A sensor fault detection and fault-tolerant control method for dual active bridge DC / DC converter

Abstract

The application discloses a kind of dual active bridge DC / DC converter sensor fault detection and fault-tolerant control method, comprising: establishing dual active bridge DC / DC converter mathematical model, design is based on the load feedforward control method of dual active bridge DC / DC converter of current mode modulation;Dual active bridge DC / DC converter sliding mode observer is constructed, and sliding mode observer parameter is set;Dual active bridge DC / DC converter output voltage sensor is detected, and fault-tolerant control system is established, to realize the reliable operation of dual active bridge DC / DC converter.The method of the application overcomes the deficiencies in the prior art, such as poor robustness, difficulty in implementing fault-tolerant control, and the need for additional sensors, ensuring the normal operation of dual active bridge DC / DC converter under output voltage sensor failure conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronic system control, and particularly to a sensor fault detection and fault-tolerant control method for a dual-active-bridge DC / DC converter. BACKGROUND

[0002] Dual-active-bridge (DAB) DC / DC converters have attracted extensive attention from scholars at home and abroad due to their modular symmetric structure and bidirectional power transmission capability. In actual systems, due to high temperature, high humidity, chemical corrosion, static electricity and other reasons, sensors and their signal conditioning circuits have become one of the vulnerable links in power converter systems. When the sensors of a dual-active-bridge DC / DC converter fail, the output voltage of the dual-active-bridge DC / DC converter cannot be effectively closed-loop controlled, and the failure of the control system will further cause the abnormal shutdown of the converter device. Therefore, it is necessary to design a reasonable control algorithm to monitor the current / voltage and other states of the running power converter in real time and online, to timely discover system abnormalities, diagnose fault causes, and actively reconstruct the system control architecture, so that the entire system can still safely operate under the original performance indicators or with slightly reduced indicators.

[0003] Sensor faults mainly include open-circuit fault, gain abnormality, and noise abnormality. Existing fault detection methods for power electronic converters are mainly divided into two categories: data-driven methods and model-driven methods. Among them, the former does not need to deeply understand the physical model of the system, mainly relies on the data set collected from the equipment, and explores the correlation in the data through neural network algorithm, and then identifies the fault mode. Literature (Z. Y. Xue, et al. A data-driven diagnosis method of open-circuit switch faults for PMSG-based wind generation system [C]. IEEE 12th Int. Symp. Diagnostics Elect. Mach. Power Electron. Drives, 2019, 481-487) uses a convolutional neural network to diagnose open-circuit faults in motor inverters, but the convolutional neural network model requires a large amount of training data, and its performance on low data is not outstanding, and the data-driven method is only limited to fault diagnosis, and cannot provide effective fault-tolerant control schemes for the system. The model-driven method needs to have a deep understanding of the working principle of the system, and the state observer is established to predict the behavior of the system. Although this method relies on the physical model, the state observation error caused by the inaccuracy of the model can be compensated by the robustness of the high-performance state observer itself. For example, literature (Piyali Pal, et al. Eliminating Current Sensor Dependencies in DAB Converters Using a Luenberger Observer-Based Hybrid Approach [J]. IEEE Transactions on Industry Applications, 2024, 60(4): 6380-6392) designs a current sensor missing fault-tolerant control scheme based on Luenberger state observer, but this method only uses linear feedback-based error adjustment method, and the robustness of the observer still needs to be enhanced.

[0004] Through the analysis of the existing research results, it can be seen that: the data-driven method does not rely on the system model, but often needs a large amount of data to achieve a high fault diagnosis rate, and cannot control the fault tolerance of the system; the model-driven method can automatically switch the fault sensor value to the state observation value quickly after the sensor fails, and realize fault tolerance control, but the robustness of the existing method has not reached the best. Therefore, how to design a sensor fault detection and fault tolerance control algorithm with strong robustness, low implementation cost and excellent control effect for different fault types has become the key to improve the operation reliability of the dual active bridge DC / DC converter. SUMMARY

[0005] The purpose of the application is to provide a dual active bridge DC / DC converter sensor fault detection and fault tolerance control method to ensure that the dual active bridge DC / DC converter can operate normally when the voltage sensor fails.

