A method and system for diagnosing open-circuit faults of power tubes in hybrid energy source permanent magnet motor systems

Abstract

The present invention discloses a method and system for diagnosing open-circuit faults in power tubes in a hybrid energy source permanent magnet motor system. The method comprises: establishing a global mathematical model of a bidirectional DC / DC converter in the hybrid energy source permanent magnet motor system, designing a sliding mode observer to observe the DC bus current, and calculating a first current residual by comparing the observed value with the actual measured value; calculating the DC bus current based on the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, and adding a compensation term to obtain an estimated DC bus current; calculating a second current residual by comparing the estimated DC bus current with the actual measured value; constructing an evaluation function based on the first and second current residuals, determining whether an open-circuit fault has occurred in the power tube in the bidirectional DC / DC converter by using the evaluation function, and locating the faulty side if a fault occurs. The present invention can efficiently and accurately detect and locate faults on a specific side of the hybrid energy source permanent magnet motor system, thereby improving fault diagnosis efficiency.

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, under actual operating conditions, bidirectional DC / DC converter and voltage-source converter faults primarily include power tube faults, capacitor faults, and interface faults. Power tube faults account for approximately 31% of converter faults, primarily open-circuit and short-circuit faults. Short-circuit faults evolve rapidly, and fast fuses are typically added to the converter to convert short-circuit faults into open-circuit faults. Currently, power tube fault diagnosis methods for bidirectional DC / DC converters in hybrid energy source permanent magnet motor systems primarily include the inductor voltage method, the inductor current method, the input current method, and the diode voltage method. For voltage-source converters, power tube fault diagnosis methods are primarily divided into current-based and voltage-based methods.

[0003] However, current fault diagnosis for the power transistors of bidirectional DC / DC converters and voltage-source converters is performed separately, without considering their coupling. This separate diagnostic approach not only reduces fault detection efficiency but also increases hardware costs. Prolonged operation under fault conditions can reduce the reliability of hybrid energy source permanent magnet motor systems. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a method and system for diagnosing 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 a 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 using the observation value and an actual measurement value;

[0008] Calculate the DC bus current based on the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, add the compensation term to obtain an estimated DC bus current, and calculate the second current residual using 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 to 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 They are the resistance, inductance and current of the battery side respectively; R2, L2, i L2 are the resistance, inductance, and current of the supercapacitor side respectively; V bat 、V sc are the battery voltage and 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 output current observation value of the battery side, the output current observation value of the supercapacitor side and the DC bus current observation value respectively; 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 for the first current residual and the second current residual are:

[0030]

[0031] Among them, e HESS is the first current residual, is the DC bus current observation value, 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, configured 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 using the observation value and an actual measurement value;

[0038] a second calculation module, configured to calculate a DC bus current based on a relationship between a phase current on the permanent magnet motor side and a power tube trigger signal, and to obtain an estimated DC bus current after adding a compensation term, and to calculate a second current residual using 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, 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.

[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. Second, based on 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 comparing the observation value with an actual measurement value. Next, based on 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 an estimated DC bus current is obtained after adding a compensation term. A second current residual is calculated by comparing the estimated DC bus current with the actual measurement value. Finally, an evaluation function is constructed based on the first current residual and the second current residual. The evaluation function is used to determine whether an open-circuit fault occurs in the power tube in the bidirectional DC / DC converter, and the fault side is located when a fault occurs.

[0042] The present invention integrates a bidirectional DC / DC converter and a voltage-type converter. By analyzing the characteristics of the DC bus current under power tube faults, it can efficiently and accurately detect and locate faults on specific sides of the hybrid energy source permanent magnet motor system, thereby improving fault diagnosis efficiency and reducing hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

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

[0045] Figure 2 This is a structural block diagram of a sliding mode observer for 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 open-circuit faults of power tubes 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 of the embodiments in this 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] Example 1

[0050] like Figure 1 As shown in FIG, 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, including:

[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 The specific steps for establishing a global mathematical model for a hybrid energy source system are as follows:

[0054]

[0055] Where R1, L1, i L1 They are the resistance, inductance and current of the battery side respectively; R2, L2, i L2 are the resistance, inductance, and current of the supercapacitor side respectively; V bat 、V scare the battery voltage and 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 battery and supercapacitor.

