Fault diagnosis method and system for active device of active magnetic suspension bearing power amplifier

Abstract

The invention discloses a fault diagnosis method and system for an active device of an active magnetic suspension bearing power amplifier, and belongs to the technical field of magnetic suspension bearings, and the method comprises the steps: controlling each winding to be in an upward follow current state and a downward follow current state at the initial moment and the end moment of a switching period under a normal working condition; respectively acquiring direct-current bus current ibus1 and ibus2 at a starting moment and an ending moment, and winding current at an intermediate moment, and predicting winding current of a next switching period according to the winding current; if ibus1 is equal to 0 and ibus2 is equal to 0 and the error between the winding current predicted value and the measured value in the next switching period is large, the corresponding winding is controlled to be in a charging state at the initial moment of the next switching period, the direct current bus current and the winding current are compared, and if the error between the direct current bus current and the winding current is large, it is judged that a corresponding phase current sensor breaks down; and if ibus1 = 0 and ibus2 = 0 are not satisfied, judging that a transistor fault occurs. According to the invention, effective and rapid diagnosis of the active device in the magnetic suspension bearing power amplifier can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic suspension bearings, and more specifically, relates to a fault diagnosis method and system for active components of an active magnetic suspension bearing power amplifier. Background Art

[0002] Magnetic bearings support the rotor through electromagnetic force, avoiding direct contact between the rotor and the stator. Therefore, they have the advantages of low friction, no need for lubrication, and long life, and have become one of the best solutions for high-speed rotating machinery support. The rotor position of the magnetic bearing is controlled by a position loop and a current loop. The position controller outputs a current signal command based on the error between the position command and the actual position, and the current controller outputs a voltage signal command based on the error between the current signal command and the actual current. The output PWM is then modulated to control the on and off of the transistor in the power amplifier.

[0003] Since magnetic bearings are unstable in the open loop, their normal operation is completely dependent on the stable operation of the power amplifier. Therefore, how to improve the reliability of the power amplifier has become a hot topic in the field of magnetic bearings. The power amplifier mainly includes transistors, diodes, drive circuits, control parts, current sensors, inductors, and capacitors. Among them, active devices such as transistors and current sensors are more susceptible to harsh working conditions such as temperature and electromagnetic interference, resulting in performance degradation or even failure. Typical fault types include open circuit and short circuit faults of transistors, measurement faults of current sensors, etc.

[0004] At present, the fault diagnosis method for power amplifiers can only cover the open circuit fault and short circuit fault of the transistor, and is completely dependent on the normal operation of the phase current sensor. It is impossible to effectively diagnose the fault of the phase current sensor. At the same time, because the winding current cannot change suddenly, it takes a long time for the controller to accumulate to identify the fault characteristics, which is not conducive to the stable suspension of the rotor, and thus affects the stable operation 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 method and system for diagnosing faults of active devices in an active magnetic bearing power amplifier, the purpose of which is to achieve effective and rapid diagnosis of active devices in the magnetic bearing power amplifier and ensure the stable operation of the magnetic bearing.

[0006] To achieve the above object, according to one aspect of the present invention, a method for diagnosing active device faults of an active magnetic bearing power amplifier is provided, wherein the active magnetic bearing has 2N windings; the power amplifier includes 2N H bridges and 2N phase current sensors; each winding is connected in series with a phase current sensor, and both ends are respectively connected to the midpoints of two bridge arms of an H bridge; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of a DC bus; N is a positive integer;

[0007] The fault diagnosis method includes: controlling each winding to be in the upward freewheeling state and the downward freewheeling state at the start and end moments of the current switching cycle respectively, and obtaining the DC bus current value i bus1 (k) and i bus2 (k); controlling the states of each winding during the remaining time of the current switching cycle through the voltage command signals m1 to m 2N and obtaining the current values i1(k) to i 2N (k) of each winding at the intermediate moment through the phase current sensor; k represents the serial number of the current switching cycle;

[0008] If i bus1 (k) = 0 and i bus2 (k) = 0, then execute the following steps:

[0009] S1: Predict the current values of each winding in the next switching cycle according to i1(k) to i 2N (k)

[0010]

