Dual three-phase motor non-regenerative braking method based on motor loss control

Abstract

The invention discloses a dual-three-phase motor non-regenerative braking method based on motor loss control. The method comprises the steps that firstly, the direct-current bus voltage variable quantity of a dual-three-phase motor system in a braking state is calculated; the braking torque output by the dual three-phase motor is further limited so as to limit the regenerative braking power; and finally, stator copper loss of the double-three-phase motor is controlled, braking energy is consumed on a motor stator winding, and non-regenerative braking control over the double-three-phase motor is achieved. According to the method, the braking power of the dual-three-phase motor system is limited, and meanwhile, the harmonic subspace current is controlled to control the loss of the dual-three-phase motor system, so that energy generated during braking operation is consumed in the motor, and the non-regenerative braking effect is achieved under the conditions of normal operation and single-phase open-circuit fault; compared with a braking method in a traditional three-phase motor, a stable and rapid braking process can be realized by adopting the control method disclosed by the invention.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a non-regenerative braking method for a dual three-phase motor based on motor loss control. Background Technology

[0002] Motor drive systems using diode rectifiers without braking devices offer advantages such as low cost and compact structure, making them suitable for low-cost applications or those with strict size requirements for motor drivers. However, this motor drive topology can only achieve single-phase limited operation. When the motor system is in braking mode, the energy generated by braking cannot be fed back into the power grid, causing an increase in bus capacitor voltage and endangering system safety. Therefore, developing non-regenerative braking methods is of great significance for improving the reliability of such motor drive systems.

[0003] In recent years, numerous scholars have conducted extensive research on non-regenerative braking control technology for motor systems. Existing non-regenerative braking methods primarily achieve this by limiting the motor's braking power and increasing losses during braking. Chinese patent application CN223348564U provides an energy-saving braking method for a frequency converter system. This method adds a braking module between the frequency converter and the motor, enabling the frequency converter to have braking capabilities and achieve rapid motor shutdown and deceleration. Chinese patent application CN119315869A provides an energy-saving braking anti-reverse device and method for a permanent magnet motor-driven electric submersible centrifugal pump. This device consumes the reverse electrical energy generated during motor braking and reversal by setting up a braking circuit and a motor status monitoring and protection circuit. However, both of these patented technologies rely on additional braking and monitoring circuits, significantly increasing system costs. Furthermore, most of these studies and patents focus on three-phase motor systems.

[0004] Compared to traditional three-phase motors, the additional control degrees of freedom of dual three-phase motors enable them to maintain operation without additional software or hardware reconfiguration after a single-phase open-circuit fault. Furthermore, the additional control degrees of freedom of dual three-phase motors provide a new approach to non-regenerative braking. By utilizing the low harmonic subspace impedance and the fact that current does not participate in motor torque generation in dual three-phase motors, the performance of non-regenerative braking in multiphase motors can be optimized. Summary of the Invention

[0005] In view of the above, the present invention provides a non-regenerative braking method for a dual three-phase motor based on motor loss control, which can explore the role of the additional control degrees of freedom of the dual three-phase motor in non-regenerative braking.

[0006] A non-regenerative braking method for a dual three-phase motor based on motor loss control includes the following steps: (1) Calculate the change in DC bus voltage of the dual three-phase motor system under braking conditions; (2) Calculate the q-axis reference current of the motor and limit it to limit the output braking torque and regenerative braking power of the motor; (3) Calculate the x-axis reference current and y-axis reference current of the motor; (4) Adjust the motor current according to the reference current to obtain the reference voltage of the motor, and then perform coordinate transformation and pulse width modulation on the reference voltage to generate a corresponding PWM signal to drive the switching devices in the system inverter.

[0007] Further, in step (1), the change in DC bus voltage is calculated using the following expression: Where: ΔV dc V represents the change in DC bus voltage during braking, C represents the DC bus capacitance of the system, and V represents the change in DC bus voltage during braking. dc Let i be the DC bus voltage of the system. d and i q These are the d-axis current and q-axis current of the motor in the dq coordinate space, respectively. d and u q These represent the d-axis voltage and q-axis voltage of the motor in the dq coordinate space, respectively. x and i y These are the x-axis current and y-axis current of the motor in xy coordinate space, respectively. x and u y t represents the x-axis voltage and y-axis voltage of the motor in the xy coordinate space, respectively, and t represents time.

