CN117996119A - Heat management system for standby power supply of fuel cell of transformer substation and control method of heat management system - Google Patents

Abstract

The present invention discloses a thermal management system for a fuel cell backup power supply for a substation and a control method thereof. The system includes a fuel cell stack, a filter, a main cooling circuit water pump, a three-way valve, a main cooling circuit radiator, a PTC electric heater, a cathode and anode gas heat exchangers, a secondary cooling circuit water pump, a secondary cooling circuit radiator, an RS485 bus, a controller and other structures. The fuel cell backup power supply for a substation using a new alloy hydrogen storage technology provides a thermal management solution, so that the system also has control methods for three operating modes: stack heating, stack heat dissipation and stack heat dissipation. The present invention solves the heat dissipation problem when the fuel cell is used as a station power supply for a long time and the problem of rapid cold start in a low temperature environment, and can effectively improve the accuracy of stack temperature control.

Description

A thermal management system for a fuel cell backup power supply in a substation and a control method thereof

Technical Field

The present invention belongs to the field of thermal management of fuel cells as large-scale power supply, and more specifically, relates to a thermal management system for a fuel cell backup power supply of a transformer substation and a control method thereof.

Background technique

A fuel cell is a chemical device that converts chemical energy stored in fuel directly into electrical energy. Hydrogen is usually used as fuel and passed into the anode, and air is used as an oxidant and passed into the cathode for reaction. The reaction product is water. Fuel cells can be divided into proton exchange membrane fuel cells (PEMFC), alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC) according to the electrolyte. Among them, proton exchange membrane fuel cells have the advantages of being environmentally friendly, highly reliable, fast startup time, high energy conversion efficiency and low operating temperature, and are very suitable for use as a backup power source for substations.

Backup power supply is an important device to ensure the reliability of power supply for substations. In view of the low energy density, inconvenient maintenance, poor environmental friendliness, and short replacement cycle of traditional lead-acid batteries and diesel generators as backup power supplies, the introduction of fuel cells as a new type of station power supply, the use of new metal hydride hydrogen storage technology, and the study of new substation backup power supply architecture combined with high-efficiency power electronic conversion technology will help solve the AC/DC split problem of traditional substation power supply systems and build a new, efficient, and safe green substation power supply system.

The ideal operating temperature range of proton exchange membrane fuel cells is about 60℃-80℃, and changes in the temperature of the stack have a significant impact on the performance of the fuel cell. Complex electrochemical reactions are taking place inside the fuel cell. While providing electrical energy, they are often accompanied by a large amount of heat generation, which causes the temperature of the stack to rise. On the one hand, when the fuel cell is running at high power and for a long time, a reasonable heat dissipation system is often required to control the temperature to prevent the operating temperature from exceeding the upper limit and local overheating; on the other hand, in a low temperature environment, the heat generated by the electrochemical reaction of the fuel cell may not be able to maintain the system at a suitable temperature, or face the problem of the fuel cell starting too slowly or even failing to start normally. At this time, the original cooling circuit needs to be used to assist in heating the fuel cell stack. Studies have shown that about 8% of the cost in a fuel cell system belongs to thermal management. Therefore, it is crucial to design a thermal management system for fuel cells based on specific application scenarios.

Metal hydride hydrogen storage is a new type of hydrogen storage technology, which uses hydrogen storage alloys to react chemically with hydrogen under certain temperature and pressure conditions to generate metal hydrides, thereby achieving high-density hydrogen storage, and then releasing hydrogen by heating. The hydrogen absorption and desorption reaction formula can be expressed as

Magnesium-based hydrogen storage alloys are recognized as the most promising hydrogen storage materials due to their large hydrogen storage capacity and low cost. However, the heating temperature required for dehydrogenation is usually above 280°C, and the high-temperature gas generated needs to undergo a pre-cooling process before it can be passed into the anode to participate in the reaction. At the same time, the temperature of the air supplied to the cathode through the compressor is usually as high as hundreds of degrees. Therefore, the reactants of the anode and cathode of the fuel cell system for substations that uses metal hydride hydrogen storage are both high-temperature and high-pressure gases, which need to undergo a cooling process before passing into the anode and cathode to prevent local high temperatures on the membrane electrode and damage to the membrane electrode.

There are pressure limitations inside the fuel cell cooling circuit, among which the pressure bearing capacity of the fuel cell stack cooling chamber is particularly limited. If the water pump is connected to the inlet of the fuel cell stack cooling chamber, it is necessary to pay special attention to the cooling fluid pressure at the inlet. Bubbles and impurities need to be avoided in the cooling circuit to prevent local high temperature of the membrane electrode caused by uneven local heat transfer in the cooling chamber. The stack transfers heat to the cooling circuit through the bipolar plate. Since the bipolar plate also plays the role of collecting and conducting current, the coolant, as an object in direct contact with the bipolar plate, must maintain extremely low conductivity. After the fuel cell system is started, when the temperature of the cooling circuit rises, the coolant will expand due to heat. When designing the thermal management system, it is also necessary to consider how to accommodate the expansion of the coolant and maintain the stability of the cooling circuit pressure.

In order to achieve high-performance operation of fuel cells and prevent component damage, an additional thermal management system is necessary. For different types of fuel cells and their application scenarios, there are different cooling methods such as passive cooling, air cooling, liquid cooling and phase change material cooling. At present, for station power fuel cell systems that operate for a long time and at high power, liquid cooling is usually the best choice.

However, the thermal management system of fuel cells in the prior art has the following deficiencies:

In 2022, Lu Xing et al. proposed a hybrid vehicle model including a fuel cell thermal management system in the paper "Modeling and thermal management of proton exchange membrane fuel cell for fuel cell/battery hybrid automotive vehicle[J].International Journal of Hydrogen Energy,2022,47(3):1888-1900." and tested the performance of the thermal management system under an actual driving cycle. The structural diagram of the fuel cell stack cooling circuit is shown in Figure 1. The model uses PID control to adjust the cooling water flow, and then the performance of the thermal management system is tested under an actual driving cycle. Fuel cells are typical nonlinear time-varying strongly coupled dynamic systems. There are a large number of random disturbances during operation. It may be difficult to meet the dynamic performance requirements of the system using traditional PID control. In fact, the proposed thermal management system model was only tested in the low-speed stage of the CLTC-P operating condition, and it is impossible to prove the effectiveness of the thermal management system when the fuel cell is running at high power.

