Multi-stack reforming hydrogen production fuel cell energy management topological structure and control method thereof

Abstract

The invention provides a multi-stack reforming hydrogen production fuel cell energy management topological structure and a control method thereof. The topological structure comprises a fuel cell system processor and a plurality of topological branches, and the output end of the fuel cell system processor is connected with the plurality of topological branches; the topology branch comprises an opening valve, a flow sensor, an electric pile, a DCDC and a relay which are connected in sequence, the input end of the opening valve is connected with the input end of the fuel cell system processor, and the output end of the relay and the lithium battery are connected with a direct-current load or connected with an alternating-current load through an inverter. The energy management system of the reformed fuel cell system is designed aiming at multiple electric piles and considering the influence of variable load frequency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cell technology, in particular, especially relates to a multi-stack reforming hydrogen fuel cell energy management topology and a control method thereof. BACKGROUND

[0002] The reforming fuel cell is pollution-free, high energy conversion efficiency, high specific energy, high specific power, high safety, low characteristic signal, and has a wide application prospect in military and civil fields. However, the fuel reforming fuel cell has the characteristics of long relaxation time and slow load change, and it is difficult to meet the system application alone. The multi-stack fuel cell system needs to solve the power distribution among the multiple stacks to achieve the purpose of prolonging the system life and improving the system efficiency.

[0003] The existing energy management scheme is partly based on the SOC control strategy, which aims to realize the accurate control of the SOC of the power battery, to ensure that the battery works in the safe range, and to prolong the service life of the battery. Part of the power distribution strategy aims to determine the best power distribution mode according to the load demand and the state of the power battery, to realize the highest energy utilization efficiency

[0004] The existing energy management scheme has high requirements for the fuel cell load change speed, low efficiency based on the lithium battery SOC control strategy, and no multi-stack working condition model. The reforming fuel cell system has a longer relaxation time than the pure hydrogen system. Because the reforming hydrogen fuel cell system needs to convert fuel into hydrogen first, it takes a certain period of time to stabilize the conversion of hydrogen, and excessive frequent load change will cause the performance of the reforming hydrogen system and the performance of the stack group. Then the hydrogen is introduced into the stack to generate electricity. Each stack of the stack group has an optimal working interval, and keeping the power distribution of the stack in the optimal working interval can prolong the system life and improve the system efficiency. SUMMARY

[0005] In view of the above-mentioned technical problem that the existing energy management scheme does not consider the influence of the system relaxation time and the load change frequency on the service life and efficiency of the fuel cell, a multi-stack reforming hydrogen fuel cell energy management topology and a control method thereof are provided. The present application designs two-stage energy management, the first stage mainly studies the power distribution between the fuel cell system and the lithium battery, introduces the control parameter of the battery load change time, solves the purpose of improving the system response time and optimizing the control parameter of the fuel cell, and the second stage mainly solves the energy distribution among the multiple fuel cell stacks, introduces the fuel cell health factor for fuel cell power distribution, and improves the overall life of the fuel cell system.

[0006] The technical means adopted by the present application are as follows:

[0007] A multi-stack reforming hydrogen fuel cell energy management topology structure, comprising a fuel cell system processor and a plurality of topology branches, the output end of the fuel cell system processor being connected to the plurality of topology branches;

[0008] The topology branch comprises an opening degree valve, a flow sensor, a stack, a DCDC and a relay connected in sequence, the input end of the opening degree valve being connected to the input end of the fuel cell system processor, and the output end of the relay being connected to a direct current load together with a lithium battery or connected to an alternating current load through an inverter.

[0009] Further, the number of topology branches is greater than or equal to two.

[0010] Further, the inverter is a bidirectional inverter.

[0011] The present application also provides a control method of a multi-stack reforming hydrogen fuel cell energy management topology structure, which is realized based on any one of the above multi-stack reforming hydrogen fuel cell energy management topology structures and comprises the following steps:

[0012] Detecting system load output power; the system load is the sum of a direct current load and an alternating current load;

[0013] Time-integrating the power of fuel cell design variable load time ΔT to obtain load power consumption in ΔT time;

[0014] Calculating average power P req As load demand power, adjusting the total power of the fuel cell stack group to make the average power P req as target power; the specific fuel cell power is calculated according to the lithium battery capacity SOCt at time t to obtain the working power interval P fc [min,max] of the fuel cell; and the working power interval P fc [min,max] of the fuel cell is selected for stage power output.