[0008] Furthermore, the specific implementation of step (2) is as follows: First, the voltage controller is used to measure the change in DC bus voltage ΔV. dc Adjust the voltage controller to keep it near 0, using the output of the voltage controller as the limit for the motor's q-axis reference current. Then, the error between the reference speed and the actual motor speed is input to the speed controller for adjustment, thereby utilizing... The q-axis reference current output by the speed controller is limited; both the voltage controller and the speed controller use PI (proportional-integral) controllers.

[0009] Furthermore, in step (3), when the motor is running normally, the calculation expressions for the x-axis reference current and y-axis reference current are as follows: When a single-phase open-circuit fault exists in the system and the fault occurs in one of the three phases a, b, and c, the calculation expressions for the x-axis reference current and y-axis reference current are as follows: When a single-phase open-circuit fault exists in the system and the fault occurs in one of the three phases (uvw), the calculation expressions for the x-axis reference current and y-axis reference current are as follows: Where: i d and i q These represent the d-axis current and q-axis current of the motor in the dq coordinate space, respectively, i α and i β Let be the α-axis current and β-axis current of the motor in the α-β coordinate space, respectively. and These are the x-axis reference current and y-axis reference current of the motor, respectively. max The maximum phase current amplitude that the system can withstand. i is the reference value for DC current. αf and i βf Let α be the α-axis auxiliary current and β-axis auxiliary current of the motor in the α-β coordinate space.

[0010] Furthermore, the maximum phase current amplitude I max The expression is as follows: in: This is the maximum current amplitude that the inverter in the system can withstand. This is the maximum phase current amplitude that the motor stator winding can withstand.

[0011] Furthermore, the α-axis auxiliary current i αf and β-axis auxiliary current i βf The calculation expression is as follows: The value of φ1 is related to the location of the fault. When the fault occurs in phase a or phase w, φ1 is 0; when the fault occurs in phase b or phase u, φ1 is 2π / 3; when the fault occurs in phase c or phase v, φ1 is -2π / 3.

[0012] Furthermore, the DC current reference value The calculation expression is as follows: Furthermore, in step (4), a PI controller is used to control the d-axis current error. and q-axis current error Adjustments are made to obtain the d-axis reference voltage of the motor. and q-axis reference voltage A quasi-proportional resonant regulator is used to adjust the x-axis current error. and y-axis current error The x-axis reference voltage of the motor is obtained through adjustment. and y-axis reference voltage ;in and The d-axis reference current and q-axis reference current of the motor are... , and These are the x-axis reference current and y-axis reference current of the motor, i d and i q These represent the d-axis current and q-axis current of the motor in the dq coordinate space, respectively, i xf and i yf These are the motor's x-axis auxiliary current and y-axis auxiliary current in the xy coordinate space, respectively.

[0013] Furthermore, when a single-phase open-circuit fault exists in the system, the x-axis reference voltage output by the proportional resonant regulator needs to be adjusted. and y-axis reference voltage The processing is performed, and the specific expression is as follows: in: and These are the final x-axis reference voltage and y-axis reference voltage of the motor after processing, respectively. The value of φ2 is related to the location of the fault. When the fault occurs in phase a or w, φ2 is π; when the fault occurs in phase b or u, φ2 is π / 3; when the fault occurs in phase c or v, φ2 is -π / 3.

[0014] Furthermore, when there is no open-circuit fault in the system, i xf =i x i yf =i y When a single-phase open-circuit fault exists in the system, i xf and i yf The calculation expression is as follows: Where: i x and i y These are the x-axis current and y-axis current of the motor in the xy coordinate space, respectively. The value of φ2 is related to the location of the fault. When the fault occurs in phase a or w, φ2 is π; when the fault occurs in phase b or u, φ2 is π / 3; when the fault occurs in phase c or v, φ2 is -π / 3.

