Brushless doubly-fed AC motor and design method thereof

Abstract

The invention relates to the field of AC motors, and particularly provides a brushless doubly-fed AC motor and a design method thereof, and the method comprises the steps: configuring the winding proportion of a high-voltage winding and a low-voltage winding in the brushless doubly-fed AC motor in advance; connecting the high-voltage winding with a power grid, and supplying power to the low-voltage winding through low-voltage frequency conversion; constructing a motor constant magnetic 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 the rotor side current according to the motor constant magnetic flux model; according to a motor constant power factor model, stator side and rotor side synchronous current phases are determined, and a second control strategy under a constant power factor is constructed; and loading the first control strategy and the second control strategy into a motor efficiency control model, determining a topological equation under the maximum power efficiency, and determining design parameters according to the topological equation.

Description

Technical Field

[0001] The present invention relates to the field of motors, and in particular to a brushless double-fed AC motor and a design method thereof. Background Art

[0002] At present, brushless doubly-fed AC motor (BDFM) is a motor with special structure and function, which has attracted wide attention in academia and industry in recent years. Brushless doubly-fed motor is valued for its advantages such as no slip ring brush, reliable operation, adjustable power factor, small inverter capacity, etc. This type of motor is suitable for variable frequency speed regulation and variable speed constant frequency and other fields.

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

[0004] For example, the efficiency of the motor varies under different working conditions, and it cannot continuously guarantee high-efficiency operation. There is vibration and noise during the operation 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 of the invention

[0005] The present invention provides a brushless double-fed AC motor and a design method thereof, which are used to solve the above-mentioned background technology problems.

[0006] In a first aspect, the present invention provides a design method of a brushless double-fed AC motor, comprising:

[0007] Pre-configure the winding ratio of high voltage winding and low voltage winding in brushless double-fed AC motor;

[0008] Connect the high voltage winding to the power grid and power the low voltage winding through low voltage frequency conversion;

[0009] According to the winding ratio, the motor constant magnetic flux model, motor constant power factor model and motor efficiency control model are constructed;

[0010] Determine a first control strategy of the rotor side current according to a constant magnetic flux model of the motor;

[0011] 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;

[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 topological 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 double-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 building steps:

[0017] According to the winding ratio, the motor parameters of the brushless double-fed AC motor are collected; wherein the motor parameters include: stator winding high voltage parameters, stator winding low voltage control parameters, rotor winding parameters, flux parameters, motor structure parameters, motor torque parameters and external load torque range;

[0018] The brushless double-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 fluxes;

[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 comprises the following steps of constructing:

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

[0023] Construct the motor equivalent circuit model of BDFIM; the motor equivalent circuit model includes: high voltage winding, low voltage winding, low voltage inverter and MC compensation network;

[0024] The motor power, the input voltage of the high-voltage winding and the supply voltage of the low-voltage winding are introduced 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 comprises the following steps of constructing:

[0027] According to the motor constant magnetic flux model and the motor constant power factor model, the motor efficiency simulation is performed 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] According to the motor efficiency evaluation model, determine the correlation factor of motor efficiency;

[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 double-fed AC motor, which is applicable to the design method of the brushless double-fed AC motor mentioned above, and the motor comprises:

[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 end of the low-voltage inverter, and the low-voltage inverter 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;

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

[0039] The controller loads the motor efficiency control model, and the motor efficiency control model conforms to the topological equation under maximum power efficiency.

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

[0041] By optimizing the control strategy, the present invention can keep the motor running at high efficiency under different working conditions. Constant magnetic flux control helps to reduce vibration and noise during motor operation and improve overall stability. The constant power factor model helps to reduce harmonic pollution of the power grid and improve the power quality of the power grid.

[0042] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or 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 method flow chart of a design method of a brushless double-fed AC motor in 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 It is 72 slots, 2 poles and 3 phases in 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 in conjunction with 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 power 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] Determine a first control strategy of the 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 Figure 1 to Figure 5 As shown, the present invention is a method of pre-configuring the ratio of high-voltage and low-voltage windings, and then determining the control strategy and design parameters of the motor by constructing a constant magnetic flux model, a constant power factor model and an efficiency control model of the motor, and optimizing the performance of the motor 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 the specific implementation process, such as a wind turbine, the ratio of high-voltage windings to low-voltage windings is configured. For example, the high-voltage winding may account for 70% of the total power of the motor, and the low-voltage winding accounts for 30%. The high-voltage winding is directly connected to the grid, and the low-voltage winding is powered by a frequency converter. The frequency converter can adjust the power supply frequency according to the change of wind speed, thereby controlling the speed of the motor. According to the winding ratio, a constant magnetic flux model of the motor is constructed. This model will ensure that the motor maintains a constant magnetic flux when the wind speed changes, thereby improving efficiency and stability. A constant power factor model of the motor is constructed to ensure that the motor maintains a stable power factor at different wind speeds and reduce the impact on the grid. Combining the above two models, an efficiency control model is constructed to determine the motor operating parameters at maximum power efficiency. According to the constant magnetic flux model, the first control strategy of the rotor side current is determined to keep the magnetic flux constant. According to the constant power factor model, the phase of the synchronous current on the stator side and the rotor side 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 topological equation at maximum power efficiency, and the design parameters of the motor, such as the number of winding turns and magnet size, are determined based on this equation.

