A method for controlling the speed reduction of a motor

Abstract

The present invention relates to the technical field of air compressor control systems, and particularly to a method for controlling the speed reduction of a motor, including: determining the maximum operating bus voltage V_limit that can be run according to the hardware characteristics of the controller, and taking the maximum operating voltage V_limit as the target bus voltage V_limit of the voltage closed-loop system; using the actually acquired real-time bus voltage as the feedback of the voltage closed-loop system; when a speed reduction instruction is received, the voltage closed-loop system intervenes to work, inputting the target bus voltage V_limit and the real-time bus voltage into the voltage closed-loop system, and the voltage closed-loop system outputs the Q-axis reference current or outputs a speed reduction frequency to control the motor to reduce speed; during the process of the motor reducing speed, the magnitudes of the D-axis current and the Q-axis current are limited by power devices; performing step S3 until the motor reaches the target speed; the present invention enables the motor to reduce speed at the maximum deceleration, shortens the motor speed reduction time, and improves the service life of the air compressor bearing while protecting the safety of the hardware.

Description

Technical Field

[0001] The present invention relates to the technical field of air compressor control systems, and particularly to a method for controlling the speed reduction of a motor. Background Art

[0002] Hydrogen fuel cell vehicles are an important technical route in China's new energy vehicle industry. With the advancement of the national new energy strategy, the disadvantages of traditional batteries are becoming increasingly apparent. Compared with pure electric vehicles, hydrogen fuel cell vehicles have the advantages of high power density, long endurance mileage, and short refueling time. Hydrogen fuel cells will become a substitute for traditional batteries due to their unparalleled superiority.

[0003] In the prior art, an air compressor controller generally controls a motor through a speed outer loop and a current inner loop. This method cannot accurately control the deceleration frequency, and problems such as too fast or too slow deceleration of the air compressor motor may occur. If the motor decelerates too fast, it will be in a reverse power generation state, which may cause the bus voltage to be too high and damage the air compressor controller. If the deceleration is too slow, the response of the air compressor will become slower. Moreover, in the prior art, a super-high-speed air pump is usually used as the air compressor. If the motor decelerates too slowly, it will increase the wear of the air bearing in the super-high-speed air pump and reduce the service life of the super-high-speed air pump. Summary of the Invention

[0004] The object of the present invention is to provide a method for controlling the speed reduction of a motor to solve the problem that in the prior art, the air compressor controller cannot accurately control the deceleration frequency, resulting in too fast or too slow deceleration of the air compressor motor, which in turn causes damage to the air compressor controller and slower response of the air compressor.

[0005] The technical solution of the present invention is: A method for controlling the speed reduction of a motor, which is applied to an air compressor in a hydrogen fuel cell system, includes:

[0006] S1. According to the hardware characteristics of the controller, determine the maximum operating voltage Vlimt that the bus can run, and use the maximum operating voltage Vlimt as the target bus voltage Vlimt of the voltage closed-loop system;

[0007] S2. Use the actually obtained real-time bus voltage as the feedback of the voltage closed-loop system;

[0008] S3. When a deceleration command is received, the voltage closed-loop system intervenes to work. Input the target bus voltage Vlimt and the actual bus voltage into the voltage closed-loop system. The voltage closed-loop system outputs the Q-axis reference current or outputs the deceleration frequency to control the motor to decelerate. During the motor deceleration process, the magnitudes of the D-axis current and the Q-axis current are limited by power devices;

[0009] S4. Execute step S3 until the motor reaches the target speed.

[0010] Preferably, the voltage closed-loop system outputs the Q-axis reference current to control the motor to decelerate, including:

[0011] The voltage closed-loop system outputs the Q-axis current; obtain the D-axis current;

[0012] After limiting the current values of the Q-axis current and the D-axis current, they are used as the reference current of the current loop, which are respectively denoted as the Q-axis reference current and the D-axis reference current;

[0013] Control the motor to decelerate through the current loop.

[0014] Preferably, in the process that the voltage closed-loop system outputs the deceleration frequency to control the motor to decelerate, it includes:

[0015] The voltage closed-loop system outputs the deceleration frequency;

[0016] Take the deceleration frequency as the slope of the speed control and input it into the speed ramp controller to obtain the real-time set speed;

[0017] Obtain the current speed through the position estimator, input the set speed and the current speed into the speed-loop PI system, and the speed-loop PI system outputs the Q-axis current; obtain the D-axis current;

[0018] After limiting the current values of the Q-axis current and the D-axis current, they are used as the reference current of the current loop, which are respectively denoted as the Q-axis reference current and the D-axis reference current;

[0019] Control the motor to decelerate through the current loop.

