.

[0123] The first is proportional-integral control with constant magnetic flux. This control strategy is primarily used to maintain a stable motor speed under rated load. Under this strategy, the motor automatically adjusts the magnetic flux linkage based on load changes to maintain a constant speed. This control strategy offers the advantage of fast response, but it can cause excessive rotor current under light loads, shortening the motor's lifespan.

[0124] The second approach is phase-locked loop control, which synchronizes the rotor-side current phase. This control strategy primarily ensures that the motor's current phase and voltage phase are synchronized under rated load. This synchronous control effectively prevents the rotor's current from lagging or leading its voltage during load changes, ensuring motor efficiency. This control strategy has the advantage of reducing inefficient power losses caused by current phase discrepancies, but it requires significant computational resources and control complexity.

[0125] Finally, there's current amplitude feedforward control, which uses current amplitude adjustment. This control strategy primarily compensates for current amplitude fluctuations caused by load variations. By predicting and adjusting the current amplitude in advance, this control strategy effectively eliminates current amplitude fluctuations caused by load variations, ensuring a constant power factor for the motor. This control strategy effectively eliminates current amplitude fluctuations caused by load variations, improving motor efficiency. However, it requires high prediction accuracy and controller robustness.

[0126] In the specific implementation process of the present invention, the second control strategy includes: phase difference closed-loop control, current amplitude closed-loop control, frequency synchronization control and feedforward and feedback synchronization control.

[0127] In the present invention:

[0128] Phase-difference closed-loop control: This control strategy is primarily used to precisely control the phase difference between the motor's stator and rotor currents, achieving high-precision control. This control strategy requires a sophisticated phase measurement and control system that accurately tracks and eliminates any phase error, improving the motor's operating efficiency and accuracy.

[0129] Current Amplitude Closed-Loop Control: This control strategy mainly aims to adjust in real time for slight fluctuations in current amplitude to maintain a constant current amplitude. This control strategy is usually combined with active power factor control (APFC) technology to achieve real-time control of current amplitude through fast response and accurate calculation.

[0130] Frequency Synchronous Control: This control strategy is mainly used to ensure that the motor stator frequency and power frequency are always consistent, preventing electromagnetic force and torque imbalance caused by inconsistency. This control strategy requires real-time monitoring and adjustment of motor speed to ensure stable operation of the motor under various loads and operating conditions.

[0131] Feedforward and Feedback Synchronous Control: This is a comprehensive control strategy that considers the advantages of both feedforward control and feedback control, providing faster response speed and higher accuracy. Feedforward control can improve system stability and robustness, while feedback control can further improve system accuracy and stability.

[0132] The present application also includes a brushless doubly-fed AC motor suitable for the design method of the above brushless doubly-fed AC motor, the motor comprising:

[0133] The motor comprises:

[0134] The stator winding comprises a high-voltage winding and a low-voltage winding.

[0135] The high-voltage winding is used to connect the power grid power supply; wherein the number of turns of the high-voltage winding accounts for 70% of the total number of turns of the motor winding.

[0136] The low-voltage winding is used to connect the output end of the low-voltage frequency converter, and the low-voltage frequency converter is connected to the output end of the controller; wherein the number of turns of the low-voltage winding accounts for 30% of the total number of turns of the motor winding.

[0137] The rotor winding is used to connect the external frequency converter in reverse sequence, and is connected to the controller through the low-voltage frequency converter; wherein the rotor winding rotates after the stator winding is powered.

[0138] The controller loads the motor efficiency control model, and the motor efficiency control model conforms to the topology equation under maximum power efficiency.

[0139] The principle of the above technical solution is:

[0140] The motor of the present application comprises a stator winding, a rotor winding and a controller. The stator winding comprises a high-voltage winding and a low-voltage winding. The high-voltage winding is responsible for connecting the power grid power supply, while the low-voltage winding is responsible for connecting the output end of the low-voltage frequency converter. The rotor winding is used to connect the external frequency converter in reverse sequence, and is connected to the controller through the low-voltage frequency converter. After the stator winding is powered, the rotor winding will rotate.

[0141] In addition, the controller of the motor is responsible for loading the motor efficiency control model. The model is designed according to the topology equation derived under the maximum power efficiency, which can effectively improve the efficiency of the motor and ensure its reliable operation. Through the intelligent management of the controller, the motor can achieve the optimal efficiency under various working conditions, thereby reducing energy consumption, reducing production cost and improving overall economic benefit.

[0142] The brushless doubly-fed AC motor system of the application integrates high efficiency, low cost and intelligence, and can not only meet the needs of various industrial productions, but also play an important role in the fields of new energy vehicles, rail transit and the like with high efficiency and low energy consumption.

[0143] Obviously, those skilled in the art can make various modifications and variations to the application without departing from the spirit and scope of the application. Thus, if these modifications and variations of the application belong to the scope of the claims of the application and their equivalent technologies, the application also intends to include these modifications and variations.

