A method and system for self-identifying idling speed of a magnetic levitation compressor

Abstract

The present invention relates to a method and system for self-identifying the idling speed of a magnetic levitation compressor, the method comprising: when the current of the power supply line of the motor is detected to be zero, collecting the three-phase line voltage of the motor; converting the three-phase line voltage into a two-phase line voltage; normalizing the converted two-phase line voltage to obtain a normalized value; and calculating the motor speed according to the normalized value. The technical solution provided by the present invention realizes the accurate identification of the full range of speeds during the idling process of the magnetic levitation compressor through a line voltage normalized phase-locked algorithm, avoids the problem of unbalanced compensation failure of the bearing controller due to inaccurate speed, and improves the reliability of the magnetic levitation compressor.

Description

Technical Field

[0001] The invention belongs to the field of self-identification control, and in particular relates to a method and system for self-identifying an idling speed of a magnetic suspension compressor. Background Art

[0002] The magnetic suspension compressor uses magnetic suspension bearings, and the shaft and bearing rotate without contact, which reduces energy loss. The high-speed two-stage compressor with integrated variable frequency drive reduces the speed when the condensing temperature drops or the heat load drops, thereby reducing energy consumption. Due to the above characteristics, the magnetic suspension compressor is widely used.

[0003] The control of the magnetic levitation compressor includes two parts: motor drive and bearing control (except passive bearings). Its shutdown is different from that of ordinary compressors. After shutdown, the bearing control needs to continue to work while the shaft is idling by inertia to maintain the stable suspension of the shaft until the motor speed drops to 0 before it can stop working. The imbalance of the shaft will have a great impact on the bearing control. In severe cases, the shaft will collide with the protective bearing, so imbalance compensation control is required. The key to imbalance compensation is the real-time running speed of the motor. There are many mature algorithms that can accurately estimate the rotation speed during normal driving of the motor, but these methods are often not applicable during shutdown idling. At this time, the bearing is easy to become unstable during imbalance compensation, and in severe cases, the protective bearing of the magnetic levitation compressor will be damaged.

[0004] Therefore, it is necessary to provide a method and system for self-identifying the idling speed of a magnetic levitation compressor to solve the deficiencies of the prior art. Summary of the invention

[0005] In order to solve the problem in the prior art that the rotation speed of a motor cannot be calculated when the motor is stopped and idling, the present invention provides a method and system for self-identifying the idling rotation speed of a magnetic levitation compressor.

[0006] A method for self-identifying an idling speed of a magnetic levitation compressor, wherein the magnetic levitation compressor comprises a motor and a bearing, and the method comprises:

[0007] When it is detected that the current of the power supply line of the motor is zero, collecting the three-phase line voltage of the motor;

[0008] Converting the three-phase line voltage into a two-phase line voltage;

[0009] Normalizing the converted two-phase line voltage to obtain a normalized value;

[0010] The motor speed is calculated according to the normalized value.

[0011] Furthermore, converting the three-phase line voltage into a two-phase line voltage comprises:

[0012] The three-phase line voltage is subjected to coordinate transformation to obtain a two-phase line voltage in a two-phase stationary coordinate system.

[0013] Furthermore, the coordinate transformation is shown in the following formula:

[0014]

[0015] Among them, e α and e β are the components of the line voltage in the two-phase stationary coordinate system; e ab and e bc They are the components of the line voltage in the three-phase stationary coordinate system.

[0016] Furthermore, the converted two-phase line voltages are normalized to obtain normalized values, including:

[0017] The normalization is shown as follows:

[0018]

[0019] in, and are the normalized values ​​of line voltage in the two-phase stationary coordinate system; e α and e β They are the components of the line voltage in the two-phase stationary coordinate system.

[0020] Further, calculating the motor speed according to the normalized value includes:

[0021] Calculate the difference between the normalized values ​​of the two-phase line voltages;

[0022] The difference is subjected to PI adjustment calculation to obtain the actual value of the motor speed.

[0023] Furthermore, the calculation of the difference between the normalized values ​​of the two-phase line voltages includes:

[0024] The difference is calculated as follows:

[0025]

[0026] sinΔθ=Δθ

[0027] in, and are the normalized values ​​of line voltage in the two-phase stationary coordinate system; ω r is the motor speed; f is the permanent magnet flux; θ is the phase angle of the line voltage; is the actual value of the line voltage phase angle.

