KR20070036481A - Method for controlling operation of fuel cell hybrid system - Google Patents

Abstract

Disclosed is a driving control method of a fuel cell hybrid system. In an operation control method of a fuel cell hybrid system according to the present invention, the operation control method of a fuel cell hybrid system for supplying at least one power of a fuel cell device and a battery to a load, the method comprising the steps of: sensing the temperature of the battery; Extracting the limit voltage of the battery corresponding to the temperature, sensing the voltage of the battery, and comparing the output power of the fuel cell device with the required power of the load when the detected battery voltage is lower than the limit voltage. Controlling the discharge. According to the present invention, it is possible to prevent the battery from discharging below the threshold voltage to prevent unexpected shutdown of the system and to prevent damage to the battery.

Fuel cell, hybrid, battery, temperature, driving control

Description

{Method for controlling operation of fuel cell hybrid system}

1 is a flowchart illustrating an operation control method of a fuel cell hybrid system according to an exemplary embodiment of the present invention.

FIG. 2 is a graph illustrating a current (capacity) -voltage curve according to a temperature of a battery used in the driving control method of FIG. 1.

3 is a block diagram of a system using an operation control method of a fuel cell hybrid system according to a preferred embodiment of the present invention.

4 is a diagram schematically illustrating a fuel cell device of an operation control device of the fuel cell hybrid system of FIG. 3.

FIG. 5 is a diagram schematically illustrating an example of a power distribution device coupled to an operation control device of the fuel cell hybrid system of FIG. 3.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell hybrid system, and more particularly, to an operation control method of a fuel cell hybrid system capable of preventing a battery from being discharged below a limit capacity to prevent unexpected shutdown of the system and to protect the battery.

A fuel cell is a device that converts energy contained in a fuel into electrical energy directly by chemical reaction. For example, fuel cells generate electrical energy using a reaction in which water is generated from hydrogen and oxygen, that is, a combustion reaction of hydrogen. This is represented by the following reaction scheme.

2H ₂ + O _2- > 2H ₂ O + 1.23 V

Fuel cells include phosphoric acid type, molten carbonate type, solid oxide type, polymer electrolyte type and alkali type. Among them, the polymer electrolyte fuel cell refers to a fuel cell using a proton conductive polymer electrolyte membrane as an electrolyte. The polymer electrolyte fuel cell generally has a stack structure for high power, and includes a catalyst for smoothly reacting the positive electrode and the negative electrode in the fuel cell. As the catalyst, a platinum catalyst supported on carbon is used. The fuel cell is drawing attention as a next-generation clean energy source with a very low emission of nitrogen compounds and sulfur oxides compared to a power generation system for burning fossil fuels.

On the other hand, since the fuel cell system generates optimal electric energy by using sufficient fuel and air, it is difficult to suddenly increase the output, and therefore, it is desirable to operate at a constant output. However, the load supplied from the fuel cell system does not consume only a certain amount of power. In addition, when instantaneous high power is required at the load, it is difficult to increase the output power in the fuel cell system, and thus it is not possible to respond quickly to the load fluctuation.

In order to solve the above problem, the conventional fuel cell system uses a fuel cell hybrid system in which a battery is coupled to supply the output of the battery to the load in response to the instantaneous high power demand of the load.

The battery has a gentle charge / discharge characteristic curve, but also has a voltage section in which the capacity drops sharply. If the battery consumes power below a sharp drop in capacity, the load on the laptop or mobile phone immediately shuts down, and the battery can be fatally damaged. Thus, the battery must be properly controlled so that its capacity is not used below a voltage that drops sharply.

An object of the present invention is to provide a method for controlling operation of a fuel cell hybrid system which can prevent the battery from being discharged below a threshold voltage, thereby preventing an unexpected shutdown of the system and protecting the battery.

In order to achieve the above object, according to a preferred aspect of the present invention, in the operation control method of a fuel cell hybrid system for supplying at least one of the fuel cell device and the power to the load, (a) a battery in the operation control device Sensing the temperature of the; (b) extracting a limit voltage of the battery corresponding to the sensed temperature; (c) sensing the voltage of the battery; And (d) controlling the charging and discharging of the battery by comparing the output power of the fuel cell device with the required power of the load when the sensed battery voltage is lower than or equal to the threshold voltage. .

Preferably, step (d) includes charging the battery when the sensed battery voltage is below the threshold voltage and the output power of the fuel cell device exceeds the required power of the load.

In addition, the step (d) is the step of separating the load in the fuel cell device when the detected battery voltage is less than the threshold voltage, the output of the fuel cell device is less than the required power of the load, and the output power of the fuel cell device Further comprising the step of charging. The method also includes outputting an alarm signal for disconnecting the load in the fuel cell device.

