Magnetic bearing system and control method, device, storage medium and program product thereof

Abstract

The present invention discloses a magnetic bearing system and its control method, device, storage medium, and computer program product. The method includes: after the rotor is suspended, when the current of the stator coil is at a set value, combining the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the power amplifier's drive PWM signal, and the corresponding relationship between the duty cycle value of the power amplifier's drive PWM signal under a three-level modulation mode and the temperature of the stator coil, and determining the current temperature of the stator coil based on the current duty cycle value of the power amplifier's drive PWM signal, thereby detecting the current temperature of the stator coil. This solution, by obtaining the duty cycle value of the power amplifier's drive PWM signal when the current of the stator coil is at the set value, and then detecting the stator coil temperature based on the relationship between the duty cycle value of the three-level power amplifier's drive PWM signal and the temperature of the stator coil, is simple and low-cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic bearing systems, and specifically relates to a control method, device, magnetic bearing system, storage medium and computer program product of a magnetic bearing system, and more particularly to a method, device, magnetic bearing system, storage medium and computer program product for detecting the temperature of a stator coil of a magnetic bearing without setting a sensor. Background Art

[0002] Magnetic bearings (i.e., electromagnetic bearings) are a new type of contactless support bearing that uses electromagnets to generate controllable electromagnetic forces to suspend rotors. They have the advantages of being frictionless, wear-free, requiring no lubrication, having adjustable stiffness, and having a long life. Therefore, they are widely used in aerospace, vacuum, ultra-clean, nuclear energy, and other scenarios. The magnetic bearing uses a power amplifier to supply power to the stator coil wound with enameled wire. However, due to the internal resistance of the stator coil, the stator coil will generate heat and increase the temperature, thereby increasing the internal resistance of the stator coil. The temperature rise of the stator coil will cause the insulation performance of the enameled wire to decrease, and there is a risk of short circuit in the stator coil, which seriously affects the normal operation of the magnetic bearing. Therefore, the temperature of the stator coil needs to be detected and controlled. However, when detecting the temperature of the stator coil of the magnetic bearing in the related scheme, a special temperature detection device needs to be set up, which is not only complex in structure but also costly.

[0003] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art. Summary of the Invention

[0004] The object of the present invention is to provide a control method, device, magnetic bearing system, storage medium and computer program product for a magnetic bearing system, so as to solve the problem in related schemes that when detecting the temperature of the stator coil of the magnetic bearing, a special temperature detection device needs to be set up, which is complex in structure and high in cost. The invention achieves the effect of detecting the temperature of the stator coil by the correspondence between the duty cycle value of the driving PWM signal of the three-level power amplifier and the temperature of the stator coil under the condition that the current of the stator coil is constant, so that the detection method is simple and low in cost.

[0005] The present invention provides a control method for a magnetic bearing system, wherein the magnetic bearing system comprises a rotor, a stator coil and a control system, wherein a power amplifier in the control system adopts a three-level modulation mode; the control method for the magnetic bearing system comprises: when the current of the stator coil is a set value, pre-determining the corresponding relationship between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil; when the current of the stator coil is a set value, pre-acquiring the initial temperature of the stator coil, the initial resistance value of the stator coil, and the duty cycle value of the driving PWM signal of the power amplifier; maximum duty cycle value; after the rotor is suspended, when the current of the stator coil is a set value, obtaining the current duty cycle value of the driving PWM signal of the power amplifier; combining the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the driving PWM signal of the power amplifier, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil under a three-level modulation mode, determining the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier, so as to realize the detection of the current temperature of the stator coil.

[0006] In some embodiments, the power amplifier includes a power switch device and a diode. The predetermined correspondence between the duty cycle of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil includes the following formula:

[0007]

[0008] Wherein, q is the duty cycle of the driving PWM signal of the power amplifier, i is the current of the stator coil, T R is the temperature of the stator coil, T0 is the initial temperature of the stator coil, R0 is the initial resistance value of the stator coil, α T0 is the temperature coefficient of the stator coil, U dc is the bus voltage of the power amplifier, U on is the on-state voltage drop of the power switch device in the power amplifier, U D is the conduction voltage drop of the diode in the power amplifier, and K1, K2, K3, K4, and K5 are all calculation coefficients.

[0009] In some embodiments, the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier are obtained in advance, including: obtaining the initial temperature of the stator coil; and using the resistance value of the stator coil obtained at the initial temperature of the stator coil as the initial resistance value of the stator coil; obtaining the maximum temperature of the stator coil; and using the duty cycle value of the driving PWM signal of the power amplifier obtained at the maximum temperature of the stator coil as the maximum duty cycle value of the driving PWM signal of the power amplifier.

[0010] In some embodiments, determining the current temperature of the stator coil according to a current duty cycle value of the drive PWM signal of the power amplifier in combination with the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the drive PWM signal of the power amplifier, and the correspondence between the duty cycle value of the drive PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil includes: determining whether the current duty cycle value of the drive PWM signal of the power amplifier is less than the maximum duty cycle value of the drive PWM signal of the power amplifier; if it is determined that the current duty cycle value of the drive PWM signal of the power amplifier is less than the maximum duty cycle value of the drive PWM signal of the power amplifier, calculating the current temperature of the stator coil according to the current duty cycle value of the drive PWM signal of the power amplifier based on the initial temperature of the stator coil, the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the drive PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil, and displaying the current temperature of the stator coil.

[0011] In some embodiments, based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under a three-level modulation mode and the temperature of the stator coil, the current temperature of the stator coil is calculated according to the current duty cycle value of the driving PWM signal of the power amplifier. The method includes: based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under a three-level modulation mode and the temperature of the stator coil, taking the stator coil temperature corresponding to the duty cycle value of the driving PWM signal of the power amplifier that is the same as the current duty cycle value of the driving PWM signal of the power amplifier in the correspondence as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier.

[0012] In some embodiments, it also includes: determining whether the current duty cycle value of the driving PWM signal of the power amplifier is less than the maximum duty cycle value of the driving PWM signal of the power amplifier; if it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is greater than or equal to the maximum duty cycle value of the driving PWM signal of the power amplifier, sending a signal for over-temperature protection of the current temperature of the stator coil to control the rotor to stop floating.

[0013] Matching the above method, the present invention provides a control device for a magnetic bearing system on the other hand. The magnetic bearing system has a rotor, a stator coil and a control system, and the power amplifier in the control system adopts a three-level modulation method; the control device for the magnetic bearing system includes: a control unit, configured to pre-determine the corresponding relationship between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation method and the temperature of the stator coil when the current of the stator coil is a set value; an acquisition unit, configured to pre-acquire the initial temperature of the stator coil, the initial resistance value of the stator coil, and the driving PW of the power amplifier when the current of the stator coil is a set value. The maximum duty cycle value of the M signal; the acquisition unit is further configured to, after the rotor is suspended, obtain the current duty cycle value of the driving PWM signal of the power amplifier when the current of the stator coil is a set value; the control unit is further configured to combine the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the driving PWM signal of the power amplifier, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil under the three-level modulation mode, and determine the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier, so as to realize the detection of the current temperature of the stator coil.

