Magnetic suspension bearing control system based on common follow current topology and magnetic suspension bearing system

Abstract

The invention discloses a magnetic suspension bearing control system based on common follow current topology and a magnetic suspension bearing system, and belongs to the field of magnetic suspension bearing control, and the magnetic suspension bearing control system comprises a plurality of groups of H bridges connected with windings in a one-to-one correspondence manner, and a current sensor and a control module which are mounted on a direct current bus side; the upper and lower ends of each bridge arm are respectively connected with the positive and negative electrodes of a direct current bus, and the upper or lower ends of the front and rear bridge arms in the same group of H bridges are respectively connected with the two ends of a current sensor; the control module is used for sequentially selecting one winding as a target winding in turn in each switching period, controlling the front bridge arm upper tube connected with the target winding to be switched on and the rear bridge arm lower tube to be switched off, and controlling the front bridge arm upper tubes connected with the other windings to be switched off and the rear bridge arm lower tubes to be switched on so as to measure the current of the target winding; and predicting the current of the other windings through a current model prediction control algorithm, generating PWM waves of the switching tubes, and applying the PWM waves to the corresponding switching tubes. According to the invention, the influence of winding current ripples on current sampling values can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of magnetic bearing control, and more specifically, relates to a magnetic bearing control system and a magnetic bearing system based on a common freewheeling topology. Background Art

[0002] Magnetic bearings refer to the use of electromagnetic force generated by the stator to suspend the motor rotor. Because it avoids mechanical contact between the rotor and the stator, it greatly reduces mechanical losses and becomes one of the best solutions for high-speed rotating mechanical support. Compared with traditional mechanical bearings, magnetic bearings have significant advantages such as no friction, low noise, long life, no need for lubrication, and good sealing. Therefore, they are widely used in aerospace, energy storage flywheels, turbine machinery, impeller machinery and other industrial fields. With the continuous in-depth research of domestic and foreign experts and scholars in the field of magnetic bearings, its related technologies have become more and more mature, making outstanding contributions to the progress of my country's high-end equipment manufacturing industry and having broad development prospects.

[0003] Magnetic bearings can be divided into active, passive and hybrid types according to the way electromagnetic force is generated. Active magnetic bearings have low cost and wide application range, and have become a hot topic in the field of magnetic bearings in recent years. Active magnetic bearings include key components such as magnetic bearing body, protective bearing, displacement sensor, controller, etc. The design of the controller directly determines the performance of the magnetic bearing system. The controller is mainly composed of a power amplifier and a control board.

[0004] In the traditional magnetic bearing control system, current sensors with the same number as the windings are required to obtain the winding current in order to achieve complete control of each degree of freedom of the rotor, which greatly increases the volume and cost of the controller and is not conducive to the further integration of the controller. In response to this problem, in the patent document with application publication number CN118462717A, a magnetic bearing control scheme with a single current sensor is disclosed. The scheme combines the current sampling result of the current sensor with the current model predictive control algorithm, and reduces the number of current sensors to the greatest extent while effectively realizing the control of the magnetic bearing, reduces the control cost, and improves the integration. However, under the topological structure proposed by the scheme, in order to use the current sensor to measure the current of the target winding, it is necessary to control the target winding to be in a state where the winding current rises rapidly and the remaining windings are in a freewheeling state. Since the winding coil has an inductive characteristic, when the current changes rapidly, the winding inductance will cause the current waveform to be distorted. Especially in a system with a high switching frequency, the current waveform will be affected by the transient effect caused by the switching action, resulting in a large current ripple, which ultimately affects the accuracy of the target winding current measured by the current sensor, and thus affects the control accuracy of the magnetic bearing. Summary of the invention

[0005] In view of the defects of the prior art and the need for improvement, the present invention provides a magnetic bearing control system and a magnetic bearing system based on a common freewheeling topology, which aims to improve the winding current ripple during the current sensor sampling process, thereby improving the accuracy of the winding current measured by the current sensor and improving the control accuracy of the magnetic bearing.