[0015] Further, the SOCt judgment principle is as follows:

[0016] When the system is started, if SOC>70%, and the load demand power P req is greater than the load power determination threshold P th , the fuel cell is started, and after successful start, the fuel cell is operated at minimum power P min ;

[0017] If the load demand power P req is less than or equal to the load power determination threshold P th , the fuel cell is in standby state.

[0018] When 30%≤SOCt≤70%, the fuel cell state is determined, and if the start is successful, the fuel cell operating point P fc is set to the larger value in the fuel cell operable range P fc [min,max] closest to the load demand power P req ; if 50%≤SOCt≤70%, the fuel cell operating point P fc is set to the smaller value in the fuel cell operable range P fc [min,max] closest to the load demand power P req ;

[0019] If the original state of the fuel cell is the unstarted state, the fuel cell system is started first, and then the output power is determined according to the SOCt and the load demand power;

[0020] If 30%≤SOCt≤70%, the load demand power P req is less than the fuel cell operable power range P fc [min,max] P fcmin , the fuel cell operates at P fcmin , and at this time, the SOC determination is as follows: if SOCt>95%, the fuel cell output power is cut to the discharging resistor discharging;

[0021] If SOCt<30, the fuel cell system operates at the maximum power, and after operating to SOCt>50%, it operates according to the 30%≤SOCt≤70% specification.

[0022] Further, the determination rules of the larger value and the smaller value are as follows:

[0023] The load demand power P req is close to the fuel cell operable range P fc [min,max] downward, and if the smaller value is taken, the calculation result is directly used as the output, and if the larger value is taken, the smaller value plus a ΔP fc power is used as the output.

[0024] Further,

[0025] The fuel cell operable power range P fc [min,max] is determined according to the reforming fuel cell variable load characteristics and the multi-stack debugging operating point, and each stack operating point P st is divided into [P st0 , P st1 , P st2 , P st3 ……Pstm ], working point corresponding efficiency [λ st0 , λ st1 , λ st2 , λ st3 …… λ stm ], fuel cell working power interval P fc [min, max] according to n stack working points P st consisting of, corresponding efficiency points can be calculated.

[0026] Further, when considering the power distribution of each stack of the stack group, the single stack working time t n , the total discharge energy W n , the real-time health status H n , the discharge power distribution of the stack group is carried out.

[0027] Further, when the system is shut down, the fuel cell replenishes the lithium battery power to more than 80% of SOC with the maximum power and the shortest time, so as to meet the subsequent start-up application.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] The multi-stack reforming hydrogen production fuel cell energy management topology provided by the present application realizes the control of the reforming fuel multi-stack through the distribution of the fuel processing hydrogen-rich gas and the discharge management of the multi-stack, and improves the reliability of the system.

[0030] The energy management method provided by the present application combines the lithium battery, the fuel cell and the load characteristics, designs the fuel cell to be always in high-efficiency electric working, and the lithium battery to work in the best working interval, thereby improving the system efficiency.

[0031] The energy management method provided by the present application introduces the health factor, and carries out the power distribution according to the health degree of the stack, thereby improving the service life of the system. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0033] Figure 1 It is a schematic diagram of the topology structure of the present application.

[0034] Figure 2 It is a flow chart of the control method of the present application.

[0035] Figure 3This is a control architecture diagram for an example.

[0036] Figure 4 This is a schematic diagram of the topology of an embodiment. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0040] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0041] like Figure 1As shown, the present invention provides an energy management topology for a multi-stack reforming hydrogen fuel cell, including a fuel cell system processor and several topology branches, wherein the output terminal of the fuel cell system processor is connected to several topology branches;

[0042] The topology branch includes an opening valve, a flow sensor, a fuel cell stack, a DC-DC converter, and a relay connected in sequence. The input terminal of the opening valve is connected to the input terminal of the fuel cell system processor, and the output terminal of the relay is connected to a DC load together with the lithium battery or connected to an AC load through an inverter.