[0014] In some embodiments, the power amplifier includes a power switch device and a diode; wherein the control unit predetermines a correspondence between a duty cycle value of a driving PWM signal of the power amplifier under a three-level modulation mode and a temperature of the stator coil, including the following formula:

[0015]

[0016] Wherein, q is the duty cycle of the driving PWM signal of the power amplifier, i is the current of the stator coil, T R is the temperature of the stator coil, T0 is the initial temperature of the stator coil, R0 is the initial resistance value of the stator coil, α T0 is the temperature coefficient of the stator coil, U dcis the bus voltage of the power amplifier, U on is the on-state voltage drop of the power switch device in the power amplifier, U D is the conduction voltage drop of the diode in the power amplifier, and K1, K2, K3, K4, and K5 are all calculation coefficients.

[0017] In some embodiments, the acquisition unit pre-acquires the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier, including: acquiring the initial temperature of the stator coil; and using the resistance value of the stator coil acquired at the initial temperature of the stator coil as the initial resistance value of the stator coil; acquiring the maximum temperature of the stator coil; and using the duty cycle value of the driving PWM signal of the power amplifier acquired at the maximum temperature of the stator coil as the maximum duty cycle value of the driving PWM signal of the power amplifier.

[0018] In some embodiments, the control unit determines the current temperature of the stator coil according to a current duty cycle value of the drive PWM signal of the power amplifier based on the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the drive PWM signal of the power amplifier, and the correspondence between the duty cycle value of the drive PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil. The control unit includes: determining whether the current duty cycle value of the drive PWM signal of the power amplifier is less than the maximum duty cycle value of the drive PWM signal of the power amplifier; if it is determined that the current duty cycle value of the drive PWM signal of the power amplifier is less than the maximum duty cycle value of the drive PWM signal of the power amplifier, calculating the current temperature of the stator coil according to the current duty cycle value of the drive PWM signal of the power amplifier based on the initial temperature of the stator coil, the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the drive PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil, and displaying the current temperature of the stator coil.

[0019] In some embodiments, the control unit calculates the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, including: based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, taking the stator coil temperature corresponding to the duty cycle value of the driving PWM signal of the power amplifier that is the same as the current duty cycle value of the driving PWM signal of the power amplifier in the correspondence as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier.

[0020] In some embodiments, it also includes: the control unit is further configured to determine whether the current duty cycle value of the driving PWM signal of the power amplifier is less than the maximum duty cycle value of the driving PWM signal of the power amplifier; the control unit is further configured to send a signal of over-temperature protection of the current temperature of the stator coil to control the rotor to stop floating if it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is greater than or equal to the maximum duty cycle value of the driving PWM signal of the power amplifier.

[0021] In accordance with the above-mentioned device, the present invention further provides a magnetic bearing system, comprising: the control device of the magnetic bearing system described above.

[0022] In conjunction with the above-mentioned magnetic bearing system, the present invention further provides a computer program product, comprising a computer program, which implements the steps of the above-mentioned method for controlling the magnetic bearing system when executed by a processor.

[0023] In accordance with the above method, the present invention further provides a storage medium comprising a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the steps of the above-mentioned method for controlling the magnetic bearing system.

[0024] Therefore, the solution of the present invention predetermines, for the stator coil of the magnetic bearing in the magnetic bearing system and the power amplifier using a three-level modulation method, the stator coil resistance value when the stator coil current is constant and the stator coil temperature is the initial temperature as the initial resistance value, and the duty cycle value of the power amplifier driving PWM signal when the stator coil temperature is the maximum temperature as the maximum duty cycle value. The initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the power amplifier obtained when the stator coil current is constant are used as reference values. The duty cycle value of the power amplifier driving PWM signal determined when the stator coil current is constant after the rotor of the magnetic bearing in the magnetic bearing system is suspended is used as the current duty cycle value. The current temperature of the stator coil is determined by using the corresponding relationship between the duty cycle value of the driving PWM signal of the three-level power amplifier and the temperature of the stator coil. Thus, by detecting the temperature of the stator coil based on the corresponding relationship between the duty cycle value of the driving PWM signal of the three-level power amplifier and the temperature of the stator coil when the stator coil current is constant, the detection method is simple and low-cost.

[0025] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is a flow chart of an embodiment of a method for controlling a magnetic bearing system according to the present invention;

[0028] Figure 2 1 is a flow chart of an embodiment of the method of the present invention for calculating and displaying the current temperature of the stator coil;

[0029] Figure 3 1. A flow chart of an embodiment of the method of the present invention for performing over-temperature protection on the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier;

[0030] Figure 4 Schematic diagram of the structure of an embodiment of a control device for a magnetic bearing system of the present invention;

[0031] Figure 5 It is a control flow diagram of the magnetic bearing control system;

[0032] Figure 6 It is a schematic diagram of the structure of the H-bridge topology of the power amplifier;

[0033] Figure 7 Schematic diagram of current waveform of a three-level power amplifier (i.e., a power amplifier using a three-level modulation mode);

[0034] Figure 8 The figure is a flow chart of the temperature detection and over-temperature protection procedure of the stator coil of the magnetic bearing.

[0035] In conjunction with the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0036] 102 - acquisition unit; 104 - control unit. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Considering that in the relevant scheme, when detecting the temperature of the stator coil of the magnetic bearing, a special temperature detection device needs to be set up, for example: measuring the voltage at both ends of the stator coil by a voltage sensor and measuring the current at both ends of the stator coil by a current sensor, calculating the change in the internal resistance of the stator coil to obtain the temperature of the stator coil; or adding a temperature sensor to directly measure the temperature of the stator coil. Whether setting up voltage and current sensors or setting up temperature sensors, there are problems of complex structure and high cost.

[0039] Furthermore, when monitoring and controlling the temperature of the magnetic bearing's stator coil, the internal resistance increases as the stator coil's temperature rises. Therefore, to maintain a constant current in the stator coil at a certain value, the voltage across the stator coil must be increased to offset the change in internal resistance. In a magnetic bearing control system, the voltage across the stator coil is controlled by adjusting the duty cycle of the power amplifier's PWM signal.

[0040] Therefore, the solution of the present invention provides a control method for a magnetic bearing system, specifically a method for detecting the temperature of the stator coil of the magnetic bearing without setting a sensor. By monitoring the current of the stator coil of the magnetic bearing to be a certain constant value, the duty cycle of the driving PWM signal of the power amplifier is detected to achieve real-time detection of the temperature of the stator coil, and there is no need to additionally design a complex and accurate temperature detection circuit. For example, there is no need for a voltage sensor to measure the voltage across the stator coil. Only contactless and sensorless detection of the temperature of the stator coil can be achieved through application software programming based on the original hardware, which greatly simplifies the temperature detection method of the stator coil of the magnetic bearing.

[0041] According to an embodiment of the present invention, a control method for a magnetic bearing system is provided, such as Figure 1 The flowchart of an embodiment of the method of the present invention is shown in FIG. The magnetic bearing system comprises a rotor, a stator coil and a control system, wherein the power amplifier in the control system adopts a three-level modulation method. Figure 5 Figure 1 is a control flow diagram of the magnetic bearing control system. Figure 5 As shown in the figure, the control process of the power amplifier of the magnetic bearing includes: using a current sensor to detect the current i of the stator coil and output a voltage u; the controller MCU obtains the driving PWM duty cycle value of the power amplifier based on the voltage u and applies a three-level modulation method; at the same time, it outputs the value to the power amplifier bridge circuit through an isolation circuit, and controls the power amplifier to output the current i to the stator coil. Figure 5 In the example shown, when the temperature of the stator coil of the magnetic bearing increases, the internal resistance of the stator coil increases. If the current i of the stator coil needs to be kept constant at a certain value, the voltage across the stator coil needs to be increased to offset the change in the internal resistance of the stator coil. In the magnetic bearing control system, the voltage u across the stator coil is achieved by adjusting the duty cycle of the power amplifier's drive PWM signal. Specifically, the voltage u across the stator coil is increased by increasing the duty cycle of the power amplifier's drive PWM signal to offset the change in the stator coil's resistance. Based on this, the present invention proposes a solution for sensorless detection of the stator coil temperature by monitoring the current of the stator coil of the magnetic bearing at a certain constant value, detecting the duty cycle of the power amplifier's drive PWM signal, and applying the corresponding mathematical relationship.