[0011] S2: Obtain the current values i1(k + 1) to i 2N (k + 1) of each winding through the phase current sensor in the (k + 1)-th switching cycle. If there is a winding that satisfies then go to S3; otherwise, go to S4; n ∈ {1, 2... 2N} represents the winding serial number; ε is a preset error threshold;

[0012] S3: At the start moment of the (k + 2)-th cycle, control the n-th winding to be in the charging state, while the remaining windings are all in the upward freewheeling state, and obtain the DC bus current value i bus1 (k + 2). Then, through the voltage command signals m1 to m 2N control the states of each winding, and obtain the current value i n (k + 2) of the n-th winding through the phase current sensor. If |i bus1 (k + 2) - i n (k + 2)| < ε, then go to S4; otherwise, determine that the current sensor in series with the n-th winding has a fault, and the diagnosis ends;

[0013] S4: Determine that there is no active device fault in the power amplifier, and the diagnosis ends.

[0014] Furthermore, within each switching cycle, the voltage command signals of the windings satisfy:

[0015] -1 + 2T d < m n < 1 - 2T d

[0016] Among them, T d represents the sampling dead zone.

[0017] Furthermore, in the power amplifier, each H-bridge includes a first arm and a second arm. The upper transistor of the first arm and the lower transistor of the second arm are both insulated gate bipolar transistors, and the lower transistor of the first arm and the upper transistor of the second arm are both diodes;

[0018] And, the fault diagnosis method further includes: if it does not satisfy i bus1 (k) = 0 and i bus2 (k) = 0, then it is determined that there is a transistor fault.

[0019] Furthermore, if there is a transistor fault, then perform the transistor fault diagnosis step; the transistor fault diagnosis step includes:

[0020] Judge the relationship between the current value of each winding in the current switching cycle and i bus1 (k) and i bus2 (k). If there is a winding that satisfies i bus1 (k) = -i n (k) and i bus2 (k) = 0, or i bus1 (k) = 0 and i bus2 (k) = i n (k), then it is determined that the upper transistor of the first arm in the H-bridge connected to the nth winding has a fault;

[0021] If there is a winding that satisfies i bus1 (k) = 0 and i bus2 (k) = -i n (k), or i bus1 (k) = i n (k) and i bus2 (k) = 0, then it is determined that the lower transistor of the second arm in the H-bridge connected to the nth winding has a fault.

[0022] Furthermore, if there is a winding that satisfies i bus1 (k) = -i n (k), i bus2 (k) = 0, then it is determined that the upper transistor of the first arm in the H-bridge connected to the nth winding has a short-circuit fault;

[0023] If there is a winding that satisfies i bus1 (k) = 0, i bus2 (k) = i n (k), then it is determined that the upper transistor of the first arm in the H-bridge connected to the nth winding has a short-circuit fault;

[0024] If there is a winding that satisfies i bus1(k) = 0, i bus2 (k) = -i n If i

[0025] If there exists a winding satisfying i bus1 (k) = i n (k), i bus2 (k) = 0, it is determined that the lower transistor of the second bridge arm in the H-bridge connected to the nth winding has an open-circuit fault.

[0026] Furthermore,

[0027]

[0028] wherein, R represents the winding resistance, and L n represents the inductance of the nth winding, T s represents the switching period, and V dc represents the bus voltage.

[0029] According to another aspect of the present invention, there is provided an active magnetic bearing power amplifier active device fault diagnosis system. The active magnetic bearing has 2N windings; the power amplifier includes 2N H-bridges and 2N phase current sensors; after each winding is connected in series with a phase current sensor, both ends are respectively connected to the midpoints of the two bridge arms of an H-bridge; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of the DC bus; N is a positive integer;

[0030] The fault diagnosis system includes: a bus current sensor and a fault diagnosis controller arranged on the DC bus side;

[0031] The fault diagnosis controller includes:

[0032] a computer-readable storage medium for storing a computer program;

[0033] and a processor for reading the computer program stored in the computer-readable storage medium to implement the active magnetic bearing power amplifier active device fault diagnosis method provided by the present invention.

