Energy recovery method and device for load reduction working condition of fuel cell stack, vehicle and medium

Abstract

The invention relates to an energy recovery method and device for a fuel cell stack under a load reduction working condition, a vehicle and a medium. The method comprises the steps of judging whether a fuel cell stack is in a load reduction working condition; under the condition that the fuel cell stack is in the load reduction working condition, judging whether a load reduction response delay phenomenon exists or not; and under the condition that the load reduction response delay phenomenon exists, based on the capacitance characteristic of the fuel cell stack, the voltage recovery gradient, the total output current, the cell temperature and the air flow of the fuel cell stack under the load reduction working condition are adjusted, so that energy recovery of the fuel cell stack under the load reduction working condition is carried out. Therefore, the energy output of the electric pile is controlled by controlling the temperature, the flow, the voltage and the current in the electric pile load reduction working condition on line, so that the problems that in the prior art, the implementation cost is high, and the energy recovery requirements under different road conditions and driving requirements cannot be better met due to the fact that the implementation strategy is not flexible enough are solved; an energy management strategy of low cost and high energy recovery is realized, and resource waste and electric pile loss are reduced.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to an energy recovery method, device, vehicle and medium for a fuel cell stack under load reduction conditions. Background Art

[0002] During the load reduction process of fuel cell commercial vehicles, there is a delay in the response of the fuel cell stack working conditions, resulting in the power generated by the fuel cell stack exceeding the power required by the motor or lithium battery. If this excess energy is not effectively utilized, it will accelerate the loss of the fuel cell stack and also lead to excessive consumption of hydrogen fuel, resulting in a waste of resources.

[0003] In the related art, generally, the method of increasing the capacity of lithium batteries is used to recover the excess energy generated by the load reduction delay of the battery stack; or a fixed operating condition operation strategy of the battery stack is adopted to allow the recovery node to change the load through the lithium battery.

[0004] However, this method has certain limitations. Increasing the capacity of lithium batteries will increase the weight and cost of the vehicle, and the number of charge and discharge times of lithium batteries is limited. Long-term and frequent use will shorten their service life. The use of a fixed operating condition strategy for the battery stack limits the flexibility and adaptability of the vehicle, and cannot meet the energy recovery requirements under different road conditions and driving needs, which needs to be urgently resolved. Summary of the invention

[0005] The present application provides an energy recovery method, device, vehicle and medium for a fuel cell stack under load reduction conditions, so as to solve the problems of high implementation cost of the prior art and insufficient flexibility of the implementation strategy, which leads to the inability to better meet the energy recovery requirements under different road conditions and driving needs, and to realize a low-cost, high-energy recovery energy management strategy, thereby reducing resource waste and stack loss.

[0006] To achieve the above-mentioned purpose, the first embodiment of the present application proposes an energy recovery method for a fuel cell stack under load reduction conditions, comprising the following steps:

[0007] Determine whether the fuel cell stack is in a load reduction condition;

[0008] When the fuel cell stack is in the load reduction condition, determining whether there is a load reduction response delay phenomenon;

[0009] In the presence of the load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, the voltage recovery gradient, total output current, cell temperature and air flow of the fuel cell stack under the load reduction condition are adjusted to perform energy recovery under the load reduction condition of the fuel cell stack.

[0010] According to an embodiment of the present application, adjusting the voltage recovery gradient, total output current, cell temperature, and air flow of the fuel cell stack under the load reduction condition includes:

[0011] Using cyclic voltammetry, adjusting the voltage recovery gradient of the fuel cell stack under the load reduction condition based on a preset voltage scan slope;

[0012] Obtaining the capacitive charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition, and controlling the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitive charging current;

[0013] Using a thermal management system to control the cell temperature of the fuel cell stack under the load reduction condition within a preset temperature range;

[0014] Based on the vehicle demand current, controlling the rotational speed of the air compressor and the opening degree of the bypass valve to adjust the air flow entering the fuel cell stack under the load reduction condition.

[0015] According to an embodiment of the present application, using cyclic voltammetry to control the voltage recovery gradient of the fuel cell stack under the load reduction condition based on a preset voltage scan slope includes:

[0016] Using cyclic voltammetry to obtain the dynamic capacitance value of the fuel cell stack under the load reduction condition;

[0017] Determining the preset voltage scan slope based on the dynamic capacitance value, and adjusting the voltage recovery gradient of the fuel cell stack under the load reduction condition according to the preset voltage scan slope.

[0018] According to an embodiment of the present application, adjusting the voltage recovery gradient of the fuel cell stack under the load reduction condition according to the preset voltage scan slope includes:

[0019] Obtaining the initial output voltage of the fuel cell stack under the load reduction condition;

[0020] Obtaining the vehicle demand power, and calculating the target voltage of the fuel cell stack after load reduction according to the vehicle demand power;

[0021] Based on the preset voltage scan slope, controlling the voltage of the fuel cell stack under the load reduction condition to linearly rise from the initial output voltage to the target voltage.

[0022] According to an embodiment of the present application, obtaining the capacitive charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition, and controlling the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitive charging current includes:

[0023] Calculating the capacitive charging current according to the dynamic capacitance value and the preset voltage scanning slope;

[0024] Based on the vehicle demand current and the capacitive charging current, calculating the total output current of the fuel cell stack under the load reduction condition.

