阅读说明：本技术 多燃料电池的混合动力系统及其能量管理方法、装置 (Hybrid power system with multiple fuel cells and energy management method and device thereof ) 是由 韩国鹏 裴春兴 冯轩 王艳琴 汪星华 刘楠 赵丽丽 于 2021-08-05 设计创作，主要内容包括：本申请实施例提供了一种多燃料电池的混合动力系统及其能量管理方法、装置,该混合动力系统包括：动力电池,其连接到直流母线；燃料电池系统,其包括至少两个并联的支路,每个支路中串联有至少两个燃料电池,各支路分别通过一DC/DC模块连接到所述直流母线,每个燃料电池的两端并联有旁路隔离开关,所述旁路隔离开关用于将燃料电池接入到所述燃料电池系统中进行供电或将燃料电池从所述燃料电池系统中切除。本实施例将多个燃料电池通过串、并联结合方式组成燃料电池系统,采用多串联-多并联的拓扑结构,且在串联燃料电池两端并联旁边隔离开关,在保证系统有较高效率、体积重量较轻的同时具有高可控性。(The embodiment of the application provides a hybrid power system with multiple fuel cells and an energy management method and device thereof, wherein the hybrid power system comprises: a power battery connected to the DC bus; the fuel cell system comprises at least two parallel branches, wherein at least two fuel cells are connected in series in each branch, each branch is connected to the direct current bus through a DC/DC module, two ends of each fuel cell are connected in parallel with a bypass isolating switch, and the bypass isolating switch is used for connecting the fuel cell into the fuel cell system to supply power or cutting the fuel cell from the fuel cell system. In the embodiment, a plurality of fuel cells form a fuel cell system in a series-parallel combination mode, a multi-series-multi-parallel topological structure is adopted, and the two ends of the series fuel cells are connected with the adjacent isolating switches in parallel, so that the system has high efficiency, lighter volume and weight and high controllability.)

1. A multi-fuel cell hybrid system, comprising:

a power battery connected to the DC bus;

the fuel cell system comprises at least two parallel branches, wherein at least two fuel cells are connected in series in each branch, each branch is connected to the direct current bus through a DC/DC module, two ends of each fuel cell are connected in parallel with a bypass isolating switch, and the bypass isolating switch is used for connecting the fuel cell into the fuel cell system to supply power or cutting the fuel cell from the fuel cell system.

2. The system of claim 1, wherein the fuel cell system comprises a first branch and a second branch connected in parallel, and each branch has four fuel cells connected in series.

3. A method for managing energy of a hybrid system with multiple fuel cells, which is applied to the hybrid system according to claim 1 or 2, the method comprising:

acquiring a current main state value of a hybrid power system, wherein the main state value represents a power supply state of the hybrid power system at the current moment, and the power supply state is determined by a power supply topological structure formed by a battery which can supply power to the outside in the hybrid power system;

and after receiving a high-voltage starting instruction, starting a corresponding battery in the hybrid power system according to a preset starting strategy corresponding to the main state value, and performing energy management on the started battery of the hybrid power system according to the main state value and the required power of the vehicle.

4. The method of claim 3, wherein said obtaining a current primary state value of the hybrid powertrain system comprises:

acquiring a fault state value Alarm _ Bat of the power battery;

acquiring a state number FCs _ Hstate of a fuel cell system, wherein FCs _ Hstate represents the total number of fuel cells which can supply power to the outside in the fuel cell system;

and determining a main state value HBS _ state of the hybrid power system according to Alarm _ Bat and FCs _ Hstate.

5. The method according to claim 4, wherein the obtaining the number of states of the fuel cell system FCs _ Hstate comprises:

identifying a fault condition of each fuel cell individually, the fault condition including normal or fault;

respectively counting the state reference number FCs _ Hstate _ i _ re of each branch according to the fault state of each fuel cell, wherein FCs _ Hstate _ i _ re represents the number of the fuel cells with normal fault states in the ith branch;

and determining the state number FCs _ Hstate according to the state reference number FCs _ Hstate _ i _ re of each branch.

6. The method of claim 5 wherein said determining said state number FCs _ Hstate based on a state reference number FCs _ Hstate _ i _ re for each leg comprises:

judging whether a hydrogen storage system connected with the fuel cell system fails;

if the hydrogen storage system does not have a fault, judging whether the DC/DC module connected with each branch circuit has a fault;

assigning a state reference number FCs _ Hstate _ i _ re of a branch without the fault of the DC/DC module to a state target number FCs _ Hstate _ i of the branch, and setting the state target number FCs _ Hstate _ i of the branch with the fault of the DC/DC module to zero, wherein FCs _ Hstate _ i represents the number of fuel cells which can supply power to the outside in the ith branch;

and obtaining the state number FCs _ Hstate according to the sum of the state target numbers FCs _ Hstate _ i of the branches.

7. The method of claim 6, after determining whether a hydrogen storage system to which the fuel cell system is connected is malfunctioning, the method further comprising:

and if the hydrogen storage system fails, directly setting the state number FCs _ Hstate of the fuel cell system to zero.

8. The method of claim 6, wherein said determining a main state value HBS _ state of the hybrid powertrain system from Alarm _ Bat and FCs _ Hstate comprises:

when Alarm _ Bat indicates that the power battery is normal and FCs _ Hstate is equal to M, assigning a main state value HBS _ state as a target value, wherein M is the total number of fuel batteries contained in the fuel battery system, and the target value corresponds to the normal power supply state of the hybrid power system;

when Alarm _ Bat indicates that the power battery is normal and FCs _ Hstate belongs to [1, M-1], assigning the main state value HBS _ state to be a first numerical value, wherein the first numerical value corresponds to the hybrid power supply state of the hybrid power system;

when Alarm _ Bat indicates that the power battery is normal and FCs _ Hstate is equal to 0, assigning the main state value HBS _ state to be a second numerical value, wherein the second numerical value corresponds to the power supply state of a single power battery of the hybrid power system;

when Alarm _ Bat indicates that the power battery has a fault and FCs _ Hstate is equal to M, assigning the main state value HBS _ state to be a third value, wherein the third value corresponds to the power supply state of a single fuel battery of the hybrid power system;

when Alarm _ Bat represents the power battery fault and FCs _ Hstate belongs to [ M ', M-1], assigning the main state value HBS _ state to be a fourth numerical value, wherein M' is the basic number of the fuel batteries meeting the lowest power supply requirement of the vehicle, and the fourth numerical value corresponds to the single-fuel-battery fault power supply state of the hybrid power system;

and when Alarm _ Bat represents the power battery fault and FCs _ Hstate is in the range of 0, M'), assigning the main state value HBS _ state to be a fifth value, wherein the fifth value corresponds to the fault state of the hybrid power system.

