A hydrogen fuel cell air path flow detection control system and method

Abstract

The present application relates to the field of hydrogen fuel cell, especially to a kind of hydrogen fuel cell air path flow detection control system and method.The system includes fixed hydrogen fuel cell power station air centralized supply module and stack module.The method includes S1, obtaining different current under the pressure demand of stack inlet and the flow demand Q m Corresponding relationship;S2, decoupling control is carried out to pressure sensor Pn-2, so that the flow reaches Q m And the pressure reaches target pressure b;S3, the control of pressure sensor Pn-3 and air flow, under the flow resistance balance adjustment effect before the inlet of stack, reaches target flow coefficient, while keeping the flow to reach Q m The present application realizes flow control by air pressure control, meets the flow control demand of full range, avoids the problem of high cost of using high-pressure air flowmeter or air flow controller;This power station realizes functional partition and modular arrangement, and has higher integration degree and is convenient to maintain.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen fuel cells, in particular to a hydrogen fuel cell air path flow detection control system and method. BACKGROUND

[0002] Air flow is a key control parameter of proton exchange membrane fuel cells, which has an important influence on the gas transmission efficiency, electrochemical reaction rate and overall performance of hydrogen fuel cells. Providing accurate flow for hydrogen fuel cells according to different working conditions is of great significance to ensure the performance and service life of fuel cells.

[0003] At present, common air supply solutions for hydrogen fuel cell fixed power stations are generally divided into two schemes: independent air supply and centralized air supply. The independent air supply scheme usually adopts a direct integration of fuel cell systems, and each air system needs an air compressor, an air flow meter or an air flow controller. The centralized air supply scheme usually adopts one or more high-power air compressors for air supply, and the air supply pressure is stabilized through an air buffer tank. The air flow control is realized by using a high-pressure air flow meter or an air flow controller at the front end of the power module air supply.

[0004] In the existing independent air supply scheme, each air system needs an air compressor, an air flow meter or an air flow controller. The air flow meter usually adopts a thermal flow meter, which has strict requirements for the length of the straight section of the pipeline before and after installation. The insufficient straight section of the pipeline directly affects the measurement accuracy, so the overall layout form has low integration and modularity. In the centralized air supply scheme, the air pressure in the air buffer tank is usually maintained at a relatively high pressure value. Traditional low-pressure flow meters cannot be used, and high-pressure air flow meters need to be used, which is more expensive. If an air flow controller is used, the cost is also high. In the current industry, the cost is more sensitive, and the use of high-pressure air flow meters or air flow controllers will increase the cost and reduce the competitiveness of the product. SUMMARY

[0005] In view of the problems in the background art, a hydrogen fuel cell air path flow detection control system and method are proposed. The flow control is realized by air pressure control, which meets the full-range flow control requirement and avoids the high cost problem of using high-pressure air flow meters or air flow controllers. At the same time, this power station can realize functional partitioning and modular arrangement, has higher product integration, is convenient for later maintenance, and reduces the system operation cost.

[0006] The application provides a hydrogen fuel cell air path flow detection control system, which comprises an air centralized supply module and a stack module.

[0007] The application further provides a hydrogen fuel cell air path flow detection control method.

[0008] S1, obtaining stack inlet pressure requirements and stack inlet flow requirements Q under different currents m corresponding relationship;

[0009] S2, decoupling control is performed on the pressure sensor Pn-2, so that the flow reaches Q m , and the pressure reaches the target pressure b at the same time;

[0010] S3, control is performed on the pressure sensor Pn-3 and the air flow, so that the target flow coefficient is reached under the regulation of the flow resistance balance in the front section of the stack inlet, and the flow reaches Q m .

[0011] Preferably, the specific steps of S1 are as follows:

[0012] S11, calculating the stack air flow requirements Q according to different working points of each stack m The formula is: , is an air excess coefficient, is an air molecular weight, is the number of stack sheets, is a working current, is the mass fraction of O2 in air, is the number of transferred charges, is the Faraday constant;

[0013] S12. Calculate the relationship between current and air flow rate for each of the n parallel fuel cell sub-modules in the fuel cell module under individual operating conditions according to the above formula, and obtain the relationship between current and flow rate.

[0014] S13. According to the fuel cell stack product manual, obtain the metering ratio of flow demand under different current conditions. and air pressure;

[0015] S14. After understanding the relationship between different currents and air pressures in the fuel cell submodules, based on the relationship between current and air flow obtained in S12, and in conjunction with the fuel cell product manual, the relationship between air pressure and air flow under different currents is obtained. This leads to the fuel cell inlet pressure requirement and fuel cell inlet flow requirement Q under different currents. m Correspondence.