[0025] According to an embodiment of the present application, using the thermal management system to control the cell temperature of the fuel cell stack within a preset temperature range under the load reduction condition includes:

[0026] Obtaining the cell temperature of the fuel cell stack in real time;

[0027] Determining the target flow rate of the coolant according to the cell temperature, and adjusting the rotation speed of the water pump of the thermal management system based on the target flow rate of the coolant;

[0028] And / or, determining the target rotation speed of the cooling fan according to the cell temperature, and adjusting the rotation speed of the cooling fan of the thermal management system based on the target rotation speed of the cooling fan;

[0029] And / or, determining the target flow direction of the coolant according to the cell temperature, and adjusting the opening and closing state of the electronic thermostat of the thermal management system based on the target flow direction of the coolant.

[0030] According to an embodiment of the present application, based on the vehicle demand current, controlling the rotation speed of the air compressor and the opening of the bypass valve, and adjusting the air flow rate entering the fuel cell stack in the load reduction condition includes:

[0031] Based on the vehicle demand current, determining the target cathode air flow rate entering the fuel cell stack in the load reduction condition;

[0032] Controlling the rotation speed of the air compressor and the opening of the bypass valve so that the air flow rate entering the fuel cell stack in the load reduction condition meets the target cathode air flow rate.

[0033] According to the energy recovery method for the fuel cell stack under the load reduction condition proposed by the embodiments of the present application, when the fuel cell stack is in the load reduction condition and there is a load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, the voltage recovery gradient, the total output current, the cell temperature, and the air flow rate of the fuel cell stack under the load reduction condition are adjusted to recover the energy of the fuel cell stack under the load reduction condition. Thus, the problems in the prior art that the implementation cost is relatively high and the implementation strategy is not flexible enough to better meet the energy recovery requirements under different road conditions and driving demands are solved, and an energy management strategy with low cost and high energy recovery is realized, reducing resource waste and stack loss.

[0034] To achieve the above object, an energy recovery device for the fuel cell stack under the load reduction condition proposed by the second aspect of the present application includes:

[0035] The first judgment module is used to judge whether the fuel cell stack is in the load reduction condition;

[0036] The second judgment module is used to judge whether there is a load reduction response delay phenomenon when the fuel cell stack is in the load reduction condition;

[0037] The adjustment module is used to, when there is the load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, adjust the voltage recovery gradient, the total output current, the cell temperature, and the air flow rate of the fuel cell stack under the load reduction condition to recover the energy of the fuel cell stack under the load reduction condition.

[0038] According to an embodiment of the present application, the adjustment module includes:

[0039] The first adjustment unit is used to, by using cyclic voltammetry, adjust the voltage recovery gradient of the fuel cell stack under the load reduction condition based on a preset voltage scanning slope;

[0040] The first control unit is used to obtain the capacitance charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition, and control the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitance charging current;

[0041] The second control unit is used to control the cell temperature of the fuel cell stack under the load reduction condition to be within a preset temperature range by using a thermal management system;

[0042] The second adjustment unit is used to control the rotation speed of the air compressor and the opening degree of the bypass valve based on the vehicle demand current to adjust the air flow rate entering the fuel cell stack in the load reduction condition.

[0043] According to an embodiment of the present application, the first adjustment unit includes:

[0044] An acquisition subunit, configured to acquire the dynamic capacitance value of the fuel cell stack under the load reduction condition by using the cyclic voltammetry method;

[0045] An adjustment subunit, configured to determine the preset voltage sweep slope based on the dynamic capacitance value, and adjust the voltage recovery gradient of the fuel cell stack under the load reduction condition according to the preset voltage sweep slope.

[0046] According to an embodiment of the present application, the adjustment subunit is specifically configured to:

[0047] Acquire the initial output voltage of the fuel cell stack under the load reduction condition;

[0048] Acquire the vehicle demand power, and calculate the target voltage of the fuel cell stack after load reduction according to the vehicle demand power;

[0049] Based on the preset voltage sweep slope, control the voltage of the fuel cell stack under the load reduction condition to linearly rise from the initial output voltage to the target voltage.

[0050] According to an embodiment of the present application, the first control unit is specifically configured to:

[0051] Calculate the capacitive charging current according to the dynamic capacitance value and the preset voltage sweep slope;

[0052] Based on the vehicle demand current and the capacitive charging current, calculate the total output current of the fuel cell stack under the load reduction condition.

[0053] According to an embodiment of the present application, the second control unit is specifically configured to:

[0054] Real-time acquire the cell temperature of the fuel cell stack;

[0055] Determine the target flow rate of the coolant according to the cell temperature, and adjust the rotational speed of the water pump of the thermal management system based on the target flow rate of the coolant;

[0056] And / or, determine the target rotational speed of the cooling fan according to the cell temperature, and adjust the rotational speed of the cooling fan of the thermal management system based on the target rotational speed of the cooling fan;

[0057] And / or, determine the target flow direction of the coolant according to the cell temperature, and adjust the opening and closing state of the electronic thermostat of the thermal management system based on the target flow direction of the coolant.

[0058] According to an embodiment of the present application, the second adjustment unit is specifically configured to:

[0059] Determine a target cathode air flow rate entering the fuel cell stack in the load reduction condition based on the vehicle demand current;

[0060] Control the rotational speed of the air compressor and the opening degree of the bypass valve so that the air flow rate entering the fuel cell stack in the load reduction condition meets the target cathode air flow rate.

[0061] According to the energy recovery device for the fuel cell stack under the load reduction condition proposed in the embodiment of the present application, when the fuel cell stack is in the load reduction condition and there is a load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, the voltage recovery gradient, the total output current, the cell temperature and the air flow rate of the fuel cell stack in the load reduction condition are adjusted to recover the energy of the fuel cell stack under the load reduction condition. Thus, the problems in the prior art that the implementation cost is relatively high and the implementation strategy is not flexible enough to better meet the energy recovery requirements under different road conditions and driving demands are solved, and an energy management strategy with low cost and high energy recovery is realized, reducing resource waste and stack loss.

