Fault-tolerant transient control method and system for a magnetic bearing circuit, magnetic levitation device

Abstract

The application discloses a kind of fault-tolerant transient control method and system of magnetic suspension bearing circuit and magnetic suspension equipment, belong to magnetic suspension bearing control technical field.Therein, fault-tolerant transient control method includes: when circuit breaking fault occurs, the current of winding 1 and winding 2 between the non-common bridge arm group containing circuit breaking fault switch tube and common bridge arm is reversed;Wherein, the method of each step control current reversal includes: the duty cycle of common bridge arm switch tube is adjusted to D com When current needs to be adjusted from positive to negative, D com Satisfy the maximum value in duty cycle sequence {D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 1;When current needs to be adjusted from negative to positive, D com Satisfy the minimum value in duty cycle sequence {D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 0.Through the above method, the winding to be reversed can be modulated as much as possible following the ideal calculated modulation value u1, u2 without affecting the state of other windings that do not perform current reversal modulation, improving the controllability of overall modulation.

Description

Technical Field

[0001] This invention belongs to the field of magnetic levitation bearing control technology, and more specifically, relates to a fault-tolerant transient control method and system for magnetic levitation bearing circuits, and magnetic levitation equipment. Background Technology

[0002] Electromagnetic levitation technology is the best solution for high-speed rotating machinery, and its non-contact, wear-free, and lubrication-free characteristics have attracted widespread attention in many high-speed motor fields. With the continuous progress and development of science and technology, the performance of magnetic levitation bearings is constantly improving, and the integration of electronic components is also driving down their cost year by year. Therefore, in recent years, magnetic levitation bearing technology has received widespread attention from academia and industry.

[0003] For an electromagnetic levitation control system, the large number of switching devices increases the likelihood of open-circuit failures. In the field of high-speed rotating machinery, failure of the support components leading to rotor drop can result in irreversible accidents. Therefore, fault tolerance for switching device failures and ensuring that the high-speed rotor does not fall under power electronic fault-tolerant transients are of great value.

[0004] While existing solutions exist for fault-tolerant power electronic circuit breaker faults, such as the winding current reversal scheme described in patent CN202110372834.5, "Fault Location, Fault Tolerance Method and System for Winding Controller of Magnetic Bearing," the rotor displacement fluctuates significantly during fault-tolerant transients involving current reversal. There is even a high probability that the high-speed rotor will collide with the protective bearing. Furthermore, it can affect the modulation of other windings that do not require reversal, making the entire reversal process uncontrollable. Therefore, this places higher demands on the displacement fluctuations caused by fault-tolerant transients after power electronic faults. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a fault-tolerant transient control method and system for magnetic levitation bearing circuit and magnetic levitation equipment, the purpose of which is to improve the controllability of rotor fault-tolerant transient control.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a fault-tolerant transient control method for magnetic levitation bearing circuits is provided.

[0007] The magnetic levitation bearing circuit includes: a common bridge arm and N non-common bridge arm groups, each non-common bridge arm group corresponding to control one degree of freedom of the magnetic levitation bearing; each non-common bridge arm group includes two non-common bridge arms, and the common bridge arm and each non-common bridge arm include an upper switch tube connected to the positive terminal of the DC power supply and a lower switch tube connected to the negative terminal of the DC power supply; a winding is provided between the connection point of the upper and lower switch tubes of each non-common bridge arm and the connection point of the upper and lower switch tubes of the common bridge arm;

[0008] The fault-tolerant transient control method comprises: when a short-circuit fault occurs, controlling the current of winding 1 and winding 2 between the non-common bridge arm group containing the short-circuit fault switch tube and the common bridge arm to be reversed; wherein the method for controlling the current to be reversed at each step comprises: adjusting the duty cycle of the switch tube of the common bridge arm to D com adjusting the duty cycle of the switch tube of the non-common bridge arm i corresponding to winding i to D i , D 1= D com -A1u1, D 2= D com -A2u2; D k = D com +A k u k , k≠1, 2; when D 1 or D 2 is less than 0, directly taking 0, and greater than 1, directly taking 1; wherein,

[0009] defining that the winding current flowing from the non-common bridge arm into the common bridge arm is positive, and the winding current flowing from the common bridge arm into the non-common bridge arm is negative; when the current needs to be adjusted from positive to negative, D com satisfying that the maximum value of the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 1; when the current needs to be adjusted from negative to positive, D com satisfying that the minimum value of the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 0; wherein u i is the modulation wave of winding i calculated by the current loop, A i is the coefficient of winding i before reversal, if the current of winding i before reversal is positive, Ai =1; if the current of the reverse winding i is negative, A i =-1.

[0010] In one embodiment,

[0011] When the magnetic levitation bearing circuit is operating normally, the N non-common bridge arm groups are divided into two parts and the winding currents of the two non-common bridge arm groups are in opposite directions.

