CN112977180B - Average value-based vehicle-mounted fuel cell energy management method - Google Patents

Abstract

The invention discloses a vehicle-mounted fuel cell energy tube based on an average valueThe method is that the first N minutes of the fuel cell system is set as the fixed power P₀And outputting, and then taking the average value of the total power required by the fuel cell system in the whole vehicle in the previous period t as the power output. Therefore, the output power of the fuel cell system gradually approaches to the average value of the total power required by the whole vehicle at the front-stage time t, the SOC of the power cell can be controlled to operate in a small-range efficient interval, the service life and the use efficiency of the power cell are improved, the output power of the fuel cell system changes slowly, the change interval is relatively small, the number of starting and stopping times of the fuel cell system is reduced, and the service life of the fuel cell is further prolonged. By reasonably distributing the power of the fuel cell system and the power of the power cell, the service life and the service efficiency of the power cell can be improved on the premise of not influencing the service life of the fuel cell system.

Description

Average value-based vehicle-mounted fuel cell energy management method

Technical Field

The invention relates to a vehicle-mounted fuel cell energy management method based on an average value.

Background

For a fuel cell vehicle, due to the defects of the fuel cell stack, such as soft output characteristics, slow output response, and the like, the fuel cell stack cannot supply power required by the whole vehicle in time, and has the disadvantages of high price, short service life, and the like, the fuel cell stack cannot be independently and directly used as an energy source, so that an auxiliary power supply is required to be matched with the fuel cell stack for use. The power battery can solve the problem of slow response of the fuel cell stack, and meanwhile, the power battery can also provide electric energy required by the start of the fuel cell stack, such as power supply of high-voltage components such as an air compressor assembly, a water pump and the like, and the components need to be started to operate before the fuel cell stack starts to generate electricity; when the vehicle accelerates or climbs a slope, peak power is needed for a short time, and then the power battery can assist the fuel cell stack to provide energy; in addition, when the vehicle brakes, the power battery can be used for absorbing braking feedback energy, and energy consumption is reduced. Thus, the power battery improves the power performance and the economical efficiency of the fuel cell vehicle. However, the energy management strategy for the fuel cell stack and the power battery in the whole vehicle factory at present mainly protects the service life of the fuel cell stack, and only the fuel cell stack is enabled to work at a plurality of specific power points, and the change and fluctuation of the SOC of the power battery are large, so that the service life attenuation of the power battery is accelerated.

The existing fuel cell automobile energy management method generally segments the SOC of the power battery to charge the power battery with different powers through the fuel cell stack. The SOC variation interval of the power battery is large, so that the load change of the fuel cell stack is frequent, and the load change amplitude is relatively large. Not only the service life of the fuel cell stack, but also the service life of the power cell.

Disclosure of Invention

The invention aims to provide a vehicle-mounted fuel cell energy management method based on an average value, which considers the service life of a power cell on the premise of ensuring the service life of a fuel cell system, so that the SOC fluctuation of the power cell is stabilized in a smaller range, and the service life and the service efficiency of the power cell are improved; meanwhile, the number of start-stop times of the fuel cell system is reduced, and the service life of the fuel cell system is further prolonged.

In order to achieve the purpose, the invention adopts the technical scheme that:

an average-based on-board fuel cell energy management method, comprising the steps of:

s1: before starting the fuel cell system, the power cell is started, and whether SOC (t) is less than SOC is judged_InIf true, then P_FC(t) with P₀Run for N minutes, then execute as per S2; otherwise the fuel cell system is not operated and then executed as per S1;

s2: judgment of P_FC(t) whether or not less than P_V(t), if true, proceed according to S3; otherwise, execution is according to S8;

s3: judgment of P_V(t) whether or not greater than P_maxIf yes, executing according to S4, otherwise executing according to S5;

s4: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise P_FC(t +1) is P_maxThen according to S2;

s5: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, execution is according to S6;

s6: determining whether SOC (t) is less than SOC_{Lower part}If true, then P_FC(t +1) is P_maxThen according to S7; otherwise P_FC(t +1) by P_FC(t) plus P₁Run, then execute as per S2;

