Fuel cell hybrid power system and control method

Abstract

A fuel cell hybrid power system, comprising a fuel cell (1), a first DC / DC converter (2), a power battery (3), a second DC / DC converter (4), a traction motor (5), a first DC / AC inverter (6), an auxiliary motor (7), a second DC / AC inverter (8), and an intermediate direct-current bus (9), wherein the fuel cell (1) is electrically connected to the first DC / DC converter (2); the power battery (3) is electrically connected to the second DC / DC converter (4); the traction motor (5) is electrically connected to the first DC / AC inverter (6); the second DC / AC inverter (8) is electrically connected to the auxiliary motor (7). The total required power of the fuel cell is calculated by means of the difference between the actual intermediate direct-current power of the hybrid power system and the standard power of the power battery, and the number of fuel cell systems to be started and the target output power of a fuel cell system are determined on the basis of the total required power of the fuel cell. The rational starting / stopping of the fuel cell system and the control of the output power are realized, the number of times of starting / stopping the fuel cell is reduced, and the service life of the fuel cell is prolonged. Also disclosed is a control method for a fuel cell hybrid power system.

Description

Fuel cell hybrid power system and control method Technical Field

[0001] This invention relates to the field of power technology, and in particular to fuel cell hybrid power systems and control methods. Background Technology

[0002] As global environmental pollution worsens, developing and utilizing clean energy has become an effective way to address environmental problems. Among various clean energy sources, hydrogen energy is characterized by high efficiency, reliability, and zero pollution. Fuel cells, as a typical application of hydrogen energy, are currently widely used in automobiles, ships, aircraft, and other fields. However, fuel cells have relatively weak adaptability to changes in load power; therefore, in many applications, fuel cells are combined with energy storage devices to form a hybrid power system to power the load.

[0003] In the field of fuel cell locomotives, the total power demand of fuel cells is large and varies widely, necessitating the separate start-stop and power control of multiple fuel cell sets. Existing energy management systems for fuel cell hybrid powertrains in locomotives cannot effectively optimize energy allocation between the fuel cell system and energy storage devices, resulting in high fuel cell system costs, low fuel cell efficiency, and significant resource waste. Technical issues

[0004] To overcome the shortcomings of low combustion efficiency in existing fuel cells, this invention provides a fuel cell hybrid power system and control method. Technical solutions

[0005] The technical solution adopted by this invention to solve its technical problem is: a fuel cell hybrid power system, including a fuel cell, a DC / DC converter I, a power battery, a DC / DC converter II, a traction motor, a DC / AC inverter I, an auxiliary motor, a DC / AC inverter II, and an intermediate DC bus. The fuel cell is electrically connected to DC / DC converter I, the power battery is electrically connected to DC / DC converter II, the traction motor is electrically connected to DC / AC inverter I, and DC / AC inverter II is electrically connected to the auxiliary motor. DC / DC converter I, DC / DC converter II, DC / AC inverter I, and DC / AC inverter II are all electrically connected to the intermediate DC bus.

[0006] According to another embodiment of the invention, the number of fuel cells is more than one, and the number of fuel cells is the same as that of the DC / DC converter.

[0007] According to another embodiment of the present invention, the number of power batteries is more than one, and the number of power batteries is the same as that of the second DC / DC converter.

[0008] A control method for a fuel cell hybrid power system includes the following steps:

[0009] S1. Perform system initialization settings;

[0010] S2. Determine whether the power battery is powered on. If the power battery is not powered on, restart step S2. If the power battery is powered on, proceed to step S3.

[0011] S3. Calculate the total power demand P of the fuel cell. FQ Proceed to step S4;

[0012] S4. Determine if the number of fuel cells started is 0. If it is not 0, proceed to step S5; if it is 0, proceed to step S9.

[0013] S5. Determine the total power demand P of the fuel cell. FQ Is it less than the fuel cell shutdown power P? stop If the value is less than , proceed to step S6; if the value is not less than , proceed to step S12.

[0014] S6. All fuel cells are shut down. After the shutdown is completed, proceed to step S7.

[0015] S7. Determine if the power battery is powered off. If the power battery is powered off, proceed to step S8; otherwise, proceed to step S3.

[0016] S8. Exit this process;

[0017] S9. Compare and sort the lifespans of each group of fuel cells, then proceed to step S10.

[0018] S10. Determine the power demand P of the fuel cell. FQ Is it greater than the fuel cell starting power P? start If it is greater than, proceed to step S11; if it is not greater than, proceed to step S7.

