Midpoint potential balance system based on multi-level magnetic suspension bearing driver

Abstract

The invention provides a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver, and belongs to the technical field of magnetic suspension bearing control, and the system comprises a three-level four-bridge-arm driver which comprises a switch bridge arm module and a capacitor bridge arm module which are connected in parallel and is used for obtaining winding current data, the neutral-point voltage balancing module is in communication connection with the current controller and is used for adjusting the voltage of the switch bridge arm module based on the voltage control signal so as to balance the neutral-point potential of the capacitor bridge arm module, and the neutral-point voltage balancing module is in communication connection with the current controller and is used for balancing the neutral-point potential of the capacitor bridge arm module based on the average voltage of the switch bridge arm module. The neutral-point voltage balancing module is used for balancing the neutral-point voltage to obtain zero-sequence voltage, the duty ratio updating module is in communication connection with the neutral-point voltage balancing module and is used for obtaining switching time based on the zero-sequence voltage and average voltage of the switching bridge arm module, and the modulation module is in communication connection with the duty ratio updating module and is used for receiving the switching time and obtaining a voltage control signal based on the switching time.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic suspension bearing control, and in particular to a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver. Background Art

[0002] As early as the 1940s, foreign scholars conducted in-depth research on magnetic bearings. Magnetic bearings are a bearing device that uses electromagnetic force to suspend the rotor, achieving contactless operation between the rotor and the stator. This allows no mechanical contact between the rotor and the stator, so that the rotor and the stator do not require lubrication, have good stability, long service life, and are pollution-free. Magnetic bearings have also gradually replaced traditional mechanical bearings and are generally used in technical fields such as energy storage flywheels and aviation equipment.

[0003] A magnetic bearing system can be formed by a rotor, a sensor, a controller and an electromagnetic actuator. The magnetic bearing control system determines the performance of the entire device. Generally, the power amplifier converts the control signal into the current in the winding to control the electromagnetic force of the magnetic bearing. The power amplifier is an important part of the magnetic bearing system.

[0004] At present, the power amplifier of magnetic bearings is mainly two-level. However, with the increase of the power level of the magnetic bearing system, the EMI problem of the system has become increasingly prominent. The electromagnetic interference generated by the power amplifier will affect the suspension accuracy and reliability of the magnetic bearing, thereby causing the midpoint potential of the magnetic bearing driver to be unbalanced. This is mainly because the electromagnetic interference generated by the power amplifier will affect the switching process of the magnetic bearing and will also be coupled to the position sensor of the magnetic bearing through the rotor. Summary of the invention

[0005] In view of this, it is necessary to provide a midpoint potential balancing system based on a multi-level magnetic levitation bearing driver to solve the technical problem in the prior art that the suspension accuracy and reliability of the magnetic levitation bearing driver are reduced due to electromagnetic interference generated by the power amplifier, thereby causing midpoint potential imbalance.

[0006] In order to solve the above technical problems, in a first aspect, the present invention provides a midpoint potential balancing system based on a multi-level magnetic suspension bearing drive, comprising: The three-level four-bridge-arm driver includes a switch bridge-arm module and a capacitor bridge-arm module connected in parallel, and is used to obtain winding current sampling data, and to adjust the voltage of the switch bridge-arm module based on a voltage control signal to balance the midpoint potential of the capacitor bridge-arm module; The current controller is used to receive the winding current sampling data, and obtain the average voltage of the switch bridge arm module based on the winding current sampling data; A midpoint voltage balancing module is connected to the current controller for obtaining a zero-sequence voltage based on an average voltage of the switch bridge arm module; A duty cycle update module is connected to the midpoint voltage balance module for receiving the zero-sequence voltage and the average voltage of the switch bridge module, and obtaining the switching time based on the zero-sequence voltage and the average voltage of the switch bridge module; The modulation module is connected to the duty cycle update module for receiving the switching time and obtaining the voltage control signal based on the switching time.

[0007] In a possible implementation, the switch bridge arm module includes: four half-bridge bridge arms and four winding units; The first half-bridge arm is electrically connected to one end of the first winding unit; The second half-bridge arm is electrically connected to one end of the second winding unit; The third half-bridge arm is electrically connected to one end of the third winding unit; The fourth half-bridge arm is electrically connected to one end of the fourth winding unit; The other end of the first winding unit is electrically connected to the other end of the second winding unit, the other end of the third winding unit, and the other end of the fourth winding unit.