[0028] A self-identification system for idling speed of a magnetic levitation compressor, the magnetic levitation compressor comprising a motor and a bearing, the system comprising:

[0029] a current detection circuit connected to the power supply line of the motor, wherein the current detection circuit outputs a control signal when detecting that the current of the power supply line is zero;

[0030] A voltage detection circuit, wherein the control end of the voltage detection circuit is connected to the output end of the current detection circuit, and the collection end is connected to the three-phase voltage line of the motor; the control end of the voltage detection circuit collects the voltage of the three-phase voltage line when receiving a control signal;

[0031] A voltage conversion circuit, the input end of which is connected to the voltage detection circuit, and is used to convert the voltage collected by the voltage conversion circuit into a two-phase voltage;

[0032] A per-unit processing circuit, wherein an input end of the per-unit processing circuit is connected to the voltage conversion circuit;

[0033] A calculator is connected to the per-unit processing circuit and is used to calculate the rotation speed of the motor.

[0034] Furthermore, the voltage detection circuit is a differential sampling circuit.

[0035] Furthermore, the calculator includes: a comparator, a PI regulator and an integrator connected in sequence.

[0036] A magnetic levitation compressor comprises the idling speed self-identification system of the magnetic levitation compressor described in any one of the above.

[0037] The technical solution provided by the present invention has the following advantages compared with the closest prior art:

[0038] The technical solution provided by the present invention first collects the three-phase line voltage of the motor when the current of the power supply line of the motor is detected to be zero, then converts the three-phase line voltage into a two-phase line voltage through coordinate transformation, normalizes the two-phase line voltage to obtain a normalized value, and finally calculates the motor speed according to the normalized value. The present invention realizes the accurate identification of the full range of speeds during the idling process of the magnetic levitation compressor through the line voltage normalization phase-locking algorithm, avoids the problem of unbalanced compensation failure caused by inaccurate speed of the bearing controller, and improves the reliability of the magnetic levitation compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the present invention;

[0040] Figure 2 is a schematic diagram of coordinate system transformation of three phases to two phases in an embodiment of the present invention;

[0041] Figure 3 It is a structural diagram of the speed identification principle based on the line voltage phase-locked loop in an embodiment of the present invention;

[0042] Figure 4 1 is a schematic diagram of a differential sampling circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the present invention provides a method for self-identification of idling speed of a magnetic levitation compressor, wherein the magnetic levitation compressor comprises a motor and a bearing, and the method comprises:

[0045] When it is detected that the current of the power supply line of the motor is zero, collecting the three-phase line voltage of the motor;

[0046] Converting the three-phase line voltage into a two-phase line voltage;

[0047] Normalizing the converted two-phase line voltage to obtain a normalized value;

[0048] The motor speed is calculated according to the normalized value.

[0049] In the embodiment of the present application, the three-phase line voltage of the motor is firstly collected when the current of the power supply line of the motor is detected to be zero, and then the three-phase line voltage is converted into a two-phase line voltage through coordinate transformation, and the two-phase line voltage is normalized to obtain a normalized value, and finally the motor speed is calculated according to the normalized value. The present invention realizes the accurate identification of the full range of speeds during the idling process of the magnetic levitation compressor through the line voltage normalization phase-locking algorithm, avoids the problem of unbalanced compensation failure caused by inaccurate speed of the bearing controller, and improves the reliability of the magnetic levitation compressor.

[0050] In some embodiments of the present application, the three-phase line voltage is converted into a two-phase line voltage, such as Figure 2 As shown, including:

[0051] The three-phase line voltage is subjected to coordinate transformation to obtain a two-phase line voltage in a two-phase stationary coordinate system.

[0052] That is, the three-phase line voltage is converted from the ABC coordinate system to the αβ coordinate system.

[0053] The coordinate transformation is shown below:

[0054]

[0055] Among them, e α and e β are the components of the line voltage in the two-phase stationary coordinate system; e ab and e bc They are the components of the line voltage in the three-phase stationary coordinate system.

[0056] Among them, the two-phase line voltage satisfies the following relationship in the two-phase stationary coordinate system:

[0057]

[0058] Among them, θ is the angle between the line voltage and the A axis, that is, the phase angle of the line voltage, ω r is the motor speed, ψ f is the permanent magnet flux or line voltage constant.

[0059] In some embodiments of the present application, in order to improve the adaptability and robustness of the algorithm, the converted two-phase line voltage is normalized to obtain a normalized value, including:

[0060] The normalization is shown as follows:

[0061]

[0062] in, and are the normalized values ​​of line voltage in the two-phase stationary coordinate system; e α and e β They are the components of the line voltage in the two-phase stationary coordinate system.

[0063] In some embodiments of the present application, the normalized value is used to calculate the motor speed, including:

[0064] Calculate the difference between the normalized values ​​of the two-phase line voltages;

[0065] The difference is subjected to PI adjustment calculation to obtain the actual value of the motor speed.

[0066] The difference is calculated as follows:

[0067]

[0068] When Δθ is small enough, it can be approximately considered that: sinΔθ=Δθ.

