KR20180035101A - Rate control hybrid electricity supplying system containing solid oxide fuel cell and secondary battery and controlling method - Google Patents

Abstract

The present invention provides an active hybrid power supply system including a secondary battery, a fuel cell, a power conversion device for converting an output voltage of the secondary battery, and a control unit for controlling a duty ratio of the power conversion device. The control unit converts a control parameter of the secondary battery and a control variable of the fuel cell into an integrated control variable satisfying Ohm′s law, calculates a command value for controlling the power conversion device at a duty ratio that reflects the integrated control variable, and maximally controls a current ratio of the secondary battery and the fuel cell. Accordingly, the present invention can easily determine an operation range of a system.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid power supply system and a control method of a fuel cell and a secondary battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid power supply system including a fuel cell and a secondary battery, and a control method of the system. More particularly, the present invention relates to an active hybrid power supply system and a control method thereof.

A PEMFC (Polymer Electrolyte Membrane Fuel Cell) is composed of a polymer electrolyte membrane, which is a pathway for the proton generated by the oxidation reaction, an anode that supplies protons from the fuel (hydrogen) through the oxidation reaction to the electrolyte membrane, and a proton provided from the electrolyte membrane And a cathode for reducing water to make water. Polymer electrolyte fuel cells (PEMFCs) convert chemical energy directly into electrical energy without any intermediate conversion process.

The energy conversion process in the fuel cell shows higher energy conversion efficiency than the conventional internal combustion engine. The products of the internal combustion engine or the heat engine are CO2 or environmentally harmful gases, while the reactants of the PEMFC are environmentally friendly because general water is generated. In addition, a polymer electrolyte fuel cell can exhibit consistent performance as long as fuel (H2) is provided. Such a characteristic of the fuel cell is particularly suitable as an energy source for a robot.

However, despite the many advantages of fuel cells, there are still many barriers to applying them to various fields. For example, due to the structural problems of fuel cells, it is difficult to instantaneously supply power to the load at startup, and it is difficult to cope with sudden changes in load.

On the other hand, a secondary battery, particularly a lithium ion battery, provides power while lithium ions move from the cathode to the anode and charges the battery in the opposite case. Lithium polymer batteries are basically the same structure as lithium ion batteries, but use solid or gel electrolyte. By using a solid or gel electrolyte, the lithium polymer battery has a high energy density and has the advantage of being able to easily shape its shape. However, the lithium polymer battery has a problem in that power is reduced according to the use time.

Therefore, in the case where the power supply device is composed of only the fuel cell, it is difficult to cope with the fast load due to the slow start time. On the other hand, when the power supply is composed only of the secondary battery, it has a fast load response characteristic but can not be used for a long time. For this reason, in order to overcome the disadvantage of mutual trade-off, a hybrid type power supply system combining a secondary cell and a fuel cell has recently been actively developed

However, as described above, since the fuel cell and the secondary battery have different current, resistance and voltage characteristics, it is not easy to apply the fuel cell and the secondary battery to one power supply device.

Korean Patent No. 10-0659818

The present invention provides an active hybrid power supply system and a control method that can easily and effectively control the output of a hybrid power supply system in which a fuel cell and a secondary battery are combined, and is easy to design.

In particular, the present invention relates to an active hybrid power supply system capable of controlling the output power of a secondary battery, including: an active hybrid power supply system for controlling the output of the system by controlling a duty ratio of the power converter; .

According to an aspect of the present invention, there is provided an active hybrid power supply system including a secondary battery, a fuel cell, a power conversion device for converting an output voltage of the secondary battery, and a control unit for controlling a duty ratio of the power conversion device , The control unit converts the control variables of the secondary battery and the control variables of the fuel cell into integrated control variables that satisfy the Ohm's law and sets a command value for controlling the power conversion apparatus to a duty And the current ratio between the secondary battery and the fuel cell is controlled to the maximum.

Preferably, the controller sets a command value for an output current of the secondary battery, measures an output current of the fuel cell, and receives a current ratio command value as the integrated control variable.

Preferably, the controller calculates a current ratio of the fuel cell and the secondary battery to a first integrated control variable, calculates a resistance ratio of the fuel cell and the secondary battery to a second integrated control variable, The relative voltage ratio of the secondary battery is calculated by a third integrated control variable, and the third integrated control variable may be expressed as a product of the first integrated control variable and the second integrated control variable.

Preferably, the control unit sets the step-up or step-down mode of the power converter according to the kind of the hardware, and calculates the duty ratio command value using the first integrated control variable.

