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

Abstract

The invention discloses a dual-active bridge type DC / DC converter sensor fault detection and fault-tolerant control method, which comprises the following steps: establishing a dual-active bridge type DC / DC converter mathematical model, and designing a dual-active bridge type DC / DC converter load feedforward control method based on current mode modulation; constructing a sliding mode observer of the dual-active bridge type DC / DC converter, and setting parameters of the sliding mode observer; and fault detection is carried out on an output voltage sensor of the dual-active bridge type DC / DC converter, and a fault-tolerant control system is established, so that reliable operation of the dual-active bridge type DC / DC converter is realized. According to the method, the defects that in an existing method, the robust performance is poor, fault-tolerant control implementation is difficult, and a sensor needs to be additionally installed are overcome, and normal work of the dual-active bridge type DC / DC converter under the condition that the output voltage sensor breaks down is ensured.

Description

Technical Field

[0001] The invention relates to the field of power electronic system control, and in particular to a dual-active bridge DC / DC converter sensor fault detection and fault-tolerant control method. Background Art

[0002] The dual-active-bridge (DAB) DC / DC converter has attracted extensive attention from scholars at home and abroad due to its modular symmetrical 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 the power converter system. When the sensor of the dual-active bridge DC / DC converter fails, its output voltage will not be effectively closed-loop controlled, and the failure of the control system will further cause the converter equipment to shut down abnormally. Therefore, it is urgent to design a reasonable control algorithm to perform real-time, online status monitoring of the current / voltage and other states of the running power converter, timely detect system anomalies, diagnose the causes of faults, and actively reconstruct the system control architecture so that the entire system can still operate safely under the original performance indicators or slightly reduced indicators.

[0003] Sensor faults mainly include open circuit faults, gain anomalies, and noise anomalies. Existing power electronic converter fault detection methods are mainly divided into two categories: data-driven methods and model-driven methods. Among them, the former does not require an in-depth understanding of the physical model of the system, but mainly relies on the data set collected from the device, and uses algorithms such as neural networks to discover the associations in the data and then identify the fault mode. The literature (ZYXue, 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 the open-circuit fault of the motor inverter, but the convolutional neural network model requires a large amount of training data, and its performance on low data volume is not outstanding. In addition, the data-driven method is limited to fault diagnosis and cannot provide an effective fault-tolerant control solution for the system. The model-driven method requires an in-depth understanding of the working principle of the system and predicts the behavior of the system by establishing a state observer. Although this type of method relies on physical models, the state observation error caused by inaccurate models can be compensated by utilizing the robustness of the high-performance state observer itself. For example, the 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) designed a current sensor missing fault-tolerant control scheme based on the Luenberger state observer, but this method only uses an error adjustment method based on linear feedback, and the robustness of the observer still needs to be enhanced.

[0004] Through the analysis of existing research results, it can be seen that although the data-driven method does not rely on the system model, it often requires a large amount of data to achieve a high fault diagnosis rate and cannot perform fault-tolerant control on the system; while the model-driven method can automatically and quickly switch the fault sensor acquisition value to the state observation value after the sensor fails to achieve fault-tolerant control, but the robust performance of the existing method has not yet reached the best. Therefore, how to design a sensor fault detection and fault-tolerant control algorithm with strong robustness, low implementation cost and excellent control effect for different fault types has become the key to improving the operating reliability of dual-active bridge DC / DC converters. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to propose a dual-active bridge DC / DC converter sensor fault detection and fault-tolerant control method to ensure that the dual-active bridge DC / DC converter system can operate normally when the voltage sensor fails.

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

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

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

[0009] S3. Perform fault detection on the output voltage sensor of the dual-active bridge DC / DC converter and establish a fault-tolerant control system for 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, detecting the fault sensor by comparing the output voltage residual with a threshold, and then introducing the observation value of the dual-active bridge DC / DC converter sliding mode observer into the feedback channel to replace the fault sensor acquisition value for closed-loop control, thereby achieving fault-tolerant control of the dual-active bridge DC / DC converter.