[0016] Preferably, the specific steps of S2 are as follows:

[0017] S21. The reference pressure of the air buffer tank is set to a, and air is replenished in real time by running the air compressor to make the pressure fluctuation range of the air buffer tank ±0.2a.

[0018] S22 and Pn-2 are set as target pressure b, based on the stack inlet pressure requirement and stack inlet flow requirement Q under different currents. m Corresponding relationship, for the fuel cell stack inlet flow requirement Q under different operating currents. m And to calibrate the opening of regulating valve n-1 for different pressure values ​​'a' inside the air buffer tank;

[0019] S23. During calibration, refer to the calibration parameters of the control valve n-1 opening, and apply them at different Q values. m Under different Pn-1 pressures, pressure control after Pn-2 is achieved by setting different opening values ​​of regulating valve n-1, thus maintaining the flow rate at Q. m At the same time, the pressure reaches b.

[0020] Preferably, the specific steps of S3 are as follows:

[0021] S31. Based on the stack inlet pressure and stack inlet flow requirements Q under different current conditions. m The corresponding relationship is used to determine the flow rate requirement Q of the fuel cell stack at different operating conditions. m And the required pressure value of Pn-3, determine the pressure relationship between Pn-2 and Pn-3, and determine whether the air medium is a critical flow or a non-critical flow;

[0022] Noncritical flow: Pn-3 > Pn-2 / 2,

[0023] (1);

[0024] Critical flow: Pn-3 < Pn-2 / 2,

[0025] (2);

[0026] Wherein, Gas flow under standard conditions; Pn-2 and Pn-3 before and after the pressure difference of the regulating valve, The gas density under standard conditions; Represent the flow coefficient;

[0027] S32, according to the temperature sensor acquisition value Tn before the regulating valve n-2, then according to the above formula (1) or formula (2) calculation, get the flow coefficient value of regulating valve n-2 under different working current of the electric pile ;

[0028] S33, according to the demand flow coefficient value determined in the last step And the opening and flow coefficient curve of regulating valve n-2, determine the target opening value of regulating valve n-2, adjust the regulating valve n-2 to reach the target opening value, so that the front section flow resistance of the electric pile inlet reaches the target flow coefficient under the balance adjustment of the regulating valve n-2, while keeping the flow to Q m .

[0029] Compared with the prior art, the present application has the following beneficial technical effects:

[0030] 1. Cost and energy efficiency breakthrough: using air buffer tank to stabilize pressure (fluctuation ±0.2a), so that the air compressor only needs threshold start and stop, reduces power consumption and prolongs service life; save high-precision flowmeter, replace flow controller with pressure sensor, reduce hardware cost;

[0031] 2. Precise control of all working conditions: two-stage pressure decoupling, regulating valve n-1 dynamic compensation buffer tank pressure fluctuation (table control, precision ±1%), to ensure that the secondary pressure Pn-2 is stable at the target value b; critical flow self-adaptation, according to the pressure relationship between Pn-3 and Pn-2 to switch the flow coefficient formula (formula 1 or formula 2), combined with the valve n-2 calibration curve to realize the flow Q m Error control; back pressure coordination, valve n-3 auxiliary PI regulates the electric pile inlet pressure Pn-3, eliminates the influence of valve hysteresis;

[0032] 3. Modularity and reliability: parallel electric pile submodules support flexible expansion of megawatt power station, single module maintenance does not affect system operation; multi-node pressure sensor (Pn-1 to Pn-4) realizes real-time diagnosis of pipeline fault, and the anti-disturbance ability is improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a hydrogen fuel cell air path flow detection control system structure block diagram;

[0034] Figure 2 This is a graph showing the relationship between the opening degree of regulating valve n-2 and the flow coefficient. Detailed Implementation

[0035] Example 1: This example proposes a hydrogen fuel cell air path flow detection and control system, such as... Figure 1 As shown, it includes a centralized air supply module and an electric stack module.

[0036] The centralized air supply module includes an air filter, an air compressor, and an air buffer tank connected sequentially along the air delivery direction. This part meets the air flow requirements of the fuel cell stack module. By adding the air buffer tank, an air compressor that meets the maximum air flow requirements of multiple fuel cell stack modules can be adapted. Unlike traditional fuel cells, the air compressor power and MPA do not need to be matched to the flow and pressure ratio requirements of different power points. The air compressor only needs to ensure that the pressure in the buffer tank is within a certain pressure range. The air compressor can start working when the pressure is below a certain value and stop working when the pressure is above a certain value, so as to ensure that the pressure in the air buffer tank is stable within a certain range.