s7: determining whether SOC (t) is greater than SOC_InIf true, proceed according to S2; otherwise P_FC(t +1) is P_maxThen according to S7;

s8: judgment of P_V(t) whether or not less than P_minIf true, proceed according to S9; otherwise, execution is according to S10;

s9: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise P_FC(t +1) is P_minThen according to S2;

s10: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, execution is according to S11;

s11: determining whether SOC (t) is less than SOC_{Lower part}If true, then P_FC(t +1) continuing with P_FC(t) run, then execute as per S2; otherwise P_FC(t +1) by P_FC(t) subtracting P₂Run, then execute as per S2;

wherein:

P_FC(t) is the current output power, kw, of the fuel cell system;

P_FC(t +1) is the next time output power, kw, of the fuel cell system;

P₀initial operating power, kw, for the fuel cell system;

P_minis the minimum operating power, kw, of the fuel cell system;

P_maxis a stand forThe maximum operating power, kw, of the fuel cell system;

P_V(t) is the average real-time total power requirement kw of the whole vehicle within t minutes before the current time;

SOC (t) is the current state of charge,%, of the power battery;

SOC_{on the upper part}The upper limit value,%, of the state of charge of the power battery;

SOC_inThe intermediate value of the state of charge of the power battery is percent;

SOC_{lower part}The lower limit value,%, of the state of charge of the power battery;

P₁loading the fuel cell system with power, kw;

P₂derating power, kw, for the fuel cell system.

Preferably, in S1-S11, when the two values compared with each other are equal, execution is performed according to an established condition or an unsatisfied condition, respectively.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the invention relates to a vehicle-mounted fuel cell energy management method based on an average value, which enables a fuel cell system to use fixed power P for the first N minutes₀And outputting, and then taking the average value of the total power required by the fuel cell system in the whole vehicle in the previous period t as the power output. Therefore, the output power of the fuel cell system gradually approaches to the average value of the total power required by the whole vehicle at the front-stage time t, the SOC of the power cell can be controlled to operate in a small-range efficient interval, the service life and the use efficiency of the power cell are improved, the output power of the fuel cell system changes slowly, the change interval is relatively small, the number of starting and stopping times of the fuel cell system is reduced, and the service life of the fuel cell is further prolonged. By reasonably distributing the power of the fuel cell system and the power of the power cell, the service life and the service efficiency of the power cell can be improved on the premise of not influencing the service life of the fuel cell system.

Drawings

FIG. 1 is a flow chart illustrating a method for controlling the power of a vehicle-mounted fuel cell according to an embodiment of the present invention;

FIG. 2 is a conventional method for controlling the power of a bus fuel cell;

FIG. 3 is a schematic diagram of a power battery SOC variation curve obtained by performing fuel cell power control on a bus in Table 1 by using a conventional bus fuel cell power control method;

FIG. 4 is a schematic diagram of a power change curve of a fuel cell system obtained by performing fuel cell power control on a bus in Table 1 by using a conventional bus fuel cell power control method;

fig. 5 is a schematic diagram of a power battery SOC variation curve obtained by performing fuel battery power control on a bus in table 1 by the bus fuel battery power control method in the embodiment of the invention;

fig. 6 is a schematic diagram of a power change curve of a fuel cell system obtained by performing fuel cell power control on a bus in table 1 by using the bus fuel cell power control method in the embodiment of the invention.

Detailed Description

The technical solution of the present invention is further explained below with reference to the specific embodiments and the accompanying drawings.

Referring to fig. 1, the present embodiment provides an average-value-based on-vehicle fuel cell energy management method, including the steps of:

s1: before starting the fuel cell system, the power cell is started, and whether the current state of charge SOC (t) of the power cell is smaller than the intermediate value SOC of the state of charge of the power cell is judged_InIf yes, the current output power P of the fuel cell system_FC(t) at the initial operating power P of the fuel cell system₀Run for N minutes, then execute as per S2; otherwise, the fuel cell system is not operated and then executed as per S1.