[0012] In one embodiment, when N is even, each part has N / 2 non-common arm components; when N is odd, one part has (N-1) / 2 non-common arm groups and the other part has (N+1) / 2 non-common arm groups.

[0013] In one embodiment, after the current in windings 1 and 2 between the non-common bridge arm group containing the circuit breaker switch and the common bridge arm is reversed, the method further includes:

[0014] Then control the winding current between any non-common bridge arm group and the common bridge arm in another part to reverse.

[0015] In one embodiment, the winding current is reversed in the next step only after the previous winding current has been reversed and the rotor's offset displacement in the corresponding degree of freedom has converged to less than the displacement threshold.

[0016] In one embodiment, when the magnetic levitation bearing circuit is operating normally, the duty cycle of the common bridge arm switch is 0.5.

[0017] In one embodiment, the fault-tolerant transient control method further includes:

[0018] The current of the windings of each non-common bridge arm group and the common bridge arm is collected, and the open circuit fault of the bridge arm switch tube in each non-common bridge arm group is determined according to the preset threshold.

[0019] According to a second aspect of the present invention, a fault-tolerant transient control system for a magnetic levitation bearing circuit is provided.

[0020] The magnetic levitation bearing circuit includes: a common bridge arm and N non-common bridge arm groups, each non-common bridge arm group corresponding to control one degree of freedom of the magnetic levitation bearing; each non-common bridge arm group includes two non-common bridge arms, and the common bridge arm and each non-common bridge arm include an upper switch tube connected to the positive terminal of the DC power supply and a lower switch tube connected to the negative terminal of the DC power supply; a winding is provided between the connection point of the upper and lower switch tubes of each non-common bridge arm and the connection point of the upper and lower switch tubes of the common bridge arm;

[0021] The fault-tolerant transient control system is used to perform: when a short-circuit fault occurs, control the current of winding 1 and winding 2 between the non-common bridge arm group containing the short-circuit fault switch tube and the common bridge arm to reverse; wherein, the method for controlling the current to reverse at each step comprises: adjusting the duty ratio of the switch tube of the non-common bridge arm i corresponding to winding i to D com , D i , D 1= D com -A1u1, D 2= D com -A2u2, D k = D com +A k u k , k≠1, 2; when D 1 or D 2 is less than 0, directly taking 0, and greater than 1, directly taking 1; wherein, the winding current flowing from the non-common bridge arm into the common bridge arm is defined as positive, and the winding current flowing from the common bridge arm into the non-common bridge arm is defined as negative; when the current needs to be adjusted from positive to negative, D com satisfies that the maximum value in the duty ratio sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 1; when the current needs to be adjusted from negative to positive, D com satisfies that the minimum value in the duty ratio sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 0; wherein, u i is the modulation wave of winding i calculated by the current loop, A i is the coefficient of winding i before reversing, if the current of winding i before reversing is positive, A i =1; if the current of winding i before reversing is negative, A i =-1.

[0022] In one embodiment, when the magnetic suspension bearing circuit is operating normally, the N non-common bridge arms are divided into two parts and the winding current directions of the two parts of non-common bridge arms are opposite;

[0023] The fault-tolerant transient control system also controls the winding current between any one of the non-common bridge arms in the other part and the common bridge arm to be reversed after controlling the winding 1 and winding 2 between the non-common bridge arm group containing the open-circuit fault switch tube and the common bridge arm to be reversed.

[0024] According to a third aspect of the present application, a magnetic suspension device is provided, comprising a magnetic suspension bearing, a magnetic suspension bearing circuit and the above-mentioned fault-tolerant transient control system for the magnetic suspension bearing circuit.

[0025] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0026] The fault-tolerant transient control method of the present application reverses the winding current between the corresponding non-common bridge arm and the common bridge arm when an open-circuit fault occurs, so as to restore the magnetic suspension bearing circuit to normal. When performing current reversal, the present application focuses on the adjustment of the modulation parameters of each bridge arm, and adjusts the duty cycle of the switch tube of the common bridge arm to D com The duty cycle of the switch tube of the non-common bridge arm i corresponding to the winding i is adjusted to D i When the current needs to be adjusted from positive to negative, the value of the duty cycle sequence is determined according to the maximum value in D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 1; when the current needs to be adjusted from negative to positive, the value of the duty cycle sequence is determined according to the minimum value in D com -A1u1, D com -A2u2, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} is 0. D comThe value of the modulation method can be obtained. By the above modulation method, the winding to be reversed can follow the ideal calculated modulation value u1, u2 as much as possible without affecting the state of other windings not subjected to current reverse modulation, thereby improving the controllability of the overall modulation. On this basis, increasing the modulation value u1, u2 can increase the potential difference between the two ends of the winding to be reversed, so that the winding to be reversed can quickly complete the current reversal in a short time, shorten the fault tolerance transient time, and reduce the displacement fluctuation during the fault tolerance transient, thereby making the entire magnetic suspension bearing device more safe and reliable.

