A zero common-mode voltage modulation method, unit and magnetic levitation bearing control device

Abstract

The application discloses a zero common-mode voltage modulation method, a unit and a magnetic suspension bearing control device, and belongs to the technical field of magnetic suspension bearing control. The method comprises the following steps: calculating a normalized differential-mode voltage instruction and a common-mode voltage instruction; judging a sector number according to the differential-mode voltage instruction; calculating the normalized action time of each voltage vector according to the sector number, the differential-mode voltage instruction and the common-mode voltage instruction; calculating four duty cycles according to the normalized action time of each voltage vector, and then distributing the four duty cycles to four bridge arms according to the sector number N to generate corresponding modulation signals; and comparing the set carrier signal and the modulation signals of the four bridge arms by using a carrier comparison link to generate a PWM signal, so as to drive a magnetic bearing driving converter. The application can significantly inhibit the common-mode electromagnetic interference caused by the magnetic suspension bearing controller without affecting the normal control of the magnetic suspension bearing, and can avoid the damage to the protection bearing and the influence on the displacement sensor.

Description

Technical Field

[0001] This invention belongs to the field of magnetic levitation bearing control technology, and more specifically, relates to a zero common-mode voltage modulation method, unit, and magnetic levitation bearing control device. Background Technology

[0002] Active magnetic bearings possess excellent characteristics such as frictionless operation, low loss, and noiselessness, and are widely used in high-speed rotating machinery. The magnetic bearing controller primarily controls the winding current of the magnetic bearing through the switching action of a power electronic converter, thereby controlling the rotor position. The high-frequency switching action of the power electronic devices generates a high-frequency common-mode voltage, which in turn generates a high-frequency common-mode leakage current through the common-mode circuit formed by the stray parameters of the magnetic bearing.

[0003] Common-mode interference in existing technologies makes it difficult for magnetic levitation bearing controllers to meet electromagnetic compatibility standards; the resulting common-mode leakage current can corrode the protective bearing and threaten its safe operation; high-frequency common-mode voltage can also cause electromagnetic radiation in space, interfering with the position sensor signal and threatening the bearing's levitation control. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a zero common-mode voltage modulation method, unit, and magnetic levitation bearing control device. Its purpose is to achieve maximum DC voltage utilization in both differential-mode and common-mode voltage aspects, maintain the system's dynamic response speed, theoretically achieve zero common-mode interference voltage, and significantly suppress common-mode electromagnetic interference from the magnetic levitation bearing controller without affecting the normal control of the magnetic levitation bearing. This solves the technical problem of the difficulty in accurately and efficiently controlling magnetic levitation bearings in existing technologies.

[0005] To achieve the above objectives, according to one aspect of the present invention, a zero common-mode voltage modulation method is provided, comprising:

[0006] S1: The voltage command calculation unit receives the reference voltages of the four bridge arms on the magnetic bearing controller and calculates the normalized differential-mode voltage command and common-mode voltage command; the differential-mode voltage command includes the difference between the voltages of the two windings in the x-direction. The voltage difference between the two windings in the y direction The common-mode voltage command includes: the sum of the voltages of the two windings in the x-direction.

[0007] S2: The sector number N is determined based on the differential mode voltage command using the sector determination step;

[0008] S3: Using the action time calculation step, calculate the normalized action time of each voltage vector based on the sector number N, the differential mode voltage command, and the common mode voltage command;

[0009] S4: The duty cycle allocation step calculates four duty cycles based on the normalized action time of each voltage vector, and then allocates the four duty cycles to the four bridge arms according to the sector number N to generate corresponding modulation signals.

[0010] S5: The carrier comparison circuit compares the set carrier signal with the modulation signals of the four bridge arms to generate a PWM signal.

[0011] In one embodiment, in S1:

[0012] The voltage difference between the two windings in the x-direction Represented as:

[0013]

[0014] The voltage difference between the two windings in the y direction Represented as:

[0015]

[0016] The sum of the voltages of the two windings in the x-direction Represented as:

[0017]

[0018] in, This is the reference voltage for the bridge arm connecting the two windings in the x-direction. The reference voltage for the bridge arm connecting the two windings in the y-direction is v. N V is the voltage at the star connection of the four windings. dc This is the DC bus voltage.

[0019] In one embodiment, S2 includes:

[0020] The sector determination process is controlled by utilizing The corresponding sector number N is used as the basis for judgment.