[0015] This invention limits the braking power of a dual three-phase motor system while controlling the losses of the system by regulating the harmonic subspace current. This allows the energy generated during braking to be dissipated within the motor, achieving non-regenerative braking under normal operation and single-phase open-circuit fault conditions. Compared to traditional braking methods in three-phase motors, the control method of this invention enables a smooth and rapid braking process. Attached Figure Description

[0016] Figure 1 This is a control block diagram of the non-regenerative braking method for dual three-phase motors of the present invention.

[0017] Figure 2 This is a schematic diagram of the simulation results of non-regenerative braking of the present invention under normal conditions of a dual three-phase motor.

[0018] Figure 3 This is a schematic diagram of the simulation results of non-regenerative braking under the open circuit fault of phase a of a dual three-phase motor according to the present invention. Detailed Implementation

[0019] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example: This embodiment focuses on a dual three-phase permanent magnet synchronous motor with a 30° phase shift at both neutral points. The stator windings of the motor are powered by a two-level voltage source inverter, whose DC side is connected to a three-phase diode rectifier. This implementation method uses field-oriented control to perform non-regenerative braking of the dual three-phase permanent magnet synchronous motor under normal conditions and single-phase open-circuit faults. Figure 1 As shown: First, the six-phase current i of the dual three-phase motor is collected. a i b i c i u i v i w Then, the six-phase current is transformed into α-β subspace current and xy subspace current as i α i β i x i y : Based on the motor rotor position angle θ, the α-β subspace current is transformed into the dq subspace current: A PI controller is used as the speed regulator and the dq subspace current regulator, while a quasi-proportional resonant regulator is used as the xy subspace current regulator. The output of the speed regulator serves as the q-axis current reference, while the d-axis current reference is set to zero; the outputs of the dq and xy subspace current regulators... and Used as a voltage reference.

[0021] The previous control cycle and Using the dq and xy subspace voltages as the basis for this control cycle, and combining them with the dq and xy subspace currents, the stator power is calculated: Measuring DC bus voltage V dc The average current of the DC bus is: Furthermore, based on the capacitance C of the bus capacitor, the change in DC bus voltage can be calculated: To achieve the control effect of non-regenerative braking, it is necessary to control ΔV. dc The value is zero; for dual three-phase permanent magnet synchronous motors, the stator copper loss can be increased by adjusting the xy subspace current while limiting the braking torque, so that the energy generated by braking is consumed on the stator windings of the motor to achieve the effect of non-regenerative braking.

[0022] Specifically, a PI controller is used as a voltage controller to control ΔV. dc Adjustments are made to keep it near zero, using the voltage regulator output as the limit value for the q-axis current to limit the braking torque. To control the stator copper losses of the motor, the phase current of the motor system should be controlled to reach the system limit value in each control cycle during braking operation by controlling the xy subspace current. When calculating the xy subspace current reference, the current limit of the motor system and the operating state need to be considered. The current limit value of the motor system is the smaller of the maximum current amplitude that the stator winding can withstand and the maximum current amplitude that the inverter can withstand, denoted as I. max : In the formula: This is the maximum current amplitude that the inverter can withstand. This is the maximum phase current amplitude that the motor stator winding can withstand.

[0023] During normal operation, it is necessary to ensure that the current amplitude of each phase is the same. Therefore, the current reference of the xy subspace can be calculated from the α-β subspace current during braking. After a single-phase open-circuit fault, the XY subspace current reference needs to be set according to different fault conditions. Specifically: if the fault occurs in one of the three phases (a, b, c), the XY subspace current reference is calculated as follows: If the fault occurs in one of the three phases uvw, the reference calculation method for the xy subspace current is as follows: In the formula: i αf and i βf The auxiliary variable is obtained from the α-β subspace current. This is the DC current reference value for the xy subspace.

[0024] The calculation method is as follows: Auxiliary variable i αf and i βf The calculation method for is: In the formula: the value of φ1 is related to the location of the fault. When the fault occurs in phase a or phase w, φ1 is 0; when the fault occurs in phase b or phase u, φ1 is 2π / 3; when the fault occurs in phase c or phase v, φ1 is -2π / 3.