[0019] S11. Start the group of fuel cells that has been used for the shortest time. After starting, proceed to step S3.

[0020] S12, Based on the fuel cell power requirement P FQ Number of fuel cells started (k) and fuel cell shutdown power (P) stop Fuel cell start-up power P start Fuel cell standard power P FS Given the total number of fuel cells N, calculate the number of fuel cells i that should be activated;

[0021] S13. Compare the number of fuel cells to be started i with the number already started k. If k is greater than i, proceed to step S14; if k is not greater than i, proceed to step S15.

[0022] S14. Stop the fuel cells in group ki that have been used for a relatively long time. After the shutdown is completed, proceed to step S3.

[0023] S15. Compare the number of fuel cells to be started i with the number of fuel cells already started k. If k is less than i, proceed to step S16; if k is not less than i, proceed to step S3.

[0024] S16. Start the fuel cells in group IK that have been used for a relatively short time. After the start-up is complete, proceed to step S3.

[0025] According to another embodiment of the present invention, the initialization settings further include a single power battery standard output power P. BSmax Standard input power P of a single power battery BSmin Power battery SOC lower limit C1, power battery SOC lower limit C2, power battery SOC upper limit C3, fuel cell shutdown power P stop Fuel cell start-up power P start Standard power P of a single fuel cell FS The parameters.

[0026] According to another embodiment of the invention, the total power demand P of the fuel cell is further included. FQ For P M and P BS The average difference over a certain period of time, P M P is the intermediate DC output power of the fuel cell hybrid power system. BS This is the standard output power of the power battery.

[0027] According to another embodiment of the present invention, the fuel cell output power control method further includes: the target value of the output power of each group of fuel cells is the total power demand P of the fuel cells. FQ The result is divided by the number of fuel cells i that have been activated.

[0028] According to another embodiment of the present invention, step S12 further includes determining the required power P of the fuel cell. FQ The formula for calculating the number of fuel cells that need to be started or stopped is: P FQ > P stop + (i-1) * P FS

[0029] P FQ < P start + (i-1) * P FS

[0030] 1 ≤ i ≤ N. Beneficial effects

[0031] The beneficial effects of this invention are that it calculates the total power demand of the fuel cell by the difference between the actual DC power of the hybrid power system and the standard power of the power battery, and determines the number of fuel cell system starts and the target output power of the fuel cell system based on the total power demand. This enables reasonable start-up and shutdown of the fuel cell system and output power control, reduces the number of fuel cell start-ups and shutdowns, and improves the service life of the fuel cell. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Figure 1 is a structural block diagram of the present invention;

[0034] Figure 2 is a flowchart of the control method of the present invention;

[0035] Figure 3 shows the P of the present invention. M P BS P FQ Relationship diagram;

[0036] In the diagram: 1. Fuel cell, 2. DC / DC converter one, 3. Power battery, 4. DC / DC converter two, 5. Traction motor, 6. DC / AC inverter one, 7. Auxiliary motor, 8. DC / AC inverter two, 9. Intermediate DC bus. Embodiments of the present invention

[0037] Figure 1 is a structural block diagram of the present invention; Figure 2 is a flowchart of the control method of the present invention; Figure 3 is a P diagram of the present invention. M P BS P FQ Relationship diagram.

[0038] As shown in Figure 1, a fuel cell hybrid power system includes a fuel cell 1, a DC / DC converter 2, a power battery 3, a DC / DC converter 4, a traction motor 5, a DC / AC inverter 6, an auxiliary motor 7, a DC / AC inverter 8, and an intermediate DC bus 9. The fuel cell 1 is electrically connected to the DC / DC converter 2, the power battery 3 is electrically connected to the DC / DC converter 4, the traction motor 5 is electrically connected to the DC / AC inverter 6, the DC / AC inverter 8 is electrically connected to the auxiliary motor 7, and the DC / DC converter 2, DC / DC converter 4, DC / AC inverter 6, and DC / AC inverter 8 are all electrically connected to the intermediate DC bus 9.

[0039] The intermediate DC bus 9 is the energy collection point. The intermediate DC bus 9 is connected to the intermediate DC link.

[0040] The energy output from fuel cell 1 via its matching DC / DC converter 2 is combined with the energy output from power battery 3 via its matching DC / DC converter 4 at the intermediate DC bus 9. Fuel cell 1 can supply power to intermediate DC bus 9. Power battery 3 can supply power to intermediate DC bus 9 or absorb power from intermediate DC bus 9. Traction motor 5 obtains power from intermediate DC bus 9 via its matching DC / AC inverter 6 and converts it into kinetic energy. It can also convert kinetic energy into electrical energy and input it in reverse to intermediate DC bus 9 via DC / AC inverter 6. Auxiliary motor 7 obtains power from intermediate DC bus 9 via its matching DC / AC inverter 8 and converts it into kinetic energy.