[0008] In a possible implementation, the first half-bridge arm includes: a first switch device, a first unidirectional conductive device, a second switch device, and a second unidirectional conductive device; One end of the first switch device is electrically connected to one end of the second switch device and one end of the first unidirectional conductive device; The other end of the second switching device is electrically connected to one end of the second unidirectional conducting device.

[0009] In a possible implementation, the second half-bridge arm includes: a third switch device, a third unidirectional conductive device, a fourth switch device, and a fourth unidirectional conductive device; One end of the third switch device is electrically connected to one end of the fourth switch device and one end of the third unidirectional conductive device; The other end of the fourth switching device is electrically connected to one end of the fourth unidirectional conducting device.

[0010] In a possible implementation, the third half-bridge arm includes: a fifth switch device, a fifth unidirectional conductive device, a sixth switch device, and a sixth unidirectional conductive device; One end of the fifth unidirectional conductive device is electrically connected to one end of the fifth switching device; The other end of the fifth switching device is electrically connected to one end of the sixth switching device and one end of the sixth unidirectional conducting device.

[0011] In a possible implementation, the fourth half-bridge arm includes: a seventh switch device, a seventh unidirectional conductive device, an eighth switch device, and an eighth unidirectional conductive device; One end of the seventh unidirectional conducting device is electrically connected to one end of the seventh switching device; The other end of the seventh switching device is electrically connected to one end of the eighth switching device and one end of the eighth unidirectional conducting device.

[0012] In a possible implementation, the capacitor bridge arm module includes: a first capacitor and a second capacitor; One end of the first capacitor is electrically connected to the first switching device, the third switching device, the fifth unidirectional conductive device and the seventh unidirectional conductive device, the other end of the first capacitor is electrically connected to one end of the second capacitor, the other end of the first unidirectional conductive device, the other end of the third single-line conductive device, the other end of the sixth unidirectional conductive device and the other end of the eighth unidirectional conductive device, and the other end of the second capacitor is electrically connected to the other end of the second unidirectional conductive device, the other end of the fourth unidirectional conductive device, the other end of the sixth switching device and the other end of the eighth switching device.

[0013] In a possible implementation, the system further includes: a sampling module, which is communicatively connected to the three-level four-bridge-arm driver and is used to obtain winding current sampling data.

[0014] In a possible implementation, the system further includes: a driving circuit, electrically connected to the modulation module, configured to receive a voltage control signal generated by the modulation module, and generate a driving signal based on the voltage control signal; The three-level four-bridge-arm driver is also electrically connected to the driving circuit, and is used to receive a driving signal, and adjust the voltage of the switch bridge arm module based on the driving signal to promote the midpoint potential balance of the driver.

[0015] In a second aspect, the present invention further provides a midpoint potential balancing method based on a horizontal magnetic suspension bearing driver, the method comprising: The winding current sampling data is obtained through a three-level four-bridge arm driver; The average voltage of the switch bridge arm module is obtained based on the winding current sampling data through the current controller; The zero-sequence voltage is obtained based on the average voltage of the switch bridge arm module through the midpoint voltage balancing module; The switching time is obtained based on the zero-sequence voltage and the average voltage of the switch bridge arm module through the duty cycle update module; A voltage control signal is obtained based on the switching time through a modulation module; The voltage of the switch bridge arm module is adjusted based on the voltage control signal by the three-level four-bridge arm driver to make the midpoint potential of the capacitor bridge arm module balanced.