[0006] To achieve the above object, according to one aspect of the present invention, a magnetic bearing control system based on a common freewheeling topology is provided, wherein the magnetic bearing has N degrees of freedom and includes 2N windings for controlling the N degrees of freedom, where N is a positive integer; the magnetic bearing control system includes: 2N groups of H bridges corresponding to the 2N windings, a current sensor installed on the positive side of a DC bus, and a control module;

[0007] In each group of H-bridges, the upper tube of the front bridge arm is an insulated gate bipolar transistor, and the lower tube is a power diode; the upper tube of the rear bridge arm is a power diode, and the lower tube is an insulated gate bipolar transistor; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of the DC bus, and in the same group of H-bridges, the upper ends of the front and rear bridge arms are respectively connected to the two ends of the current sensor; the midpoints of the front and rear bridge arms of each group of H-bridges are respectively connected to the two ends of the corresponding winding;

[0008] The control module is used to execute the magnetic bearing control method, including: in each switching cycle, one winding is selected as the target winding in turn, and the following steps are executed:

[0009] S1: At the initial moment of the current switching cycle, the upper tube of the front bridge arm connected to the target winding is controlled to be turned on and the lower tube of the rear bridge arm is turned off, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned off and the lower tube of the rear bridge arm is turned on, so as to measure the current of the target winding using a current sensor;

[0010] S2: predicting the current of each winding other than the target winding in the current switching cycle through a current model predictive control algorithm;

[0011] S3: With the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the on and off of each insulated gate bipolar transistor is generated and applied to the corresponding insulated gate bipolar transistor to complete the control of the current switching cycle.

[0012] Furthermore, in step S2, the current model used by the current model predictive control algorithm is:

[0013]

[0014] Where w represents the winding, i w (k) and i w(k+1) represents the current of winding w in the kth cycle and the k+1th switching cycle respectively; T s is the switching cycle length, R is the winding resistance, L w is the inductance of winding w, V dc is the DC bus voltage, U s is the pipe pressure drop.

[0015] Further, in step S3, with the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the turning on and off of each insulated gate bipolar transistor is generated, including:

[0016] S31: Calculate the modulation ratio of each winding in the current switching cycle with the goal of making the current of each winding in the next switching cycle equal to the current command value;

[0017] S32: Calculate the duty cycle of the PWM wave of each insulated gate bipolar transistor in the H-bridge to which each winding is connected according to the modulation ratio to determine the PWM wave used to control the on and off of each insulated gate bipolar transistor.

[0018] Further, if the current switching cycle is the kth switching cycle, then in step S31, for any winding w, its modulation ratio in the current switching cycle is:

[0019]

[0020] Among them, d w (k) represents the modulation ratio of winding w in the current switching cycle, i ref (k) represents the current command value of winding w in the current switching cycle.

[0021] According to another aspect of the present invention, another magnetic bearing control system based on a common freewheeling topology is provided, wherein the magnetic bearing has N degrees of freedom and includes 2N windings for controlling the N degrees of freedom, where N is a positive integer; the magnetic bearing control system includes: 2N groups of H bridges corresponding to the 2N windings, a current sensor installed on the negative side of a DC bus, and a control module;

[0022] In each group of H-bridges, the upper tube of the front bridge arm is an insulated gate bipolar transistor, and the lower tube is a power diode; the upper tube of the rear bridge arm is a power diode, and the lower tube is an insulated gate bipolar transistor; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of the DC bus, and in the same group of H-bridges, the lower ends of the front and rear bridge arms are respectively connected to the two ends of the current sensor; the midpoints of the front and rear bridge arms of each group of H-bridges are respectively connected to the two ends of the corresponding winding;

[0023] The control module is used to execute the magnetic bearing control method, including: in each switching cycle, one winding is selected as the target winding in turn, and the following steps are executed:

[0024] T1: At the initial moment of the current switching cycle, the upper tube of the front bridge arm connected to the target winding is controlled to be turned off and the lower tube of the rear bridge arm is controlled to be turned on, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned on and the lower tube of the rear bridge arm is controlled to be turned off, so as to measure the current of the target winding using the current sensor;

[0025] T2: predict the current of the remaining windings in the current switching cycle by using the current model predictive control algorithm;

[0026] T3: With the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave is generated to control the on and off of each insulated gate bipolar transistor, and applied to the corresponding insulated gate bipolar transistor to complete the control of the current switching cycle.