9. The method of claim 8, wherein starting the corresponding battery in the hybrid system according to the preset starting strategy corresponding to the main state value comprises:

when the HBS _ state is equal to a target value, sequentially starting one of the branches of the power battery and the fuel cell system and the DC/DC module, and setting the DC/DC module to be in a current source working mode;

when the HBS _ state is equal to a first value, sequentially starting a power battery, one branch of a fuel cell system and a DC/DC module, cutting off a fault fuel cell in the fuel cell system from the fuel cell system through a bypass isolating switch, and setting the DC/DC module to be in a current source working mode;

when the HBS _ state is equal to the second value, starting the power battery;

when the HBS _ state is equal to a third value, starting the fuel cell system and the DC/DC module in sequence and setting the DC/DC module to a voltage source operating mode;

and when the HBS _ state is equal to a fourth value, sequentially starting the fuel cell system and the DC/DC module, cutting off a fault fuel cell in the fuel cell system from the fuel cell system through a bypass isolating switch, and setting the DC/DC module to be in a voltage source working mode.

10. The method of claim 9, wherein starting one of the legs in the fuel cell system comprises:

and starting one branch with fewer normal fuel cells in the two branches connected in parallel of the fuel cell system.

11. The method of claim 9, wherein the energy managing the hybrid system activated battery based on the primary state value and vehicle demanded power comprises:

when the HBS _ state is equal to a target value or a first value, performing global power distribution on the fuel cell system according to the vehicle required power to obtain the target output power of the fuel cell system;

controlling the power output of the fuel cell system according to the target output power.

12. The method according to claim 11, wherein the globally allocating power to the fuel cell system according to the vehicle required power to obtain the target output power of the fuel cell system comprises:

when the state of charge SOC of the power battery is larger than SOCmax, if the required power of the vehicle is larger than the sum of the maximum available electric power of the power battery and the maximum available electric power of the fuel cell system, taking the maximum available electric power of the fuel cell system as the target output power and generating a system power shortage prompt, otherwise, taking the minimum available electric power of the fuel cell system as the target output power;

wherein SOCmax is the upper limit of the SOC control range.

13. The method according to claim 12, wherein the globally allocating power to the fuel cell system according to the vehicle required power to obtain the target output power of the fuel cell system comprises:

when the SOC epsilon (SOCmin, SOCmax) of the power battery,

if the required power of the vehicle is larger than the sum of the maximum available electric power of the power battery and the maximum available electric power of the fuel cell system, taking the maximum available electric power of the fuel cell system as the target output power, and generating a system power shortage prompt;

if the required power of the vehicle is between the maximum available electric power of the fuel cell system and the maximum available electric power of the hybrid power system, determining the target output power according to the size relation between the SOC and the SOCpower of the power battery;

if the required power of the vehicle is not in the two ranges, taking the minimum available electric power of the fuel cell system as the target output power;

wherein SOCmin is the lower limit of the SOC control range, SOCwindow is the middle reference value of the SOC control range, and SOCmin < SOCwindow < SOCmax.

14. The method of claim 13, wherein determining the target output power according to the magnitude relation between the SOC and socbrown of the power battery comprises:

when the SOC of the power battery is epsilon (SOCmin, SOCwindow), taking the maximum available electric power of the fuel cell system as the target output power;

when the SOC epsilon (SOCbrown, SOCmax) of the power battery, the vehicle required power is taken as the target output power.

15. The method according to claim 13, wherein the globally allocating power to the fuel cell system according to the vehicle required power to obtain the target output power of the fuel cell system comprises:

and when the SOC of the power battery is less than or equal to the SOCmin, taking the maximum available electric power of the fuel cell system as the target output power and generating a power reduction prompt.

16. The method according to any one of claims 11 to 15, wherein the controlling the power output of the fuel cell system according to the target output power includes:

according to the target output power, carrying out local power distribution between two branches of the fuel cell system connected in parallel to obtain a power distribution value of each branch;

determining a power separation point according to the number of the normal fuel cells of each branch circuit; the power separation point is obtained by determining a total external power-battery working efficiency curve of the branch according to the number of normal fuel cells of each branch and taking the intersection point of the total external power-battery working efficiency curves of the branches of the two branches;

when the target output power is less than or equal to the power corresponding to the power separation point, controlling the fuel cell in the currently started branch to operate according to the power distribution value corresponding to the branch;

and when the target output power is greater than the power corresponding to the power separation point, starting the other branch of the two branches, and controlling the fuel cells in the two branches to operate according to the corresponding power distribution value.

17. The method according to claim 16, wherein the performing the local power distribution between the two branches of the fuel cell system connected in parallel according to the target output power to obtain the power distribution value of each branch comprises:

dividing the target output power by the total number of the fuel cells in the normal state in the two branches to obtain a power output value of a single normal fuel cell;

and multiplying the power output value of the single normal fuel cell by the number of the fuel cells in the normal state in each branch to obtain the power distribution value of each branch.

18. The method of claim 9, wherein the energy managing the hybrid system activated battery based on the primary state value and vehicle demanded power comprises:

when HBS _ state equals a second value, a limp home alert and a maximum allowed discharge current of a power battery are sent to a vehicle controller VCU, so that the VCU updates a vehicle demanded power according to the maximum allowed discharge current after receiving the limp home alert.

19. The method of claim 18, further comprising:

and when the SOC of the power battery is gradually reduced to be lower than the warning value SOC _ low _ alarm2, the power battery is shut down.