[0042] In the solution of the present invention, Figure 1 As shown, the control method of the magnetic bearing system includes: steps S110 to S140.

[0043] In step S110 , when the current of the stator coil is a set value, a corresponding relationship between a duty cycle of a driving PWM signal of the power amplifier and a temperature of the stator coil in a three-level modulation mode is predetermined.

[0044] In some embodiments, the power amplifier includes a power switch device and a diode. Figure 6 This is a schematic diagram of the H-bridge topology of the power amplifier. Figure 6 As shown, the power amplifier H bridge includes: MOS tube S1, MOS tube S2, diode D1 and diode D2. Bus voltage V dcThe output of the supply voltage is connected to the drain of MOS transistor S1. The source of MOS transistor S1 is connected to the anode of diode D1 after passing through the stator coil. The output of the supply voltage is also connected to the cathode of diode D1. The source of MOS transistor S1 is connected to the cathode of diode D2, and the ground of diode D2 is GND. The anode of diode D1 is connected to the drain of MOS transistor S2, and the source of MOS transistor S2 is grounded. The stator coil has an equivalent inductance and an equivalent resistance, which is equivalent to an equivalent inductance and an equivalent resistance connected in series. The gates of MOS transistors S1 and S2 are both control terminals, used to input the duty cycle value of the driving PWM signal. Figure 7 Schematic diagram of the current waveform of a three-level power amplifier (i.e., a power amplifier with three-level modulation). Figure 7 Middle,U gs1 is the driving voltage of MOS tube S1, U gs2 is the driving voltage of MOS transistor S2. To reduce current ripple, the power amplifier uses a three-level modulation scheme. The stator coil current now has three states: charging, freewheeling, and discharging. When both MOS transistors S1 and S2 are turned on, the stator coil current increases. When either power switch is turned on and the other is turned off, the stator coil current freewheels.

[0045] In step S110, when the current of the stator coil is a set value, the correspondence between the duty cycle of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil is predetermined, including the following formula:

[0046]

[0047] Wherein, q is the duty cycle of the driving PWM signal of the power amplifier, i is the current of the stator coil, T R is the temperature of the stator coil, T0 is the initial temperature of the stator coil, R0 is the initial resistance value of the stator coil, α T0 is the temperature coefficient of the stator coil, U dc is the bus voltage of the power amplifier, U on is the on-state voltage drop of the power switch device in the power amplifier, U D is the conduction voltage drop of the diode in the power amplifier, K1, K2, K3, K4, and K5 are all calculation coefficients. Preferably, K1 is 0.5, K2 is 2, K3 is 2, K4 is 2, and K5 is 2.

[0048] Specifically, by Figure 6 and Figure 7It can be obtained that when the power amplifier adopts three-level modulation, the expression of the stator coil current i is:

[0049]

[0050] Where L is the inductance of the stator coil, U is the equivalent inductance of the stator coil, dc is the bus voltage, U on is the conduction voltage drop of the power switch device, U D is the conduction voltage drop of the diode, t1 is the conduction time of the power switch tube device, T is the PWM signal period, R is the internal resistance of the stator coil (that is, the resistance value of the equivalent resistance of the stator coil), and i is the current of the stator coil.

[0051] Solving equations (1) and (2) together, we can obtain the stator coil current i (i.e., the average value of the stator coil ripple current):

[0052]

[0053] Where i max is the maximum ripple current of the stator coil, i min is the minimum value of the ripple current of the stator coil, i is the current of the stator coil (i.e. the average value of the ripple current of the stator coil). Due to the freewheeling state of the three-level power amplifier and the conduction voltage drop U on and the forward voltage drop U of the freewheeling diode D Therefore, the conduction voltage drop U of the power switch device cannot be ignored in the calculation. on and the forward voltage drop U of the freewheeling diode D Therefore, formula (3) can be expressed as:

[0054]

[0055] Where q is the duty cycle of the power amplifier's driving PWM signal. From equation (4), the relationship between the duty cycle of the three-level power amplifier's driving PWM signal and the stator coil current i (i.e., the average value of the stator coil's ripple current) is:

[0056]

[0057] The internal resistance value R of the stator coil and the temperature T R The relationship is:

[0058]

[0059] Where, T Ris the temperature when the internal resistance of the stator coil is R, R is the resistance value of the stator coil (i.e. the internal resistance of the stator coil), R0 is the resistance value of the stator coil when the temperature of the stator coil is T0℃, α T0 Temperature coefficient of the stator coil, T0 is the initial temperature of the stator coil.

[0060] From equations (5) and (6), we can get the duty cycle q of the driving PWM signal of the three-level power amplifier and the temperature T of the stator coil: R The relationship is:

[0061]

[0062] In the formula, since the stator coil current i (i.e. the average value of the stator coil ripple current) needs to be kept constant in the magnetic bearing control system, i, T0, R0, α T0 、U dc 、U D 、U on is a constant. From formula (7), if the duty cycle value q of the driving PWM signal of the three-level power amplifier is known, the temperature T of the stator coil at this time can be obtained by calculation. R . From formula (7), we can know the mathematical expression of the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil. The solution of the present invention, by monitoring the current of the stator coil of the magnetic bearing to be a certain constant value, by detecting the duty cycle value of the driving PWM signal of the power amplifier and applying the corresponding mathematical relationship, realizes the solution of sensorless detection of the temperature of the stator coil, realizes the measurement of the temperature of the stator coil without a sensor, and the detection method is simple and low-cost.

[0063] At step S120 , the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier are acquired in advance, also when the current of the stator coil is a set value.

[0064] In some embodiments, in step S120, when the current of the stator coil is a set value, the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier are pre-acquired. That is, the process of determining the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier, which are pre-determined when the current of the stator coil is a set value, includes any of the following determination situations:

[0065] In the first determination scenario, when the stator coil current is a set value, the initial temperature of the stator coil is obtained; and the resistance value of the stator coil obtained at the initial temperature of the stator coil is used as the initial resistance value of the stator coil. The set value may be the set stator coil current x, the initial temperature of the stator coil may be the set stator coil temperature of 25°C, and the initial resistance value of the stator coil may be the stator coil resistance value R0.

[0066] The second determination scenario: when the current of the stator coil is a set value, the maximum temperature of the stator coil is obtained; and the duty cycle value of the driving PWM signal of the power amplifier obtained at the maximum temperature of the stator coil is used as the maximum duty cycle value of the driving PWM signal of the power amplifier. The maximum temperature of the stator coil is the temperature T of the stator coil. max The maximum duty cycle value of the driving PWM signal of the power amplifier is q max .