[0020] Preferably, the current loop includes:

[0021] After performing PI regulation on the Q-axis reference current and the D-axis reference current through a current PI regulator, determine the Q-axis voltage and the D-axis voltage;

[0022] Perform park inverse transformation on the Q-axis voltage and the D-axis voltage to obtain the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system;

[0023] Perform Clarke coordinate inverse transformation on the α-axis voltage and the β-axis voltage to transform the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system into a conventional three-phase coordinate system, and obtain V r 1, V r 2, V r 3;

[0024] The power device is a three-phase inverter; the V r 1, V r 2, V r3 is modulated into a space vector pulse width modulation signal, and the turn-off and turn-on of a three-phase inverter connected to the motor are controlled according to the space vector pulse width modulation signal to control the motor to decelerate;

[0025] The measured two-phase current values I a , I b are subject to Clarke coordinate transformation on the I a , I b to transform the conventional three-phase coordinate system into a stationary two-phase coordinate system, obtaining I α , I β ;

[0026] Park coordinate transformation is performed on the I α , I β to transform the two-phase stationary coordinate system into a two-phase rotating coordinate system, obtaining I d , I q feedback values; the position estimator provides the position parameter θ for the Park transformation calculation.

[0027] Preferably, when V s is greater than U max , where U max is 's maximum value, and V s is the bus voltage utilization rate; then a weak magnetic current is generated by the weak magnetic control module, and the current value of the weak magnetic current is limited and used as the D-axis reference current.

[0028] Preferably, the closed-loop controller used in the voltage closed-loop system is any one of a PID controller, a PR controller, and a Bang-Bang controller.

[0029] The present invention also provides an air compressor controller, and the air compressor controller uses the method of controlling the motor to decelerate as described above to control the motor in the air compressor to decelerate.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] According to the hardware characteristics of the controller, the present invention determines the maximum operating voltage Vlimt that the bus can run, and uses the maximum operating voltage Vlimt as the target bus voltage Vlimt of the voltage closed-loop system; takes the actually acquired actual bus voltage as the feedback of the voltage closed-loop system; when the motor receives a speed reduction command, the voltage closed-loop system intervenes to work, inputs the target bus voltage Vlimt and the actual bus voltage into the voltage closed-loop system, and the voltage closed-loop system outputs the Q-axis reference current or outputs a speed reduction frequency to control the motor to reduce speed; during the process of the motor reducing speed, the magnitudes of the D-axis current and the Q-axis current are limited by power devices until the motor reaches the target speed; through the above method of controlling the motor to reduce speed, the present invention controls the bus voltage value near the limit value, protects the hardware safety, enables the motor to reduce speed at the maximum deceleration, shortens the motor speed reduction time, and improves the service life of the air compressor bearing. Description of the Drawings

[0032] The present invention will be further described below in conjunction with the drawings and embodiments:

[0033] Figure 1 It is a flowchart of a method for controlling the motor to reduce speed according to the present invention;

[0034] Figure 2 It is a control circuit diagram for controlling the motor to reduce speed by outputting the Q-axis reference current through the voltage closed-loop system in the first embodiment;

[0035] Figure 3 It is a control circuit diagram for controlling the motor to reduce speed by outputting the speed reduction frequency through the voltage closed-loop system in the second embodiment. Detailed Embodiments

[0036] The content of the present invention will be further described in detail below in conjunction with specific embodiments:

[0037] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0038] As Figure 1 shown, this embodiment provides a method for controlling the motor to reduce speed, which is applied to the air compressor of a hydrogen fuel cell system, and includes:

[0039] S1. Determine the maximum operating voltage Vlimt that the bus can run according to the hardware characteristics of the controller, and use the maximum operating voltage Vlimt as the target bus voltage Vlimt of the voltage closed-loop system; among them, determine the maximum voltage value that the controller can withstand according to the withstand voltage values of the bus capacitor, drive chip, and power device in the controller, so as to determine the maximum operating voltage Vlimt that the bus can run.

[0040] S2. Use the actually acquired bus voltage in real time as the feedback of the voltage closed-loop system.

[0041] S3. When a speed reduction command is received, the voltage closed-loop system intervenes to work. Input the target bus voltage Vlimt and the actual bus voltage into the voltage closed-loop system. The voltage closed-loop system outputs the Q-axis reference current or outputs the speed reduction frequency to control the motor to decelerate. During the motor deceleration process, limit the magnitudes of the D-axis current and Q-axis current through the power device.

[0042] S4. Execute step S3 until the motor reaches the target speed.