[0034] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0035] (1) The failure of the phase current sensor will cause a large error between the winding current value sampled by the phase current sensor and the actual current value. Based on this, when the fault is not diagnosed in the present invention, each winding is controlled to be in the upward freewheeling state and the downward freewheeling state at the beginning and end of the switching period respectively, and the corresponding DC bus current is obtained. By comparing the error between the predicted value of the winding current and the sampling result of the phase current, the phase current sensor that may have a fault is located, and then the judgment result is calibrated with the DC bus voltage, so that the fault of the phase current sensor can be accurately diagnosed, and the entire diagnosis process can be completed within 2 switching periods, greatly shortening the diagnosis time. Generally speaking, the present invention can quickly and accurately diagnose the fault of the phase current sensor, improve the reliability of the power amplifier, and ensure the stable operation of the magnetic levitation bearing.

[0036] (2) In the preferred embodiment of the present invention, the present invention can also diagnose the fault of the transistor in the power amplifier of the active magnetic levitation bearing, making the fault types covered by the active device fault diagnosis more comprehensive. In its further preferred embodiment, by analyzing the relationship between the winding current and the DC bus current, the judgment and location of the specific fault type can be further realized, and the entire diagnosis process can be completed within only one switching period. Description of the Drawings

[0037] Figure 1 is a schematic diagram of the topology structure of the existing power amplifier for magnetic levitation bearings;

[0038] Figure 2 is a flowchart of the method for diagnosing the faults of active devices in the power amplifier of the magnetic levitation bearing provided by the embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of the winding state modulation strategy provided by the embodiment of the present invention; among them, (a) is a modulation schematic diagram of the upward freewheeling state and the downward freewheeling state, and (b) is a schematic diagram of charging at the initial moment of the switching period;

[0040] Figure 4 is a schematic diagram of the system for diagnosing the faults of active devices in the power amplifier of the magnetic levitation bearing provided by the embodiment of the present invention. Detailed Embodiment

[0041] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used 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.

[0042] 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, and do not necessarily describe a specific order or sequence.

[0043] Before explaining the technical solution of the present invention in detail, a brief introduction to the topology of the power amplifier of the active magnetic bearing is given first:

[0044] For an N-axis (N is a positive integer) magnetic bearing, it includes 2N windings, with every two windings in a group for controlling one axis. In practical applications, a typical one is a 5-axis magnetic bearing, and its 5 axes specifically refer to 4 directions in the radial direction and 1 direction in the axial direction.

[0045] Figure 1 The figure shows a schematic diagram of a power amplifier for controlling the windings in an N-axis magnetic bearing, which includes 2N H-bridges and 2N phase current sensors. After each winding is connected in series with a phase current sensor, both ends are respectively connected to the midpoints of the two bridge arms of an H-bridge. The phase current sensor can sample the winding current; each H-bridge includes a first bridge arm and a second bridge arm. The upper transistor of the first bridge arm and the lower transistor of the second bridge arm are both insulated gate bipolar transistors, and the lower transistor of the first bridge arm and the upper transistor of the second bridge arm are both diodes, preferably Schottky fast recovery diodes; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of the DC bus. Figure 1 In, in the H-bridge where the nth winding is located, the transistors in the first bridge arm and the second bridge arm are respectively represented by the symbols S 2n-1 and S 2n respectively, and the diodes in the first bridge arm and the second bridge arm are respectively represented by D 2n-1 and D 2n respectively.

[0046] The control system of the N-axis magnetic bearing adopts a differential control method. Each axis is controlled by two windings. The currents of the two windings can generate a differential electromagnetic force to control the position of the rotor on this axis; the rotor position is controlled by a double-loop control of a position loop and a current loop. The position loop controller outputs a current command signal, and the current loop controller outputs a voltage command signal.

[0047] Based on the above topology, each H-bridge controls the current of one winding. With different on and off states of the transistors on the two bridge arms in the H-bridge, each winding may have the following four states:

[0048] When the transistor in the first bridge arm is on and the transistor in the second bridge arm is off, the winding is in the upward freewheeling state;

[0049] When the transistor in the second bridge arm is on and the transistor in the first bridge arm is off, the winding is in the downward freewheeling state;

[0050] When both transistors are turned on, the winding is in the charging state;

[0051] When both transistors are turned off, the winding is in the discharging state.