[0021] In one embodiment, in S3: the normalized action time of each voltage vector includes:

[0022] First differential vector action time

[0023] Second differential vector action time

[0024] Reverse common mode vector action time t CM- ,

[0025] Positive vector action time t CM+ ;

[0026] The formulas for calculating the four duty cycles d1, d2, d3, and d4 are as follows: d1 = 0.5t CM- ;d2=d1+t DM1 d3 = d2 + t CM+ d4 = d3 + t DM2 .

[0027] In one embodiment, in step S4: a modulation signal is allocated to each bridge arm according to the sector number N and four duty cycles, and the allocation principle is as follows:

[0028]

[0029]

[0030]

[0031]

[0032] Wherein, the letter D represents the bridge arm modulation signal, the first subscript indicates the bridge arm number, and the second subscript indicates the signal strength of the modulation signal, satisfying D i1 ≤D i2 , i = 1, 2, 3, 4.

[0033] In one embodiment, the carrier signal is a triangular carrier; in step S5:

[0034] For each bridge arm, when the carrier signal is greater than the first modulation signal D i1 And less than the second modulation signal D i2 When the signal is high, the output PWM signal is high; otherwise, the output PWM signal is low.

[0035] The four PWM signals will be correspondingly distributed to the upper drive of the bridge arm connected to the two windings in the x direction and the lower drive of the bridge arm connected to the two windings in the y direction.

[0036] According to another aspect of the present invention, a zero common-mode voltage modulation unit is provided for performing the aforementioned zero common-mode voltage modulation method, comprising:

[0037] The voltage command calculation stage receives reference voltages from the four bridge arms of the magnetic bearing controller and calculates normalized differential-mode voltage commands and common-mode voltage commands. The differential-mode voltage command includes the voltage difference between the two windings in the x-direction. The voltage difference between the two windings in the y direction The common-mode voltage command includes: the sum of the voltages of the two windings in the x-direction.

[0038] The sector determination step is used to determine the sector number N based on the differential mode voltage command;

[0039] The action time calculation step is used to calculate the normalized action time of each voltage vector based on the sector number N, the differential mode voltage command, and the common mode voltage command.

[0040] The duty cycle allocation stage is used to calculate four duty cycles based on the normalized action time of each voltage vector, and then allocate the four duty cycles to the four bridge arms according to the sector number N to generate corresponding modulation signals.

[0041] The carrier comparison stage is used to compare the set carrier signal with the modulation signals of the four bridge arms to generate a PWM signal.

[0042] According to another aspect of the present invention, a magnetic levitation bearing control device with common-mode interference suppression capability is provided, comprising:

[0043] A magnetic bearing drive converter, connected to a magnetic levitation bearing, is composed of power electronic devices and is used to amplify power according to a gate drive signal to drive the two-degree-of-freedom eight-pole magnetic levitation bearing.

[0044] A displacement control unit, connected to the magnetic levitation bearing, is used to collect the displacement deviation signal of the magnetic levitation bearing and execute a position control algorithm to generate a current command value for the bearing winding.

[0045] A current control unit, connected to the displacement control unit, is used to receive the current command value to acquire the actual current value and execute a current control algorithm to generate command voltages for the four bridge arms.

[0046] The zero common-mode voltage modulation unit, connected to the current control unit, is used to receive command voltages from the four bridge arms and execute the zero common-mode voltage modulation method to generate gate drive signals and transmit them to the magnetic bearing drive converter.

[0047] In one embodiment, the magnetic bearing drive converter includes four switch bridge arms with a common DC bus, each connected to one end of one of the four windings of a two-degree-of-freedom eight-pole magnetic levitation bearing, and the other ends of the four windings are directly connected together.

[0048] According to another aspect of the invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0049] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0050] (1) The zero common-mode voltage modulation method proposed in this invention has the highest DC voltage utilization rate in both differential-mode voltage and common-mode voltage, without reducing the dynamic response speed of the system, and theoretically achieves zero common-mode interference voltage; it can significantly suppress the common-mode electromagnetic interference brought by the magnetic levitation bearing controller without affecting the normal control of the magnetic levitation bearing, and avoid its damage to the protective bearing and its impact on the displacement sensor.