When the fuel cell system is started for the first time, the power cell is allowed to start when the current state of charge (SOC) (t) is lower than a certain value so as to avoid the situation that the SOC (t) is too high and reaches the upper limit value SOC of the power cell state of charge in a short time_{On the upper part}Resulting in a shorter time to shutdown after the start-up of the fuel cell system, an increase in the number of shutdowns, and a reduction in the life of the fuel cell.

: judgmentCurrent output power P of fuel cell system_FC(t) whether the total power P required by the whole vehicle in real time in t minutes before the current time is less than the average real-time total power P_V(t), if true, proceed according to S3; otherwise, execution is as per S8.

Current output power P of fuel cell system_FC(t) is more than the average real-time total power P required by the whole vehicle in t minutes before the current time_VAnd (t), reducing the power of the fuel cell system, so that the power of the fuel cell system gradually approaches the average real-time total power demand of the whole vehicle.

: judging the average real-time total power P required by the whole vehicle within t minutes before the current time_V(t) whether or not it is greater than the maximum operating power P of the fuel cell system_maxIf so, execution is as per S4, otherwise execution is as per S5.

At this time, whether the fuel cell system is loaded or not needs to be considered, so that the average real-time total power P required by the whole vehicle in t minutes before the current time needs to be judged_V(t) whether or not it is greater than the maximum operating power P of the fuel cell system_max。

: judging whether the current state of charge (SOC) (t) of the power battery is greater than the upper limit value SOC of the state of charge of the power battery_{On the upper part}If yes, the fuel cell system outputs power P at the next time_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, the fuel cell system outputs power P at the next time_FC(t +1) is the maximum operating power P of the fuel cell system_maxAnd then executed as by S2.

The fuel cell system power cannot exceed its maximum value, and as long as SOC (t) is greater than SOC_{On the upper part}The fuel cell system needs to be stopped.

: judging whether the current state of charge (SOC) (t) of the power battery is greater than the upper limit value SOC of the state of charge of the power battery_{On the upper part}If yes, the fuel cell system outputs power P at the next time_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, execution is as per S6.

The power of the fuel cell system is smaller than the maximum value at the stage, and meanwhile, the SOC (t) is larger than the SOC_{On the upper part}Fuel cell systemThe system needs to stop working, otherwise, whether loading or not needs to be executed.

: judging whether the current state of charge (SOC) (t) of the power battery is smaller than the lower limit value SOC of the state of charge of the power battery_{Lower part}If yes, the fuel cell system outputs power P at the next time_FC(t +1) is the maximum operating power P of the fuel cell system_maxThen according to S7; otherwise, the fuel cell system outputs power P at the next time_FC(t +1) at the present output power P of the fuel cell system_FC(t) plus Fuel cell System Loading Power P₁The operation is then performed as per S2.

When SOC (t) is less than SOC_{Lower part}Loading is required, and in order to quickly return to the power cell high efficiency region, the fuel cell system is operated at the maximum operating power P_maxAnd rapidly charging the power battery.

: judging whether the current state of charge (SOC) (t) of the power battery is greater than the intermediate value SOC of the state of charge of the power battery_InIf true, proceed according to S2; otherwise, the fuel cell system outputs power P at the next time_FC(t +1) is the maximum operating power P of the fuel cell system_maxAnd then executed as by S7.

The stage can lead the current state of charge SOC (t) of the power battery to quickly return to the middle value SOC of the state of charge of the power battery_In。

: judging the average real-time total power P required by the whole vehicle within t minutes before the current time_V(t) whether or not it is less than the minimum operating power P of the fuel cell system_minIf true, proceed according to S9; otherwise, execution is as per S10.

At this time, whether the fuel cell is unloaded or not needs to be considered, so that the average real-time total power P required by the whole vehicle in t minutes before the current time needs to be judged_V(t) whether or not it is less than the minimum operating power P of the fuel cell system_min。

: judging whether the current state of charge (SOC) (t) of the power battery is greater than the upper limit value SOC of the state of charge of the power battery_{On the upper part}If yes, the fuel cell system outputs power P at the next time_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise the fuel cell systemOutput power P at next time_FC(t +1) is the minimum operating power P of the fuel cell system_minAnd then executed as by S2.