[0027] Furthermore, in step T2, the current model used by the current model predictive control algorithm is:

[0028]

[0029] Where w represents the winding, i w (k) and i w (k+1) represents the current of winding w in the kth cycle and the k+1th switching cycle respectively; T s is the switching cycle length, R is the winding resistance, L w is the inductance of winding w, V dc is the DC bus voltage, U s is the pipe pressure drop.

[0030] Further, in step T3, with the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the turning on and off of each insulated gate bipolar transistor is generated, including:

[0031] T31: Calculate the modulation ratio of each winding in the current switching cycle with the goal of making the current of each winding in the next switching cycle equal to the current command value;

[0032] T32: Calculate the duty cycle of the PWM wave of each insulated gate bipolar transistor in the H-bridge connected to each winding according to the modulation ratio to determine the PWM wave used to control the on and off of each insulated gate bipolar transistor.

[0033] Further, if the current switching cycle is the kth switching cycle, then in step T31, for any winding w, its modulation ratio in the current switching cycle is:

[0034]

[0035] Among them, d w (k) represents the modulation ratio of winding w in the current switching cycle, i ref (k) represents the current command value of winding w in the current switching cycle.

[0036] According to another aspect of the present invention, there is provided a magnetic bearing system, comprising:

[0037] Magnetic bearings;

[0038] And any one of the above-mentioned magnetic bearing control systems based on the common freewheeling topology provided by the present invention.

[0039] Through the above technical scheme conceived by the present invention, by controlling the on and off of the insulated gate bipolar transistor in the H-bridge, the current in the winding connected to the H-bridge can be in different states, and the present invention improves the topological structure so that when the winding current of each winding is in one of the freewheeling states, the current sensor is located on the freewheeling circuit, so that the freewheeling circuit of each winding in the freewheeling state has a common freewheeling circuit branch.

[0040] When the current sensor is installed on the positive side of the DC bus, the switch status of each H-bridge and the corresponding winding current status are as follows:

[0041] When the upper tube of the front bridge arm is turned on and the lower tube of the rear bridge arm is turned off in the H bridge, the winding current of the connected winding is in the freewheeling state of the common freewheeling circuit, and the winding current will flow through the current sensor;

[0042] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned on in the H bridge, the current of the connected winding is in the freewheeling state of the non-common freewheeling circuit;

[0043] When the upper tube of the front bridge arm and the lower tube of the rear bridge arm in the H bridge are turned on, the current of the connected winding is in a rapidly increasing state;

[0044] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned off in the H-bridge, the current of the connected winding is in a rapidly decreasing state.

[0045] When the current sensor is installed on the negative side of the DC bus, the switch status of each H-bridge and the corresponding winding current status are as follows:

[0046] When the upper tube of the front bridge arm is turned on and the lower tube of the rear bridge arm is turned off in the H bridge, the winding current of the connected winding is in the freewheeling state of the non-common freewheeling circuit;

[0047] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned on in the H bridge, the current of the connected winding is in the freewheeling state of the common freewheeling circuit, and the winding current will flow through the current sensor;

[0048] When the upper tube of the front bridge arm and the lower tube of the rear bridge arm in the H bridge are turned on, the current of the connected winding is in a rapidly increasing state;

[0049] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned off in the H-bridge, the current of the connected winding is in a rapidly decreasing state.

[0050] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0051] The present invention includes a single current sensor, which is used to measure the current of each winding in turn, and at the same time, the current model prediction control algorithm is used to predict the current of the remaining windings other than the target winding, thereby ensuring the update frequency and accuracy of the winding current, and ultimately reducing the number of current sensors to the greatest extent while effectively realizing the control of the magnetic suspension bearing, reducing the control cost, and improving the integration. On this basis, when the present invention uses the current sensor to measure the current of the target winding, the winding current is in a freewheeling state, in which the current is relatively stable, and the inductance characteristics of the winding coil have little effect on the current waveform. Therefore, the present invention can significantly improve the effect of the current ripple on the target winding current sampling value, improve the measurement accuracy of the target winding current, and thus improve the control accuracy of the magnetic suspension winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of a magnetic bearing control system based on a common freewheeling topology provided in Embodiment 1 of the present invention;