[0043] After the fuel is reformed by the fuel processor, the resulting hydrogen-rich gas passes through N (N≥2) opening valves and N (N≥2) flow sensors at the back end for precise hydrogen control. Each fuel cell stack controls its discharge current through its own DC-DC converter. After discharge, the stack is directly connected in parallel with the lithium battery to output electrical energy. The DC output voltage can be directly used to output electrical energy through the DC-DC converter and lithium battery. If AC power is used, it can be output through an inverter.

[0044] If a single fuel cell stack or several fuel cell stacks experience a fault that could affect the power bus, the controllable relay of the corresponding circuit will automatically disconnect, disconnecting the circuit from the power bus without affecting the system's external power output. The opening valve of the circuit will also be closed to cut off the fuel supply. Once the fault is resolved, the controllable relay will close, allowing the circuit to reconnect to the power bus.

[0045] If a lithium battery is not used for a long time and becomes depleted, this energy management topology can use a bidirectional inverter to charge the system's lithium battery with an external AC power stack.

[0046] like Figure 2 As shown, the present invention also provides a control method for the energy management topology of a multi-stack reforming hydrogen fuel cell, comprising the following steps:

[0047] Detect the system load output power;

[0048] The power consumption during the designed load variation time ΔT of the fuel cell is integrated over time to obtain the load power consumption during the time ΔT.

[0049] Calculate the average power P req As the load demand power, adjusting the total power of the fuel cell stack will reduce the average power P req As the target power, the specific fuel cell power will be determined based on SOCt, and the fuel cell's operating power range P. fc Stage power selection output is performed in [min,max].

[0050] The SOCt judgment principle is as follows: when the system starts up, if SOC > 70%, and the load demand power Preq Greater than the load power determination threshold P th The fuel cell starts up and operates at minimum power after successful startup; P min If the load demand power P req Less than or equal to the load power determination threshold P th The fuel cell is in standby mode. When 30% ≤ SOCt ≤ 70%, the fuel cell status is determined. If startup is successful, the operating point P of the fuel cell is determined based on whether SOCt falls within the range of 30% ≤ SOCt < 50% or 50% ≤ SOCt < 70%. If it falls within the range of 30% ≤ SOCt < 50%, the fuel cell operating point P is determined. fc Set in the operating range P of the fuel cell fc The closest power P to the load demand is in [min, max]. req The larger value in the range; if 50% ≤ SOCt ≤ 70%, then the fuel cell operating point P fc Set in the operating range P of the fuel cell fc The closest power P to the load demand is in [min, max]. req The smaller of the values ​​in the range; if the fuel cell is in an unstarted state, start the fuel cell system first, and then determine the output power based on SOCt and load demand power; if 30% ≤ SOCt ≤ 70%, the load demand power P req Less than the operating power range P of the fuel cell fc In the [min,max] region, Pfcmin indicates that the fuel cell operates at P... fcmin During operation, the SOC determination is as follows: if SOCt > 95%, the fuel cell output power is switched to discharge resistor for discharge; if SOCt < 30%, the fuel cell system operates at maximum power until SOCt > 50%, and then operates according to the specification of 30% ≤ SOCt ≤ 70%.

[0051] The fuel cell has an operating power range P fc [min,max] are determined based on the load variation characteristics of the reformed fuel cell and the commissioning operating points of multiple stacks. Each stack operating point P is determined. st Divided into [P] st0, P st1 ,P st2 ,P st3 ...P stm The efficiency corresponding to the working point [λ] st0 ,λ st1 ,λ st2 ,λ st3 ……λ stm The operating power range P of a fuel cell fc [min,max] are based on n fuel cell operating points P. st The composition and corresponding efficiency points can be calculated.

[0052] When considering the power allocation of the fuel cell stack to each fuel cell stack, the operating time t of a single fuel cell stack is introduced. n Total discharge energy W n Real-time health status H n Discharge power distribution of the fuel cell stack is carried out.

[0053] When the system shuts down, the fuel cell replenishes the lithium battery to over 80% SOC in the shortest time and at maximum power to meet the requirements for restarting the application.