In addition, the step (d) further includes the step of stopping the fuel cell hybrid system when the sensed battery voltage is below the threshold voltage and the output of the fuel cell device is below the required power of the load. The method may further include outputting an alarm signal for stopping operation.

In addition, step (a) includes the step of measuring the temperature of the center of the battery.

In addition, the step (b) includes the step of extracting a threshold voltage corresponding to the temperature from the pre-stored table.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings for those skilled in the art to easily implement the present invention.

1 is a flowchart illustrating an operation control method of a fuel cell hybrid system according to an exemplary embodiment of the present invention.

Referring to FIG. 1, in the operation control method of a fuel cell hybrid system, a limit voltage of a battery is changed and set according to a temperature of a battery in an operation control device to prevent an unexpected shutdown of a system when a high power demand of a load is required. As a result, the discharge of the battery is controlled to prevent the battery from being discharged below a voltage at which the capacity of the battery is sharply lowered.

Specifically, first, when an operation start signal is input to the fuel cell hybrid system (S10), the temperature of the battery is sensed by the temperature sensor (S12). For example, the battery temperature at the time of discharge of the battery is detected through a thermistor or thermocouple, converted into a digital signal by an analog-to-digital converter, and the converted signal is sensed by the arithmetic processing unit.

Next, the threshold voltage of the battery corresponding to the sensed temperature is extracted (S14). For example, this step may be implemented to extract the threshold voltage of the battery corresponding to the sensed battery temperature from a table previously stored in a storage in the fuel cell hybrid system.

Next, the voltage of the battery is sensed by the predetermined voltage detector in a state where the threshold voltage of the battery is prepared (S16). For example, the battery voltage is detected through a voltmeter, converted into a digital signal by an analog-to-digital converter, and the converted signal is sensed by the computing processor.

Next, it is determined whether the detected battery voltage is lower than or equal to the threshold voltage (S18).

If the determination result is YES, it is determined whether the current stack output power exceeds the required power of the load (S20). If the determination result is no, the battery voltage is again sensed, and it is periodically determined whether the detected battery voltage is below the threshold voltage.

As a result of the determination, when the stack output power exceeds the required power of the load, the battery is charged while supplying the output power of the fuel cell device to the load (S22).

On the other hand, if the stack output power is less than or equal to the required power of the load, an alarm signal is output (S24). Here, the alarm signal is either a signal for notifying the load disconnection from the fuel cell device or a signal for notifying the operation of the system, as set in a later step.

Next, the battery is charged after disconnecting the load from the fuel cell device. Alternatively, the battery is charged after the fuel cell hybrid system is stopped (S26). This step is to charge the battery preferentially or to charge the battery separately after shutting down the system because it is difficult to meet the high power demand of the load when the capacity of the battery is insufficient. In this step, if the output power of the fuel cell device is greater than or equal to a predetermined value, the battery may be charged after disconnecting the load. If the output power of the fuel cell device is less than the predetermined value, the battery may be separately charged after stopping the system. According to the above-described configuration, it is possible to prevent damage to the battery or the system by failing to adequately meet the high power demand of the load when the capacity of the battery is insufficient.

FIG. 2 is a graph showing a current (capacity) -voltage curve according to the temperature of the battery employed in FIG. 1.

For the experiment, the battery was first prepared by charging for 3 hours at 0.5C-4.2V in an atmosphere of 25 ℃. The battery was discharged at a discharge rate of 0.2C-2.75V at battery temperatures of -20 ° C, -10 ° C, 0 ° C, 25 ° C, 45 ° C, and 60 ° C. Here, 0.2C indicates that the battery capacity can be discharged for 5 hours.

As can be seen in Figure 2, the voltage of the discharged battery is rapidly reduced capacity based on about 3.50V, when the battery temperature is 25 ℃ or more. On the other hand, as the temperature decreases, the cutoff voltage (hereinafter referred to as the limit voltage) gradually decreases and the usable capacity also decreases. When power is consumed even under a sharp drop in capacity, the load on the laptop or cell phone is shut down immediately, and the battery has a fatal adverse effect.

For example, if the threshold voltage of the battery is set to 3.6V, the battery will operate normally at temperatures above 25 ° C, but normal discharge of the battery will not be possible at temperatures below 25 ° C, preventing unexpected shutdown of the system. You must stop the system to do this. Conversely, if the threshold voltage is set to 3.25V, the battery will operate normally at temperatures above 0 ° C, but at temperatures above 0 ° C the system must be shut down despite the remaining battery capacity.

According to the above-described configuration, the limit voltage of the battery can be changed and set according to the temperature of the battery to stably and effectively operate and control the battery and the system as well as to make full use of the battery.

3 is a block diagram of a system using an operation control method of a fuel cell hybrid system according to a preferred embodiment of the present invention. In the following description, when an element is coupled to another element, the element is directly coupled to another element and is coupled to another element.

