KR20200003630A - Power supply system of fuel cell and control method of the same - Google Patents

Abstract

The present invention relates to an electric power supply system of a fuel cell, which comprises: a fuel cell which generates electric power by chemical reaction between hydrogen and oxygen; a main bus end connecting fuel cell and load; a bi-directional converter which is disposed between the fuel cell and the load of the main bus end and converts the electric power; a battery supplying the electric power to the main bus end between the bidirectional converter and the load by charging/discharging or receiving the electric power; and a control unit for controlling the current of the bi-directional converter based on a charging state of the battery.

Description

Power supply system of fuel cell and its control method {POWER SUPPLY SYSTEM OF FUEL CELL AND CONTROL METHOD OF THE SAME}

The present invention relates to a power supply system for a fuel cell and a control method thereof, and more particularly, to a control for distributing power of a fuel cell system according to a required power of a load by charging or discharging power to a battery.

A fuel cell is an energy converter that converts chemical energy of fuel into electric energy by electrochemically reacting it without converting it into heat by combustion. It can also be used to supply power.

Particularly, in the polymer electrolyte membrane fuel cell (PEMFC) having a high power density, a membrane electrode assembly (MEA), which is a main component, is located at the innermost side, and the membrane electrode assembly is a hydrogen ion. A solid polymer electrolyte membrane that can be moved, and a cathode and an anode, which are electrode layers coated with a catalyst to allow hydrogen and oxygen to react on both sides of the electrolyte membrane.

1 shows a power supply system of a fuel cell according to the prior art.

Referring to FIG. 1, the power supply system of the fuel cell 10 including the conventional fuel cell 10 includes a battery 20 for charging or discharging generated power of the fuel cell 10. The battery 20 charges the electric power generated by the fuel cell 10, or charges the electric power by regenerative braking of the motor 32, and assists the motor 32 by discharging when the required electric power is large.

In the conventional power supply system of the fuel cell 10, the driving voltage ranges of the fuel cell, the motor 32, and the inverter 31 and the charge / discharge voltage ranges of the battery 20 are different from each other. Different voltage ranges were converted between the batteries 20 between the main bus terminals connected between the 32, including a bidirectional high voltage DC / DC converter (BHDC). However, in the case of a large-capacity driving system requiring a voltage of 600V or more in the motor 32, such a power supply system of the fuel cell 10 cannot be applied.

Accordingly, a power supply system of the fuel cell 10 in which a converter for voltage conversion is further added to the main bus terminal between the fuel cell 10 and the motor 32 has been developed. However, as more converters are used, efficiency decreases due to converting. As a result, the efficiency of the power supply system itself of the fuel cell 10 decreases, thereby deteriorating fuel efficiency.

In order to solve this problem, there is a demand for a fuel cell power supply system that maximizes the conversion efficiency by appropriately controlling the charging and discharging of a battery while minimizing a converter.

The matters described as the background art are only for the purpose of improving the understanding of the background of the present invention, and should not be taken as acknowledging that they correspond to the related art already known to those skilled in the art.

KR 10-1047406 B

The present invention has been proposed to solve such a problem, and is to provide a power supply system for a fuel cell and a control method thereof including a large-capacity driving system having a high efficiency by reducing the use of a converter.

A fuel cell power supply system according to the present invention for achieving the above object is a fuel cell for generating power by a chemical reaction of hydrogen and oxygen; A main bus stage connecting between the fuel cell and the load; A bidirectional converter provided between a fuel cell of the main bus stage and a load to convert electric power; A battery that supplies power or is supplied with power to the main bus terminal between the bidirectional converter and the load through charging or discharging; And a controller configured to control the current of the bidirectional converter based on the state of charge of the battery.

The controller may set the battery charge allowable current based on the state of charge of the battery, and control the sum of the set battery charge allowable current and the required current of the load as the current of the bidirectional converter.