[0067] Specifically, Figure 8 The figure is a flow chart of the temperature detection and over-temperature protection program of the stator coil of the magnetic bearing. Figure 8 As shown, the temperature detection and over-temperature protection program of the stator coil includes: step 1, setting the current of the stator coil to x; under the current x of the stator coil, setting the temperature of the stator coil to T0℃=25℃, the stator coil resistance value is R0, and the duty cycle value of the driving PWM signal is q x0 ; Under the current x of the stator coil, set the temperature of the stator coil to T max When the stator coil resistance is R max 、The duty cycle of the driving PWM signal is q max , then proceed to step 2. That is, first, it is necessary to measure the current of the stator coil at a constant value x: (i) When the temperature of the stator coil is 25°C, the resistance value of the stator coil R0 and the duty cycle value of the driving PWM signal q x0 ; (2) Stator coil temperature T max When the stator coil resistance value R max And the duty cycle value q of the driving PWM signal max ; Use the above measured data values ​​as a reference and write them into the controller MCU program.

[0068] At step S130, after the rotor is suspended, when the current of the stator coil is the set value, the current value of the duty cycle value of the driving PWM signal of the power amplifier is obtained, such as directly reading the current value of the duty cycle value of the driving PWM signal of the power amplifier from the controller MCU program in the magnetic bearing control system of the magnetic bearing system, and recording it as the current duty cycle value of the driving PWM signal of the power amplifier.

[0069] At step S140, the current temperature of the stator coil is determined based on the current duty cycle of the power amplifier's drive PWM signal, in combination with the initial temperature of the stator coil, the initial resistance of the stator coil, the maximum duty cycle of the power amplifier's drive PWM signal, and the correspondence between the duty cycle of the power amplifier's drive PWM signal under a three-level modulation scheme and the temperature of the stator coil, thereby detecting the current temperature of the stator coil. Specifically, based on the initial temperature of the stator coil, the initial resistance of the stator coil, and the maximum duty cycle of the power amplifier's drive PWM signal, which are predetermined when the current in the stator coil is at a set value, the current temperature of the stator coil is determined based on the current duty cycle of the power amplifier's drive PWM signal, in combination with the correspondence between the duty cycle of the power amplifier's drive PWM signal under a three-level modulation scheme and the temperature of the stator coil, thereby detecting the current temperature of the stator coil.

[0070] The present invention proposes a sensor-free method for detecting the temperature of the magnetic bearing's stator coil. By monitoring the stator coil current at a constant value and then detecting the duty cycle of the power amplifier's PWM signal, real-time stator coil temperature detection is achieved. This solution can be implemented within the existing magnetic bearing controller's hardware circuitry, eliminating the need for complex temperature detection circuitry or equipment. This simplifies the stator coil temperature measurement method and effectively ensures the magnetic bearing's performance and stability in harsh, high-temperature operating environments.

[0071] In some embodiments, step S140 combines the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the driving PWM signal of the power amplifier, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, and determines the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier, including: a process of calculating and displaying the current temperature of the stator coil.

[0072] The following combination Figure 2 The flowchart of an embodiment of calculating and displaying the current temperature of the stator coil in the method of the present invention further illustrates the specific process of calculating and displaying the current temperature of the stator coil in step S140, including: steps S210 to S220.

[0073] Step S210, determining whether the current duty cycle value of the driving PWM signal of the power amplifier is less than the maximum duty cycle value of the driving PWM signal of the power amplifier; wherein the current duty cycle value of the driving PWM signal of the power amplifier is currently obtained when the current of the stator coil is a set value; the maximum duty cycle value of the driving PWM signal of the power amplifier is pre-detected when the current of the stator coil is a set value.

[0074] In step S220, if it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is less than the maximum duty cycle value of the driving PWM signal of the power amplifier, based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil under the three-level modulation mode, the current temperature of the stator coil is calculated according to the current duty cycle value of the driving PWM signal of the power amplifier, and the current temperature of the stator coil is displayed (for example, the current temperature of the stator coil is sent to a host computer so that the host computer can display the detected real-time temperature of the stator coil in real time) to detect the current temperature of the stator coil.

[0075] In the solution of the present invention, when the current is a constant value in real time monitored by the controller MCU, the change in the duty cycle value of the power amplifier's drive PWM signal is detected to estimate the temperature of the stator coil. In this way, the temperature of the stator coil can be estimated as long as the duty cycle value of the power amplifier's drive PWM signal is known. The duty cycle value of the power amplifier's drive PWM signal can be directly read by the controller MCU program, thereby realizing the measurement of the stator coil temperature without a sensor, and the detection method is simple and low-cost.

[0076] In some implementations of radiation protection, in step S220, based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, the current temperature of the stator coil is calculated according to the current duty cycle value of the driving PWM signal of the power amplifier. The calculation includes: based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, taking the stator coil temperature corresponding to the duty cycle value of the driving PWM signal of the power amplifier that is the same as the current duty cycle value of the driving PWM signal of the power amplifier in the correspondence as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier. Specifically, when the correspondence between the duty cycle value of the driving PWM signal of the power amplifier in the three-level modulation mode predetermined when the current of the stator coil is a set value and the temperature of the stator coil includes the following formula, the initial temperature of the stator coil and the initial resistance value of the stator coil predetermined when the current of the stator coil is a set value are substituted into the following formula, and the current duty cycle value of the driving PWM signal of the power amplifier is used as the duty cycle value q of the driving PWM signal of the power amplifier in the following formula to calculate the temperature T of the stator coil. R , as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier:

[0077]

[0078] Specifically, if Figure 8 As shown, the temperature detection and over-temperature protection program of the stator coil also includes: Step 2, after controlling the rotor to float, the controller MCU directly outputs a drive PWM signal to the power amplifier to control the current of the stator coil. At this time, the controller MCU detects in real time the duty cycle value q of the output PWM signal when the current of the stator coil is x. x , and the temperature T of the stator coil at this moment is calculated by equation (7) x and the stator coil temperature T at this moment x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x . At the same time, judge q max >q x Is it true: If it is true, the controller MCU continues to detect the temperature T of the stator coil in real time. x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time.x .

[0079] like Figure 8 The stator coil temperature detection and over-temperature protection program shown in the figure includes the stator coil temperature estimation operation, which is the first operation: when the stator coil current is a certain constant value (this value can be directly obtained by the controller MCU program), the first step is to obtain the duty cycle value q of the driving PWM signal when the stator coil temperature is 25°C. x0 , which drives the duty cycle value q of the PWM signal x0 As the reference value, estimate the duty cycle value q of the driving PWM signal x The stator coil temperature T x The second step is to estimate the stator coil temperature T in real time. x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x , it is possible to detect the temperature of the stator coil without setting a sensor, and the detection method is simple and low-cost.

[0080] In some embodiments, in the scheme of the present invention, after obtaining the current duty cycle value of the driving PWM signal of the power amplifier, it also includes: a process of over-temperature protection of the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier.

[0081] The following combination Figure 3 The flowchart of an embodiment of over-temperature protection for the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier in the method of the present invention is shown, further illustrating the specific process of over-temperature protection for the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier, including: steps S310 to S320.

[0082] Step S310: Determine whether the current duty cycle of the power amplifier's driving PWM signal is less than the maximum duty cycle of the power amplifier's driving PWM signal. The current duty cycle of the power amplifier's driving PWM signal is currently acquired when the stator coil current is at a set value; the maximum duty cycle of the power amplifier's driving PWM signal is pre-detected when the stator coil current is at a set value.

[0083] Step S320: If it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is greater than or equal to the maximum duty cycle value of the driving PWM signal of the power amplifier, it is determined that the current temperature of the stator coil is overtemperature, and a signal for overtemperature protection of the current temperature of the stator coil is sent to control the rotor to stop floating.

