Energy storage battery temperature measuring branch fault diagnosis system

Abstract

The application provides a kind of energy storage battery temperature measuring branch fault diagnosis system, belong to battery monitoring technical field, wherein, temperature measuring branch includes sampling resistance, thermistor and capacitor C1, controller is configured to output original excitation signal to the input end of signal conditioning circuit at preset time point, signal conditioning circuit is configured to condition original excitation signal, output unipolar sinusoidal excitation signal, the output end of signal conditioning circuit is connected with the first end of temperature measuring branch, the second end of temperature measuring branch is grounded;First voltage acquisition circuit is configured to acquire the voltage signal at the two ends of sampling resistance, second voltage acquisition circuit is configured to acquire the voltage signal at the two ends of temperature measuring branch, the output end of first voltage acquisition circuit and the output end of second voltage acquisition circuit are respectively connected to two analog sampling channels of controller.This application can improve the reliability of energy storage battery temperature measuring branch.

Description

Technical Field

[0001] This application belongs to the field of battery monitoring technology, and more specifically, relates to a fault diagnosis system for the temperature measurement branch of an energy storage battery. Background Technology

[0002] In energy storage systems, the Battery Management Unit (BMU) typically monitors the voltage and temperature of the battery cells in the battery pack in real time and transmits this information to upper-level devices. During charging and discharging, the battery temperature generally rises due to internal chemical reactions. The upper-level devices adjust the cooling system based on the cell temperature information monitored by the BMU to prevent overheating that could lead to battery explosion or fire. Therefore, cell temperature monitoring is a crucial and essential aspect of energy storage systems.

[0003] The battery cells in the battery pack are connected in series through a Cell Contact System (CCS). The CCS has voltage sampling points for each cell soldered on it, as well as NTC probes for temperature measurement. Voltage and temperature sampling lines are led out of the battery pack via wiring harnesses and connected to the BMU via terminals. The NTC temperature probes reflect the temperature at each measurement point through their resistance (NTC: higher impedance indicates lower temperature). Figure 1 As shown, in the existing battery temperature monitoring circuit, the NTC is soldered inside the probe and connected in series with resistor R1 on the BMU. The BMU collects the voltage drop across resistor R1 through the analog sampling channel (Analog-to-Digital Converter, ADC) and then calculates the resistance value of the NTC. The temperature measured at the probe can then be obtained by looking up the R-℃ correspondence table provided by the NTC manufacturer.

[0004] In field applications, due to long-term operation, the terminals in the NTC temperature measurement branch are prone to aging or loose connection, introducing unknown resistance into the temperature measurement circuit. This causes the BMU to be unable to collect the correct NTC voltage, thus failing to calculate the temperature of the measurement point correctly, resulting in false alarms from the BMU. Summary of the Invention

[0005] The purpose of this application is to provide a fault diagnosis system for the temperature measurement branch of an energy storage battery, so as to solve the problem that faults in the temperature measurement branch of an energy storage battery can lead to false temperature alarms, and improve the reliability of the temperature measurement branch of the energy storage battery.

[0006] The technical solutions provided in this application are as follows: A fault diagnosis system for a temperature measurement branch of an energy storage battery, wherein the temperature measurement branch includes a sampling resistor, a thermistor, and a capacitor C1, wherein the first end of the sampling resistor is the first end of the temperature measurement branch, the second end of the sampling resistor is connected to the first end of the thermistor, the second end of the thermistor is the second end of the temperature measurement branch, and the capacitor C1 is connected in parallel across the thermistor; the fault diagnosis system includes a controller, a signal conditioning circuit, a first voltage acquisition circuit, and a second voltage acquisition circuit; The controller is configured to output the original excitation signal to the input terminal of the signal conditioning circuit at a preset time point. The signal conditioning circuit is configured to condition the original excitation signal and output a unipolar sinusoidal excitation signal. The output terminal of the signal conditioning circuit is connected to the first terminal of the temperature measuring branch, and the second terminal of the temperature measuring branch is grounded. The first voltage acquisition circuit is configured to acquire the voltage signal across the sampling resistor, and the second voltage acquisition circuit is configured to acquire the voltage signal across the temperature measurement branch. The output of the first voltage acquisition circuit is connected to the first analog sampling channel of the controller, and the output of the second voltage acquisition circuit is connected to the second analog sampling channel of the controller. The controller is also configured to: The current signal of the temperature measuring branch is calculated based on the voltage signal across the sampling resistor and the resistance value of the sampling resistor. The complex impedance of the temperature measuring branch is calculated based on the voltage signal at both ends of the temperature measuring branch and the current signal of the temperature measuring branch; the complex impedance includes a real part and an imaginary part of the impedance. The resistance of the thermistor is calculated based on the imaginary part of the impedance, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal. The contact resistance of the temperature measuring branch is calculated based on the real part of the impedance, the resistance value of the thermistor, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal. Based on the relative magnitude of the contact resistance and the preset impedance threshold, the fault diagnosis result of the temperature measurement branch is determined.