[0006] Technical scheme: The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method comprises the following steps:

[0007] S1, establish a mathematical model of the dual active bridge DC / DC converter, and design a load current feedforward control method of the dual active bridge DC / DC converter based on current mode modulation;

[0008] S2, construct a sliding mode observer of the dual active bridge DC / DC converter, and set the parameters of the sliding mode observer;

[0009] S3, detect the fault of the output voltage sensor of the dual active bridge DC / DC converter, and establish a fault tolerance control system of the dual active bridge DC / DC converter; including: normalizing the observation error of the output voltage of the dual active bridge DC / DC converter to establish an output voltage residual error, detecting the fault sensor by comparing the output voltage residual error with a threshold value, then introducing the observation value of the sliding mode observer of the dual active bridge DC / DC converter into the feedback channel to replace the acquisition value of the fault sensor for closed-loop control, thereby realizing the fault tolerance control of the dual active bridge DC / DC converter.

[0010] Further, the mathematical model of the dual active bridge DC / DC converter in step S1 is:

[0011]

[0012] Wherein, Q A , Q B , Q C , Q D are four ideal switch functions of the bridge arm, L is the sum of the inductor coil and the transformer leakage inductance, that is, the equivalent inductance; i Lis the inductor current, k is the transformer ratio, v i and v o are the input and output voltages, respectively, C2 is the secondary side capacitor, i o is the output current.

[0013] Further, the load feedforward control of the dual active bridge DC / DC converter based on current mode modulation in step S1 is:

[0014] The current modulator receives the measured inductor current i L and the command value i Lr , and generates the switching signal of the secondary bridge, the feedforward control path F f controls i Lr , the input of F f is the load current i o , which is calculated according to the feedforward formula; the output of the feedback control path with a proportional integral PI link compensates, that is, Δi Lr ; i Lr is expressed as:

[0015]

[0016] Define i Lr as the reference value of the inductor current when the secondary side voltage of the dual active bridge DC / DC converter is reversed, i L The two segments of the waveform have different slopes M L1 and M L2 are expressed as:

[0017]

[0018] Based on the shift angle φ and the above formula, the given value i Lr of the inductor current satisfies:

[0019]

[0020] Where T sw is the switching period of the switching tube, and the time domain expression of i s2 (t) is:

[0021]

[0022] Taking the average of the above formula in the two subintervals, we get:

[0023]

[0024] Where i s2 is the average value of the inductor current in the two subintervals, and the sampling frequency f sw = 1 / T swFrom the above formula, we have:

[0025]

[0026] Thus, we have i Lr and the relationship of i s2 , that is, the expression of the original feedforward control path F f is:

[0027]

[0028] wherein the coefficient

[0029] The expression of the original feedforward control path F f is composed of two terms, one is a nonlinear function and the other is composed of v i , v o , f sw , k, L, since the time variation of the latter is much slower than the step variation of the output current, it is removed from the expression of the feedforward control path F f , which is compensated by the feedback control path; after simplification, the expression of the feedforward control path is designed as:

[0030]

[0031] wherein, is the output value of the feedforward control path.

[0032] Further, the step S2 comprises:

[0033] According to the mathematical model of the dual active bridge DC / DC converter, the dynamic equation of the sliding mode observer of the dual active bridge DC / DC converter is designed with the observation of the output voltage as the target:

[0034]

[0035] wherein, is the observation value of the inductor current, is the observation value of the output voltage, and p is the gain of the switching term, and l1 is the gain of the sliding mode observer to be designed; the dynamic equation of the sliding mode observer is subtracted from the mathematical model of the dual active bridge DC / DC converter, and the dynamic equation of the observation error is obtained as:

[0036]

[0037] wherein, e1 and e2 are the observation errors of the inductor current and the output voltage respectively, and are the time derivatives of the observation errors of the inductor current and the output voltage respectively.