A current sensor for measuring the battery charging current supplied from the main bus terminal to the battery; further comprising, the control unit may control the feedback of the current of the bidirectional converter using the battery charging current measured by the current sensor.

According to an aspect of the present invention, there is provided a method of controlling a power supply system of a fuel cell, the method comprising: estimating a charge amount of a battery; Setting a battery charge allowable current based on the estimated amount of charge of the battery; And controlling the current of the bidirectional converter based on the set battery charge allowable current.

The method may further include determining whether the required power of the load is within a preset power range before estimating the charge amount of the battery.

The preset power range may be greater than or equal to the first power on which the required power of the load is a reference for maintaining the idle state of the fuel cell.

The preset power range may be less than or equal to the second power that is the maximum generated power of the fuel cell.

In the setting of the battery charge allowable current, when the estimated charge amount of the battery is greater than the first charge amount, the battery charge allowable current may be set to a negative value.

In the setting of the battery charge allowable current, when the estimated charge amount of the battery is smaller than the second charge amount, the battery charge allowable current may be set to a positive value.

In setting the battery charge allowable current, when the estimated charge amount of the battery is equal to or less than the first charge amount and equal to or greater than the second charge amount, the battery charge allowable current may be set to zero.

In the step of controlling the current of the bidirectional converter, the sum of the set battery charge allowable current and the required current of the load may be controlled by the current of the bidirectional converter.

In the controlling of the current of the bidirectional converter, feedback of the current of the bidirectional converter may be controlled by measuring the battery charging current supplied from the main bus terminal to the battery.

According to the power supply system and control method thereof of the fuel cell of the present invention, even when power is supplied to a load requiring a high voltage, it has the effect of minimizing the power consumed for converting by minimizing the converter.

In addition, by limiting the charge and discharge current according to the amount of charge (SOC) of the battery has the effect of preventing overcharge or over-discharge of the battery to improve the durability.

In addition, by appropriately maintaining the amount of charge of the battery has the effect of improving the fuel economy of the vehicle, and ensures the running performance of the vehicle.

1 shows a power supply system of a fuel cell according to the prior art.
2 is a block diagram of a power supply system of a fuel cell according to an embodiment of the present invention.
3 is a flowchart of a method for controlling a power supply system of a fuel cell according to an embodiment of the present invention.

Specific structural to functional descriptions of the embodiments of the present invention disclosed in the specification or the application are only illustrated for the purpose of describing the embodiments according to the present invention, and the embodiments according to the present invention may be embodied in various forms. It should not be construed as limited to the embodiments described in this specification or the application.

Since the embodiments according to the present invention can be variously modified and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiments in accordance with the concept of the present invention to a particular disclosed form, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and / or second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another, for example, without departing from the scope of rights in accordance with the inventive concept, and the first component may be called a second component and similarly The second component may also be referred to as the first component.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between. Other expressions describing the relationship between components, such as "between" and "immediately between," or "neighboring to," and "directly neighboring to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is described, and that one or more other features or numbers are present. It is to be understood that the present invention does not exclude, in advance, the possibility of addition, presence of steps, actions, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal sense unless clearly defined herein. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

2 is a block diagram of a power supply system of a fuel cell according to an embodiment of the present invention.

2, a power supply system of a fuel cell 100 according to an embodiment of the present invention includes a fuel cell 100 generating power by a chemical reaction between hydrogen and oxygen; A main bus stage 300 connecting the fuel cell 100 and the load 200; A bidirectional converter 400 provided between the fuel cell 100 and the load 200 of the main bus stage 300 to convert power; A battery 500 for supplying power or supplying power to the main bus terminal 300 between the bidirectional converter 400 and the load 200 through charging or discharging; And a controller 600 for controlling the current of the bidirectional converter 400 based on the state of charge of the battery 500.