[0027] Further, when the magnetic suspension bearing circuit is normally operated, the N non-common bridge arm groups are divided into two parts, and the winding current directions of the two parts of the non-common bridge arm groups are opposite, so as to ensure that the overall bridge arm current stress is small.

[0028] Further, when a circuit breaking fault occurs, the winding current between the non-common bridge arm group containing the circuit breaking fault switch tube and the common bridge arm is first controlled to be reversed, and then the winding current between any one of the non-common bridge arm groups in the other part and the common bridge arm is controlled to be reversed. Thus, it can be ensured that the overall bridge arm current stress is small after the fault tolerance transient control. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 FIG. 1 is a structural diagram of a single radial magnetic suspension bearing according to an embodiment;

[0030] Figure 2 FIG. 2 is a circuit diagram of a magnetic suspension bearing circuit according to an embodiment;

[0031] FIG. 3(a) is a schematic diagram of the maximum potential difference between the two ends of the winding i when the winding current is reversed from positive to negative, and the common bridge arm duty ratio is fixed at 0.5, according to an embodiment;

[0032] FIG. 3(b) is a schematic diagram of the maximum potential difference between the two ends of the winding i when the winding current is reversed from positive to negative, and the common bridge arm duty ratio is set to 1, according to an embodiment;

[0033] FIG. 3(c) is a schematic diagram of the maximum potential difference between the two ends of the winding i when the winding current is reversed from negative to positive, and the common bridge arm duty ratio is fixed at 0.5, according to an embodiment;

[0034] FIG. 3(d) is a schematic diagram of the maximum potential difference between the two ends of the winding i when the winding current is reversed from negative to positive, and the common bridge arm duty ratio is set to 0, according to an embodiment;

[0035] Figure 4 FIG. 4 is a step flow chart of a fault tolerance transient control method according to an embodiment;

[0036] Figure 5Fig. 6(a) is a schematic diagram of the relative relationship between the duty cycles of the common bridge arm and the non-common bridge arm when the common bridge arm duty cycle is 0.5 in an embodiment of the application when the current direction is changed from positive to negative;

[0037] Fig. 6(a) is a schematic diagram of the relative relationship between the duty cycles of the common bridge arm and the non-common bridge arm when the common bridge arm duty cycle is 0.5 in an embodiment of the application when the current direction is changed from positive to negative;

[0038] Fig. 6(b) is a schematic diagram of the relative relationship between the duty cycles of the common bridge arm and the non-common bridge arm after the whole of Fig. 6(a) is moved upward;

[0039] Fig. 7(a) is a schematic diagram of the relative relationship between the duty cycles of the common bridge arm and the non-common bridge arm when the common bridge arm duty cycle is 0.5 in an embodiment of the application when the current direction is changed from negative to positive;

[0040] Fig. 7(b) is a schematic diagram of the relative relationship between the duty cycles of the common bridge arm and the non-common bridge arm after the whole of Fig. 7(a) is moved downward;

[0041] Fig. 8(a) is a schematic diagram of step-by-step switching when the current direction of the magnetic bearing is reversed in an embodiment of the application;

[0042] Fig. 8(b) is a schematic diagram of the current flowing through the switch tube when the step-by-step switching of Fig. 8(a) is performed. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0044] As Figure 1 Fig. 1 is a schematic diagram of the structure of a single radial magnetic bearing in an embodiment of the application. The magnetic bearing has multiple control degrees of freedom, Figure 1 Fig. 1 shows two degrees of freedom in the x direction and the y direction, but is not limited thereto. The electromagnetic force in each degree of freedom is determined by two windings, for example, the electromagnetic force in the x direction is determined by the electromagnetic force generated by winding (i.e. bearing coil) A1 and the electromagnetic force generated by winding A2, and the electromagnetic force in the y direction is determined by the electromagnetic force generated by winding A3 and the electromagnetic force generated by winding A4. Each winding is connected to the magnetic bearing circuit, and the electromagnetic force generated by the winding is controlled by controlling the current of the magnetic bearing circuit.

[0045] As Figure 2The circuit diagram of the magnetic suspension bearing circuit in an embodiment is shown, which comprises a common bridge arm and N non-common bridge arm groups, each non-common bridge arm group corresponding to control of one degree of freedom of the magnetic suspension bearing; each non-common bridge arm group contains two non-common bridge arms, the common bridge arm and each non-common bridge arm contain an upper switch tube connected with the positive pole of a direct current power supply and a lower switch tube connected with the negative pole of the direct current power supply; the connection points of the upper and lower switch tubes of each non-common bridge arm are provided with windings between the connection points of the upper and lower switch tubes of the common bridge arm, and the windings are used for magnetic suspension control of the bearing. It should be noted that the current direction on each winding can not be limited, and the electromagnetic force can be generated regardless of the winding current direction.