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

[0011]

[0012] Among them, Q A , Q B , Q C , Q D is the ideal switching function of the four bridge arms, 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 voltage and output voltage respectively, C2 is the secondary side capacitor, i o is the output current.

[0013] Furthermore, 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 instruction value i Lr , generating the switching signal of the secondary bridge, the feedforward control path F f Control Lr , F f The input is the load current i o , Calculated according to the feedforward formula; using a proportional integral PI link feedback control path output compensation, that is, Δi Lr ;i Lr It is expressed as:

[0015]

[0016] will i Lr Defined as the reference value of the inductor current when the secondary voltage of the dual active bridge DC / DC converter is reversed, i L The two sections of the waveform have different slopes M L1 With M L2 It is expressed as:

[0017]

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

[0019]

[0020] Among them, T sw is the switching cycle of the switch tube, i s2 The time domain expression of (t) is:

[0021]

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

[0023]

[0024] Among them, i s2 is the average value of the inductor current in the two sub-intervals, and the sampling frequency f sw =1 / T sw; From the above formula we can get:

[0025]

[0026] Thus we get i Lr with i s2 The relationship between the original feedforward control path F f The expression is:

[0027]

[0028] Among them, the coefficient

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

[0030]

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

[0032] Further, step S2 includes:

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

[0034]

[0035] in, is the observed value of the inductor current, is the output voltage observation value, ρ is the switch term gain, and l1 is the sliding mode observer gain to be designed; subtract the dynamic equation of the sliding mode observer from the mathematical model of the dual active bridge DC / DC converter, and the dynamic equation of the observation error is obtained as follows:

[0036]

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

[0038] Furthermore, 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 determined according to the Lyapunov stability, including:

[0039] Constructing Lyapunov functions To determine the sign of the sliding mode observer gain l1, the time derivative of the Lyapunov function V is obtained:

[0040]

[0041] in, is the time derivative of V, is the time derivative of e1; when hour, At this time, e1=0, Then the dynamic equation of the output voltage observation error is simplified to:

[0042]

[0043] From the above formula, we can see that when l1(Q C -Q D )>0; according to the real-time acquisition of Q C With Q D The switching state determines the sign of the sliding mode observer gain l1.

[0044] Further, step S3 includes:

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

[0046]

[0047] Among them, v or is the output voltage given value, is the output voltage residual;

[0048] Comprehensive consideration of 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 to determine the threshold;

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

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

[0051] 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 dual-active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the output voltage sensor collection value for closed-loop control, thereby realizing fault-tolerant control of the dual-active bridge DC / DC converter until the fault is eliminated.

[0052] Furthermore, when the output voltage residual exceeds the threshold value in five consecutive sampling periods, it is determined that the output voltage sensor fails.

[0053] The system corresponding to the method includes:

[0054] A feedforward control unit is used to establish a mathematical model of a dual active bridge DC / DC converter and design a load current feedforward control of a dual active bridge DC / DC converter based on current mode modulation;

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

[0056] A fault detection and fault-tolerant control unit is used for performing fault detection on an output voltage sensor of a dual-active bridge DC / DC converter and establishing a fault-tolerant control system of a dual-active bridge DC / DC converter; the control system comprises: normalizing the observation error of the output voltage of the dual-active bridge DC / DC converter to establish an output voltage residual, detecting a fault sensor by comparing the output voltage residual with a threshold, and then introducing the observation value of the dual-active bridge DC / DC converter sliding mode observer into a feedback channel to replace the fault sensor acquisition value for closed-loop control, thereby realizing 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 code;

[0059] a processor coupled to the memory;

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

[0061] A computer-readable storage medium for storing and executing the method, wherein the computer-readable storage medium stores computer instructions, and when the computer instructions are called, they are used to execute the steps of the dual-active bridge DC / DC converter fault detection and fault-tolerant control method.