[0062] To achieve the above object, an embodiment of the third aspect of the present application proposes a vehicle, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to implement the energy recovery method for the fuel cell stack under the load reduction condition as described in the above embodiment.

[0063] To achieve the above object, an embodiment of the fourth aspect of the present application proposes a computer-readable storage medium, on which a computer program is stored, and the program is executed by a processor to be used to implement the energy recovery method for the fuel cell stack under the load reduction condition as described in the above embodiment.

[0064] The additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Description of the Drawings

[0065] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of the embodiments in conjunction with the drawings, where:

[0066] Figure 1 is a flowchart of an energy recovery method for a fuel cell stack under a load reduction condition provided according to an embodiment of the present application;

[0067] Figure 2 is a schematic diagram of the double-layer capacitance formed on the surfaces of the anode and cathode electrodes during the electrochemical reaction process of the fuel cell stack according to an embodiment of the present application;

[0068] Figure 3 is a schematic diagram of the voltage-current circuit principle in the load reduction condition according to an embodiment of the present application;

[0069] Figure 4 Schematic diagram of a voltage-current PID (Proportional-Integral-Differential) control strategy architecture according to an embodiment of the present application;

[0070] Figure 5 Schematic diagram of cyclic voltammetry according to an embodiment of the present application;

[0071] Figure 6 Schematic diagram of a cyclic voltammogram according to an embodiment of the present application;

[0072] Figure 7 Schematic diagram of a method for calculating the initial state value of the double-layer capacitance of a fuel cell stack according to an embodiment of the present application;

[0073] Figure 8 Block diagram of an energy recovery device for a fuel cell stack under a load reduction condition according to an embodiment of the present application;

[0074] Figure 9 Schematic diagram of the structure of a vehicle according to an embodiment of the present application. Detailed implementation manners

[0075] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and should not be construed as limiting the present application.

[0076] The energy recovery method, device, vehicle and medium for a fuel cell stack under a load reduction condition according to an embodiment of the present application will be described below with reference to the drawings. First, the energy recovery of a fuel cell stack under a load reduction condition according to an embodiment of the present application will be described with reference to the drawings.

[0077] Figure 1 Flow chart of an energy recovery method for a fuel cell stack under a load reduction condition according to an embodiment of the present application.

[0078] As Figure 1 shown, the energy recovery method for the fuel cell stack under a load reduction condition includes the following steps:

[0079] In step S101, it is determined whether the fuel cell stack is in a load reduction condition.

[0080] It can be understood that a fuel cell stack is a device that can directly convert chemical energy into electrical energy. Usually, hydrogen and oxygen are used as reactants to generate electrical energy and water in the stack. The load reduction condition refers to the state where the load of the fuel cell stack decreases during operation. For example, the situation where a fuel cell vehicle reduces its load.

[0081] In step S102, when the fuel cell stack is in the load reduction condition, it is judged whether there is a load reduction response delay phenomenon.

[0082] That is to say, when the fuel cell stack is in the load reduction condition, its output power or voltage adjustment reaction may not be fast enough, there is a delay, and the power generated by the stack exceeds the power required by the motor or lithium battery (i.e., the load reduction response delay phenomenon). In order not to cause waste of resources, it can be checked whether there is a load reduction response delay phenomenon when the fuel cell stack is in the load reduction condition.

[0083] In step S103, when there is a load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, the voltage recovery gradient, total output current, cell temperature, and air flow rate of the fuel cell stack in the load reduction condition are adjusted to recover the energy of the fuel cell stack in the load reduction condition.

[0084] It can be understood that as Figure 2 shown, a double-layer capacitance will be formed on the surfaces of the anode and cathode electrodes during the electrochemical reaction process of the stack. Utilizing the charge and discharge characteristics of the capacitance of the fuel cell stack, during the process of the stack voltage rising (i.e., under the load reduction condition), the double-layer capacitance is in the charging state and can absorb the excess energy generated by the load reduction delay of the stack, thereby realizing energy recovery. Its circuit principle is as Figure 3 shown. The voltage recovery gradient refers to the speed at which the voltage of the fuel cell stack returns to the normal level after load reduction. The total output current includes the current output to meet the vehicle's requirements and the charging current of the double-layer capacitance used for energy recovery inside. The cell temperature refers to the operating temperature of a single fuel cell unit (i.e., the cell) inside the fuel cell stack. The air flow rate refers to the gas flow rate flowing through the cathode of the fuel cell stack.

[0085] When facing the load reduction response delay phenomenon, the embodiment of the present application can be optimized by utilizing the capacitance characteristics of the fuel cell stack. Specifically, the key parameters such as the voltage recovery gradient, total output current, cell temperature, and air flow rate of the fuel cell stack in the load reduction condition can be precisely adjusted, thereby effectively recovering energy. This adjustment strategy not only helps to improve the performance of the fuel cell stack under the load reduction condition, but also optimizes the energy efficiency of the entire system, ensuring that the energy can be maximally recovered and utilized during the load reduction process and reducing energy waste.

[0086] For ease of understanding, the following details how to adjust the voltage recovery gradient, total output current, cell temperature, and air flow of a fuel cell stack under a load reduction condition to achieve energy recovery under the load reduction condition of the fuel cell stack.