[0069] The actual value of the motor speed is calculated by designing the PI regulator through the angle error Δθ The identified speed The integral is When the motor is idling, the speed identification principle structure diagram based on the line voltage phase-locked loop is as follows: Figure 3 shown.

[0070] in, and are the normalized values ​​of line voltage in the two-phase stationary coordinate system; ω r is the motor speed; f is the permanent magnet flux; θ is the phase angle of the line voltage; is the actual value of the line voltage phase angle.

[0071] Based on the same inventive concept, the present invention also provides an idling speed self-identification system for a magnetic levitation compressor, wherein the magnetic levitation compressor comprises a motor and a bearing, and the system comprises:

[0072] a current detection circuit connected to the power supply line of the motor, wherein the current detection circuit outputs a control signal when detecting that the current of the power supply line is zero;

[0073] A voltage detection circuit, wherein the control end of the voltage detection circuit is connected to the output end of the current detection circuit, and the collection end is connected to the three-phase voltage line of the motor; the control end of the voltage detection circuit collects the voltage of the three-phase voltage line when receiving a control signal;

[0074] A voltage conversion circuit, the input end of which is connected to the voltage detection circuit, and is used to convert the voltage collected by the voltage conversion circuit into a two-phase voltage;

[0075] A per-unit processing circuit, wherein an input end of the per-unit processing circuit is connected to the voltage conversion circuit;

[0076] A calculator is connected to the per-unit processing circuit and is used to calculate the rotation speed of the motor.

[0077] Wherein, the voltage detection circuit is a differential sampling circuit, and the circuit schematic diagram is as follows: Figure 4 shown.

[0078] Optionally, the differential sampling circuit includes:

[0079] An RC filter circuit, wherein an input end of the RC filter circuit is connected to a sampling signal terminal, and is used to filter the sampling signal;

[0080] The amplifier circuit has an input end connected to the output end of the RC filter circuit, and is used to amplify the filtered sampling signal and transmit the amplified sampling signal to the sampler terminal to obtain the line voltage of the motor.

[0081] Optionally, the sampling signal terminal includes a sampling signal first terminal and a sampling signal second terminal, and the RC filter circuit includes:

[0082] A first resistor, a first end of the first resistor is connected to the sampling signal first terminal;

[0083] A second resistor, a first end of the second resistor is connected to the sampling signal second terminal;

[0084] a first capacitor, wherein a first end of the first capacitor is connected to a second end of the first resistor, and a second end of the first capacitor is grounded;

[0085] A second capacitor, wherein a first end of the second capacitor is connected to a second end of the second resistor, and a second end of the second capacitor is grounded.

[0086] Optionally, the amplifying circuit includes:

[0087] an operational amplifier, wherein a non-inverting input terminal of the operational amplifier is connected to the second end of the second resistor, and an inverting input terminal of the amplifier is connected to the second end of the first resistor;

[0088] a third resistor, a first end of the third resistor being connected to the output end of the operational amplifier, and a second end of the third resistor being connected to the sampler terminal;

[0089] a third capacitor, wherein a first end of the third capacitor is connected to the second end of the third resistor, and a second end of the third capacitor is grounded;

[0090] a fifth resistor, wherein a first end of the fifth resistor is connected to the inverting input end of the operational amplifier, and an output end of the fifth resistor is connected to the output end of the operational amplifier;

[0091] A fifth capacitor, wherein a first end of the fifth capacitor is connected to the first end of the fifth resistor, and a second end of the fifth capacitor is connected to the second end of the fifth resistor.

[0092] Optionally, the differential sampling circuit further includes:

[0093] a fourth resistor, wherein a first end of the fourth resistor is connected to the second end of the second resistor, and a second end of the fourth resistor is connected to a given power signal terminal;

[0094] A fourth capacitor, wherein a first end of the fourth capacitor is connected to the first end of the fourth resistor, and a second end of the fourth capacitor is connected to the second end of the second resistor.

[0095] Optionally, the calculator includes: a comparator, a PI regulator and an integrator connected in sequence.

[0096] The normalized values ​​of the two-phase line voltage output by the normalization processing circuit are multiplied by the cosine value and sine value of the two-phase line voltage phase angle and input into the comparator to obtain the difference of the normalized values ​​of the two-phase line voltage; the difference is then input into the PI regulator for adjustment to obtain the actual value of the motor speed; the actual value of the motor speed is input into the integrator to obtain the actual value of the two-phase line voltage phase angle. When the motor is idling, the speed identification principle structure diagram based on the line voltage phase-locked loop is as follows Figure 3 shown.

[0097] The present invention also provides a magnetic levitation compressor, comprising any one of the above-mentioned idling speed self-identification systems for the magnetic levitation compressor.

