CN110758180B - An Energy Distribution Method for Hybrid Power System Considering Fuel Cell Start-Stop Strategy - Google Patents

Abstract

The invention provides a composite power supply system energy distribution method considering a fuel cell start-stop strategy, belongs to the field of fuel cells, and has the advantages of reducing the start-stop times of a fuel cell system, improving the system efficiency and prolonging the service life of a power supply. The invention comprises an upper layer control and a lower layer control; the upper control is start-stop control of the fuel cell: collecting electric quantity data of a storage battery and load current of an automobile, and determining that the fuel cell is started and shut down according to the current opening and closing state of the fuel cell and the electric quantity data of the storage battery; the lower control is a control of energy distribution: and according to the electric quantity of the storage battery, the electric quantity of the super capacitor and the current demand of the load, which are acquired by the data acquisition module, the energy is distributed to the fuel cell module and the super capacitor module.

Description

An Energy Distribution Method for Hybrid Power System Considering Fuel Cell Start-Stop Strategy

technical field

The invention belongs to the field of fuel cells, and in particular relates to an energy distribution method of a composite power supply system considering a fuel cell start-stop strategy.

Background technique

In recent years, fuel cells have been widely used in the vehicle field due to their advantages of high efficiency and no pollution. Considering the shortcoming of the fuel cell's slow dynamic response, the fuel cell and other energy storage sources such as batteries and supercapacitors are used as composite energy sources. Supercapacitors have the advantages of high power density, and batteries have the advantages of high energy density. Therefore, it is especially important to design a fuel cell composite power system with high efficiency, long life and good reliability to give full play to the respective advantages of these power sources.

The current fuel composite power system generally only includes two power supplies, especially in the energy management strategy, the damage caused by frequent switching to the fuel cell system is not considered, and the start-stop control of the fuel cell is not considered while the energy distribution of the composite power supply is carried out. The design of the energy management controller cannot fully meet the characteristics of fuel cells and other energy storage sources, which leads to the disadvantages of low efficiency of the composite power system and damage to the life of the battery system.

Contents of the invention

The invention provides an energy distribution method of a composite power supply system considering the start-stop strategy of the fuel cell, which can reduce the number of times of start-stop of the fuel cell system, improve the working efficiency of the composite power supply system, and prolong the service life of the battery.

To achieve the above object, the present invention adopts the following technical solutions:

An energy distribution method for a composite power system considering a fuel cell start-stop strategy, the composite power system includes: a fuel cell module, a supercapacitor module, a storage battery module, a data acquisition module, and a composite power controller; the composite power controller and The data acquisition module is connected, and the data acquisition module is respectively connected with the fuel cell module, the battery module, and the super capacitor module; the battery module is directly connected with the load module; the fuel cell module is connected with a one-way DC-DC control The unidirectional DC-DC controller is connected to the load and the composite power controller respectively; the supercapacitor module is connected to a bidirectional DC-DC controller, and the bidirectional DC-DC controller is respectively connected to the load and the The composite power controller is connected. The composite power controller includes two parts: the upper layer and the lower layer control. The upper layer is the start-stop strategy of the fuel cell, and the lower layer is the distribution of energy. According to the power of the battery and the power of the super capacitor collected by the data acquisition module And the current demand of the load, the energy distribution of the fuel cell module and the super capacitor module;

The data acquisition module includes a load current and voltage acquisition module, a fuel cell current acquisition module, a super capacitor power acquisition module, and a battery power acquisition module; after the load current acquisition module is connected in series with the load in the car, it is connected to the composite power controller After the load voltage acquisition module is connected in parallel with the load, it is connected with the composite power controller; the fuel cell power acquisition module is connected with the fuel cell module and the composite power controller respectively; the supercapacitor power acquisition module is respectively connected with the supercapacitor module It is connected with the composite power controller; the battery power collection module is connected with the supercapacitor module and the composite power controller respectively;

