Method and system for diagnosing open-circuit fault of power tube in hybrid energy source permanent magnet motor system

Abstract

The invention discloses a diagnosis method and system for open-circuit faults of a power tube in a hybrid energy source permanent magnet motor system, and the method comprises the steps: building a global mathematical model of a bidirectional DC / DC converter in the hybrid energy source permanent magnet motor system, and designing a sliding-mode observer to observe the current of a DC bus, a first current residual error is calculated through the observation value and the actual measurement value; according to the relation between the phase current of the permanent magnet motor side and a power tube trigger signal, calculating a direct current bus current, adding a compensation item to obtain an estimated direct current bus current, and calculating a second current residual error through the estimated direct current bus current and an actual measurement value; and an evaluation function is constructed based on the first current residual error and the second current residual error, whether an open-circuit fault occurs in a power tube in the bidirectional DC / DC converter is judged through the evaluation function, and a fault side is positioned when the fault occurs. According to the invention, the fault of the specific side of the hybrid energy source permanent magnet motor system can be efficiently and accurately detected and positioned, and the fault diagnosis efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault diagnosis and analysis, and in particular relates to a method and system for diagnosing open-circuit faults of power tubes in a hybrid energy source permanent magnet motor system. Background Art

[0002] For hybrid energy source permanent magnet motor systems, in actual operating conditions, the faults of bidirectional DC / DC converters and voltage-type converters mainly include power tube faults, capacitor faults, and interface faults. Among them, power tube faults account for about 31% of converter faults, mainly power tube open circuit faults and short circuit faults. Short circuit faults evolve quickly, and fast fuses are usually added to the converter to convert short circuit faults into open circuit faults. At present, for bidirectional DC / DC converters in hybrid energy source permanent magnet motor systems, the power tube fault diagnosis methods mainly include inductor voltage method, inductor current method, input current method, and diode voltage method. For voltage-type converters, power tube fault diagnosis methods are mainly divided into current-based and voltage-based fault diagnosis methods.

[0003] However, the current fault diagnosis of the power tubes of the bidirectional DC / DC converter and the voltage-type converter is performed separately without considering the coupling relationship between them. This separate diagnosis method not only reduces the efficiency of fault detection, but also increases the hardware cost. Long-term operation under fault conditions will reduce the reliability of the hybrid energy source permanent magnet motor system. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a diagnostic method and system for open-circuit faults of power tubes in hybrid energy source permanent magnet motor systems, which can not only improve the efficiency of fault diagnosis, but also reduce hardware costs, thereby improving the reliability and economy of the entire system to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for diagnosing an open circuit fault of a power tube in a hybrid energy source permanent magnet motor system, comprising:

[0006] Establish a global mathematical model of the bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system;

[0007] According to the global mathematical model, a sliding mode observer is designed to observe the DC bus current to obtain an observation value, and a first current residual is calculated by using the observation value and an actual measurement value;

[0008] According to the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, the DC bus current is calculated, and the estimated DC bus current is obtained after adding the compensation term, and the second current residual is calculated by the estimated DC bus current and the actual measurement value;

[0009] An evaluation function is constructed based on the first current residual and the second current residual, and the evaluation function is used to determine whether an open circuit fault occurs in a power tube in a bidirectional DC / DC converter, and locate the fault side when a fault occurs.

[0010] Preferably, the process of establishing a global mathematical model of a bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system includes:

[0011] Define the binary switching function of the battery and supercapacitor charge and discharge states;

[0012] establishing a local model according to the binary switching function;

[0013] The local models are integrated into a global mathematical model.

[0014] Preferably, the global mathematical model is:

[0015]

[0016] Among them, R1, L1, i L1 are the resistance, inductance and current of the battery side respectively; R2, L2, i L2 They are the resistance, inductance and current of the supercapacitor side respectively; V bat 、V sc are the battery voltage and the supercapacitor voltage respectively; V dc is the DC bus filter capacitor voltage, C dc is the DC bus filter capacitor; V' o is the DC bus output voltage V o The derivative of i o is the DC bus output current; d 01 d 23 It is the driving signal of the bidirectional DC / DC converter on the hybrid energy source side.