[0053] Figure 2 A schematic diagram of the change of the voltage across each winding in a sampling cycle provided in Embodiment 1 of the present invention;

[0054] Figure 3 A schematic diagram of a magnetic bearing control system based on a common freewheeling topology provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0056] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0057] In order to solve the problem of large ripple in sampling results of the existing active magnetic bearing control system based on a single current sensor, the present invention provides a magnetic bearing control system and a magnetic bearing system based on a common freewheeling topology, the overall concept of which is: only a single current sensor is set, and the current sensor is used to measure the current of each winding in the magnetic bearing in sequence and in turn in each switching cycle, and at the same time, the switching signal of each switch tube is obtained by using a current prediction model control algorithm and a PWM modulation strategy to reduce the number of current sensors, reduce control costs, and improve integration; on this basis, the topological structure is improved so that the current sensor is located on a freewheeling loop of each winding to form a common freewheeling topology between the windings, so that the current sensor can be used to detect the winding current when the winding current is in the freewheeling state. Compared with the existing magnetic bearing control system based on a single current sensor, the problem of large fluctuations in sampling values ​​is solved, the sampling accuracy is improved, and the control accuracy of the magnetic bearing is thereby improved.

[0058] The magnetic bearing control system provided by the present invention can be applied to magnetic bearings with any degree of freedom. Without loss of generality, in the following embodiments, a 5-degree-of-freedom magnetic bearing is used as an example for explanation. The 5 degrees of freedom in the 5-degree-of-freedom magnetic bearing specifically refer to 4 degrees of freedom in the radial direction and one degree of freedom in the axial direction. Each degree of freedom is controlled by two windings, and there are a total of 10 windings. For ease of description, the 10 windings used to control the 5 degrees of freedom are respectively recorded as A1, A2, A3, A4, A5, B1, B2, B3, B4, and B5, where windings An and Bn are a pair of windings used to control the nth degree of freedom, n∈{1,2,3,4,5}.

[0059] The following are examples.

[0060] Embodiment 1:

[0061] A magnetic bearing control system based on a common freewheeling topology. The magnetic bearing involved in this embodiment has five degrees of freedom and includes ten windings for controlling the five degrees of freedom.

[0062] like Figure 1 As shown, the magnetic bearing control system provided in this embodiment includes: 10 groups of H bridges corresponding to 10 windings, a current sensor installed on the positive side of the DC bus, and a control module;

[0063] In each group of H-bridges, the upper tube of the front bridge arm is an insulated gate bipolar transistor, and the lower tube is a power diode; the upper tube of the rear bridge arm is a power diode, and the lower tube is an insulated gate bipolar transistor; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of the DC bus, and in the same group of H-bridges, the upper ends of the front and rear bridge arms are respectively connected to the two ends of the current sensor; the midpoints of the front and rear bridge arms of each group of H-bridges are respectively connected to the two ends of the corresponding winding.

[0064] Optionally, in this embodiment, the current sensor provided on the positive side of the DC bus is a Hall current sensor.

[0065] The magnetic bearing control system based on the common freewheeling topology provided in this embodiment is provided with a single current sensor installed on the positive side of the DC bus, and the upper and lower ends of each bridge arm are respectively connected to the positive and negative electrodes of the DC bus, and the upper ends of the front and rear bridge arms in the same H-bridge are respectively connected to the two ends of the current sensor. Based on this topological structure, this embodiment can control the on and off of the insulated gate bipolar transistor in the H-bridge to make the current in the winding connected to the H-bridge in the following different states:

[0066] When the upper tube of the front bridge arm is turned on and the lower tube of the rear bridge arm is turned off in the H bridge, the winding current of the connected winding is in the freewheeling state; at this time, the current sensor is located on the freewheeling loop, and the winding current will flow through the current sensor. This state is specifically called the common freewheeling loop freewheeling state;

[0067] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned on in the H bridge, the winding current of the connected winding is in a freewheeling state; at this time, the freewheeling circuit of the winding current is independent of the freewheeling circuits of the other windings, and this state is specifically called a non-common freewheeling circuit freewheeling state;

[0068] When the upper tube of the front bridge arm is turned on and the lower tube of the rear bridge arm is turned on in the H bridge, the winding current of the connected winding is in a rapidly increasing state;

[0069] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned off in the H bridge, the winding current of the connected winding is in a rapidly decreasing state.