[0062] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows: (1) The dual-active bridge DC / DC converter control scheme designed by the present invention is highly robust. When the load changes suddenly, the system output voltage fluctuates less and can quickly recover to a steady state. (2) The voltage sensor fault detection and fault-tolerant control scheme designed by the present invention has a simple control architecture, does not require a complex calculation process, and is easy to implement. It 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 THE DRAWINGS

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

[0064] Figure 2 It is a topological diagram of the dual active bridge DC / DC converter of the present invention;

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

[0066] Figure 4 The switching signal and the voltage and current waveforms of the dual active bridge DC / DC converter of the present invention when it works normally;

[0067] Figure 5 The figure is a comparison of the simulation experimental results of the load current feedforward control of the present invention and the traditional voltage single closed-loop control, 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 These are the simulation experiment results of the voltage sensor open circuit fault detection and fault-tolerant control of the present invention, where (a) is the simulation result of the output voltage observation value and the fault sensor measurement value, (b) is the simulation result of the output voltage actual value, and (c) is the simulation result of the output voltage residual.

[0069] Figure 7 These are the simulation experimental results of the voltage sensor gain anomaly detection and fault-tolerant control of the present invention, where (a) is the simulation result of the output voltage observation value and the fault sensor measurement value, (b) is the simulation result of the output voltage actual value, and (c) is the simulation result of the output voltage residual.

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

[0071] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0072] like Figure 1 As shown, a dual active bridge DC / DC converter sensor fault detection and fault tolerance control method of the present invention comprises the following steps:

[0073] S1. Establish a mathematical model of a dual-active bridge DC / DC converter and design a load current feedforward control method of a dual-active bridge DC / DC converter based on current mode modulation; specifically:

[0074] The topology of the dual active bridge DC / DC converter is as follows Figure 2 As shown, it consists of three parts: AC / DC converter, transformer and DC / AC converter. According to Kirchhoff's voltage law, we can get:

[0075]

[0076] Among them, 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 divided 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 coil auxiliary inductance and the transformer leakage inductance, i.e. the equivalent inductance; i L is the inductor current.

[0077] Define the ideal switching function Q of the four bridge arms A , Q B , Q C , Q D for:

[0078]

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

[0080] according to Figure 2 Topology, we can get:

[0081]

[0082] Among them, vi and v o are the input voltage and output voltage respectively. Substituting (3) into (1), the voltage equation of the primary side (including transformer and coil auxiliary inductance) of the dual active bridge DC / DC converter is obtained as follows:

[0083]

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

[0085]

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

[0087]

[0088] The load current feedforward (LCFF) control structure block diagram of the dual active bridge DC / DC converter used in the present invention is as follows: Figure 3 As shown, the current modulator receives the measured inductor current i L and instruction value i Lr , generating a switching signal S2 of the secondary bridge, which is realized by 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 , the output value of the feedforward control path It is calculated according to the feedforward formula. In addition, a proportional-integral (PI) link is required to feedback the output compensation of the control path, that is, Δi Lr At this time, i Lr It is expressed as:

[0090]

[0091] Among them, Δi Lr Output compensation for the feedback control path.

[0092] according to Figure 4 , change i Lr Defined as the reference value of the inductor current when the secondary voltage of the dual active bridge DC / DC converter is reversed, iL The two sections of the waveform have different slopes M L1 With M L2 It is expressed as:

[0093]

[0094] Based on the shift angle φ and the above formula, the peak current I0 and the given value of the inductor current i are obtained. Lr Satisfy the following formula:

[0095]

[0096] Among them, T sw is the switching period of the IGBT switch tube. Subtract the two equations in (9) and replace the slope formula M in (8) with L1 、M L2 Substituting in, we get:

[0097]

[0098] For the convenience of derivation, the time t = 0 is defined as Figure 4 In this case, i s2 (t) is expressed as:

[0099]

[0100] In the two subintervals ( and ) and take the average value of the above formula to obtain:

[0101]

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

[0103]

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

[0105]

[0106] Among them, the coefficient

[0107] Original feedforward control path F f The expression consists of two terms, one of which is a nonlinear function Another by v i 、v o 、fsw , k, and L. Since the latter changes much more slowly than the step-change output current, it is removed from the feedforward control path F f is removed from the expression and compensated by the feedback control path. After simplification, the feedforward formula is designed as:

[0108]

[0109] in, is the output value of the feedforward control path, is the average value of the inductor current in the two subintervals.