Preferably, the control unit uses the Ohm's law to reflect the first integrated control variable to the duty ratio of the transducer according to the following equation (4) The current ratio between the secondary battery and the fuel cell can be maximally controlled.

&Quot; (4) "

,

이고, V_B는 이차 전지의 출력 전압이며, V_F는 연료 전지의 출력 전압이고, V_L은 부하 장치에 출력되는 전압을 의미하며, R_B는 이차 전지의 내부 저항이고, R_F는 연료 전지의 내부 저항을 의미한다.Where D _B is the duty ratio of the power converter, K _I is the first integrated control variable,

,

And, V _B is the output voltage of the secondary battery, V _F is the output voltage of the fuel cell, V _L refers to the voltage applied to the load device, and, R _B is the internal resistance of the secondary battery, R _F is the fuel cell . ≪ / RTI >

According to another aspect of the present invention, there is provided a method of controlling an active hybrid power supply system including a secondary battery and a fuel cell, the method comprising: (a) receiving a current command value of the secondary battery and a measured output current of the fuel cell; Wherein the control unit converts the control variables of the secondary battery and the control variables of the fuel cell into an integrated control variable satisfying the Ohm's law and the output current command value of the secondary battery received in the step (a) (B) calculating a current ratio command value by using an integrated control variable by calculating a ratio of an output current of the inverter to an output current of the inverter; And the control unit calculates a command value for controlling the power conversion apparatus connected to the secondary battery at a duty ratio that reflects the integrated control parameter calculated in the step (b), so that the current ratio of the secondary battery and the fuel cell is controlled to the maximum (C).

According to the present invention, in a hybrid circuit including a fuel cell and a secondary battery, the control unit controls three control variables (current, voltage, resistance) of the fuel cell and three control variables (current, voltage, resistance) Control variables into three integrated control variables. In particular, in this case, the three integrated control variables are defined as the ratio of the secondary cell to the fuel cell control variables, and satisfy the Ohm's law, which greatly facilitates circuit design and analysis.

According to the present invention, it is confirmed that the ratio of the current generated in the fuel cell and the secondary cell can be controlled by the duty ratio of the power conversion device by circuit analysis through the integrated control variable, The operating range of the system can be easily determined by controlling the duty ratio of the converter.

1 shows an active hybrid power supply system according to an embodiment of the present invention.
2 shows current and voltage relationships of an active hybrid power supply system including a fuel cell and a secondary battery.
Figure 3 is a graph which shows the change of the internal resistance (R _B) and voltage (V ^{^} _B) of the secondary battery by the electric power conversion in the active hybrid system according to an embodiment of the present invention.
4 shows the voltage ratio (K _V ) and the resistance ratio (K _R ) of the fuel cell and the secondary battery according to the duty ratio of the power conversion device.
5 shows the current ratio (K _I ) of the fuel cell and the secondary battery according to the duty ratio of the power converter.
Fig. 6 shows the change of the current ratio KI according to the change (2, 5, 10) of the resistance ratio KR of the fuel cell and the secondary battery in Fig.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to or limited by the exemplary embodiments. Like reference numerals in the drawings denote members performing substantially the same function.

The objects and effects of the present invention can be understood or clarified naturally by the following description, and the purpose and effect of the present invention are not limited by the following description. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 shows an active hybrid power supply system according to an embodiment of the present invention. Referring to FIG. 1, the hybrid power supply system may include a secondary battery 30, a fuel cell 10, a power converter 20, and a controller 50.

The fuel cell 10 is an apparatus that generates electrical energy by electrochemically reacting a fuel and an oxidant. The fuel cell 10 is not particularly limited. For example, oxygen is supplied to the cathode, fuel gas is supplied to the anode, and electrochemical reactions of the electrolysis reverse reaction type of water proceed, And may be a solid oxide fuel cell.

The secondary battery 30 is a device capable of supplying and charging electric energy. The secondary battery 30 is not particularly limited and may be, for example, a nickel-cadmium battery, a nickel-hydrogen battery, a nickel-zinc battery, or a lithium secondary battery.

The power conversion device 20 can control the output voltage of the secondary battery 30. [ As the power converter 20, a buck type DC converter or a boost type DC converter may be used. The power conversion device 20 is connected to the output terminal of the secondary battery 30 and the fuel cell 10 can be connected in parallel to the output terminal of the power conversion device 20.

The control unit 50 converts the control variables of the secondary battery 30 and the control variables of the fuel cell 10 into integrated control parameters satisfying the Ohm's law and inputs command values for controlling the system as integrated control variables The current ratio of the secondary battery 30 and the fuel cell 10 is adjusted to the maximum value by controlling the duty ratio of the power converter 20 by reflecting the integrated control parameter to the duty ratio of the power converter 20. [ .