20. The method of claim 9, wherein the energy managing the hybrid system activated battery based on the primary state value and vehicle demanded power comprises:

when the HBS _ state is equal to a third value or a fourth value, dividing the target output power by the total number of the fuel cells in the normal state in two branches of the parallel hybrid power system to obtain a power output value of a single normal fuel cell;

multiplying the power output value of a single normal fuel cell by the number of the fuel cells in the normal state in each branch to obtain the power distribution value of each branch;

and setting the current value of each branch according to the power distribution value of each branch so as to control the fuel cell in each branch to output power according to the corresponding power distribution value.

21. The method of claim 3, further comprising:

and after receiving a shutdown command, shutting down all started batteries in the hybrid power system.

22. An energy management device of a hybrid system with multiple fuel cells, which is applied to the hybrid system according to claim 1 or 2, the device comprising:

the main state determining module is used for acquiring a current main state value of the hybrid power system, wherein the main state value represents a power supply state of the hybrid power system at the current moment, and the power supply state is determined by a power supply topological structure formed by a battery which can supply power to the outside in the hybrid power system;

and the energy management module is used for starting a corresponding battery in the hybrid power system according to a preset starting strategy corresponding to the main state value after receiving a high-voltage starting instruction, and performing energy management on the started battery of the hybrid power system according to the main state value and the required power of the vehicle.

Technical Field

The application relates to the technical field of battery energy management, in particular to a hybrid power system with multiple fuel cells and an energy management method and device thereof.

Background

The rail vehicle power system usually adopts an electric-electric hybrid power system formed by a fuel cell/a power cell. Compared with automobiles, the hybrid power system of the rail vehicle requires large power, generally adopts a high-power fuel cell system developed in a customized manner, and has high cost and low technical maturity; the low-power fuel cell, although mature in technology and strong in selectivity, cannot be directly applied to the rail vehicle due to low single-machine power.

The hybrid power system of the existing railway vehicle mainly adopts a high-power fuel cell to perform simple parallel power supply, as shown in fig. 1. In the scheme, each high-power fuel cell is connected to a direct current bus through a DC/DC module, and the power cell adopts a direct-hanging bus mode. The hybrid power system power supply scheme that the high-power fuel cells are simply connected in parallel is adopted, and the single fuel cell has high power requirement, generally needs customized development and has high cost; under the influence of the working characteristics of the fuel cell, when the power required by the vehicle is smaller, the high-power fuel cell is at a low efficiency point, which is not beneficial to improving the system efficiency; due to the small number of fuel cells in the system, when two fuel cells fail, the hybrid system loses energy sources and cannot continuously operate.

Disclosure of Invention

The embodiment of the application provides a hybrid power system with multiple fuel cells and an energy management method and device thereof, so as to solve the technical problems.

In a first aspect, an embodiment of the present application provides a hybrid power system with multiple fuel cells, including:

a power battery connected to the DC bus;

the fuel cell system comprises at least two parallel branches, wherein at least two fuel cells are connected in series in each branch, each branch is connected to the direct current bus through a DC/DC module, two ends of each fuel cell are connected in parallel with a bypass isolating switch, and the bypass isolating switch is used for connecting the fuel cell into the fuel cell system to supply power or cutting the fuel cell from the fuel cell system.

In a second aspect, an embodiment of the present application provides an energy management method for a hybrid power system with multiple fuel cells, where the method is applied to the hybrid power system according to the first aspect, and the method includes:

acquiring a current main state value of a hybrid power system, wherein the main state value represents a power supply state of the hybrid power system at the current moment, and the power supply state is determined by a power supply topological structure formed by a battery which can supply power to the outside in the hybrid power system;

and after receiving a high-voltage starting instruction, starting a corresponding battery in the hybrid power system according to a preset starting strategy corresponding to the main state value, and performing energy management on the started battery of the hybrid power system according to the main state value and the required power of the vehicle.

In a third aspect, an embodiment of the present application provides an energy management apparatus for a hybrid power system with multiple fuel cells, where the apparatus is applied to the hybrid power system as described in the first aspect, and the apparatus includes:

the main state determining module is used for acquiring a current main state value of the hybrid power system, wherein the main state value represents a power supply state of the hybrid power system at the current moment, and the power supply state is determined by a power supply topological structure formed by a battery which can supply power to the outside in the hybrid power system;

and the energy management module is used for starting a corresponding battery in the hybrid power system according to a preset starting strategy corresponding to the main state value after receiving a high-voltage starting instruction, and performing energy management on the started battery of the hybrid power system according to the main state value and the required power of the vehicle.

By adopting the technical scheme, a plurality of low-power fuel cells can be connected in series and in parallel to form a complex fuel cell system, and compared with a simple parallel scheme of a high-power fuel cell, the cost can be reduced and the system efficiency can be improved; the fuel cell system designed by combining the characteristics of the series connection mode and the parallel connection mode adopts a multi-series-multi-parallel connection topological structure, and the two ends of the series connection fuel cell are connected with the bypass isolating switch in parallel to connect the fuel cell into the fuel cell system or cut the fuel cell from the fuel cell system, so that when any one fuel cell in a branch circuit fails through the bypass isolating switch, the failed fuel cell is cut off the system in time and is connected into the system again after the failure is relieved, the defects of low reliability of the series branch circuit and high cost of the parallel branch circuit are overcome, and the reliability of the fuel cell system coupled by the multi-fuel cell is improved, so that the scheme has high efficiency, lighter volume and weight while ensuring the system to have high controllability.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 shows a schematic representation of a hybrid powertrain of a prior art rail vehicle;

FIG. 2 shows a schematic structural diagram of a hybrid power system of a rail vehicle in an embodiment of the present application;

FIG. 3 is a flow chart illustrating a method for energy management of a multi-fuel cell hybrid system according to an embodiment of the present disclosure;

fig. 4 is a flowchart showing a procedure of determining the main state value HBS _ state in the embodiment of the present application;

FIG. 5 is a flowchart showing the detailed process of step 220 in FIG. 4;

fig. 6 is a flowchart showing a specific process of controlling the power output of the fuel cell system according to the target output power in the embodiment of the present application;

fig. 7 shows a schematic diagram of an energy management device of a multi-fuel cell hybrid power system provided by an embodiment of the application.