[0110] S2. Construct a sliding mode observer for a dual active bridge DC / DC converter and adjust the sliding mode observer parameters; specifically:

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

[0112]

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

[0114]

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

[0116] The following is the sign of the sliding mode observer gain l1 based on Lyapunov stability, including:

[0117] Constructing Lyapunov functions To determine the sign of the sliding mode observer gain l1, the time derivative of the Lyapunov function V is obtained:

[0118]

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

[0120] When satisfied hour, At this time, e1=0 Then the dynamic equation of the output voltage observation error is simplified to:

[0121]

[0122] From the above formula, we can see that when l1(Q C -Q D )>0, the sliding mode observer converges. C With Q D The sign of the gain l1 can be determined by the switching state of the

[0123] S3, performing fault detection on the 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 the observation error of the output voltage of the dual-active bridge DC / DC converter to establish an output voltage residual, detecting the fault sensor by comparing the output voltage residual with a threshold, and then introducing the observation value of the dual-active bridge DC / DC converter sliding mode observer into feedback control to replace the fault sensor acquisition value for closed-loop control, thereby realizing fault-tolerant control of the dual-active bridge DC / DC converter; specifically:

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

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

[0126]

[0127] Among them, v or is the output voltage given value, is the output voltage residual.

[0128] Comprehensive consideration of the observation error of the sliding mode observer of the dual active bridge DC / DC converter A 3-fold margin is allowed to establish the threshold value due to the sampling error of the output voltage sensor.

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

[0130] 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, at which time the output voltage sensor fault can be detected.

[0131] In order to reduce the probability of misdiagnosis, the present invention is designed to determine that the sensor is faulty only when the output voltage residual exceeds the threshold value within 5 consecutive sampling cycles.

[0132] 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 dual-active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the output voltage sensor collection value for closed-loop control, thereby realizing fault-tolerant control of the dual-active bridge DC / DC converter until the fault is eliminated.

[0133] A dual active bridge DC / DC converter sensor fault detection and fault tolerance control system of the present invention comprises:

[0134] A feedforward control (LCFF) unit is used to establish a mathematical model of a dual-active bridge DC / DC converter and design a load current feedforward control of a dual-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 dual-active bridge DC / DC converter system; specifically, the input voltage, output voltage, and inductor current of the dual-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 dual-active bridge DC / DC converter, construct the sliding mode observer of the dual-active bridge DC / DC converter, and set the parameters of the sliding mode observer; specifically: design the sliding mode observer of the output voltage of the dual-active bridge DC / DC converter, construct the Lyapunov function based on the quadratic form of the output voltage observation error, and obtain the sign and lower limit of the coefficient of the switching function term of the sliding mode observer by scaling its time derivative;

[0136] A fault detection and fault-tolerant control unit is used to detect the output voltage sensor fault of the dual-active bridge DC / DC converter and establish a fault-tolerant control system; specifically: the observation error of the output voltage of the dual-active bridge DC / DC converter is normalized to establish the output voltage residual, the fault sensor is detected by comparing the output voltage residual with a threshold, and then the observation value of the dual-active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the fault sensor acquisition value for closed-loop control, thereby realizing fault-tolerant control of the dual-active bridge DC / DC converter.

[0137] An electronic device of the present invention comprises:

[0138] A memory storing executable program code;

[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 above-mentioned dual-active bridge DC / DC converter sensor fault detection and fault-tolerant control method.