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

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

[0063] In the specific implementation process of the present invention, the topological 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.

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

[0065] During the design process of the present invention, multiple equations are constructed based on the rotor and stator of the brushless double-fed AC motor, a detailed mathematical model of the motor is established, the performance of the motor under different working conditions is predicted, and the stability and response characteristics of the system are evaluated.

[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 input power of the motor through different ratios of high-voltage windings and low-voltage windings, so that the high-voltage side can handle more power and is suitable for applications requiring higher power output. The high-voltage winding accounts for a larger proportion, which can provide a greater control range and flexibility to a certain extent, especially in situations where the motor speed and torque need to be adjusted.

[0069] In the specific implementation 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 the present invention, the reverse phase sequence connection can reduce the harmonic content in the rotor winding to a certain extent and improve the electromagnetic compatibility of the motor. Through the reverse phase sequence connection, the magnetomotive force in the rotor winding can be made more uniform, the torque fluctuation can be reduced, and the stability of the motor operation can be improved. The reverse phase sequence connection may make the motor easier to control under certain working conditions, thereby simplifying the control strategy.

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

[0073] According to the winding ratio, the motor parameters of the brushless double-fed AC motor are collected; wherein the motor parameters include: stator winding high voltage parameters, stator winding low voltage control parameters, rotor winding parameters, flux parameters, motor structure parameters, motor torque parameters and external load torque range;

[0074] The brushless double-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 fluxes;

[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 parameters: 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. Use simulation software (such as MATLAB / Simulink) to simulate the magnetic flux conversion part, 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 currents I1, I2, Ir, and the corresponding torque T. Finally, according to 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 can improve 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, input voltage of the high voltage winding and supply voltage of the low voltage winding of the brushless double-fed AC motor;

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

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

[0094] According to the frequency conversion 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 inverter, and an MC (Motor Controller) compensation network. For example, circuit simulation software (such as PSpice) is used to construct an equivalent circuit model of the BDFIM, including a high-voltage winding (R1, L1), a low-voltage winding (R2, L2), a low-voltage inverter, and an 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, high-voltage winding input voltage VHV and low-voltage winding supply voltage VLV are set in the equivalent circuit model.

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

[0103] Finally, according to the variable frequency conditions, a constant power factor model of the motor based on the power factor is built. According to the variable frequency conditions, the MC compensation network parameters are adjusted to ensure that the power factor of the motor remains at 1 under changing load conditions. For example, the compensation of reactive power can be changed by adjusting the size of the compensation capacitor C, thereby maintaining a constant power factor.

[0104] The beneficial effects of the above technical solution are:

[0105] The present invention can effectively control the power factor of the motor to keep 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, thereby adapting to different loads and power grid conditions and maintaining the motor performance.

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

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

[0108] 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;

[0109] According to the motor efficiency evaluation model, determine the correlation factor of motor efficiency;

[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 motor constant magnetic flux model and a motor constant power factor model are used to perform a simulation analysis of the motor efficiency. 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. The motor efficiency MAP diagram is obtained by simulation, and the diagram generally includes a torque-speed diagram and a power-efficiency diagram, which shows the efficiency distribution of the motor under different working conditions. For example: the simulation results are plotted into 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 an efficiency expression, an output power expression, an input power expression, and a 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] Through the efficiency evaluation model, the key factors affecting the motor efficiency, namely the correlation factors, are determined. For example, by analyzing the efficiency evaluation model, the main factors affecting the efficiency, such as current size, voltage level, load conditions, etc., are determined. The correlation factors are combined with the motor constant power factor model to generate a motor efficiency control model for optimizing the motor operating efficiency. For example, a control strategy is developed by combining the correlation factors and the constant power factor model, for example, by adjusting the output frequency of the low-voltage inverter and the parameters of the MC compensation network to optimize the motor efficiency.

[0121] In the specific implementation process 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 of constant magnetic flux, phase-locked loop control of synchronous rotor side current phase, and current amplitude feedforward control of current amplitude adjustment. These three aspects are very important and can help brushless double-fed AC motors better control constant power factor, improve efficiency, and reduce energy consumption.

[0123] The first is the proportional integral control of constant magnetic flux. This control strategy is mainly used to maintain the stable speed of the motor under rated load. Under this strategy, the motor will automatically adjust the magnetic flux according to the load change to keep the motor speed constant. The advantage of this control strategy is fast response speed, but it may cause excessive current in the rotor under light load, affecting the life of the motor.