Detailed Description

The following detailed description of exemplary embodiments of the present application, taken in conjunction with the accompanying drawings, makes it apparent that the described embodiments are only some embodiments of the application, and are not exhaustive of all embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

In the embodiment of the present application, a plurality of low-power fuel cells are connected in series and in parallel to form a complex fuel cell system, fig. 2 shows a schematic structural diagram of a hybrid power system provided in the embodiment of the present application, please refer to fig. 2, where the hybrid power system includes: the fuel cell system comprises at least two parallel branches, at least two fuel cells are connected in series in each branch, each branch is connected to a direct current bus through a DC/DC module, specifically, all the fuel cells on the same branch are connected to the direct current bus through the DC/DC module after being connected in series, and the power cells are connected to the same direct current bus. In the hybrid power system, the power battery is used for maintaining the bus voltage, and the characteristic of large capacity can prevent the sudden change of the bus voltage and play a role in peak clipping and valley filling; the fuel cell system is used as the final energy source of the whole hybrid power system, and the output power of the fuel cell system can be adjusted according to the state of charge (SOC) of the power cell and the required power of the vehicle, and is the main control variable of energy management.

In one embodiment, the fuel cell system comprises two parallel branches, namely a first branch and a second branch, wherein each branch is connected with four fuel cells in series, as shown in fig. 2, and the fuel cell system has a 4-series-2-parallel topology. It is understood that the fuel cell system may have three, four or even more branches connected in parallel, and the number of fuel cells connected in series in each branch may be equal or different.

On the same branch, the series current is equal, the voltage is the sum of the voltages of all the fuel cells, 4 series fuel cells are connected to the input end of one DC/DC module, the boost ratio of the DC/DC module is controlled to be a small value, and the electricity-electricity conversion efficiency is improved; the DC/DC module mainly has the functions of boosting and stabilizing voltage, the boosting is that because the output power of the fuel cell can not meet the use requirement of a vehicle, imbalance can occur when the fuel cell monomers are connected in series too much, so that the performance is reduced, the output voltage set by a fuel cell manufacturer is lower, and boosting is needed; voltage stabilization is due to the fact that the fuel cell has soft output characteristics, and the voltage drops rapidly due to the increase of current, so that the fuel cell and the DC/DC module need to be used together.

The parallel branch circuit guarantees the power requirement of the vehicle and improves the power supply reliability of the vehicle; the bypass isolating switches are connected in parallel at two ends of each fuel cell to connect the fuel cell into the fuel cell system for power supply or cut the fuel cell from the fuel cell system, so that when any one fuel cell in a branch circuit fails through the bypass isolating switches, the failed fuel cell is timely cut off from the system and is reconnected into the system after the failure is relieved, thereby overcoming the defects of low reliability of serial branch circuits and high cost of parallel branch circuits and improving the reliability of the fuel cell system coupled by multiple fuel cells; the hydrogen storage system provides hydrogen gas to the entire fuel cell system. The energy control unit controls each unit (power battery, each fuel battery, hydrogen storage system, and DC/DC module) in the hybrid system.

The topological structure of the hybrid power system can solve the problem of coupling power supply of the fuel cell system with multiple fuel cells on the rail vehicle. The multiple fuel cells can form a fuel cell system in a series-parallel mode, but the fuel cell system comprises the following components: the parallel connection mode needs to be provided with one DC/DC module for each fuel cell, so that the system has larger volume and weight, the higher voltage boosting ratio causes the reduction of the electric-electric conversion efficiency, and the comprehensive cost of the system is high; a single fuel cell in the series will fail to operate in the entire branch connected in series, resulting in poor system reliability and controllability. Therefore, the design of the fuel cell system is carried out by combining the characteristics of two connection modes, a multi-series-multi-parallel topology structure is adopted, and the adjacent isolating switches are connected to two ends of the series fuel cell in parallel, so that the system has high efficiency, lighter volume and weight and high controllability.

According to the topology shown in fig. 2, the hybrid power system with multiple fuel cells supplies power for 6 states as follows:

(1) normally supplying power;

(2) limp-hybrid power supply;

(3) limp-single power battery powered;

(4) limp-single fuel cell powered;

(5) limp-single fuel cell failure power;

(6) a hybrid system failure.

The power supply state is determined according to a power supply topological structure formed by a battery which can supply power to the outside in the hybrid power system. The fault states of all units (a power battery, a fuel battery, a hydrogen storage system and a DC/DC module) in the hybrid power system are uniformly divided into three levels, wherein the level 0 represents no fault, the level 1 represents that some parameters deviate from normal values, attention needs to be paid, and the operation is not influenced; level 2 indicates a fault. The fault levels are level 0 and level 1, the fault state is considered normal, the fault state is level 2, and the fault state is considered fault.

When one or more fuel cells in the system fail to generate power, the fuel cell in a normal state can continue to generate power by cutting off the failed fuel cell, but because the failure state of the fuel cell system has various forms, the power supply state of the hybrid power system has great difference, so that the reliable application of the system can be realized only by solving the energy management problem of the hybrid power system with multiple fuel cells in different failure states. The power supply state of the system is identified according to the main state value of the hybrid power system, and the entrance is provided for different energy control strategies, so that the power supply application of the low-power fuel cell on the rail vehicle is realized.

The present embodiment provides an energy management method based on the hybrid power system, where the steps of the method are executed by an electronic control unit ECU on a rail vehicle, please refer to fig. 3, and the method includes:

and step 110, acquiring a current main state value of the hybrid system.

And step 120, after receiving the high-voltage starting instruction, starting a corresponding battery in the hybrid power system according to a preset starting strategy corresponding to the main state value.

And step 130, performing energy management on the battery of which the hybrid power system is started according to the main state value and the required power of the vehicle.