The fuel cell 100 may be a fuel cell stack in which hydrogen and oxygen are supplied to generate power. The fuel cell stack may generate power by a chemical reaction by receiving oxygen and air containing oxygen through a membrane-electrode assembly (MEA) including a catalyst to a cathode and an anode, respectively.

The generated power of the fuel cell 100 may be connected to the load 200 through the main bus stage 300. The load 200 is a device that consumes the supplied power, and may be an inverter 210 for supplying power to the motor 220 and the motor 220 as shown, and other balances of plant (BOP). Or it may include all of the load connected to the outside.

The generated power of the fuel cell 100 is supplied to the main bus terminal 300 at a voltage of about 250 to 450 [V], and when the load 200 is operated at the corresponding voltage, the bidirectional converter 400 is not necessary. When the load 200 is to be operated at a voltage higher than the voltage range, a step-up process is required. For example, when a large-capacity driving system is required, such as a commercial vehicle instead of a passenger car, a high voltage of about 600 [V] may be required for the motor 220. Therefore, the bidirectional converter 400 may be provided between the fuel cell 100 and the load 200 of the main bus stage 300 to convert power.

The battery 500 may supply or receive power to the main bus terminal 300 between the bidirectional converter 400 and the load 200 through charging or discharging. That is, when the generated power of the fuel cell 100 remains or the motor 220 regeneratively brakes the surplus electric power, the electric power may be supplied to the motor 220 as it is discharged when necessary.

The battery 500 is capable of charging and discharging in a high voltage region of about 600 [V] required for a large-capacity driving system. A separate converter may be provided in the main bus stage 300 between the bidirectional converter 400 and the load 200. It can be connected directly without further inclusion. Accordingly, the efficiency of power supply is improved by not wasting power consumed in converting.

As the battery 500 is directly connected to the main bus terminal 300 without a separate converter, charging and discharging of the battery 500 are bidirectionally provided between the fuel cell 100 and the load 200 of the main bus terminal 300. Control may be performed using the converter 400.

However, the charge and discharge of the battery 500 is controlled according to the OCV (Open Circuit Voltage) voltage of the battery 500, the OCV of the battery 500 can not be accurately known, the size of the load 200 is variable in real time As a result, the charging and discharging of the battery 500 could not be properly controlled. However, the controller 600 of the present invention can accurately control the charging current of the battery 500 by controlling the current of the bidirectional converter 400 based on the state of charge of the battery 500.

In detail, the controller 600 sets a battery charge allowable current based on the state of charge of the battery 500, and sets the sum of the set allowance of the charge charge current of the battery 500 and the required current of the load 200 in the bidirectional converter 400. Can be controlled by the current of. The method for setting the battery charge allowable current will be described later in the control method.

The power supply system of the fuel cell 100 of the present invention may further include a current sensor 700 for measuring the charging current of the battery 500 supplied from the main bus stage 300 to the battery 500, and includes a control unit. The 600 may feedback control the current of the bidirectional converter 400 using the charging current of the battery 500 measured by the current sensor 700.

3 is a flowchart of a method for controlling a power supply system of a fuel cell according to an embodiment of the present invention.

Referring to FIG. 3, the method for controlling the power supply system of the fuel cell 100 according to an embodiment of the present invention includes estimating a charge amount of the battery 500 (S200); Setting a battery charge allowable current based on the estimated amount of charge of the battery 500 (S300); And controlling the current of the bidirectional converter 400 based on the set battery charge allowable current (S400).

In the estimating amount of charge of the battery 500 (S200), the amount of power currently charged in the battery 500 or the amount of power dischargeable from the battery 500 may be estimated as a state of charge (SOC) of the battery 500. have. The amount of charge of the battery 500 may vary by external factors such as the temperature of the battery 500, and the amount of charge of the battery 500 that varies according to such external factors may be estimated by a separate pre-stored map. .

Before the step of estimating the charge amount of the battery 500 (S200), determining whether the required power of the load 200 is within a predetermined power range (S100); may further include.