The energy distribution method includes upper-level control and lower-level control; the upper-level control is the start-stop control of the fuel cell, and the control method is to collect the electric quantity data of the storage battery and the load current of the vehicle, according to the current on-off state of the fuel cell and the current state of the storage battery. power data, to determine fuel cell start-up and shutdown operations,

Specific steps are as follows:

(1) Judging the current state of the car according to the positive and negative of the collected car load current, if the current is negative, the car is in the braking state, the reference current value of the fuel cell is 0, and if the current is positive, the car is in the driving state;

(2) According to the collected power data of the battery and the current switch state of the fuel cell, turn on or shut down the fuel cell; if the fuel cell is in the off state, when the power of the battery is less than its lower limit threshold, then the minimum shutdown is not considered Time toff constraints, the fuel cell is turned on immediately, and the reference current value of the fuel cell is the maximum output current I max of the fuel cell; The minimum power-on time ton is constrained. At this time, the reference current of the fuel cell is 0; if the fuel cell is turned on, when the power of the battery is between its upper and lower limit thresholds, the output current of the fuel cell changes with the change of the load current. change, the reference current of the fuel cell is Id; if the fuel cell is in the off state, the load current is always greater than the maximum current of the fuel cell within 10 seconds, and the time of the fuel cell off state is greater than the minimum off time, then turn on the fuel cell; if The fuel cell is in the power-on state, and the load current has been less than the optimal current of the fuel cell within 10 seconds. The optimal current is the current value corresponding to the maximum efficiency point of the fuel cell system, and the power-on time is greater than the minimum power-on time. battery; if the load current is greater than the maximum current that the supercapacitor and battery can provide, the fuel cell is turned on.

The lower layer control includes the following steps:

Step a: Determine the reference current of the fuel cell according to the collected vehicle load current and battery power data, combined with the upper and lower limit thresholds of the high-efficiency range of the fuel cell current;

Step b: According to the collected load current of the vehicle and the reference current of the fuel cell determined in step a, the difference between the two is the difference current required by the super capacitor and the storage battery, and according to the positive and negative of the difference current and the super capacitor Power data, determine the reference current of the supercapacitor;

Step a in the above-mentioned lower layer control comprises the following steps:

According to the start-stop state of the fuel cell judged by the upper layer control, if the fuel cell is in the shutdown state, then the reference current of the fuel cell is 0; if the fuel cell is in the open state, the load current and the battery charging After the current is added, the demand current of the fuel cell is obtained. After the demand current of the fuel cell is compared with the upper and lower limit threshold currents of the fuel cell, the corresponding reference current of the fuel cell is obtained; the upper and lower limit thresholds of the fuel cell current are the actual measurement of the fuel cell system The efficiency test data delineate the upper and lower limit thresholds of the current of the fuel cell working in the high-efficiency region; if the demand current of the fuel cell is less than the lower current threshold of the fuel cell, then the reference current of the fuel cell at this time is the lower current threshold of the fuel cell; If the demand current of the fuel cell is between the upper and lower thresholds of the current of the fuel cell, then the reference current of the fuel cell is equal to the demand current value; if the demand current of the fuel cell is greater than the current upper threshold of the fuel cell, then the reference current of the fuel cell is the fuel cell The upper current threshold of the battery.

Step b includes the following steps:

According to the collected vehicle load current and the determined reference current of the fuel cell, the difference between the two is the difference current required by the supercapacitor and the battery, and judge whether the difference current is positive or negative, and if it is positive, go to step s1 , otherwise go to step s2;

Step s1 includes the following steps:

If the difference current is positive, to judge whether the supercapacitor can supply power, compare the difference current with the lower limit threshold of the battery current. The lower limit threshold refers to the minimum discharge current of the battery under the current SOC. If the difference current is less than the battery The current lower limit threshold of the super capacitor, the reference current of the super capacitor is 0, if the difference current is greater than the current lower limit threshold of the battery, compare the size of the super capacitor power and the super capacitor power lower limit threshold, if the super capacitor power is greater than the super capacitor power lower limit threshold, then The output supercapacitor reference current is Iscmax; otherwise, the output supercapacitor reference current is 0.