Bo Zhang et al. designed a thermal management system for an open cathode proton exchange membrane fuel cell in 2020. In "Design and implementation of model predictive control for an open-cathode fuel cell thermal management system[J].Renewable Energy, 2020, 154:1014-1024.", they proposed a new model predictive control (MPC) method as a control strategy for the blower in the cooling system. The constructed thermal management system is shown in Figure 2. The system uses air cooling, and the only controlled object is the cooling fan in the open cathode proton exchange membrane fuel cell system. There is no coupling problem of multiple heat sinks, and the scale of the cooling system is limited, which can only meet the cooling needs of small fuel cell systems.

Ye Yaoli et al. also proposed a high-power fuel cell dual water pump cooling system in Chinese patent CN115863694A, but the system did not take into account the pre-cooling of the anode supply gas, was not suitable for the substation fuel cell backup power system using the new alloy hydrogen storage technology, and its heat dissipation control capability was not strong enough.

The research on fuel cell thermal management conducted by domestic and foreign scholars mainly focuses on two directions, namely the design of the cooling system structure and the research on the radiator control strategy. At present, the new substation backup power architecture based on fuel cells is in the pilot promotion stage, and the research on the thermal management system of substation fuel cell backup power is relatively weak. According to the analysis of actual application scenarios, the design of the thermal management system of the station power supply with long-term high-power operation mainly has the following three key points:

(1) The system must have sufficient heat dissipation capacity to cope with the temperature control problem during long-term, high-power operation of the station power supply; it must also have the function of auxiliary heating of the fuel cell stack through the cooling circuit to deal with the problem of slow startup or even failure to start the fuel cell in a low-temperature environment, thereby broadening the application scenarios of the system.

(2) Secondly, the control loop of the thermal management system needs to be effectively integrated with the secondary system of the station power supply.

(3) Third, for the fuel cell backup power supply of substations using the new alloy hydrogen storage technology, it is necessary to consider the pre-cooling process of the reaction gas entering the anode, and it is necessary to further improve the heat dissipation capacity under the heat dissipation mode.

Therefore, there is an urgent need to design a thermal management system and control method for a substation fuel cell backup power supply, which can solve the heat dissipation problem when the fuel cell is used as a station power supply for a long time and the problem of rapid cold start in a low temperature environment.

Summary of the invention

1. Technical issues to be resolved

Based on the above defects, the present invention proposes a thermal management system for a substation fuel cell backup power supply and a control method thereof. The system will provide a thermal management solution for the substation fuel cell backup power supply adopting a new alloy hydrogen storage technology. The system has three operating modes: stack heating, stack heat dissipation and stack heat dissipation. It solves the heat dissipation problem of the fuel cell when it runs for a long time as a station power supply and the problem of rapid cold start in a low temperature environment.

(II) Technical solution

The present invention discloses a thermal management system for a fuel cell backup power supply in a substation, comprising a fuel cell stack, a filter, a main cooling circuit water pump, a first three-way valve, a second three-way valve, a third three-way valve, a fourth three-way valve, a PTC electric heater and a main cooling circuit radiator, wherein the outlet of the filter is connected to the inlet of a cooling chamber of the fuel cell stack, the outlet of the main cooling circuit water pump is connected to the inlet of the filter through a pipeline, the first three-way valve and the second three-way valve are two-inlet and one-outlet three-way valves, the third three-way valve and the fourth three-way valve are two-outlet and one-inlet three-way valves, and the coolant outlet of the main cooling circuit radiator is connected to the first inlet of the second three-way valve through a pipeline , the outlet of the second three-way valve is connected to the first inlet of the first three-way valve, the outlet of the first three-way valve is connected to the inlet of the main cooling circuit water pump, the PTC electric heater is arranged on the pipeline between the first outlet of the third three-way valve and the second inlet of the first three-way valve to form a second branch, the first outlet of the fourth three-way valve is connected to the second inlet of the second three-way valve through a pipeline to form a third branch, the cooling chamber outlet of the fuel cell stack is connected to the inlet of the third three-way valve, the second outlet of the third three-way valve is connected to the inlet of the fourth three-way valve, and the second outlet of the fourth three-way valve is connected to the inlet of the main cooling circuit radiator.

Preferably, the main cooling circuit radiator includes a heat-conducting metal plate, cooling fins and a fan group. The heat-conducting metal plate is made of copper, and a fine cavity is formed inside by processing. The cavity is pre-filled with phase change material. The cooling fins are made of aluminum alloy and are arranged above the heat-conducting metal plate. The fan group directly blows the cooling fins, and the number of fans in the fan group is not less than 4.

Preferably, it also includes a main cooling circuit expansion water tank and a deionizer in the first branch, the inlet of the main cooling circuit expansion water tank is connected to the outlet of the cooling chamber of the fuel cell stack through a pipe, the inlet of the deionizer is connected to the outlet of the main cooling circuit expansion water tank through a pipe, and the outlet of the deionizer is connected to the inlet of the main cooling circuit water pump through a pipe.

Preferably, it also includes an inlet pressure sensor, an inlet temperature sensor and an outlet temperature sensor, the inlet pressure sensor and the inlet temperature sensor are placed between the cooling chamber inlet of the fuel cell stack and the outlet of the filter, and the outlet temperature sensor is placed between the cooling chamber outlet of the fuel cell stack and the inlet of the main cooling circuit expansion water tank.

Preferably, a secondary cooling circuit is further included, wherein the secondary cooling circuit includes a cathode gas heat exchanger, an anode gas heat exchanger, a secondary cooling circuit water pump, a secondary cooling circuit expansion water tank and a secondary cooling circuit radiator, the outlet of the secondary cooling circuit water pump is connected to the coolant inlet of the cathode gas heat exchanger and the anode gas heat exchanger through a pipeline, the inlet of the secondary cooling circuit expansion water tank is connected to the coolant outlet of the cathode gas heat exchanger and the anode gas heat exchanger through a pipeline, the coolant outlet of the secondary cooling circuit radiator is connected to the inlet of the secondary cooling circuit cooling water pump through a pipeline, and the coolant inlet of the secondary cooling circuit radiator is connected to the outlet of the secondary cooling circuit expansion water tank through a pipeline.

Preferably, it also includes an RS485 bus, a first controller and a second controller, the first controller performs thermal management control of the main cooling circuit and each branch through the RS485 bus, and the second controller performs thermal management control of the auxiliary cooling circuit through the RS485 bus.

