Circuit and method for detecting virtual connection of sampling line of fuel cell

Abstract

The invention provides a fuel cell sampling line virtual connection detection circuit and method, fuel cells are sequentially connected in series, and the fuel cell sampling line virtual connection detection circuit comprises a filter capacitor, a sampling resistor, a voltage detection optocoupler, an optocoupler gating unit, a virtual connection detection optocoupler, a divider resistor, an analog-to-digital conversion unit and an MCU. The problem that a voltage acquisition fault problem point is difficult to position is solved; according to the virtual connection detection circuit, the isolation optocoupler and the divider resistor are added, so that the detection of the sampling line connection equivalent resistor is realized, the cost is low, and the realization is easy; according to the virtual connection detection circuit and method, the characteristic that the battery voltage is 0 when no hydrogen is supplied to the fuel battery is fully utilized, and the battery is equivalent to a resistor for measurement; according to the virtual connection detection circuit and method, the complexity of fuel cell voltage acquisition fault processing is reduced, and the after-sale cost of the CVM is reduced.

Description

Technical Field

[0001] The invention belongs to the field of new energy batteries, and in particular relates to a circuit and method for detecting virtual connection of a fuel cell sampling line. Background Art

[0002] The fuel cell system needs to accurately monitor the voltage of each single cell in the stack to ensure the safe and reliable operation of the stack. This monitoring process is achieved by collecting the voltage of the battery cell through a voltage monitor (CVM). The premise for accurate voltage collection is that the connection between the battery voltage sampling line and each single cell in the stack is effective and reliable. However, there are many strings in the fuel cell stack. Even if two pieces are inspected at a time, there are more than 100 inspection lines for stacks above 50kW. In addition, the thickness of the fuel cell bipolar plate is very small, and the process of welding the sampling line to the bipolar plate is complicated. Therefore, crimping is more often used to connect the sampling line and the battery bipolar plate. The mechanical structure and friction force are used to ensure the effective electrical connection. According to the actual situation, this connection method cannot completely avoid loosening due to vehicle vibration and forming poor contact.

[0003] One of the common faults of fuel cell systems is voltage acquisition failure. The typical phenomenon is that two strings of voltage acquisition are abnormal in succession. There are three possible causes for this fault: 1) abnormal battery voltage; 2) abnormal sampling line connection; 3) abnormal CVM operation. The severity levels of the three causes are different. The first is abnormal battery voltage, which requires shutdown processing to prevent further damage to the battery; the latter two abnormalities will not cause further damage, and a shielding strategy can be adopted to keep the system running. The most common cause of the fault is abnormal sampling line connection. The worst case of abnormal connection is open circuit, but the current CVM basically has a disconnection detection mechanism, which can identify this fault; another case is virtual connection, that is, poor contact, in which case the contact impedance may be large. At present, there is a lack of effective detection measures for virtual connection of sampling lines. A judgment method is proposed in the patent of Beijing Yihuatong Technology Co., Ltd. (application number: CN2022110092288), but it is only a judgment strategy based on software data and cannot be used as an actual judgment basis.

[0004] The lack of a method to detect loose connections in the sampling lines makes it impossible to determine the cause of a voltage acquisition failure. To solve the problem, the fuel cell system needs to be disassembled for inspection, and the CVM parts after-sales service is triggered, resulting in a huge loss of manpower and material resources. Summary of the invention

[0005] In view of the technical problems of the prior art, the present invention provides a fuel cell sampling line virtual connection detection circuit and method.

[0006] According to one aspect of the present invention, the present invention provides a circuit for detecting virtual connection of a fuel cell sampling line, wherein the fuel cell is connected in series in sequence, and comprises a filter capacitor, a sampling resistor, a voltage detection optocoupler, an optocoupler gating unit, a virtual connection detection optocoupler, a voltage dividing resistor, an analog-to-digital conversion unit, and an MCU;

[0007] Both ends of the fuel cells connected in series and between two adjacent fuel cells connected in series are each connected to one end of a sampling line, one end of each of the sampling lines is each connected to the first end of a sampling resistor, the second end of each sampling resistor is connected to the signal input end of a voltage detection optocoupler, a filter capacitor is connected between the second ends of two adjacent sampling resistors, the control signal output end of the optocoupler gating unit is one-to-one connected to the control signal input end of a voltage detection optocoupler, and the control signal input end of the optocoupler gating unit is connected to the MCU;