Referring to FIG. 3, a system 100 (hereinafter referred to as an operation control system) using an operation control method of a fuel cell hybrid system includes a voltage detector 110, a temperature detector 120, three analog-to-digital converters 132, 134 and 136 (hereinafter referred to as A / D converter), arithmetic processing unit 140, communication processing unit 150 and storage unit 160. In addition, the driving control system 100 is coupled to the battery 200, the fuel cell device 300, the power distribution device 400, and the electric device 500.

In detail, the voltage detector 110 detects a voltage of the battery 200. The voltage detector 110 may be configured to detect a voltage of the entire battery 200 or measure respective voltages of a plurality of battery cells in the battery 200. The voltage detector 110 provides the detected signal to the calculation processor 140 through the first A / D converter 132. The voltage detector 110 may be implemented with a conventional voltmeter.

The temperature detector 120 is installed on the surface or the inside of the battery 200 and detects the temperature of the battery 200. In the case of the battery 200 having a battery pack structure in which a plurality of battery cells are combined in series and / or in parallel, the temperature of the battery 200 is higher at the center than at the edge, so that the temperature detector 120 includes the battery 200. It is installed to measure the temperature in the central part of the. In addition, in the case of the battery 200 having a battery pack structure, the temperature detector 120 is preferably installed to measure the temperature of all the battery cells. The temperature detector 120 provides the detected temperature to the calculation processor 140 through the second A / D converter 134. The temperature detector 120 may be implemented with a thermistor or a thermocouple.

The calculation processor 140 detects a signal input from the voltage detector 110 and the temperature detector 120, and processes the detected signal according to a predetermined processing routine. Here, the detected signal includes the temperature of the battery and the battery voltage.

In detail, the operation processor 140 extracts a threshold voltage corresponding to the sensed temperature from the table stored in the storage 160. The limit voltage corresponding to the temperature can be implemented as a function. In addition, the operation processor 140 detects the current and voltage applied to the input terminal of the fuel cell device 300 and the output terminal of the electric device 500 by the third A / D converter 136 of the power distribution device 400. do. This is for sensing the output power of the fuel cell device 300 and the required power of the electric device 500 as a load. In the above case, the power of the input terminal and the output terminal of the power distribution device 400 may be detected by a predetermined current / voltage sensing means, and the current / voltage sensing means may be embedded in the power distribution device 400 or be configured separately. Can be.

In addition, the operation processor 140 compares the threshold voltage and the battery voltage, compares the output power of the fuel cell device 300 with the required power of the electric device 500, and then outputs predetermined output signals according to the comparison result. Generate. The generated output signal is transmitted to the communication processor 150. The operation processor 140 may be implemented as a digital signal processing device, and in this case, one or more of the three A / D converters may be omitted.

The above-described output signal is a signal for charging the battery when the battery voltage is below the threshold voltage and the output power of the fuel cell apparatus exceeds the required power of the load. Alternatively, the above-described output signal may be used to disconnect the load from the fuel cell device and charge the battery with the output power of the fuel cell device when the detected battery voltage is less than the threshold voltage and the output of the fuel cell device is less than or equal to the required power of the load. It is a signal. Alternatively, the above-described output signal is a signal for stopping the fuel cell hybrid system when the sensed battery voltage is below the threshold voltage and the output of the fuel cell device is below the required power of the load.

The communication processor 150 generates a control signal in response to the output signal of the operation processor 140, and transmits the generated control signal to the power distribution device 400 and / or the electric device 500. In addition, the communication processor 150 generates an alarm signal in response to the output signal of the operation processor 140. The generated alarm signal is transmitted to an imaging device or an audio device coupled to the driving control device 100 or transmitted to the electric device 500 and output through a screen or a speaker of the electric device 500. The communication processor 150 may be implemented as a wired or wireless communication circuit having a wired or wireless interface.

The storage unit 160 may include a table storing the discharge current of the battery 200 and the limit voltage of the battery corresponding to the discharge current. In addition, the storage 160 may store the number of charge / discharge cycles, that is, the cycle number of the battery 200. The storage unit 160 is coupled to the operation processor 140 and may be implemented as any storage device such as a RAM, a ROM, a flash memory, a hard disk, or the like. In addition, the storage 160 may be implemented as a logic circuit implemented by AND, OR, NAND, NOR gate, or the like.

The battery 200 includes a rechargeable battery that can be recharged by the fuel cell device 300 or an external commercial power source. The battery 200 may be implemented with at least one lithium ion secondary battery. When the battery 200 is formed of a plurality of lithium ion secondary batteries connected in series, each secondary battery may react differently to the charging current when the battery 200 is charged, and thus the battery 200 may be charged with each secondary battery. It is preferable that the voltage detector 110 capable of independently detecting a voltage is coupled. In this case, since the failure of a specific secondary battery in the battery 200 can be detected, there is an advantage that the state of the battery 200 can be more accurately identified.