The fuel cell system power cannot be less than its minimum value, and as long as SOC (t) is greater than SOC_{On the upper part}The fuel cell system needs to be stopped.

: judging whether the current state of charge (SOC) (t) of the power battery is greater than the upper limit value SOC of the state of charge of the power battery_{On the upper part}If yes, the fuel cell system outputs power P at the next time_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, execution is as per S11.

The power of the fuel cell system is larger than the minimum value at the stage, as long as the SOC (t) is larger than the SOC_{On the upper part}The fuel cell system needs to be stopped, otherwise it needs to be performed whether to perform load shedding.

: judging whether the current state of charge (SOC) (t) of the power battery is smaller than the lower limit value SOC of the state of charge of the power battery_{Lower part}If yes, the fuel cell system outputs power P at the next time_FC(t +1) continuing with the current output power P of the fuel cell system_FC(t) run, then execute as per S2; otherwise, the fuel cell system outputs power P at the next time_FC(t +1) at the present output power P of the fuel cell system_FC(t) subtracting the fuel cell system turndown power P₂The operation is then performed as per S2.

When SOC (t) is less than SOC_{Lower part}In order to return to the high-efficiency region of the power battery, the power of the fuel cell system cannot be unloaded and should be kept unchanged, and continuous charging is realized.

Wherein:

P_FC(t) is the current output power of the fuel cell system, and the unit is kw;

P_FC(t +1) is the output power of the fuel cell system at the next time, and the unit is kw;

P₀is the initial operating power of the fuel cell system, and the unit is kw;

P_minthe minimum operating power of the fuel cell system is represented by kw;

P_maxthe maximum operation power of the fuel cell system is represented by kw;

P_V(t) is the average real-time total power required by the whole vehicle within t minutes before the current time, and the unit is kw;

SOC (t) is the current state of charge,%;

SOC_{on the upper part}The upper limit value,%, of the state of charge of the power battery;

SOC_inThe intermediate value of the charge state of the power battery is percent;

SOC_{lower part}The lower limit value,%, of the state of charge of the power battery;

P₁loading power for the fuel cell system in kw;

P₂the unit is kw for the load shedding power of the fuel cell system.

Here, the determination of the current state of charge soc (t) of the power battery is provided by the power battery BMS. The power battery BMS belongs to the prior art and is not described in detail herein.

In S1 to S11, when the two values compared with each other are equal, the execution is performed in accordance with the satisfied condition or the non-satisfied condition, respectively.

Taking S2 as an example, the current output power P of the fuel cell system_FC(t) is equal to the average real-time total power P required by the whole vehicle within t minutes before the current time_V(t) the process proceeds according to S3, or according to S8, either of which is performed.

The following simulation analysis is performed according to the daily running condition of a certain city bus, and the running parameters are shown in the following table 1.

TABLE 1 daily operating parameters of a city bus

Referring to FIG. 2, a conventional method for controlling the power of a bus fuel cell system, fuel cell system power P_FC(t) varies with the power cell SOC. The start-up power of the fuel cell system was 22 kw; when the SOC of the power battery is charged to 75%, the fuel cell system stops working, and then the power battery is chargedThe fuel cell system is started up until the SOC drops below 50%.

Referring to fig. 2, there is a hysteresis interval between power change points of the fuel cell system, which include 30%, 45%, 50%, 65%. Taking the power change points 30% and 45% as an example, when the SOC is changed between 30% and 45%, the power is hysteretic between the two points of 36kw and 54 kw. The hysteresis principle belongs to the prior art and is not described in detail here.

In the method of the embodiment, the fuel cell system is started at a constant P N =5min before the stack is started₀Power output of =20 kw; and after the 5min, taking the average real-time total power required by the whole vehicle as the output power of the fuel cell system. Meanwhile, the values of other parameters are as follows:

P_mintaking 8 kw; p_maxTaking 54 kw; SOC_{On the upper part}Taking 75 percent; SOC_InTaking 65 percent; SOC_{Lower part}Taking 30 percent; p₁Taking 20 w; p₂Take 30 w.