[0007] In one embodiment of this application, when calculating the resistance value of the thermistor based on the imaginary part of the impedance, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal, the controller is configured to: The resistance of the thermistor is calculated using the following first formula: ; in, This indicates the resistance value of the thermistor. Represents the imaginary part of the impedance. This represents the frequency of the unipolar sinusoidal excitation signal. This indicates the capacitance value of capacitor C1.

[0008] In one embodiment of this application, when calculating the contact resistance of the temperature sensing branch based on the real part of the impedance, the resistance value of the thermistor, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal, the controller is configured to: The contact resistance of the temperature measuring branch is calculated using the following second formula: ; in, This indicates the contact resistance of the temperature measuring branch. Represents the real part of the impedance. This indicates the resistance value of the sampling resistor RS. This indicates the resistance value of the thermistor. This represents the frequency of the unipolar sinusoidal excitation signal. This indicates the capacitance value of capacitor C1.

[0009] In one embodiment of this application, when calculating the complex impedance of the temperature sensing branch based on the voltage signal across the temperature sensing branch and the current signal of the temperature sensing branch, the controller is configured to: Digital phase-sensitive demodulation is performed on the voltage signal at both ends of the temperature measuring branch and the current signal of the temperature measuring branch to obtain the voltage in-phase component and voltage quadrature component of the voltage signal at both ends of the temperature measuring branch, and the current in-phase component and current quadrature component of the current signal. The complex impedance of the temperature measuring branch is obtained by performing complex impedance calculations based on the in-phase voltage component, the quadrature voltage component, the in-phase current component, and the quadrature current component.

[0010] In one embodiment of this application, the original excitation signal is a PWM signal, and the signal conditioning circuit includes a low-pass filter circuit and an adder circuit connected in sequence. The input terminal of the low-pass filter circuit is the input terminal of the signal conditioning circuit. The output terminal of the low-pass filter circuit is connected to the first input terminal of the adder circuit. The second input terminal of the adder circuit is connected to the bias voltage. The output terminal of the adder circuit is the output terminal of the signal conditioning circuit.

[0011] In one embodiment of this application, the first voltage acquisition circuit includes resistors R9, R10, and R11, and operational amplifier U2C; The first end of the resistor R10 is connected to the first end of the sampling resistor, and the second end of the resistor R10 is connected to the non-inverting input of the operational amplifier U2C. The first end of the resistor R9 is connected to the second end of the sampling resistor, and the second end of the resistor R9 is connected to the inverting input terminal of the operational amplifier U2C. The output terminal of the operational amplifier U2C is fed back to the inverting input terminal of the operational amplifier U2C through the resistor R11; The output terminal of the operational amplifier U2C is the output terminal of the first voltage acquisition circuit.

[0012] In one embodiment of this application, the second voltage acquisition circuit includes resistor RF1, resistor RF2, and a first subtraction circuit; The first end of the resistor RF1 is connected to the first end of the temperature measuring branch, and the second end of the resistor RF1 is connected to the second end of the temperature measuring branch through the resistor RF2. The two ends of the resistor RF2 are respectively connected to the two input terminals of the first subtraction circuit, and the output terminal of the first subtraction circuit is the output terminal of the second voltage acquisition circuit.

[0013] In one embodiment of this application, the fault diagnosis system for the temperature measurement branch of the energy storage battery further includes a DC bias circuit, which includes a resistor R23 and a resistor R24. The first end of the resistor R23 is connected to a DC power supply, and the second end of the resistor R23 is grounded through the resistor R24. The second end of the resistor R23 serves as the bias voltage.

[0014] In one embodiment of this application, the preset impedance threshold includes a first impedance threshold and a second impedance threshold, and the first impedance threshold is less than the second impedance threshold; Specifically, when determining the fault diagnosis result of the temperature measurement branch based on the relative magnitude of the contact resistance and a preset impedance threshold, the controller is configured as follows: If the contact resistance is greater than or equal to a preset first impedance threshold and less than a preset second impedance threshold, then a first fault alarm message is output. If the contact resistance is greater than or equal to a preset second impedance threshold, a second fault alarm message is output; the severity of the second fault alarm message is greater than the severity of the first fault alarm message.

[0015] In one embodiment of this application, the fault diagnosis system for the temperature measurement branch of the energy storage battery further includes a resistor R1, a first switch, a second switch, and a third switch; The first end of the resistor R1 is connected to the DC power supply, and the second end of the resistor R1 is connected to the first end of the temperature measuring branch through the first switch. The first end of the second switch is connected to the first end of the temperature measuring branch, and the second end of the second switch is connected to the third analog sampling channel of the controller; The third switch is connected in series in the second voltage acquisition circuit; The control terminals of the first switch, the second switch, and the third switch are respectively connected to the controller.