[0084] Specifically, if Figure 8 As shown, the temperature detection and over-temperature protection program of the stator coil also includes: Step 2, after controlling the rotor to float, the controller MCU directly outputs a drive PWM signal to the power amplifier to control the current of the stator coil. At this time, the controller MCU detects in real time the duty cycle value q of the output PWM signal when the current of the stator coil is x. x , and the temperature T of the stator coil at this moment is calculated by equation (7) x and the stator coil temperature T at this moment x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x . At the same time, judge q max >q x Is it true: If not, the stator coil over-temperature protection signal is sent to control the rotor to stop floating.

[0085] like Figure 8 The temperature detection and over-temperature protection program of the stator coil shown in FIG1 also includes the operation of the stator coil temperature over-temperature protection, i.e., the second operation: the first step is to set the temperature of the stator coil to T according to formula (7). max When the duty cycle value of the driving PWM signal is q max Step (2) Based on the first operation, the temperature T of the stator coil at this moment is x Whether the stator coil temperature exceeds the set maximum value T max To judge, when the temperature of the stator coil T x Exceeding the maximum temperature of the stator coil, that is, the temperature of the stator coil T max In order to protect the safe operation of the device, the magnetic bearing controller issues a stop floating shaft instruction, and the magnetic bearing control system enters a stop working state, realizing over-temperature protection of the stator coil of the magnetic bearing to ensure the safety of the magnetic bearing operation.

[0086] The solution of the present invention realizes real-time contactless and sensorless detection of the temperature of the stator coil by detecting the change in the duty cycle of the driving PWM signal of the power amplifier when the current of the stator coil of the magnetic bearing is a certain constant value. There is no need to add any redundant structures or circuits. The change in the voltage across the stator coil is obtained by the information of the duty cycle of the driving PWM signal of the power amplifier, and the change in the internal resistance of the stator coil is obtained, thereby calculating the temperature of the stator coil. In related solutions, adding sensors will require adding corresponding circuits, increasing design costs; however, in the solution of the present invention, the temperature of the stator coil can be obtained without adding additional sensors, which is low-cost. In addition, the solution of the present invention is applicable to magnetic bearing controllers that adopt a pulse width modulation strategy, and is also applicable to the topology of power amplifiers of full-bridge and half-bridge circuits, and is also applicable to analog and digital power amplifiers.

[0087] According to the technical solution of this embodiment, for the stator coil of the magnetic bearing in the magnetic bearing system and the power amplifier using a three-level modulation method, the stator coil resistance value when the stator coil current is constant and the stator coil temperature is at the initial temperature is predetermined as the initial resistance value, and the duty cycle value of the power amplifier driving PWM signal when the stator coil temperature is at the maximum temperature is predetermined as the maximum duty cycle value. The initial stator coil temperature, the initial stator coil resistance value, and the maximum duty cycle value of the power amplifier obtained when the stator coil current is constant are used as reference values. In a magnetic bearing system, after the rotor of the magnetic bearing is suspended and the current of the stator coil is constant, a duty cycle value of a driving PWM signal of a power amplifier is used as a current duty cycle value. The corresponding relationship between the duty cycle value of the driving PWM signal of the three-level power amplifier and the temperature of the stator coil is used to determine the current temperature of the stator coil. Thus, by detecting the temperature of the stator coil based on the corresponding relationship between the duty cycle value of the driving PWM signal of the three-level power amplifier and the temperature of the stator coil when the current of the stator coil is constant, the detection method is simple and low-cost.

[0088] According to an embodiment of the present invention, a control device for a magnetic bearing system corresponding to the control method for the magnetic bearing system is also provided. Figure 4 The structure diagram of an embodiment of the device of the present invention is shown in FIG. The magnetic bearing system comprises a rotor, a stator coil and a control system, wherein the power amplifier in the control system adopts a three-level modulation method. Figure 5 Figure 1 is a control flow diagram of the magnetic bearing control system. Figure 5 As shown in the figure, the control process of the power amplifier of the magnetic bearing includes: using a current sensor to detect the current i of the stator coil and output a voltage u; the controller MCU obtains the driving PWM duty cycle value of the power amplifier based on the voltage u and applies a three-level modulation method; at the same time, it outputs the value to the power amplifier bridge circuit through an isolation circuit, and controls the power amplifier to output the current i to the stator coil. Figure 5In the example shown, when the temperature of the stator coil of the magnetic bearing increases, the internal resistance of the stator coil increases. If the current i of the stator coil needs to be kept constant at a certain value, the voltage across the stator coil needs to be increased to offset the change in the internal resistance of the stator coil. In the magnetic bearing control system, the voltage u across the stator coil is achieved by adjusting the duty cycle of the driving PWM signal of the power amplifier. Specifically, the voltage u across the stator coil is increased by increasing the duty cycle of the driving PWM signal of the power amplifier to offset the change in the resistance value of the stator coil. Based on this, the solution of the present invention proposes a solution for sensorless detection of the temperature of the stator coil by monitoring the current of the stator coil of the magnetic bearing to a certain constant value, detecting the duty cycle of the driving PWM signal of the power amplifier, and applying the corresponding mathematical relationship. In the solution of the present invention, as Figure 4 As shown, the control device of the magnetic bearing system includes: an acquisition unit 102 and a control unit 104.

[0089] The control unit 104 is configured to predetermine a correspondence between a duty cycle of a PWM signal driving the power amplifier under a three-level modulation scheme and a temperature of the stator coil when the current of the stator coil is a set value. The specific functions and processing of the control unit 104 are described in step S110.

[0090] In some embodiments, the power amplifier includes a power switch device and a diode. Figure 6 This is a schematic diagram of the H-bridge topology of the power amplifier. Figure 6 As shown, the power amplifier H bridge includes: MOS tube S1, MOS tube S2, diode D1 and diode D2. Bus voltage V dc The output of the supply voltage is connected to the drain of MOS transistor S1. The source of MOS transistor S1 is connected to the anode of diode D1 after passing through the stator coil. The output of the supply voltage is also connected to the cathode of diode D1. The source of MOS transistor S1 is connected to the cathode of diode D2, and the ground of diode D2 is GND. The anode of diode D1 is connected to the drain of MOS transistor S2, and the source of MOS transistor S2 is grounded. The stator coil has an equivalent inductance and an equivalent resistance, which is equivalent to an equivalent inductance and an equivalent resistance connected in series. The gates of MOS transistors S1 and S2 are both control terminals, used to input the duty cycle value of the driving PWM signal. Figure 7 Schematic diagram of the current waveform of a three-level power amplifier (i.e., a power amplifier with three-level modulation). Figure 7 Middle,U gs1 is the driving voltage of MOS tube S1, U gs2is the driving voltage of MOS transistor S2. To reduce current ripple, the power amplifier uses a three-level modulation scheme. The stator coil current now has three states: charging, freewheeling, and discharging. When both MOS transistors S1 and S2 are turned on, the stator coil current increases. When either power switch is turned on and the other is turned off, the stator coil current freewheels.

[0091] The control unit 104 predetermines a correspondence between a duty cycle of a driving PWM signal of the power amplifier and a temperature of the stator coil under a three-level modulation mode when the current of the stator coil is a set value, and the correspondence includes the following formula:

[0092]

[0093] Wherein, q is the duty cycle of the driving PWM signal of the power amplifier, i is the current of the stator coil, T R is the temperature of the stator coil, T0 is the initial temperature of the stator coil, R0 is the initial resistance value of the stator coil, α T0 is the temperature coefficient of the stator coil, U dc is the bus voltage of the power amplifier, U on is the on-state voltage drop of the power switch device in the power amplifier, U D is the conduction voltage drop of the diode in the power amplifier, K1, K2, K3, K4, and K5 are all calculation coefficients. Preferably, K1 is 0.5, K2 is 2, K3 is 2, K4 is 2, and K5 is 2.