[0087] Before performing energy management on a real vehicle using the energy management strategy proposed in the embodiments of the present application, first, an accelerated stack life test can be carried out through a hub test bench, that is, different initial stack powers for load reduction are calibrated on the chassis dynamometer to obtain the commercial vehicle lithium battery power capacity (kWh) and SOC (State of Charge) state (%) under different load reduction conditions, so as to obtain the mapping relationship between the allowable charging power and charging time of the lithium battery and the load reduction delay power of the stack. At the same time, the mapping relationship between the vehicle operating conditions and the motor demand power is obtained, and when implementing the energy management strategy, by collecting the power consumption of the BOP (Balance Of Plant, the auxiliary equipment system corresponding to core equipment such as fuel cell stacks, electrolytic water hydrogen production, and hydrogen circulation) in real time (including power consumption during the load reduction operation of the air compressor, power consumption of the cooling fan operation, power consumption of the water pump operation, etc.), the mapping relationship between the BOP power consumption and the load reduction delay power of the stack can be obtained.

[0088] Furthermore, according to the test, the load reduction delay time (a set of data) of the fuel cell stack under different conditions is obtained, including reducing the load to the vehicle demand power or idle power, so as to obtain the mapping relationship between the load reduction delay time and the load reduction condition, which helps to understand the response characteristics of the fuel cell stack under different conditions.

[0089] Furthermore, according to the test, the mapping relationship between the stack charging capacitance (i.e., the dynamic capacitance value, and the initial dynamic capacitance value needs to be calibrated) and the capacitance charging current of the fuel cell stack under the load reduction condition is obtained, and the mapping relationship between the voltage sweep slope and the capacitance charging current under different load reduction conditions is calculated by the cyclic voltammetry (C-V method). The voltage sweep slope is set to ensure that the voltage and current of the stack can be accurately controlled in the subsequent control strategy.

[0090] Furthermore, according to the test, the mapping relationship between the voltage sweep slope and the cathode pressure, flow rate, cell temperature, humidity, and stoichiometry of the fuel cell stack under the load reduction condition is obtained, and the air path control strategy of the fuel cell stack under different temperature conditions is formulated.

[0091] Furthermore, according to the test, the mapping relationship between the vehicle demand current and the (double-layer) capacitance charging current of the fuel cell stack under the load reduction condition is obtained. The external output current (or power) of the stack is controlled by a DCDC (Direct Current Direct Current) module. This part of the current is the vehicle demand current, which meets the vehicle demand. At the same time, the capacitance charging current is used to realize the internal heat release (energy recovery) of the stack.

[0092] Furthermore, due to different ambient temperatures, the heat dissipation capacity of the stack thermal management system changes. Different ambient temperatures are calibrated according to the test to obtain the mapping relationship between the stack temperature, humidity control and the thermal management system (such as the rotational speed of the cooling fan, the rotational speed of the water pump, the opening degree of the electronic thermostat, etc.) at different ambient temperatures, so as to obtain the power consumption requirements of the auxiliary components and the thermal management control strategy.

[0093] Based on the data and mapping relationships obtained above, the embodiments of the present application can utilize the online energy management control algorithm of the fuel cell stack of the FCCU (Fuel Cell Control Unit) and the PID control logic (as Figure 4 shown), through real-time calculation, to adjust the voltage recovery gradient, total output current, cell temperature and air flow of the fuel cell stack under the load reduction condition, so as to ensure the efficient operation and energy management of the fuel cell stack under different working conditions.

[0094] As a possible implementation manner, in some embodiments, adjusting the voltage recovery gradient, total output current, cell temperature and air flow of the fuel cell stack under the load reduction condition includes: using cyclic voltammetry to adjust the voltage recovery gradient of the fuel cell stack under the load reduction condition based on a preset voltage sweep slope; obtaining the capacitance charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition, and controlling the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitance charging current; using the thermal management system to control the cell temperature of the fuel cell stack under the load reduction condition within a preset temperature range; based on the vehicle demand current, controlling the rotational speed of the air compressor and the opening degree of the bypass valve to adjust the air flow entering the fuel cell stack under the load reduction condition.

[0095] It is understandable that cyclic voltammetry is an electrochemistry test method. By applying a linearly varying voltage (scanning voltage) to the electrode, periodically changing the potential of the electrode, and recording the curve of current varying with potential, the redox reaction of substances on the electrode surface can be studied. In a fuel cell stack, this method can be used to control the rising gradient of the stack voltage, thereby regulating the charging process of the double-layer capacitance. The voltage scanning slope represents the change amount of voltage per unit time (i.e., the rising gradient of voltage), which is a key parameter for controlling the voltage rise. By adjusting the value of the voltage scanning slope, the rising speed of the stack voltage can be precisely controlled. Here, the preset value of the voltage scanning slope is not specifically limited.

[0096] Specifically, during the load reduction process of the stack, the embodiments of the present application can use cyclic voltammetry to calibrate the voltage scanning slope, and based on the calibrated value of the voltage scanning slope (i.e., the preset voltage scanning slope), control the rising gradient of the reverse scanning voltage. Through the FCCU, the vehicle demand current (power) can be collected in real time. Based on the preset voltage scanning slope, the capacitive charging current of the fuel cell stack can be determined. Based on these two currents, the total output current of the fuel cell stack under the load reduction condition can be controlled. The temperature of the stack cell is controlled within a safe range (i.e., the preset temperature range) through the thermal management system (including, for example, water pumps, electronic thermostat, cooling fans, etc.) to prevent the stack temperature from being too high. Based on the change of the vehicle demand current, parameters such as the rotational speed of the air compressor and the opening degree of the bypass valve can be dynamically adjusted through the FCCU, thereby realizing the control of the air flow rate entering the fuel cell stack inlet.

[0097] Optionally, in some embodiments, using cyclic voltammetry to control the rising gradient of the fuel cell stack voltage under the load reduction condition based on a preset voltage scanning slope includes: using cyclic voltammetry to obtain the dynamic capacitance value of the fuel cell stack under the load reduction condition; determining the preset voltage scanning slope based on the dynamic capacitance value, and adjusting the rising gradient of the fuel cell stack voltage under the load reduction condition according to the preset voltage scanning slope.