[0046] The fault-tolerant transient control method comprises: when a circuit breaking fault occurs, the current of the windings 1 and 2 between the non-common bridge arm group containing the circuit breaking fault switch tube and the common bridge arm is reversed; wherein the method for controlling the current reversal at each step comprises: adjusting the duty ratio of the common bridge arm switch tube to D com adjusting the duty ratio of the switch tube of the non-common bridge arm i corresponding to the winding i to D i In the present application, the duty ratio of the common bridge arm switch tube is adjusted to D com and the duty ratio of the switch tube of each non-common bridge arm i is adjusted to D i The specific relationship needs to be met, which will be described in detail below.

[0047] Generally, if the current of the target winding is reversed, the potential difference between the two ends of the target winding is directly adjusted, the potential difference is increased, and the current reversal speed is increased. The duty ratio of the common bridge arm is denoted as D com The duty ratio of the non-common bridge arm i corresponding to the winding i is denoted as D i Under normal circumstances, D com Generally, it is 0.5. As shown in FIG. 3(a), if a fault occurs, the duty ratio of the non-common bridge arm i corresponding to the winding i when the current of the winding i is reversed from positive to negative is denoted as D i The common bridge arm duty ratio is always low, and the potential difference between the two ends of the winding is only 0.5 times the direct current bus voltage; while the common bridge arm duty ratio D com is adjusted to 0, the duty ratio of the non-common bridge arm i is D iis 1, the potential difference between the two ends of the winding can be 1 times the DC bus voltage, and the current can be quickly reversed, as shown in Fig. 3(b). As shown in Fig. 3(c), when the winding i current needs to be reversed from negative to positive under the condition that the duty ratio of the common bridge arm is always 0.5, the duty ratio of the non-common bridge arm i corresponding to the common bridge arm is denoted as D i is always high, and the potential difference between the two ends of the winding is only 0.5 times the DC bus voltage; and under the condition that the duty ratio of the common bridge arm is adjusted to 1, the duty ratio of the non-common bridge arm i is adjusted to 0, the potential difference between the two ends of the winding can be 1 times the DC bus voltage, and the current can be quickly reversed, as shown in Fig. 3(d). However, the above modulation method only adjusts the duty ratio of the common bridge arm according to the reversal of the target winding current, although the current of the target winding can be quickly reversed, the operation of other windings in the entire circuit that do not need to reverse the current will be affected due to the change of the duty ratio of the common bridge arm, and the overall modulation process is greatly affected. D com is adjusted to 0, the potential difference between the two ends of the winding can be 1 times the DC bus voltage, and the current can be quickly reversed, as shown in Fig. 3(d). However, the above modulation method only considers the reversal of the target winding current to adjust the duty ratio of the common bridge arm, although the current of the target winding can be quickly reversed, the operation of other windings in the entire circuit that do not need to reverse the current will be affected due to the change of the duty ratio of the common bridge arm, and the overall modulation process is greatly affected. D i is adjusted to 0, the potential difference between the two ends of the winding can be 1 times the DC bus voltage, and the current can be quickly reversed, as shown in Fig. 3(d). However, the above modulation method only considers the reversal of the target winding current to adjust the duty ratio of the common bridge arm, although the current of the target winding can be quickly reversed, the operation of other windings in the entire circuit that do not need to reverse the current will be affected due to the change of the duty ratio of the common bridge arm, and the overall modulation process is greatly affected.

[0048] Therefore, the present application proposes a new regulation method for modulation parameters when fault-tolerant transient control is performed, which can quickly reverse the target winding and does not affect the normal operation of other windings.

[0049] As shown in Fig. 3, the fault-tolerant transient control method comprises the following steps: Figure 4

[0050] locating the non-common bridge arm group to which the circuit breaking fault switch belongs, and determining the winding 1 and the winding 2 located between the non-common bridge arm group and the common bridge arm;

[0051] setting the duty ratio of the common bridge arm switch according to the current direction of the winding 1 and the winding 2 D com and the duty ratio of the switch of each non-common bridge arm i D i , D 1= D com -A1u1, D 2= D com -A2u2, D k = D com +A k u k , k≠1, 2, wherein,

[0052] when the current needs to be reversed from positive to negative, D com satisfies the duty ratio sequence D com ​- A1u1, D com - A2u2, D com + A3u3,..., D com + A 2N u 2N} is 1;

[0053] When the current needs to be adjusted from negative to positive, D com satisfies the duty cycle sequence { D com - A1u1, D com - A2u2, D com + A3u3,..., D com + A 2N u 2N} is 0.