In another aspect, the present invention also designs a control method for a substation fuel cell backup power supply thermal management system, through which the substation fuel cell backup power supply thermal management system can control and realize three working modes: stack heating mode, stack heat dissipation mode, and stack auxiliary heating mode;

In the stack heating mode, the coolant does not flow through the main cooling circuit radiator and the second branch, but only through the third branch;

In the stack heat dissipation mode, the coolant flows only through the main cooling circuit radiator of the main cooling circuit, and does not pass through the second branch and the third branch; at this time, the control voltage of the main cooling circuit water pump and the fan gear position of the main cooling circuit radiator can be adjusted according to the temperature and power data of the fuel cell stack;

In the stack auxiliary heating mode, the coolant does not flow through the main cooling circuit radiator and the third branch, but only through the second branch where the PTC electric heater is located, and the PTC electric heater is started to heat the cooling circuit.

In addition, when the battery stack is in heat dissipation mode, the first controller can run the MARC optimal temperature adaptive control method based on FFRLS online identification and LSTM neural network. The method includes FFRLS online identification model modeling, optimal temperature predictor based on LSTM neural network, and MRAC model reference adaptive control method. See the following text for details.

(III) Beneficial effects

1. The present invention proposes a thermal management system for a fuel cell backup power supply for a substation, which will provide a thermal management solution for a fuel cell backup power supply for a substation using a new alloy hydrogen storage technology. The system includes a fuel cell stack, a filter, a main cooling circuit water pump, a three-way valve, a main cooling circuit radiator, a PTC electric heater, a cathode and anode gas heat exchangers, a secondary cooling circuit water pump, a secondary cooling circuit radiator, an RS485 bus and a controller. The control and communication module of the system will be combined with the secondary system of the substation to become an important part of the new backup power supply architecture of the substation. In order to cope with the thermal management problem of the fuel cell system of the substation during long-term and high-power operation, and to improve the safety and reliability of the fuel cell backup power supply, the system has the functions of fuel cell temperature control and rapid cold start. The system has three working modes of stack heat dissipation, stack heating, and stack auxiliary heating, which work in coordination with each other. While meeting the high-temperature control requirements of the fuel cell, the requirements for rapid start of the fuel cell in a low-temperature environment are taken into account. By setting a cooling circuit branch and a PTC electric heater, a stack heating mode and a stack auxiliary heating mode are added, and rapid start in the full temperature range is achieved, effectively broadening the application scenarios of the thermal management system.

2. In order to solve the problem of pre-cooling the reaction gas of the fuel cell system using the new alloy hydrogen storage technology, the present invention also sets up an independent auxiliary cooling circuit in hardware improvement. The circuit is not coupled with the main cooling circuit and is used for pre-cooling the high-temperature reaction gas of the anode and cathode to prevent the high-temperature gas from directly entering the anode and cathode and causing the life of the system components to be shortened and damaged, and reduce the control complexity of the system.

3. Because in the stack heat dissipation mode, the controller needs to adjust the control voltage of the main cooling circuit water pump and the fan gear of the main cooling circuit radiator according to the temperature and power data of the fuel cell stack, so as to perform temperature control of heat dissipation and cooling through multi-variable adjustment, the present invention designs an optimal temperature model reference adaptive control strategy, which is a PEMFC optimal temperature adaptive control method based on FFRLS online identification and LSTM neural network, and realizes precise control of the fuel cell stack temperature in the heat dissipation mode.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments are briefly introduced below:

FIG1 is a structural diagram of a PEMFC cooling circuit for a vehicle in the prior art;

FIG2 is a schematic diagram of an open cathode proton exchange membrane fuel cell cooling system in the prior art;

FIG3 is a schematic diagram of the overall architecture of a thermal management system for a fuel cell backup power supply for a substation proposed by the present invention;

FIG4 is an operation flow chart of the thermal management system of the fuel cell backup power supply for a substation according to the present invention;

FIG5 is a schematic diagram of the optimal temperature adaptive control method for PEMFC based on FFRLS online identification and LSTM neural network in the present invention.

The markings in the accompanying drawings are:

010-fuel cell stack, 011-cathode gas heat exchanger, 012-anode gas heat exchanger, 020-inlet pressure sensor, 021-inlet temperature sensor, 022-outlet temperature sensor, 030-filter, 041-main cooling circuit water pump, 042-auxiliary cooling circuit water pump, 051-first three-way valve, 052-second three-way valve, 053-third three-way valve, 054-fourth three-way valve, 061-first controller, 062-second controller, 070-PTC electric heater, 080-main cooling circuit radiator, 090-deionizer, 101-main cooling circuit expansion water tank, 102-auxiliary cooling circuit expansion water tank, 110-auxiliary cooling circuit radiator, 120-RS485 bus.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

To solve the heat dissipation problem when the fuel cell is used as the power source of the substation for a long time and the problem of rapid cold start in a low temperature environment. As shown in Figure 3, the present invention provides a substation fuel cell backup power supply thermal management system, including a fuel cell stack 010, a filter 030, a main cooling circuit water pump 041, a first three-way valve 051, a second three-way valve 052, a third three-way valve 053, a fourth three-way valve 054, a PTC electric heater 070 and a main cooling circuit radiator 080, the outlet of the filter 030 is connected to the cooling chamber inlet of the fuel cell stack 010, the outlet of the main cooling circuit water pump 041 is connected to the inlet of the filter 030 through a pipeline, the four three-way valves 051-054 are used to connect each branch with the main cooling circuit, and the first three-way valve 051 and the second three-way valve 052 are two-in and one-out three-way valves, the third three-way valve 053 and the fourth three-way valve 054 are two-out and one-in three-way valves, and the main cooling circuit radiator 080 is connected to the main cooling circuit radiator 080. The coolant outlet of the cooling circuit radiator 080 is connected to the first inlet of the second three-way valve 052 through a pipeline, the outlet of the second three-way valve 052 is connected to the first inlet of the first three-way valve 051, the outlet of the first three-way valve 051 is connected to the inlet of the main cooling circuit water pump 041, the PTC electric heater 070 is arranged on the pipeline between the first outlet of the third three-way valve 053 and the second inlet of the first three-way valve 051, the first outlet of the fourth three-way valve 054 is connected to the second inlet of the second three-way valve 052 through a pipeline, the cooling chamber outlet of the fuel cell stack 010 is connected to the inlet of the third three-way valve 053, the second outlet of the third three-way valve 053 is connected to the inlet of the fourth three-way valve 054, and the second outlet of the fourth three-way valve 054 is connected to the inlet of the main cooling circuit radiator 080. Therefore, it can be known that the coolant outlet of the main cooling circuit radiator 080 is connected to the inlet of the main cooling circuit water pump 041 through the pipeline and three-way valves 051 and 052, and the cooling cavity outlet of the fuel cell stack 010 is connected to the main cooling circuit radiator 080 through the pipeline and three-way valves 053 and 054. The fuel cell stack, filter, main cooling circuit water pump, three-way valve and main cooling circuit radiator together constitute the main cooling circuit.