[0008] The analog-to-digital conversion unit is used to convert an input differential analog signal into a digital signal. The two differential signal input terminals of the analog-to-digital conversion unit are respectively connected to the signal output terminals of a virtual connection detection optocoupler, the control signal input terminal of the virtual connection detection optocoupler is connected to the MCU, the signal input terminal of the virtual connection detection optocoupler is connected to one end of a voltage-dividing resistor, the other end of the voltage-dividing resistor corresponding to the positive signal input terminal of the analog-to-digital conversion unit is connected to a positive power supply, and the other end of the voltage-dividing resistor corresponding to the negative signal input terminal of the analog-to-digital conversion unit is connected to the ground; the signal output terminals of the two voltage detection optocouplers corresponding to each fuel cell are connected to the two differential signal input terminals of the analog-to-digital conversion unit, and the voltage detection optocouplers between two adjacent fuel cells are shared, and the digital signal output terminal of the analog-to-digital conversion unit is connected to the signal input terminal of the MCU.

[0009] Furthermore, in the circuit for detecting virtual connection of the fuel cell sampling line of the present invention, for a group of adjacent voltage detection optocouplers, the corresponding fuel cells are connected in series to form a battery group, and the signal output ends of the voltage detection optocoupler corresponding to the positive pole end of the battery group and the voltage detection optocouplers spaced one apart from the voltage detection optocoupler are connected to the negative signal input end of the analog-to-digital conversion unit, and the signal output ends of the voltage detection optocoupler corresponding to the negative pole end of the battery group and the voltage detection optocouplers spaced one apart from the voltage detection optocoupler are connected to the positive signal input end of the analog-to-digital conversion unit.

[0010] Furthermore, in the circuit for detecting virtual connection of a fuel cell sampling line of the present invention, the voltage detection optocouplers corresponding to all fuel cells to be detected are connected together as a group of adjacent voltage detection optocouplers to the same analog-to-digital conversion unit; or,

[0011] The voltage detection optocouplers corresponding to all the fuel cells to be detected are divided into a plurality of groups of adjacent voltage detection optocouplers, and each group of adjacent voltage detection optocouplers is connected to an analog-to-digital conversion unit.

[0012] According to another aspect of the present invention, the present invention also provides a method for detecting virtual connection of a fuel cell sampling line, which is used in the above-mentioned circuit for detecting virtual connection of a fuel cell sampling line, and comprises the following steps:

[0013] The circuit structure CVM of the virtual connection detection of the fuel cell sampling line performs voltage detection: the MCU controls the virtual connection detection optocoupler to be disconnected, and controls the voltage detection optocoupler through the optocoupler selection unit. When measuring a fuel cell channel, the voltage detection optocoupler connected to the positive and negative electrodes of the fuel cell is turned on, and the fuel cell voltage is transmitted to the analog-to-digital conversion unit, which processes the differential voltage and transmits it to the MCU. The MCU obtains the fuel cell voltage and then transmits it to the fuel cell controller;

[0014] If the detected fuel cell voltage is normal, the voltage detection is continued. If the detected voltage is abnormal, the fuel cell system is troubleshooted based on the voltage acquisition data. If the abnormal phenomenon is not manifested as two consecutive voltage strings being abnormal, other troubleshooting methods are used. If the abnormal phenomenon is not manifested as two consecutive voltage strings being abnormal, the fuel cell stack is powered off at high voltage, and a virtual connection detection frame command is sent to the CVM through the fuel cell controller.

[0015] After receiving the virtual connection detection frame command, CVM determines whether the high voltage power-on is successful. If successful, it enters the virtual connection detection mode to perform virtual connection detection: CVM collects and calculates the equivalent resistance of the sampling line corresponding to each fuel channel that shows two consecutive strings of voltage abnormalities connected to the fuel cell, and determines whether the fuel cell sampling line connection is normal based on the equivalent resistance, and transmits the detection result to the fuel cell controller.

[0016] In the method for detecting virtual connection of a fuel cell sampling line of the present invention, whether the voltage of the fuel cell is abnormal is confirmed in the following manner: when the detected fuel cell voltage exceeds a certain range of the average value of all fuel cells, it is judged to be abnormal; when it does not exceed a certain range, it is judged to be normal.

[0017] In the method for detecting virtual connection of a fuel cell sampling line of the present invention, the fuel cell stack is purged before the high voltage of the fuel cell stack is turned off.

[0018] In the method for detecting virtual connection of the fuel cell sampling line of the present invention, after receiving the virtual connection detection frame command, the CVM determines whether the high voltage power-on is successful. After success, the CVM also sends a message back to the fuel cell controller to determine whether it is in the virtual connection detection state. If so, the CVM continues to perform virtual connection detection, otherwise the fuel cell controller continues to send instructions to the CVM to enable the CVM to perform virtual connection detection.