[0051] (2) The magnetic levitation bearing control device and method with common mode interference suppression capability proposed in this invention can theoretically achieve zero common mode interference voltage without affecting normal current control, significantly reduce the common mode interference of the system, avoid the harm of common mode current to the bearing protection, reduce the interference to the displacement sensor, and increase the position control accuracy.

[0052] (3) The magnetic levitation bearing control device with common mode interference suppression capability proposed in this invention is designed for a typical eight-pole two-degree-of-freedom axial magnetic levitation bearing. It can be easily extended to more degrees of freedom, and suppress the common mode interference brought by the entire control system while realizing multi-degree-of-freedom control. Attached Figure Description

[0053] Figure 1 A magnetic levitation bearing control device with common-mode interference suppression capability is provided as an example of the present invention;

[0054] Figure 2 A vector diagram of the zero common-mode voltage modulation method proposed in this invention;

[0055] Figure 3 This is a block diagram of the zero common-mode voltage modulation method provided by the present invention;

[0056] Figure 4 The four PWM pulse waveforms output by the zero common-mode voltage modulation method proposed in this invention within one switching cycle;

[0057] Figure 5 This is a comparison diagram of the common-mode leakage current of the device and method proposed in this invention with that of conventional carrier comparison PWM.

[0058] Figure 6 This is a comparison chart of common-mode electromagnetic interference (EMI) between the device and method proposed in this invention and conventional carrier-based PWM. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0060] Figure 1 The magnetic levitation bearing control device with common-mode interference suppression capability proposed in this invention includes: a DC power supply 1, a bearing drive converter 2, a displacement control unit 3, a current control unit 4, and a zero common-mode voltage modulation unit 5;

[0061] DC power supply 1 is used to power the entire magnetic levitation bearing control system.

[0062] The magnetic bearing drive converter 2 is composed of power electronic devices and is used to amplify the power according to the gate drive signal to drive the two-degree-of-freedom eight-pole magnetic levitation bearing.

[0063] The displacement control unit 3 is used to acquire the displacement deviation signal of the magnetic levitation bearing, execute the position control algorithm, and generate the current command value of the bearing winding, which is then transmitted to the current control unit.

[0064] The current control unit 4 is used to receive current command values, acquire actual current values, execute current control algorithms, generate command voltages for the four bridge arms, and transmit them to the zero common-mode voltage modulation unit.

[0065] The zero common-mode voltage modulation unit 5 is used to receive the command voltage of the four bridge arms, execute the zero common-mode voltage modulation algorithm, and generate a gate drive signal to be transmitted to the magnetic bearing drive converter.

[0066] Furthermore, the magnetic bearing drive converter consists of four switching bridge arms sharing a DC bus, which are respectively connected to one end of the four windings of the two-degree-of-freedom eight-pole magnetic levitation bearing, and the other ends of the four windings are directly connected together.

[0067] Figure 2 This is a vector diagram illustrating the zero common-mode voltage modulation method proposed in this invention. The differential-mode voltage V across the two windings is shown in the x-direction. DMx The differential-mode voltage V on the two windings in the y direction DMy The common-mode voltage V on the two windings in the x-direction CM Using three orthogonal coordinate axes, a vector diagram of all switch states can be drawn. The six bold vectors are V3, V5, V6, V9, and V... 10 V 12 Their common characteristic is that two bridge arms output high levels, while the other two output low levels, thus ensuring that the common-mode voltage is zero. Specifically, V3 and V...12 These are two equal-sized, opposite vectors that contribute only to the common-mode voltage. They are used to implement the common-mode voltage command value and simultaneously synthesize a zero vector to fill the remaining time within the switching cycle. V5, V6, V9, V 10 These are four differential-mode voltage vectors, contributing only to the differential-mode voltage, and V DMx -V DMy The plane is divided into four sectors.

[0068] Figure 3 The diagram shows the block diagram of the zero common-mode voltage modulation method provided by the present invention. The zero common-mode voltage modulation method provided by the present invention includes a voltage command calculation stage, a sector judgment stage, an action time calculation stage, a duty cycle allocation stage, and a carrier comparison stage.

[0069] The voltage command calculation stage receives the reference voltages of the four bridge arms generated by the current control unit of the magnetic bearing controller and calculates the normalized differential-mode voltage command. and common-mode voltage command The differential mode voltage command is passed to the sector calculation stage, and the differential mode voltage command and common mode voltage command are passed to the action time calculation stage.