[0054] Example 1

[0055] Please see Figure 3 A four-stack reforming hydrogen fuel cell energy management and control architecture, wherein the data acquisition module collects system feed fuel type, feed molar quantity, inlet gas molar quantity, inlet water molar quantity, inlet gas-liquid pressure, temperature, and ambient gas pressure parameters. (See reference...) Figure 4 In-feed monitoring module; collects temperature and pressure information from different sections of the processor (see reference). Figure 4 The processor monitoring module collects information such as voltage, temperature, humidity, and pressure of each cell in the fuel cell stack within the system. Figure 4 The battery stack monitoring module collects parameters such as voltage, current, and lithium battery SOC. (See also: [link to system details]). Figure 4 The monitoring module for China Power Energy; see the system for information on whether there are leaks of electricity, gas, or liquids. Figure 4 The system monitoring module performs filtering on the collected raw data, using physical filtering methods such as Chebyshev filters and digital filtering methods such as median filtering algorithms.

[0056] Data is collected to determine the current status of each energy management module. By comparing the system flow control, component control logic, and final drive control, the current status of the energy management system is assessed. The assessment structure is divided into four categories: No fault, the energy management system can discharge normally; Fault Level 1, the system has a fault that does not affect performance, a prompt is given in the human-machine interface module, and the energy management system discharges normally; Fault Level 2, the system has a more serious fault, a prompt is given in the human-machine interface, and the energy management output power is limited to 60% of the output power, as specified in the system; Fault Level 3, the system has a serious fault, a prompt is given in the human-machine interface, and the system shuts down urgently.

[0057] Process control includes control logic for processor feeding and stack discharge power allocation based on collected load changes, and includes execution strategies for the energy management system's startup, operation, shutdown, and emergency stop.

[0058] The control logic module mainly performs a related operation. For example, when the power demand of the fuel cell stack needs to be increased, the control logic module performs feed adjustment, gas path distribution, and DC-DC discharge.

[0059] The drive control module executes specific control of the corresponding components, including PWM control, CAN control, analog current and voltage control, dry contact, wet contact control, etc. In this case, the feeding system uses PWM and analog current and voltage control methods, the water pump uses PWM control, the DC-DC converter uses CAN control, and the corresponding contactors use wet contact control.

[0060] Example 2

[0061] Please see Figure 4 Furthermore, based on Example 1, the method for collecting battery SOC is the voltage-corrected current integration method. 100% SOC is when the voltage of a single ternary lithium battery cell reaches 4.25V. The real-time SOCt is equal to the full ampere-hours minus the discharge current integrated over time.

[0062] The load power Preq is taken as Δt = 600 seconds, and the power Pload is integrated over time to obtain the discharge energy W over Δt = 600 seconds. Δt Preq = W Δt / 600 seconds;

[0063] The discharge power range of a single fuel cell stack is {2.5kW, 5kW, 9.6kW, 13.8kW, 17.6kW, 21.2kW, 24.6kW}. Therefore, the adjustable power range of the fuel cell stack {2.5kW~98.4kW} corresponds to an efficiency {λ1~λ n The cumulative operating time of the fuel cell stack is {t1~t4}, the discharged electrical energy is {W1~W4}, and the health status is monitored in real time {H1~H4}.

[0064] Figure 3 The intermediate process control module calculates the required output power of the fuel cell stack based on the SOC, fuel cell output power demand Preq, and stack power range obtained by the above method, thereby adjusting the fuel feed rate. The secondary identification algorithm in the process control then uses four real-time stack health evaluation parameters {H1~H4}, cumulative stack operating time {t1~t4}, discharge energy {W1~W4}, and corresponding efficiencies {λ1~λ n The stack power distribution achieves a dual consideration of system lifespan and efficiency for reformed hydrogen fuel cell systems.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A topology for energy management of a multi-stack reforming hydrogen fuel cell, characterized in that: It includes a fuel cell system processor and several topology branches, with the output of the fuel cell system processor connected to the several topology branches; The topology branch includes an opening valve, a flow sensor, a fuel cell stack, a DC-DC converter, and a relay connected in sequence. The input terminal of the opening valve is connected to the input terminal of the fuel cell system processor, and the output terminal of the relay is connected to a DC load together with the lithium battery or connected to an AC load through an inverter.