[0052] The active devices in the power amplifier of the active magnetic bearing mainly include insulated gate bipolar transistors, their drive circuits and current sensors. Since the active devices require an additional auxiliary power supply, they are more prone to failures than passive devices. The typical failure types mainly include short circuit, open circuit of the insulated gate bipolar transistor, and the error between the measured value of the current sensor and the actual current value exceeding the allowable range.

[0053] The existing fault diagnosis methods for the active devices of the power amplifier of the active magnetic bearing can only achieve open circuit and short circuit faults of the transistors, and it takes a long time to accumulate to identify the fault characteristics after the fault occurs. To solve this technical problem, the present invention provides a fault diagnosis method and system for the active devices of the power amplifier of the active magnetic bearing. The overall concept is to control the winding state so that under different faults, the winding current value and the DC bus current value obtained by sampling through the phase current sensor satisfy a specific relationship, and the fault diagnosis is realized based on this specific relationship.

[0054] The following are embodiments.

[0055] Embodiment 1:

[0056] A fault diagnosis method for the active devices of the power amplifier of the active magnetic bearing. In this embodiment, the active magnetic bearing has 2N windings, and its power amplifier is as Figure 1 shown.

[0057] In the working condition where no fault is diagnosed in this embodiment, at the initial moment of the switching period, each winding is controlled to be in the upward freewheeling state, and at the end moment, the winding is controlled to be in the downward freewheeling state; when it is judged that the phase current sensor may be abnormal, the winding is controlled to be in the charging state at the initial moment of the switching period.

[0058] Through the above winding state control method, two bus currents and 2N phase currents, that is, winding currents, can be obtained in each switching period; in the normal working condition, at the initial moment and the end moment of the switching period, each winding current only passes through its own freewheeling circuit and does not flow through the DC bus. Correspondingly, both DC bus currents are 0. On the contrary, if both DC bus currents are not 0, it indicates that there is a transistor fault. In addition, it should be noted that in practical applications, the failure rate of the power amplifier of the active magnetic bearing is extremely low, and the probability of multiple faults occurring simultaneously is even lower. Therefore, in this embodiment, the fault diagnosis of the phase current sensor is only carried out when it is judged that there is no transistor fault.

[0059] Based on the above analysis, the fault diagnosis method provided in this embodiment is as follows Figure 2 shown, including: controlling each winding to be in the upward freewheeling state and the downward freewheeling state at the start time and the end time of the current switching cycle respectively, and obtaining the DC bus current values i bus1 (k) and i bus2 (k); controlling the states of each winding during the remaining time of the current switching cycle through the voltage command signals m1 to m 2N and obtaining the current values i1(k) to i 2N (k) of each winding at the intermediate time through the phase current sensor; k represents the serial number of the current switching cycle;

[0060] If i bus1 (k) = 0 and i bus2 (k) = 0, it indicates that a transistor fault has occurred, then the following steps are executed to diagnose possible phase current sensor faults:

[0061] S1: Predict the current values of each winding in the next switching cycle according to i1(k) to i 2N (k)

[0062]

[0063] Optionally, in this embodiment, for any nth winding, the following formula is used to predict its current value in the next switching cycle:

[0064]

[0065] where n ∈ {1, 2... 2N} represents the winding serial number; R represents the winding resistance, L n represents the inductance of the nth winding, T s represents the switching cycle, V dc represents the bus voltage;

[0066] S2: Obtain the current values i1(k + 1) to i 2N (k + 1) of each winding through the phase current sensor in the (k + 1)th switching cycle. If there is a winding that satisfies then it indicates that the phase current sensor connected in series with the nth winding may be faulty, and transfer to S3; otherwise, transfer to S4; ε is a preset error threshold;

[0067] A phase current sensor fault will cause a large error between the winding current value sampled by the phase current sensor and the actual current value. Based on this, step S2 of this embodiment judges that a phase current sensor fault may occur when the difference between the predicted value and the measured current value is large by comparing the predicted value with the measured current value;

[0068] S3: At the start of the (k + 2)-th cycle, control the n-th winding to be in the charging state, while the remaining windings are all in the upward freewheeling state, and obtain the current value i of the DC bus. bus1 (k + 2), and then control the states of each winding through the voltage command signals m1 to m 2N and obtain the current value i of the n-th winding through the phase current sensor. n (k + 2). If |i bus1 (k + 2) - i n (k + 2)| < ε, then transfer to S4; otherwise, determine that the current sensor connected in series with the n-th winding has a fault, and the diagnosis ends.