The fuel cell 10 and the secondary battery 30 each have three control variables (voltage V, current I, and resistance R). The hybrid system according to the present embodiment in which the fuel cell 10 and the secondary battery 30 are combined is provided with control variables V _F , I _F and R _F of the fuel cell 10 for easy analysis and easy control of the system, And the control variables (V _B , I _B , R _B ) of the secondary battery 30 to the integrated control variables (K _V , K _I , K _R ).

The control unit 50 may set a command value for the output current of the secondary battery 30 and measure the output current of the fuel cell 10 to receive the current ratio command value as an integrated control variable.

2 shows the current and voltage relationship of the hybrid power supply system including the fuel cell 10 and the secondary battery 30. As shown in Fig.

2, the current I _F of the fuel cell 10 and the current I _B of the secondary battery 30 are given when the load device 5 is operated with a constant voltage maintained. The fuel cell 10 satisfies the relational expression V _F = V _F0 -R _F I _F , and the secondary battery 30 satisfies the relationship of V _B = V _B0 -R _B I _B. Here, V _F0 denotes the open-circuit voltage of the fuel cell 10, and V _B0 denotes the open-circuit voltage of the secondary battery 30.

The fuel cell 10 and the secondary battery 30 are electrical elements that are connected in parallel and satisfy the Ohm's law. In the case of a hybrid system in which two devices are connected in parallel _, we can obtain a coupling equation that is defined as a ratio from the intrinsic characteristics (V _F = V _F0 -R _F I _{F ,} V _B = V _B0 -R _B I _B ) . The Applicant has defined an integrated control variable representing the hybrid device from this combination formula. When the hybrid system operates under a constant voltage, the following equation (1) can be derived.

[Equation 1]

Here, K _I represents a current ratio between the fuel cell and the secondary battery. K _V represents the relative voltage ratio between the fuel cell and the secondary battery. K _R represents the resistance ratio of the fuel cell to the secondary battery. Here, it is known that a yarn hybrid element can be expressed by a ratio of the intrinsic characteristic values of the individual elements. When each control variable (voltage, current, resistance) of an individual element satisfies Ohm's law, the hybrid Ohm's law is satisfied after coupling. Therefore, it is noted that the K variable set as a ratio of the control variables of the fuel cell and the secondary battery in Equation (1) satisfies the Ohm's law (V = IR). In the hybrid system according to the present embodiment, three variables (V _B , V _F , I _B , I _F , R _B , and R _F ) (K _V , K _I , K _R ).

The control unit 50 derives the coupling equation expressing the relationship from the intrinsic characteristics of the two devices even when the fuel cell 10 and the secondary battery 30 are hybridized according to the relational expression of Equation (1).

The control unit 50 calculates the current ratio of the fuel cell 10 and the secondary battery 30 to the first integrated control variable and sets the resistance ratio of the fuel cell 10 and the secondary battery 30 to the second integrated control variable And calculates the relative voltage ratio between the fuel cell 10 and the secondary battery 30 as a third integrated control variable. In this case, the third integrated control variable can be expressed as a product of the first integrated control variable and the second integrated control variable, and eventually satisfies Ohm's law.

In this embodiment, the first integrated control variable may be K _I (I _B / I _F ) described above. In addition, the second integrated control variable may be K _R (R _B / R _F ) described above. Further, the third integrated control variable may be K _V ((V _B -V _L ) / (V _F -V _L )) described above.

The control unit 50 calculates the command value for controlling the power converter 20 using the converted integrated control parameter as the duty ratio D _F reflecting the integrated control variable, And the fuel cell 10 can be maximally controlled. Hereinafter, a process of the control unit 50 calculating and controlling the duty ratio D _F command value will be described.

Figure 3 is a graph which shows the change of the internal resistance (R _B) and voltage (V ^{^} _B) of the secondary battery 30 by the power converter 20 in the active hybrid system according to an embodiment of the present invention. The power converter 20 controls the output voltage of the secondary battery 30.

The ratio of the input voltage to the output voltage of the power converter 20 is defined as duty ratio D _B in the present embodiment in which the power converter 20 capable of controlling the output voltage of the secondary battery 30 is configured in the hybrid system, . For reference, the duty ratio D _B has a value of 1 or less in a buck type power conversion apparatus and 1 or more in a boost type power conversion apparatus.