[0070] Based on the above topological structure, in this embodiment, the control module is used to execute the magnetic bearing control method, including: in each switching cycle, one winding is selected in turn as the target winding, and the following steps are executed:

[0071] S1: At the initial moment of the current switching cycle, the upper tube of the front bridge arm connected to the target winding is controlled to be turned on and the lower tube of the rear bridge arm is turned off, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned off and the lower tube of the rear bridge arm is turned on, so as to measure the current of the target winding using a current sensor;

[0072] In step S1 of this embodiment, the upper tube of the front bridge arm connected to the target winding is controlled to be turned on and the lower tube of the rear bridge arm is turned off, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned off and the lower tube of the rear bridge arm is turned on, so that the target winding is in a freewheeling state of a common freewheeling circuit, and its current will flow through the current sensor. At the same time, the remaining windings outside the target winding are in a freewheeling state of a non-common freewheeling circuit, and the winding current will not flow through the current sensor. Therefore, the current sensor can be used to sample the current of the target winding to achieve measurement of the target winding current;

[0073] S2: predicting the current of each winding other than the target winding in the current switching cycle through a current model predictive control algorithm;

[0074] Optionally, in step S2 of this embodiment, the current model adopted by the current model predictive control algorithm is:

[0075]

[0076] Where w represents the winding, i w (k) and i w (k+1) represents the current of winding w in the kth cycle and the k+1th switching cycle respectively; T s is the switching cycle length, R is the winding resistance, L w is the inductance of winding w, V dc is the DC bus voltage, U s is the pipe pressure drop;

[0077] S3: With the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the on and off of each insulated gate bipolar transistor is generated and applied to the corresponding insulated gate bipolar transistor to complete the control of the current switching cycle;

[0078] Optionally, in step S3 of this embodiment, with the goal of making the current of each winding in the next switching cycle equal to the current command value, generating a PWM wave for controlling the turning on and off of each insulated gate bipolar transistor includes:

[0079] S31: Calculate the modulation ratio of each winding in the current switching cycle with the goal of making the current of each winding in the next switching cycle equal to the current command value;

[0080] If the current switching cycle is the kth switching cycle, then in step S31, for any winding w, its modulation ratio in the current switching cycle is:

[0081]

[0082] Among them, d w (k) represents the modulation ratio of winding w in the current switching cycle, iref (k) represents the current command value of winding w in the current switching cycle;

[0083] S32: Calculate the duty cycle of the PWM wave of each insulated gate bipolar transistor in the H-bridge to which each winding is connected according to the modulation ratio to determine the PWM wave used to control the on and off of each insulated gate bipolar transistor.

[0084] Based on the above-mentioned magnetic bearing control method executed by the control module, this embodiment selects a winding as the target winding in each control cycle, and measures the current of the target winding when the target winding is in the freewheeling state of the common freewheeling circuit and the remaining windings are in the freewheeling state of the non-common freewheeling circuit. At the same time, the current of the remaining windings is predicted based on the current model prediction control algorithm. Therefore, after every 10 switching cycles, the current sensor will measure the current of each winding once, completing a complete sampling cycle. In a complete sampling cycle, the current waveform of each winding is as follows: Figure 2 As shown, where T s Represents the switching cycle. Figure 2 It can be seen from the current waveform shown that in each switching cycle, when the target winding is sampled for current, the target winding is in a freewheeling state, the voltage across it is low (usually 0), the current is relatively stable, and the current ripple caused by the inductance effect of the winding coil is small. Therefore, the influence of the current ripple on the current sampling value can be significantly improved, and the accuracy of the target winding current sampling value can be improved, thereby effectively improving the overall control accuracy.