[0016] The beneficial effects of the technical solution provided in this application are as follows: In this embodiment, the controller outputs the original excitation signal to the input of the signal conditioning circuit at a preset time point. After filtering and level adjustment by the signal conditioning circuit, a unipolar sinusoidal excitation signal is output to the temperature measuring branch. The controller also acquires the voltage signal across the sampling resistor through the first voltage acquisition circuit and the voltage signal across the temperature measuring branch through the second voltage acquisition circuit. Based on this, the controller can determine the current signal of the temperature measuring branch according to the voltage signal across the sampling resistor. Based on the voltage signal and current signal of the temperature measuring branch, the controller calculates the complex impedance of the temperature measuring branch. The complex impedance can be separated into the real part and the imaginary part of the impedance. Taking advantage of the fact that the imaginary part of the impedance is independent of the contact resistance, the resistance value of the thermistor is first calculated from the imaginary part of the impedance. Then, the calculated resistance value of the thermistor is substituted into the expression of the real part of the impedance to calculate the contact resistance of the temperature measuring branch.

[0017] The magnitude of the contact resistance can be used to determine whether there is aging or loose connection fault in the temperature sensing branch, enabling timely detection of temperature sensing branch faults, thereby avoiding false temperature alarms caused by temperature sensing branch faults and improving the reliability of the temperature sensing branch of the energy storage battery. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below.

[0019] Figure 1 This is a schematic diagram of an existing battery temperature monitoring circuit. Figure 2 A schematic diagram of a fault diagnosis system for the temperature measurement branch of an energy storage battery provided in an embodiment of this application; Figure 3 A schematic diagram illustrating the calculation process of contact resistance provided in an embodiment of this application; Figure 4 A schematic diagram of the signal conditioning circuit provided in an embodiment of this application; Figure 5 A schematic diagram of the first voltage acquisition circuit provided in an embodiment of this application; Figure 6 A schematic diagram of the first subtraction circuit provided in an embodiment of this application; Figure 7 The schematic diagram is of the DC bias circuit provided in the embodiments of this application. Detailed Implementation

[0020] The embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the embodiments described below with reference to the accompanying drawings are exemplary descriptions for explaining the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions of the embodiments of this application.

[0021] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the terms “comprising” and “including” as used in embodiments of this application mean that the corresponding feature can be implemented as the presented feature, information, data, step, operation, element, and / or component, but do not exclude implementation as other features, information, data, step, operation, element, component, and / or combinations thereof supported by the art. It should be understood that when we say that an element is “connected” or “coupled” to another element, the one element can be directly connected or coupled to the other element, or it can mean that the one element and the other element establish a connection relationship through an intermediate element. Furthermore, “connected” or “coupled” as used herein can include wireless connection or wireless coupling. The term “and / or” as used herein indicates at least one of the items defined by the term; for example, “A and / or B” can be implemented as “A,” or as “B,” or as “A and B.” When describing multiple (two or more) items, if the relationship between the multiple items is not explicitly defined, the multiple items can refer to one, several or all of the multiple items. For example, the description of "parameter A includes A1, A2, A3" can be implemented as parameter A includes A1 or A2 or A3, or it can be implemented as parameter A includes at least two of the three items A1, A2 and A3.

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0023] like Figure 2 As shown in the figure, this application embodiment provides a fault diagnosis system for the temperature measurement branch of an energy storage battery. The temperature measurement branch includes a sampling resistor RS, a thermistor RT, and a capacitor C1. The first terminal of the sampling resistor RS is the first terminal of the temperature measurement branch (denoted as A in the network). The second terminal of the sampling resistor RS (denoted as C in the network) is connected to the first terminal of the thermistor RT. The second terminal of the thermistor RT is the second terminal of the temperature measurement branch (denoted as B in the network). The capacitor C1 is connected in parallel across the thermistor RT. The fault diagnosis system includes a controller, a signal conditioning circuit, a first voltage acquisition circuit, and a second voltage acquisition circuit. The controller is configured to output the original excitation signal to the input of the signal conditioning circuit at a preset time point. The signal conditioning circuit is configured to condition the original excitation signal and output a unipolar sinusoidal excitation signal. The output of the signal conditioning circuit is connected to the first end of the temperature measurement branch, and the second end of the temperature measurement branch is grounded. The first voltage acquisition circuit is configured to acquire the voltage signal across the sampling resistor RS, and the second voltage acquisition circuit is configured to acquire the voltage signal across the temperature measurement branch. The output of the first voltage acquisition circuit is connected to the first analog sampling channel AD1 of the controller, and the output of the second voltage acquisition circuit is connected to the second analog sampling channel AD2 of the controller.

[0024] In this embodiment, a temperature measurement branch (energy storage battery) is formed by a sampling resistor RS, a thermistor RT, and a capacitor C1. The resistor in the temperature measurement branch... This indicates the contact resistance caused by aging or loose connections at the terminals in the temperature sensing branch. The controller can be a microcontroller unit (MCU) within the battery management system. The preset time point can be a time point set according to a fixed timing period (e.g., 1 hour) or a time point manually triggered by the user. At the preset time point, the controller outputs the raw excitation signal to the input of the signal conditioning circuit. After filtering and level adjustment by the signal conditioning circuit, a unipolar sinusoidal excitation signal (without negative voltage) is output to the temperature sensing branch. The first voltage acquisition circuit acquires the voltage signal across the sampling resistor RS, and the second voltage acquisition circuit acquires the voltage signal across the temperature sensing branch. Based on this, the controller can calculate the contact resistance. Therefore, based on contact resistance The size of the temperature measurement branch indicates whether it is aging or has a loose connection.