[0098] Specifically, the embodiments of the present application can use a test bench to conduct an accelerated life test on the fuel cell stack. The inherent double-layer capacitance value of the fuel cell stack can be divided into two types. The first is the initial state value, which does not take into account the attenuation effect of the activity of the catalytic layer of the fuel cell stack. The second is the dynamic capacitance value, which takes into account the life attenuation effect during the operation of the stack, and its value can be obtained through the accelerated life test of the stack. When obtaining the initial state value, cyclic voltammetry can be used, that is, a group of triangular wave voltages are used to reverse scan the electrode surface. As Figure 5 shown, the reverse scanning process is the voltage rising stage, and redox current can appear in this stage. The cyclic voltammetry curve can be as Figure 6As shown. The voltage scan slope determines the stack voltage recovery gradient in this stage. According to Equation (1), the initial capacitance value can be calculated, as Figure 7 shown.

[0099]

[0100] where I c is Figure 7 the current value corresponding to point c in d is Figure 7 the current value corresponding to point d in dl C is the initial capacitance value, i H is the hydrogen fuel current.

[0101] When obtaining the dynamic capacitance value, it can be obtained through the stack life acceleration test. Considering the influence of the catalytic layer activity decay, the dynamic capacitance value C dl-dynamic = the capacitance change ΔC measured in the stack life acceleration test dl + the initial capacitance value C dl .

[0102] According to the measured dynamic capacitance value, a suitable voltage scan slope can be set (i.e., determine the preset voltage scan slope), and then the stack voltage recovery speed of the fuel cell stack can be adjusted according to the preset voltage scan slope.

[0103] Furthermore, in some embodiments, adjusting the voltage recovery gradient of the fuel cell stack in the load reduction condition according to the preset voltage scan slope includes: obtaining the initial output voltage of the fuel cell stack in the load reduction condition; obtaining the vehicle demand power, and calculating the target voltage of the fuel cell stack after load reduction according to the vehicle demand power; based on the preset voltage scan slope, controlling the voltage of the fuel cell stack in the load reduction condition to linearly rise from the initial output voltage to the target voltage.

[0104] Specifically, in the load reduction condition, the embodiments of the present application can use the FCCU to online collect the real-time operating stack output voltage (i.e., the initial output voltage of the fuel cell stack in the load reduction condition), and at the same time use the vehicle controller to obtain the vehicle request power, BOP power consumption, lithium battery charging power and the initial stack load reduction power in real time, and transmit the vehicle request power, BOP power consumption, lithium battery charging power and the initial stack load reduction power to the FCCU. The FCCU can calculate the vehicle demand power through a preset algorithm. According to the vehicle demand power, calculate the target voltage of the fuel cell stack after load reduction through the PID control algorithm. By adjusting the bypass valve opening, air compressor speed, etc., make the stack voltage linearly rise from the initial output voltage to the target voltage according to the preset voltage scan slope.

[0105] At this time, the allowable charging electrical energy (maximum value) of the fuel cell stack under the test calibration condition is:

[0106]

[0107] Among them, is the allowable charging power (maximum value) of the stack capacitor, t shedding is the load reduction delay time, C dl is the initial state value of the capacitor, V1 is the target voltage, and V0 is the initial output voltage.

[0108]

[0109] Among them, P charge is the allowable charging power (maximum value) of the lithium battery, P BoP is the BOP power consumption (calculated by the built-in algorithm of FCCU). The stack load reduction delay power refers to the power that the stack output is greater than the power demand of the motor or lithium battery during the load reduction process of the fuel cell commercial vehicle due to the delay in the response of the stack working condition.

[0110] However, in the actual working condition, the actual charging electrical energy of the fuel cell stack is:

[0111] ΔP×t shedding =(P Cdl -P c ′ harge -P BOP )×t shedding ; (4)

[0112] Among them, ΔP is the actual charging power of the stack capacitor, P c ′ harge is the actual charging power of the lithium battery (which can be collected by FCCU).

[0113] Optionally, in some embodiments, the capacitor charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition are obtained, and the total output current of the fuel cell stack under the load reduction condition is controlled based on the vehicle demand current and the capacitor charging current, including: calculating the capacitor charging current according to the dynamic capacitance value and the preset voltage scanning slope; calculating the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitor charging current.

[0114] It should be noted that the total output current of the fuel cell stack under the load reduction condition consists of two parts, namely the vehicle demand current and the capacitor charging current. By precisely controlling the total output current, it can be ensured that the fuel cell stack can not only meet the vehicle current (power) demand under the load reduction condition, but also charge the electric double layer capacitor to recover the excess energy, while avoiding overloading of the fuel cell stack.

[0115] Specifically, the capacitor charging current (for the electric double layer) can be obtained by multiplying the dynamic capacitance value of the current load reduction condition by the preset voltage sweep slope. Therefore, by controlling the speed of voltage recovery (i.e., the preset voltage sweep slope), the magnitude of the capacitor charging current can be adjusted so that the total output current of the fuel cell stack under the load reduction condition satisfies: total output current = vehicle demand current + capacitor charging current.

[0116] Thus, by real-time monitoring the actual operating state of the fuel cell stack and the vehicle demand, and dynamically adjusting the vehicle demand current and the capacitor charging current, the stability and accuracy of current control can be ensured.