[0016] The beneficial effects of the present invention are as follows: the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver, a current controller, a midpoint voltage balancing module, a duty cycle updating module and a modulation module, wherein the three-level four-bridge arm driver further includes a switch bridge arm module and a capacitor bridge arm module. The present invention creatively proposes a switch bridge arm module, and controls the switch bridge arm module through a voltage control signal generated by the current controller, the midpoint voltage balancing module, the duty cycle updating module and the modulation module to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving midpoint potential balance of the capacitor bridge arm module. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A system structure diagram of an embodiment of a midpoint potential balancing system based on a multi-level magnetic bearing drive provided by the present invention; Figure 2 A flow chart of a midpoint potential balancing method of an embodiment of a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver provided by the present invention; Figure 3 A structural diagram of a three-level four-bridge-arm driver according to an embodiment of a midpoint potential balancing system based on a multi-level magnetic bearing driver provided by the present invention; Figure 4 A current loop control block diagram of a three-level four-bridge-arm driver of an embodiment of a midpoint potential balancing system based on a multi-level magnetic bearing driver provided by the present invention; Figure 5 A structural diagram of a driving circuit and a sampling module of an embodiment of a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver provided by the present invention; Figure 6 A schematic flow chart of an embodiment of a midpoint potential balancing method based on a multi-level magnetic suspension bearing driver provided by the present invention; Figure 7 A winding current control simulation diagram of an embodiment of a midpoint potential balancing method based on a multi-level magnetic bearing drive provided by the present invention; Figure 8 A midpoint potential control simulation diagram of an embodiment of a midpoint potential balancing method based on a multi-level magnetic suspension bearing driver provided by the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0019] In the description of the embodiments of the present invention, unless otherwise specified, "multiple" means two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone.

[0020] The descriptions of "first", "second", etc. involved in the embodiments of the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the technical features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0021] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] Before presenting the embodiments, the following terms are explained.

[0023] The present invention provides a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver, which is described below respectively.

[0024] Figure 1 A system structure diagram of an embodiment of a midpoint potential balancing system based on a multi-level magnetic bearing driver provided by the present invention includes: The three-level four-bridge-arm driver 110 includes a switch bridge arm module 101 and a capacitor bridge arm module 102 connected in parallel, and is used to obtain winding current sampling data, and adjust the voltage of the switch bridge arm module 101 based on a voltage control signal to make the midpoint potential of the capacitor bridge arm module 102 balanced; The current controller 120 is used to receive the winding current sampling data, and obtain the average voltage of the switch bridge arm module 101 based on the winding current sampling data; The midpoint voltage balancing module 130 is in communication with the current controller 120 and is used to obtain a zero-sequence voltage based on the average voltage of the switch bridge arm module 101; The duty cycle updating module 140 is in communication with the midpoint voltage balancing module 130, and is used to receive the zero-sequence voltage and the average voltage of the switch bridge arm module 101, and obtain the switching time based on the zero-sequence voltage and the average voltage of the switch bridge arm module 101; The modulation module 150 is in communication with the duty cycle update module 140 and is configured to receive the switching time and obtain a voltage control signal based on the switching time.

[0025] It should be noted that the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver 110, a current controller 120, a midpoint voltage balancing module 130, a duty cycle update module 140 and a modulation module 150. Among them, the three-level four-bridge arm driver 110 also includes a switch bridge arm module 101. The present invention creatively proposes a switch bridge arm module 101 and a capacitor bridge arm module 102. The voltage control signal generated by the current controller 120, the midpoint voltage balancing module 130, the duty cycle update module 140 and the modulation module 150 controls the switch bridge arm module to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving midpoint potential balance of the capacitor bridge arm module 102.

[0026] It should be further explained that, in each switching cycle, the sampling unit collects the current signals of the four windings of the NPC three-level four-arm driver 101 and sends them to the current controller 120, and calculates the average voltage command of each bridge arm midpoint in combination with the reference value; the midpoint voltage balancing module 130 collects the voltage difference between the upper and lower capacitors on the DC side and determines the zero-sequence voltage to be injected together with the winding current and the midpoint average voltage command; the duty cycle updating module 140 combines the initially calculated average voltage command of each bridge arm midpoint with the zero-sequence voltage to calculate the switching time, generates a modulation signal through the modulation module 150 and then outputs it, which is connected to each switch tube of each bridge arm in the NPC three-level four-arm driver 101 through the drive circuit.

[0027] Figure 2 A flow chart of a midpoint potential balancing method of an embodiment of a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver provided by the present invention comprises: four half-bridge arms and four winding units; The first half-bridge arm is electrically connected to one end of the first winding unit; The second half-bridge arm is electrically connected to one end of the second winding unit; The third half-bridge arm is electrically connected to one end of the third winding unit; The fourth half-bridge arm is electrically connected to one end of the fourth winding unit; The other end of the first winding unit is electrically connected to the other end of the second winding unit, the other end of the third winding unit, and the other end of the fourth winding unit.