[0069] Affected by the displacement fluctuation and magnetic saturation of the magnetic bearing rotor, the winding inductance will change in real time, which leads to an error between the predicted current value and the actual value. Therefore, it is more likely to produce misjudgment only by judging through the predicted value. In step S3 of this embodiment, when it is judged in step S2 that a certain winding may have a fault, the determination result will be further calibrated through the bus current. Specifically, control the phase winding to be in the charging state at the start of the switching cycle, and obtain the corresponding DC bus current. At this time, the DC bus current is equal to the current of this phase winding. Then, use the phase current sensor to obtain the winding current, and compare the two current values. If the difference between the two is small, it means that the phase current sensor has no fault; otherwise, it is considered that the phase current sensor has a fault.

[0070] S4: Judge that there is no active device fault in the power amplifier, and the diagnosis ends.

[0071] Through the above diagnostic steps, this embodiment can accurately and reliably diagnose the phase current sensor fault, and moreover, the entire diagnostic process can be completed within two switching cycles, greatly shortening the diagnostic time and effectively ensuring the stable operation of the active magnetic bearing power amplifier.

[0072] The winding state of the active magnetic bearing is realized through modulation. Taking the n-th winding as an example, after the current loop outputs the voltage command signal m n , the modulation ratios d 2n-1 of the upper transistor S of the first bridge arm and the lower transistor S of the second bridge arm in the H-bridge where the winding is located can be calculated through the following formula (1). 2n Compare the modulation ratio with the upward-counting triangular carrier wave. For the transistors in the first bridge arm, when the modulation ratio d 2n-1 is greater than the carrier value, the transistor conducts; otherwise, it turns off. For the transistors in the second bridge arm, when the modulation ratio d 2n is greater than the carrier value, the transistor turns off; otherwise, it conducts. 2n-1 is greater than the carrier value, the transistor conducts; otherwise, it turns off. For the transistors in the second bridge arm, when the modulation ratio d 2n is greater than the carrier value, the transistor turns off; otherwise, it conducts.

[0073]

[0074] In practical applications, the DC bus current can also be obtained through a corresponding current sensor. In order to make the winding in the upward freewheeling state at the beginning of the switching period and in the downward freewheeling state at the end, and to reserve time for sampling the DC bus current at the beginning and end moments, in this embodiment, the voltage command signal is compressed by the following formula (2):

[0075] -1 + 2T d <m n <1 - 2T d (2)

[0076] Where, T d represents the sampling dead zone.

[0077] Figure 3 The modulation mode for realizing the winding state change in this embodiment is shown as follows. When it is necessary to realize that the winding is in the upward freewheeling state at the initial stage of the switching period and in the downward freewheeling state at the end moment, the modulation strategy shown in (a) in Figure 3 is adopted. For the upper transistor, when the modulation ratio is greater than the carrier value, the upper transistor is turned on, otherwise it is turned off; for the lower transistor, when the modulation ratio is greater than the carrier value, the lower transistor is turned off, otherwise it is turned on. When it is necessary to realize that the winding is charging at the initial moment of the switching period, the modulation mode shown in (b) in Figure 3 is adopted. For both the upper transistor and the lower transistor, when the modulation ratio is greater than the carrier value, the transistor is turned on; when the modulation ratio is less than the carrier value, the transistor is turned off.

[0078] In order to cover more fault types, as shown in Figure 2 , the fault diagnosis method provided in this embodiment further includes: if it does not satisfy i bus1 (k) = 0 and i bus2 (k) = 0, it is determined that there is a transistor fault.

[0079] Taking the transistor in the H-bridge where the first winding is located as an example, when the transistor S1 in the first bridge arm has a short-circuit fault, at the initial moment of the switching period, the winding should be in the upward freewheeling state, that is, only S1 is turned on. However, because S1 is open-circuited, the winding is actually in the discharging state, and at this time, the measured value of the bus current sensor is -i n ; while at the end moment of the switching period, the winding is in the downward freewheeling state, that is, only S2 is turned on and S2 works normally, so the measured value of the bus current sensor is 0. According to the same judgment method, the relationship between the phase current corresponding to different transistor faults and the DC bus current can be obtained, as shown in Table 1.