[0025] Specifically, such as Figure 3 As shown, contact resistance The calculation process includes the following steps S101-S104: S101: Calculate the current signal of the temperature measurement branch based on the voltage signal across the sampling resistor RS and the resistance value of the sampling resistor RS.

[0026] In this embodiment, the sampling resistor RS can be a precision resistor, such as a resistor with an accuracy range of ±0.5% or ±0.1% and a resistance value on the order of several ohms. The sampling resistor RS is connected in series in the temperature measurement branch. Therefore, the current signal of the temperature measurement branch can be obtained by dividing the voltage signal across the sampling resistor RS by the resistance value of the sampling resistor RS.

[0027] S102: Calculate the complex impedance of the temperature measuring branch based on the voltage signal at both ends of the temperature measuring branch and the current signal of the temperature measuring branch; the complex impedance includes the real part and the imaginary part of the impedance.

[0028] In this embodiment, the impedance of the temperature measuring branch can be obtained by dividing the voltage signal across the two ends of the temperature measuring branch by the current signal of the temperature measuring branch. Since the thermistor RT is connected in parallel with the capacitor C1, a capacitive reactance component will be generated. Therefore, the impedance of the temperature measuring branch is a complex impedance.

[0029] For example, the calculation process for complex impedance includes: Digital phase-sensitive demodulation is performed on the voltage signal at both ends of the temperature measuring branch and the current signal of the temperature measuring branch to obtain the voltage in-phase component and voltage quadrature component of the voltage signal at both ends of the temperature measuring branch, as well as the current in-phase component and current quadrature component of the current signal. Complex impedance calculations are performed based on the in-phase voltage component, the quadrature voltage component, the in-phase current component, and the quadrature current component to obtain the complex impedance of the temperature measurement branch.

[0030] In this embodiment, the controller can first generate two orthogonal reference signals with the same frequency as the unipolar sinusoidal excitation signal. Then, based on the two orthogonal reference signals, the controller performs quadrature phase-locked demodulation on the sampling sequence of the acquired voltage signal to extract the voltage in-phase component and voltage quadrature component with the same frequency as the unipolar sinusoidal excitation signal. At the same time, based on the two orthogonal reference signals, the controller performs quadrature phase-locked demodulation on the sampling sequence of the acquired current signal to extract the current in-phase component and current quadrature component with the same frequency as the unipolar sinusoidal excitation signal.

[0031] Assume the frequency of the unipolar sinusoidal excitation signal is Discrete time is The sampling period is The unipolar sinusoidal excitation signal is The two orthogonal reference signals are: The sampling sequence of the voltage signal is The sampling sequence of the current signal is The sampling sequence of the voltage signal Subtracting the average value over the entire period yields the voltage sampling sequence after DC stripping. The sampling sequence of the current signal Subtracting the average value over the entire cycle yields the current sampling sequence after DC stripping. The formula is expressed as follows: ; in, This represents the average value over an entire period of the voltage signal. This represents the average value over an entire cycle of the current signal.

[0032] Furthermore, the voltage sampling sequence can be processed using the following formula. and current sampling sequence Perform quadrature phase-locked demodulation: ; in, Indicates the in-phase component of the voltage. Represents the orthogonal components of voltage. Indicates the in-phase component of the current. This represents the orthogonal components of the current.

[0033] Furthermore, complex voltages can be constructed. and complex current as follows: ; Furthermore, it is possible to base it on complex voltages and complex current Calculate complex impedance : (1) in, Represents the real part of the impedance. This represents the imaginary part of the impedance.

[0034] S103: Calculate the resistance of the thermistor RT based on the imaginary part of the impedance, the capacitance of capacitor C1, and the frequency of the unipolar sinusoidal excitation signal, and calculate the contact resistance of the temperature measuring branch based on the real part of the impedance, the resistance of the thermistor RT, the capacitance of capacitor C1, and the frequency of the unipolar sinusoidal excitation signal.

[0035] according to Figure 2 It can be seen that the capacitor C1 and the thermistor RT are connected in parallel, and their parallel impedance is: ; in, This represents the parallel impedance of capacitor C1 and thermistor RT. This indicates the resistance value of the thermistor RT. This represents the frequency of the unipolar sinusoidal excitation signal. This indicates the capacitance value of capacitor C1.

[0036] Therefore, the total impedance of the temperature measurement branch is: ; in, This represents the total impedance of the temperature measurement branch. This indicates the contact resistance of the temperature measuring branch. This indicates the resistance value of the sampling resistor RS.

[0037] Separating the real and imaginary parts of the above equation, we get: ; The real and imaginary parts obtained by separation are respectively equal to the real part of the impedance calculated by the above formula (1). and the imaginary part of impedance Therefore, we get: (2) (3) and All of these are known constants; therefore, according to formula (3), we can obtain: (4) Substituting formula (4) into formula (2), we get: ; This completes the measurement of the contact resistance of the temperature measurement branch. The calculation.