[0028] It should be noted that the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver 110, a current controller 120, a midpoint voltage balancing module 130, a duty cycle update module 140 and a modulation module 150. Among them, the three-level four-bridge arm driver 110 also includes a switch bridge arm module 101 and a capacitor bridge arm module 102 connected in parallel. The present invention creatively proposes a switch bridge arm module 101, and controls the switch bridge arm module through the voltage control signal generated by the current controller 120, the midpoint voltage balancing module 130, the duty cycle update module 140 and the modulation module 150 to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving the midpoint potential balance of the capacitor bridge arm module 102.

[0029] Figure 3 A structural diagram of a three-level four-bridge-arm driver 101 of an embodiment of a midpoint potential balancing system based on a multi-level magnetic bearing driver provided by the present invention includes: A first switching device, a first unidirectional conducting device, a second switching device and a second unidirectional conducting device; One end of the first switch device is electrically connected to one end of the second switch device and one end of the first unidirectional conductive device; The other end of the second switching device is electrically connected to one end of the second unidirectional conducting device.

[0030] It should be noted that Figure 3 It is an NPC three-level four-bridge arm topology structure. The capacitor bridge arm consists of two capacitors connected in series, and the two ends are connected to the positive and negative ends of the DC power supply respectively. The midpoints of the two capacitors are used as the midpoint level ends. In addition, it includes 4 half-bridge bridge arms. The midpoint of each bridge arm is connected to one end of a winding, and the other ends of all windings are connected to the common node O. The four winding currents i1, i2, i3, and i4 respectively generate electromagnetic forces in the directions of two degrees of freedom of the magnetic bearing. i1 and i2 control one degree of freedom, and i3 and i4 control the other degree of freedom. Among them, i1+i2=i3+i4=2Ibias, Ibias is the magnetic bearing bias current, which is a constant value.

[0031] Preferably, i1 and i2 are arranged to flow out of the three-level bridge arm, and i3 and i4 are arranged to flow into the three-level bridge arm, so that the current flowing into and out of the common node O is the same.

[0032] Preferably, when the winding current flows out of the midpoint of the bridge arm, the first end of the first switching device is connected to the first end of the upper capacitor, the second end of the first switching device is connected to the first end of the second switching device and the first end of the first unidirectional conducting device, the second end of the second switching device is connected to the first end of the second unidirectional conducting device and connected to the winding as the midpoint of the bridge arm, the second end of the second unidirectional conducting device is connected to the second end of the lower capacitor, and the second end of the first unidirectional conducting device is connected to the midpoint level end; when the winding current flows into the midpoint of the bridge arm, the first end of the first unidirectional conducting device is connected to the first end of the upper capacitor, the second end of the first unidirectional conducting device is connected to the first end of the first switching device and connected to the winding as the midpoint of the bridge arm, the second end of the first switching device is connected to the first end of the second switching device and the second end of the second unidirectional conducting device, the second end of the second switching device is connected to the second end of the lower capacitor, and the first end of the second unidirectional conducting device is connected to the midpoint level end.

[0033] In some embodiments of the present invention, the second half-bridge arm includes: a third switch device, a third unidirectional conductive device, a fourth switch device and a fourth unidirectional conductive device; One end of the third switch device is electrically connected to one end of the fourth switch device and one end of the third unidirectional conductive device; The other end of the fourth switching device is electrically connected to one end of the fourth unidirectional conducting device.

[0034] It should be noted that the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver 110, a current controller 120, a midpoint voltage balancing module 130, a duty cycle update module 140 and a modulation module 150. Among them, the three-level four-bridge arm driver 110 also includes a switch bridge arm module 101 and a capacitor bridge arm module 102. The present invention creatively proposes a switch bridge arm module 101, and controls the switch bridge arm module through the voltage control signal generated by the current controller 120, the midpoint voltage balancing module 130, the duty cycle update module 140 and the modulation module 150 to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving the midpoint potential balance of the capacitor bridge arm module 102.

[0035] In some embodiments of the present invention, the third half-bridge arm includes: a fifth switch device, a fifth unidirectional conductive device, a sixth switch device and a sixth unidirectional conductive device; One end of the fifth unidirectional conductive device is electrically connected to one end of the fifth switching device; The other end of the fifth switching device is electrically connected to one end of the sixth switching device and one end of the sixth unidirectional conducting device.