[0043] In this embodiment, by determining the maximum operating voltage Vlimt that the bus can run according to the hardware characteristics of the controller, and using the maximum operating voltage Vlimt as the target bus voltage Vlimt of the voltage closed-loop system; using the actually acquired bus voltage in real time as the feedback of the voltage closed-loop system; when a speed reduction command is received by the motor, the voltage closed-loop system intervenes to work. Input the target bus voltage Vlimt and the actual bus voltage into the voltage closed-loop system. The voltage closed-loop system outputs the Q-axis reference current or outputs the speed reduction frequency to control the motor to decelerate; during the motor deceleration process, limit the magnitudes of the D-axis current and Q-axis current through the power device until the motor reaches the target speed; through the above method of controlling the motor to decelerate in this embodiment, control the bus voltage value near the limit value, protect the hardware safety, enable the motor to decelerate at the maximum deceleration, shorten the motor deceleration time, and improve the life of the air compressor bearing.

[0044] Embodiment 1

[0045] In Figure 1 In a method of controlling the motor to decelerate as shown, the motor can be controlled to decelerate by the voltage closed-loop system outputting the Q-axis reference current. As Figure 2 shown, this method may include the following steps;

[0046] S31a. The voltage closed-loop system outputs the Q-axis current; acquire the D-axis current.

[0047] S32a. After limiting the current values of the Q-axis current and the D-axis current, they are used as the reference current of the current loop, which are respectively denoted as the Q-axis reference current and the D-axis reference current; by limiting the current values of the Q-axis current and the D-axis current, the output current of the air compressor controller is restricted to prevent damage to the power device due to excessive current.

[0048] S33a. Perform the inverse Park transformation on the Q-axis voltage and the D-axis voltage to obtain the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system.

[0049] S34a. Perform the inverse Clarke coordinate transformation on the α-axis voltage and the β-axis voltage to transform the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system into the conventional three-phase coordinate system, and obtain V r 1, V r 2, V r 3;

[0050] S35a. The power device is a three-phase inverter; modulate V r 1, V r 2, V r 3 into a space vector pulse width modulation signal, and control the turn-off and turn-on of the three-phase inverter connected to the motor according to the space vector pulse width modulation signal to control the motor to decelerate.

[0051] S36a. In the current loop, measure the two-phase current values I a , I b of the motor, perform the Clarke coordinate transformation on I a , I b to transform the conventional three-phase coordinate system into a stationary two-phase coordinate system, and obtain I α , I β ;

[0052] S37a. Perform the Park coordinate transformation on I α , I β to transform the two-phase stationary coordinate system into a two-phase rotating coordinate system, and obtain the feedback values of I d , I q ; The position estimator provides the position parameter θ for the Park transformation calculation.

[0053] In the first embodiment, when V s is greater than U max , where U max is the maximum value of , and V s is the bus voltage utilization rate; then the weak magnetic control module is used to generate the weak magnetic current, and after limiting the current value of the weak magnetic current, it is used as the D-axis reference current; specifically, when V s is greater than U maxWhen the rotational speed reaches the critical speed, the output voltage reaches the limit state. Negative current is injected into the direct axis to reduce the magnetic flux for field-weakening control, thereby increasing the operable range of the rotational speed.

[0054] Embodiment 2

[0055] In Figure 1 In a method for controlling the speed reduction of a motor as shown, the speed reduction frequency can be output by a voltage closed-loop system to control the speed reduction of the motor. As Figure 3 shown, the method may include the following steps;

[0056] S31b. The voltage closed-loop system outputs the speed reduction frequency;

[0057] S32b. Use the speed reduction frequency as the slope of the speed control and input it into the speed ramp controller to obtain the real-time set rotational speed;

[0058] S33b. Obtain the current speed through a position estimator, input the set rotational speed and the current speed into the speed loop PI system. The speed loop PI system outputs the Q-axis current; obtain the D-axis current; limit the current values of the Q-axis current and the D-axis current to prevent excessive current output by the air compressor controller from damaging the power devices;

[0059] S34b. After limiting the current values of the Q-axis current and the D-axis current, use them as the current loop reference currents, denoted as the Q-axis reference current and the D-axis reference current respectively;

[0060] S35b. After performing PI regulation on the Q-axis reference current and the D-axis reference current through a current PI regulator, determine the Q-axis voltage and the D-axis voltage;

[0061] S36b. Perform an inverse Park transformation on the Q-axis voltage and the D-axis voltage to obtain the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system;

[0062] S37b. Perform an inverse Clarke transformation on the α-axis voltage and the β-axis voltage to transform the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system into the conventional three-phase coordinate system to obtain V r 1, V r 2, V r 3;

[0063] S38b. The hardware power device is a three-phase inverter; Modulate V r 1, V r 2, V r 3 into a space vector pulse width modulation signal, and control the turn-off and turn-on of the three-phase inverter connected to the motor according to the space vector pulse width modulation signal to control the speed reduction of the motor;

[0064] S39b. Measure the two-phase current values I of the motor a, I b , for I a , I b Perform Clarke coordinate transformation on I, transform the conventional three-phase coordinate system into a stationary two-phase coordinate system, and obtain I α , I β ;

[0065] S310b. Perform Park coordinate transformation on I α , I β transform the two-phase stationary coordinate system into a two-phase rotating coordinate system, and obtain the feedback values of I d , I q ; The position estimator provides the position parameter θ for the Park transformation calculation. In the second embodiment, similarly, when V s is greater than U max , after the rotational speed reaches the transition speed, the field-weakening control module is used to generate a field-weakening current, and the current value of the field-weakening current is limited and used as the D-axis reference current.