Step s2 includes the following steps:

If the difference current is negative, to judge whether the super capacitor can be charged, compare the power of the super capacitor with the initial power of the super capacitor. If the power of the super capacitor is less than the initial power of the super capacitor, then the charging current of the super capacitor is taken as the lower limit of the current of the super capacitor threshold, otherwise the charging current of the supercapacitor is 0.

Beneficial effects: the present invention provides an energy distribution method for a composite power system considering the fuel cell start-stop strategy. The present invention adopts a combination of upper-layer control and lower-layer control. The upper layer is the start-stop strategy of the fuel cell, and the lower layer is the distribution of energy. According to the electric quantity of the storage battery collected by the data acquisition module, the electric quantity of the supercapacitor and the current demand of the load, the energy distribution is carried out to the fuel cell module and the supercapacitor module; The actual measured efficiency test data of the selected fuel cell system stipulates the upper and lower limit thresholds of the fuel cell working in the high-efficiency area, so that the fuel cell can meet the high-efficiency range during operation, thereby improving the working efficiency of the entire system; in the composite power system The start-stop strategy of the fuel cell system is added to the energy management, and considering the shortcoming of the fuel cell's slow dynamic response and prolonging its life, the minimum on-time and minimum off-time restrictions are introduced, so as to reduce the frequent start of the fuel cell as much as possible; for The supercapacitor ensures that it maintains a normal power level, and the life of the entire system is greatly improved through the above methods.

Description of drawings

Fig. 1 is the structural representation of composite power supply system of the present invention;

Fig. 2 is the block diagram of composite power source control method among the present invention;

Fig. 3 is a flow chart of the energy distribution method of the storage battery and the supercapacitor in the present invention.

Detailed ways

The present invention is described in detail below in conjunction with accompanying drawing and specific embodiment:

As shown in Figure 1, the composite power supply system includes: a fuel cell module, a supercapacitor module, a storage battery module, a data acquisition module, and a composite power supply controller; the dotted line in the figure is a signal connection line, and the solid line is an electrical connection line. The module is used to provide the main power source for the car, the supercapacitor module is used to provide peak power for the car, the battery module is used to supplement the remaining power required by the car, and the composite power controller is connected to the data acquisition module , the data acquisition module is respectively connected with the fuel cell module, the storage battery module, and the supercapacitor module; the battery module is directly connected with the load module, so as to realize the supplement of the remaining power demand of the vehicle after the fuel cell and the supercapacitor supply energy; the said The fuel cell module is connected to a unidirectional DC-DC controller, and the unidirectional DC-DC controller is respectively connected to the load and the composite power supply controller to realize the unidirectional energy supply of the fuel cell module to the DC bus; the supercapacitor The module is connected to a bidirectional DC-DC controller, and the bidirectional DC-DC controller is respectively connected to the load and the composite power controller to realize the charging and discharging of supercapacitor electric energy. The composite power controller includes two parts of upper layer and lower layer control, The upper layer is the start-stop strategy of the fuel cell, and the lower layer is the distribution of energy. According to the battery power collected by the data acquisition module, the power of the super capacitor and the current demand of the load, the fuel cell module and the super capacitor module are used for energy distribution;

The data acquisition module includes a load current and voltage acquisition module, a fuel cell current acquisition module, a super capacitor power acquisition module, and a battery power acquisition module; after the load current acquisition module is connected in series with the load in the car, it is connected to the composite power controller After the load voltage acquisition module is connected in parallel with the load, it is connected with the composite power controller; the fuel cell power acquisition module is connected with the fuel cell module and the composite power controller respectively; the supercapacitor power acquisition module is respectively connected with the supercapacitor module It is connected with the composite power controller; the storage battery electricity collection module is respectively connected with the supercapacitor module and the composite power controller.