[0036] It should be noted that the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver 110, a current controller 120, a midpoint voltage balancing module 130, a duty cycle update module 140 and a modulation module 150. Among them, the three-level four-bridge arm driver 110 also includes a switch bridge arm module 101 and a capacitor bridge arm module 102. The present invention creatively proposes a switch bridge arm module 101, and controls the switch bridge arm module through the voltage control signal generated by the current controller 120, the midpoint voltage balancing module 130, the duty cycle update module 140 and the modulation module 150 to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving the midpoint potential balance of the capacitor bridge arm module 102.

[0037] In some embodiments of the present invention, the fourth half-bridge arm includes: a seventh switch device, a seventh unidirectional conductive device, an eighth switch device and an eighth unidirectional conductive device; One end of the seventh unidirectional conducting device is electrically connected to one end of the seventh switching device; The other end of the seventh switching device is electrically connected to one end of the eighth switching device and one end of the eighth unidirectional conducting device.

[0038] It should be noted that the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver 110, a current controller 120, a midpoint voltage balancing module 130, a duty cycle update module 140 and a modulation module 150. Among them, the three-level four-bridge arm driver 110 also includes a switch bridge arm module 101 and a capacitor bridge arm module 102. The present invention creatively proposes a switch bridge arm module 101, and controls the switch bridge arm module through the voltage control signal generated by the current controller 120, the midpoint voltage balancing module 130, the duty cycle update module 140 and the modulation module 150 to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving the midpoint potential balance of the capacitor bridge arm module 102.

[0039] In some embodiments of the present invention, the three-level four-bridge-arm driver 110 comprises: a capacitor bridge-arm module, the capacitor bridge-arm module being connected in parallel with the switch bridge-arm module 101; The capacitor bridge arm module comprises: a first capacitor and a second capacitor; One end of the first capacitor is electrically connected to the first switching device, the third switching device, the fifth unidirectional conductive device and the seventh unidirectional conductive device, the other end of the first capacitor is electrically connected to one end of the second capacitor, the other end of the first unidirectional conductive device, the other end of the third single-line conductive device, the other end of the sixth unidirectional conductive device and the other end of the eighth unidirectional conductive device, and the other end of the second capacitor is electrically connected to the other end of the second unidirectional conductive device, the other end of the fourth unidirectional conductive device, the other end of the sixth switching device and the other end of the eighth switching device.

[0040] It should be noted that the midpoint potential balancing system based on the multi-level magnetic levitation bearing driver provided by the present invention is composed of a three-level four-bridge arm driver 110, a current controller 120, a midpoint voltage balancing module 130, a duty cycle update module 140 and a modulation module 150. Among them, the three-level four-bridge arm driver 110 also includes a switch bridge arm module 101 and a capacitor bridge arm module. The present invention creatively proposes a switch bridge arm module 101, and controls the switch bridge arm module through the voltage control signal generated by the current controller 120, the midpoint voltage balancing module 130, the duty cycle update module 140 and the modulation module 150 to achieve a three-level control effect, thereby increasing the number of current transformation steps, reducing current harmonics, and improving the control of the three-level four-bridge arm driver, thereby achieving the midpoint potential balance of the capacitor bridge arm module 102.

[0041] Figure 4 A current loop control block diagram of a three-level four-bridge-arm driver 101 of an embodiment of a midpoint potential balancing system based on a multi-level magnetic suspension bearing driver provided by the present invention and Figure 5 A structural diagram of a driving circuit and a sampling module of an embodiment of a midpoint potential balancing system based on a multi-level magnetic bearing driver provided by the present invention includes: The sampling module is connected to the three-level four-bridge-arm driver 110 for obtaining winding current sampling data.

[0042] It should be noted that the four winding currents are sampled and the common mode current Ic=i1+i2=i3+i4 and the differential mode current Id1=i1-i2, Id2=i3-i4 are calculated and fed back to the current controller for comparison with the reference value.