[0041] The number of fuel cells 1 is more than one, and the number of fuel cells 1 is the same as that of DC / DC converter 2.

[0042] One fuel cell unit 1 and one DC / DC converter 2 constitute one fuel cell system, which can output electrical energy with controllable power. One to N fuel cell systems are connected in parallel to the intermediate DC bus 9 of the hybrid power system. One to N fuel cell units 1 can be partially or fully started to provide electrical energy at different power levels.

[0043] The number of power batteries 3 is more than one, and the number of power batteries 3 is the same as that of DC / DC converter 4.

[0044] One set of power batteries 3 and one set of DC / DC converters 4 constitute one power battery system, which can output and input electrical energy with controllable power. One to M sets of power battery systems are connected in parallel to the intermediate DC bus 9 of the hybrid power system. One to M sets of power batteries 3 can be partially or fully started to provide or absorb electrical energy that cannot be supplied.

[0045] The working mode of this application is as follows: the locomotive operating conditions mainly include traction operating conditions and power braking operating conditions.

[0046] In locomotive traction mode, traction motor 5 obtains electrical energy from intermediate DC bus 9 through the matching DC / AC inverter 1 6, converts it into kinetic energy, and drives the wheels to rotate. Auxiliary motor 7 obtains electrical energy from intermediate DC bus 9 through the matching DC / AC inverter 2 8, converting it into kinetic energy.

[0047] Under traction conditions, if the traction motor 5 requires a large power, the fuel cell system and the power battery system simultaneously converge to the intermediate DC bus 9 to provide power to the intermediate DC link. During this process, the power battery 3 is in a discharge condition, and the power battery 3 will gradually decrease in power.

[0048] Under traction conditions, if the traction motor 5 requires less power and the power battery 3 has sufficient charge, the power battery 3 can supply power to the intermediate DC link. At this time, the power battery is in discharge condition and the power battery 3 will gradually decrease in charge.

[0049] Under traction conditions, if the traction motor 5 requires less power and the power battery 3 has less charge, the fuel cell 1 can provide more energy to the intermediate DC link. Part of the energy is used to power the traction motor 5 and the auxiliary motor 7, and part of the energy is used to charge the power battery 3. At this time, the charge of the power battery 3 will gradually increase.

[0050] In dynamic braking mode, traction motor 5 obtains kinetic energy from the wheels and converts it into electrical energy, which is then supplied to the intermediate DC link via the matching DC / AC inverter 6. The energy from the intermediate DC link is preferentially used to power auxiliary motor 7, and excess energy is used to charge power battery 3, during which the charge of power battery 3 will gradually increase.

[0051] Under dynamic braking conditions, if the output power of the traction motor 5 is low and the power battery 3 has low charge, the fuel cell 1 and the traction motor 5 simultaneously provide energy to the intermediate DC link. At this time, the power battery obtains energy from the intermediate DC link to charge, and the charge of the power battery 3 will gradually increase.

[0052] Under dynamic braking conditions, if the traction motor 5 has a high output power or the power battery 3 has a high charge level, the fuel cell 1 will shut down or reduce its output power to ensure that the charging current of the power battery 3 does not exceed the specified value. If the charging current of the power battery 3 still exceeds the specified value after the fuel cell 1 is completely shut down, the output power of the traction motor 5 needs to be reduced.

[0053] During operation, the locomotive frequently switches between traction and power braking modes. Simultaneously, the output and input power of the traction motor 5 also fluctuate frequently during acceleration and deceleration. During this process, the state of charge (SOC) of the power battery 3 must be maintained within a reasonable range so that it can both absorb and provide electrical energy, ensuring the normal operation of the locomotive. Therefore, when the fuel cell hybrid system is operating, the number of fuel cells 1 activated and their output power must be controlled according to the different states of the locomotive.

[0054] As shown in Figure 2, a control method for a fuel cell hybrid power system includes the following steps:

[0055] S1. Perform system initialization settings;

[0056] S2. Determine whether the power battery 3 is powered on. If the power battery 3 is not powered on, restart step S2. If the power battery 3 is powered on, proceed to step S3.

[0057] S3. Calculate the total power demand P of fuel cell 1. FQ Proceed to step S4;

[0058] S4. Determine if the number of fuel cells 1 started is 0. If it is not 0, proceed to step S5; if it is 0, proceed to step S9.