Take the fuel cell of German EK company as an example:

As shown in Figure 2, an energy distribution method for a composite power system considering the fuel cell start-stop strategy, including upper-level control and lower-level control:

The upper-level control is the start-stop control of the fuel cell. The control method is to collect the battery power data and the load current of the car, and determine the fuel cell to start and shut down according to the current on-off state of the fuel cell and the power data of the battery. The upper-level control The start-stop control method of the fuel cell includes: judging the current state of the vehicle according to the positive and negative of the collected load current of the vehicle. If the current is negative, it is in the braking state, and the reference current value of the fuel cell is 0. If the current is positive, the car is in the driving state, and the fuel cell is turned on or off according to the collected power data of the battery and the current switch state of the fuel cell; threshold, then regardless of the constraint of the minimum shutdown time toff (here 5s, combined with the value of the specific system), the fuel cell is turned on immediately, and the reference current value of the fuel cell is the maximum current of the fuel cell, and the maximum current passes through the fuel cell The test data is available. In this embodiment, the electric stack with a peak power of 35kW from the German EK company is selected, and the corresponding maximum current is about 230A; The battery shuts down immediately, regardless of the constraint of the minimum power-on time ton (the value here is 5s, and the specific value needs to be adjusted according to the specific system value), at this time the reference current of the fuel cell is 0; if the fuel cell is on, when When the power of the battery is between its upper and lower limit thresholds, the output current of the fuel cell changes with the change of the load current; if the fuel cell is turned off, the load current is always greater than the maximum current of the fuel cell within 10 seconds, and If the fuel cell shutdown time is greater than the minimum shutdown time, the fuel cell is turned on; if the fuel cell is in the power-on state, the load current has been less than the optimal current of the fuel cell within 10 seconds, and the startup time is greater than the minimum shutdown time, the fuel cell is turned off. battery; if the load current is greater than the maximum current that the supercapacitor and battery can provide, the fuel cell is turned on, and the optimal current is the current value corresponding to the maximum efficiency point of the fuel cell system, and the optimal current of the fuel cell of the German EK company is 82A, The reference current of the fuel cell in the upper layer control is the total vehicle demand current Id.

The control content of the lower layer control includes:

Step a: According to the collected load current and battery power data, combined with the upper and lower limit thresholds of the high-efficiency range of the fuel cell current, determine the reference current Ifcref of the fuel cell; In the stop state, the reference current of the fuel cell is 0; if the fuel cell is in the start state, according to the collected load current Iload, and the charging current of the battery, the demand current of the fuel cell is obtained, and the demand current of the fuel cell and the fuel cell After comparing the upper and lower limit threshold currents, the corresponding reference current Ifcref of the fuel cell is obtained; the upper and lower limit thresholds of the fuel cell current are the measured efficiency test data of the fuel cell system to delineate the upper and lower currents of the fuel cell working in the high-efficiency area limit threshold. If the demand current of the fuel cell is less than the lower current threshold of the fuel cell, then the output fuel cell reference current is the lower current threshold of the fuel cell; if the demand current of the fuel cell is between the upper and lower current thresholds of the fuel cell, then the fuel cell The reference current of the fuel cell is equal to the demand current value; if the demand current of the fuel cell is greater than the upper current threshold of the fuel cell, then the reference current of the fuel cell is the upper current threshold of the fuel cell; for the fuel cell system of EK, the high efficiency range refers to the system efficiency In the area above 45%, the current range is about 40A-100A, where the lower limit is 40A, and the upper limit is 100A.

Step b: According to the collected vehicle load current Iload and the reference current Ifcref of the fuel cell determined in the previous step, the difference Idi between the two is the difference current required by the supercapacitor and the battery, according to the positive and negative of the difference current and The power data of the supercapacitor determines the reference current of the supercapacitor.

The reference current of the fuel cell in the lower layer control is the current Ifcref finally distributed by the fuel cell.