[0019] In the method for detecting virtual connection of a fuel cell sampling line of the present invention, after the CVM performs virtual connection detection, it transmits the sampling line connection equivalent resistance data and the virtual connection diagnosis result to the fuel cell controller through a message. If the diagnosis result shows that there is a virtual connection of the sampling line, a control strategy is adopted to shield the abnormal fuel cell voltage caused by the virtual connection, assign the abnormal fuel cell voltage to the average voltage of the fuel cell, and temporarily shield the fault; if the diagnosis result shows that there is no virtual connection of the sampling line, other types of faults are checked.

[0020] In the method for detecting virtual connection of the fuel cell sampling line of the present invention, the CVM determines whether the high-voltage power-on is successful in the following manner: when the CVM calculates the voltages of each fuel cell channel collected and confirms that the average voltage is less than the first preset value, the CVM will determine that the high-voltage power-on is successful, control the virtual connection detection optocoupler to enter the on state, and switch the circuit to the virtual connection detection mode, otherwise it will be judged that the high-voltage power-on is unsuccessful.

[0021] In the method for detecting virtual connection of a fuel cell sampling line of the present invention, the specific method for judging whether the connection of the fuel cell sampling line is normal according to the equivalent resistance is as follows:

[0022] When the sampling line connection equivalent resistance of the CELLn channel exceeds the second preset value:

[0023] ① When CELLn is the first fuel cell at the negative end of the battery pack formed by the fuel cells connected in series, if the sampling line connection equivalent resistance of the CELLn+1 channel does not exceed the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 channel exceeds the second preset value, the positive sampling line Vn of CELLn is virtually connected;

[0024] ② When CELLn is the first fuel cell at the positive end of the battery pack formed by the fuel cells connected in series, if the sampling line connection equivalent resistance of the CELLn-1 channel does not exceed the second preset value, the positive sampling line Vn of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn-1 channel exceeds the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected;

[0025] ③When CELLn is the fuel cell between the fuel cells at both ends of the battery pack formed after the fuel cells are connected in series, if the sampling line connection equivalent resistance of the CELLn+1 and CELLn-1 channels does not exceed the second preset value, it is judged as other faults; if the sampling line connection equivalent resistance of the CELLn+1 channel does not exceed the second preset value and the sampling line connection of the CELLn-1 channel exceeds the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 channel exceeds the second preset value and the sampling line of the CELLn-1 channel is not connected and exceeds the second preset value, the positive sampling line Vn of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 and CELLn-1 channels exceeds the second preset value, the positive and negative sampling lines Vn and Vn-1 of Vn are both virtually connected.

[0026] In general, the above technical solutions conceived by the present invention have beneficial effects compared with the prior art: the present invention provides a hardware detection circuit for the virtual connection fault of the fuel cell sampling line, which solves the problem that the voltage acquisition fault problem point is difficult to locate; the virtual connection detection circuit realizes the detection of the equivalent resistance of the sampling line connection by adding an isolation optocoupler and a voltage divider resistor, which is low-cost and easy to implement; the virtual connection detection circuit and method make full use of the characteristic that the battery voltage is 0 when the fuel cell has no hydrogen supply, and the battery is equivalent to a resistor for measurement; the virtual connection detection circuit and method reduce the complexity of fuel cell voltage acquisition fault processing and reduce the after-sales cost of CVM. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of an embodiment of a circuit for detecting virtual connection of a fuel cell sampling line according to the present invention;

[0028] Figure 2 It is the logic diagram for voltage acquisition abnormal fault processing;

[0029] Figure 3 This is the voltage divider circuit diagram. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The probability of a typical voltage acquisition failure being caused by abnormal CVM operation is very small. Therefore, sampling line virtual connection detection can be implemented based on CVM to distinguish between battery abnormalities and sampling line connection abnormalities, which is beneficial for the fuel cell system to adopt appropriate control strategies and reduce fault handling costs.

[0032] In order to solve the problem of lack of detection method for virtual connection of fuel cell voltage sampling line, the present invention provides a detection circuit and method for virtual connection of fuel cell sampling line, which fully utilizes the characteristic that the theoretical value of the battery voltage is 0 when there is no hydrogen supply.

[0033] 1. Basic composition

[0034] refer to Figure 1 The sampling line virtual connection detection circuit includes a filter capacitor, a sampling resistor, a voltage detection optocoupler, an optocoupler selection unit, a virtual connection detection optocoupler, a voltage dividing resistor, an analog-to-digital conversion unit and an MCU.