[0080] Table 1 Transistor fault types and positions

[0081]

[0082] Based on the analysis results corresponding to Table 1, when a transistor fault is determined in this embodiment, the transistor fault diagnosis step is executed; the transistor fault diagnosis step includes:

[0083] Judging the relationship between the current value of each winding in the current switching cycle and i bus1 (k) and i bus2 (k). If there is a winding that satisfies i bus1 (k) = -i n (k) and i bus2 (k) = 0, or i bus1 (k) = 0 and i bus2 (k) = i n (k), then it is determined that the upper transistor of the first bridge arm in the H-bridge connected to the nth winding has a fault;

[0084] If there is a winding that satisfies i bus1 (k) = 0 and i bus2 (k) = -i n (k), or i bus1 (k) = i n (k) and i bus2 (k) = 0, then it is determined that the lower transistor of the second bridge arm in the H-bridge connected to the nth winding has a fault.

[0085] More specifically, if there is a winding that satisfies i bus1 (k) = -i n (k), i bus2 (k) = 0, then it is determined that the upper transistor of the first bridge arm in the H-bridge connected to the nth winding has a short circuit fault;

[0086] If there is a winding that satisfies i bus1 (k) = 0, i bus2 (k) = i n (k), then it is determined that the upper transistor of the first bridge arm in the H-bridge connected to the nth winding has a short circuit fault;

[0087] If there is a winding that satisfies i bus1 (k) = 0, i bus2 (k) = -i n (k), then it is determined that the lower transistor of the second bridge arm in the H-bridge connected to the nth winding has an open circuit fault;

[0088] If there is a winding that satisfies i bus1 (k) = i n (k), i bus2 (k) = 0, then it is determined that the lower transistor of the second bridge arm in the H-bridge connected to the nth winding has a short circuit fault.

[0089] This embodiment can achieve the diagnosis of transistor faults within only one switching period, greatly shortening the diagnosis time.

[0090] Generally speaking, through the control of the winding state and the analysis of the relationship between the winding current and the DC bus current, this embodiment can achieve a comprehensive diagnosis of transistor open-circuit faults, transistor short-circuit faults, and phase current sensor faults in the power amplifier of the active magnetic bearing, greatly improving the reliability of the power amplifier and significantly shortening the fault diagnosis time.

[0091] Embodiment 2:

[0092] An active magnetic bearing power amplifier active device fault diagnosis system, where the active magnetic bearing has 2N windings; the power amplifier is as Figure 1 shown.

[0093] The fault diagnosis system provided by this embodiment is as Figure 4 shown, including: a bus current sensor and a fault diagnosis controller (not shown in the figure) arranged on the DC bus side;

[0094] The fault diagnosis controller includes:

[0095] A computer-readable storage medium for storing a computer program;

[0096] And a processor for reading the computer program stored in the computer-readable storage medium to implement the active magnetic bearing power amplifier active device fault diagnosis method provided in the above Embodiment 1.

[0097] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for diagnosing faults of active components of an active magnetic bearing power amplifier, wherein the active magnetic bearing has 2N windings; the power amplifier includes 2N H bridges and 2N phase current sensors; each winding is connected in series with a phase current sensor, and both ends are respectively connected to the midpoints of two bridge arms of an H bridge; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of a DC bus; N is a positive integer; It is characterized in that The fault diagnosis method comprises: controlling each winding to be in an upward freewheeling state and a downward freewheeling state at the beginning and end of the current switching cycle, respectively, and obtaining a DC bus current value i bus1 (k) and i bus2 (k); through the voltage command signal m1 ~ m 2N Control the state of each winding in the remaining time of the current switching cycle, and obtain the current value i1(k)~i1(k) of each winding at the intermediate moment through the phase current sensor. 2N (k); k represents the serial number of the current switching cycle; If i bus1 (k)=0 and i bus2 (k) = 0, then execute the following steps: S1: According to i1(k)~i 2N (k) Predict the current value of each winding in the next switching cycle S2: In the k+1th switching cycle, the current values ​​of each winding i1(k+1)~i 2N (k+1), if there exists a winding satisfying Then go to S3; otherwise, go to S4; n∈{1,2…2N} represents the winding number; ε is the preset error threshold; S3: At the beginning of the k+2th cycle, the nth winding is controlled to be in the charging state, while the other windings are in the upward freewheeling state, and the current value i of the DC bus is obtained. bus1 (k+2), and then through the voltage command signal m1~m 2N Control the state of each winding and obtain the current value i of the nth winding through the phase current sensor n (k+2), if |i bus1 (k+2)-i n (k+2)|<ε, then go to S4; otherwise, it is determined that the current sensor connected in series with the nth winding is faulty, and the diagnosis ends; S4: It is determined that no active device failure exists in the power amplifier, and the diagnosis ends.