[0038] S104: Determine the fault diagnosis result of the temperature measurement branch based on the relative magnitude of the contact resistance and the preset impedance threshold.

[0039] In this embodiment, an impedance threshold can be preset based on empirical values, when the contact resistance... When the impedance exceeds the preset threshold, it indicates that the temperature measurement branch has faults such as aging or loose connection.

[0040] Furthermore, considering that the contact resistance of the temperature sensing branch gradually increases with the degree of fault deterioration, two levels of impedance thresholds can be set to achieve graded fault alarms. For example, a first impedance threshold (e.g., 80mΩ) and a second impedance threshold (e.g., 250mΩ) can be set separately. Based on these, two levels of fault alarms can be implemented according to the first and second impedance thresholds. Specifically, if the contact resistance is greater than or equal to the preset first impedance threshold and less than the preset second impedance threshold, a slight contact abnormality is determined to have occurred in the temperature sensing branch, and the controller outputs a first fault alarm message to remind maintenance personnel to perform routine inspections; if the contact resistance is greater than the second impedance threshold, a loose connection or severe aging fault in the temperature sensing branch is determined to have occurred, and the controller outputs a second fault alarm message to remind maintenance personnel to handle the situation promptly.

[0041] As can be seen from the above, in this embodiment, the controller outputs the original excitation signal to the input terminal of the signal conditioning circuit at a preset time point. After filtering and level adjustment by the signal conditioning circuit, a unipolar sinusoidal excitation signal is output to the temperature measuring branch. The voltage signal across the sampling resistor RS is acquired by the first voltage acquisition circuit, and the voltage signal across the temperature measuring branch is acquired by the second voltage acquisition circuit. Accordingly, the controller can determine the current signal of the temperature measuring branch based on the voltage signal across the sampling resistor RS. Based on the voltage signal across the temperature measuring branch and the current signal of the temperature measuring branch, the complex impedance of the temperature measuring branch is calculated. The complex impedance can be separated into the real part and the imaginary part of the impedance. Taking advantage of the fact that the imaginary part of the impedance is independent of the contact resistance, the resistance value of the thermistor RT is first calculated from the imaginary part of the impedance. Then, the calculated resistance value of the thermistor RT is substituted into the expression of the real part of the impedance to calculate the contact resistance of the temperature measuring branch. .

[0042] Based on contact resistance The magnitude of the temperature measurement signal can determine whether there is aging or loose connection fault in the temperature measurement branch, enabling timely detection of temperature measurement branch faults, thereby avoiding false temperature alarms caused by temperature measurement branch faults and improving the reliability of the temperature measurement branch of the energy storage battery.

[0043] In one embodiment of this application, the original excitation signal is a PWM signal, such as... Figure 4 As shown, the signal conditioning circuit includes a low-pass filter circuit and an adder circuit connected in sequence; The input terminal of the low-pass filter circuit is the input terminal of the signal conditioning circuit. The first input terminal of the adder circuit is connected to the output terminal of the low-pass filter circuit. The second input terminal of the adder circuit is connected to the bias voltage VREF. The output terminal of the adder circuit is the output terminal of the signal conditioning circuit.

[0044] In this embodiment, the controller can output a PWM signal as the original excitation signal through the built-in PWM module. According to the principle of pulse width modulation, in one carrier cycle of the PWM signal, the area enclosed by the PWM rectangular pulse voltage is equal to the area enclosed by the sine wave in the same time period. Therefore, the average voltage of the PWM rectangular pulse in one carrier cycle is equal to the instantaneous voltage of the sine wave. Thus, by setting the pulse width of the PWM signal to change periodically with the sine curve, the PWM signal can be filtered out by a low-pass filter circuit to remove high-order harmonics, resulting in a sine wave signal. Furthermore, to avoid distortion at the bottom of the sine wave signal, the sine wave signal is connected to the first input terminal of the adder circuit and superimposed with the bias voltage VREF to boost the voltage of the sine wave signal. The boosted sine wave signal is then used as the unipolar sine excitation signal signalal.

[0045] The low-pass filter circuit can be a second-order low-pass filter circuit, such as... Figure 4As shown, resistor R2 and capacitor C5 form a first-order RC low-pass filter circuit, and resistor R4 and capacitor C6 form a second-order RC low-pass filter circuit. Combined with operational amplifier U2A, this forms an active second-order low-pass filter circuit. Utilizing the low output impedance of the operational amplifier, the load-carrying capacity of the output signal can be enhanced, avoiding signal distortion. Furthermore, the specific model of operational amplifier U2A can be LM224, with pin 2 being the inverting input, pin 3 the non-inverting input, and pin 1 the output.