[0035] 2. Basic functions of constituent elements:

[0036] The sampling resistor is used for voltage sampling. The sampling resistor and the filter capacitor can be used together for filtering to filter out noise in the signal; the optocoupler gating unit controls the conduction of the voltage detection optocoupler to achieve switching of different battery channels; the virtual connection detection optocoupler is used to switch the virtual connection detection mode; the voltage dividing resistor is used for voltage dividing during virtual connection detection; the analog-to-digital conversion unit has functions such as differential amplification, inversion, and analog-to-digital conversion. In this embodiment, the ±5V differential input can be converted into a suitable digital signal and provided to the MCU; the MCU processes the collected voltage data and controls the optocoupler gating unit and the virtual connection detection optocoupler at the same time.

[0037] 3. Connection of constituent elements:

[0038] Each fuel cell voltage input is connected in series with a sampling resistor, and each battery channel is connected in parallel with a filter capacitor after the sampling resistor; the voltage detection optocoupler control terminal Pin1 is connected to the power supply, Pin2 is connected to the output of the optocoupler selection unit, the voltage detection optocoupler output terminal Pin4 is connected to the sampling resistor, and Pin3 is connected to the input of the analog-to-digital conversion unit; the positive signal input of the analog-to-digital conversion unit is disconnected and connected to the signal output terminal of a virtual connection detection optocoupler, and the signal input terminal of the virtual connection detection optocoupler is connected to the isolated 5V power supply through a voltage divider resistor; the negative signal input terminal of the analog-to-digital conversion unit is connected to the output of another virtual connection detection optocoupler, and the signal input terminal of the virtual connection detection optocoupler is connected to the isolated ground through a voltage divider resistor; the virtual connection detection optocoupler control terminal Pin1 is connected to the power supply, and Pin2 is connected to the MCU; the output of the analog-to-digital conversion unit is connected to the MCU, and the MCU is connected to the optocoupler selection unit for control, and the signal output terminals of the two voltage detection optocouplers corresponding to each fuel cell are connected to the two differential signal input terminals of the analog-to-digital conversion unit, and the voltage detection optocouplers between two adjacent fuel cells are shared. The hardware circuit diagram is as follows Figure 1 shown.

[0039] For a group of adjacent voltage detection photocouplers, the corresponding fuel cells are connected in series to form a battery group, and the signal output ends of the voltage detection photocoupler corresponding to the positive end of the battery group and the voltage detection photocouplers that are separated from the voltage detection photocoupler by one are connected to the negative signal input end of the analog-to-digital conversion unit, and the signal output ends of the voltage detection photocoupler corresponding to the negative end of the battery group and the voltage detection photocouplers that are separated from the voltage detection photocoupler by one are connected to the positive signal input end of the analog-to-digital conversion unit.

[0040] For a group of adjacent voltage detection optocouplers, the corresponding fuel cells are connected in series to form a battery group, and the signal output end of the voltage detection optocoupler corresponding to the positive end of the battery group and the voltage detection optocoupler that is separated from the voltage detection optocoupler in sequence is connected to the negative signal input end of the analog-to-digital conversion unit, and the signal output end of the voltage detection optocoupler corresponding to the negative end of the battery group and the voltage detection optocoupler that is separated from the voltage detection optocoupler in sequence is connected to the positive signal input end of the analog-to-digital conversion unit. In this embodiment, all fuel cells form a battery group, with the negative electrode to the positive electrode of the battery group, and the fuel cells are named CELL1, CELL2, CELL3, ..., CELLK, K is the number of fuel cells in the battery group, and the negative electrode sampling line and positive electrode sampling line of the nth fuel cell CELLn are Vn-1 and Vn respectively.

[0041] In this embodiment, the voltage detection optocouplers corresponding to all fuel cells to be detected are connected to the same analog-to-digital conversion unit as a group of adjacent voltage detection optocouplers. In other embodiments, the voltage detection optocouplers corresponding to all fuel cells to be detected are divided into multiple groups of adjacent voltage detection optocouplers, each group of adjacent voltage detection optocouplers is connected to an analog-to-digital conversion unit, each analog-to-digital conversion unit has a corresponding optocoupler selection unit, virtual connection detection optocoupler, voltage divider resistor, etc., and the MCU can share one or each analog-to-digital conversion unit can correspond to one.

[0042] 4. Basic working logic

[0043] The circuit is divided into two modes: voltage detection and virtual connection detection. During voltage detection, the virtual connection detection optocoupler is not turned on, and during virtual connection detection, the virtual connection detection optocoupler is turned on. The virtual connection detection mode is only turned on when the fuel cell is not flowing with hydrogen.

[0044] CVM supports the voltage acquisition abnormal fault processing logic of virtual connection detection. Figure 2 shown.