[0094] Specifically, by Figure 6 and Figure 7 It can be obtained that when the power amplifier adopts three-level modulation, the expression of the stator coil current i is:

[0095]

[0096] Where L is the inductance of the stator coil, U is the equivalent inductance of the stator coil, dc is the bus voltage, U on is the conduction voltage drop of the power switch device, U D is the conduction voltage drop of the diode, t1 is the conduction time of the power switch tube device, T is the PWM signal period, R is the internal resistance of the stator coil (that is, the resistance value of the equivalent resistance of the stator coil), and i is the current of the stator coil.

[0097] Solving equations (1) and (2) together, we can obtain the stator coil current i (i.e., the average value of the stator coil ripple current):

[0098]

[0099] Where i max is the maximum ripple current of the stator coil, i min is the minimum value of the ripple current of the stator coil, i is the current of the stator coil (i.e. the average value of the ripple current of the stator coil). Due to the freewheeling state of the three-level power amplifier and the conduction voltage drop U on and the forward voltage drop U of the freewheeling diode D Therefore, the conduction voltage drop U of the power switch device cannot be ignored in the calculation. on and the forward voltage drop U of the freewheeling diode D Therefore, formula (3) can be expressed as:

[0100]

[0101] Where q is the duty cycle of the power amplifier's driving PWM signal. From equation (4), the relationship between the duty cycle of the three-level power amplifier's driving PWM signal and the stator coil current i (i.e., the average value of the stator coil's ripple current) is:

[0102]

[0103] The internal resistance value R of the stator coil and the temperature T R The relationship is:

[0104]

[0105] Where, T R is the temperature when the internal resistance of the stator coil is R, R is the resistance value of the stator coil (i.e. the internal resistance of the stator coil), R0 is the resistance value of the stator coil when the temperature of the stator coil is T0℃, α T0 Temperature coefficient of the stator coil, T0 is the initial temperature of the stator coil.

[0106] From equations (5) and (6), we can get the duty cycle q of the driving PWM signal of the three-level power amplifier and the temperature T of the stator coil: R The relationship is:

[0107]

[0108] In the formula, since the stator coil current i (i.e. the average value of the stator coil ripple current) needs to be kept constant in the magnetic bearing control system, i, T0, R0, α T0 、U dc 、U D 、U onis a constant. From formula (7), if the duty cycle value q of the driving PWM signal of the three-level power amplifier is known, the temperature T of the stator coil at this time can be obtained by calculation. R . From formula (7), we can know the mathematical expression of the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil. The solution of the present invention, by monitoring the current of the stator coil of the magnetic bearing to be a certain constant value, by detecting the duty cycle value of the driving PWM signal of the power amplifier and applying the corresponding mathematical relationship, realizes the solution of sensorless detection of the temperature of the stator coil, realizes the measurement of the temperature of the stator coil without a sensor, and the detection method is simple and low-cost.

[0109] The acquisition unit 102 is configured to pre-acquire the initial temperature of the stator coil, the initial resistance of the stator coil, and the maximum duty cycle of the driving PWM signal of the power amplifier, also when the current of the stator coil is at a set value. The specific functions and processing of the acquisition unit 102 are described in step S120.

[0110] In some embodiments, the acquisition unit 102 pre-acquires the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier when the current of the stator coil is a set value. That is, the process of determining the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier, which are pre-determined when the current of the stator coil is a set value, includes any of the following determination situations:

[0111] The first determination scenario: the acquisition unit 102 is specifically further configured to acquire the initial temperature of the stator coil when the current of the stator coil is a set value; and use the resistance value of the stator coil acquired at the initial temperature of the stator coil as the initial resistance value of the stator coil; wherein the set value is such as the set current x of the stator coil, the initial temperature of the stator coil is such as the set temperature of the stator coil at 25°C, and the initial resistance value of the stator coil is such as the stator coil resistance value R0.

[0112] The second determination scenario: the acquisition unit 102 is further configured to acquire the maximum temperature of the stator coil when the current of the stator coil is a set value; and use the duty cycle value of the driving PWM signal of the power amplifier acquired at the maximum temperature of the stator coil as the maximum duty cycle value of the driving PWM signal of the power amplifier. The maximum temperature of the stator coil is the temperature T of the stator coil. maxThe maximum duty cycle value of the driving PWM signal of the power amplifier is q max .

[0113] Specifically, Figure 8 The figure is a flow chart of the temperature detection and over-temperature protection program of the stator coil of the magnetic bearing. Figure 8 As shown, the temperature detection and over-temperature protection program of the stator coil includes: step 1, setting the current of the stator coil to x; under the current x of the stator coil, setting the temperature of the stator coil to 25°C, the stator coil resistance value to R0, and the duty cycle value of the driving PWM signal to q x0 ; Under the current x of the stator coil, set the temperature of the stator coil to T max When the stator coil resistance is R max 、The duty cycle of the driving PWM signal is q max , then proceed to step 2. That is, first, it is necessary to measure the current of the stator coil at a constant value x: (i) When the temperature of the stator coil is 25°C, the resistance value of the stator coil R0 and the duty cycle value of the driving PWM signal q x0 ; (2) Stator coil temperature T max When the stator coil resistance value R max And the duty cycle value q of the driving PWM signal max ; Use the above measured data values ​​as a reference and write them into the controller MCU program.

[0114] The acquisition unit 102 is further configured to, after the rotor is suspended and also when the current in the stator coil is at a set value, acquire a current value of the duty cycle of the driving PWM signal of the power amplifier, such as by directly reading the current value of the duty cycle of the driving PWM signal of the power amplifier from a program in a controller MCU of the magnetic bearing control system of the magnetic bearing system, and record the value as the current duty cycle value of the driving PWM signal of the power amplifier. The specific functions and processing of the acquisition unit 102 are further described in step S130.

[0115] The control unit 104 is further configured to determine the current temperature of the stator coil based on the current duty cycle of the power amplifier's drive PWM signal, in combination with the initial temperature of the stator coil, the initial resistance of the stator coil, the maximum duty cycle of the power amplifier's drive PWM signal, and the correspondence between the duty cycle of the power amplifier's drive PWM signal under a three-level modulation scheme and the temperature of the stator coil, thereby detecting the current temperature of the stator coil. Specifically, based on the initial temperature of the stator coil, the initial resistance of the stator coil, and the maximum duty cycle of the power amplifier's drive PWM signal, which are predetermined when the current in the stator coil is at a set value, the current duty cycle of the power amplifier's drive PWM signal is determined based on the current duty cycle of the power amplifier's drive PWM signal, in combination with the correspondence between the duty cycle of the power amplifier's drive PWM signal under a three-level modulation scheme and the temperature of the stator coil, thereby detecting the current temperature of the stator coil. The specific functions and processing of the control unit 104 are also shown in step S140.

[0116] The present invention proposes a sensor-free method for detecting the temperature of the magnetic bearing's stator coil. By monitoring the stator coil current at a constant value and then detecting the duty cycle of the power amplifier's PWM signal, real-time stator coil temperature detection is achieved. This solution can be implemented within the existing magnetic bearing controller's hardware circuitry, eliminating the need for complex temperature detection circuitry or equipment. This simplifies the stator coil temperature measurement method and effectively ensures the magnetic bearing's performance and stability in harsh, high-temperature operating environments.