[0025] Before adjusting the xy subspace current, it is necessary to preprocess the xy subspace current according to the operating conditions of the motor system. Specifically: when the motor system is running normally, there is no need to process the xy subspace current, and at this time, i xf =i x i yf =i y When a single-phase open-circuit fault occurs in the motor system, the auxiliary i in the xy subspace needs to be calculated based on the location of the fault using the following method. xf and i yf : In the formula: the value of φ2 is related to the location of the fault. When the fault occurs in phase a or phase w, φ2 is π; when the fault occurs in phase b or phase u, φ2 is π / 3; when the fault occurs in phase c or phase v, φ2 is -π / 3.

[0026] Use the dq subspace current reference and the dq subspace current i d and i q Adjust the input dq subspace current regulator; set the xy subspace current reference. and With the auxiliary current i in the xy subspace xf and i yf Adjust the xy subspace current using the input xy subspace current regulator. After adjusting the dq subspace current and xy subspace current, set the dq subspace voltage reference... and Transformed into an α-β subspace voltage reference: Taking the normal operation of a dual three-phase motor system and the open-circuit fault of phase a as examples, when the motor system is operating normally, the current input to the xy subspace current regulator is i. x and i y When an open-circuit fault occurs in phase a of the motor system, the auxiliary variable i αf equals i α i βf equals i β i f equals i x i yf equals i y .

[0027] Before modulating the reference voltages of the dq and xy subspaces, the xy subspace reference voltage needs to be preprocessed according to the operating conditions of the motor system. Specifically: when the motor system is operating normally, no processing is performed on the xy subspace reference voltage; when the motor system has a single-phase open-circuit fault, the xy subspace reference voltage needs to be processed before voltage modulation. in: and This serves as the final xy subspace voltage reference after processing. and The xy subspace voltage reference is the output of the xy subspace current regulator.

[0028] α-β subspace voltage reference and and the processed xy subspace voltage reference and Transform into : By using carrier-based pulse width modulation technology, the reference voltage is converted into a switching signal to control the inverter to drive a dual three-phase permanent magnet synchronous motor, thereby achieving non-regenerative braking control.

[0029] Verification example: To verify the effectiveness of this invention, we constructed a simulation model of a dual three-phase permanent magnet synchronous motor system. The parameters of the motor system are shown in Table 1. Table 1 Applications such as Figure 1 The control strategy of this invention, as shown, was simulated and verified under two conditions: normal operation and phase a open circuit fault. The simulation results of non-regenerative braking under normal conditions of a dual three-phase motor are as follows: Figure 2 As shown, and the simulation results of non-regenerative braking under the condition of an open-circuit fault in phase a of a dual three-phase motor are as follows: Figure 3 As shown in the figure. The simulation results show that the method of this invention can achieve the control effect of non-regenerative braking in both normal operation and fault conditions of a dual three-phase motor system.

[0030] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A method for non-regenerative braking of a dual three-phase electric machine based on electric machine loss control, characterized in that, The method comprises the following steps: (1) calculating the DC bus voltage variation of the dual three-phase motor system in the braking state; (2) calculating the q-axis reference current of the motor and limiting the q-axis reference current, so as to limit the braking torque and the regenerative braking power of the motor; (3) calculating the x-axis reference current and the y-axis reference current of the motor; (4) adjusting the motor current according to the reference current to obtain the reference voltage of the motor, and then performing coordinate transformation and pulse width modulation on the reference voltage to generate corresponding PWM signals for driving the switching devices in the system inverter.

2. The method of claim 1, wherein the non-regenerative braking of the dual three-phase motor is controlled based on motor losses. In the step (1), the DC bus voltage variation is calculated by the following expression: where: ΔV dc is the change of the DC bus voltage of the system in braking state, C is the DC bus capacitance value of the system, V dc is the DC bus voltage of the system, i d and i q are the d-axis current and q-axis current of the motor in d-q coordinate space respectively, u d and u q are the d-axis voltage and q-axis voltage of the motor in d-q coordinate space respectively, i x and i y are the x-axis current and y-axis current of the motor in x-y coordinate space respectively, u x and u y are the x-axis voltage and y-axis voltage of the motor in x-y coordinate space respectively, t represents time.