2. The energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 1, characterized in that, The number of the topological branches is greater than or equal to two.

3. The energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 1, characterized in that, The inverter is a bidirectional inverter.

4. A control method for an energy management topology of a multi-stack reformed hydrogen fuel cell, implemented based on the energy management topology of a multi-stack reformed hydrogen fuel cell as described in any one of claims 1-3, characterized in that, Includes the following steps: The system load output power is detected; the system load is the sum of a DC load and an AC load. The power consumption during the designed load variation time ΔT of the fuel cell is integrated over time to obtain the load power consumption during the time ΔT. Calculate the average power P req As the load demand power, adjusting the total power of the fuel cell stack will reduce the average power P req The target power is used as the power output; the specific fuel cell power will be calculated based on the lithium battery's capacity SOCt at time t, yielding the fuel cell's operating power range P. fc [min,max]; defines the operating power range P of the fuel cell. fc Stage power selection output is performed in [min,max].

5. The control method for the energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 4, characterized in that, The SOCt determination principle is as follows: When the system starts up, if the SOC > 70%, and the load demand power P req Greater than the load power determination threshold P th The fuel cell starts up, and after successful startup, it operates at minimum power P. min run; If the load demand power P req Less than or equal to the load power determination threshold P th The fuel cell is in standby mode; When 30% ≤ SOCt ≤ 70%, the fuel cell status is determined. If startup is successful, the fuel cell operating point P is determined based on whether SOCt falls within the 30% ≤ SOCt < 50% or 50% ≤ SOCt < 70% range. If it falls within the 30% ≤ SOCt < 50% range, the fuel cell operating point P is determined. fc Set in the operating range P of the fuel cell fc The closest power P to the load demand is in [min, max]. req The larger value in the range; if 50% ≤ SOCt ≤ 70%, then the fuel cell operating point P fc Set in the operating range P of the fuel cell fc The closest power P to the load demand is in [min, max]. req The smaller value in the middle; If the fuel cell was not started, the fuel cell system should be started first, and the output power should be determined based on the SOCt and the load power demand. If 30% ≤ SOCt ≤ 70%, the load power demand P req Less than the operating power range P of the fuel cell fc P in [min,max] fcmin Then the fuel cell uses P fcmin During operation, if the SOC is greater than 95%, the fuel cell output power is switched to discharge resistor for discharge. If SOCt < 30, the fuel cell system operates at maximum power until SOCt > 50%, then operates according to the specification of 30% ≤ SOCt ≤ 70%.

6. The control method for the energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 5, characterized in that, The rules for judging the larger and smaller values ​​are as follows: Load demand power P req According to the operating range P of fuel cells fc The [min,max] rule tends to move downwards. If a smaller value is taken, the calculated result is used directly as the output. If a larger value is taken, the smaller value is added to a ΔP. fc Power is used as output.

7. The control method for the energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 5, characterized in that, The fuel cell has an operating power range P fc [min,max] are determined based on the load variation characteristics of the reformed fuel cell and the commissioning operating points of multiple stacks. Each stack operating point P is determined. st Divided into [P] st0 ,P st1 ,P st2 ,P st3 ...P stm The efficiency corresponding to the working point [λ] st0 ,λ st1 ,λ st2 ,λ st3 ……λ stm The operating power range P of a fuel cell fc [min,max] are based on n fuel cell operating points P. st The composition and corresponding efficiency points can be calculated.

8. The control method for the energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 4, characterized in that, When considering the power allocation of the fuel cell stack to each fuel cell stack, the operating time t of a single fuel cell stack is introduced. n Total discharge energy W n Real-time health status H n Discharge power distribution of the fuel cell stack is carried out.

9. The control method for the energy management topology of a multi-stack reforming hydrogen fuel cell according to claim 4, characterized in that, When the system shuts down, the fuel cell replenishes the lithium battery to over 80% SOC in the shortest time and at maximum power to meet the requirements for restarting the application.

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