[0038] Further, the size of the sliding mode observer gain l1 is designed by pole placement method; wherein, the sign of the sliding mode observer gain l1 is determined according to Lyapunov stability, including:

[0039] Construct Lyapunov function to determine the sign of the sliding mode observer gain l1, and the time derivative of Lyapunov function V is:

[0040]

[0041] wherein, the time derivative of V is the time derivative of e1 is; when , at this time e1 = 0, then the dynamic equation of output voltage observation error is simplified as:

[0042]

[0043] From the above formula, when l1(Q C -Q D ) > 0, the sliding mode observer converges; according to the switching state of Q C and Q D obtained by real-time acquisition, the sign of the sliding mode observer gain l1 is determined.

[0044] Further, step S3 includes:

[0045] The output voltage observation error of the dual active bridge DC / DC converter is normalized, and the absolute value of the sliding mode observer observation error of the dual active bridge DC / DC converter is divided by the given value of the output voltage to establish the residual error, and the specific calculation method is:

[0046]

[0047] wherein, v or is the given value of the output voltage, is the output voltage residual error;

[0048] By comprehensively considering the sliding mode observer observation error of the dual active bridge DC / DC converter and the sampling error of the output voltage sensor, the threshold value is determined;

[0049] When the output voltage sensor of the dual active bridge DC / DC converter does not fail, the obtained output voltage residual error will always be below the threshold value;

[0050] When the output voltage sensor of the dual active bridge DC / DC converter has an open circuit fault, abnormal sensor gain or abnormal noise, the output voltage residual will increase and exceed the threshold, and the output voltage sensor fault can be detected at this time;

[0051] Since the dual active bridge DC / DC converter sliding mode observer still works normally when the output voltage sensor fails, the observation value of the dual active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the output voltage sensor acquisition value for closed-loop control, so that the fault-tolerant control of the dual active bridge DC / DC converter is realized until the fault is eliminated.

[0052] Further, when the output voltage residual exceeds the threshold in the continuous 5 sampling periods, it is determined that the output voltage sensor has a fault.

[0053] The method corresponds to a system, comprising:

[0054] The feedforward control unit is configured to establish a mathematical model of the dual active bridge DC / DC converter, and design a load current feedforward control of the dual active bridge DC / DC converter based on current mode modulation.

[0055] The sliding mode observer and parameter setting unit is configured to construct a sliding mode observer of the dual active bridge DC / DC converter, and set parameters of the sliding mode observer.

[0056] The fault detection and fault-tolerant control unit is configured to detect faults of the output voltage sensor of the dual active bridge DC / DC converter, and establish a fault-tolerant control system of the dual active bridge DC / DC converter. The fault detection and fault-tolerant control unit comprises: normalizing an observation error of the output voltage of the dual active bridge DC / DC converter to establish an output voltage residual, comparing the output voltage residual with a threshold to detect a fault sensor, and then introducing an observation value of the sliding mode observer of the dual active bridge DC / DC converter into a feedback channel to replace an acquisition value of the fault sensor for closed-loop control, so as to realize fault-tolerant control of the dual active bridge DC / DC converter.

[0057] An electronic device for storing and executing the method, the device comprising:

[0058] A memory storing executable program codes;

[0059] A processor coupled with the memory;

[0060] The processor calls the executable program codes stored in the memory to execute the steps of the dual active bridge DC / DC converter fault detection and fault-tolerant control method.

[0061] A computer readable storage medium for storing and executing the method, the computer readable storage medium storing computer instructions, the computer instructions being invoked to perform the steps of the fault detection and fault-tolerant control method of the dual active bridge DC / DC converter.

[0062] Advantages: Compared with the prior art, the significant technical effects of the present application are: (1) The dual active bridge DC / DC converter control scheme designed by the present application has strong robustness, and when the load suddenly changes, the system output voltage fluctuation is small and can quickly recover to the steady state. (2) The voltage sensor fault detection and fault-tolerant control scheme designed by the present application has a simple control architecture, does not require complex calculation process, and the algorithm is easy to implement, and is more convenient to execute in the digital microprocessor used in the dual active bridge DC / DC converter system in the industry. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 is a flow chart of the method of the present application;

[0064] Figure 2 is a topology diagram of the dual active bridge DC / DC converter of the present application;

[0065] Figure 3 is a load current feedforward control structure block diagram of the dual active bridge DC / DC converter of the present application;

[0066] Figure 4 is a switch signal and voltage and current waveform of the dual active bridge DC / DC converter of the present application when operating normally;

[0067] Figure 5 is a simulation experiment result comparison of the load current feedforward control and the traditional voltage single closed loop control of the present application, wherein (a) is the simulation result of the traditional voltage single closed loop control, and (b) is the simulation result of the load current feedforward control;

[0068] Figure 6 is a simulation experiment result of the open circuit fault detection and fault-tolerant control of the voltage sensor of the present application, wherein (a) is the simulation result of the output voltage observation value and the fault sensor measurement value, (b) is the simulation result of the actual output voltage, and (c) is the simulation result of the output voltage residual error.