[0046] The adder circuit consists of resistors R6, R7, R8, and R26, and operational amplifier U2B. The specific model of operational amplifier U2B can be LM224. The first terminals of resistors R6 and R26 are the two input terminals of the adder circuit. The second terminals of both resistors R6 and R26 are connected to the non-inverting input (pin 5) of operational amplifier U2B. The inverting input of operational amplifier U2B is pin 6, and the output is pin 7. Depending on the actual needs, the amplification factor of the adder circuit can be adjusted by adjusting the values ​​of resistors R7 and R8, thereby adjusting the output voltage of the signal conditioning circuit. Resistors R6 and R26 mainly serve as impedance matching resistors.

[0047] like Figure 5 As shown, in one embodiment of this application, the first voltage acquisition circuit includes resistors R9, R10, and R11, and operational amplifier U2C. The first end of resistor R10 is connected to the first end of the sampling resistor, and the second end of resistor R10 is connected to the non-inverting input of operational amplifier U2C. The first end of resistor R9 is connected to the second end of the sampling resistor, and the second end of resistor R9 is connected to the inverting input of operational amplifier U2C; The output of op-amp U2C is fed back to the inverting input of op-amp U2C through resistor R11; The output terminal of op-amp U2C is the output terminal of the first voltage acquisition circuit.

[0048] In this embodiment, resistors R9, R10, and R11, along with operational amplifier U2C, constitute the second subtraction circuit. The first terminals of resistors R10 and R9 are the two input terminals of the second subtraction circuit, respectively. The two terminals of the sampling resistor RS are connected to the two input terminals of the second subtraction circuit. The second subtraction circuit outputs the voltage across the sampling resistor RS to the analog sampling channel AD1 of the controller. The controller reads the data from the analog sampling channel AD1 to obtain the voltage across the sampling resistor RS. Furthermore, the operational amplifier U2C can be an LM224, with pin 9 as the inverting input, pin 10 as the non-inverting input, and pin 8 as the output.

[0049] Depending on actual needs, the amplification factor of the second subtraction circuit can be adjusted by adjusting the resistance values ​​of resistors R9 and R11, thereby conditioning the output voltage of the first voltage acquisition circuit to a preset range (e.g., 0~3.3V) for accurate reading by the controller.

[0050] like Figure 2 As shown, in one embodiment of this application, the second voltage acquisition circuit includes resistor RF1, resistor RF2, and a first subtraction circuit; The first end of resistor RF1 is connected to the first end of the temperature measuring branch, and the second end of resistor RF1 is connected to the second end of the temperature measuring branch through resistor RF2. The two ends of resistor RF2 are connected to the two input terminals of the first subtraction circuit, and the output terminal of the first subtraction circuit is the output terminal of the second voltage acquisition circuit.

[0051] In this embodiment, resistors RF1 and RF2 form a resistor voltage divider circuit, which is connected in parallel across the temperature measuring branch. The voltage across resistor RF2 is proportional to the voltage across the temperature measuring branch. Therefore, the voltage across the temperature measuring branch can be obtained by detecting the voltage across resistor RF2.

[0052] Specifically, the two ends of resistor RF2 ( Figure 2 RF2_1 and RF2_2 are respectively connected to the two input terminals of the first subtraction circuit. The voltage across the output resistor RF2 of the first subtraction circuit is sent to the analog sampling channel AD2 of the controller. The controller can obtain the voltage across the temperature measurement branch by reading the data of the analog sampling channel AD2.

[0053] Among them, such as Figure 6 As shown, the first subtraction circuit consists of resistors R21, R22, and R16, and operational amplifier U3A. The specific model of operational amplifier U3A can be LM224. The first terminal of resistor R22 is the first input terminal of the first subtraction circuit, and the second terminal of resistor R22 is connected to the non-inverting input terminal (pin 3) of operational amplifier U3A. The first terminal of resistor R21 is the second input terminal of the first subtraction circuit, and the second terminal of resistor R21 is connected to the inverting input terminal (pin 2) of operational amplifier U3A. Resistor R16 is the negative feedback resistor. Depending on actual needs, by adjusting the resistance values ​​of resistors R21 and R16, the amplification factor of the first subtraction circuit can be adjusted, thereby conditioning the output voltage of the second voltage acquisition circuit to a preset range (e.g., 0~3.3V) for accurate reading by the controller.

[0054] In addition, resistor R22 is placed at the non-inverting input of op-amp U3A to provide impedance matching, and resistor R20 is placed at the output (pin 1) of op-amp U3A to provide output current limiting protection.

[0055] like Figure 7As shown, in one embodiment of this application, the fault diagnosis system for the temperature measurement branch of the energy storage battery further includes a DC bias circuit. The DC bias circuit includes a resistor R23 and a resistor R24. The first end of the resistor R23 is connected to a DC power supply, and the second end of the resistor R23 is grounded through the resistor R24. The second end of the resistor R23 serves as the bias voltage VREF.

[0056] In this embodiment, resistors R23 and R24 form a series voltage divider circuit. The voltage across resistor R24 ​​is proportional to the DC power supply VCC. The second terminal of resistor R23 (i.e., the first terminal of resistor R24) can be used as the bias voltage VREF. The magnitude of the bias voltage VREF can be adjusted by changing the resistance values ​​of resistors R23 and R24 as needed.