[0054] Specifically, the modulation wave generated by the current feedback of each winding is {u1, u2,..., u 2N} through the optimization of the modulation process, each winding can be operated according to the above-mentioned modulation wave during the two winding current reverse periods. If the current direction of the i-th winding is from the non-common bridge arm to the common bridge arm (positive), denoted as A i = 1; if the current direction of the i-th winding is from the common bridge arm to the non-common bridge arm (negative), denoted as A i = -1. Normally, the common bridge arm duty cycle is generally set to 0.5, and the duty cycles of the 2N non-common bridge arms { D 1, D 2,..., D 2N} can be represented as {0.5 + A1u1, 0.5 + A2u2, 0.5 + A3u3,..., 0.5 + A 2N u 2N, under normal circumstances, control according to the duty cycle. In the detection of the need to implement the winding current reverse, it is assumed that the winding current reverse needs to be performed respectively winding 1 and winding 2, the winding current reverse is implemented by the controller generated modulation wave is u1, u2, it can be understood that the greater the value of u1, u2, the greater the potential difference between the corresponding winding, the faster the current reverse speed. Generally speaking, when the current is reversed, the modulation wave u1, u2 is set as large as possible (greater than 0 but not more than 1) to achieve the fastest reverse speed, which can be flexibly changed according to the actual situation, for example, it can be 0.6, 0.7, 0.8, 0.9, etc. In order to make the winding current reverse at a faster speed, the common bridge arm duty cycle can be adjusted to D com , it is assumed that the winding current reverse needs to be performed respectively winding 1 and winding 2, at this time, when the current is reversed, the duty cycle of the switch tube of the non-common bridge arm i corresponding to the winding i is adjusted to D i , D 1= D com -A1u1, D 2= D com -A2u2, D k = D com +A k u k , k≠1, 2, that is, when the current is reversed, the duty cycle sequence of the switch tube of the non-common bridge arm is { D com -A1u1, D com -A2u2, D com +A3u3,... D com +A 2N u 2N}. The sequence ensures that winding 1 and winding 2 can reverse the current and other windings will not reverse the current and other windings will operate according to the given modulation wave. At the same time, the value of the common bridge arm duty cycle D com is limited for forward and reverse current conditions to ensure that other windings operate without affecting the winding 1 and winding 2 to obtain a larger potential difference between the two ends, that is, the actual modulation wave of winding 1 and winding 2 follows or approaches the ideal calculation modulation wave u1, u2.

[0055] As Figure 5As shown, under normal circumstances, the duty cycle of the common bridge arm is 0.5, but other values ​​are also possible. Here, we take the commonly used 0.5 as an example, and the duty cycles of each non-common bridge arm are set to around 0.5.

[0056] As shown in Figure 6(a), when a fault occurs and it is necessary to reverse the current flow from the non-common bridge arm to the common bridge arm (positive direction) and vice versa (negative direction), A1=1, A2=1. If the duty cycle of the common bridge arm... D com The duty cycle remains unchanged at 0.5. The duty cycle sequence of the switches in the non-common arm is {0.5-A1u1, 0.5-A2u2, 0.5+A3u3,..., 0.5+A...} 2N u 2N When u1 and u2 are greater than 0.5, D 1= D com -A1u1 < 0, D 2= D com -A2u2 < 0, meaning that if winding 1 and winding 2 are to be modulated by the ideally calculated modulation waves u1 and u2, the duty cycle of the corresponding non-common bridge arm needs to be set to negative. As shown in Figure 6(a), the dashed line represents the duty cycle of the ideally calculated non-common bridge arm to be reversed. D 1. D 2 with public bridge arm D com The relationship between them is clear. In practice, the duty cycle cannot be negative. When the calculated duty cycle is negative, it will be set to 0 in practice. As shown in Figure 6(a), the solid line represents the duty cycle of the non-common bridge arm to be reversed during actual modulation. D 1. D 2 with public bridge arm D com The relationship between them. In this invention, in order to make the modulation wave actually modulated by winding 1 and winding 2 follow or approach the ideally calculated modulation wave u1, u2, the duty cycle of the common bridge arm switch is modulated. D com , so that the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N The maximum value in} is 1, as shown in Figure 6(b), making the duty cycle sequence { D com -A1u1,D com -A2u2, D com +A3u3,..., D com +A 2N u 2N The maximum value in} is 1, which actually means shifting the whole to the maximum limit of 1, ensuring that the relative relationship between the duty cycle of the non-common arm switch and the duty cycle of the common arm switch remains unchanged. At this time, the duty cycle of the non-common arm to be reversed during actual modulation, represented by the solid line, is... D 1. D 2. Duty cycle of public bridge arm D com The relative relationship between them increases, becoming closer to the ideally calculated modulation waves u1 and u2, thus enabling the actual modulation waves obtained by windings 1 and 2 to follow or approach the ideally calculated modulation waves u1 and u2. In one embodiment, during reversal, the modulation waves u1 and u2 can follow the duty cycle of the common arm switch. D com Soon D 1. D Set 2 directly to 0 to maximize the potential difference in the reverse direction.