[0069] Figure 7 is a simulation experiment result of the gain abnormality detection and fault-tolerant control of the voltage sensor of the present application, wherein (a) is the simulation result of the output voltage observation value and the fault sensor measurement value, (b) is the simulation result of the actual output voltage, and (c) is the simulation result of the output voltage residual error.

[0070] Figure 8are simulation results of voltage sensor noise anomaly detection and fault-tolerant control of the application, wherein (a) is a simulation result of output voltage observation value and fault sensor measurement value, (b) is a simulation result of output voltage actual value, and (c) is a simulation result of output voltage residual error. DETAILED DESCRIPTION

[0071] The application will be described in detail below in combination with the drawings and specific embodiments.

[0072] As shown in the drawings, a sensor fault detection and fault-tolerant control method of a dual active bridge DC / DC converter of the application comprises the following steps: Figure 1

[0073] S1, a mathematical model of a dual active bridge DC / DC converter is established, and a load current feedforward control method of the dual active bridge DC / DC converter based on current mode modulation is designed; specifically:

[0074] The topology of the dual active bridge DC / DC converter is shown in the drawings, which is composed of an AC / DC converter, a transformer and a DC / AC converter. According to Kirchhoff's voltage law, the following equation can be obtained: Figure 2

[0075]

[0076] wherein, u AB is the primary side voltage of the dual active bridge DC / DC converter (including the primary side voltage of the transformer and the voltage on the inductor L); u CD is the secondary side voltage of the dual active bridge DC / DC converter (i.e. the secondary side voltage of the transformer); k is the transformer ratio; L is the sum of the auxiliary inductance of the coil and the leakage inductance of the transformer, i.e. the equivalent inductance; i L is the inductor current.

[0077] The ideal switch functions Q A , Q B , Q C , Q D of the four bridge arms are defined as:

[0078]

[0079] wherein, S i and D i represent the IGBT and the reverse diode of the bridge arm i (i=1, 2,..., 8) respectively.

[0080] According to the topology, the following equation can be obtained: Figure 2

[0081]

[0082] wherein, v​​​i and v o These are the input voltage and the output voltage, respectively. Substituting (3) into (1), we obtain the primary side voltage equation (including the transformer and the coil auxiliary inductor) of the dual active bridge DC / DC converter as follows:

[0083]

[0084] According to the law of conservation of power, the current equation for the secondary side (i.e., the AC / DC converter) of the dual active bridge DC / DC converter can be obtained as follows:

[0085]

[0086] Among them, i s2 This is the output current of the secondary bridge arm, C2 is the secondary capacitor, and i o Let the output current be the output current. After simplification, the mathematical model of the dual active bridge DC / DC converter is:

[0087]

[0088] The block diagram of the load-current-feedforward (LCFF) control structure of the dual active bridge DC / DC converter used in this invention is as follows: Figure 3 As shown, the current modulator receives the measured inductor current i L and instruction value i Lr This generates a switching signal S2 for the secondary bridge, which is implemented using an RS flip-flop (RS) and two comparators.

[0089] In LCFF control, the feedforward control path F f control F f The input is the load current i o Output value of the feedforward control path The result is calculated based on the feedforward formula. Furthermore, output compensation for the feedback control path, specifically Δi, is required using a proportional-integral (PI) loop. Lr At this time, i Lr Represented as:

[0090]

[0091] Where, Δi Lr This is for output compensation of the feedback control path.