The preset power range may be equal to or greater than the first power at which the required power of the load 200 becomes a reference for maintaining the idle stop state of the fuel cell 100. The idle stop state maintenance criterion of the fuel cell 100 may vary according to the charging amount of the battery 500, and the first power may also vary. In addition, the preset power range may be less than or equal to the second power that is the maximum generated power of the fuel cell 100. That is, the required power of the load 200 exceeds the maximum generated power of the fuel cell 100 so that the battery 500 is always discharged and may not be a range for assisting power.

Therefore, the preset power range is a section in which the required power of the load 200 is greater than or equal to the first power and less than or equal to the second power. The generated power of the fuel cell 100 may be charged or discharged in the battery 500. It may be in Part Load state. The fuel cell 100 continuously generates power in a preset power range, and the generated power of the fuel cell 100 is charged with the battery 500 or the battery 500 is discharged according to the amount of charge of the battery 500. The generated power of the fuel cell 100 may be assisted and supplied to the load 200.

Since the required power of the load 200 may be changed in real time, the operating state of the fuel cell 100 is continuously changed by using an average value for a predetermined time so as not to enter or exit the preset power range in real time. Can be prevented.

In the step of setting the battery charge allowable current (S300), when the estimated charge amount of the battery 500 is greater than the first charge amount (S210), the battery charge allowable current may be set to a negative value (S310). When the battery charge allowable current is negative, the battery 500 is discharged, not charged, and a current flows from the battery 500 to the main bus terminal 300.

The first charge amount is a charge amount in a state where the charge amount of the battery is sufficiently large, and may be preset to 80% or 90% of the maximum chargeable power amount.

Conversely, in the step of setting the battery charge allowable current (S300), when the estimated charge amount of the battery 500 is smaller than the second charge amount (S220), the battery charge allowable current may be set to a positive value. If the battery charge allowable current is positive, the battery 500 is charged, and a current flows from the main bus terminal 300 to the battery 500.

The second charge amount is a state in which it is necessary to charge the battery further, and a state in which the charge amount of the battery is small and may be preset to about 50% of the maximum chargeable power amount.

The battery charging allowable current may be fixed to a predetermined positive value or a predetermined negative value, or may be set to a plurality of positive values or negative values by dividing various steps according to the charging amount of the battery 500. It is also possible to set the battery charge allowable current continuously linearly or nonlinearly according to the charge amount of the battery 500.

In addition, it is possible to limit the magnitude of the battery charge allowable current. That is, the durability of the battery 500 may be improved by limiting the magnitude of the current for charging or discharging the battery 500, thereby preventing the battery from being damaged because too large current flows in the battery 500.

In step S300 of setting the allowable battery charge current, when the estimated charge amount of the battery 500 is less than or equal to the first charge amount and more than or equal to the second charge amount, the battery charge allowance current may be set to 0 (S330). That is, when the charge amount of the battery 500 is an appropriate level, the battery charge allowable current is set to 0 to minimize the power loss due to repeated charging and discharging.

In step S400 of controlling the current of the bidirectional converter 400, the sum of the set allowable battery charging current and the required current of the load 200 may be controlled by the current of the bidirectional converter 400.

In particular, in the step S400 of controlling the current of the bidirectional converter 400, the charging current of the battery 500 supplied from the main bus terminal 300 to the battery 500 is measured to feed back the current of the bidirectional converter 400. Can be controlled.

More specifically, an error between the set battery charge allowance current and the measured battery 500 charge current may be calculated and feedback control may be performed using the error. By using the PI control it is possible to control the current of the bi-directional converter 400 as follows.

Ic = Pgain * Error + Igain * Cumulative Error

Here, Ic is a current of the bidirectional converter 400, Pgain and Igain are gain values and weights appropriately set by repetitive experiments, and an error is a set battery charge allowance current and a measured battery 500 charge current. The difference value between, and the cumulative error is a cumulative error integrated value.