The substation fuel cell backup power supply thermal management system also includes a main cooling circuit expansion water tank 101 and a deionizer 090 in the first branch. The inlet of the main cooling circuit expansion water tank 101 is connected to the cooling chamber outlet of the fuel cell stack 010 through a pipeline, the inlet of the deionizer 090 is connected to the outlet of the main cooling circuit expansion water tank 101 through a pipeline, and the deionizer outlet 090 is connected to the inlet of the main cooling circuit water pump 041 through a pipeline. The main cooling circuit expansion water tank 101 and the deionizer 090 together constitute the first branch.

In addition, the second branch is composed of a PTC electric heater 070 and two upper and lower three-way valves 051 and 053. The PTC electric heater 070 can heat the coolant in the circuit through the heating chamber. The heating chamber inlet of the PTC electric heater 070 is connected to the cooling chamber outlet of the fuel cell stack 010 through the third three-way valve 053 and a pipeline. The heating chamber outlet of the PTC electric heater 070 is connected to the inlet of the main cooling circuit water pump 041 through the first three-way valve 051 and a pipeline.

The third branch is arranged between the second three-way valve 052 and the fourth three-way valve 054. The function of the third branch is to adjust the coolant flow rate. The branch is connected in parallel with the main cooling circuit radiator through the three-way valves 052 and 054. The inlet of the third branch is connected to the cooling chamber outlet of the fuel cell stack 010 through the pipeline and the three-way valves 053 and 054. The outlet of the third branch is connected to the inlet of the main circuit cooling water pump 041 through the pipeline and the three-way valves 051 and 052.

The main cooling circuit radiator 080 includes a heat-conducting metal plate, heat-dissipating fins and a fan group. The heat-conducting metal plate is made of copper, and a fine cavity is formed inside through processing, and the cavity is pre-filled with phase change material. The phase change material vaporizes when heated, and quickly condenses when cooled, and flows back to the bottom of the heat-conducting metal plate along the internal capillary. This process is repeated to quickly cool the coolant. The heat-dissipating fins are made of aluminum alloy and are arranged above the heat-conducting metal plate to increase the contact area between the radiator and the air and enhance heat convection. The fan group blows directly to the heat-dissipating fins, and the fan speed has several gears that can be selected according to the heat dissipation needs. The number of fans in the fan group is not less than 4 to ensure the air intake.

The main cooling circuit is also provided with an inlet pressure sensor 020 and an inlet temperature sensor 021, which are placed between the cooling chamber inlet of the fuel cell stack 010 and the outlet of the filter 030. In addition, an outlet temperature sensor 022 is provided, which is placed between the cooling chamber outlet of the fuel cell stack 010 and the inlet of the main cooling circuit expansion tank 101 on the first branch.

In addition to the main cooling circuit, a secondary cooling circuit independent of the main cooling circuit is also designed in the thermal management system of the fuel cell backup power supply of the substation. The secondary cooling circuit includes a cathode gas heat exchanger 011, an anode gas heat exchanger 012, a secondary cooling circuit water pump 042, a secondary cooling circuit expansion water tank 102 and a secondary cooling circuit radiator 110. The outlet of the secondary cooling circuit water pump 042 is connected to the coolant inlet of the cathode gas heat exchanger 011 and the anode gas heat exchanger 012 through a pipeline, and the inlet of the secondary cooling circuit expansion water tank 102 is connected to the coolant outlet of the cathode gas heat exchanger 011 and the anode gas heat exchanger 012 through a pipeline. The secondary cooling circuit radiator 110 includes structures such as a cold plate and a fan group. The coolant outlet of the secondary cooling circuit radiator 110 is connected to the inlet of the secondary circuit cooling water pump 042 through a pipeline, and the coolant inlet of the secondary cooling circuit radiator 110 is connected to the outlet of the secondary cooling circuit expansion water tank 102 through a pipeline. Therefore, the cathode gas heat exchanger, the anode gas heat exchanger, the auxiliary cooling circuit water pump, the auxiliary cooling circuit expansion water tank, and the auxiliary cooling circuit radiator together constitute an auxiliary cooling circuit circulation independent of the main cooling circuit, and the auxiliary cooling circuit has no direct connection with the main cooling circuit.

In order to independently control the main cooling circuit and the auxiliary cooling circuit, the system also includes communication modules such as RS485 bus 120, first controller 061 and second controller 062. RS485 bus 120 collects signals sent by sensors inside the fuel cell stack 110, cathode gas heat exchanger 011 and anode gas heat exchanger 012, as well as inlet pressure sensor 020, inlet temperature sensor 021 and outlet temperature sensor 022. The first controller 061 and the second controller 062 read the signals on the RS485 bus, analyze and process the received sensor data, and control the main circuit cooling water pump, three-way valve, main cooling circuit radiator, auxiliary cooling circuit water pump, auxiliary cooling circuit and other heat dissipation structures and PTC electric heaters according to the pre-burned control program. At the same time, the RS485 bus and controller will communicate with the industrial computer in the substation in real time to complete tasks such as data storage and processing, visualization of system operation information, and real-time adjustment of control strategies. The above control and communication modules will constitute part of the substation secondary system.

In the communication module, the detection signals of the fuel cell stack 010, the inlet pressure sensor 020, the inlet temperature sensor 021, and the outlet temperature sensor 022 in the main cooling circuit are connected to the first controller 061 through the RS485 bus 120. The first controller 061 can be a DSP processor, and the control end of the first controller 061 is connected to the main cooling circuit water pump 041, the four three-way valves 051-054, the PTC electric heater 070, and the main cooling circuit radiator 080 for communication, so as to control the temperature of the main cooling circuit. The control method implemented by the first controller is shown in FIG4. In addition, the detection signals of the cathode gas heat exchanger 011 and the anode gas heat exchanger 012 in the auxiliary cooling circuit are connected to the second controller 062 through the RS485 bus 120. The control port of the second controller 062, which can be a DSP processor, is connected to the control end of the auxiliary cooling circuit water pump 042 and the auxiliary cooling circuit radiator 110 to control the temperature of the auxiliary cooling circuit.

After describing the various components in the system and the connection methods between the components, it can be seen that the fuel cell thermal management system for substations is generally composed of a main cooling circuit, a secondary cooling circuit, a first branch, a second branch, a third branch and a control and communication module. The functions of each module are briefly described below to facilitate understanding of the advantages of the system.