[0092] according to Figure 4 , change i Lr Defined as the reference value of the inductor current when the secondary side voltage of a dual active bridge DC / DC converter reverses, iL Waveform Two different slopes M L1 With M L2 Indicated as:

[0093]

[0094] Based on the shift angle φ and the above formula, the peak current I0 and the inductance current given value i Lr Satisfy the following formula:

[0095]

[0096] Where, T sw The switching period of IGBT switch tube. The difference between the two formulas in (9) is made, and the slope formula M L1 , M L2 In (8) is substituted to obtain:

[0097]

[0098] For easy derivation, define t = 0 in Figure 4 At this time, i s2 (t) is expressed as:

[0099]

[0100] In the two sub-intervals ( and ) in formula (11), the average value of the above formula is obtained:

[0101]

[0102] Where, the sampling frequency is f sw = 1 / T sw . From the above formula, we can get:

[0103]

[0104] From this, we can get the relationship between i Lr and , that is, the expression of the original feedforward control path F f :

[0105]

[0106] Where, the coefficient

[0107] The expression of the original feedforward control path F f is composed of two terms, one is the nonlinear function The other is v i , v o , fsw , k, L. Since the time variation of the latter is much slower than the step variation of the output current, it is removed from the expression of the feedforward control path F f and compensated by the feedback control path. After simplification, the feedforward formula is designed as:

[0108]

[0109] where, is the output value of the feedforward control path, is the average value of the inductor current in the two sub-intervals.

[0110] S2, construct a sliding mode observer for the dual active bridge DC / DC converter, and set the parameters of the sliding mode observer; specifically:

[0111] According to the mathematical model of the dual active bridge DC / DC converter (i.e. formula (6)), the dynamic equation of the sliding mode observer is designed as:

[0112]

[0113] where, is the observed value of the inductor current, is the observed value of the output voltage, and ρ is the gain of the switching term, and l1 is the gain of the sliding mode observer to be designed. Subtracting (16) from (6), the dynamic equation of the observation error is:

[0114]

[0115] where, e1 and e2 are the observation errors of the inductor current and the output voltage, and are the time derivatives of the observation errors of the inductor current and the output voltage, respectively. The size of the gain l1 is designed by the pole placement method.

[0116] Next, the sign of the sliding mode observer gain l1 is judged according to Lyapunov stability, including:

[0117] The Lyapunov function V is constructed as: to judge the sign of the sliding mode observer gain l1. Taking the time derivative of the Lyapunov function V, we have:

[0118]

[0119] where, is the time derivative of V, is the time derivative of e1.

[0120] When is satisfied, at this time e1 = 0 The dynamic equation of the output voltage observation error is simplified as:

[0121]

[0122] From the above formula, when l1(Q C -Q D )>0, the sliding mode observer converges. According to the switching state of Q C and Q D obtained in real time, the sign of the gain l1 can be determined.

[0123] S3, fault detection is performed on the output voltage sensor of the dual active bridge DC / DC converter, and a fault-tolerant control system of the dual active bridge DC / DC converter is established; including: the observation error of the output voltage of the dual active bridge DC / DC converter is normalized to establish the output voltage residual error, the fault sensor is detected by comparing the output voltage residual error with the threshold value, then the observation value of the sliding mode observer of the dual active bridge DC / DC converter is introduced into the feedback control to replace the acquisition value of the fault sensor for closed-loop control, so that the fault-tolerant control of the dual active bridge DC / DC converter is realized; specifically:

[0124] The application considers that the fault sensor of the dual active bridge DC / DC converter is an output voltage sensor, and the three types of faults considered are open circuit fault, abnormal sensor gain and abnormal noise.

[0125] The observation error of the output voltage of the dual active bridge DC / DC converter is normalized, and the absolute value of the observation error of the sliding mode observer of the dual active bridge DC / DC converter is divided by the given value of the output voltage to establish the residual error, and the specific calculation method is:

[0126]

[0127] Wherein, v or is the given value of the output voltage, is the output voltage residual error.

[0128] By comprehensively considering the observation error of the sliding mode observer of the dual active bridge DC / DC converter and the sampling error of the output voltage sensor, a threshold value is left out with a margin of 3 times.

[0129] When the output voltage sensor of the dual active bridge DC / DC converter does not fail, the obtained output voltage residual error will always be below the threshold value.