The following describes specific embodiments of each step from step 110 to step 130:

in step 110, after the vehicle is started, the controller connected to each unit (power battery, fuel cell, hydrogen storage system and DC/DC module) in the hybrid system is powered on to automatically complete self-test, and the fault status of each unit is sent to the ECU for subsequent judgment. The fault state is uniformly divided into three levels, wherein the level 0 indicates no fault, and the level 1 indicates that some parameters deviate from normal values, attention needs to be paid, but the operation is not influenced; level 2 indicates a fault. The fault levels are level 0 and level 1, the fault state is considered normal, the fault state is level 2, and the fault state is considered fault.

And after receiving the fault states of the units sent by the controllers, the ECU determines the main state value of the hybrid system at the current moment according to the fault states of the units.

Specifically, fig. 4 shows a process of determining the main state value HBS _ state in this embodiment, please refer to fig. 4, which includes the following specific processes:

and step 210, acquiring a fault state value Alarm _ Bat of the power battery.

The fault state of the power battery is divided into three levels, wherein a level 0 indicates no fault, a level 1 indicates that some parameters deviate from normal values, attention is needed but operation is not affected, and a level 2 indicates that a fault occurs. The fault levels are level 0 and level 1, the fault state is considered normal, the fault state is level 2, and the fault state is considered fault. Therefore, if the fault level is 0 level or 1 level, the fault state value Alarm _ Bat of the power battery is assigned to 1, which indicates that the power battery is normal, and if the fault level is 2 level, the fault state value Alarm _ Bat of the power battery is assigned to 0, which indicates that the power battery is faulty.

Step 220, obtaining the state number FCs _ Hstate of the fuel cell system. FCs _ Hstate represents the total number of fuel cells in the fuel cell system that can supply power to the outside.

Specifically, referring to fig. 5, step 220 specifically includes:

step 221, the fault status of each fuel cell is identified separately.

The fault state of the fuel cell is divided into three levels, wherein 0 level represents no fault, 1 level represents that some parameters deviate from normal values and need attention but do not affect the operation, and 2 level represents that a fault occurs. The fault levels are level 0 and level 1, the fault state is considered normal, the fault state is level 2, and the fault state is considered fault. If the fault level of the fuel cell is level 0 or level 1, the fault state of the fuel cell is determined to be normal, and if the fault level of the fuel cell is level 2, the fault state of the fuel cell is determined to be fault.

Step 222, respectively counting the state reference number FCs _ Hstate _ i _ re of each branch according to the fault state of each fuel cell.

Wherein, FCs _ Hstate _ i _ re represents the number of fuel cells in the ith branch circuit whose fault state is normal. If 4 fuel cells are connected in series in the 2 nd branch, wherein the fault state of 3 fuel cells is normal, and the fault state of 1 fuel cell is fault, the state reference number FCs _ Hstate _2_ re of the 2 nd branch is 3.

In step 223, the state number FCs _ Hstate is determined according to the state reference number FCs _ Hstate _ i _ re of each branch.

After obtaining the state reference number FCs _ Hstate _ i _ re of each branch, judging whether a hydrogen storage system connected with the fuel cell system has a fault, dividing the fault state of the hydrogen storage system into three levels, wherein the level 0 indicates no fault, the level 1 indicates that some parameters deviate from normal values, attention needs to be paid, but operation is not influenced, and the level 2 indicates that the fault occurs. The fault levels are level 0 and level 1, the fault state is considered normal, the fault state is level 2, and the fault state is considered fault. And if the fault level of the hydrogen storage system is 0 level or 1 level, determining that the hydrogen storage system has no fault, and if the fault level of the hydrogen storage system is 2 levels, determining that the hydrogen storage system has a fault.

If the hydrogen storage system does not have a fault, further judging whether the DC/DC module connected with each branch circuit has a fault; assigning a state reference number FCs _ Hstate _ i _ re of a branch without the fault of the DC/DC module to a state target number FCs _ Hstate _ i of the branch, and setting the state target number FCs _ Hstate _ i of the branch with the fault of the DC/DC module to zero, wherein FCs _ Hstate _ i represents the number of fuel cells which can supply power to the outside in the ith branch; and obtaining the state number FCs _ Hstate according to the sum of the state target numbers FCs _ Hstate _ i of the branches.

Because the whole fuel cell system adopts a set of hydrogen storage system to supply hydrogen, if the hydrogen storage system fails, the whole fuel cell system cannot normally operate, namely cannot supply power to the outside, and at the moment, the state target number FCs _ Hstate _ i of each branch and the state number FCs _ Hstate of the fuel cell system are directly set to zero.

Taking fig. 2 as an example, in one specific embodiment of the above-mentioned steps 221-222, the fault states of the fuel cells are identified one by one, if the fault level of the fuel cell is not 2, the fuel cell is considered to be normal, and the fault state value FCX _ X _ OK is set to 1, otherwise 0 is set, the first X in FCX _ X _ OK is a branch label representing two branches connected in parallel, and takes the value of 1-2, and the second X is a fuel cell number representing 4 fuel cells connected in series, and takes the value of 1-4; then summing the fault state values FCX _ X _ OK of the branch fuel cells and assigning the sum to FCs _ Hstate _1_ re and FCs _ Hstate _2_ re respectively; judging whether the hydrogen storage system has a fault, if the hydrogen storage system has the fault, setting the state target numbers FCs _ Hstate _1 and FCs _ Hstate _2 which represent the number of the fuel cells with the branches capable of supplying power to the outside and the state number FCs _ Hstate of the fuel cell system to be 0; if the hydrogen storage system does not have a fault, further judging the fault state of the DC/DC module connected with each branch, if the DC/DC module of the branch has a fault (namely a 2-level fault level), setting the target number FCs _ Hstate _ i of the branch state to be 0, if the DC/DC modules of two branches do not have faults, respectively assigning FCs _ Hstate _1_ re and FCs _ Hstate _2_ re to FCs _ Hstate _1 and FCs _ Hstate _2, and summing FCs _ Hstate _1 and FCs _ Hstate _2 to obtain the state number FCs _ Hstate of the fuel cell system.