In the lower layer control, the flow chart of the energy control method in step b is shown in Figure 3, which specifically includes the following steps:

According to the collected vehicle load current and the determined reference current of the fuel cell, the difference between the two is the difference current Idi provided by the supercapacitor and the storage battery, judge whether the difference current is positive or negative, and if it is positive, enter the step s1, otherwise go to s2.

The control method of step s1 is:

If the differential current Idi is a positive value, it is necessary to judge whether the supercapacitor can supply power. Compare the current lower limit threshold Ibamin of the difference current and the storage battery. The lower limit threshold refers to the minimum discharge current of the storage battery under the current SOC. If the difference current is less than the current lower limit threshold Ibamin of the storage battery, the reference current Isc of the output supercapacitor is 0 . If the difference current is greater than the current lower limit threshold of the battery, compare the supercapacitor power with the supercapacitor power lower limit threshold, if the super capacitor power SOCsc is greater than the super capacitor power lower limit threshold SOCmin, then output the super capacitor reference current as Iscmax; otherwise output supercapacitor The capacitor reference current Isc is zero.

The control method of step s2 is:

The difference current Idi is a negative value, and it is necessary to judge whether the supercapacitor can be charged. Compare the power SOCsc of the super capacitor with the initial power SOCint of the super capacitor. If the power SOCsc of the super capacitor is less than the initial power SOCint of the super capacitor, then the charging current Isc of the super capacitor takes the lower limit threshold of the current of the super capacitor, otherwise the charging current of the super capacitor is 0.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (4)