[0037] The fuel cell stack module comprises multiple fuel cell sub-modules. Each sub-module includes a kilowatt-level fuel cell stack, a humidifier, regulating valves n-1, n-2, and n-3, pressure sensors Pn-1, Pn-2, Pn-3, and Pn-4, and a temperature sensor Tn. The multiple fuel cell sub-modules are connected by parallel pipelines. The air inlet of the parallel pipelines is connected to an air buffer tank device, and the air outlet is a tailpipe. n represents the group of the parallel fuel cell sub-modules.

[0038] The regulating valve n-1 and pressure sensor Pn-3 are installed on the pipeline between the fuel cell stack inlet and the humidifier outlet; the regulating valve n-3 and pressure sensor Pn-4 are installed on the pipeline between the fuel cell stack outlet and the first humidifier inlet; the temperature sensor Tn, pressure sensor Pn-1, regulating valve n-1 and regulating valve n-2 are installed on the parallel pipeline and located at the front end of the second humidifier inlet.

[0039] The fuel cell stack module meets the power requirements of megawatt-level or higher fuel cell power plants, and through the control of regulating valves and pressure sensors, it achieves precise control of the flow requirements of the fuel cell stack under different operating conditions.

[0040] Example 2: This invention further proposes a method for detecting and controlling the air flow rate of a hydrogen fuel cell, employing the hydrogen fuel cell air flow rate detection and control system described in Example 1. The steps are as follows:

[0041] S1. Obtain the table showing the relationship between the fuel cell stack inlet pressure requirement and the fuel cell stack inlet flow requirement Qm under different currents;

[0042] S11, according to the fuel cell operating characteristics, the fuel cell at different operating points (different operating current density I) The required air flow (AirFlowTgt) and air pressure (AirPreTgt) are different, and the air flow and air pressure need to be controlled according to the actual working condition;

[0043] According to the different working points of each electric pile, the electric pile air flow demand Q is calculated m The formula is: , The air excess coefficient is, The air molecular weight is, The number of electric pile pieces is, The working current is, The mass fraction of O2 in air is, The number of transferred charges is, The Faraday constant is;

[0044] S12, according to the above formula, the corresponding relationship between current and air flow of each electric pile sub-module in the n parallel electric pile sub-modules in the electric pile module under the single operation state is calculated, and a current-flow correspondence table is obtained.

[0045] S13, under different currents, the electric pile demand pressure is also different, which can be directly obtained from the electric pile product manual to query the flow demand ratio under different currents And air pressure;

[0046] S14, after knowing the corresponding relationship between different currents and air pressures of the electric pile sub-module, according to the corresponding relationship between current and air flow obtained by S12, combined with the electric pile product manual, the corresponding relationship between air pressure and air flow under different currents is obtained, and the electric pile inlet pressure demand and electric pile inlet flow demand Q m Corresponding relationship table, table 1;

[0047] Table 1 Electric pile flow and pressure demand table

[0048] .

[0049] S2, decouple control is performed on the pressure sensor Pn-2, so that the flow reaches Q m , and the pressure reaches the target pressure b;

[0050] In actual work process, Pn-1 represents the pressure of the air buffer tank, and there will be a certain amplitude of pressure fluctuation, and the opening value of the regulating valve n-1 needs to be controlled according to the actual pressure of Pn-1 to meet the stability of the pressure sensor Pn-2, but when controlling the regulating valve n-2, the pressure of Pn-2 will also be coupled to change, resulting in too large control difficulty; in order to solve this problem, the decoupling control scheme is adopted to independently control the regulating valve n-1 and the regulating valve n-2;

[0051] The specific steps of S2 are:

[0052] S21, the reference pressure of the air buffer tank is set as a, and the air buffer tank pressure fluctuation amplitude is ±0.2a through real-time air supply of the air compressor;

[0053] S22, Pn-2 is set as the target pressure b (determine the value of b according to the pipeline flow resistance of each group of stacks and the stack demand pressure value), and the regulating valve n-1 opening is calibrated according to the stack inlet pressure demand and the stack inlet flow demand Q m under different working currents, and the stack inlet flow demand Q m and the air buffer tank pressure value a are calibrated;