After obtaining the fault state value Alarm _ Bat of the power battery and the state number FCs _ Hstate of the fuel cell system, step 230 is executed to determine the main state value HBS _ state of the hybrid power system according to Alarm _ Bat and FCs _ Hstate.

The main state value HBS _ state represents the power supply state of the hybrid system at the current real-time, and as shown above, the hybrid system in the present embodiment includes 6 power supply states in total: (1) normally supplying power; (2) limp-hybrid power supply; (3) limp-single power battery powered; (4) limp-single fuel cell powered; (5) limp-single fuel cell failure power; (6) a hybrid system failure.

In step 230, the specific determination procedure of the main state value HBS _ state is as follows:

(1) normal power supply state HBS _ state is 0: and the power battery and the fuel battery system in the hybrid power system are normal and can provide power according to a normal energy distribution strategy.

When Alarm _ Bat indicates that the power battery is normal and FCs _ Hstate is equal to M, the main state value HBS _ state is assigned as a target value, wherein M is the total number of fuel batteries included in the fuel battery system, the target value corresponds to the normal power supply state of the hybrid power system, and the target value can be 0 for implementation.

(2) Limp-hybrid power state HBS _ state is 1: in this state, the power battery is normal, a part of the fuel battery faults exist in the fuel battery system, and at the moment, the hybrid power system supplies power in a hybrid power supply mode, and since the system comprises 8 fuel batteries, the system topology with HBS _ state equal to 1 comprises various situations, such as single branch fault, double branch fault, and the number of branch faults also has various combinations, the energy distribution strategies of the fuel battery system are different.

When Alarm _ Bat indicates that the power battery is normal and FCs _ Hstate belongs to [1, M-1], assigning the main state value HBS _ state to be a first numerical value, wherein the first numerical value corresponds to the hybrid power supply state of the hybrid power system; for ease of implementation, the first value may be 1.

(3) Limp-single power battery supply HBS _ state 2: in this state, the power battery is normal, the whole fuel cell system can not supply power normally, and the power battery can be adopted to supply power for the system independently.

When the Alarm _ Bat indicates that the power battery is normal and FCs _ Hstate is equal to 0, the main state value HBS _ state is assigned as a second value, the second value corresponds to the power supply state of a single power battery of the hybrid power system, and the second value can be 2 for implementation.

(4) Limp-single fuel cell powered HBS _ state 3: in this state, the power battery is in failure, each fuel battery in the whole fuel battery system is normal, and because no voltage stabilization source is arranged on the direct current bus, the DC/DC module connected with the fuel battery can be set to be in a voltage source working mode to output the power battery to the outside.

When Alarm _ Bat indicates that the power battery has a fault and FCs _ Hstate is equal to M, assigning the main state value HBS _ state to be a third value, wherein the third value corresponds to the power supply state of a single fuel battery of the hybrid power system; for ease of implementation, the third value may be 3.

(5) Limp-single fuel cell failure power HBS _ state 4: in the state, the power battery is in fault, partial fuel battery in the fuel battery system is in fault, and the hybrid power system can utilize the fuel battery in a normal state to supply power to the outside. Meanwhile, to meet the requirement of the lowest power supply (auxiliary load power supply) of the vehicle, when the FCs _ Hstate is not less than the preset base number, the HBS _ state is assigned to 4. Since the system topology includes 8 fuel cells and the HBS _ state 4 includes multiple situations, such as single branch failure, double branch failure, and multiple combinations of branch failure numbers, the local energy distribution strategy of the fuel cell system may be changed.

When Alarm _ Bat represents the power battery fault and FCs _ Hstate belongs to [ M ', M-1], assigning the main state value HBS _ state to be a fourth numerical value, wherein M' is the basic number of the fuel batteries meeting the lowest power supply requirement of the vehicle, and the fourth numerical value corresponds to the single-fuel-battery fault power supply state of the hybrid power system; for convenience of implementation, the fourth value may be 4, and the base number M' of fuel cells that meet the minimum power requirement of the vehicle may be 2.

(6) Hybrid system fault HBS _ state is 5: in this state, the power battery and the whole fuel cell system both have faults (or the fuel battery does not meet the minimum power supply requirement of the vehicle), the hybrid power system cannot output power to the outside, and the power supply needs to be shut down for troubleshooting.

When Alarm _ Bat indicates a power battery fault and FCs _ Hstate ∈ [0, M'), the main state value HBS _ state is assigned to a fifth value, which corresponds to a hybrid system fault state, and for convenience of implementation, the fifth value may be 5.

It should be noted that after the main state value HBS _ state is assigned, a high-voltage start instruction is waited, and a real-time main state value of the hybrid power system is determined in a loop before the high-voltage start instruction is not received, so as to ensure that the main state value is always in the current latest state before the high-voltage start.

After receiving the high-voltage start command, the ECU executes step 120, i.e., starts the corresponding battery in the hybrid system according to the main state value.

In step 120, the start strategy of the hybrid system is divided into the following cases according to the main state values:

1) when the HBS _ state is equal to a target value, sequentially starting one of the branches of the power battery and the fuel cell system and the DC/DC module, and setting the DC/DC module to be in a current source working mode;

2) when the HBS _ state is equal to a first value, sequentially starting the power battery, one branch of the fuel cell system and the DC/DC module, cutting off a fault fuel cell in the fuel cell system from the fuel cell system through a bypass isolating switch, and setting the DC/DC module to be in a current source working mode;

in the above cases 1) and 2), the power supply state of the hybrid power system is a normal power supply state or a hybrid power supply state, and at this time, to save energy, only one of the branches is started, specifically, one of the two branches in parallel connection with the fuel cell system, which has a smaller number of normal fuel cells, is started, and if the two branches have the same number, the first branch is started.

3) When the HBS _ state is equal to the second value, starting the power battery;

4) when the HBS _ state is equal to the third value, the fuel cell system and the DC/DC module are started up in sequence, and the DC/DC module is set to a voltage source operation mode;

5) when the HBS _ state is equal to the fourth value, the fuel cell system and the DC/DC module are started up in sequence, a faulty fuel cell in the fuel cell system is removed from the fuel cell system by means of the bypass disconnector, and the DC/DC module is set to the voltage source mode of operation.