[0045] When the fuel cell system is operating normally, the circuit for detecting virtual connection of the fuel cell sampling line works in the voltage detection mode, collects the voltage of the single fuel cell and transmits it to the fuel cell controller (FCU). Specifically, the MCU controls the disconnection of the virtual connection detection optocoupler, and controls the voltage detection optocoupler through the optocoupler selection unit. When measuring a certain fuel cell channel, the voltage detection optocoupler connected to the positive and negative poles of the fuel cell is turned on, and the fuel cell voltage is transmitted to the analog-to-digital conversion unit, which processes the differential voltage and transmits it to the MCU, and then to the fuel cell controller. The fuel cell controller obtains the fuel cell voltage. When measuring a certain fuel cell channel, the voltage detection optocouplers connected to the positive and negative poles of other fuel cells are disconnected. Among them, the CVM includes the circuit for detecting virtual connection of the fuel cell sampling line, that is, the circuit for detecting virtual connection of the fuel cell sampling line is a part of the CVM.

[0046] It should be noted that, since part of the voltage input to the analog-to-digital conversion unit is reversed, the analog-to-digital conversion unit needs to be inverted for this part of the input voltage.

[0047] If the detected fuel cell voltage is normal, the voltage detection will continue. When the voltage acquisition is abnormal, the fuel cell system needs to handle and troubleshoot the fuel cell system. At this time, the voltage acquisition data can be used to determine whether the fault phenomenon is a continuous 2-string voltage abnormality. If so, after the stack is purged and the stack high voltage is turned off, the fuel cell controller sends a virtual connection detection frame command to the CVM.

[0048] Note: The judgment standard of voltage abnormality is formulated according to the system control strategy. For example, when the difference between the channel single fuel cell voltage and the average voltage of all channels exceeds 100mV, it is judged as abnormal; if it does not exceed, it is judged as normal.

[0049] After receiving the virtual connection detection command, the CVM determines whether the stack has been powered off by collecting and calculating the average voltage of each fuel cell channel. After confirmation, it enters the virtual connection detection mode. The CVM determines whether the high-voltage power-off is successful in the following way: the CVM calculates the voltage of each fuel cell channel collected and confirms that the average voltage is less than the first preset value. Only then will the CVM determine that the high-voltage power-off is successful, and control the virtual connection detection optical coupler to enter the conducting state, so that the circuit switches to the virtual connection detection mode, otherwise it is judged that the high-voltage power-off is unsuccessful. In this embodiment, the first preset value is 50mV.

[0050] After receiving the virtual connection detection frame command, CVM determines whether the high voltage power-off is successful. If successful, CVM also sends a message back to the fuel cell controller to determine whether it is in the virtual connection detection state. If so, CVM continues to perform virtual connection detection. Otherwise, the fuel cell controller continues to send instructions to CVM to make CVM perform virtual connection detection.

[0051] In the virtual connection detection mode, CVM collects and calculates the equivalent resistance of each channel sampling line connected to the battery, determines whether the battery voltage sampling line connection is normal based on the equivalent resistance, and transmits the detection results to the fuel cell controller. The staff can view the sampling line connection equivalent resistance data transmitted by CVM, as well as the virtual connection diagnosis results, so as to adopt appropriate fault handling strategies.

[0052] Only after receiving the frame command of virtual connection detection, the virtual connection detection optocoupler will be turned on and switched to the virtual connection detection mode.

[0053] In order to avoid damage caused by false triggering of the virtual connection detection mode when the battery stack is energized, it is necessary to calculate the voltage of each channel collected. When it is confirmed that the average voltage is <50mV, the MCU will control the virtual connection detection optocoupler to enter the conduction state and switch the circuit to the virtual connection detection mode.

[0054] In the virtual connection detection mode, the voltage divider resistor, the sampling resistor, the sampling line connection equivalent resistance, and the battery internal resistance will form a voltage divider, and the analog-to-digital conversion unit will collect the voltage, and then calculate the equivalent resistance of each channel sampling line connected to the battery. This equivalent resistance is very small under normal conditions of sampling line connection, close to 0Ω, and is larger when the sampling line is virtual connected, even reaching the MΩ level. Considering that the virtual connection will cause voltage collection abnormalities only when it reaches a certain degree, the sampling line connection equivalent resistance exceeds the second preset value as a basis for judging whether it is virtual connected. The second preset value is 50Ω in this embodiment.