[0043] Preferably, the current controller is adjusted using a PI controller, and the common-mode voltage Uc=(u1+u2-u3-u4) / 2 and the differential-mode voltage instructions Ud1=u1-u2 and Ud2=u4-u3 are given, and converted into the average voltage instruction value of each bridge arm through the transformation matrix T, where u1, u2, u3, and u4 are the average mid-point voltage instructions of the four switch bridge arms.

[0044] Preferably, the transformation matrix T can be obtained according to the relationship between the common mode voltage and the average midpoint voltage of the bridge arm, The average midpoint voltage is added to the injected zero-sequence voltage d0 to obtain the final duty cycle command, which drives the switching device after carrier modulation.

[0045] Preferably, when the voltage difference between the upper capacitor and the lower capacitor is greater than zero, the zero-sequence voltage d0 takes a value in the range of (0, dmax); when the voltage difference between the upper capacitor and the lower capacitor is less than zero, the zero-sequence voltage d0 takes a value in the range of (-dmax, 0); dmax is the maximum duty cycle instruction without overmodulation.

[0046] In some embodiments of the present invention, the system further includes: a driving circuit electrically connected to the modulation module 150, configured to receive a voltage control signal generated by the modulation module 150, and to generate a driving signal based on the voltage control signal; The three-level four-bridge-arm driver 110 is also electrically connected to the driving circuit, and is used to receive a driving signal, and adjust the voltage of the switch bridge arm module 101 based on the driving signal to balance the midpoint potential of the driver.

[0047] It can be understood that the present invention uses 8 controllable switching devices to achieve the control of the two-degree-of-freedom magnetic bearing winding current, and can achieve a three-level control effect, which can increase the number of current transformation steps in the winding current control process, reduce current harmonics, improve the winding current control quality, and improve electromagnetic compatibility.

[0048] Figure 6 A schematic flow chart of an embodiment of a midpoint potential balancing method based on a multi-level magnetic bearing drive provided by the present invention, Figure 7 A winding current control simulation diagram of an embodiment of a midpoint potential balancing method based on a multi-level magnetic bearing drive provided by the present invention and Figure 8 A midpoint potential control simulation diagram of an embodiment of a midpoint potential balancing method based on a multi-level magnetic suspension bearing driver provided by the present invention includes: S601, obtaining winding current sampling data through a three-level four-bridge arm driver; S602, obtaining an average voltage of the switch bridge arm module based on winding current sampling data through a current controller; S603, obtaining a zero-sequence voltage based on an average voltage of the switch bridge arm module by a midpoint voltage balancing unit; S604, obtaining a switching time based on the zero-sequence voltage and the average voltage of the switch bridge arm module by a duty cycle updating unit; S605, obtaining a voltage control signal based on the switching time through a modulation unit; S606 , adjusting the voltage of the switch bridge arm module based on the voltage control signal through the three-level four-bridge arm driver to balance the midpoint potential of the capacitor bridge arm module.

[0049] The midpoint potential balancing system based on the multi-level magnetic bearing drive provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A midpoint potential balancing system based on a multi-level magnetic bearing drive, characterized in that: include: The three-level four-bridge-arm driver includes a switch bridge arm module and a capacitor bridge arm connected in parallel, and is used to obtain winding current sampling data, and to adjust the voltage of the switch bridge arm module based on a voltage control signal to balance the midpoint potential of the capacitor bridge arm module; The current controller is used to receive the winding current sampling data, and obtain the average voltage of the switch bridge arm module based on the winding current sampling data; A midpoint voltage balancing unit is connected in communication with the current controller and is used to obtain a zero-sequence voltage based on an average voltage of the switch bridge arm module; A duty cycle updating unit is connected to the midpoint voltage balancing unit for receiving the zero-sequence voltage and the average voltage of the switch bridge arm module, and obtaining the switching time based on the zero-sequence voltage and the average voltage of the switch bridge arm module; The modulation unit is connected to the duty cycle update unit for receiving the switching time and obtaining the voltage control signal based on the switching time.

2. The midpoint potential balancing system based on the multi-level magnetic bearing drive according to claim 1 is characterized in that: The switch bridge arm module includes: four half-bridge bridge arms and four winding units; The first half-bridge arm is electrically connected to one end of the first winding unit; The second half-bridge arm is electrically connected to one end of the second winding unit; The third half-bridge arm is electrically connected to one end of the third winding unit; The fourth half-bridge arm is electrically connected to one end of the fourth winding unit; The other end of the first winding unit is electrically connected to the other end of the second winding unit, the other end of the third winding unit, and the other end of the fourth winding unit.