(1) Main cooling circuit

The fuel cell stack, filter, main cooling circuit water pump, four three-way valves and main cooling circuit radiator together constitute the main cooling circuit to realize the heat dissipation function of the stack. During the operation of the system, the flow rate of coolant flowing through the stack cooling chamber is adjusted by adjusting the speed of the main cooling circuit water pump 041. In the actual application scenario of the present invention, a two-dimensional mapping table of the speed can be established according to the stack output power and the stack temperature signal, and the control voltage of the water pump speed gear can be determined in real time according to the signal measured by the sensor. The function of the filter 030 is to remove solid particles in the coolant to prevent uneven heat transfer in the cooling chamber.

(2) First branch

The expansion water tank and deionizer of the main cooling circuit together constitute the first branch, which can always operate and has no temperature regulation function. The expansion water tank 101 can accommodate the volume expansion of the coolant due to the temperature rise and maintain the pressure of the cooling circuit stable. At the same time, the expansion water tank also has the function of discharging bubbles in the cooling circuit. The deionizer 090 removes the conductive ions in the coolant by resin adsorption to reduce the conductivity of the coolant.

(3) Second branch

The main component of the second branch is the PTC electric heater, which is mainly used to achieve rapid start-up of the battery stack and auxiliary heating of the battery stack. The PTC electric heater 070 can heat the coolant in the loop through the heating chamber, so that the temperature of the battery stack quickly rises to the ideal operating temperature range, or prevents the temperature of the battery stack from falling below the lower limit of the operating temperature.

(4) The third branch

When the system is in the stack heating mode, the fourth three-way valve and the second three-way valve can be adjusted to allow the coolant to bypass the main cooling circuit and flow only through the third branch. The stack temperature can be rapidly increased by adjusting the coolant flow in the third branch.

(5) Auxiliary cooling circuit

The cathode gas heat exchanger, the anode gas heat exchanger, the auxiliary cooling circuit water pump, the auxiliary cooling circuit expansion water tank, and the auxiliary cooling circuit radiator together constitute an auxiliary cooling circuit cycle independent of the main cooling circuit. As can be seen from the background technology, the reactant of the anode of the fuel cell is the high-temperature hydrogen released after heating the hydrogen storage alloy above 280°C, and the reactant of the cathode is the high-temperature and high-pressure air processed by the compressor. Therefore, before the reactant is introduced into the gas diffusion layer of the fuel cell, it needs to be pre-treated by the auxiliary cooling circuit to prevent local high temperature from causing damage to system components. When the system output power changes, the supply gas temperature is controlled within a reasonable range by adjusting the speed of the auxiliary cooling circuit water pump 042. The auxiliary cooling circuit expansion water tank 102 can accommodate the volume expansion of the coolant due to the temperature rise, and maintain the cooling circuit pressure stable. The auxiliary cooling circuit radiator 110 includes structures such as a cold plate and a fan group to improve the heat dissipation efficiency. In addition, the auxiliary cooling circuit is always maintained during the operation of the fuel cell system, regardless of whether the main cooling circuit enters the stack heat dissipation mode.

(6) Control and communication module

The control and communication module of the system will be directly combined with the secondary system of the substation, including structures such as RS485 bus and controller. RS485 bus 120 collects temperature, pressure, power and other signals measured by all sensors in the system. The first controller 061 and the second controller 062 read the signal on the RS485 bus 120, determine the working mode of the thermal management system according to the system status information sent by each sensor, and then adjust the speed gear of the main cooling circuit water pump 041 and the auxiliary cooling circuit water pump 042 according to the specified control strategy, adjust the fan gear of the main cooling circuit radiator 080 and the auxiliary cooling circuit radiator 110, adjust the power gear of the PTC electric heater 070, and adjust the opening of the four three-way valves 051, 052, 053, and 054 to adjust the proportion of coolant flowing through the main cooling circuit and each branch. At the same time, the RS485 bus and controller will communicate with the industrial computer in the substation in real time to complete tasks such as data storage and processing, visualization of system operation information, and real-time adjustment of control strategies. It should be pointed out that, because the temperature control of the second controller is relatively simple (it has less hardware and variables and strong controllability), the present invention mainly studies the control strategy of the first controller.

The thermal management system of the fuel cell backup power supply of the substation can realize three working modes of stack heat dissipation, stack heating and stack auxiliary heating through the control of the first controller 061, and can switch different working modes according to the specific working scenarios of the fuel cell to maintain the stack temperature within the ideal range. The specific control method can be seen in Figure 4.

Among them, the switch states in the three working modes of stack heat dissipation, stack heating, and stack auxiliary heating are introduced as follows:

(1) Stack heating mode

When the stack is started, the working mode of the fuel cell thermal management system for the substation is stack heating. The controller 061 adjusts the opening of the four three-way valves 051, 052, 053, and 054 so that the coolant does not flow through the main cooling circuit radiator 080 and the second branch (the PTC electric heater 070 is not started at this time), and only flows through the third branch. The three-way valve is used to adjust the coolant flow rate so that the stack heats up by itself. This mode uses the heat generated by the electrochemical reaction of the fuel cell stack 010 to quickly heat up the stack, thereby achieving rapid start-up. When the coolant temperature at the outlet of the cooling chamber of the fuel cell stack 010 is greater than 60°C, the stack heating mode is switched to the stack heat dissipation mode. In this process, the three-way valve opening can be adjusted without starting and stopping the main cooling circuit water pump.

(2) Stack cooling mode

When the temperature of the coolant at the outlet of the cooling chamber of the fuel cell stack 010 reaches above 60°C and the fuel cell stack 010 continues to heat up, the stack heat dissipation mode is started, and the first controller 061 adjusts the opening of the four three-way valves 051, 052, 053, and 054 so that the coolant only flows through the main cooling circuit. The controller adjusts the control voltage of the main cooling circuit water pump 041 and the fan gear position of the main cooling circuit radiator 080 according to the temperature and power data of the fuel cell stack 010, and realizes precise control of the temperature of the fuel cell stack 010 through an optimal temperature model reference adaptive control strategy. The schematic diagram of the adaptive control method used is shown in Figure 5, and the overall brief description is shown later.

(3) Stack auxiliary heating mode

When the fuel cell is in a low-temperature environment, the heat generated by the electrochemical reaction of the fuel cell stack 010 itself cannot meet the needs of heating the stack, and it may even fail to start. At this time, the working mode of the fuel cell thermal management system for the substation is switched to auxiliary heating of the stack. The controller 061 adjusts the opening of the three-way valves 051, 052, 053, and 054 so that the coolant does not flow through the main cooling circuit radiator 080 and the third branch, but only through the second branch where the PTC electric heater 070 is located, and starts the PTC electric heater 070. The PTC electric heater 070 heats the cooling circuit, and the coolant sends heat to the fuel cell stack 010 through circulation, so that the fuel cell stack 010 quickly reaches the ideal temperature range. When the coolant temperature at the outlet of the cooling chamber of the fuel cell stack 010 reaches 60°C, it switches to other working modes according to the situation.