Claims

1. A design method for a brushless double-fed AC motor, characterized in that: include: Pre-configure the winding ratio of high-voltage winding and low-voltage winding in brushless double-fed AC motor; Connect the high-voltage winding to the grid and power the low-voltage winding through low-voltage frequency conversion; According to the winding ratio, the motor constant magnetic flux model, motor constant power factor model and motor efficiency control model are constructed; Determining a first control strategy for the rotor-side current based on a constant magnetic flux model of the motor; wherein the first control strategy includes: proportional-integral control of the constant magnetic flux, phase-locked loop control for synchronizing the rotor-side current phase, and current amplitude feedforward control for current amplitude adjustment; Based on the constant power factor model of the motor, the synchronous current phases on the stator and rotor sides are determined, and a second control strategy under the constant power factor is constructed; wherein the second control strategy includes: phase difference closed-loop control, current amplitude closed-loop control, frequency synchronization control, and feedforward and feedback synchronization control; The first control strategy and the second control strategy are loaded into the motor efficiency control model, a topology equation under maximum power efficiency is determined, and design parameters are determined according to the topology equation.

2. The design method of a brushless double-fed AC motor according to claim 1, characterized in that: The topology equations include a stator side voltage equation, a rotor side voltage equation, a stator side flux equation, a rotor side flux equation, a torque equation, a power equation and a voltage-frequency control equation.

3. The design method of a brushless double-fed AC motor according to claim 1, characterized in that: In the winding ratio, the high-voltage winding accounts for 70%; the low-voltage winding accounts for 30%.

4. The design method of a brushless double-fed AC motor according to claim 1, wherein: The rotor windings of the brushless double-fed AC motor are connected in reverse phase sequence.

5. The design method of a brushless double-fed AC motor according to claim 1, characterized in that: The motor constant magnetic flux model includes the following construction steps: Collect motor parameters of the brushless doubly-fed AC motor based on the winding ratio. The motor parameters include: stator winding high-voltage parameters, stator winding low-voltage control parameters, rotor winding parameters, magnetic flux parameters, motor structure parameters, motor torque parameters, and external load torque range. The brushless doubly-fed AC motor is divided into input control parameters and flux conversion parameters. The input control parameters are the stator winding low-voltage control parameters and the external load torque range, and the flux conversion parameters include the stator winding high-voltage parameters, rotor winding parameters, and flux parameters. Perform electromagnetic transient simulation on the magnetic flux conversion part according to constant magnetic flux to determine the discretization model under different constant magnetic flux conditions; According to the discretization model, the parameter set of different motor parameters in the electromagnetic transient simulation process is determined. According to the parameter set and the constant magnetic flux, the alternating transformation relationship between the constant magnetic flux and the motor parameters is constructed, and the motor constant magnetic flux model is generated.

6. The design method of a brushless double-fed AC motor according to claim 1, characterized in that: The motor constant power factor model is constructed by the following steps: Determine the motor power, high-voltage winding input voltage, and low-voltage winding supply voltage of the brushless double-fed AC motor; Construct the BDFIM motor equivalent circuit model, which includes high-voltage winding, low-voltage winding, low-voltage inverter, and MC compensation network. Import the motor power, high-voltage winding input voltage, and low-voltage winding supply voltage into the motor equivalent circuit model to determine the frequency conversion conditions of the low-voltage inverter; According to the frequency conversion conditions, a constant power factor model of the motor based on the power factor is established.

7. The design method of a brushless double-fed AC motor according to claim 1, characterized in that: The motor efficiency control model is constructed by the following steps: Perform motor efficiency simulation based on the motor constant magnetic flux model and the motor constant power factor model to determine the motor efficiency MAP diagram; wherein the motor efficiency MAP diagram includes: a torque speed diagram and a power efficiency diagram; According to the motor efficiency MAP diagram, a motor efficiency evaluation model is built; the motor efficiency evaluation model consists of efficiency expression, output power expression, input power expression, loss expression, copper loss expression, iron loss expression and mechanical loss expression; Determine the correlation factors of motor efficiency based on the motor efficiency evaluation model; The correlation factor and the motor constant power factor model are integrated to generate a motor efficiency control model.

8. A brushless doubly-fed AC motor, applicable to the design method of a brushless doubly-fed AC motor according to any one of claims 1 to 7, characterized in that: The motor comprises: Stator winding, including high-voltage winding and low-voltage winding; High-voltage winding, used to connect to the grid power supply; the number of turns of the high-voltage winding accounts for 70% of the total number of turns of the motor winding; The low-voltage winding is used to connect the output terminal of the low-voltage inverter, which is connected to the output terminal of the controller. The number of turns of the low-voltage winding accounts for 30% of the total number of turns of the motor winding. The rotor winding is used for reverse phase connection of the external frequency converter and is connected to the controller through low voltage frequency conversion. The rotor winding rotates after the stator winding is energized. The controller is loaded with the motor efficiency control model, and the motor efficiency control model conforms to the topology equation under maximum power efficiency.

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