That is, the battery 500 may be controlled by reflecting an error from the battery charging allowance current set by feeding back the charging current of the battery 500 measured using the current sensor 700 or the like. In addition, by accumulating the error between the battery 500 charging current measured by using the integral control and the set battery charge allowable current cumulatively integrated in the control to minimize the error between the set battery charge allowable current Can be controlled.

After controlling the current of the bidirectional converter 400 (S400), it may be again determined whether the required power of the load 200 is a predetermined range (S500). That is, it is possible to determine whether the required power of the load 200 is the Part Load state in which the generated power of the fuel cell 100 described above may be charged or discharged, and the load 200 may be determined. If the required power is less than the first power or the second power is exceeded, the control may be terminated by leaving the part load state. If the required power of the load 200 is within a predetermined range, the process may return to the step S200 of estimating the charge amount of the battery 500 and the control may be repeated.

While shown and described with respect to specific embodiments of the present invention, it is within the skill of the art that various changes and modifications can be made therein without departing from the spirit of the invention provided by the following claims. It will be self-evident for those of ordinary knowledge.

100: fuel cell 200: load
210: inverter 220: motor
300: main bus stage 400: bidirectional converter
500 battery 600 control unit
700: current sensor

Claims (12)

A fuel cell generating electric power by a chemical reaction between hydrogen and oxygen;
A main bus stage connecting between the fuel cell and the load;
A bidirectional converter provided between a fuel cell of the main bus stage and a load to convert electric power;
A battery that supplies power or is supplied with power to the main bus terminal between the bidirectional converter and the load through charging or discharging; And
Control unit for controlling the current of the bi-directional converter based on the state of charge of the battery. The method according to claim 1,
The control unit sets the battery charge allowance current based on the state of charge of the battery, and controls the sum of the set battery charge allowance current and the load current required by the current of the bidirectional converter, characterized in that the fuel cell power supply system. The method according to claim 2,
Further comprising: a current sensor for measuring the battery charging current supplied from the main bus to the battery,
The control unit feedback control the current of the bidirectional converter using the battery charging current measured by the current sensor. A method of controlling a power supply system of a fuel cell of claim 1,
Estimating a charge amount of the battery;
Setting a battery charge allowable current based on the estimated amount of charge of the battery; And
And controlling the current of the bidirectional converter based on the set battery charge allowable current. The method according to claim 4,
And determining whether the required power of the load is within a preset power range before estimating the charge amount of the battery. The method according to claim 5,
The preset power range is a power supply system control method for a fuel cell, characterized in that the required power of the load is equal to or more than the first power which becomes a reference for maintaining the idle state of the fuel cell. The method according to claim 5,
The predetermined power range is a power supply system control method for a fuel cell, characterized in that the required power of the load is less than the second power which is the maximum generated power of the fuel cell. The method according to claim 4,
In the step of setting the battery charge allowable current, when the estimated amount of charge of the battery is greater than the first charge amount, the battery charge allowance current control method, characterized in that for setting a negative value. The method according to claim 4,
In the step of setting the battery charge allowable current, when the estimated amount of charge of the battery is less than the second charge amount, the control method of the power supply system of the fuel cell, characterized in that the battery charge allowable current is set to a positive value. The method according to claim 4,
In the step of setting the battery charge allowable current, when the estimated amount of charge of the battery is less than the first charge amount and more than the second charge amount, the battery charging allowance current is set to zero. The method according to claim 4,
In the controlling of the current of the bidirectional converter, the method of controlling the power supply system of a fuel cell, characterized in that the sum of the set battery charge allowable current and the required current of the load is controlled by the current of the bidirectional converter. The method according to claim 4,
In the step of controlling the current of the bi-directional converter, the control method of the power supply system of the fuel cell, characterized in that the feedback control the current of the bi-directional converter by measuring the battery charging current supplied to the battery from the main bus terminal.

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