As shown in FIG. 4, the fuel cell apparatus 300 includes an electricity generator 310 that directly oxidizes fuel to produce electrical energy. The electricity generation unit 310 may be implemented as a stack having a structure in which a plurality of fuel cells are stacked. In addition, the electricity generating unit 310 may be implemented as an electrolyte membrane 311 and an anode electrode 313 and a cathode electrode 315 bonded to both surfaces of the electrolyte membrane 311. As a fuel supplied to the fuel cell device 300, a hydrocarbon-based fuel such as methanol, ethanol, or natural gas may be used. In addition, the fuel cell device 300 includes a fuel pump 320 for storing fuel, a fuel pump 330 for supplying fuel, a fuel reformer 340 for reforming fuel, and an oxidant such as air or oxygen. An oxidant supply device 350 for supplying the cathode of 310 may be provided.

The power distribution device 400 is controlled by the arithmetic processing unit 140 as shown in FIG. 5, and the power of at least one of the battery 200 and the fuel cell device 300 by the switching means 410 and 420. It is coupled to supply to the electrical device (500). The switching means 410 and 420 may be implemented with transistors or thyristors. In addition, the power distribution device 400 detects the output power of the fuel cell device 300 by the current / voltage detectors 432, 434, 436, and 438, detects the required power of the electric device 500, and detects the detected power. The transmitted signal is transferred to the operation processor 140 through the third A / D converter 136. In addition, the power distribution device 400 converts the output power of the fuel cell device 300 by the power conversion means 440 to an appropriate level and / or manner suitable for use in the electric device 500. The power conversion means 440 is a DC / DC converter for converting the direct current output from the fuel cell device 300 to a different level of direct current or a DC / AC converter for converting the direct current output from the fuel cell device 300 to AC. Can be implemented.

The electrical device 500 refers to an electrical load using electrical energy of the battery 200 or the fuel cell device 300. The electric device 500 includes all devices that use electricity, such as a notebook, a mobile phone, and a home electric device. In addition, the electrical device 500 is coupled to the communication processing unit 150 of the operation control system 100, a device that receives a control signal or an alarm signal of the communication processing unit 150, and displays the screen in response to the signal. It includes.

On the other hand, it is difficult to combine the two devices with each other because the profile of the output voltage of the fuel cell device and the profile of the discharge voltage of the battery are different. In addition, in order to combine the output voltage of the fuel cell device and the battery, an additional expensive control device is required, and a system equipped with such an expensive control device is complicated in construction. Therefore, in the above-described embodiment, a combination of the output voltages of the fuel cell device and the battery is omitted, and a configuration in which the load is performed by the battery only when the high power of the load is required is described as a preferred embodiment.

On the other hand, although not explicitly mentioned in the above-described embodiment, the step of detecting the discharge current and the voltage of the battery includes detecting either one of the discharge current and the voltage first or both at the same time. And the detection unit for detecting the current or voltage of the battery of the above embodiment can be installed at any position if it can directly or indirectly detect the current and voltage of the battery.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, it is possible to easily prevent the battery from discharging below the limit capacity in the fuel cell hybrid system, thereby preventing unexpected shutdown of the system and protecting the battery.

Claims (8)

In the operation control method of a fuel cell hybrid system for supplying power to at least one of the fuel cell device and the battery, (a) sensing the temperature of the battery; (b) extracting a threshold voltage of the battery corresponding to the sensed temperature; (c) sensing the voltage of the battery; And and controlling the charging and discharging of the battery by comparing the output power of the fuel cell device with the required power of the load when the sensed battery voltage is less than or equal to the threshold voltage. Way. The method of claim 1, The step (d) of the fuel cell hybrid system comprising the step of charging the battery when the sensed battery voltage is less than the threshold voltage, the output power of the fuel cell device exceeds the required power of the load Operation control method. The method of claim 1, In the step (d), when the sensed battery voltage is less than the threshold voltage and the output of the fuel cell device is less than or equal to the required power of the load, separating the load from the fuel cell device, and the fuel cell Charging the battery with the output power of the device. The method of claim 3, wherein And outputting an alarm signal for disconnecting the load from the fuel cell device. The method of claim 1, The fuel cell hybrid system may include stopping the fuel cell hybrid system when the sensed battery voltage is less than the threshold voltage and the output of the fuel cell device is less than or equal to the required power of the load. Operation control method. The method of claim 5, And outputting an alarm signal for stopping operation of the fuel cell hybrid system. The method of claim 1, Wherein (a) is the operation control method of a fuel cell hybrid system comprising the step of measuring the temperature at the center of the battery. The method of claim 1, And (b) extracting the threshold voltage corresponding to the temperature from a pre-stored table.

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