[0059] S5. Determine the total power demand P of fuel cell 1. FQ Is it less than the shutdown power P of fuel cell 1? stop If the value is less than , proceed to step S6; if the value is not less than , proceed to step S12.

[0060] S6. All fuel cells 1 are shut down. After the shutdown is completed, proceed to step S7.

[0061] S7. Determine whether the power battery 3 is powered off. If the power battery 3 is powered off, proceed to step S8; otherwise, proceed to step S3.

[0062] S8. Exit this process;

[0063] S9. Compare and sort the lifespans of each group of fuel cells 1, and proceed to step S10.

[0064] S10. Determine the power demand P of fuel cell 1. FQ Is it greater than the fuel cell starting power P? start If it is greater than, proceed to step S11; if it is not greater than, proceed to step S7.

[0065] S11. Start the group of fuel cells 1 that has been used for the shortest time. After starting, proceed to step S3.

[0066] S12, Based on the power demand P of fuel cell 1 FQ The number of fuel cells 1 started (k) and the shutdown power (P) of fuel cells 1 are as follows: stop Fuel cell start-up power P start Fuel cell standard power P FS Given the total number of fuel cells N, calculate the number of fuel cells i that should be activated;

[0067] S13. Compare the number of fuel cells i to be started with the number k that has already been started. If k is greater than i, proceed to step S14; if k is not greater than i, proceed to step S15.

[0068] S14. Stop fuel cell 1 in group ki, which has been used for a relatively long time. After the shutdown is completed, proceed to step S3.

[0069] S15. Compare the number of fuel cells 1 to be started i with the number of fuel cells 1 already started k. If k is less than i, proceed to step S16; if k is not less than i, proceed to step S3.

[0070] S16. Start the fuel cell 1 of the ik group, which has been used for a relatively short time. After the start-up is completed, proceed to step S3.

[0071] Initialization settings include a single power battery pack with a standard output power of 3P. BSmax 1. Single-cell power battery 3 standard input power P BSmin 1. Lower limit of 3SOC of power battery C1, 2. Lower limit of 3SOC of power battery C2, 3. Upper limit of 3SOC of power battery C3, 3. Shutdown power of fuel cell 1 P stop Fuel cell 1 start-up power P start A single fuel cell unit has a standard power output of P. FS The parameters.

[0072] Fuel cell 1 shutdown power P stop If the required power is less than this power, fuel cell 1 needs to be shut down.

[0073] Fuel cell 1 start-up power P start When the required power exceeds this power, fuel cell 1 needs to be started.

[0074] Single fuel cell 1 standard power P FS This power is a range value, within which fuel cell efficiency and lifespan are both relatively high.

[0075] Total power demand P of fuel cell 1 FQ For P M and P BS The average difference over a certain period of time.

[0076] P M P is the intermediate DC output power of the fuel cell hybrid power system. M A positive value indicates that the intermediate DC link supplies power to the traction motor 5 and the auxiliary motor 7, while a negative value indicates that the traction motor 5 feeds power back to the intermediate DC link.

[0077] P BS This is the standard output power of the power battery. (P) BS Positive values ​​represent the discharge power of power battery 3, while negative values ​​represent the charging power of power battery 3.

[0078] As shown in Figure 3, the standard power of the power battery 3 varies depending on the current state of charge (SOC) of the power battery 3. In step S1, the parameters are configured, and the standard power of the power battery can be calculated in real time based on the configured parameters and the current of the power battery 3.

[0079] The power of the intermediate DC link in the hybrid power system is constantly changing, therefore the calculated total power demand P of fuel cell 1 is... FQAn average value over a certain period needs to be calculated for subsequent calculations. This average value is typically taken over 3 to 5 minutes.

[0080] The output power control method for fuel cell 1 is as follows: the target output power of each group of fuel cells 1 is the total power demand P of fuel cell 1. FQ The result is divided by the number of fuel cells i that have been activated.

[0081] In step S12, the required power P of the fuel cell 1 is... FQ The formula for calculating the number of fuel cells that need to be started or stopped is as follows:

[0082] P FQ > P stop + (i-1) * P FS

[0083] P FQ < P start + (i-1) * P FS

[0084] 1 ≤ i ≤ N.