[0117] Optionally, in some embodiments, a thermal management system is used to control the cell temperature of the fuel cell stack within a preset temperature range under the load reduction condition, including: obtaining the cell temperature of the fuel cell stack in real time; determining the target flow rate of the coolant according to the cell temperature, and adjusting the rotation speed of the water pump of the thermal management system based on the target flow rate of the coolant; and / or, determining the target rotation speed of the cooling fan according to the cell temperature, and adjusting the rotation speed of the cooling fan of the thermal management system based on the target rotation speed of the cooling fan; and / or, determining the target flow direction of the coolant according to the cell temperature, and adjusting the opening and closing state of the electronic thermostat of the thermal management system based on the target flow direction of the coolant.

[0118] It can be understood that during the energy recovery process of the fuel cell stack under the load reduction condition, since the electric double layer capacitor of the fuel cell stack is in a charging state, the cell temperature rises. By precisely controlling the cell temperature within the preset temperature range, the performance of the fuel cell stack can be optimized, its service life can be extended, and damage caused by excessive temperature can be prevented. In the embodiments of the present application, controlling the cell temperature within the preset temperature range is mainly carried out by controlling the water pump, the electronic thermostat, and the cooling fan, etc.

[0119] Specifically, during the operation of the fuel cell stack, the core temperature of the fuel cell stack is monitored in real time by temperature sensors arranged inside the fuel cell stack, and the temperature sensors feed back the core temperature data to the FCCU; according to the design and operation requirements of the fuel cell stack, a safe operating range of the core temperature (i.e., determining a preset temperature range) is set to prevent the stack from overheating and operating at low temperatures. For the control of the water pump, if the core temperature is too high, increase the water pump speed and increase the coolant flow rate to the target flow rate to enhance the heat dissipation capacity; if the core temperature is too low, reduce the water pump speed and reduce the coolant flow rate to the target flow rate to reduce the heat dissipation intensity. For the control of the cooling fan, if the core temperature is close to the upper limit, increase the cooling fan speed to the target speed to improve the heat dissipation efficiency; if the core temperature is low, reduce the cooling fan speed to the target speed or turn off the cooling fan. For the control of the electronic thermostat, if the core temperature is too high, the electronic thermostat opens to increase the heat dissipation path of the coolant; if the core temperature is too low, the electronic thermostat closes to reduce the heat dissipation path of the coolant. Based on the real-time data fed back by the temperature sensors, the FCCU can dynamically adjust the operating parameters of the thermal management system (such as water pump speed, cooling fan speed, electronic thermostat opening, etc.), thereby maintaining the core temperature within the preset temperature range.

[0120] It should be noted that when controlling the core temperature through the thermal management system, more power needs to be consumed to maintain the core temperature within the safe range. This part of the additional power consumption originally belonged to the available energy of the stack capacitor charging power and now needs to be deducted from the total charging power. Therefore, the actual charging electrical energy of the corrected fuel cell stack is:

[0121] ΔP×t shedding =(P Cdl -P c ′ garge -P BOP -ΔP Coolant )×t shedding ; (5)

[0122] where ΔP is the corrected charging power, and ΔP Coolant is the additional power of the coolant (i.e., the newly added cooling power consumption).

[0123] Thus, in the load reduction condition, the excess energy generated by the delayed response of the fuel cell stack can be converted into heat through the double-layer capacitor charging and discharged outside the stack through the thermal management system to ensure that the core temperature is within the safe range and control the voltage of the fuel cell stack to linearly rise to the target voltage based on the preset voltage sweep slope. Of course, if the ambient temperature is low, the excess heat can be used to warm up the fuel cell stack to optimize the operating conditions of the fuel cell stack.

[0124] Optionally, in some embodiments, based on the vehicle's demand current, the rotation speed of the air compressor and the opening degree of the bypass valve are controlled to adjust the air flow rate entering the fuel cell stack in the load reduction condition, including: determining the target cathode air flow rate entering the fuel cell stack in the load reduction condition based on the vehicle's demand current; controlling the rotation speed of the air compressor and the opening degree of the bypass valve so that the air flow rate entering the fuel cell stack in the load reduction condition meets the target cathode air flow rate.

[0125] It can be understood that the air compressor is the main device for providing air flow rate, and its rotation speed directly affects the air supply. By adjusting the rotation speed of the air compressor, precise control of the air flow rate can be achieved. In the load reduction condition, the rotation speed of the air compressor needs to be reduced to reduce the air flow rate and avoid too rapid a rise in the stack voltage. The bypass valve is used to adjust the air flow rate entering the stack. By controlling the opening degree of the bypass valve, part of the air can be bypassed, thereby reducing the air volume entering the stack. In the load reduction condition, increasing the opening degree of the bypass valve reduces the air flow rate entering the stack, thereby controlling the rate of rise of the stack voltage.

[0126] Based on this, by appropriately controlling the rotation speed of the air compressor and the opening degree of the bypass valve, the air flow rate entering the fuel cell stack in the load reduction condition can be made to meet the target cathode air flow rate, that is, target cathode air flow rate = air flow rate required for the vehicle's demand current + air flow rate required for the capacitor charging current.

[0127] It can be seen from this that the purpose of controlling the opening degree of the bypass valve is to control the cathode inlet air flow rate so that the reverse voltage can rise according to the preset voltage scan slope. At the same time, controlling the intake air volume of the fuel cell stack can make the capacitor charging current controllable and ensure that the stack cell temperature is within the safe range, reducing the risk of stack damage.

[0128] According to the energy recovery method for the fuel cell stack in the load reduction condition proposed by the embodiments of the present application, when the fuel cell stack is in the load reduction condition and there is a load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, the voltage rise gradient, total output current, cell temperature, and air flow rate of the fuel cell stack in the load reduction condition are adjusted to perform energy recovery for the fuel cell stack in the load reduction condition. Thus, the problems in the prior art of high implementation cost and inflexible implementation strategy that cannot better meet the energy recovery requirements under different road conditions and driving demands are solved, and an energy management strategy with low cost and high energy recovery is realized, reducing resource waste and stack loss.