[0057] As shown in Figure 7(a), when a fault occurs and it is necessary to reverse the current flow from the common arm to the non-common arm (negative direction) of windings 1 and 2, so that the current flows from the non-common arm to the common arm (positive direction), A1 = -1, A2 = -1. If the duty cycle of the common arm... D com The duty cycle remains unchanged at 0.5. The duty cycle sequence of the switches in the non-common arm is {0.5-A1u1, 0.5-A2u2, 0.5+A3u3,..., 0.5+A...} 2N u 2N When u1 and u2 are greater than 0.5, D 1= D com -A1u1>1, D 2= D com -A2u2>1, meaning that if winding 1 and winding 2 are to be modulated by the ideally calculated modulation waves u1 and u2, the duty cycle of the corresponding non-common bridge arm needs to be set to be greater than 1. As shown in Figure 7(a), the dashed line represents the duty cycle of the ideally calculated non-common bridge arm to be reversed. D 1. D 2 with public bridge arm D comrelationship between the duty cycles of the non-common bridge arms and the common bridge arms, obviously, the duty cycle in the actual situation cannot be greater than 1, when the calculated duty cycle is greater than 1, the duty cycle in the actual situation is set to 1, the solid line in Fig. 7(a) represents the duty cycle of the non-common bridge arms to be reversed in the actual modulation D 1、 D 2and the common bridge arms D com relationship between the duty cycles of the non-common bridge arms and the common bridge arms. In the present application, in order to make the modulation waves obtained by the actual modulation of the winding 1 and the winding 2 follow or approach the ideal calculated modulation waves u1, u2, the modulation common bridge arm switching tubes D com make the minimum value in the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} be 0, as shown in Fig. 7(b), make the minimum value in the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N} be 0, in fact, the whole is moved to the minimum limit 0, and the relative relationship between the duty cycles of the non-common bridge arms and the common bridge arms is ensured unchanged, at this time, the duty cycle of the non-common bridge arms to be reversed in the actual modulation represented by the solid line D 1、 D 2and the common bridge arms D com the relative relationship between the duty cycles of the non-common bridge arms and the common bridge arms is changed to be larger, and is closer to the ideal calculated modulation waves u1, u2, and the modulation waves obtained by the actual modulation of the winding 1 and the winding 2 follow or approach the ideal calculated modulation waves u1, u2. In an embodiment, the modulation waves u1, u2 can follow 1- D com that is, the D 1、 D 2are directly set to 1, so that the reversal has the maximum potential difference.

[0058] In an embodiment, when the magnetic suspension bearing circuit is normally operated, the N non-common bridge arms are divided into two parts, and the winding current directions of the two parts of the non-common bridge arms are opposite, so as to ensure that the overall bridge arm current stress is small.

[0059] The winding current controlled by the bridge arm in the normal control has the following characteristics:

[0060] In the normal state, to ensure that the overall bridge arm current stress is small, at least one group of non-common bridge arm groups in the N-axis controls two winding currents flowing from the non-common bridge arm group to the common bridge arm, and at least one group of non-common bridge arm groups controls two winding currents flowing from the common bridge arm to the non-common bridge arm group.

[0061] Further, when N is even, each part has N / 2 non-common bridge arm groups; when N is odd, one part has (N-1) / 2 non-common bridge arm groups, and the other part has (N+1) / 2 non-common bridge arm groups. Through the above current distribution, the overall bridge arm current stress can be minimized.

[0062] Based on the above stress reduction design, in an embodiment, when a circuit breaking fault occurs, the winding current between the non-common bridge arm group containing the circuit breaking fault switch and the common bridge arm is first controlled to reverse, and then the winding current between any one non-common bridge arm group in the other part and the common bridge arm is controlled to reverse. Thus, it can be ensured that the overall bridge arm current stress is small after the fault tolerant transient control is performed.

[0063] As shown in FIG. 8(a), the non-common bridge arm group corresponding to the circuit breaking fault switch is determined. When the winding current direction between the non-common bridge arm group and the common bridge arm is from the non-common bridge arm to the common bridge arm, the winding current direction between the non-common bridge arm group and the common bridge arm is first controlled to reverse, so that the winding current direction becomes from the common bridge arm to the non-common bridge arm. Then, from the other part of the non-common bridge arm group whose winding current direction is from the common bridge arm to the non-common bridge arm, any one non-common bridge arm group is selected and the winding current direction between the non-common bridge arm group and the common bridge arm is controlled to reverse, so that the winding current direction becomes from the non-common bridge arm to the common bridge arm.