[0057] For example, if the DC power supply VCC is 3.3V, and the resistances of resistors R23 and R24 are equal, then the bias voltage VREF is 1.65V.

[0058] like Figure 2 As shown, in one embodiment of this application, the fault diagnosis system for the temperature measurement branch of the energy storage battery further includes a resistor R1, a first switch, a second switch, and a third switch. The first end of resistor R1 is connected to the DC power supply, and the second end of resistor R1 is connected to the first end of the temperature measuring branch through the first switch. The first terminal of the second switch is connected to the first terminal of the temperature measurement branch, and the second terminal of the second switch is connected to the third analog sampling channel of the controller; the third switch is connected in series in the second voltage acquisition circuit. The control terminals of the first switch, the second switch, and the third switch are respectively connected to the controller.

[0059] In this embodiment, the first, second, and third switches can be implemented using transistors. When measuring the temperature of the energy storage battery, the controller outputs a high-level control signal CTRL1 to the control terminal of the second switch (transistor Q2) and a high-level control signal CTRL2 to the control terminal of the first switch (transistor Q1), controlling the first and second switches to conduct. The DC power supply VCC sequentially passes through resistor R1, the first switch, the sampling resistor RS, and the thermistor RT to form a temperature measurement circuit for measuring the energy storage battery temperature. The temperature measurement signal is connected to the controller's third analog sampling channel AD3 through the second switch. At this time, the controller does not output the original excitation signal and does not perform fault diagnosis of the temperature measurement branch. Simultaneously, the controller outputs a low-level control signal CTRL3 to the control terminal of the third switch (transistor Q3), controlling the third switch to disconnect. This ensures the accuracy of temperature measurement and avoids resistors RF1 and RF2 consuming the DC power supply VCC. Furthermore, resistor R25 is the collector pull-up resistor of transistor Q2, and resistors R3, R4, and R5 are all current-limiting resistors.

[0060] When diagnosing a fault in the temperature measurement branch, the controller outputs a low-level control signal CTRL2 to the control terminal of the first switch and a low-level control signal CTRL1 to the control terminal of the second switch, controlling the first and second switches to open. At the same time, the controller outputs a high-level control signal CTRL3 to the control terminal of the third switch, controlling the third switch to close, and outputs the original excitation signal to the input terminal of the signal conditioning circuit. The signal conditioning circuit outputs a unipolar sinusoidal excitation signalal to both ends of the temperature measurement branch to perform fault diagnosis of the temperature measurement branch.

[0061] The above description is only an optional implementation method for some implementation scenarios of this application. It should be noted that for those skilled in the art, other similar implementation methods based on the technical concept of this application without departing from the technical concept of this application also fall within the protection scope of the embodiments of this application.

Claims

1. A fault diagnosis system for the temperature measurement branch of an energy storage battery, characterized in that, The temperature measurement branch includes a sampling resistor, a thermistor, and a capacitor C1. The first end of the sampling resistor is the first end of the temperature measurement branch, and the second end of the sampling resistor is connected to the first end of the thermistor. The second end of the thermistor is the second end of the temperature measurement branch. The capacitor C1 is connected in parallel across the thermistor. The fault diagnosis system includes a controller, a signal conditioning circuit, a first voltage acquisition circuit, and a second voltage acquisition circuit. The controller is configured to output the original excitation signal to the input terminal of the signal conditioning circuit at a preset time point. The signal conditioning circuit is configured to condition the original excitation signal and output a unipolar sinusoidal excitation signal. The output terminal of the signal conditioning circuit is connected to the first terminal of the temperature measuring branch, and the second terminal of the temperature measuring branch is grounded. The first voltage acquisition circuit is configured to acquire the voltage signal across the sampling resistor, and the second voltage acquisition circuit is configured to acquire the voltage signal across the temperature measurement branch. The output of the first voltage acquisition circuit is connected to the first analog sampling channel of the controller, and the output of the second voltage acquisition circuit is connected to the second analog sampling channel of the controller. The controller is also configured to: The current signal of the temperature measuring branch is calculated based on the voltage signal across the sampling resistor and the resistance value of the sampling resistor. The complex impedance of the temperature measuring branch is calculated based on the voltage signal at both ends of the temperature measuring branch and the current signal of the temperature measuring branch; the complex impedance includes a real part and an imaginary part of the impedance. The resistance of the thermistor is calculated based on the imaginary part of the impedance, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal. The contact resistance of the temperature measuring branch is calculated based on the real part of the impedance, the resistance value of the thermistor, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal. Based on the relative magnitude of the contact resistance and the preset impedance threshold, the fault diagnosis result of the temperature measurement branch is determined.

2. The fault diagnosis system for the temperature measurement branch of the energy storage battery as described in claim 1, characterized in that, When calculating the resistance of the thermistor based on the imaginary part of the impedance, the capacitance value of the capacitor C1, and the frequency of the unipolar sinusoidal excitation signal, the controller is configured as follows: The resistance of the thermistor is calculated using the following first formula: ； in, This indicates the resistance value of the thermistor. Represents the imaginary part of the impedance. This represents the frequency of the unipolar sinusoidal excitation signal. This indicates the capacitance value of capacitor C1.