[0129] Next, the energy recovery device for the fuel cell stack in the load reduction condition proposed by the embodiments of the present application is described with reference to the drawings.

[0130] Figure 8 It is a block diagram of the energy recovery device for the fuel cell stack in the load reduction condition according to an embodiment of the present application.

[0131] As Figure 8 shown, the energy recovery device 10 for the load reduction condition of the fuel cell stack includes: a first judgment module 100, a second judgment module 200, and an adjustment module 300.

[0132] Among them, the first judgment module 100 is used to judge whether the fuel cell stack is in the load reduction condition;

[0133] The second judgment module 200 is used to judge whether there is a load reduction response delay phenomenon when the fuel cell stack is in the load reduction condition;

[0134] The adjustment module 300 is used to adjust the voltage recovery gradient, total output current, cell temperature, and air flow of the fuel cell stack in the load reduction condition based on the capacitance characteristics of the fuel cell stack when there is a load reduction response delay phenomenon, so as to recover the energy of the fuel cell stack in the load reduction condition.

[0135] According to an embodiment of the present application, the adjustment module 300 includes:

[0136] The first adjustment unit is used to adjust the voltage recovery gradient of the fuel cell stack in the load reduction condition based on a preset voltage sweep slope by using cyclic voltammetry;

[0137] The first control unit is used to obtain the capacitive charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack in the load reduction condition, and control the total output current of the fuel cell stack in the load reduction condition based on the vehicle demand current and the capacitive charging current;

[0138] The second control unit is used to control the cell temperature of the fuel cell stack in the load reduction condition to be within a preset temperature range by using a thermal management system;

[0139] The second adjustment unit is used to control the rotation speed of the air compressor and the opening degree of the bypass valve based on the vehicle demand current, so as to adjust the air flow entering the fuel cell stack in the load reduction condition.

[0140] According to an embodiment of the present application, the first adjustment unit includes:

[0141] An acquisition subunit is used to obtain the dynamic capacitance value of the fuel cell stack in the load reduction condition by using cyclic voltammetry;

[0142] An adjustment subunit is used to determine a preset voltage sweep slope based on the dynamic capacitance value, and adjust the voltage recovery gradient of the fuel cell stack in the load reduction condition according to the preset voltage sweep slope.

[0143] According to an embodiment of the present application, the adjustment subunit is specifically used for:

[0144] Obtain the initial output voltage of the fuel cell stack under the load reduction condition;

[0145] Obtain the vehicle demand power, and calculate the target voltage of the fuel cell stack after load reduction according to the vehicle demand power;

[0146] Based on the preset voltage scanning slope, control the voltage of the fuel cell stack under the load reduction condition to linearly rise from the initial output voltage to the target voltage.

[0147] According to an embodiment of the present application, the first control unit is specifically configured to:

[0148] Calculate the capacitor charging current according to the dynamic capacitance value and the preset voltage scanning slope;

[0149] Based on the vehicle demand current and the capacitor charging current, calculate the total output current of the fuel cell stack under the load reduction condition.

[0150] According to an embodiment of the present application, the second control unit is specifically configured to:

[0151] Obtain the core temperature of the fuel cell stack in real time;

[0152] Determine the target flow rate of the coolant according to the core temperature, and adjust the rotation speed of the water pump of the thermal management system based on the target flow rate of the coolant;

[0153] And / or, determine the target rotation speed of the cooling fan according to the core temperature, and adjust the rotation speed of the cooling fan of the thermal management system based on the target rotation speed of the cooling fan;

[0154] And / or, determine the target flow direction of the coolant according to the core temperature, and adjust the opening and closing state of the electronic thermostat of the thermal management system based on the target flow direction of the coolant.

[0155] According to an embodiment of the present application, the second adjustment unit is specifically configured to:

[0156] Based on the output current of the fuel cell stack under the load reduction condition, determine the target cathode air flow rate entering the fuel cell stack in the load reduction condition;

[0157] Control the rotation speed of the air compressor and the opening degree of the bypass valve so that the air flow rate entering the fuel cell stack in the load reduction condition meets the target cathode air flow rate.

[0158] It should be noted that the foregoing explanation of the energy recovery method embodiment for the fuel cell stack under the load reduction condition also applies to the energy recovery device for the fuel cell stack under the load reduction condition of this embodiment, and will not be elaborated here.

[0159] The energy recovery device for the fuel cell stack under the load reduction condition proposed in the embodiments of the present application adjusts the voltage recovery gradient, total output current, cell temperature, and air flow of the fuel cell stack under the load reduction condition based on the capacitance characteristics of the fuel cell stack when the fuel cell stack is under the load reduction condition and there is a load reduction response delay phenomenon, so as to recover the energy of the fuel cell stack under the load reduction condition. Thereby, the problems of high implementation cost in the prior art and inflexible implementation strategies, which lead to the inability to better meet the energy recovery requirements under different road conditions and driving demands, are solved, and an energy management strategy with low cost and high energy recovery is realized, reducing resource waste and stack loss.

[0160] Figure 9 The structure diagram of the vehicle provided by the embodiments of the present application. The vehicle may include:

[0161] A memory 901, a processor 902, and a computer program stored on the memory 901 and executable on the processor 902.

[0162] When the processor 902 executes the program, it implements the energy recovery method for the fuel cell stack under the load reduction condition provided in the above embodiments.

[0163] Further, the vehicle further includes:

[0164] A communication interface 903 for communication between the memory 901 and the processor 902.