Claims

1. A fuel cell hybrid power system, characterized in that, The system includes a fuel cell (1), a DC / DC converter I (2), a power battery (3), a DC / DC converter II (4), a traction motor (5), a DC / AC inverter I (6), an auxiliary motor (7), a DC / AC inverter II (8), and an intermediate DC bus (9). The fuel cell (1) is electrically connected to the DC / DC converter I (2), the power battery (3) is electrically connected to the DC / DC converter II (4), the traction motor (5) is electrically connected to the DC / AC inverter I (6), and the DC / AC inverter II (8) is electrically connected to the auxiliary motor (7). The DC / DC converter I (2), DC / DC converter II (4), DC / AC inverter I (6), and DC / AC inverter II (8) are all electrically connected to the intermediate DC bus (9).

2. The fuel cell hybrid power system according to claim 1, characterized in that, The number of fuel cells (1) is more than one, and the number of fuel cells (1) is the same as that of DC / DC converter (2).

3. The fuel cell hybrid power system according to claim 1, characterized in that, The number of power batteries (3) is more than one, and the number of power batteries (3) is the same as that of DC / DC converter two (4).

4. A control method for a fuel cell hybrid power system according to claim 1, 2, or 3, characterized in that, Includes the following steps: S1. Perform system initialization settings; S2. Determine whether the power battery (3) is powered on. If the power battery (3) is not powered on, restart step S2. If the power battery (3) is powered on, proceed to step S3. S3. Calculate the total power demand P of the fuel cell (1). FQ Proceed to step S4; S4. Determine if the number of fuel cells (1) started is 0. If it is not 0, proceed to step S5; if it is 0, proceed to step S9. S5. Determine the total power demand P of the fuel cell (1). FQ Is it less than the shutdown power P of the fuel cell (1)? stop If the value is less than , proceed to step S6; if the value is not less than , proceed to step S12. S6. All fuel cells (1) are shut down. After the shutdown is completed, proceed to step S7. S7. Determine whether the power battery (3) is powered off. If the power battery (3) is powered off, proceed to step S8; otherwise, proceed to step S3. S8. Exit this process; S9. Compare and sort the lifespans of each group of fuel cells (1), and proceed to step S10; S10. Determine the required power P of the fuel cell (1). FQ Is it greater than the fuel cell starting power P? start If it is greater than, proceed to step S11; if it is not greater than, proceed to step S7. S11. Start the group of fuel cells (1) that has been used for the shortest time. After starting, proceed to step S3. S12, based on the power demand P of fuel cell (1) FQ The number of fuel cells (1) started (k) and the power of fuel cell shutdown (P) are as follows: stop Fuel cell start-up power P start Fuel cell standard power P FS Given the total number of fuel cells N, calculate the number of fuel cells i that should be activated; S13. Compare the number of fuel cells (1) to be started (i) with the number already started (k). If k is greater than i, proceed to step S14; if k is not greater than i, proceed to step S15. S14. Stop the fuel cell (1) in group ki that has been used for a relatively long time. After the shutdown is completed, proceed to step S3. S15. Compare the number of fuel cells (1) to be started (i) with the number of fuel cells (1) already started (k). If k is less than i, proceed to step S16; if k is not less than i, proceed to step S3. S16. Start the fuel cell (1) of the ik group that has been used for a relatively short time. After the start-up is completed, proceed to step S3.

5. The control method for a fuel cell hybrid power system according to claim 4, characterized in that, The initialization settings include the standard output power P of a single power battery (3). BSmax 1. Standard input power P of a single power battery (3) BSmin 、Power battery (3) lower limit of SOC C1、Power battery (3) lower limit of SOC C2、Power battery (3) upper limit of SOC C3、Fuel cell (1) shutdown power P stop Fuel cell (1) Start-up power P start 1. Standard power P of a single fuel cell (1) FS The parameters.

6. The control method for a fuel cell hybrid power system according to claim 4, characterized in that, The total power demand P of the fuel cell (1) FQ For P M and P BS The average difference over a certain period of time, P M For the intermediate DC output power of the fuel cell (1) hybrid power system, P BS This is the standard output power of the power battery.

7. The control method for a fuel cell hybrid power system according to claim 4, characterized in that, The output power control method of the fuel cell (1) is as follows: the target output power of each group of fuel cells (1) is the total power demand P of the fuel cell (1). FQ The result is divided by the number of fuel cells (1) i that have been started.

8. The control method for a fuel cell hybrid power system according to claim 4, characterized in that, In step S12, the required power P of the fuel cell (1) FQ The formula for calculating the number of fuel cells (1) that need to be started or stopped is as follows: P FQ > P stop + (i-1) * P FS P FQ < P start + (i-1) * P FS 1 ≤ i ≤ N.

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