[0064] Corresponding to FIG. 8(a), as shown in FIG. 8(b), it is a schematic diagram of the current flowing through the switch after the fault tolerant transient control is performed. Before the reversal, if the winding current flows from the non-common bridge arm to the common bridge arm, the triode in the upper switch of the non-common bridge arm and the diode in the lower switch are turned on, ensuring the normal flow of current. When the triode in the upper switch breaks down, the winding current is reversed, so that the diode in the upper switch of the non-common bridge arm and the triode in the lower switch are turned on, ensuring the normal operation of the circuit.

[0065] In an embodiment, the fault tolerant transient control method further comprises:

[0066] Collecting the current of the winding of each non-public bridge arm group and the public bridge arm, judging whether the bridge arm switch tube in each non-public bridge arm group appears open circuit fault according to the preset threshold.

[0067] Correspondingly, the application also relates to a fault-tolerant transient control system for a magnetic suspension bearing circuit.

[0068] The fault-tolerant transient control system is used for performing the following: when the open circuit fault occurs, the current of the winding 1 and the winding 2 between the non-public bridge arm group containing the open circuit fault switch tube and the public bridge arm is controlled to be reversed; wherein the method for controlling the current to be reversed at each step comprises the following steps: the duty ratio of the public bridge arm switch tube is adjusted to D com the duty ratio of the switch tube of the non-public bridge arm i corresponding to the winding i is adjusted to D i , D 1= D com -A1u1, D 2= D com -A2u2, D k = D com +A k u k , k≠1, 2; when D 1 or D 2 is less than 0, 0 is directly taken; when greater than 1, 1 is directly taken; wherein the winding current flowing from the non-public bridge arm into the public bridge arm is defined as positive direction, and the winding current flowing from the public bridge arm into the non-public bridge arm is defined as negative direction; when the current needs to be adjusted from the positive direction to the negative direction, D com the maximum value of the duty ratio sequence D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N is 1; when the current needs to be adjusted from the negative direction to the positive direction, D com the maximum value of the duty ratio sequence D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A2N u 2N is the minimum value in {u i is the winding modulation wave generated by the current loop of the winding i during the reverse period, A i is the coefficient of the winding i before the reverse, if the current flowing through the winding i before the reverse is positive, A i =1; if the current flowing through the winding i before the reverse is negative, A i =-1.

[0069] It can be understood that the fault-tolerant transient control system can be used to execute the fault-tolerant transient control method introduced above, and the specific execution process can refer to the above description.

[0070] Correspondingly, the application also relates to a magnetic suspension device, which comprises a magnetic suspension bearing, a magnetic suspension bearing circuit and a fault-tolerant transient control system used for the magnetic suspension bearing circuit and introduced above, wherein the fault-tolerant transient control system is used for controlling the magnetic suspension bearing circuit to make the circuit normally operate, so as to ensure the stability of the suspension bearing.

[0071] Those skilled in the art can understand that the above description is only the preferred embodiment of the application, and is not used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A fault-tolerant transient control method for a magnetic bearing circuit, characterized in that, the magnetic bearing circuit comprises a common bridge arm and N non-common bridge arm groups, each of which corresponds to control of one degree of freedom of the magnetic bearing; each non-common bridge arm group contains two non-common bridge arms, and the common bridge arm and each non-common bridge arm contain an upper switch tube connected to the positive pole of a DC power supply and a lower switch tube connected to the negative pole of the DC power supply; and a winding is arranged between the connection points of the upper and lower switch tubes of each non-common bridge arm and the connection points of the upper and lower switch tubes of the common bridge arm. The fault-tolerant transient control method comprises: when a circuit breaking fault occurs, controlling the current of winding 1 and winding 2 between the non-common bridge arm group containing the circuit breaking fault switch tube and the common bridge arm to be reversed; wherein, the method of controlling the current to be reversed at each step comprises: adjusting the duty cycle of the switch tube of the common bridge arm to D com adjusting the duty cycle of the switch tube of the non-common bridge arm i corresponding to the winding i to D i , D 1= D com -A1u1, D 2= D com -A2u2; D k = D com +A k u k , k≠1, 2; when D 1 or D 2 is less than 0, directly taking 0, and greater than 1, directly taking 1; wherein, The winding current is defined as flowing from a non-common arm into the common arm as positive, and flowing from a non-common arm into the common arm as negative; when the current needs to be adjusted from positive to negative... D com Satisfying the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N The maximum value in} is 1; when the current needs to be adjusted from negative to positive, D com Satisfying the duty cycle sequence { D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N The minimum value in} is 0; where u i A is the modulation wave of winding i calculated from the current loop. i For the coefficient of the reverse front winding i, if the current of the reverse front winding i is in the positive direction, A i =1; if the current of the reverse winding i is negative, A i =-1. 2.The fault-tolerant transient control method for a magnetic bearing circuit according to claim 1, characterized in that, when the magnetic bearing circuit is in normal operation, the N non-common bridge arm groups are divided into two parts, and the winding current directions of the two parts of non-common bridge arm groups are opposite.