The change in the voltage of the secondary battery 30 by the power converter 20 can be expressed as V _B0 = D _B V _B0 . Here, V _B is the output voltage of the secondary battery, and R _B is the internal resistance of the secondary battery. The change in the internal resistance of the secondary battery 30 by the power converter 20 can be expressed as R _B = D _B ² R _B. Referring to Figure 3, after the secondary battery 10 of the _{V B = V B0 -R B I} B is a relational expression ^{_{V ^ B = D B V B0}} -D B 2 R B I B by the power converter 20 .

The control unit 50 can convert the voltage ratio and the resistance ratio of the fuel cell 10 and the secondary battery 30 into a variable of the duty ratio D _F. In the above embodiment, the voltage ratio can be the third integrated control variable K _V and the resistance ratio can be the second integrated control variable K _R. The voltage of the fuel cell 10 is ^{_{V ^ B0 = D B V B0}} , the internal resistance is ^{_{R ^ B = D B 2 R}} B. Here, the fuel cell 10 and the secondary battery 30 are connected in parallel and have the same voltage as the load voltage V _L. That is, V ^{^} = _B V _F = V _L. Since the voltage has a constant value, the integrated control variable can be expressed by the following equation (2) as a parameter of the duty ratio.

&Quot; (2) "

이고, V_B는 이차 전지의 출력 전압이며, V_F는 연료 전지의 출력 전압이고, V_L은 부하 장치에 출력되는 전압을 의미하며, R_B는 이차 전지의 내부 저항이고, R_F는 연료 전지의 내부 저항을 의미한다.here,

And, V _B is the output voltage of the secondary battery, V _F is the output voltage of the fuel cell, V _L refers to the voltage applied to the load device, and, R _B is the internal resistance of the secondary battery, R _F is the fuel cell . ≪ / RTI >

4 shows the voltage ratio K _V and the resistance ratio K _R of the fuel cell 10 and the secondary battery 30 according to the duty ratio of the power conversion device 20. 4, a voltage ratio K _{V, which} is a third integrated control variable, has a proportional relationship with a duty ratio D _F and a linear equation, and a second integrated control The resistance ratio K _{R, which} is a variable, has a proportional relationship with a duty ratio D _B and a quadratic equation. 4, the voltage ratio K _V and the resistance ratio K _R of the fuel cell 10 and the secondary battery 30 can be varied only by adjusting the duty ratio D _B of the power conversion device 20.

)In the above description, the control unit 50 expresses the second and third integrated control variables (K _R , K _V ) in the hybrid system as variables of the duty ratio DB. The control unit 50 may calculate the first integrated control variable K _{I as} the current ratio using Equation 3 using the second and third integrated control variables K _R and K _V defined in the above process. (

)

&Quot; (3) "

,

이다. 옴의 법칙으로 최종적으로 구한 관계식은 연료 전지(10)와 이차 전지(30)에서 발생되는 전류의 비(KI)가 전력변환장치(20)의 듀티비 D_B에 의해 결정될 수 있음을 보이고 있다.here,

,

to be. The relational expression finally obtained by the Ohm's law shows that the ratio KI of the current generated in the fuel cell 10 and the secondary battery 30 can be determined by the duty ratio D _B of the power converter 20.

5 shows the current ratio (K _I ) of the fuel cell 10 and the secondary battery 30 according to the duty ratio of the power inverter 20. [ 5 is a graph showing the relationship of Equation (3). Referring to FIG. 5, it can be seen that the value of the second integrated control variable K _I , which is the current ratio at a specific duty ratio of the power converter 20, . As a result, the active hybrid system according to the embodiment of the present invention can determine the operation range of the fuel cell 10 using the duty ratio of the power conversion device 20 as shown in FIG.

Fig. 6 shows a change in the current ratio KI according to the change (2, 5, 10) of the resistance ratio KR of the fuel cell 10 and the secondary battery 30 in Fig. According to the relationship defined in the controller 50, in consideration of the operating range, the hardware characteristics of the hybrid system 2 may determine an integrated control variable (K _R), the second from K _R of the integrated control variables suitable fuel cells (10 And the secondary battery 30 can be selected.

Referring to FIG. 1 again, a process of controlling the output of the fuel cell 10 using the integrated control variable will be described.

The control unit 50 receives the output current command value of the secondary battery 30 and the measured output current of the fuel cell 10 (a); The control parameter of the secondary battery 30 and the control parameter of the fuel cell 10 are converted into integrated control parameters satisfying the Ohm's law and the output current command value of the secondary battery 30 inputted in the step (a) (B) calculating a ratio of the output current of the fuel cell (10) and calculating a current ratio command value using an integrated control variable; The command value for controlling the power conversion apparatus 20 connected to the secondary battery 30 and the secondary battery 30 is calculated at a duty ratio that reflects the integrated control parameter calculated in the step (b) And (c) controlling the current ratio to the maximum.