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

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

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

[0144] In the simulation experiment, a load mutation is introduced at t = 0.1s, and the equivalent load resistance is switched from 1Ω to 0.5Ω. The simulation results of the dual active bridge DC / DC converter system startup process and load mutation are shown in Figure 2. Figure 5 As shown in (a) and (b). At t = 0.2s, the voltage sensor open circuit fault, gain anomaly, and noise anomaly are introduced respectively, and the simulation results are as follows Figure 6 (a), (b) and (c), Figure 7 (a), (b) and (c), Figure 8 As shown in (a), (b) and (c). Figure 5 It can be seen from (a) and (b) that the secondary output voltage of the traditional single closed-loop voltage control drops by about 4V under load mutation, and the output voltage recovers to the given value of 28V after about 0.025s of adjustment time; while the LCFF control adopted by the present invention has stronger robustness and anti-load disturbance capability, and the secondary output voltage drops by only 0.1V under load mutation, and the adjustment time is shortened to 0.005s. Figure 6 (a), (b) and (c), Figure 7 (a), (b) and (c), Figure 8It can be seen from (a), (b) and (c) that the designed sliding mode observer can achieve accurate observation of the output voltage before and after the introduction of load disturbance. When the voltage sensor fails, the voltage residual exceeds the threshold after 5 sampling cycles, which means that the sensor failure is detected; due to the implementation of fault-tolerant control, the observation value of the dual-active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the fault sensor acquisition value for closed-loop control. Therefore, the actual output voltage is not affected by the sensor failure and remains stable at 28V, which proves the effectiveness of the dual-active bridge DC / DC converter sensor fault diagnosis and fault-tolerant control strategy proposed in this invention.

Claims

1. A dual active bridge DC / DC converter sensor fault detection and fault tolerance control method, characterized in that: The following steps are involved: S1. Establish a mathematical model of a dual-active bridge DC / DC converter and design a load current feedforward control method for the dual-active bridge DC / DC converter based on current mode modulation; S2, construct a sliding mode observer for a dual active bridge DC / DC converter and set the sliding mode observer parameters; S3. Perform fault detection on the output voltage sensor of the dual-active bridge DC / DC converter and establish a fault-tolerant control system for 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, detecting the fault sensor by comparing the output voltage residual with a threshold, and then introducing the observation value of the dual-active bridge DC / DC converter sliding mode observer into the feedback channel to replace the fault sensor acquisition value for closed-loop control, thereby achieving fault-tolerant control of the dual-active bridge DC / DC converter.

2. The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method according to claim 1, characterized in that: The mathematical model of the dual active bridge DC / DC converter in step S1 is: Among them, Q A , Q B , Q C , Q D is the ideal switching function of the four bridge arms, L is the sum of the inductor coil and the transformer leakage inductance, that is, the equivalent inductance; i L is the inductor current, k is the transformer ratio, v i and v o are the input voltage and output voltage respectively, C2 is the secondary side capacitor, i o is the output current.

3. The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method according to claim 1, characterized in that: The load feedforward control of the dual active bridge DC / DC converter based on current mode modulation in step S1 is: The current modulator receives the measured inductor current i L and instruction value i Lr , generating the switching signal of the secondary bridge, the feedforward control path F f Control Lr , F f The input is the load current i o , Calculated according to the feedforward formula; The output compensation of the feedback control path using a proportional integral PI link, that is, Δi Lr ;i Lr It is expressed as: will i Lr Defined as the reference value of the inductor current when the secondary voltage of the dual active bridge DC / DC converter is reversed, i L The two sections of the waveform have different slopes M L1 With M L2 It is expressed as: Based on the shift angle φ and the above formula, the given value of the inductor current i is obtained. Lr satisfy: Among them, T sw is the switching cycle of the switch tube, i s2 The time domain expression of (t) is: Taking the average of the above formula in the two subintervals, we get: in, is the average value of the inductor current in the two sub-intervals, and the sampling frequency f sw =1 / T sw ; From the above formula we can get: Thus we get i Lr and The relationship between the original feedforward control path F f The expression is: Among them, the coefficient Original feedforward control path F f The expression consists of two terms, one of which is a nonlinear function Another by v i 、v o 、f sw , k, L, since the latter changes much slower than the step-change output current, it is removed from the feedforward control path F f is removed from the expression and compensated by the feedback control path; after simplification, the feedforward control path expression is designed as: in, is the output value of the feedforward control path.