[0054] S23, the related parameters in the regulating valve n-1 opening calibration parameter table are referred to during calibration, as shown in Table 2; under different Q m and different Pn-1 pressures, the opening value of the regulating valve n-1 is set to realize the pressure control after Pn-2, and the flow reaches Q m , and the pressure reaches b;

[0055] The blank of the regulating valve n-1 opening calibration parameter table is the opening calibration result of the regulating valve n-1 according to different conditions, and then the opening value table of the regulating valve n-1 under different currents and different buffer tank pressures in the calibrated regulating valve n-1 opening calibration parameter table is written into the fuel cell system control software, and the opening of the valve n-1 is controlled and executed in the form of table lookup (corresponding to current and buffer tank pressure) during work to realize the control of the target pressure of Pn-2;

[0056] In actual application, the buffer tank pressure can be more finely divided, for example, divided into 0.8a, 0.85a, 0.9a, …, 1.15a, 1.2a to realize more accurate Pn-2 pressure control;

[0057] Table 2 regulating valve n-1 opening calibration parameter table

[0058] .

[0059] S3, control of the pressure sensor Pn-3 and air flow, to reach the target flow coefficient under the flow resistance balance regulation effect of the front section of the stack inlet, while keeping the flow to Q m ;

[0060] The specific steps of S3 are:

[0061] S31, according to the stack inlet pressure requirement and stack inlet flow requirement Q m of different currents, determine the flow requirement Q m of different working points of the stack, and the Pn-3 requirement pressure value (corresponding to the stack inlet pressure requirement), judge the pressure relationship between Pn-2 and Pn-3, determine whether the air medium is critical flow or non-critical flow;

[0062] Formula 1 and formula 2 are flow coefficient calculation formulas, and the calculation formulas of critical flow and non-critical flow are different, which need to be judged according to the pressure to select which calculation formula;

[0063] Non-critical flow: Pn-3>Pn-2 / 2,

[0064] (1);

[0065] Critical flow: Pn-3

[0066] (2);

[0067] Wherein, Gas flow under standard conditions; Pn-2 and Pn-3 are the pressure difference before and after the regulating valve, The gas density under standard conditions; Represent the flow coefficient;

[0068] S32, according to the temperature sensor acquisition value Tn before the regulating valve n-2, then according to the above formula (1) or formula (2) calculation, get the regulating valve n-2 flow coefficient value under different working current of the stack ;

[0069] S33, according to the requirement flow coefficient value determined in the above step, and the opening and flow coefficient curve of the regulating valve n-2 (provided by the regulating valve manufacturer), determine the target opening value of the regulating valve n-2, adjust the regulating valve n-2 to reach the target opening value, so that the front section of the stack inlet reaches the target flow coefficient under the flow resistance balance regulation effect, while keeping the flow to Q m .

[0070] For example Figure 2The vertical coordinate is flow coefficient, and the horizontal coordinate is the opening degree of the regulating valve n-2; the regulating valve characteristic is a closed loop curve because of the hysteresis phenomenon of the open and closed valves.

[0071] The stack operation not only needs flow but also needs to control the inlet pressure Pn-3 to reach the target value; under different currents, the pressure value of Pn-2 is b, and the single pressure sensor Pn-3 needs to reach the pressure value under the current in Table 1, so the opening degrees of the valves n-3 and n-2 need to be adjusted. According to the previous calibration, the feedforward values of the regulating valves n-2 and n-3 under different currents are given and written into the software, and in the actual control process, the opening degrees of the valves n-2 and n-3 are adjusted according to the PI parameters to make them meet the pressure requirement of Pn-3 and reach the target value. Therefore, the regulating valve n-3 is added to play a back pressure role, and the regulating valve n-3 and the auxiliary regulating valve n-2 of the regulating valve n-2 are adjusted to supplement the adjustment.