는 제어부(50)에서 다음과 같이 산출된다.3 to 6, the control unit 50 can set the output current command value I _B * of the secondary battery 30 capable of providing the maximum output of the system. In step (a), the controller 50 receives the output current command value I _B * and the output current I _F of the fuel cell 10 as input values. In step (b), the control unit 50 calculates a first integrated control variable K _I (a current ratio command value) by a ratio of the applied current command value I _B * of the secondary battery 30 and the output current I _F of the fuel cell 10 *. In step (c), the control unit 50 determines the step-up or step-down mode of the power converter 20 in consideration of the type of hardware. As the fuel cell 10 and the secondary battery 30 are determined

Is calculated by the control unit 50 as follows.

the controller 50 generates the duty ratio command value D _B * of the power converter 20 of the secondary battery 30 in step (c). At this time, the controller 50 can calculate the duty ratio command value D _B * according to the following equation (4) with reference to the above-mentioned equation (3).

&Quot; (4) "

에 따라 듀티비 지령값 D_B*를 계산한다. 또는, 제어부(50)는 전력변환장치(20)가 감압형인 경우,

에 따라 듀티비 지령값 D_B*를 계산한다.When the power conversion apparatus 20 is of the step-up type

To calculate the duty ratio command value D _B *. Alternatively, when the power conversion device 20 is of the reduced pressure type,

To calculate the duty ratio command value D _B *.

The conventional passive hybrid system does not include the control function, and the semi-active hybrid system controls the input amount of the energy elements to change the output amount. According to the embodiment of the present invention as described above, the output amount of energy elements is controlled through the power converter 20 by the active hybrid system. In this case, it is noted that the control unit 50 newly defines the hybrid variable of the energy elements and controls the duty ratio of the power conversion apparatus 20 using the defined hybrid variable.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. will be. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by all changes or modifications derived from the scope of the appended claims and equivalents of the claims.

Claims (6)

In an active hybrid power supply system,
A secondary battery, a fuel cell, a power converter for converting an output voltage of the secondary battery, and a controller for controlling a duty ratio of the power converter,
Wherein,
A control parameter of the secondary battery and a control variable of the fuel cell are converted into an integrated control variable satisfying the Ohm's law, a command value for controlling the power conversion apparatus is calculated with a duty ratio reflecting the integrated control variable, And the current ratio of the secondary battery and the fuel cell is maximized.
The method according to claim 1,
Wherein,
Wherein an instruction value for an output current of the secondary battery is set and an output current of the fuel cell is measured to receive a current ratio command value as the integrated control variable.
The method according to claim 1,
Wherein,
Calculating a current ratio of the fuel cell and the secondary battery to a first integrated control variable, computing a resistance ratio of the fuel cell and the secondary battery to a second integrated control variable, Is calculated by the third integrated control variable,
Wherein the third integrated control variable can be expressed as a product of the first integrated control variable and the second integrated control variable.
The method of claim 3,
Wherein,
Wherein the step-up or step-down mode of the power conversion apparatus is set according to the kind of the hardware, and the duty ratio command value is calculated using the first integrated control variable.
The method of claim 3,
Wherein,
The first integrated control variable is reflected to the duty ratio of the power converter according to Equation (4) below using the Ohm's law to control the duty ratio of the power converter, And the current ratio of the first power supply to the second power supply is maximized.
&Quot; (4) "

Where D _B is the duty ratio of the power converter, K _I is the first integrated control variable,

,

And, V _B is the output voltage of the secondary battery, V _F is the output voltage of the fuel cell, V _L refers to the voltage applied to the load device, and, R _B is the internal resistance of the secondary battery, R _F is the fuel cell . ≪ / RTI >
A control method of an active hybrid power supply system including a secondary battery and a fuel cell,
(a) a control unit receiving an output current command value of the secondary battery and a measured output current of the fuel cell;
(b) the control unit converts the control variables of the secondary battery and the control variables of the fuel cell into an integrated control variable satisfying the Ohm's law, and the output current command value of the secondary battery received in the step (a) Calculating a ratio of an output current of the fuel cell to a current ratio command value using an integrated control variable; And
(c) calculating a command value for controlling the power conversion device connected to the secondary battery at a duty ratio that reflects the integrated control parameter calculated in the step (b), so that the current ratio of the secondary battery and the fuel cell is maximized And controlling the power supply to the active hybrid power supply system.

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