4. The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method according to claim 1, characterized in that: Step S2 includes: According to the mathematical model of the dual-active bridge DC / DC converter, with the output voltage as the goal, the dynamic equation of the sliding mode observer of the dual-active bridge DC / DC converter is designed as follows: in, is the observed value of the inductor current, is the output voltage observation value, ρ is the switch term gain, and l1 is the sliding mode observer gain to be designed; subtract the dynamic equation of the sliding mode observer from the mathematical model of the dual active bridge DC / DC converter, and the dynamic equation of the observation error is obtained as follows: Where e1 and e2 are the observed errors of the inductor current and output voltage, respectively. and are the time derivatives of the observed errors of the inductor current and output voltage, respectively.

5. The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method according to claim 4, characterized in that: 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 determined according to the Lyapunov stability, including: Constructing Lyapunov functions To determine the sign of the sliding mode observer gain l1, the time derivative of the Lyapunov function V is obtained: in, is the time derivative of V, is the time derivative of e1; when hour, At this time, e1=0, Then the dynamic equation of the output voltage observation error is simplified to: From the above formula, we can see that when l1(Q C -Q D )>0, the sliding mode observer converges; according to the real-time acquisition of Q C With Q D The switching state determines the sign of the sliding mode observer gain l1.

6. The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method according to claim 1, characterized in that: Step S3 includes: The observation error of the output voltage of the dual active bridge DC / DC converter is normalized, and the residual is established by dividing the absolute value of the observation error of the dual active bridge DC / DC converter sliding mode observer by the output voltage given value. The specific calculation method is: Among them, v or is the output voltage given value, is the output voltage residual; Comprehensive consideration of 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 to determine the threshold; When the dual active bridge DC / DC converter output voltage sensor does not fail, the resulting output voltage residual will always be below the threshold; When the output voltage sensor of the dual active bridge DC / DC converter has an open circuit fault, sensor gain abnormality or noise abnormality, the output voltage residual will increase and exceed the threshold, at which time the output voltage sensor fault 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 dual-active bridge DC / DC converter sliding mode observer is introduced into the feedback channel to replace the output voltage sensor collection value for closed-loop control, thereby realizing fault-tolerant control of the dual-active bridge DC / DC converter until the fault is eliminated.

7. The dual active bridge DC / DC converter sensor fault detection and fault tolerance control method according to claim 6, characterized in that: When the output voltage residual exceeds the threshold value for five consecutive sampling cycles, it is determined that the output voltage sensor is faulty.

8. A dual active bridge DC / DC converter fault detection and fault tolerance control system, characterized in that: include: A feedforward control unit is used to establish a mathematical model of a dual active bridge DC / DC converter and design a load current feedforward control method of a dual active bridge DC / DC converter based on current mode modulation; The sliding mode observer and parameter setting unit is used to construct a sliding mode observer of a dual active bridge DC / DC converter and to set the sliding mode observer parameters. A fault detection and fault-tolerant control unit is used for performing fault detection on an output voltage sensor of a dual-active bridge DC / DC converter and establishing a fault-tolerant control system of a dual-active bridge DC / DC converter; the control system comprises: normalizing the observation error of the output voltage of the dual-active bridge DC / DC converter to establish an output voltage residual, detecting a fault sensor by comparing the output voltage residual with a threshold, and then introducing the observation value of the dual-active bridge DC / DC converter sliding mode observer into a feedback channel to replace the fault sensor acquisition value for closed-loop control, thereby realizing fault-tolerant control of the dual-active bridge DC / DC converter.

9. An electronic device, characterized in that: The device comprises: A memory storing executable program code; a processor coupled to the memory; The processor calls 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 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, which, when called, are used to execute the steps of the dual-active bridge DC / DC converter sensor fault detection and fault-tolerant control method described in any one of claims 1 to 7.

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