[0124] The second is the phase-locked loop control of the synchronous rotor side current phase. This control strategy is mainly used to ensure that the current phase and voltage phase of the motor are synchronized under rated load. This synchronous control can effectively avoid the situation where the rotor current lags or leads the voltage when the load changes, ensuring the operating efficiency of the motor. The advantage of this control strategy is that it can reduce the invalid power loss caused by the different current phases, but it requires more computing resources and control complexity.

[0125] Finally, there is the current amplitude feedforward control of current amplitude adjustment. This control strategy is mainly used to compensate for the current amplitude fluctuation caused by load changes. This control strategy can effectively eliminate the current amplitude fluctuation caused by load changes and ensure the constant power factor of the motor by predicting and adjusting the current amplitude in advance. The advantage of this control strategy is that it can effectively eliminate the current amplitude fluctuation caused by load changes and improve the operating efficiency of the motor, but it requires higher 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 mainly used to accurately control the phase difference between the motor stator current and the rotor current, so as to achieve the purpose of high-precision control. This control strategy requires the use of a precise phase measurement and control system, which can accurately track and eliminate any phase error, thereby improving the operating efficiency and accuracy of the motor.

[0129] Current amplitude closed-loop control: This control strategy mainly adjusts the small fluctuations of the current amplitude in real time 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 the current amplitude through fast response and precise calculation.

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

[0131] Feedforward and feedback synchronous control: This is a comprehensive control strategy that takes into account the advantages of both feedforward control and feedback control, and can provide faster response speed and higher accuracy. Feedforward control can improve the stability and robustness of the system, while feedback control can further improve the accuracy and stability of the system.

[0132] The present invention also includes a brushless double-fed AC motor, which is applicable to the design method of the brushless double-fed AC motor mentioned above, and the motor includes:

[0133] The motor comprises:

[0134] Stator winding, including high voltage winding and low voltage winding;

[0135] 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;

[0136] The low-voltage winding is used to connect the output end of the low-voltage inverter, and the low-voltage inverter 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 for reverse phase connection of an external frequency converter and is connected to a controller via a low voltage frequency converter; wherein the rotor winding rotates after the stator winding is energized.

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

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

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

[0141] In addition, the controller of the motor is responsible for loading the motor efficiency control model. The model is designed based on the topological equation obtained 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 costs, and improving overall economic benefits.

[0142] The brushless double-fed AC motor system of the present invention combines high efficiency, low cost and intelligence, and can not only meet the needs of various industrial production, but also play an important role in high-efficiency and low-energy consumption fields such as new energy vehicles and rail transportation.

[0143] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended 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 power 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; Determine a first control strategy of the rotor side current according to a constant magnetic flux model of the motor; 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; 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. A method for designing a brushless double-fed AC motor as claimed in claim 1, characterized in that: The topological 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 as claimed in claim 1, characterized in that: In the winding ratio, the high-voltage winding accounts for 70%; and the low-voltage winding accounts for 30%.

4. The design method of a brushless double-fed AC motor as claimed in claim 1, characterized in that: 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 as claimed in claim 1, characterized in that: The motor constant magnetic flux model includes the following building steps: According to the winding ratio, the motor parameters of the brushless double-fed AC motor are collected; wherein the motor parameters include: stator winding high voltage parameters, stator winding low voltage control parameters, rotor winding parameters, flux parameters, motor structure parameters, motor torque parameters and external load torque range; The brushless double-fed AC motor is divided into input control parameters and flux conversion 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 fluxes; 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. A method for designing a brushless double-fed AC motor as claimed in claim 1, characterized in that: The motor constant power factor model comprises the following steps: Determine the motor power, input voltage of the high voltage winding and supply voltage of the low voltage winding of the brushless double-fed AC motor; Construct the motor equivalent circuit model of BDFIM; the motor equivalent circuit model includes: high voltage winding, low voltage winding, low voltage inverter and MC compensation network; The motor power, the input voltage of the high-voltage winding and the supply voltage of the low-voltage winding are introduced 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. A method for designing a brushless double-fed AC motor as claimed in claim 1, characterized in that: The motor efficiency control model comprises the following steps: According to the motor constant magnetic flux model and the motor constant power factor model, the motor efficiency simulation is performed 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; According to the motor efficiency evaluation model, determine the correlation factor of motor efficiency; The point correlation factor and the motor constant power factor model are integrated to generate a motor efficiency control model.

8. The design method of a brushless double-fed AC motor as claimed in claim 1, characterized in that: 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.

9. The design method of a brushless double-fed AC motor according to claim 1, characterized in that: The second control strategy includes: phase difference closed-loop control, current amplitude closed-loop control, frequency synchronization control and feedforward and feedback synchronization control.

10. A brushless double-fed AC motor, applicable to the design method of a brushless double-fed AC motor as claimed in any one of claims 1 to 9, 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 end of the low-voltage inverter, and the low-voltage inverter 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; The rotor winding is used for reverse phase connection of an external frequency converter and is connected to a controller via a low voltage frequency converter; wherein the rotor winding rotates after the stator winding is energized. The controller loads the motor efficiency control model, and the motor efficiency control model conforms to the topological equation under maximum power efficiency.

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