1. A composite power system energy distribution method considering fuel cell start-stop strategy, characterized in that, the composite power system includes a fuel cell module, a supercapacitor module, a storage battery module, a data acquisition module, and a composite power controller; The composite power supply controller is connected with the data acquisition module, and the data acquisition module is respectively connected with the fuel cell module, the storage battery module, and the supercapacitor module; the storage battery module is directly connected with the load module; the fuel cell module is connected with a single To the DC-DC controller, the unidirectional DC-DC controller is respectively connected to the load and the composite power controller; the supercapacitor module is connected to a bidirectional DC-DC controller, and the bidirectional DC-DC controller is respectively Connected with the load and the composite power controller, the composite power controller includes two parts, the upper layer and the lower layer control, the upper layer is the start-stop strategy of the fuel cell, and the lower layer is the distribution of energy, according to the battery power collected by the data acquisition module , the electric quantity of the supercapacitor and the current demand of the load, the energy distribution is carried out to the fuel cell module and the supercapacitor module; the data acquisition module includes a load current acquisition module and a load voltage acquisition module, a fuel cell current acquisition module, and a super capacitor power acquisition module, battery power collection module; the load current collection module is connected to the composite power controller after the load in the car is connected in series; the load voltage collection module is connected to the composite power controller after the load is connected in parallel; the fuel cell The power collection module is connected with the fuel cell module and the composite power controller respectively; the supercapacitor power collection module is connected with the supercapacitor module and the composite power controller respectively; the battery power collection module is connected with the supercapacitor module and the composite power controller respectively connection; the energy distribution includes upper-level control and lower-level control; the upper-level control is the start-stop control of the fuel cell: collect the power data of the storage battery and the load current of the car, according to the current open and close state of the fuel cell and the power data of the battery , to determine the start-up and shutdown operations of the fuel cell, which specifically includes the following steps: (1) According to the positive and negative of the collected car load current, judge the current state of the car, if the current is negative, the car is in the braking state, and the reference current value of the fuel cell is 0, if the current is positive, the car is in the driving state; (2) According to the collected power data of the battery and the current switch state of the fuel cell, the fuel cell is turned on or off; if the fuel cell is in the off state, when the battery When the power of the fuel cell is less than its lower limit threshold, then regardless of the constraint of the minimum shutdown time toff, the fuel cell is turned on immediately, and the reference current value of the fuel cell is the maximum current Imax of the fuel cell; if the fuel cell is turned on, when the power of the battery is greater than its When the upper threshold is set, regardless of the constraint of the minimum power-on time ton, the fuel cell is shut down immediately, and the reference current of the fuel cell is 0 at this time; The output current of the battery varies with the variation of the load current of the vehicle, and the reference current of the fuel cell is Id; if the fuel cell is in a shutdown state, the load current is always greater than the maximum current of the fuel cell within 10 seconds, and the fuel cell is shut down state time is greater than the minimum power-off time, then turn on the fuel cell; if the fuel cell is in the power-on state, the load current is always less than the optimal current of the fuel cell within 10 seconds, and the power-on time is greater than the minimum power-on time, then turn off the fuel cell; if The load current is greater than the maximum current that the supercapacitor and battery can provide, and the fuel cell is turned on; the lower layer control is the control of energy distribution: according to the collected load current of the vehicle and the reference current of the fuel cell, the difference between the two is The differential current that the supercapacitor and the storage battery need to provide, according to the positive and negative of the differential current and the power data of the supercapacitor, determine the reference current of the supercapacitor According to the power of the battery collected by the data acquisition module, the power of the supercapacitor and the load Current demand, energy distribution for fuel cell modules and super capacitor modules. 2. The energy distribution method of a composite power system considering a fuel cell start-stop strategy according to claim 1, wherein determining the reference current of the fuel cell in the lower layer control specifically comprises the following steps: judging the fuel cell current according to the upper layer control If the fuel cell is in the off state, the reference current of the fuel cell is 0; if the fuel cell is in the on state, according to the collected load current of the vehicle, add the load current and the charging current of the battery The demand current of the fuel cell is obtained, and after comparing the demand current of the fuel cell with the upper and lower threshold currents of the fuel cell current, the corresponding reference current of the fuel cell is obtained; if the demand current of the fuel cell is less than the lower limit threshold of the fuel cell current, then the When the reference current of the fuel cell is the current lower limit threshold of the fuel cell; if the demand current of the fuel cell is between the upper and lower limit thresholds of the current of the fuel cell, then the reference current of the fuel cell is equal to the demand current value; if the demand current of the fuel cell is greater than the fuel cell The upper current threshold of the fuel cell, then the reference current of the fuel cell is the upper current threshold of the fuel cell. 3. The energy distribution method of a composite power system considering fuel cell start-stop strategy according to claim 1 or 2, wherein the upper and lower limit thresholds of the fuel cell current are defined by the efficiency test data measured by the fuel cell system The upper and lower limit thresholds of the current where the fuel cell works in the high-efficiency region. 4. The energy distribution method of the compound power system considering the start-stop strategy of the fuel cell according to claim 1 or 2, characterized in that, determining the reference current of the supercapacitor in the lower layer control specifically comprises the following steps: according to the collected The load current of the vehicle and the reference current of the fuel cell, the difference between the two is the difference current required by the supercapacitor and the storage battery, judge whether the difference current is positive or negative, if it is positive, go to step s1, if it is negative value then enter step s2; the step s1 includes the following steps: if the differential current required to be provided by the supercapacitor and the storage battery is a positive value, to determine whether the supercapacitor can supply power, compare the differential current with the current lower limit threshold of the storage battery , if the difference current is less than the battery current lower limit threshold, the reference current of the supercapacitor is 0, if the difference current is greater than the battery current lower limit threshold, compare the supercapacitor power with the supercapacitor power lower limit threshold, if the supercapacitor power is greater than The lower limit threshold of the supercapacitor power, then the output supercapacitor reference current is Iscmax; otherwise, the output supercapacitor reference current is 0; the step s2 includes the following steps: if the difference current that the supercapacitor and the storage battery need to provide is negative, To judge whether the super capacitor can be charged, compare the power of the super capacitor with the initial power of the super capacitor. If the power of the super capacitor is less than the initial power of the super capacitor, then the charging current of the super capacitor takes the lower limit threshold of the current of the super capacitor, otherwise the charging current of the super capacitor The current is 0.

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