2. The active magnetic bearing power amplifier active device fault diagnosis method according to claim 1, characterized in that: In each switching cycle, the voltage command signal of the winding satisfies: -1+2T d <m n <1-2T d Among them, T d Indicates the sampling dead zone.

3. The active magnetic bearing power amplifier active device fault diagnosis method according to claim 2, characterized in that: In the power amplifier, each H-bridge comprises a first bridge arm and a second bridge arm, the upper tube of the first bridge arm and the lower tube of the second bridge arm are both insulated gate bipolar transistors, and the lower tube of the first bridge arm and the upper tube of the second bridge arm are both diodes; Furthermore, the fault diagnosis method further comprises: if i is not satisfied bus1 (k)=0 and i bus2 (k) = 0, it is determined that there is a transistor failure.

4. The method for diagnosing faults of active components of an active magnetic bearing power amplifier according to claim 3, characterized in that: If there is a transistor fault, a transistor fault diagnosis step is performed; the transistor fault diagnosis step includes: Determine the current value of each winding in the current switching cycle and i bus1 (k) and i bus2 (k) If there is a winding that satisfies i bus1 (k) = -i n (k) and i bus2 (k) = 0, or i bus1 (k)=0 and i bus2 (k) = i n (k), it is determined that the upper tube of the first bridge arm of the H bridge connected to the nth winding is faulty; If there exists a winding that satisfies i bus1 (k)=0 and i bus2 (k) = -i n (k) or i bus1 (k) = i n (k) and i bus2 (k)=0, it is determined that the lower tube of the second bridge arm of the H bridge connected to the nth winding is faulty.

5. The method for diagnosing faults of active components of an active magnetic bearing power amplifier according to claim 4, characterized in that: If there exists a winding that satisfies i bus1 (k) = -i n (k), i bus2 (k)=0, it is determined that the upper tube of the first bridge arm of the H bridge connected to the nth winding has a short circuit fault; If there exists a winding that satisfies i bus1 (k) = 0, i bus2 (k) = i n (k), it is determined that the upper tube of the first bridge arm of the H bridge connected to the nth winding has a short circuit fault; If there exists a winding that satisfies i bus1 (k) = 0, i bus2 (k) = -i n (k), it is determined that the lower tube of the second bridge arm of the H bridge connected to the nth winding has a circuit breaker fault; If there exists a winding that satisfies i bus1 (k) = i n (k), i bus2 (k)=0, it is determined that a short circuit fault occurs in the lower tube of the second bridge arm of the H bridge connected to the nth winding.

6. The method for diagnosing faults of active components of an active magnetic bearing power amplifier according to any one of claims 1 to 5, characterized in that: Where R represents the winding resistance, L n represents the inductance of the nth winding, T s represents the switching cycle, V dc Indicates the bus voltage.

7. An active magnetic bearing power amplifier active device fault diagnosis system, the active magnetic bearing having 2N windings; the power amplifier comprising 2N H bridges and 2N phase current sensors; each winding is connected in series with a phase current sensor, and both ends are respectively connected to the midpoints of two bridge arms of an H bridge; the upper and lower ends of each bridge arm are respectively connected to the positive and negative poles of a DC bus; N is a positive integer; It is characterized in that The fault diagnosis system comprises: a bus current sensor and a fault diagnosis controller arranged on the DC bus side; The fault diagnosis controller comprises: A computer-readable storage medium for storing a computer program; and a processor, wherein the processor is used to read the computer program stored in the computer-readable storage medium to implement the active device fault diagnosis method of the active magnetic bearing power amplifier according to any one of claims 1 to 6.

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