[0117] In some embodiments, the control unit 104 determines the current temperature of the stator coil according to the current duty cycle of the driving PWM signal of the power amplifier based on the initial temperature of the stator coil, the initial resistance of the stator coil, the maximum duty cycle of the driving PWM signal of the power amplifier, and the correspondence between the duty cycle of the driving PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil, including: a process of calculating and displaying the current temperature of the stator coil, specifically as follows:

[0118] The control unit 104 is further configured to determine whether a current duty cycle of the power amplifier's driving PWM signal is less than a maximum duty cycle of the power amplifier's driving PWM signal. The current duty cycle of the power amplifier's driving PWM signal is currently acquired when the stator coil current is at a set value, and the maximum duty cycle of the power amplifier's driving PWM signal is pre-detected when the stator coil current is at a set value. The specific functions and processing of the control unit 104 are described in step S210.

[0119] The control unit 104 is further configured to, if it is determined that the current duty cycle of the power amplifier's driving PWM signal is less than the maximum duty cycle of the power amplifier's driving PWM signal, calculate the current temperature of the stator coil based on the current duty cycle of the power amplifier's driving PWM signal, based on the initial temperature of the stator coil and the initial resistance value of the stator coil, as well as the correspondence between the duty cycle of the power amplifier's driving PWM signal and the temperature of the stator coil under a three-level modulation scheme, and display the current temperature of the stator coil (e.g., sending the current temperature of the stator coil to a host computer so that the host computer can display the detected real-time temperature of the stator coil in real time), thereby detecting the current temperature of the stator coil. The specific functions and processing of the control unit 104 are further described in step S220.

[0120] In the solution of the present invention, when the current is a constant value in real time monitored by the controller MCU, the change in the duty cycle value of the power amplifier's drive PWM signal is detected to estimate the temperature of the stator coil. In this way, the temperature of the stator coil can be estimated as long as the duty cycle value of the power amplifier's drive PWM signal is known. The duty cycle value of the power amplifier's drive PWM signal can be directly read by the controller MCU program, thereby realizing the measurement of the stator coil temperature without a sensor, and the detection method is simple and low-cost.

[0121] In some embodiments, the control unit 104 calculates the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier based on the initial temperature and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil, including: the control unit 104 is further configured to, based on the correspondence between the initial temperature and the initial resistance value of the stator coil, and the duty cycle value of the driving PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil, use the stator coil temperature corresponding to the duty cycle value of the driving PWM signal of the power amplifier that is the same as the current duty cycle value of the driving PWM signal of the power amplifier in the correspondence as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier. Specifically, when the correspondence between the duty cycle value of the driving PWM signal of the power amplifier in the three-level modulation mode predetermined when the current of the stator coil is a set value and the temperature of the stator coil includes the following formula, the initial temperature of the stator coil and the initial resistance value of the stator coil predetermined when the current of the stator coil is a set value are substituted into the following formula, and the current duty cycle value of the driving PWM signal of the power amplifier is used as the duty cycle value q of the driving PWM signal of the power amplifier in the following formula to calculate the temperature T of the stator coil. R , as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier:

[0122]

[0123] Specifically, if Figure 8 As shown, the temperature detection and over-temperature protection program of the stator coil also includes: Step 2, after controlling the rotor to float, the controller MCU directly outputs a drive PWM signal to the power amplifier to control the current of the stator coil. At this time, the controller MCU detects in real time the duty cycle value q of the output PWM signal when the current of the stator coil is x. x , and the temperature T of the stator coil at this moment is calculated by equation (7) x and the stator coil temperature T at this moment x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x . At the same time, judge q max >q x Is it true: If it is true, the controller MCU continues to detect the temperature T of the stator coil in real time. xThe temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x .

[0124] like Figure 8 The stator coil temperature detection and over-temperature protection program shown in the figure includes the operation of estimating the temperature of the stator coil, that is, the first operation: when the current of the stator coil is a certain constant value (this value can be directly obtained by the controller MCU program), the first step is to obtain the duty cycle value q of the driving PWM signal when the stator coil temperature is T0℃=25℃. x0 , which drives the duty cycle value q of the PWM signal x0 As the reference value, estimate the duty cycle value q of the driving PWM signal x The stator coil temperature T x The second step is to estimate the stator coil temperature T in real time. x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x , it is possible to detect the temperature of the stator coil without setting a sensor, and the detection method is simple and low-cost.

[0125] In some embodiments, after obtaining the current duty cycle value of the driving PWM signal of the power amplifier, the control unit 104 further includes: performing over-temperature protection on the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier, specifically as follows:

[0126] The control unit 104 is further configured to determine whether a current duty cycle of the power amplifier's driving PWM signal is less than a maximum duty cycle of the power amplifier's driving PWM signal. The current duty cycle of the power amplifier's driving PWM signal is currently acquired when the stator coil current is at a set value, while the maximum duty cycle of the power amplifier's driving PWM signal is pre-detected when the stator coil current is at a set value. For details on the functions and processing of the control unit 104, see step S310.

[0127] The control unit 104 is further configured to, if it is determined that the current duty cycle of the power amplifier's driving PWM signal is greater than or equal to the maximum duty cycle of the power amplifier's driving PWM signal, determine that the current temperature of the stator coil is overtemperature, and transmit a stator coil overtemperature protection signal to control the rotor to float. The specific functions and processing of the control unit 104 are further described in step S320.

[0128] Specifically, if Figure 8As shown, the temperature detection and over-temperature protection program of the stator coil also includes: Step 2, after controlling the rotor to float, the controller MCU directly outputs a drive PWM signal to the power amplifier to control the current of the stator coil. At this time, the controller MCU detects in real time the duty cycle value q of the output PWM signal when the current of the stator coil is x. x , and the temperature T of the stator coil at this moment is calculated by equation (7) x and the stator coil temperature T at this moment x The temperature T of the stator coil is transmitted to the host computer monitoring interface and displayed in real time. x . At the same time, judge q max >q x Is it true: If not, the stator coil over-temperature protection signal is sent to control the rotor to stop floating.

[0129] like Figure 8 The temperature detection and over-temperature protection program of the stator coil shown in FIG1 also includes the operation of the stator coil temperature over-temperature protection, i.e., the second operation: the first step is to set the temperature of the stator coil to T according to formula (7). max When the duty cycle value of the driving PWM signal is q max Step (2) Based on the first operation, the temperature T of the stator coil at this moment is x Whether the stator coil temperature exceeds the set maximum value T max To judge, when the temperature of the stator coil T x Exceeding the maximum temperature of the stator coil, that is, the temperature of the stator coil T max In order to protect the safe operation of the device, the magnetic bearing controller issues a stop floating shaft instruction, and the magnetic bearing control system enters a stop working state, realizing over-temperature protection of the stator coil of the magnetic bearing to ensure the safety of the magnetic bearing operation.

[0130] The solution of the present invention realizes real-time contactless and sensorless detection of the temperature of the stator coil by detecting the change in the duty cycle of the driving PWM signal of the power amplifier when the current of the stator coil of the magnetic bearing is a certain constant value. There is no need to add any redundant structures or circuits. The change in the voltage across the stator coil is obtained by the information of the duty cycle of the driving PWM signal of the power amplifier, and the change in the internal resistance of the stator coil is obtained, thereby calculating the temperature of the stator coil. In related solutions, adding sensors will require adding corresponding circuits, increasing design costs; however, in the solution of the present invention, the temperature of the stator coil can be obtained without adding additional sensors, which is low-cost. In addition, the solution of the present invention is applicable to magnetic bearing controllers that adopt a pulse width modulation strategy, and is also applicable to the topology of power amplifiers of full-bridge and half-bridge circuits, and is also applicable to analog and digital power amplifiers.