[0085] Optionally, in this embodiment, the control module is implemented by using a DSP control board and a driving module with the same number of insulated gate bipolar transistors; the DSP control board has a corresponding sampling channel connected to the current sensor for sampling the current output by the current sensor at the initial moment of the switching cycle. Optionally, in this embodiment, the sampling time is set within 100ns; after the sampling is completed, the sampled value will be held by the zero-order holder in the DSP control board until the end of the current switching cycle. In each switching cycle, the DSP control board outputs 20 PWM waves corresponding to the 20 insulated gate bipolar transistors in 10 groups of H bridges based on the above control method, that is, Figure 1 In PWM1~PWM20, each PWM wave is amplified by the driving module and applied to the corresponding insulated gate bipolar transistor to complete the control within the corresponding switching cycle.

[0086] Embodiment 2:

[0087] A magnetic bearing control system based on a common freewheeling topology. The magnetic bearing involved in this embodiment has five degrees of freedom and includes ten windings for controlling the five degrees of freedom.

[0088] like Figure 3 As shown, this embodiment is similar to the above-mentioned embodiment 1, and includes: 10 groups of H bridges corresponding to 10 windings one by one, a current sensor, and a control module;

[0089] In each group of H-bridges, the upper tube of the front bridge arm is an insulated gate bipolar transistor, and the lower tube is a power diode; the upper tube of the rear bridge arm is a power diode, and the lower tube is an insulated gate bipolar transistor; the midpoints of the front and rear bridge arms of each group of H-bridges are respectively connected to the two ends of the corresponding winding.

[0090] like Figure 3 As shown, the difference between this embodiment and the above-mentioned embodiment 1 is that, in this embodiment, the current sensor is installed on the negative side of the DC bus; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of the DC bus, and in the same group of H bridges, the lower ends of the front and rear bridge arms are respectively connected to the two ends of the current sensor.

[0091] Based on the above topological structure, this embodiment can make the current in the winding connected to the H bridge in the following different states by controlling the on and off of the insulated gate bipolar transistors in the H bridge:

[0092] When the upper tube of the front bridge arm is turned on and the lower tube of the rear bridge arm is turned off in the H bridge, the winding current of the connected winding is in the freewheeling state; at this time, the freewheeling circuit of the winding current is independent of the freewheeling circuits of the other windings, and this state is specifically called the non-common freewheeling circuit freewheeling state;

[0093] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned on in the H bridge, the winding current of the connected winding is in the freewheeling state; at this time, the current sensor is located on the freewheeling loop, and the winding current will flow through the current sensor. This state is specifically called the common freewheeling loop freewheeling state;

[0094] When the upper tube of the front bridge arm is turned on and the lower tube of the rear bridge arm is turned on in the H bridge, the winding current of the connected winding is in a rapidly increasing state;

[0095] When the upper tube of the front bridge arm is turned off and the lower tube of the rear bridge arm is turned off in the H bridge, the winding current of the connected winding is in a rapidly decreasing state.

[0096] In this embodiment, the control module is used to execute the magnetic bearing control method, including: in each switching cycle, one winding is selected in turn as the target winding, and the following steps are performed:

[0097] T1: At the initial moment of the current switching cycle, the upper tube of the front bridge arm connected to the target winding is controlled to be turned off and the lower tube of the rear bridge arm is controlled to be turned on, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned on and the lower tube of the rear bridge arm is controlled to be turned off, so as to measure the current of the target winding using the current sensor;

[0098] In step T1 of this embodiment, the upper tube of the front bridge arm connected to the target winding is turned off and the lower tube of the rear bridge arm is turned on, and the upper tube of the front bridge arm connected to the remaining windings is turned on and the lower tube of the rear bridge arm is turned off, so that the target winding is in a freewheeling state of a common freewheeling circuit, and its current will flow through the current sensor. At the same time, the remaining windings outside the target winding are in a freewheeling state of a non-common freewheeling circuit, and the winding current will not flow through the current sensor. Therefore, the current sensor can be used to sample the current of the target winding to achieve measurement of the target winding current;

[0099] T2: predict the current of the remaining windings in the current switching cycle by using the current model predictive control algorithm;

[0100] Optionally, in step T2 of this embodiment, the current model adopted by the current model predictive control algorithm is:

[0101]

[0102] Where w represents the winding, i w (k) and i w (k+1) represents the current of winding w in the kth cycle and the k+1th switching cycle respectively; T s is the switching cycle length, R is the winding resistance, L w is the inductance of winding w, V dc is the DC bus voltage, U s is the pipe pressure drop;

[0103] T3: With the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the on and off of each insulated gate bipolar transistor is generated and applied to the corresponding insulated gate bipolar transistor to complete the control of the current switching cycle;

[0104] Optionally, in step T3 of this embodiment, with the goal of making the current of each winding in the next switching cycle equal to the current command value, generating a PWM wave for controlling the turning on and off of each insulated gate bipolar transistor includes:

[0105] T31: Calculate the modulation ratio of each winding in the current switching cycle with the goal of making the current of each winding in the next switching cycle equal to the current command value;

[0106] If the current switching cycle is the kth switching cycle, then in step T31, for any winding w, its modulation ratio in the current switching cycle is:

[0107]

[0108] Among them, d w (k) represents the modulation ratio of winding w in the current switching cycle, iref (k) represents the current command value of winding w in the current switching cycle;

[0109] T32: Calculate the duty cycle of the PWM wave of each insulated gate bipolar transistor in the H-bridge connected to each winding according to the modulation ratio to determine the PWM wave used to control the on and off of each insulated gate bipolar transistor.

[0110] Similar to the above-mentioned embodiment 1, in this embodiment, when current sampling is performed on the target winding in each switching cycle, the target winding is in a freewheeling state, the current is relatively stable, and the current ripple generated by the inductance effect of the winding coil is small. Therefore, the influence of the current ripple on the current sampling value can be significantly improved, and the accuracy of the target winding current sampling value can be improved, thereby effectively improving the overall control accuracy.

[0111] Embodiment 3:

[0112] A magnetic bearing system, comprising:

[0113] Magnetic bearings;

[0114] And the magnetic bearing control system based on the common freewheeling topology provided in the above-mentioned embodiment 1 or 2.

[0115] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. A magnetic bearing control system based on a common freewheeling topology, wherein the magnetic bearing has N degrees of freedom and includes 2N windings for controlling the N degrees of freedom, where N is a positive integer; characterized in that: The magnetic bearing control system includes: 2N groups of H bridges corresponding to the 2N windings, a current sensor installed on the positive side of the DC bus, and a control module; In each group of H-bridges, the upper tube of the front bridge arm is an insulated gate bipolar transistor, and the lower tube is a power diode; the upper tube of the rear bridge arm is a power diode, and the lower tube is an insulated gate bipolar transistor; the upper and lower ends of each bridge arm are respectively connected to the positive and negative electrodes of the DC bus, and in the same group of H-bridges, the upper ends of the front and rear bridge arms are respectively connected to the two ends of the current sensor; the midpoints of the front and rear bridge arms of each group of H-bridges are respectively connected to the two ends of the corresponding winding; The control module is used to execute the magnetic bearing control method, including: in each switching cycle, one winding is selected in turn as the target winding, and the following steps are executed: S1: At the initial moment of the current switching cycle, the upper tube of the front bridge arm connected to the target winding is controlled to be turned on and the lower tube of the rear bridge arm is controlled to be turned off, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned off and the lower tube of the rear bridge arm is controlled to be turned on, so as to measure the current of the target winding by using the current sensor; S2: predicting the current of each winding other than the target winding in the current switching cycle by using a current model predictive control algorithm; S3: With the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the on and off of each insulated gate bipolar transistor is generated and applied to the corresponding insulated gate bipolar transistor to complete the control of the current switching cycle.

2. The magnetic bearing control system based on common freewheeling topology according to claim 1, characterized in that: In step S2, the current model used by the current model predictive control algorithm is: Where w represents the winding, i w (k) and i w (k+1) represents the current of winding w in the kth cycle and the k+1th switching cycle respectively; T s is the switching cycle length, R is the winding resistance, L w is the inductance of the winding w, V dc is the DC bus voltage, U s is the pipe pressure drop.