[0017] Preferably, according to the global mathematical model, the process of designing a sliding mode observer includes:

[0018] Converting the global mathematical model into a state-space equation form;

[0019] According to the state-space equation, a sliding mode observer is designed.

[0020] Preferably, the sliding mode observer is:

[0021]

[0022] in, are the observed values ​​of the output current on the battery side, the output current on the supercapacitor side, and the DC bus current; k e1, k e2 , k e3 is the feedback gain coefficient.

[0023] Preferably, the calculation formula of the DC bus current is:

[0024] i op =D a i a +D b i b +D c i c +D d i d +D e i e ;

[0025] Among them, i a 、i b 、i c 、i d 、i e are the phase currents flowing through the voltage converter on the permanent magnet motor side; D a , D b , D c , D d , D e They respectively represent the trigger signals corresponding to each power tube.

[0026] Preferably, the DC bus current formula after adding the compensation term is:

[0027] i p =i op +&(n);

[0028] Where n is the motor speed and & is the efficiency compensation factor.

[0029] Preferably, the formulas of the first current residual and the second current residual are:

[0030]

[0031] Among them, e HESS is the first current residual, is the observed value of DC bus current, i o is the DC bus output current, e PMSM is the second current residual, i p is the DC bus current after adding the compensation term.

[0032] Preferably, the evaluation function is:

[0033]

[0034] Where w is the size of the sliding window.

[0035] In a second aspect, the present invention further provides a system for diagnosing open circuit faults of power tubes in a hybrid energy source permanent magnet motor system, comprising:

[0036] A model building module is used to build a global mathematical model of a bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system;

[0037] A first calculation module is used to design a sliding mode observer according to the global mathematical model to observe the DC bus current, obtain an observation value, and calculate a first current residual through the observation value and an actual measurement value;

[0038] A second calculation module is used to calculate the DC bus current according to the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, and to obtain an estimated DC bus current after adding a compensation term, and to calculate a second current residual through the estimated DC bus current and an actual measurement value;

[0039] A fault judgment module is used to construct an evaluation function based on the first current residual and the second current residual, judge whether an open circuit fault occurs in the power tube in the bidirectional DC / DC converter through the evaluation function, and locate the fault side when a fault occurs.

[0040] Compared with the prior art, the present invention has the following advantages and technical effects:

[0041] The present invention provides a method for diagnosing an open-circuit fault of a power tube in a hybrid energy source permanent magnet motor system. First, a global mathematical model of a bidirectional DC / DC converter in the hybrid energy source permanent magnet motor system is established; secondly, a sliding mode observer is designed according to the global mathematical model to observe a DC bus current to obtain an observed value, and a first current residual is calculated by the observed value and an actual measured value; then, the DC bus current is calculated according to a relationship between a phase current on the permanent magnet motor side and a power tube trigger signal, and an estimated DC bus current is obtained after adding a compensation term, and a second current residual is calculated by the estimated DC bus current and the actual measured value; finally, an evaluation function is constructed based on the first current residual and the second current residual, and whether an open-circuit fault occurs in the power tube in the bidirectional DC / DC converter is determined by the evaluation function, and the fault side is located when a fault occurs.

[0042] The present invention starts from the perspective of the integration of a bidirectional DC / DC converter and a voltage-type converter. By analyzing the characteristics of the DC bus current under a power tube fault, it can efficiently and accurately detect and locate the fault on the specific side of the hybrid energy source permanent magnet motor system, improve the fault diagnosis efficiency, and reduce the hardware cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0044] Figure 1 A topological structure diagram of a hybrid energy source permanent magnet motor system according to an embodiment of the present invention;

[0045] Figure 2 It is a structural block diagram of a sliding mode observer of a bidirectional DC / DC converter on the hybrid energy source side according to an embodiment of the present invention;

[0046] Figure 3 This is a flow chart of a method for diagnosing an open-circuit fault of a power tube in a hybrid energy source permanent magnet motor system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0049] Embodiment 1

[0050] like Figure 1 As shown, the hybrid energy source system consists of a battery and a supercapacitor, two independent bidirectional DC / DC converters as interface circuits and a five-phase permanent magnet synchronous motor as a load.