[0056] according to Figure 1 The hybrid energy source topology structure 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 hours:

[0060]

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

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

[0066]

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

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

[0069]

[0070] Define μ 01 、μ 23 are the only driving signals for the battery and supercapacitor bidirectional DC / DC converters 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 passing 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. Designing a sliding mode observer based on the global mathematical model to observe the DC bus current, and calculating a first current residual by comparing the observed value with the actual measured value;

[0080] like Figure 2 As shown in FIG, a sliding mode observer is constructed based on 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 the 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 will be calculated using the given parameters before designing the sliding mode observer, and its rank will be checked. Since the rank of the C matrix is ​​3, the rank of the system observability matrix 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 sliding mode observer and the actual system control block diagram are as follows Figure 2 As shown, the designed sliding mode observer is:

[0087]

[0088] S3. Calculate the DC bus current based on the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, add a compensation term to obtain an estimated DC bus current, and calculate the second current residual using the estimated DC bus current and the actual measured value;

[0089] The permanent magnet motor side of the system employs hysteresis control, a nonlinear, feedback-based control method widely used in applications requiring high dynamic performance. Its core concept is to control the current within a set error band by adjusting the switching state of the voltage-source converter in real time. In the permanent magnet motor drive system, the hysteresis controller monitors the deviation of the phase current from the reference value in real time. When the deviation exceeds the preset error band, it quickly adjusts the switching state of the voltage-source converter to control the current back within 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 from 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] While the above formula (14) is an idealized estimate, it can provide a good estimate of the bus current in PWM control mode. However, in hysteresis control mode, the definition of the duty cycle is unstable due to the frequent changes in current pulsation, resulting in a decrease in the accuracy of this formula.

[0095] Through multiple simulations and experiments, we found that Equation (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 generally the main loss sources, and they are directly or indirectly related to the motor speed. These loss terms 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, and &(n) is the actual bus current i measured at different speeds. o Compared with the theoretical bus current i op A linear equation about the speed is obtained by 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 of the bidirectional DC / DC converter by using 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 follows:

[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 thresholds are 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] Example 2

[0109] Based on the same inventive concept, this embodiment further provides a system for diagnosing open-circuit faults of power tubes 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, configured to design a sliding mode observer according to the global mathematical model to observe the DC bus current, and calculate a first current residual by using the observed value and the actual measured value;

[0112] A second calculation module is used to calculate the DC bus current based on 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. The second current residual is calculated by using 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, 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.

[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 merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection 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 a 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 using the observation value and an actual measurement value; 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; The sliding mode observer is: in, are the output current observation value of the battery side, the output current observation value of the supercapacitor side and the DC bus current observation value respectively; k e1 、k e2 、k e3 is the feedback gain coefficient; Calculate the DC bus current based on the relationship between the phase current on the permanent magnet motor side and the power tube trigger signal, add the compensation term to obtain an estimated DC bus current, and calculate the second current residual using the estimated DC bus current and the actual measurement value; 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 Respectively represent the trigger signals corresponding to each power tube; 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 to 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 They are the resistance, inductance and current of the battery side respectively; R2, L2, i L2 are the resistance, inductance, and current of the supercapacitor side respectively; V bat 、V sc are the battery voltage and 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, wherein 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.

5. The method according to claim 1, wherein The formulas for the first current residual and the second current residual are: Among them, e HESS is the first current residual, is the DC bus current observation value, 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.

6. The method according to claim 1, wherein The evaluation function is: Where w is the size of the sliding window.

7. A diagnostic system for power tube open circuit faults in a hybrid energy source permanent magnet motor system, characterized in that: For implementing the method according to any one of claims 1 to 6, the system comprises: 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, configured 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 using the observation value and an actual measurement value; a second calculation module, configured to calculate a DC bus current based on a relationship between a phase current on the permanent magnet motor side and a power tube trigger signal, and to obtain an estimated DC bus current after adding a compensation term, and to calculate a second current residual using 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, 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.

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