As shown in FIG. 4 , the typical control method based on the above three working mode switching in the present invention includes the following steps:

Step 1: During the startup of the fuel cell system, the stack heating mode or the stack auxiliary heating mode is selected according to whether the ambient temperature is greater than 0°C, that is, whether the PTC electric heater needs to be started. If yes, the stack heating mode is entered, otherwise, the stack auxiliary heating mode is entered;

Step 2: When the stack temperature is higher than 60°C, it is considered that the stack has reached a high operating efficiency and the PTC electric heater is turned off. At this time, if the stack's own heat generation can maintain the operating temperature above 60°C, the thermal management system enters the stack heat dissipation mode; if the stack temperature cannot be maintained above 60°C, the stack auxiliary heating mode is restarted.

It can be seen that through the above steps 1-2, the advantages of the three working modes of stack heat dissipation, stack heating, and stack auxiliary heating can be effectively utilized for thermal management, thereby solving the heat dissipation problem when the fuel cell is used as the station power supply of the substation for a long time and the problem of rapid cold start in a low temperature environment.

Because the system complexity is reduced after the separation of the main and auxiliary cooling circuits, the controllability in the heat dissipation mode of the fuel cell stack is enhanced. At this time, in order to make the fuel cell stack work in the heat dissipation mode for as long as possible, the present invention further designs a set of high-precision temperature control methods for heat dissipation of the fuel cell stack. FIG5 is a schematic diagram of the optimal temperature adaptive control method of the fuel cell MRAC based on FFRLS online identification and LSTM neural network. The method includes three designs: FFRLS online identification model modeling, optimal temperature predictor based on LSTM neural network, and MRAC model reference adaptive control method.

(A) FFRLS online identification model building

The characteristics highly related to the stack temperature, such as the intake parameters, cooling water inlet and outlet temperatures, and the control voltages of the fan and water pump, are set as [u ₁ ,u ₂ ,…, _un ], respectively. Considering the slow dynamic response of the fuel cell, the system hysteresis d is introduced to establish a dynamic prediction model for the fuel cell temperature:

T(k)＝f{u ₁ (kd),u ₂ (kd),…, _un (kd)} (2)

Where k represents the discrete sampling time of the system, T(k) and _un (kd) correspond to the stack operating temperature at time k and the model input characteristics at time (kd), respectively.

Formula (2) can be expressed as:

Where y(k) represents the system output, represents the model input, θ is the parameter to be identified, and v(k) represents the identification error.

θ＝[θ ₁ ,θ ₂ ,…,θ _m ] (5)

The identified value of the system output y(k) is expressed as

The identification error can be expressed as

The forgetting factor μ is introduced on the basis of the recursive least squares method (RLS), namely the forgetting factor-based recursive least squares method (FFRLS), and the parameter identification is completed by iterative formula (8).

Among them, the covariance matrix P(k) represents the difference between the parameter identification value and the actual value, the gain matrix K(k) represents the degree of correction of one iteration, and I is the unit matrix.

The optimization objective function J of the FFRLS algorithm is:

The unknown parameters in the fuel cell dynamic model are fitted by the forgetting factor recursive least squares algorithm (FFRLS), and the model parameters are updated in real time when the system state changes. The functional relationship between parameters such as overoxygen ratio, duty cycle, coolant temperature and the stack temperature is quickly identified, thereby reflecting the nonlinear time-varying characteristics of the fuel cell thermal management system through a mathematical model and realizing real-time prediction of the system temperature _Tp .

(B) Optimal temperature predictor based on LSTM neural network

After establishing a fuel cell dynamic model based on the FFRLS online identification algorithm, in order to achieve optimal temperature control, it is also necessary to predict the optimal operating temperature _Tr of the system in real time according to the current state of the system as the temperature control target. Under constant current, changes in the stack temperature will cause changes in membrane hydration and catalyst activity, thereby affecting the output voltage. When the output voltage is maximum, it corresponds to the maximum power point of the fuel cell, and the stack temperature at this time is defined as the optimal temperature. The optimal temperature of the stack operation is affected by environmental conditions and load conditions. Through the powerful nonlinear processing and time series prediction capabilities of the long short-term memory neural network LSTM, the optimal temperature curve of the fuel cell can be predicted.

Define the fuel cell state quantity input at time t as x _t , the output prediction quantity as h _t , and the long short-term memory neural network LSTM determines the extent to which the prediction information h _{t-1 at time t-1} enters the memory state C _t of the neuron at time t through the forget gate f _t .

_ft = σ( _Wf ·[ht _-1 , _xt ] + _Wf ) (10)

Function _Wf and _Wf represent the weight matrix and bias term of the forget gate, respectively.

The input gate determines to what extent the input xt at time _t is retained in _Ct , where the tangent hyperbolic function

_it =σ( _Wi ·[ _ht-1 , _xt ]+ _bi ) (11)

Multiply f _t by the memory state C _t-1 of the previous moment to determine the memory that needs to be forgotten in this iteration, and update the memory state C _t at moment t in combination with the result of the output layer.

The output gate determines to what extent C _t affects the output h _t at time t. C _t is processed by the tanh function and multiplied by the output gate o _t to finally output the predicted value h _t at time t.

o _t =σ(W _o ·[h _t-1 ,x _t ]+b _o ) (14)

h _t = o _t ·tanh(C _t ) (15)

The predicted value h _t is taken as the optimal operating temperature _Tr at time t. In the above formula, _Wi , _Wo and _WC respectively represent the weight matrices of h _t–1 in the input gate, output gate and feature extraction process; _bi , b _o and b _C respectively represent the bias terms in the input gate, output gate and feature extraction process.

③MRAC control method

A large number of random disturbances will be generated during the operation of fuel cells, such as fluctuations in load, flow rate, and ambient temperature and humidity. Aiming at the thermal management and temperature control problems of fuel cells under variable load and strong disturbance, the present invention adopts the model reference adaptive control method (MRAC) to control the temperature of the fuel cell stack in order to achieve optimal temperature control and ensure the smooth and efficient operation of the system.

First, a dynamic equation characterizing the temperature characteristics of the fuel cell stack is established.