[0055] When the sampling line connection equivalent resistance of CELLn exceeds 50Ω, because the detection result includes the connection equivalent resistance of the positive sampling line Vn of CELLn and the negative sampling line Vn-1, in order to determine which sampling line is virtual connected, the detection results of CELLn-1 and CELLn+1 are combined for judgment. For example, when the sampling line connection equivalent resistance of CELLn>50Ω, if the sampling line connection equivalent resistance of CELLn-1 is <50Ω, it can be judged that the negative sampling line Vn-1 is not virtual connected; if the sampling line connection equivalent resistance of CELLn+1 is >50Ω, it can be judged that the positive sampling line Vn is virtual connected.

[0056] After the staff confirms that the CVM is in the virtual connection detection state through the message data, they can check the sampling line connection equivalent resistance data transmitted by the CVM, as well as the virtual connection diagnosis results. If the diagnosis results show that there is a virtual connection of the sampling line, appropriate control strategies can be adopted, such as shielding the abnormal single fuel cell voltage caused by the virtual connection, assigning the abnormal single cell voltage to the average voltage of the fuel cell, and quickly troubleshooting the fault; if the diagnosis results show that there is no virtual connection of the sampling line, then take the troubleshooting methods such as disassembling the shell for inspection and contacting the parts supplier.

[0057] 5. Working principle of hardware circuit

[0058] Voltage detection: The MCU controls the voltage detection optocoupler array through the optocoupler gating unit to measure the fuel cell channels one by one. When measuring a fuel cell channel, the optocoupler connected to the positive and negative electrodes of the piece is turned on, and the battery voltage is transmitted to the analog-to-digital conversion unit input, which processes the differential voltage and transmits it to the MCU.

[0059] Virtual connection detection: MCU controls the virtual connection detection optocoupler to turn on. Since the fuel cell has no voltage at this time, it can be regarded as a resistor. At the same time, the voltage sampling line and the battery connection are also equivalent to a resistor. In this way, when the virtual connection detection optocoupler is turned on, a Figure 3 The voltage divider circuit shown, and then the optocoupler array repeats the switching steps of the above voltage detection, the analog-to-digital conversion unit can collect the voltage of the sampling resistor Rm-sampling line connected to the equivalent resistor Rc-battery internal resistance Ri-sampling line connected to the equivalent resistor Rc-sampling resistor Rm, and the MCU performs calculations to convert the voltage into resistance.

[0060] Note: The virtual connection detection optocoupler needs to use a MOS output type with small on-resistance to avoid the impact of the on-voltage drop on the output side on the detection.

[0061] Since the battery internal resistance Ri is usually at the mΩ level, and the voltage divider resistor Rd and the sampling resistor Rm have fixed values, the size of the equivalent resistance of the two sampling lines of this channel can be further calculated to diagnose whether there is a virtual connection.

[0062] The specific method of judging whether the fuel cell sampling line connection is normal based on the equivalent resistance is as follows:

[0063] When the sampling line connection equivalent resistance of the CELLn channel exceeds the second preset value:

[0064] ① When CELLn is the first fuel cell at the negative end of the battery pack formed by the fuel cells connected in series, if the sampling line connection equivalent resistance of the CELLn+1 channel does not exceed the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 channel exceeds the second preset value, the positive sampling line Vn of CELLn is virtually connected;

[0065] ② When CELLn is the first fuel cell at the positive end of the battery pack formed by the fuel cells connected in series, if the sampling line connection equivalent resistance of the CELLn-1 channel does not exceed the second preset value, the positive sampling line Vn of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn-1 channel exceeds the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected;

[0066] ③When CELLn is the fuel cell between the fuel cells at both ends of the battery pack formed after the fuel cells are connected in series, if the sampling line connection equivalent resistance of the CELLn+1 and CELLn-1 channels does not exceed the second preset value, it is judged as other faults; if the sampling line connection equivalent resistance of the CELLn+1 channel does not exceed the second preset value and the sampling line connection of the CELLn-1 channel exceeds the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 channel exceeds the second preset value and the sampling line of the CELLn-1 channel is not connected and exceeds the second preset value, the positive sampling line Vn of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 and CELLn-1 channels exceeds the second preset value, the positive and negative sampling lines Vn and Vn-1 of Vn are both virtually connected.

[0067] The key technical points of the solution of the present invention are as follows.

[0068] The fuel cell virtual connection detection circuit adds voltage-dividing resistors connected to the power supply and the ground at the input end of the analog-to-digital conversion unit to divide the voltage, and detects the resistance by detecting the voltage division of the resistors;

[0069] The virtual connection detection circuit of the fuel cell realizes the switching of the virtual connection detection mode by controlling the on and off of the virtual connection detection optocoupler. The problem of MCU and battery not sharing the same ground is avoided through optocoupler isolation, and isolation control is realized.