[0098] It should be noted that, in this document, relational terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0099] It is understood that the embodiments described herein may be implemented in hardware, software, firmware, middleware, microcode, or a combination thereof. For hardware implementation, the processing unit may be implemented in one or more application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field programmable gate arrays (FPGA), general purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in the present application, or a combination thereof.

[0100] For software implementation, the technology described herein can be implemented by a unit that performs the functions described herein. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

[0101] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0102] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0103] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0104] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks or optical disks.

[0105] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for self-identifying the idling speed of a magnetic levitation compressor, wherein the magnetic levitation compressor comprises a motor and a bearing, characterized in that: The method comprises: When it is detected that the current of the power supply line of the motor is zero, collecting the three-phase line voltage of the motor; Converting the three-phase line voltage into a two-phase line voltage; Normalizing the converted two-phase line voltage to obtain a normalized value; Calculate the motor speed according to the normalized value; Converting the three-phase line voltage into a two-phase line voltage comprises: The three-phase line voltage is subjected to coordinate transformation to obtain the two-phase line voltage in a two-phase stationary coordinate system. The coordinate transformation is shown in the following formula: Among them, e α and e β are the components of the line voltage in the two-phase stationary coordinate system; e ab and e bc They are the components of the line voltage in the three-phase stationary coordinate system, among which the two-phase line voltage satisfies the following relationship in the two-phase stationary coordinate system: Among them, θ is the angle between the line voltage and the A axis, that is, the phase angle of the line voltage, ω r is the motor speed, ψ f is the permanent magnet flux or line voltage constant.

2. The method for self-identification of idling speed of a magnetic levitation compressor according to claim 1, characterized in that: The converted two-phase line voltages are normalized to obtain normalized values, including: The normalization is shown as follows: in, and are the normalized values ​​of line voltage in the two-phase stationary coordinate system; e α and e β They are the components of the line voltage in the two-phase stationary coordinate system.

3. The method for self-identification of idling speed of a magnetic levitation compressor according to claim 1, characterized in that: Calculating the motor speed according to the normalized value includes: Calculate the difference between the normalized values ​​of the two-phase line voltages; The difference is subjected to PI adjustment calculation to obtain the actual value of the motor speed.

4. The method for self-identification of idling speed of a magnetic levitation compressor according to claim 3, characterized in that: The step of calculating the difference between the normalized values ​​of the two-phase line voltages comprises: The difference is calculated as follows: sinΔθ=Δθ in, and are the normalized values ​​of line voltage in the two-phase stationary coordinate system; ω r is the motor speed; f is the permanent magnet flux; θ is the phase angle of the line voltage; is the actual value of the line voltage phase angle.

5. A magnetic levitation compressor idling speed self-identification system, the magnetic levitation compressor comprising a motor and a bearing, characterized in that: The system comprises: a current detection circuit connected to the power supply line of the motor, wherein the current detection circuit outputs a control signal when detecting that the current of the power supply line is zero; A voltage detection circuit, wherein the control end of the voltage detection circuit is connected to the output end of the current detection circuit, and the collection end is connected to the three-phase voltage line of the motor; the control end of the voltage detection circuit collects the voltage of the three-phase voltage line when receiving a control signal; A voltage conversion circuit, the input end of which is connected to the voltage detection circuit, is used to convert the voltage collected by the voltage conversion circuit into a two-phase voltage, specifically comprising: The three-phase line voltage is transformed into a coordinate system to obtain a two-phase line voltage in a two-phase stationary coordinate system. The coordinate transformation is shown in the following formula: Among them, e α and e β are the components of the line voltage in the two-phase stationary coordinate system; e ab and e bc They are the components of the line voltage in the three-phase stationary coordinate system, among which the two-phase line voltage satisfies the following relationship in the two-phase stationary coordinate system: Among them, θ is the angle between the line voltage and the A axis, that is, the phase angle of the line voltage, ω r is the motor speed, ψ f is the permanent magnet flux or line voltage constant; A per-unit processing circuit, wherein an input end of the per-unit processing circuit is connected to the voltage conversion circuit; A calculator, connected to the per-unit processing circuit, for calculating the rotation speed of the motor; The voltage detection circuit is a differential sampling circuit, comprising: an RC filter circuit, the input end of which is connected to a sampling signal terminal, for filtering the sampling signal; The amplifier circuit has an input end connected to the output end of the RC filter circuit, and is used to amplify the filtered sampling signal and transmit the amplified sampling signal to the sampler terminal to obtain the line voltage of the motor.

6. The idling speed self-identification system of a magnetic levitation compressor according to claim 5, characterized in that: The calculator comprises: a comparator, a PI regulator and an integrator which are connected in sequence.

7. A magnetic levitation compressor, characterized in that: A self-identification system for idling speed of a magnetically suspended compressor comprising the system as described in any one of claims 5 to 6.

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