In the above cases 4) and 5), the power cell in the hybrid system fails and can only be powered by the fuel cell system, when all normal fuel cells are activated as fully as possible.

When the HBS _ state is equal to the fifth value, the power supply state of the hybrid system is a system failure state, the hybrid system cannot output to the outside, and all batteries are not started.

After receiving the power demand command from the vehicle controller VCU, the ECU performs step 130, i.e. performs energy management on the battery with the hybrid system activated according to the main state value and the vehicle demanded power.

In step 130, the energy management strategy of the hybrid system is divided into the following cases according to the difference of the main state values:

1) when the HBS _ state is equal to the target value or the first value, performing global power distribution on the fuel cell system according to the vehicle required power to obtain the target output power of the fuel cell system; the power output of the fuel cell system is controlled in accordance with the target output power.

Wherein globally allocating power to the fuel cell system according to the power demand of the vehicle comprises:

i) when the state of charge SOC of the power battery is greater than SOCmax (SOC control range upper limit):

if the required power of the vehicle is larger than the sum of the maximum available power of the power battery and the maximum available power of the fuel cell system, the maximum available power of the fuel cell system is used as the target output power (the fuel cell is output at the maximum power, and the power battery automatically discharges at the maximum discharge capacity), and meanwhile, a system power shortage prompt is generated. The maximum power supply power of the power battery is determined by the output voltage of the power battery and the maximum allowable discharge current, and the maximum power supply power of the fuel cell system is determined by the number of normal fuel cells in the system and the maximum power of a single fuel cell.

Otherwise (if the power required by the vehicle is not larger than the sum of the maximum available power of the power battery and the maximum available power of the fuel cell system), the minimum available power of the fuel cell system is taken as the target output power (so that the fuel cell outputs at the minimum power, and other power requirements are met by the power battery).

ii) when SOCmin (SOC control range lower limit) < SOC ≦ SOCmax:

and if the required power of the vehicle is larger than the sum of the maximum available electric power of the power battery and the maximum available electric power of the fuel cell system, taking the maximum available electric power of the fuel cell system as the target output power, and generating a system power shortage prompt.

And if the required power of the vehicle is between the maximum available electric power of the fuel cell system and the maximum available electric power of the hybrid system, determining the target output power according to the size relation between the SOC of the power battery and the SOC control range middle reference value SOCpower, wherein SOCmin < SOCpower < SOCmax. The maximum available electric power of the hybrid power system is the sum of the maximum available electric power of the power battery and the maximum available electric power of the fuel battery.

In order to prevent the SOC of the power battery from decreasing to SOCmin, an intermediate reference value socbrown is set, and when the vehicle required power is in the above range, the range of the SOC is further determined, which includes the following two sub-cases:

SOCmin < SOC ≦ SOCwindow: taking the maximum available power of a fuel cell system as target output power, and at the moment, enabling the fuel cell to output with the maximum power, and charging the power cell as soon as possible while ensuring to meet the power required by the vehicle, so that the SOC of the power cell cannot be reduced to SOCmin;

SOCdown < SOC ≦ SOCmax: taking the vehicle required power as the target output power; on the premise that the power required by the vehicle is between the maximum available power of the fuel cell system and the maximum available power of the hybrid power system, the fuel cell is enabled to meet the power requirement of the vehicle, and the power cell does not output the power.

If the vehicle required power is not in the above two ranges, the minimum available electric power of the fuel cell system is taken as the target output power.

iii) when SOC is less than or equal to SOCmin:

at this time, no matter what the vehicle needs power, the fuel cell system outputs the maximum power, namely the maximum available electric power of the fuel cell system is taken as the target output power, and meanwhile, the power reduction prompt is generated and sent to the vehicle controller.

After obtaining the target output power of the fuel cell system, the power output of the fuel cell system is controlled according to the target output power, referring to fig. 6, the specific process includes:

and 310, performing local power distribution between two branches of the fuel cell system connected in parallel according to the target output power to obtain a power distribution value of each branch.

In one embodiment, the target output power is divided by the total number of the fuel cells in the normal state in the two branches to obtain a power output value of a single normal fuel cell; and multiplying the power output value of the single normal fuel cell by the number of the fuel cells in the normal state in each branch to obtain the power distribution value of each branch.

Step 320, determining a power separation point according to the number of the normal fuel cells of each branch; when the target output power is less than or equal to the power corresponding to the power split point, skipping to execute step 330; and when the target output power is larger than the power corresponding to the power separation point, skipping to execute the step 340.

In step 320, the power split point result calculated off-line is invoked based on the number of normal fuel cells per branch. The power separation point is obtained by determining a total external power-battery working efficiency curve (hereinafter referred to as a power-efficiency curve) of each branch according to the number of normal fuel cells of each branch and taking the intersection point of the power-efficiency curves of the two branches. The power separation point is the intersection point of the power-efficiency curves of the two branches, and as the number of the normal fuel cells of each branch can be changed between 1 and 4, the power-efficiency curve of each branch has 4 different conditions, so that various combinations exist, for example, when the number of the normal fuel cells of the first branch is 2, the number of the normal fuel cells of the second branch may be 1, 2, 3 or 4, namely, 4 different conditions exist, and the power separation points in each condition are different. The power separation point is obtained by off-line calculation according to factory parameters of the fuel cells, and the power separation point results of the two branches under the condition of different normal fuel cell numbers are preset in a control program of the ECU so as to be directly called.

And 330, controlling the fuel cell in the currently started branch to operate according to the power distribution value corresponding to the branch.

And step 340, starting the other branch of the two branches, and controlling the fuel cells in the two branches to operate according to the power distribution values corresponding to the respective branches.