[0070] This fuel cell virtual connection detection circuit uses a virtual connection detection optocoupler with a high withstand voltage value on the output side to prevent high common mode voltage from affecting device functions;

[0071] The virtual connection detection circuit of the fuel cell adopts a virtual connection detection optocoupler with very small resistance when the output side is turned on, so as to avoid the voltage drop on the output side of the optocoupler affecting the virtual connection detection result;

[0072] This virtual connection detection method is mainly aimed at the typical phenomenon of abnormal voltage collection of two consecutive strings;

[0073] The virtual connection detection device of the present invention only starts the virtual connection detection mode when the fuel cell is powered off at high voltage without hydrogen supply, that is, when the fuel cell voltage is less than the first preset value;

[0074] After receiving the virtual connection detection frame command, the virtual connection detection device needs to detect whether the fuel cell voltage is less than a first preset value, and then start the virtual connection detection mode to prevent the high voltage of the fuel cell from damaging the CVM.

[0075] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0076] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0077] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0078] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0079] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A circuit for detecting virtual connection of a fuel cell sampling line, wherein the fuel cells are connected in series in sequence, characterized in that: Including filter capacitor, sampling resistor, voltage detection optocoupler, optocoupler gating unit, virtual connection detection optocoupler, voltage dividing resistor, analog-to-digital conversion unit and MCU; Both ends of the fuel cells connected in series and between two adjacent fuel cells connected in series are each connected to one end of a sampling line, one end of each of the sampling lines is each connected to the first end of a sampling resistor, the second end of each sampling resistor is connected to the signal input end of a voltage detection optocoupler, a filter capacitor is connected between the second ends of two adjacent sampling resistors, the control signal output end of the optocoupler gating unit is one-to-one connected to the control signal input end of a voltage detection optocoupler, and the control signal input end of the optocoupler gating unit is connected to the MCU; The analog-to-digital conversion unit is used to convert an input differential analog signal into a digital signal. The two differential signal input terminals of the analog-to-digital conversion unit are respectively connected to the signal output terminals of a virtual connection detection optocoupler, the control signal input terminal of the virtual connection detection optocoupler is connected to the MCU, the signal input terminal of the virtual connection detection optocoupler is connected to one end of a voltage-dividing resistor, the other end of the voltage-dividing resistor corresponding to the positive signal input terminal of the analog-to-digital conversion unit is connected to a positive power supply, and the other end of the voltage-dividing resistor corresponding to the negative signal input terminal of the analog-to-digital conversion unit is connected to the ground; the signal output terminals of the two voltage detection optocouplers corresponding to each fuel cell are connected to the two differential signal input terminals of the analog-to-digital conversion unit, and the voltage detection optocouplers between two adjacent fuel cells are shared, and the digital signal output terminal of the analog-to-digital conversion unit is connected to the signal input terminal of the MCU.

2. A fuel cell sampling line virtual connection detection circuit according to claim 1, characterized in that: For a group of adjacent voltage detection photocouplers, the corresponding fuel cells are connected in series to form a battery group, and the signal output ends of the voltage detection photocoupler corresponding to the positive end of the battery group and the voltage detection photocouplers that are separated from the voltage detection photocoupler by one are connected to the negative signal input end of the analog-to-digital conversion unit, and the signal output ends of the voltage detection photocoupler corresponding to the negative end of the battery group and the voltage detection photocouplers that are separated from the voltage detection photocoupler by one are connected to the positive signal input end of the analog-to-digital conversion unit.

3. A fuel cell sampling line virtual connection detection circuit according to claim 2, characterized in that: The voltage detection photocouplers corresponding to all the fuel cells to be detected are connected together as a group of adjacent voltage detection photocouplers to the same analog-to-digital conversion unit; or, The voltage detection optocouplers corresponding to all the fuel cells to be detected are divided into a plurality of groups of adjacent voltage detection optocouplers, and each group of adjacent voltage detection optocouplers is connected to an analog-to-digital conversion unit.