[0130] When the output voltage sensor of the dual active bridge DC / DC converter has an open circuit fault, an abnormal sensor gain or an abnormal noise, the output voltage residual error will increase and exceed the threshold value, at which time the output voltage sensor fault can be detected.

[0131] In order to reduce the probability of misdiagnosis, the application designs that when the output voltage residual error exceeds the threshold value in the continuous 5 sampling periods, it can be determined that the sensor fails.

[0132] Since the double active bridge DC / DC converter sliding mode observer still works normally when the output voltage sensor fails, the observation value of the double active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the acquisition value of the output voltage sensor for closed-loop control, so that the fault-tolerant control of the double active bridge DC / DC converter can be realized until the fault is eliminated.

[0133] The sensor fault detection and fault-tolerant control system of the double active bridge DC / DC converter of the application comprises:

[0134] The feedforward control (LCFF) unit is used to establish the mathematical model of the double active bridge DC / DC converter and design the load current feedforward control of the double active bridge DC / DC converter based on current mode modulation; the control unit is used to improve the output voltage stability and load disturbance resistance of the double active bridge DC / DC converter system; specifically, the input voltage, output voltage and inductance current of the double active bridge DC / DC converter are collected, the output value of the feedforward path is calculated, and the output value of the voltage single-closed-loop PI controller is superimposed as the modulation signal of the current modulator;

[0135] The sliding mode observer and parameter setting unit is used to design the output voltage observation scheme of the double active bridge DC / DC converter, construct the sliding mode observer of the double active bridge DC / DC converter, and set the parameters of the sliding mode observer; specifically, the sliding mode observer of the output voltage of the double active bridge DC / DC converter is designed, the Lyapunov function is constructed based on the quadratic form of the output voltage observation error, and the sign and lower limit of the coefficient value of the sliding mode observer switching function term are obtained by scaling the time derivative.

[0136] The fault detection and fault-tolerant control unit is used to detect the output voltage sensor fault of the double active bridge DC / DC converter and establish the fault-tolerant control system; specifically, the output voltage residual error is established by normalizing the observation error of the output voltage of the double active bridge DC / DC converter, the fault sensor is detected by comparing the output voltage residual error with the threshold value, then the observation value of the sliding mode observer of the double active bridge DC / DC converter is introduced into the feedback channel to replace the acquisition value of the fault sensor for closed-loop control, so that the fault-tolerant control of the double active bridge DC / DC converter can be realized.

[0137] The electronic device of the application comprises:

[0138] The memory stores executable program codes;

[0139] a processor coupled to the memory;

[0140] The processor calls the executable program code stored in the memory to execute the steps of the sensor fault detection and fault-tolerant control method of the dual active bridge DC / DC converter as described above.

[0141] The computer readable storage medium of the application stores computer instructions, which when called, are used to execute the steps of the sensor fault detection and fault-tolerant control method of the dual active bridge DC / DC converter as described above.

[0142] The effectiveness of the sensor fault detection and fault-tolerant control method of the dual active bridge DC / DC converter proposed by the application is verified by MATLAB / Simulink simulation experiments, and simulation experiment results are given. In the simulation experiment, the parameters of the dual active bridge DC / DC converter are as follows:

[0143] The input voltage is 540V, the output voltage is 28V, the primary side inductance is 0.14mH, the switching frequency is 10kHz, the power supply resistance is 0.001Ω, the primary side capacitance is 3600μF, the secondary side capacitance is 3600μF, and the transformer ratio is 19.