[0066] The closed-loop controller adopted by the voltage closed-loop system is any one of a PID controller, a PR controller, and a Bang-Bang controller, which is not limited here.

[0067] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A method for controlling the speed reduction of a motor, which is applied to an air compressor in a hydrogen fuel cell system, characterized in that Including: S1. According to the hardware characteristics of the controller, determine the maximum operable bus voltage Vlimt, and use the maximum working voltage Vlimt as the target bus voltage Vlimt of the voltage closed-loop system; S2. Use the actually acquired real-time bus voltage as the feedback of the voltage closed-loop system; S3. When a speed reduction command is received, the voltage closed-loop system intervenes to work. Input the target bus voltage Vlimt and the actual bus voltage into the voltage closed-loop system. The voltage closed-loop system outputs the Q-axis reference current or outputs a speed reduction frequency to control the motor to decelerate. During the process of the motor decelerating, limit the magnitudes of the D-axis current and the Q-axis current through power devices; S4. Execute step S3 until the motor reaches the target speed; In the process that the voltage closed-loop system outputs a speed reduction frequency to control the motor to decelerate, it includes: The voltage closed-loop system outputs a speed reduction frequency; Use the speed reduction frequency as the slope of speed control and input it into the speed ramp controller to obtain the real-time set speed; Obtain the current speed through a position estimator, input the set speed and the current speed into the speed loop PI system. The speed loop PI system outputs the Q-axis current; Obtain the D-axis current; After limiting the current values of the Q-axis current and the D-axis current, use them as the current loop reference currents, denoted as the Q-axis reference current and the D-axis reference current respectively; Control the motor to decelerate through the current loop.

2. A method for controlling the speed reduction of a motor according to claim 1, characterized in that, In the process that the voltage closed-loop system outputs the Q-axis reference current to control the motor to decelerate, it includes; The voltage closed-loop system outputs the Q-axis current; Obtain the D-axis current; After limiting the current values of the Q-axis current and the D-axis current, use them as the current loop reference currents, denoted as the Q-axis reference current and the D-axis reference current respectively; Control the motor to decelerate through the current loop.

3. A method for controlling the speed reduction of a motor according to claim 2, characterized in that, The current loop includes: After performing PI regulation on the Q-axis reference current and the D-axis reference current through a current PI regulator, determine the Q-axis voltage and the D-axis voltage; Perform park inverse transformation on the Q-axis voltage and the D-axis voltage to obtain the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system; Perform the inverse Clarke transformation on the α-axis voltage and the β-axis voltage to transform the α-axis voltage and the β-axis voltage in the two-phase stationary coordinate system into a conventional three-phase coordinate system, obtaining V r 1, V r 2, V r 3; The power device is a three-phase inverter; modulating the V r 1, V r 2, V r 3 into a space vector pulse width modulation signal, and controlling the turn-off and turn-on of the three-phase inverter connected to the motor according to the space vector pulse width modulation signal to control the motor to decelerate; The measured two-phase current values I of the motor a , I b , for the said I a , I b , perform Clarke coordinate transformation to transform the conventional three-phase coordinate system into a stationary two-phase coordinate system, and obtain I α , I β ; Perform Park coordinate transformation on the said I α , I β , transform the two-phase stationary coordinate system into a two-phase rotating coordinate system, and obtain the feedback values of I d , I q ; the position estimator provides the position parameter θ for Park transformation calculation.

4. A method for controlling the speed reduction of a motor according to claim 3, characterized in that: When V s is greater than U max where U max is the maximum value, and V s is the utilization rate of the bus voltage; then a field-weakening current is generated by the field-weakening control module, and the current value of the field-weakening current is limited and used as the D-axis reference current.

5. A method for controlling the speed reduction of a motor according to claim 4, characterized in that: The closed-loop controller adopted by the voltage closed-loop system is any one of a PID controller, a PR controller, and a Bang-Bang controller.

6. An air compressor controller, characterized in that: The air compressor controller uses the method for controlling the motor to decelerate according to any one of claims 1-5 to control the motor in the air compressor to decelerate.

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