[0051] This embodiment provides a method for diagnosing an open circuit fault of a power tube in a hybrid energy source permanent magnet motor system, comprising:

[0052] S1. Establish a global mathematical model of a bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system;

[0053] according to Figure 1 For a hybrid energy source system, the specific steps to establish a global mathematical model are as follows:

[0054]

[0055] Where R1, L1, i L1 are the resistance, inductance and current of the battery side respectively; R2, L2, i L2 They are the resistance, inductance and current of the supercapacitor side respectively; V bat 、V scare the battery voltage and the supercapacitor voltage respectively; V dc is the DC bus filter capacitor voltage, C dc is the DC bus filter capacitor; V' o is the DC bus output voltage V o The derivative of i o is the DC bus output current; d 01 d 23 It is the driving signal for the bidirectional DC / DC converter of the battery and supercapacitor.

[0056] according to Figure 1 The topological structure of the hybrid energy source can be built based on local modeling to establish a global mathematical model of the hybrid energy source. The specific modeling process can be carried out in the following three steps:

[0057] The binary switching functions according to the charge and discharge states of the battery and supercapacitor are defined as a and b respectively:

[0058]

[0059] i L1 >0 and i L2 >0:

[0060]

[0061] Where d0 and d2 are the power tube S of the hybrid energy source side. W0 , S W2 The power tube driving signal.

[0062] i L1 >0 and i L2 <0 hours:

[0063]

[0064] Where d3 is the power tube S on the hybrid energy source side W3 The power tube driving signal.

[0065] i L1 <0 and i L2 >0:

[0066]

[0067] Where d1 is the power tube S on the hybrid energy source side W1 The power tube driving signal.

[0068] i L1 <0 and i L2 <0 hours:

[0069]

[0070] Define μ 01 , μ 23 are the only driving signals of the battery and supercapacitor bidirectional DC / DC converter respectively, then:

[0071] d 01 =a(1-d0)+(1-a)d1 (8)

[0072] d 23 =b(1-d2)+(1-b)d3 (9)

[0073] The current idc through the DC bus capacitor is:

[0074]

[0075] The current io through the DC bus conductor resistance Ro is:

[0076]

[0077] According to equations (4), (5), (6), (7), (8), (9), (10), and (11), the mathematical model of the hybrid energy source side of the hybrid energy source permanent magnet motor system is:

[0078]

[0079] S2. According to the global mathematical model, a sliding mode observer is designed to observe the DC bus current, and a first current residual is calculated by using the observed value and the actual measured value;

[0080] like Figure 2 As shown, a sliding mode observer is constructed according to the state equations of the bidirectional DC / DC converters on both sides of the supercapacitor and the battery, and the sliding mode observer is used to observe the inductor current on the battery side, the inductor current on the supercapacitor side, and the DC bus current; specifically, the following steps are included:

[0081] Change equation (1) into the description form of state space equation:

[0082]

[0083] Where: x(t)=[i L1 i L2 i o ] T ,u(t)=[V bat -d 01 V dc V sc -d 23 V dc V o ′] T,y(t)=[i L1 i L2 i o ] T A is the system state matrix, B is the input matrix, C is the output matrix, x is the state variable, u is the input variable, and y is the output variable.

[0084] In order to analyze the observability of the system, the observability matrix is ​​calculated with the given parameters before designing the sliding mode observer and checked whether it is full rank. Since the rank of the C matrix is ​​3, the rank of the observability matrix of the system must be That is, the system is full rank and fully observable, which meets the requirements of the sliding mode observer. The sliding mode observer is designed as follows:

[0085]

[0086] In the formula is the observed value of the state variable x, is the observed value of the output variable y, and the gain parameter matrix k is expressed as Control convergence speed. The control block diagram of sliding mode observer and actual system is as follows Figure 2 As shown, the designed sliding mode observer is:

[0087]

[0088] S3, according to the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, the DC bus current is calculated, and the estimated DC bus current is obtained after adding the compensation term, and the second current residual is calculated by the estimated DC bus current and the actual measured value;

[0089] The permanent magnet motor side of the system adopts hysteresis control, which is a nonlinear, feedback-based control method that is widely used in situations with high dynamic performance requirements. Its core idea is to control the current within a set error band by adjusting the switching state of the voltage-type converter in real time. In the permanent magnet motor drive system, the hysteresis controller monitors the deviation between the phase current and the reference value in real time. When the deviation exceeds the preset error band, it quickly adjusts the switching state of the voltage-type converter to control the current back to a reasonable range.