Among them, T and T _flow represent the stack temperature and cooling water inlet temperature respectively, u _fan and u _pump represent the duty cycle of the fan and the water pump respectively, i, λ, and _Tamb represent the stack load, the excess oxygen ratio and the ambient temperature respectively. The dynamic equation is locally linearized by linear fitting functions f, g, and v near the optimal operating temperature _Tr to obtain the state space model of the fuel cell cooling system. A _p , B _p , and V _p in the model are all unknown parameters.

Based on the state space model of formula (17), the controlled object and the reference model are described as follows:

The ideal control law u is described by using unknown parameters K _x and K _r as

u＝-K _x Δr+K _r Δx _p (20)

Assume existence To make the system temperature follow the reference model output, we have

Define the state deviation e between the reference model and the controlled object and the system loss function J

e＝Δx _m -Δx _p (24)

Then the parameters of the adaptive law are adjusted based on the MIT gradient descent method or Lyapunov's second method.

The optimal temperature trajectory obtained by the above LSTM-based optimal temperature predictor is subtracted from the stack temperature curve predicted by the FFRLS online identification model to obtain the input control sequence of the fuel cell thermal management system, which is input into the MARC controller after rolling optimization and input constraint processing. Under the MRAC framework, the self-optimization and self-tuning of the adaptive controller parameters are realized based on the MIT gradient descent method or Lyapunov's second method, so that the stack temperature can quickly and accurately track the optimal temperature reference trajectory, while minimizing the impact of random disturbances in the system.

In summary, compared with the prior art, the characteristics and innovations of the present invention are:

1. The system proposed in the present invention will provide a thermal management solution for the backup power supply of fuel cells in substations using the new alloy hydrogen storage technology, address the thermal management issues during the long-term, high-power operation of the fuel cell system in the substation, and keep the fuel cell system at the optimal reaction temperature, improve the overall operating efficiency of the system, and extend the service life of each component. In addition, the thermal management system adds a stack heating mode and a stack auxiliary heating mode that can cooperate with the stack heat dissipation mode by setting a cooling circuit branch and a PTC electric heater, thereby achieving rapid startup of the fuel cell in the full temperature range and effectively broadening the application scenarios of the thermal management system.

2. The present invention is a thermal management system for a fuel cell backup power supply for a substation that uses a new alloy hydrogen storage technology. Both the cathode and anode electrodes are fed with high-temperature reaction gases. Therefore, the present invention simultaneously sets up a cathode gas cooling circuit and an anode gas cooling circuit, and separates the gas cooling circuit from the main cooling circuit, completing the decoupling of the main and auxiliary cooling circuits and reducing the control complexity of the system. In addition, after the system control complexity is reduced, the controllability of the heat dissipation mode is enhanced. Therefore, the present invention is also based on the PEMFC optimal temperature adaptive control method of FFRLS online identification and LSTM neural network, which further realizes the precise control of the fuel cell stack temperature under the heat dissipation mode.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The utility model provides a fuel cell standby power thermal management system of transformer substation, its characterized in that includes fuel cell stack, filter, main cooling circuit water pump, first three-way valve, second three-way valve, third three-way valve, fourth three-way valve, PTC electric heater and main cooling circuit radiator, the export of filter is connected with the cooling chamber inlet of fuel cell stack, the export of main cooling circuit water pump is through the pipeline with the entry linkage of filter, first three-way valve and second three-way valve are two three-way valve that go into first, third three-way valve and fourth three-way valve are two three-way valve that go into first three-way valve, the coolant outlet of main cooling circuit radiator is through the pipeline with the first entry linkage of second three-way valve, the export of second three-way valve is connected with the first entry of first three-way valve, the export of first three-way valve is connected with the entry linkage of main cooling circuit water pump, PTC electric heater sets up on the pipeline between the first export of third three-way valve and the second entry of first three-way valve to constitute the second branch road, the third three-way valve is connected with the third three-way valve, the third three-way valve is connected with the export of third three-way valve.

2. The thermal management system of a backup power supply of a fuel cell in a transformer substation according to claim 1, wherein the main cooling loop radiator comprises a heat conducting metal plate, heat radiating fins and a fan group, the heat conducting metal plate is made of copper, a fine cavity is formed in the heat conducting metal plate through processing, phase change materials are pre-filled in the cavity, the heat radiating fins are made of aluminum alloy and are arranged above the heat conducting metal plate, the fan group blows the heat radiating fins, and the number of fans in the fan group is not less than 4.

3. The thermal management system of a backup power source for a fuel cell in a power substation of claim 1, further comprising a primary cooling loop expansion tank in a first leg, an inlet of the primary cooling loop expansion tank being connected to a cooling cavity outlet of the fuel cell stack by a conduit, an inlet of the deionizer being connected to an outlet of the primary cooling loop expansion tank by a conduit, an outlet of the deionizer being connected to an inlet of a primary cooling loop water pump by a conduit.

4. A substation fuel cell backup power thermal management system as claimed in claim 3, further comprising an inlet pressure sensor, an inlet temperature sensor, and an outlet temperature sensor, the inlet pressure sensor and the inlet temperature sensor being disposed between the cooling cavity inlet of the fuel cell stack and the outlet of the filter, the outlet temperature sensor being disposed between the cooling cavity outlet of the fuel cell stack and the inlet of the main cooling circuit expansion tank.

5. The thermal management system of a backup power source for a fuel cell in a power substation of claim 4, further comprising a secondary cooling loop, wherein the secondary cooling loop comprises a cathode gas heat exchanger, an anode gas heat exchanger, a secondary cooling loop water pump, a secondary cooling loop expansion tank and a secondary cooling loop radiator, wherein an outlet of the secondary cooling loop water pump is connected with cooling liquid inlets of the cathode gas heat exchanger and the anode gas heat exchanger through a pipeline, an inlet of the secondary cooling loop expansion tank is connected with cooling liquid outlets of the cathode gas heat exchanger and the anode gas heat exchanger through a pipeline, a cooling liquid outlet of the secondary cooling loop radiator is connected with an inlet of the secondary cooling loop cooling water pump through a pipeline, and a cooling liquid inlet of the secondary cooling loop radiator is connected with an outlet of the secondary cooling loop expansion tank through a pipeline.

6. The thermal management system of a backup power source for a fuel cell in a transformer substation of claim 5, further comprising an RS485 bus, a first controller for performing thermal management control of the primary cooling circuit and each of the branches via the RS485 bus, and a second controller for performing thermal management control of the secondary cooling circuit via the RS485 bus.