[0144] In the simulation experiment, at t=0.1s, the load mutation is introduced, and the equivalent load resistance is switched from 1Ω to 0.5Ω. The simulation results of the starting process of the dual active bridge DC / DC converter system and the load mutation are shown in Figs. Figure 5 (a) and (b). At t=0.2s, voltage sensor open circuit fault, gain anomaly and noise anomaly are introduced respectively. The simulation results are shown in Figs. Figure 6 (a), (b) and (c), Figure 7 (a), (b) and (c), Figure 8 (a), (b) and (c). As can be seen from Figs. Figure 5 (a) and (b), the output voltage of the secondary side of the traditional voltage single closed loop control under load mutation decreases by about 4V, and the output voltage recovers to the given value of 28V after about 0.025s adjustment time. The LCFF control adopted by the application has stronger robustness and anti-load disturbance ability, and the output voltage of the secondary side under load mutation decreases by only 0.1V, and the adjustment time is shortened to 0.005s. As can be seen from Figs. Figure 6 (a), (b) and (c), Figure 7 (a), (b) and (c), Figure 8From the above(a), (b) and (c), it can be seen that the designed sliding mode observer can realize accurate observation of the output voltage before and after the introduction of load disturbance. After the voltage sensor fails, the voltage residual error exceeds the threshold value after 5 sampling periods, which means that the sensor fault is detected. Due to the implementation of the fault-tolerant control, the observation value of the sliding mode observer of the dual active bridge DC / DC converter is introduced into the feedback channel to replace the collected value of the failed sensor for closed-loop control, so that the actual output voltage is not affected by the sensor fault and is still stable at 28V, thereby proving the effectiveness of the sensor fault diagnosis and fault-tolerant control strategy of the dual active bridge DC / DC converter.

Claims

1. A method for sensor fault detection and fault-tolerant control of a dual active bridge DC / DC converter, characterized in that, The method comprises the following steps: S1, establishing a mathematical model of the dual active bridge DC / DC converter, and designing a load current feedforward control method of the dual active bridge DC / DC converter based on current mode modulation; The load feedforward control of the dual active bridge DC / DC converter based on current mode modulation is as follows: The current modulator receives the measured inductance current and a given value of the inductance current , generates a switching signal for the secondary bridge, a feedforward control path control , The input for the current modulator is the load current , is calculated according to the feedforward formula; The output compensation is fed back by a proportional-integral (PI) loop, i.e. ; is represented as: ， Waveform two different slopes With Is represented as: ， Based on the phase shift angle And the above formula, the inductance current is given value Satisfies: ， wherein the switching period of the switching transistor, the time domain expression of the is ， The average value of the above formula in the two sub-intervals is obtained as follows: ， wherein, is the average value of the secondary side bridge arm output current in the two sub-intervals, the sampling frequency From the above formula, we can get: ， From this it follows that The relationship between the original feedforward control path is given by the expression ， wherein the coefficients ; Original feedforward control path The expression consists of two terms, one of which is a nonlinear function. Another item by composition, For transformer turns ratio, and These are the input voltage and the output voltage, respectively. This is the sum of the leakage inductance of the inductor coil and the transformer. It is the output current of the secondary side bridge arm. This is the peak current; since the latter changes much more slowly over time than the step-change output current, it is removed from the feedforward control path. The expression is removed and compensated by the feedback control path; after simplification, the feedforward control path expression is designed as follows: ， wherein is the output value of the feedforward control path; S2, constructing a sliding mode observer of the dual active bridge DC / DC converter, and setting the parameters of the sliding mode observer; S3, detecting a fault of an output voltage sensor of the dual active bridge DC / DC converter, and establishing a fault-tolerant control system of the dual active bridge DC / DC converter; including: normalizing an observation error of the output voltage of the dual active bridge DC / DC converter to establish an output voltage residual error, detecting a fault sensor by comparing the output voltage residual error with a threshold value, then introducing an observation value of the sliding mode observer of the dual active bridge DC / DC converter into a feedback channel to replace a collection value of the fault sensor for closed-loop control, so as to realize the fault-tolerant control of the dual active bridge DC / DC converter.

2. The method of claim 1, wherein, The mathematical model of the dual active bridge DC / DC converter in step S1 is as follows: ， where Q A , Q B , Q C , Q D are the ideal switching functions of the four legs, is the sum of the inductor and the transformer leakage inductance, i.e. the equivalent inductance; is the inductor current, is the transformer turns ratio, and are the input and output voltages, respectively, C2 is the secondary side capacitor, is the load current.