[0090] However, since the switching frequency is not fixed and is affected by current fluctuations, the bus current will pulsate. If this pulsation characteristic is not accurately considered when estimating the DC bus current, it may lead to large estimation errors.

[0091] Ideally, the DC bus current on the permanent magnet motor side can be calculated by the relationship between each phase current and its power tube trigger signal, as shown in the following formula:

[0092] i op =Da i a +D b i b +D c i c +D d i d +D e i e (16)

[0093] Where i a 、i b 、i c 、i d 、i e are the phase currents flowing through the voltage converter on the permanent magnet motor side; D a , D b , D c , D d , D e They respectively represent the trigger signals corresponding to each power tube.

[0094] However, the above formula (14) is an idealized estimate. In the PWM control mode, this formula can estimate the bus current well. However, in the hysteresis control mode, due to the frequent changes in current pulsation, the definition of duty cycle is not stable, resulting in a decrease in the accuracy of this formula.

[0095] Through multiple simulations and experiments, it is found that formula (14) fails to fully reflect the various loss factors in actual operation, such as conduction loss, switching loss, wire resistance loss, iron loss, copper loss, and mechanical loss. Among them, copper loss and iron loss are usually the main sources of loss, and they are directly or indirectly related to the motor speed. These loss items significantly affect the dynamic characteristics of the bus current in actual operation, resulting in deviations in the bus current estimation results.

[0096] To be closer to the actual situation, the efficiency compensation factor & is added to the above formula (14), and the final estimated result is:

[0097] i p =i op +&(n) (17)

[0098] Where n is the speed, including the efficiency compensation factor & is the variable of the motor speed n, &(n) is the actual bus current i measured at different speeds o The theoretical bus current i op A linear equation about the speed is obtained by using the difference as compensation.

[0099] S4. Construct an evaluation function based on the first current residual and the second current residual, determine whether an open circuit fault occurs in the power tube in the bidirectional DC / DC converter through the evaluation function, and locate the fault side when a fault occurs.

[0100] like Figure 3 As shown in the figure, the current residuals on the hybrid energy source side and the motor side of the hybrid energy source permanent magnet motor system are defined as:

[0101]

[0102] The evaluation function for determining the residual signal is:

[0103]

[0104] Where w is the size of the sliding window.

[0105] When the system has no faults, the maximum value of the maximum residual evaluation function caused by parameter changes is selected as the threshold of the corresponding state. The selected threshold is as follows:

[0106] J th =max(J r ) (20)

[0107] Comparison J r (t)>J th :If J r (t)<J th , no open circuit fault occurs; otherwise, an open circuit fault occurs; when an open circuit fault occurs, the absolute values ​​of the bus current residuals on the hybrid energy source side and the motor side of the hybrid energy source permanent magnet motor system are compared, and an open circuit fault occurs on the power tube on the side with the larger absolute value.

[0108] Embodiment 2

[0109] Based on the same inventive concept, this embodiment also provides a diagnostic system for power tube open circuit fault in a hybrid energy source permanent magnet motor system, comprising:

[0110] A model building module is used to build a global mathematical model of a bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system;

[0111] A first calculation module is used to design a sliding mode observer to observe the DC bus current according to the global mathematical model, and calculate a first current residual through the observed value and the actual measured value;

[0112] The second calculation module is used to calculate the DC bus current according to the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, and to obtain the estimated DC bus current after adding the compensation term, and to calculate the second current residual by the estimated DC bus current and the actual measured value;

[0113] A fault judgment module is used to construct an evaluation function based on the first current residual and the second current residual, judge whether an open circuit fault occurs in the power tube in the bidirectional DC / DC converter through the evaluation function, and locate the fault side when a fault occurs.