The two methods are used for carrying out simulation comparative analysis on the operation of the bus in the table 1, and the simulation time step length is 0.1 s.

Referring to fig. 3-6, for simulation results:

fig. 3-4 are graphs of power battery SOC and fuel cell system power variation respectively simulated by the existing bus fuel cell power control method, with time on the horizontal axis and 0.1S unit. As can be seen, the SOC varies by a large amount, one of which exceeds 75%, causing the fuel cell system to shut down until the SOC drops to 50% and the fuel cell system is not started. The fuel cell system power varies widely. The change interval of the SOC of the power battery is large, so that the service life of the power battery is shortened rapidly; the fuel cell system has a large number of start-stop times, and the service life of the fuel cell system is shortened in an accelerated manner.

Fig. 5 to 6 are graphs of simulated power cell SOC and fuel cell system power variation of the vehicle-mounted fuel cell power control method of the present embodiment, respectively, with time on the horizontal axis and 0.1S as a unit. As can be seen from the figure, the SOC variation range is small, the power variation range of the fuel cell system is relatively small, the power is more stable as the time is longer, and the problem that the SOC of the power cell exceeds 75 percent and the fuel cell system is stopped does not occur. The service life of the power battery is prolonged, and the service life of the fuel battery system is also prolonged.

The above-mentioned embodiments are merely illustrative of the technical idea and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered in the scope of the present invention.

Claims (2)

1. An average-based vehicle-mounted fuel cell energy management method, characterized by: the method comprises the following steps:

s1: before starting the fuel cell system, the power cell is started, and whether SOC (t) is less than SOC is judged_InIf true, then P_FC(t) with P₀Run for N minutes, then execute as per S2; otherwise the fuel cell system is not operated and then executed as per S1;

s2: judgment of P_FC(t) whether or not less than P_V(t), if true, proceed according to S3; otherwise, execution is according to S8;

s3: judgment of P_V(t) whether or not greater than P_maxIf yes, executing according to S4, otherwise executing according to S5;

s4: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise P_FC(t +1) is P_maxThen according to S2;

s5: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, execution is according to S6;

s6: determining whether SOC (t) is less than SOC_{Lower part}If true, then P_FC(t +1) is P_maxThen according to S7; otherwise P_FC(t +1) by P_FC(t) plus P₁Run, then execute as per S2;

s7: determining whether SOC (t) is greater than SOC_InIf true, proceed according to S2; otherwise P_FC(t +1) is P_maxThen according to S7;

s8: judgment of P_V(t) whether or not less than P_minIf true, proceed according to S9; otherwise, execution is according to S10;

s9: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise P_FC(t +1) is P_minThen according to S2;

s10: determining whether SOC (t) is greater than SOC_{On the upper part}If true, then P_FC(t +1) is 0, the fuel cell system stops operating, and then execution is performed as per S1; otherwise, execution is according to S11;

s11: determining whether SOC (t) is less than SOC_{Lower part}If true, then P_FC(t +1) continuing with P_FC(t) run, then execute as per S2; otherwise P_FC(t +1) by P_FC(t) subtracting P₂Run, then execute as per S2;

wherein:

P_FC(t) is the current output power, kw, of the fuel cell system;

P_FC(t +1) is the next time output power, kw, of the fuel cell system;

P₀initial operating power, kw, for the fuel cell system;

P_minis the minimum operating power, kw, of the fuel cell system;

P_maxis the maximum operating power, kw, of the fuel cell system;

P_V(t) is the average real-time total power requirement kw of the whole vehicle within t minutes before the current time;

SOC (t) is the current state of charge,%, of the power battery;

SOC_{on the upper part}The upper limit value,%, of the state of charge of the power battery;

SOC_inThe intermediate value of the state of charge of the power battery is percent;

SOC_{lower part}The lower limit value,%, of the state of charge of the power battery;

P₁loading the fuel cell system with power, kw;

P₂derating power, kw, for the fuel cell system.

2. The average-based on-vehicle fuel cell energy management method according to claim 1, characterized in that: in S1 to S11, when the two values compared with each other are equal, the execution is performed in accordance with the satisfied condition or the non-satisfied condition, respectively.

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