[0072] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited thereto, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

Claims

1. A hydrogen fuel cell air path flow rate detection control method characterized by, The application relates to a hydrogen fuel cell air path flow detection control system, which comprises the following components: An air centralized supply module, which comprises an air filter, an air compressor and an air buffer tank device connected in sequence along an air conveying direction; An electric pile module, which comprises a plurality of electric pile submodules, each submodule comprising an electric pile, a humidifier, a regulating valve n-1, a regulating valve n-2, a regulating valve n-3, a pressure sensor Pn-1, a pressure sensor Pn-2, a pressure sensor Pn-3, a pressure sensor Pn-4 and a temperature sensor Tn; the plurality of electric pile submodules are communicated through a parallel pipeline, the parallel pipeline is communicated with the air buffer tank device at an air inlet end and is communicated with an air outlet end tail; The regulating valve n-2 and the pressure sensor Pn-3 are arranged on a pipeline between an electric pile air inlet and a humidifier air outlet; The regulating valve n-3 and the pressure sensor Pn-4 are arranged on a pipeline between an electric pile air outlet and a humidifier air inlet; The temperature sensor Tn, the pressure sensor Pn-1, the regulating valve n-1 and the pressure sensor Pn-2 are arranged on the parallel pipeline and located in front of a humidifier air inlet two end; The control method of the hydrogen fuel cell air path flow detection control system is as follows: S1, obtaining pressure requirement and flow requirement Q of stack inlet under different currents m corresponding relationship; S2, decoupling control is performed on the pressure sensor Pn-2 so that the flow rate reaches Q m , and the pressure reaches the target pressure b simultaneously S3. Control of pressure sensor Pn-3 and air flow to achieve target flow coefficient under influence of pre-stack flow resistance balancing adjustment at stack inlet, while maintaining flow to Q m .

2. The hydrogen fuel cell air path flow rate detection control method according to claim 1, characterized by, The specific steps of S1 are as follows: S11. Calculate the air flow requirement Q of the stack according to different working points of each stack m The formula is: , is the air excess coefficient, is the air molecular weight, is the number of stack sheets, is the working current, is the mass fraction of O2 in air, is the number of transferred charges, is the Faraday constant; S12, the corresponding relationship between the current and the air flow of each electric pile submodule in the n parallel electric pile submodules in the electric pile module in a single running state is obtained according to the above formula, and the corresponding relationship between the current and the flow is obtained. S13, according to the product manual query to get different current, flow demand metering ratio and air pressure; S14, after knowing the corresponding relationship between the different currents and air pressures of the stack sub-module, the corresponding relationship between the current and air flow obtained in S12 is combined with the stack product manual to obtain the corresponding relationship between the air pressure and air flow under different currents, and further obtain the stack inlet pressure requirement and stack inlet flow requirement Q under different currents m corresponding relationship.

3. The hydrogen fuel cell air path flow rate detection control method according to claim 2, characterized by, The specific steps of S2 are as follows: S21, the air buffer tank reference pressure is set as a, the air buffer tank pressure fluctuation range is + / -0.2a through air compressor running real-time air supply; S22, Pn-2 is set as the target pressure b, according to the stack inlet pressure demand and the stack inlet flow demand Q under different currents m Corresponding relationship, for the stack inlet flow demand Q under different working currents m And different pressure values a in the air buffer tank, the opening degree calibration of the regulating valve n-1 is carried out; S23, refer to the adjustment valve n-1 opening degree calibration parameters, at different Q m And different Pn-1 pressure, by setting the different adjustment valve n-1 opening value to achieve Pn-2 after the pressure control, keep the flow to Q m At the same time, the pressure reaches b.

4. The hydrogen fuel cell air path flow rate detection control method according to claim 3, characterized by, The specific steps of S3 are as follows: S31, according to the stack inlet pressure requirement and the stack inlet flow requirement Q under different currents m Corresponding relationship, determine the flow requirement Q of different working points of the stack m And the pressure relationship between Pn-2 and Pn-3 is judged, and it is determined whether the air medium is critical flow or non-critical flow; Non-critical flow: Pn-3>Pn-2 / 2, （1）； Critical flow: Pn-3 （2）； wherein, gas flow rate at standard conditions; Pn-2 and Pn-3 adjustment valve before and after pressure difference, gas density at standard conditions; represent the flow coefficient; S32, according to the temperature sensor before the adjusting valve n-2 acquisition value Tn, then according to the above formula (1) or formula (2) calculation, get the different working current under the regulating valve n-2 flow coefficient value ; S33, determining the demand flow coefficient value according to the last step And the opening degree and flow coefficient curve of the regulating valve n-2, determine the target opening degree value of the regulating valve n-2, adjust the regulating valve n-2 to the target opening degree value, so that the front section flow resistance of the stack reaches the target flow coefficient under the balance adjustment of the regulating valve n-2, while keeping the flow to Q m .

5. The hydrogen fuel cell air path flow rate detection control method according to claim 4, characterized by, The Pn-3 demand pressure value is an electric pile inlet pressure demand value.

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