3. The fault diagnosis system for the temperature measurement branch of the energy storage battery as described in claim 1, characterized in that, When calculating the contact resistance of the temperature sensing branch based on the real part of the impedance, the resistance of the thermistor, the capacitance of capacitor C1, and the frequency of the unipolar sinusoidal excitation signal, the controller is configured as follows: The contact resistance of the temperature measuring branch is calculated using the following second formula: ； in, This indicates the contact resistance of the temperature measurement branch. Represents the real part of the impedance. This indicates the resistance value of the sampling resistor. This indicates the resistance value of the thermistor. This represents the frequency of the unipolar sinusoidal excitation signal. This indicates the capacitance value of capacitor C1.

4. The fault diagnosis system for the temperature measurement branch of the energy storage battery as described in claim 1, characterized in that, When calculating the complex impedance of the temperature sensing branch based on the voltage signal across the temperature sensing branch and the current signal of the temperature sensing branch, the controller is configured to: Digital phase-sensitive demodulation is performed on the voltage signal at both ends of the temperature measuring branch and the current signal of the temperature measuring branch to obtain the voltage in-phase component and voltage quadrature component of the voltage signal at both ends of the temperature measuring branch, and the current in-phase component and current quadrature component of the current signal. The complex impedance of the temperature measuring branch is obtained by performing complex impedance calculations based on the in-phase voltage component, the quadrature voltage component, the in-phase current component, and the quadrature current component.

5. The fault diagnosis system for the temperature measurement branch of an energy storage battery as described in claim 1, characterized in that, The original excitation signal is a PWM signal, and the signal conditioning circuit includes a low-pass filter circuit and an adder circuit connected in sequence. The input terminal of the low-pass filter circuit is the input terminal of the signal conditioning circuit. The output terminal of the low-pass filter circuit is connected to the first input terminal of the adder circuit. The second input terminal of the adder circuit is connected to the bias voltage. The output terminal of the adder circuit is the output terminal of the signal conditioning circuit.

6. The fault diagnosis system for the temperature measurement branch of an energy storage battery as described in claim 1, characterized in that, The first voltage acquisition circuit includes resistors R9, R10, and R11, and operational amplifier U2C; The first end of the resistor R10 is connected to the first end of the sampling resistor, and the second end of the resistor R10 is connected to the non-inverting input of the operational amplifier U2C. The first end of the resistor R9 is connected to the second end of the sampling resistor, and the second end of the resistor R9 is connected to the inverting input terminal of the operational amplifier U2C. The output terminal of the operational amplifier U2C is fed back to the inverting input terminal of the operational amplifier U2C through the resistor R11; The output terminal of the operational amplifier U2C is the output terminal of the first voltage acquisition circuit.

7. The fault diagnosis system for the temperature measurement branch of an energy storage battery as described in claim 1, characterized in that, The second voltage acquisition circuit includes resistor RF1, resistor RF2, and a first subtraction circuit; The first end of the resistor RF1 is connected to the first end of the temperature measuring branch, and the second end of the resistor RF1 is connected to the second end of the temperature measuring branch through the resistor RF2. The two ends of the resistor RF2 are respectively connected to the two input terminals of the first subtraction circuit, and the output terminal of the first subtraction circuit is the output terminal of the second voltage acquisition circuit.

8. The fault diagnosis system for the temperature measurement branch of an energy storage battery as described in claim 5, characterized in that, It also includes a DC bias circuit, which includes resistors R23 and R24. The first end of resistor R23 is connected to a DC power supply, and the second end of resistor R23 is grounded through resistor R24. The second end of resistor R23 serves as the bias voltage.

9. The fault diagnosis system for the temperature measurement branch of an energy storage battery as described in claim 1, characterized in that, The preset impedance threshold includes a first impedance threshold and a second impedance threshold, and the first impedance threshold is less than the second impedance threshold. Specifically, when determining the fault diagnosis result of the temperature measurement branch based on the relative magnitude of the contact resistance and a preset impedance threshold, the controller is configured as follows: If the contact resistance is greater than or equal to a preset first impedance threshold and less than a preset second impedance threshold, then a first fault alarm message is output. If the contact resistance is greater than or equal to a preset second impedance threshold, a second fault alarm message is output; the severity of the second fault alarm message is greater than the severity of the first fault alarm message.

10. The fault diagnosis system for the temperature measurement branch of an energy storage battery as described in claim 1, characterized in that, It also includes resistor R1, first switch, second switch, and third switch; The first end of the resistor R1 is connected to the DC power supply, and the second end of the resistor R1 is connected to the first end of the temperature measuring branch through the first switch. The first end of the second switch is connected to the first end of the temperature measuring branch, and the second end of the second switch is connected to the third analog sampling channel of the controller; The third switch is connected in series in the second voltage acquisition circuit; The control terminals of the first switch, the second switch, and the third switch are respectively connected to the controller.

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