[0165] The memory 901 is used to store a computer program executable on the processor 902.

[0166] The memory 901 may include a high-speed RAM (Random Access Memory) memory, and may also include a non-volatile memory, such as at least one disk memory.

[0167] If the memory 901, the processor 902, and the communication interface 903 are independently implemented, the communication interface 903, the memory 901, and the processor 902 may be interconnected through a bus and communicate with each other. The bus may be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. For the sake of representation, Figure 9 only a thick line is shown in the figure, but it does not mean that there is only one bus or one type of bus.

[0168] Optionally, in a specific implementation, if the memory 901, the processor 902, and the communication interface 903 are integrated on a single chip, the memory 901, the processor 902, and the communication interface 903 can communicate with each other through an internal interface.

[0169] The processor 902 may be a CPU (Central Processing Unit), or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present application.

[0170] The embodiments of the present application further provide a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the energy recovery method for the fuel cell stack under the load reduction condition as described above is implemented.

[0171] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0172] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0173] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A method for energy recovery in a fuel cell stack load reduction condition, characterized in that: The following steps are involved: Determine whether the fuel cell stack is in a load reduction condition; When the fuel cell stack is in the load reduction condition, determining whether there is a load reduction response delay phenomenon; In the presence of the load reduction response delay phenomenon, based on the capacitance characteristics of the fuel cell stack, the voltage recovery gradient, total output current, cell temperature and air flow of the fuel cell stack under the load reduction condition are adjusted to perform energy recovery under the load reduction condition of the fuel cell stack.

2. The method according to claim 1, characterized in that The step of adjusting the voltage recovery gradient, total output current, cell temperature and air flow of the fuel cell stack under the load reduction condition includes: Using cyclic voltammetry, based on a preset voltage scanning slope, the voltage recovery gradient of the fuel cell stack under the load reduction condition is adjusted; Acquire the capacitor charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition, and control the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitor charging current; Using a thermal management system to control the cell temperature of the fuel cell stack in a load reduction condition to be within a preset temperature range; Based on the vehicle demand current, the speed of the air compressor and the opening of the bypass valve are controlled to adjust the air flow entering the fuel cell stack in the load reduction condition.

3. The method according to claim 2, characterized in that The method of controlling the voltage recovery gradient of the fuel cell stack under the load reduction condition by using cyclic voltammetry based on a preset voltage scanning slope includes: Obtaining the dynamic capacitance value of the fuel cell stack under the load reduction condition by using the cyclic voltammetry method; The preset voltage scanning slope is determined based on the dynamic capacitance value, and the voltage recovery gradient of the fuel cell stack in the load reduction condition is adjusted according to the preset voltage scanning slope.

4. The method according to claim 3, characterized in that The step of adjusting the voltage recovery gradient of the fuel cell stack under the load reduction condition according to the preset voltage scanning slope includes: Obtaining an initial output voltage of the fuel cell stack under the load reduction condition; Obtaining the required power of the whole vehicle, and calculating the target voltage of the fuel cell stack after load reduction according to the required power of the whole vehicle; Based on the preset voltage scanning slope, the voltage of the fuel cell stack is controlled to linearly rise from the initial output voltage to the target voltage in the load reduction condition.

5. The method according to claim 2, characterized in that: The obtaining of the capacitor charging current of the fuel cell stack and the vehicle demand current of the fuel cell stack under the load reduction condition, and controlling the total output current of the fuel cell stack under the load reduction condition based on the vehicle demand current and the capacitor charging current, comprises: Calculating the capacitor charging current according to the dynamic capacitance value and the preset voltage scanning slope; Based on the vehicle demand current and the capacitor charging current, the total output current of the fuel cell stack under the load reduction condition is calculated.

6. The method according to claim 2, characterized in that Using a thermal management system to control the cell temperature of the fuel cell stack in a load reduction condition to be within a preset temperature range includes: Acquiring the cell temperature of the fuel cell stack in real time; determining a target flow rate of the coolant according to the battery core temperature, and adjusting a rotation speed of a water pump of the thermal management system based on the target flow rate of the coolant; and / or, determining a target speed of a heat dissipation fan according to the battery core temperature, and adjusting the speed of the heat dissipation fan of the thermal management system based on the target speed of the heat dissipation fan; And / or, determining a target flow direction of the coolant according to the battery core temperature, and adjusting an open or closed state of an electronic thermostat of the thermal management system based on the target flow direction of the coolant.

7. The method according to claim 2, characterized in that The controlling the speed of the air compressor and the opening of the bypass valve based on the vehicle demand current to adjust the air flow entering the fuel cell stack in the load reduction condition includes: Determining a target cathode air flow rate entering the fuel cell stack in the load reduction condition based on the vehicle demand current; The speed of the air compressor and the opening of the bypass valve are controlled so that the air flow entering the fuel cell stack in the load reduction condition meets the target cathode air flow.

8. An energy recovery device for a fuel cell stack under load reduction conditions, characterized in that: include: The first judgment module is used to judge whether the fuel cell stack is in a load reduction condition; A second judgment module is used to judge whether there is a load reduction response delay phenomenon when the fuel cell stack is in the load reduction working condition; A regulation module is used to adjust the voltage recovery gradient, total output current, cell temperature and air flow of the fuel cell stack under the load reduction condition based on the capacitance characteristics of the fuel cell stack in the presence of the load reduction response delay phenomenon, so as to perform energy recovery of the fuel cell stack under the load reduction condition.

9. A vehicle, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the energy recovery method for a fuel cell stack under load reduction conditions as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the energy recovery method of the fuel cell stack load reduction condition as described in any one of claims 1 to 7.

Images