[0070] The sector determination stage is used to receive the normalized differential mode voltage, determine the sector number N, and pass the sector number to the action time calculation stage and the duty cycle calculation stage respectively.

[0071] The action time calculation stage is used to receive the sector number and the normalized voltage command, and calculate the normalized action time of each voltage vector.

[0072] The duty cycle allocation stage receives the sector number and vector action time, calculates four duty cycles based on the vector action time, allocates the four duty cycles to the four bridge arms based on the sector number, generates the corresponding modulation signal, and transmits it to the carrier comparison stage.

[0073] The carrier comparison stage is used to generate a PWM signal by comparing the modulation signals of the four bridge arms with the set carrier signal.

[0074] Furthermore, in the voltage command calculation stage, the voltage command... Defined as the difference in voltage between the two windings in the x-direction. Defined as the difference in voltage between the two windings in the y-direction. Defined as the sum of the voltages of the two windings in the x-direction, its calculation formula is:

[0075]

[0076]

[0077]

[0078] in, This is the reference voltage for the bridge arm connecting the two windings in the x-direction. The reference voltage for the bridge arm connecting the two windings in the y-direction is v. N V is the voltage at the star connection of the four windings. dc This is the DC bus voltage.

[0079] Furthermore, in the sector determination process, the determination criteria are as follows:

[0080]

[0081] Furthermore, the action time calculation includes two orthogonal differential-mode voltage vectors and two opposite common-mode voltage vectors, whose normalized vector action times are as follows:

[0082]

[0083]

[0084]

[0085]

[0086] Among them, t DM1 It is the time of action of the first differential vector, t DM2 It is the time of action of the second differential vector, t CM- It is the time of action of the reverse common-mode vector, t CM+ It is the time of action of the positive vector.

[0087] Furthermore, in the duty cycle allocation process, the formulas for calculating the four duty cycles are as follows:

[0088]

[0089] Where d1, d2, d3, and d4 are the four calculated duty cycles.

[0090] Furthermore, in the duty cycle allocation stage, two modulation signals are generated for each bridge arm based on the sector number and the four duty cycles. The allocation principle is as follows:

[0091]

[0092]

[0093] Wherein, the letter D represents the bridge arm modulation signal, the first subscript indicates the bridge arm number, and the second subscript indicates the modulation signal magnitude, satisfying D i1 ≤D i2 (i = 1, 2, 3, 4).

[0094] Preferably, the carrier in the carrier comparison stage is a triangular carrier. For each bridge arm, when the carrier is greater than the first modulation signal D... i1 And less than the second modulation signal D i2 Output a high level when the signal is active, otherwise output a low level.

[0095] Furthermore, the four PWM signals generated in the carrier comparison stage will be correspondingly distributed to the upper drive of the bridge arm connected by the two windings in the x direction and the lower drive of the bridge arm connected by the two windings in the y direction.

[0096] Figure 4 The zero common-mode voltage modulation method proposed in this invention outputs four PWM pulse waveforms within one switching cycle. By selecting the zero common-mode voltage vector to synthesize the reference voltage, it is equivalent to phase-shifting and aligning the four PWM signals, ensuring that at any given time, two bridge arms are connected to the positive DC bus and the other two bridge arms are connected to the negative DC bus, thereby achieving the elimination of high-frequency common-mode voltage.

[0097] Figure 5 This is a comparison diagram of the common-mode leakage current of the device and method proposed in this invention with that of conventional carrier comparison PWM. By adopting the zero common-mode modulation method proposed in this invention, the common-mode leakage current can be significantly reduced.

[0098] Figure 6 The diagram shows a comparison of the common-mode electromagnetic interference (EMI) of the device and method proposed in this invention with that of conventional carrier comparison PWM. By adopting the zero common-mode modulation method proposed in this invention, the EMI spikes of the switching frequency doubling are significantly suppressed by at least 20dB.