3. The magnetic bearing control system based on common freewheeling topology according to claim 2, characterized in that: In step S3, a PWM wave for controlling the on and off of each insulated gate bipolar transistor is generated with the goal of making the current of each winding in the next switching cycle equal to the current command value, including: S31: Calculate the modulation ratio of each winding in the current switching cycle with the goal of making the current of each winding in the next switching cycle equal to the current command value; S32: Calculate the duty cycle of the PWM wave of each insulated gate bipolar transistor in the H-bridge to which each winding is connected according to the modulation ratio to determine the PWM wave used to control the on and off of each insulated gate bipolar transistor.

4. The magnetic bearing control system based on common freewheeling topology according to claim 3, characterized in that: If the current switching cycle is the kth switching cycle, then in step S31, for any winding w, its modulation ratio in the current switching cycle is: Among them, d w (k) represents the modulation ratio of winding w in the current switching cycle, i ref (k) represents the current command value of winding w in the current switching cycle.

5. A magnetic bearing control system based on a common freewheeling topology, wherein the magnetic bearing has N degrees of freedom and includes 2N windings for controlling the N degrees of freedom, where N is a positive integer; characterized in that: The magnetic bearing control system includes: 2N groups of H bridges corresponding to the 2N windings, a current sensor installed on the negative side of the DC bus, and a control module; In each group of H-bridges, the upper tube of the front bridge arm is an insulated gate bipolar transistor, and the lower tube is a power diode; the upper tube of the rear bridge arm is a power diode, and the lower tube is an insulated gate bipolar transistor; the upper and lower ends of each bridge arm are respectively connected to the positive and negative electrodes of the DC bus, and in the same group of H-bridges, the lower ends of the front and rear bridge arms are respectively connected to the two ends of the current sensor; the midpoints of the front and rear bridge arms of each group of H-bridges are respectively connected to the two ends of the corresponding winding; The control module is used to execute the magnetic bearing control method, including: in each switching cycle, one winding is selected in turn as the target winding, and the following steps are executed: T1: at the initial moment of the current switching cycle, the upper tube of the front bridge arm connected to the target winding is controlled to be turned off and the lower tube of the rear bridge arm is controlled to be turned on, and the upper tube of the front bridge arm connected to the remaining windings is controlled to be turned on and the lower tube of the rear bridge arm is controlled to be turned off, so as to measure the current of the target winding by using the current sensor; T2: predicting the current of each winding other than the target winding in the current switching cycle through a current model predictive control algorithm; T3: With the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave is generated to control the on and off of each insulated gate bipolar transistor, and applied to the corresponding insulated gate bipolar transistor to complete the control of the current switching cycle.

6. The magnetic bearing control system based on common freewheeling topology according to claim 5, characterized in that: In step T2, the current model used by the current model predictive control algorithm is: Where w represents the winding, i w (k) and i w (k+1) represents the current of winding w in the kth cycle and the k+1th switching cycle respectively; T s is the switching cycle length, R is the winding resistance, L w is the inductance of the winding w, V dc is the DC bus voltage, U s is the pipe pressure drop.

7. The magnetic bearing control system based on common freewheeling topology according to claim 6, characterized in that: In step T3, with the goal of making the current of each winding in the next switching cycle equal to the current command value, a PWM wave for controlling the turning on and off of each insulated gate bipolar transistor is generated, including: T31: Calculate the modulation ratio of each winding in the current switching cycle with the goal of making the current of each winding in the next switching cycle equal to the current command value; T32: Calculate the duty cycle of the PWM wave of each insulated gate bipolar transistor in the H-bridge connected to each winding according to the modulation ratio to determine the PWM wave used to control the on and off of each insulated gate bipolar transistor.

8. The magnetic bearing control system based on common freewheeling topology according to claim 7, characterized in that: If the current switching cycle is the kth switching cycle, then in step T31, for any winding w, its modulation ratio in the current switching cycle is: Among them, d w (k) represents the modulation ratio of winding w in the current switching cycle, i ref (k) represents the current command value of winding w in the current switching cycle.

9. A magnetic bearing system, characterized in that: include: Magnetic bearings; And the magnetic bearing control system based on the common freewheeling topology as described in any one of claims 1-8.

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