3. The method of claim 1, wherein the sensor fault detection and fault-tolerant control method of a dual active bridge DC / DC converter is characterized by, Step S2 comprises: According to the mathematical model of the dual active bridge DC / DC converter, the dynamic equation of the sliding mode observer of the dual active bridge DC / DC converter is designed as follows: ， wherein, is the inductor current observation value, is the output voltage observation value, and ρ is the switching term gain, is the sliding mode observer gain to be designed, Q A , Q B , Q C , Q D is the ideal switching function of the four bridge arms, is the sum of the inductor coil and the transformer leakage inductance, i.e., the equivalent inductance; is the transformer ratio, is the input voltage, and C2 is the secondary side capacitor, is the load current; the dynamic equation of the sliding mode observer is subtracted from the mathematical model of the dual active bridge DC / DC converter to obtain the dynamic equation of the observation error: ， wherein, and are the observation errors of the inductor current and the output voltage, respectively, and are the time derivatives of the observation errors of the inductor current and the output voltage, respectively.

4. The method of claim 3, wherein, The size of the sliding mode observer gain l1 is designed by the pole placement method; wherein, the sign of the sliding mode observer gain l1 is judged according to Lyapunov stability, including: Constructing Lyapunov function The sign of the sliding mode observer gain l1 is determined, and the time derivative of the Lyapunov function V is obtained, that is: ， wherein, is the time derivative of V, is the time derivative of is the time derivative of V; when satisfies , , at this time , the dynamic equation of the output voltage observation error is simplified as: ， From the above formula, when the sliding mode observer converges; according to the real-time collected Q C and the switching state of Q D , the sign of the sliding mode observer gain l1 is determined.

5. The method of claim 1, wherein, Step S3 comprises: The observation error of the output voltage of the dual active bridge DC / DC converter is normalized, and the absolute value of the observation error of the sliding mode observer of the dual active bridge DC / DC converter is divided by the given value of the output voltage to establish a residual error, and the specific calculation method is as follows: ， wherein, is the output voltage given value, is the output voltage residual; By comprehensively considering the sliding mode observer observation error of the dual active bridge DC / DC converter And the output voltage sensor sampling error, determine the threshold; When the output voltage sensor of the dual active bridge DC / DC converter does not fail, the obtained output voltage residual error will always be below the threshold value; When the output voltage sensor of the dual active bridge DC / DC converter fails in open circuit, the sensor gain is abnormal or the noise is abnormal, the output voltage residual error will increase and exceed the threshold value, at which time the output voltage sensor failure can be detected; Since the sliding mode observer of the dual active bridge DC / DC converter still works normally when the output voltage sensor fails, the observation value of the sliding mode observer of the dual active bridge DC / DC converter is introduced into the feedback channel to replace the collection value of the output voltage sensor for closed-loop control, so that the fault-tolerant control of the dual active bridge DC / DC converter can be realized until the fault is eliminated.

6. The method of claim 5, wherein the sensor fault detection and fault-tolerant control method of a dual active bridge DC / DC converter is characterized by, When the output voltage residual error exceeds the threshold value in the continuous 5 sampling periods, it is determined that the output voltage sensor fails.

7. A system for the method of fault detection and fault-tolerant control of a dual active bridge DC / DC converter according to any of claims 1-6, characterized in that, The method comprises the following steps: The feedforward control unit is used for establishing a mathematical model of the dual active bridge DC / DC converter, and designing a load current feedforward control method of the dual active bridge DC / DC converter based on current mode modulation; The sliding mode observer and parameter setting unit is used for constructing a sliding mode observer of the dual active bridge DC / DC converter, and setting the parameters of the sliding mode observer; The fault detection and fault-tolerant control unit is used for fault detection of a dual active bridge DC / DC converter output voltage sensor and establishment of a dual active bridge DC / DC converter fault-tolerant control system, and comprises: normalizing an observation error of the dual active bridge DC / DC converter output voltage to establish an output voltage residual error, detecting a fault sensor by comparing the output voltage residual error with a threshold value, and then introducing an observation value of a dual active bridge DC / DC converter sliding mode observer into a feedback channel to replace a fault sensor acquisition value for closed-loop control, so as to realize fault-tolerant control of the dual active bridge DC / DC converter.

8. An electronic device, comprising: The device comprises: a memory storing executable program code; a processor coupled to the memory; the processor invokes the executable program code stored in the memory to execute the steps of the dual active bridge DC / DC converter sensor fault detection and fault-tolerant control method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions, which when invoked, are used to execute the steps of the dual active bridge DC / DC converter sensor fault detection and fault-tolerant control method according to any one of claims 1-6.

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