3. The fault-tolerant transient control method for a magnetic bearing circuit of claim 2, wherein, When N is even, each part has N / 2 non-common bridge arm groups; when N is odd, one part has (N-1) / 2 non-common bridge arm groups, and the other part has (N+1) / 2 non-common bridge arm groups.

4. A fault-tolerant transient control method for a magnetic bearing circuit according to claim 2 or 3, characterized in that, After the current of the winding 1 and the winding 2 between the non-common bridge arm group containing the open-circuit fault switch tube and the common bridge arm is reversed, the method further comprises: controlling the winding current between any one non-common bridge arm group in the other part and the common bridge arm to be reversed.

5. The fault-tolerant transient control method for a magnetic bearing circuit of claim 4, wherein, After the winding current of the previous step is reversed and the rotor converges to a displacement less than a displacement threshold in the corresponding degree of freedom, the winding current of the next step is controlled to be reversed.

6. The fault-tolerant transient control method for a magnetic bearing circuit of claim 1, wherein, When the magnetic bearing circuit is in normal operation, the duty cycle of the switch tube of the common bridge arm is 0.

5.

7. The fault-tolerant transient control method for a magnetic bearing circuit of claim 1, wherein, The fault-tolerant transient control method further comprises: collecting the current of the winding of each non-common bridge arm group and the common bridge arm, and determining whether an open-circuit fault occurs in the bridge arm switch tube in each non-common bridge arm group according to a preset threshold. 8.A fault-tolerant transient control system for a magnetic bearing circuit, characterized in that, the magnetic bearing circuit comprises a common bridge arm and N non-common bridge arm groups, each of which corresponds to control of one degree of freedom of the magnetic bearing; each non-common bridge arm group contains two non-common bridge arms, and the common bridge arm and each non-common bridge arm contain an upper switch tube connected to the positive pole of a DC power supply and a lower switch tube connected to the negative pole of the DC power supply; and a winding is arranged between the connection points of the upper and lower switch tubes of each non-common bridge arm and the connection points of the upper and lower switch tubes of the common bridge arm. The fault-tolerant transient control system is used to perform: when a circuit breaking fault occurs, control the current of winding 1 and winding 2 between the non-public bridge arm group containing the circuit breaking fault switch tube and the public bridge arm to reverse; wherein, the method for controlling the current to reverse at each step comprises: adjusting the duty ratio of the switch tube of the public bridge arm to D com adjusting the duty ratio of the switch tube of the non-public bridge arm i corresponding to the winding i to D i , D 1= D com -A1u1, D 2= D com -A2u2, D k = D com +A k u k , k≠1, 2; when D 1 or D 2 is less than 0, directly taking 0, and greater than 1, directly taking 1; wherein, the winding current flowing from the non-public bridge arm into the public bridge arm is defined as positive direction, and the winding current flowing from the public bridge arm into the non-public bridge arm is defined as negative direction; when the current needs to be adjusted from positive direction to negative direction, D com satisfy the maximum value in the duty ratio sequence D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N is 1; when the current needs to be adjusted from negative direction to positive direction, D com satisfy the minimum value in the duty ratio sequence D com -A1u1, D com -A2u2, D com +A3u3,..., D com +A 2N u 2N is 0; wherein, u i is the modulation wave of the winding i calculated by the current loop, A i is the coefficient of the reversed winding i, if the current of the reversed winding i is positive, A i =1; if the current of the reversed winding i is negative, A i =-1.

9. The fault-tolerant transient control system for a magnetic bearing circuit of claim 8, wherein, When the magnetic bearing circuit is in normal operation, the N non-common bridge arm groups are divided into two parts, and the winding current directions of the two parts of non-common bridge arm groups are opposite. After the fault-tolerant transient control system controls the current of the winding 1 and the winding 2 between the non-common bridge arm group containing the open-circuit fault switch tube and the common bridge arm to be reversed, the fault-tolerant transient control system further controls the winding current between any one non-common bridge arm group in the other part and the common bridge arm to be reversed.

10. A magnetic levitation device, characterized by, The magnetic bearing, the magnetic bearing circuit, and the fault-tolerant transient control system for a magnetic bearing circuit according to claim 8 or 9.

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