3. The method of claim 1, wherein the non-regenerative braking of the dual three-phase motor is controlled based on motor losses. The specific implementation method of step (2) is as follows: First, the voltage controller is used to measure the change in DC bus voltage ΔV. dc Adjust the voltage controller to keep it near 0, using the output of the voltage controller as the limit for the motor's q-axis reference current. Then, the error between the reference speed and the actual motor speed is input to the speed controller for adjustment, thereby utilizing... The q-axis reference current output by the speed controller is limited; both the voltage controller and the speed controller are PI controllers.

4. The method of claim 1, wherein the non-regenerative braking of the dual three-phase motor is controlled based on motor losses. In the step (3), when the motor is normally operated, the calculation expressions of the x-axis reference current and the y-axis reference current are as follows: When the system has a single-phase open circuit fault and the fault occurs in one phase of the abc three-phase, the calculation expressions of the x-axis reference current and the y-axis reference current are as follows: When the system has a single-phase open circuit fault and the fault occurs in one phase of the uvw three-phase, the calculation expressions of the x-axis reference current and the y-axis reference current are as follows: where: i d and i q are the d-axis and q-axis currents of the motor in d-q coordinate space, respectively, i α and i β are the a-axis and β-axis currents of the motor in a-β coordinate space, respectively, and are the x-axis and y-axis reference currents of the motor, respectively, I max is the maximum phase current amplitude that the system can sustain, is the DC current reference value, i αf and i βf are the a-axis and β-axis auxiliary currents of the motor in a-β coordinate space.

5. The method of claim 4, wherein, The maximum phase current amplitude I max The expression for the maximum phase current amplitude I is as follows: wherein: is the maximum current amplitude that the inverter can withstand in the system, is the maximum phase current amplitude that the motor stator winding can withstand.

6. The method of claim 4, wherein the non-regenerative braking of the dual three-phase motor is controlled based on the motor loss. The α-axis auxiliary current i αf and the β-axis auxiliary current i βf The calculation expression is as follows: Wherein: the value of φ1 is related to the position of the fault, when the fault occurs in the a phase or the w phase, φ1 takes 0; when the fault occurs in the b phase or the u phase, φ1 takes 2π / 3; when the fault occurs in the c phase or the v phase, φ1 takes -2π / 3.

7. The method of claim 4, wherein the non-regenerative braking of the dual three-phase motor is controlled based on the motor loss. The direct current reference value The calculation expression is as follows: 。 8. The method of claim 1, wherein the non-regenerative braking of the dual three-phase motor is controlled based on motor losses. The step (4) adopts PI controller to adjust d-axis current error and q-axis current error to obtain d-axis reference voltage and q-axis reference voltage of the motor; the step (5) adopts PR regulator to adjust x-axis current error and y-axis current error to obtain x-axis reference voltage and y-axis reference voltage of the motor; wherein and are d-axis reference current and q-axis reference current of the motor, and , and are x-axis reference current and y-axis reference current of the motor, respectively, i d and i q are d-axis current and q-axis current of the motor in d-q coordinate space, respectively, i xf and i yf are x-axis auxiliary current and y-axis auxiliary current of the motor in x-y coordinate space, respectively.

9. The method of claim 8, wherein, When a single-phase open-circuit fault occurs in the system, the x-axis reference voltage output by the proportional resonant regulator needs to be checked. and y-axis reference voltage The processing is performed, and the specific expression is as follows: wherein: and are the final x-axis and y-axis reference voltages of the motor after processing, respectively, and the value of φ2 is related to the position where the fault occurs. When the fault occurs in phase a or phase w, φ2 takes π; when the fault occurs in phase b or phase u, φ2 takes π / 3; and when the fault occurs in phase c or phase v, φ2 takes -π / 3.

10. The method of claim 8, wherein the non-regenerative braking of the dual three-phase motor is controlled based on motor losses. When the system does not have open-circuit faults, i xf = i x = i yf = i y ; when the system has single-phase open-circuit faults, the calculation expressions of i xf and i yf are as follows: wherein: i x and i y are the x-axis and y-axis currents of the motor in the x-y coordinate space, respectively, and φ2 takes a value related to the location of the fault, φ2 takes π when the fault occurs in phase a or w; φ2 takes π / 3 when the fault occurs in phase b or u; and φ2 takes -π / 3 when the fault occurs in phase c or v.

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