4. A method for detecting virtual connection of a fuel cell sampling line, used in a circuit for detecting virtual connection of a fuel cell sampling line as claimed in any one of claims 1 to 3, characterized in that: The steps include: The circuit for detecting virtual connection of the fuel cell sampling line performs voltage detection: the MCU controls the virtual connection detection optocoupler to be disconnected, and controls the voltage detection optocoupler through the optocoupler gating unit. When measuring a fuel cell channel, the voltage detection optocoupler connected to the positive and negative electrodes of the fuel cell is turned on, and the fuel cell voltage is transmitted to the analog-to-digital conversion unit, which processes the differential voltage and transmits it to the MCU, and then transmits it to the fuel cell controller; If the detected fuel cell voltage is normal, the voltage detection is continued. If the detected voltage is abnormal, the fuel cell system is troubleshooted based on the voltage acquisition data. If the abnormal phenomenon is not manifested as two consecutive voltage strings being abnormal, other troubleshooting methods are used. If the abnormal phenomenon is not manifested as two consecutive voltage strings being abnormal, the fuel cell stack is powered off at high voltage, and a virtual connection detection frame command is sent to the CVM through the fuel cell controller. After receiving the virtual connection detection frame command, CVM determines whether the high voltage power-on is successful. If successful, it enters the virtual connection detection mode to perform virtual connection detection: CVM collects and calculates the equivalent resistance of the sampling line corresponding to each fuel channel that shows two consecutive strings of voltage abnormalities connected to the fuel cell, and determines whether the fuel cell sampling line connection is normal based on the equivalent resistance, and transmits the detection result to the fuel cell controller.

5. The method for detecting virtual connection of a fuel cell sampling line according to claim 4, characterized in that: Whether the detected fuel cell voltage is abnormal is confirmed in the following manner: when the detected fuel cell voltage exceeds a certain range of the average value of all fuel cells, it is judged to be abnormal; when it does not exceed a certain range, it is judged to be normal.

6. The method for detecting virtual connection of a fuel cell sampling line according to claim 4, characterized in that: The fuel cell stack is purged before the high voltage is turned off.

7. The method for detecting virtual connection of a fuel cell sampling line according to claim 4, characterized in that: After receiving the virtual connection detection frame command, CVM determines whether the high voltage power-off is successful. If successful, CVM also sends a message back to the fuel cell controller to determine whether it is in the virtual connection detection state. If so, CVM continues to perform virtual connection detection. Otherwise, the fuel cell controller continues to send instructions to CVM to make CVM perform virtual connection detection.

8. The method for detecting virtual connection of a fuel cell sampling line according to claim 4, characterized in that: After CVM performs a virtual connection detection, it transmits the sampling line connection equivalent resistance data and the virtual connection diagnosis result to the fuel cell controller through a message. If the diagnosis result shows that there is a virtual connection in the sampling line, a control strategy is adopted to shield the abnormal fuel cell voltage caused by the virtual connection, assign the abnormal fuel cell voltage to the average voltage of the fuel cell, and temporarily shield the fault; if the diagnosis result shows that there is no virtual connection in the sampling line, other types of faults are checked.

9. The method for detecting virtual connection of a fuel cell sampling line according to claim 4, characterized in that: CVM determines whether the high-voltage power-off is successful in the following manner: CVM calculates the collected voltages of each fuel cell channel and confirms that the average voltage is less than the first preset value. Only then will CVM determine that the high-voltage power-off is successful and control the virtual connection detection optocoupler to enter the on state, so that the circuit switches to the virtual connection detection mode. Otherwise, it will be determined that the high-voltage power-off is unsuccessful.

10. The method for detecting virtual connection of a fuel cell sampling line according to claim 4, characterized in that: The specific method of judging whether the fuel cell sampling line connection is normal based on the equivalent resistance is as follows: When the sampling line connection equivalent resistance of the CELLn channel exceeds the second preset value: ① When CELLn is the first fuel cell at the negative end of the battery pack formed by the fuel cells connected in series, if the sampling line connection equivalent resistance of the CELLn+1 channel does not exceed the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 channel exceeds the second preset value, the positive sampling line Vn of CELLn is virtually connected; ② When CELLn is the first fuel cell at the positive end of the battery pack formed by the fuel cells connected in series, if the sampling line connection equivalent resistance of the CELLn-1 channel does not exceed the second preset value, the positive sampling line Vn of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn-1 channel exceeds the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; ③When CELLn is the fuel cell between the fuel cells at both ends of the battery pack formed after the fuel cells are connected in series, if the sampling line connection equivalent resistance of the CELLn+1 and CELLn-1 channels does not exceed the second preset value, it is judged as other faults; if the sampling line connection equivalent resistance of the CELLn+1 channel does not exceed the second preset value and the sampling line connection of the CELLn-1 channel exceeds the second preset value, the negative sampling line Vn-1 of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 channel exceeds the second preset value and the sampling line of the CELLn-1 channel is not connected and exceeds the second preset value, the positive sampling line Vn of CELLn is virtually connected; if the sampling line connection equivalent resistance of the CELLn+1 and CELLn-1 channels exceeds the second preset value, the positive and negative sampling lines Vn and Vn-1 of Vn are both virtually connected.

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