[0131] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0132] According to an embodiment of the present invention, a magnetic bearing system corresponding to the control device of the magnetic bearing system is also provided. The magnetic bearing system may include: the control device of the magnetic bearing system described above.

[0133] Since the processing and functions implemented by the magnetic bearing system of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned device, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0134] According to an embodiment of the present invention, a computer program product corresponding to a magnetic bearing system is further provided, comprising a computer program. When the computer program is executed by a processor, the steps of the control method of the magnetic bearing system described above are implemented.

[0135] Since the processing and functions implemented by the product of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned magnetic bearing system, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0136] According to an embodiment of the present invention, a storage medium corresponding to the control method of the magnetic bearing system is also provided, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the steps of the control method of the magnetic bearing system described above.

[0137] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0138] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0139] The foregoing description is merely an embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of the claims.

Claims

1. A control method for a magnetic bearing system, characterized in that: The magnetic bearing system comprises a rotor, a stator coil and a control system, wherein a power amplifier in the control system adopts a three-level modulation mode; and the control method of the magnetic bearing system comprises: When the current of the stator coil is a set value, a corresponding relationship between a duty cycle value of a driving PWM signal of the power amplifier and a temperature of the stator coil under a three-level modulation mode is predetermined; When the current of the stator coil is a set value, obtaining in advance the initial temperature of the stator coil, the initial resistance value of the stator coil, and the maximum duty cycle value of the driving PWM signal of the power amplifier; After the rotor is suspended, when the current of the stator coil is at a set value, obtaining a current duty cycle value of the driving PWM signal of the power amplifier; In combination with the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the driving PWM signal of the power amplifier, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil under the three-level modulation mode, the current temperature of the stator coil is determined according to the current duty cycle value of the driving PWM signal of the power amplifier, so as to realize the detection of the current temperature of the stator coil.

2. The control method of the magnetic bearing system according to claim 1, characterized in that: The power amplifier comprises a power switch tube device and a diode; The predetermined correspondence between the duty cycle of the driving PWM signal of the power amplifier and the temperature of the stator coil under the three-level modulation mode includes the following formula: Wherein, q is the duty cycle of the driving PWM signal of the power amplifier, i is the current of the stator coil, T R is the temperature of the stator coil, T0 is the initial temperature of the stator coil, R0 is the initial resistance value of the stator coil, α T0 is the temperature coefficient of the stator coil, U dc is the bus voltage of the power amplifier, U on is the on-state voltage drop of the power switch device in the power amplifier, U D is the conduction voltage drop of the diode in the power amplifier, and K1, K2, K3, K4, and K5 are all calculation coefficients.

3. The control method of the magnetic bearing system according to claim 1, characterized in that: Pre-acquiring an initial temperature of the stator coil, an initial resistance value of the stator coil, and a maximum duty cycle value of a driving PWM signal of the power amplifier, including: Acquiring an initial temperature of the stator coil; and using the resistance value of the stator coil acquired at the initial temperature of the stator coil as the initial resistance value of the stator coil; Acquire the maximum temperature of the stator coil; and use the duty cycle value of the driving PWM signal of the power amplifier acquired at the maximum temperature of the stator coil as the maximum duty cycle value of the driving PWM signal of the power amplifier.

4. The control method of the magnetic bearing system according to any one of claims 1 to 3, characterized in that: Determining the current temperature of the stator coil according to the current duty cycle of the drive PWM signal of the power amplifier based on the initial temperature of the stator coil, the initial resistance of the stator coil, the maximum duty cycle of the drive PWM signal of the power amplifier, and the correspondence between the duty cycle of the drive PWM signal of the power amplifier and the temperature of the stator coil in a three-level modulation mode includes: determining whether a current duty cycle value of the driving PWM signal of the power amplifier is less than a maximum duty cycle value of the driving PWM signal of the power amplifier; If it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is less than the maximum duty cycle value of the driving PWM signal of the power amplifier, based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier and the temperature of the stator coil under the three-level modulation mode, the current temperature of the stator coil is calculated according to the current duty cycle value of the driving PWM signal of the power amplifier, and the current temperature of the stator coil is displayed.

5. The control method of the magnetic bearing system according to claim 4, characterized in that: Calculating the current temperature of the stator coil based on the initial temperature and the initial resistance of the stator coil, and the corresponding relationship between the duty cycle of the driving PWM signal of the power amplifier in a three-level modulation mode and the temperature of the stator coil, and according to the current duty cycle of the driving PWM signal of the power amplifier, includes: Based on the initial temperature of the stator coil and the initial resistance value of the stator coil, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, the temperature of the stator coil corresponding to the duty cycle value of the driving PWM signal of the power amplifier that is the same as the current duty cycle value of the driving PWM signal of the power amplifier in the correspondence is used as the current temperature of the stator coil corresponding to the current duty cycle value of the driving PWM signal of the power amplifier.

6. The control method of the magnetic bearing system according to any one of claims 1 to 3 and 5, characterized in that: Also includes: determining whether a current duty cycle value of the driving PWM signal of the power amplifier is less than a maximum duty cycle value of the driving PWM signal of the power amplifier; If it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is greater than or equal to the maximum duty cycle value of the driving PWM signal of the power amplifier, a current temperature over-temperature protection signal of the stator coil is sent to control the rotor to stop floating.

7. The control method of the magnetic bearing system according to claim 4, characterized in that: Also includes: determining whether a current duty cycle value of the driving PWM signal of the power amplifier is less than a maximum duty cycle value of the driving PWM signal of the power amplifier; If it is determined that the current duty cycle value of the driving PWM signal of the power amplifier is greater than or equal to the maximum duty cycle value of the driving PWM signal of the power amplifier, a current temperature over-temperature protection signal of the stator coil is sent to control the rotor to stop floating.

8. A control device for a magnetic bearing system, characterized in that: The magnetic bearing system comprises a rotor, a stator coil and a control system, wherein the power amplifier in the control system adopts a three-level modulation mode; the control device of the magnetic bearing system comprises: a control unit configured to predetermine a correspondence between a duty cycle value of a driving PWM signal of the power amplifier and a temperature of the stator coil in a three-level modulation mode when the current of the stator coil is a set value; an acquisition unit configured to, when the current of the stator coil is a set value, pre-acquire an initial temperature of the stator coil, an initial resistance value of the stator coil, and a maximum duty cycle value of a driving PWM signal of the power amplifier; The acquisition unit is further configured to acquire a current duty cycle value of the driving PWM signal of the power amplifier when the current of the stator coil is a set value after the rotor is suspended; The control unit is further configured to combine the initial temperature of the stator coil, the initial resistance value of the stator coil, the maximum duty cycle value of the driving PWM signal of the power amplifier, and the correspondence between the duty cycle value of the driving PWM signal of the power amplifier under the three-level modulation mode and the temperature of the stator coil, and determine the current temperature of the stator coil according to the current duty cycle value of the driving PWM signal of the power amplifier, so as to realize the detection of the current temperature of the stator coil.

9. A magnetic bearing system, characterized in that: include: The control device for the magnetic bearing system according to claim 8.

10. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the control method of the magnetic bearing system according to any one of claims 1 to 7.

11. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for controlling a magnetic bearing system according to any one of claims 1 to 7 are implemented.

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