[0099] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A zero common-mode voltage modulation method, characterized in that, include: S1: Receive the reference voltages of the four bridge arms on the magnetic bearing controller using the voltage command calculation stage, and calculate the normalized differential-mode voltage command and common-mode voltage command. The differential voltage command includes: x The difference in voltage between the two windings in the direction and y The difference in voltage between the two windings in the direction The common-mode voltage command includes: x The sum of the voltages of the two windings in the direction ; ； ； ； in, , for x The reference voltage of the bridge arm connected to the two windings in the direction. , for y The reference voltage of the bridge arm connected to the two windings in the direction. The voltage at the star connection of the four windings. This is the DC bus voltage; S2: The sector number N is determined based on the differential mode voltage command using the sector determination step; S3: Using the action time calculation step, calculate the normalized action time of each voltage vector based on the sector number N, the differential mode voltage command, and the common mode voltage command; S4: The duty cycle allocation step calculates four duty cycles based on the normalized action time of each voltage vector, and then allocates the four duty cycles to the four bridge arms according to the sector number N to generate corresponding modulation signals. S5: The carrier comparison circuit compares the set carrier signal with the modulation signals of the four bridge arms to generate a PWM signal.

2. The zero common-mode voltage modulation method as described in claim 1, characterized in that, S2 includes: The sector determination process is controlled by utilizing The corresponding sector number N is used as the basis for judgment.

3. The zero common-mode voltage modulation method as described in claim 1, characterized in that, In S3: the normalized action time of each voltage vector includes: First differential vector action time , ; Second differential vector action time , ; Inverse common-mode vector action time , ; positive vector action time ; ; Four duty cycles The calculation formulas are as follows: ; ; ; .

4. The zero common-mode voltage modulation method as described in claim 3, characterized in that, In S4: a modulation signal is allocated to each bridge arm according to the sector number N and the four duty cycles, and the allocation principle is as follows: ； ； ； ； Among them, letters D This represents the bridge arm modulation signal. The first subscript indicates the bridge arm number, and the second subscript indicates the signal strength of the modulation signal, satisfying the following conditions: .

5. The zero common-mode voltage modulation method as described in claim 4, characterized in that, The carrier signal is a triangular carrier; in S5: For each bridge arm, when the carrier signal is greater than the first modulation signal And smaller than the second modulation signal When the signal is high, the output PWM signal is high; otherwise, the output PWM signal is low. The four PWM signals will be allocated accordingly. x The upper tube drive of the bridge arm connected by the two windings in the direction and y The lower tube drive of the bridge arm connected by the two windings in the direction.

6. A zero common-mode voltage modulation unit, characterized in that, A method for performing the zero common-mode voltage modulation method according to any one of claims 1-5 includes: The voltage command calculation stage receives reference voltages from the four bridge arms of the magnetic bearing controller and calculates normalized differential-mode voltage commands and common-mode voltage commands; the differential-mode voltage commands include: x The difference in voltage between the two windings in the direction and y The difference in voltage between the two windings in the direction The common-mode voltage command includes: x The sum of the voltages of the two windings in the direction ; The sector determination step is used to determine the sector number N based on the differential mode voltage command; The action time calculation step is used to calculate the normalized action time of each voltage vector based on the sector number N, the differential mode voltage command, and the common mode voltage command. The duty cycle allocation stage is used to calculate four duty cycles based on the normalized action time of each voltage vector, and then allocate the four duty cycles to the four bridge arms according to the sector number N to generate corresponding modulation signals. The carrier comparison stage is used to compare the set carrier signal with the modulation signals of the four bridge arms to generate a PWM signal.

7. A magnetic levitation bearing control device with common-mode interference suppression capability, characterized in that, include: A magnetic bearing drive converter, connected to a magnetic levitation bearing, is composed of power electronic devices and is used to amplify power according to a gate drive signal to drive the two-degree-of-freedom eight-pole magnetic levitation bearing. A displacement control unit, connected to the magnetic levitation bearing, is used to collect the displacement deviation signal of the magnetic levitation bearing and execute a position control algorithm to generate a current command value for the bearing winding. A current control unit, connected to the displacement control unit, is used to receive the current command value to acquire the actual current value and execute a current control algorithm to generate command voltages for the four bridge arms. A zero common-mode voltage modulation unit, connected to the current control unit and the connection, is used to receive command voltages for the four bridge arms and execute the zero common-mode voltage modulation method according to any one of claims 1-5, from generating a gate drive signal to the magnetic bearing drive converter.

8. The magnetic levitation bearing control device with common-mode interference suppression capability as described in claim 7, characterized in that, The magnetic bearing drive converter includes four switch bridge arms that share a DC bus, each connected to one end of one of the four windings of a two-degree-of-freedom eight-pole magnetic levitation bearing, and the other ends of the four windings are directly connected together.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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