[0114] The present embodiment provides a system for diagnosing open-circuit faults of power tubes in a hybrid energy source permanent magnet motor system, which has all the advantages of the method for diagnosing open-circuit faults of power tubes in a hybrid energy source permanent magnet motor system provided in the first embodiment.

[0115] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for diagnosing open circuit faults of power tubes in a hybrid energy source permanent magnet motor system, characterized in that: The following steps are involved: Establish a global mathematical model of the bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system; According to the global mathematical model, a sliding mode observer is designed to observe the DC bus current to obtain an observation value, and a first current residual is calculated by using the observation value and an actual measurement value; According to the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, the DC bus current is calculated, and the estimated DC bus current is obtained after adding the compensation term, and the second current residual is calculated by the estimated DC bus current and the actual measurement value; An evaluation function is constructed based on the first current residual and the second current residual, and the evaluation function is used to determine whether an open circuit fault occurs in a power tube in a bidirectional DC / DC converter, and locate the fault side when a fault occurs.

2. The method according to claim 1, characterized in that The process of establishing a global mathematical model of a bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system includes: Define the binary switching function of the battery and supercapacitor charge and discharge states; establishing a local model according to the binary switching function; The local models are integrated into a global mathematical model.

3. The method according to claim 1, characterized in that: The global mathematical model is: Among them, R1, L1, i L1 are the resistance, inductance and current of the battery side respectively; R2, L2, i L2 They are the resistance, inductance and current of the supercapacitor side respectively; V bat 、V sc are the battery voltage and the supercapacitor voltage respectively; V dc is the DC bus filter capacitor voltage, C dc is the DC bus filter capacitor; V' o is the DC bus output voltage V o The derivative of i o is the DC bus output current; d 01 ,d 23 It is the driving signal of the bidirectional DC / DC converter on the hybrid energy source side.

4. The method according to claim 1, characterized in that: According to the global mathematical model, the process of designing a sliding mode observer includes: Converting the global mathematical model into a state-space equation form; According to the state-space equation, a sliding mode observer is designed.

5. The method according to claim 1, characterized in that The sliding mode observer is: in, are the observed values ​​of the output current on the battery side, the output current on the supercapacitor side, and the DC bus current; k e1 , k e2 , k e3 is the feedback gain coefficient.

6. The method according to claim 1, characterized in that The calculation formula of the DC bus current is: i op =D a i a +D b i b +D c i c +D d i d +D e i e ; Among them, i a 、i b 、i c 、i d 、i e are the phase currents flowing through the voltage converter on the permanent magnet motor side; D a , D b , D c , D d , D e They respectively represent the trigger signals corresponding to each power tube.

7. The method according to claim 1, characterized in that The DC bus current formula after adding the compensation term is: i p =i op +&(n); Where n is the motor speed and & is the efficiency compensation factor.

8. The method according to claim 1, characterized in that: The formulas of the first current residual and the second current residual are: Among them, e HESS is the first current residual, is the observed value of DC bus current, i o is the DC bus output current, e PMSM is the second current residual, i p is the DC bus current after adding the compensation term.

9. The method according to claim 1, characterized in that: The evaluation function is: Where w is the size of the sliding window.

10. A diagnostic system for power tube open circuit fault in a hybrid energy source permanent magnet motor system, characterized in that: include: A model building module is used to build a global mathematical model of a bidirectional DC / DC converter in a hybrid energy source permanent magnet motor system; A first calculation module is used to design a sliding mode observer according to the global mathematical model to observe the DC bus current, obtain an observation value, and calculate a first current residual through the observation value and an actual measurement value; A second calculation module is used to calculate the DC bus current according to the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, and to obtain an estimated DC bus current after adding a compensation term, and to calculate a second current residual through the estimated DC bus current and an actual measurement value; A fault judgment module is used to construct an evaluation function based on the first current residual and the second current residual, judge whether an open circuit fault occurs in a power tube in a bidirectional DC / DC converter through the evaluation function, and locate the fault side when a fault occurs.

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