It should be noted that, because the fuel cell system includes a plurality of fuel cells, and the power supply state of the hybrid power system changes after a single or a plurality of fuel cell systems fail, the original optimization strategy is no longer applicable. Therefore, the method is required to ensure that the fuel cell system can ensure the optimal energy distribution strategy in any state, and the efficiency of the hybrid power system is improved. The method takes the number of the fuel cells in the normal state of each of the two parallel branches as an input condition, calls an offline calculation result in real time to obtain a power separation point, starts only one parallel branch when the required power (namely target output power) of the fuel cell system is less than or equal to the power corresponding to the power separation point, and starts two branches when the required power is greater than the power corresponding to the power separation point, so that the fuel cell system is ensured to operate according to the high-efficiency intervals of two power-efficiency curves of the two branches in any fault state.

2) When HBS _ state equals the second value, the ECU sends a limp-home alert to the vehicle controller VCU along with the maximum allowed discharge current of the power battery, from which the VCU updates the vehicle demanded power after receiving the limp-home alert.

Since the power battery has been started in step 120, the power battery is always consumed after starting, the SOC thereof continuously decreases, and when the SOC decreases below the warning value SOC _ low _ alarm1, the VCU needs to cut off the vehicle traction and only send the auxiliary load demand power; and if the SOC is continuously reduced to be lower than the warning value SOC _ low _ alarm2, the ECU closes the power battery through the energy control unit, the power battery is shut down, and the hybrid power system stops supplying power to the outside. Wherein SOC _ low _ alarm1> SOC _ low _ alarm 2.

3) When the HBS _ state is equal to the third or fourth value, the target output power is divided by the total number of fuel cells in a normal state in the two branches to obtain a power output value of a single normal fuel cell; multiplying the power output value of a single normal fuel cell by the number of the fuel cells in the normal state in each branch to obtain the power distribution value of each branch; and setting the current value (the ratio of power to voltage) of each branch according to the power distribution value of each branch so as to control the fuel cell in each branch to output power according to the corresponding power distribution value. At this time, the DC/DC module outputs in a voltage source mode.

In the embodiment, energy management of the hybrid power system after the rail vehicle is started can be realized through the above embodiment, and the ECU shuts down all started batteries in the hybrid power system after receiving the stop command.

Specifically, because the units for starting the hybrid power system in different main states are not completely the same, the ECU respectively judges the states of the units in the hybrid power system after receiving the stop instruction, and if the units are in the running state, sends a close instruction to the controller connected to the units, and the controller closes the units after receiving the close instruction. After the fuel cell system is closed, the controllers of all units enter a power-on self-test state, and the ECU waits for a high-voltage starting instruction or the system is powered off.

The invention can realize the power supply application of 30kW low-power fuel cells for automobiles on the rail vehicles to replace high-power fuel cells to supply power, thereby reducing the use cost and improving the power supply reliability of a hybrid power system. The inventor applies the scheme to a new energy third-generation fuel cell system of medium-sized vehicle Tangshan company to successfully realize the energy distribution management of mixed power supply of 8 low-power fuel cells.

To sum up, the invention provides a hybrid power system with multiple fuel cells and an energy management method thereof, and the hybrid power system has the following technical effects:

(1) greatly reduce the use cost of the fuel cell system of the rail vehicle: the power requirement of the rail vehicle is much larger than that of the automobile, the conventional fuel cell for the rail vehicle generally needs to be customized and developed into a high-power fuel cell, and the customized development cost is multiplied due to the high requirements of the high-power fuel cell on the pressure, flow, distribution uniformity and the like of air, hydrogen and the like. Compared with the prior art, the low-power fuel cell has low use cost, and the energy management method provided by the invention can replace the customized high-power fuel cell scheme, so that the use cost of a user is greatly reduced.

(2) The power supply reliability of the hybrid power system is effectively improved: the energy management method provided by the invention adopts the parallel branch and the series branch with the bypass isolating switch to form a series-parallel combined complex fuel cell system, and has high controllability while ensuring higher efficiency and volume and weight reduction of the system. Compared with the situation that the high-power fuel cell fails to supply power, when one or more fuel cells fail, the failed fuel cell can be cut off through the bypass isolating switch, other fuel cells in the normal state can still supply power, the shutdown of the hybrid power system cannot be caused, and the power supply reliability of the hybrid power system is greatly improved.

(3) The system efficiency can be optimized under any fault state of the fuel cell system: the energy management method provided by the invention takes the number of the fuel cells of the two parallel branches in a normal state as an input condition, and calls the offline calculation result in real time to obtain the intersection point of the power-efficiency curves of the parallel branches under any fault state of the fuel cell system, namely the power separation point, so that the fuel cell system containing multiple fuel cells always operates in a high-efficiency interval before and after the intersection point of the two power-efficiency curves, and the economy of the power supply system of the multiple fuel cells is improved.

Based on the same inventive concept, the embodiment of the present application provides an energy management device for a hybrid power system with multiple fuel cells, wherein the hybrid power system comprises: a power battery connected to the DC bus; the fuel cell system comprises at least two parallel branches, wherein at least two fuel cells are connected in series in each branch, each branch is connected to the direct current bus through a DC/DC module, two ends of each fuel cell are connected in parallel with a bypass isolating switch, and the bypass isolating switch is used for connecting the fuel cell into the fuel cell system to supply power or cutting the fuel cell from the fuel cell system. The specific structure of the hybrid system can be referred to fig. 2 and its description.

Referring to fig. 7, the apparatus includes: a master status determination module 410 and an energy management module 420. The main state determining module 410 is configured to obtain a current main state value of the hybrid power system, where the main state value represents a power supply state of the hybrid power system at a current moment, and the power supply state is determined by a power supply topology structure formed by a battery that can supply power to the outside in the hybrid power system; the energy management module 420 is configured to start a corresponding battery in the hybrid power system according to a preset starting strategy corresponding to the main state value after receiving a high-voltage starting instruction, and perform energy management on the started battery of the hybrid power system according to the main state value and a vehicle required power.

It is understood that the implementation principle and the resulting technical effect of the energy management device of a multi-fuel cell hybrid system in this embodiment have been described in the foregoing method embodiments, and for the sake of brief description, for the sake of brevity, the corresponding descriptions in the energy management method in the foregoing embodiments may be referred to for the non-mentioned parts of the energy management device of a multi-fuel cell hybrid system, and are not repeated herein.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.