7. A control method of a thermal management system for a fuel cell backup power supply of a transformer substation according to any one of claims 1 to 6, wherein the thermal management system for a fuel cell backup power supply of a transformer substation can control three operation modes including a stack heating mode, a stack heat dissipation mode and a stack auxiliary heat mode;

In the pile temperature rising mode, the cooling liquid does not flow through the radiator of the main cooling loop and the second branch, and only passes through the third branch;

In the pile heat dissipation mode, the cooling liquid only flows through the main cooling loop radiator of the main cooling loop and does not flow through the second branch and the third branch; at the moment, the control voltage of the main cooling loop water pump and the fan gear of the main cooling loop radiator can be adjusted according to the temperature and power data of the fuel cell stack;

Under the auxiliary electric pile heat mode, the cooling liquid does not flow through the radiator of the main cooling loop and the third branch, only passes through the second branch where the PTC electric heater is located, and starts the PTC electric heater to heat the cooling loop.

8. The method for controlling a thermal management system for a backup power source of a fuel cell of a substation according to claim 7, further comprising the steps of:

Step 1: during the starting of the fuel cell system, selecting a pile heating mode or a pile auxiliary heating mode according to whether the ambient temperature is higher than 0 ℃, namely determining whether the PTC electric heater needs to be started, if so, entering the pile heating mode, and if not, entering the pile auxiliary heating mode;

Step 2: when the temperature of the electric pile is higher than 60 ℃, the electric pile is considered to reach higher operation efficiency, the PTC electric heater is turned off, and if the self-generated energy of the electric pile can maintain the operation temperature above 60 ℃, a heat dissipation mode of the electric pile is entered; if the stack temperature cannot be maintained above 60 ℃, restarting the stack auxiliary heating mode.

9. The control method of the substation fuel cell backup power supply thermal management system according to claim 8, wherein the method comprises FFRLS online identification model modeling, an optimal temperature predictor based on an LSTM neural network, and an MRAC model reference adaptive control method, wherein the MARC optimal temperature adaptive control method based on FFRLS online identification and an LSTM neural network is operated in the pile heat dissipation mode;

the FFRLS online recognition model modeling includes:

The characteristics of the air inlet parameter, the cooling water inlet and outlet temperature, the control voltage of the fan and the water pump and the height of the electric pile temperature are respectively set as [ u ₁,u₂,…,u_n ], the characteristic of slow dynamic response of the fuel cell is considered, the system delay d is introduced, and a dynamic prediction model of the fuel cell temperature is established:

T(k)＝f{u₁(k-d),u₂(k-d),…,u_n(k-d)} (2)

Wherein k represents discrete sampling time of the system, and T (k) and u _n (k-d) respectively correspond to the operating temperature of the pile at the moment k and the model input characteristics at the moment (k-d);

The formula (2) is expressed as:

Where y (k) represents the system output, Representing the input quantity of the model, wherein theta is a parameter to be identified, and v (k) represents an identification error;

θ＝[θ₁,θ₂,…,θ_m] (5)

the identification value of the system output y (k) is expressed as

The identification error can be expressed as

Introducing a forgetting factor mu on the basis of a recursive least square method, namely, completing parameter identification through an iterative formula (8) based on the recursive least square method FFRLS of the forgetting factor;

the covariance matrix P (K) represents the difference between the parameter identification value and the actual value, the gain matrix K (K) represents the correction degree of one iteration, and I is a unit matrix;

the optimization objective function J of FFRLS algorithm is:

Fitting unknown parameters in a fuel cell dynamic model through a forgetting factor recursive least square algorithm FFRLS, updating model parameters in real time when the system state is changed, and rapidly identifying the functional relation of the peroxy ratio, the duty ratio, the cooling liquid temperature and the pile temperature, so that the nonlinear time-varying characteristics of the fuel cell thermal management system are reflected through a mathematical model, and the real-time prediction of the system temperature T _p is realized;

the optimal temperature predictor based on the LSTM neural network comprises:

Defining the state quantity of the fuel cell input at the time t as x _t, outputting the predicted quantity as h _t, and determining the degree to which the predicted information h _t-1 at the time t-1 enters the memory state C _t of the neuron at the time t by the long-short-term memory neural network LSTM through a forgetting gate f _t;

f_t＝σ(W_f·[h_t-1,x_t]+W_f) (10)

Function in W _f and W _f represent the weight matrix and bias term of the forgetting gate, respectively;

The input gate determines how much the input x _t at time t remains in C _t, where tangent hyperbolic function

i_t＝σ(W_i·[h_t-1,x_t]+b_i) (11)

Multiplying f _t by the memory state C _t-1 at the previous moment, determining that the memory needed to be forgotten in the iteration is needed, and updating the memory state C _t at the moment t by combining the result of the output layer;

Determining the output quantity h _t of the C _t at the time t through the output gate, processing C _t by a tanh function, multiplying the processed C _t by o _t of the output gate, and finally outputting the predicted quantity h _t at the time t;

o_t＝σ(W_o·[h_t-1,x_t]+b_o) (14)

h_t＝o_t·tanh(C_t) (15)

Taking the value of the predicted value h _t as the optimal operation temperature T _r at the time T, wherein W _i、W_o and W _C in the above formula respectively represent an input gate, an output gate and a weight matrix of h _t–1 in the characteristic extraction process; b _i、b_o and b _C represent input gates, output gates, and bias terms in the feature extraction process, respectively;

The MARC optimal temperature self-adaptive control method comprises the following steps:

and (3) performing difference between the optimal temperature track obtained by the optimal temperature predictor based on the LSTM and a stack temperature curve predicted by the FFRLS on-line identification model to obtain an input control sequence of the fuel cell thermal management system, inputting the input control sequence into the MARC model reference adaptive controller after rolling optimization and input constraint processing, and under an MRAC framework, performing self-optimization and self-tuning of parameters of the adaptive controller based on an MIT gradient descent method or a Lyapunov second method to enable the temperature of the stack to quickly and accurately track the optimal temperature reference track.

10. The method for controlling a thermal management system of a backup power supply of a fuel cell of a transformer substation according to claim 9, wherein the MARC optimal temperature adaptive control method further comprises: establishing a dynamic equation for representing the temperature characteristics of the galvanic pile;

Wherein T, T _flow respectively represents the stack temperature and the cooling water inlet temperature, u _fan、u_pump respectively represents the duty ratio of a fan and a water pump, i, lambda and T _amb respectively represent the stack load, the peroxy ratio and the ambient temperature, a dynamic equation is locally linearized by linear fitting functions f, g and v respectively near the optimal operation temperature T _r, a state space model of the fuel cell cooling system is obtained, and A _p、B_p、V_p in the model is unknown parameter;

equations for the controlled object and the reference model are described based on the linearized state space model of equation (17).