3. The midpoint potential balancing system based on the multi-level magnetic bearing drive according to claim 2 is characterized in that: The first half-bridge arm comprises: a first switch device, a first unidirectional conductive device, a second switch device and a second unidirectional conductive device; One end of the first switch device is electrically connected to one end of the second switch device and one end of the first unidirectional conductive device; The other end of the second switching device is electrically connected to one end of the second unidirectional conducting device.

4. The midpoint potential balancing system based on the multi-level magnetic bearing drive according to claim 2 is characterized in that: The second half-bridge arm comprises: a third switch device, a third unidirectional conductive device, a fourth switch device and a fourth unidirectional conductive device; One end of the third switch device is electrically connected to one end of the fourth switch device and one end of the third unidirectional conductive device; The other end of the fourth switching device is electrically connected to one end of the fourth unidirectional conducting device.

5. The midpoint potential balancing system based on a multi-level magnetic bearing driver according to claim 2 is characterized in that: The third half-bridge arm comprises: a fifth switch device, a fifth unidirectional conductive device, a sixth switch device and a sixth unidirectional conductive device; One end of the fifth unidirectional conductive device is electrically connected to one end of the fifth switching device; The other end of the fifth switching device is electrically connected to one end of the sixth switching device and one end of the sixth unidirectional conducting device.

6. The midpoint potential balancing system based on a multi-level magnetic bearing driver according to claim 2 is characterized in that: The fourth half-bridge arm comprises: a seventh switch device, a seventh unidirectional conductive device, an eighth switch device and an eighth unidirectional conductive device; One end of the seventh unidirectional conducting device is electrically connected to one end of the seventh switching device; The other end of the seventh switching device is electrically connected to one end of the eighth switching device and one end of the eighth unidirectional conducting device.

7. The midpoint potential balancing system based on a multi-level magnetic bearing driver according to claim 1 is characterized in that: The capacitor bridge arm module comprises: a first capacitor and a second capacitor; One end of the first capacitor is electrically connected to the first switching device, the third switching device, the fifth unidirectional conductive device and the seventh unidirectional conductive device, the other end of the first capacitor is electrically connected to one end of the second capacitor, the other end of the first unidirectional conductive device, the other end of the third single-line conductive device, the other end of the sixth unidirectional conductive device and the other end of the eighth unidirectional conductive device, and the other end of the second capacitor is electrically connected to the other end of the second unidirectional conductive device, the other end of the fourth unidirectional conductive device, the other end of the sixth switching device and the other end of the eighth switching device.

8. The midpoint potential balancing system based on the horizontal magnetic bearing driver according to claim 1 is characterized in that: The system further comprises: a sampling module, which is communicatively connected with the three-level four-bridge arm driver and is used for acquiring winding current sampling data.

9. The midpoint potential balancing system based on the horizontal magnetic bearing driver according to claim 8 is characterized in that: The system further includes: a driving circuit electrically connected to the modulation module, configured to receive a voltage control signal generated by the modulation module, and to generate a driving signal based on the voltage control signal; The three-level four-bridge-arm driver is also electrically connected to the driving circuit, and is used to receive a driving signal, and adjust the voltage of the switch bridge arm module based on the driving signal to promote the midpoint potential balance of the driver.

10. A midpoint potential balancing method based on a horizontal magnetic suspension bearing driver, based on the midpoint potential balancing system based on a horizontal magnetic suspension bearing driver as claimed in any one of claims 1 to 9, characterized in that: The method comprises: The winding current sampling data is obtained through a three-level four-bridge arm driver; The average voltage of the switch bridge arm module is obtained based on the winding current sampling data through the current controller; The zero-sequence voltage is obtained based on the average voltage of the switch bridge arm module by the midpoint voltage balancing unit; Obtaining the switching time based on the zero-sequence voltage and the average voltage of the switch bridge arm module through the duty cycle updating unit; A voltage control signal is obtained based on the switching time by a modulation unit; The voltage of the switch bridge arm module is adjusted based on the voltage control signal by the three-level four-bridge arm driver to make the midpoint potential of the capacitor bridge arm module balanced.

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