JPS60253171A - Fuel battery power generation system - Google Patents

Abstract

PURPOSE:To prevent drop of a performance of battery and improve life span by suppressing an output voltage of battery to an upper limit voltage or less even during low load operation of battery. CONSTITUTION:When a load command value P0 is reduced to a value P2 during operation at the point (a) on the characteristic curve (1) which indicates a battery output voltage-output current characteristic during normal operation, a battery output voltage V moves to the point (b) of the characteristic curve (1), exceeding the upper limit voltage Vm of battery. As a result, a positive voltage deviation 23 for the upper limit voltage Vm can be obtained at a subtractor 22 by such increase of voltage, a load command correction value 26 is obtained through a PID arithmetic unit 24 and a lower zero limiter 25 in accordance with such deviation signal 23, a load command value is increased and a corrected load command value 7 can be obtained by adding a load command value P0 of a load command setter 28 in the adder 27 to such value, and an output can be increased up to the point (c) where the voltage deviation becomes zero and is suppressed and controlled to a voltage lower than the upper limit voltage by giving such value to an invertor 6.

Description

Detailed Description of the Invention [Technical Field of the Invention] - The present invention relates to a fuel cell power generation system, and particularly to a fuel cell power generation system comprising a control means for controlling the flow rate of an oxidant supplied to an oxidizer electrode.

[Technical Background of the Invention] Conventionally, fuel cell power generation systems have been known as systems that directly convert energy contained in fuel into electrical energy. This fuel cell power generation system usually arranges a pair of electrodes, a combustion electrode and an oxidizer electrode, with an electrolyte layer in between, and a fuel such as hydrogen is brought into contact with the back of the fuel electrode, and air etc. are placed in contact with the back of the oxidizer electrode. oxidizer is brought into contact with the fuel cell, and the electrochemical reaction that occurs is used to extract electrical energy from between the pair of electrodes, and the electrical energy generated in the fuel cell is converted into electricity corresponding to the load command value by a power converter. The electrical energy is converted into a quantity (for example, electric power) and supplied to the load, and as long as the above-mentioned fuel and oxidizer are supplied, electrical energy can be extracted with high conversion efficiency.

Now, in this type of fuel cell power generation system, conventionally,
The electrical energy generated by the fuel cell is controlled by a power conversion device so that the amount of electricity matches the load command value, and the resulting battery output current is detected by a current detector and oxidized according to its magnitude. Obtain the supply flow rate command value of the agent,
This is then compared with the flow rate detection value from a flow rate detector that detects the flow peak of the oxidant flowing through the oxidizer supply line, and the control valve installed on the oxidizer supply line is adjusted according to the deviation value. By setting the opening degree to v11, the flow rate of the oxidizer supplied to the oxidizer electrode is set to 1lJIIl. Incidentally, the fuel is supplied to the fuel electrode in an amount commensurate with the recess of the cell generator.

[Problems with existing technology] However, in the conventional fuel cell power generation system described above, when the fuel cell is operated at low load, the cell output voltage is
The upper limit voltage limit, which is important for the lifespan and performance maintenance of fuel cells, has been exceeded, and since concentrated phosphoric acid is used as the electrolyte in fuel cells, as a result, when the temperature and voltage exceed a certain level, the electrolyte This is undesirable because it causes WI4 deterioration of the platinum catalyst, leading to a permanent deterioration in the performance of the battery. FIG. 2 shows the output current-output voltage characteristics of such a fuel cell, and it is understood from the figure that in a battery output state where the output current is less than 1ffi, the upper limit voltage limit Vm of the battery is exceeded.

[Object of the Invention] The present invention has been made in order to solve the above-mentioned problems. 1? / suppress down, 7
It is possible to significantly improve yj# by preventing a decline in the capacity of one tank.An object of the present invention is to provide a fuel cell power generation system.

[Invention 11 In order to achieve the above object, the present invention provides a combustion electrode and an oxidizing agent (a pair of Φ'l4ti with R5
5. At the same time, a large amount of fuel was supplied to the oxidizing agent electrode. The above using the electrochemical reaction that occurs at this time? ! A fuel cell that extracts electrical energy from between the tiII and the electricity generated by this fuel cell.
A power conversion device that converts energy into an amount of electricity commensurate with the load command value, a control valve provided above the oxidizing agent supply channel, and an upper &! A flow rate detector detects the flow rate of the oxidizer flowing through the oxidizer supply line, and a 'R current detector detects the output current of the fuel i'[pool. A computing device that disobeys the supply flow rate command value of the oxidizing agent according to the size, and comparing the command flow rate from this computing device and the detection Rm from the flow Il detector to the control valve based on the comparison result in parentheses. A flow rate control means comprising means for giving an adjustment signal to adjust the valve opening, a voltage detector for detecting the output voltage of the fuel cell, and a detected voltage from the voltage detector and an upper limit voltage of the battery. Load command correction that obtains a load command correction value based on the comparison result between the voltage rise detection means to be compared and the voltage rise detection means, and obtains a corrected load command value by comparing the load command correction value and the load command value. a first flow rate correction means for obtaining a first supply flow rate correction value based on a comparison result of the voltage rise detection means; or an electricity quantity detector for detecting an output quantity of electricity from the power conversion device; a second flow rate correction means for comparing the detected quantity of electricity from the Denki [Co., Ltd.] detector with the load command value and obtaining a second supply flow rate correction value based on the comparison result; The present invention is characterized in that at least one of the first and second supply flow rate correction values is given to the supply flow rate command value as the correction value.

[Embodiments of the Invention] First, the concept of the present invention will be described using FIGS. 3 and 4. FIG. 3 shows the battery output voltage characteristics with respect to the oxidizer utilization rate in a state where the N output power current and the fuel utilization rate are held at certain constant values. Further, FIG. 4 shows the battery output voltage characteristics with respect to the fuel utilization rate in a state where the battery output current and the oxidizer utilization rate are held at certain constant values. Note that the fuel or oxidizer utilization rate mentioned above refers to the cell output current for the amount of actual fuel and oxidizer supplied to the cell, the electrochemical theoretical fuel Fl f/i determined by the Faraday constant, and the theoretical The ratio to the amount of oxidizing agent is expressed as a percentage.

The present invention has a high utilization rate as shown in Figs. 3 and 4.
The output voltage decreases when This is what we are trying to do.

An embodiment of the present invention based on the above concept will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a fuel cell power generation system according to the present invention. In the figure, reference numeral 1 denotes a fuel cell comprising a pair of electrodes, a fuel electrode 2 and an oxidizer electrode 3, with an electrolyte layer in between.The fuel electrode 2 is supplied with a fuel such as hydrogen via a fuel supply line 4. Further, an oxidizing agent such as air is supplied to the oxidizing agent electrode 3 through an oxidizing agent supply line 5, and the electrochemical reaction that occurs at this time is used to generate DC power, which is electrical energy, from between the electrodes. ~I'm trying to take it out.

6 is the fuel cell 1 based on the corrected load command value 7, which will be described later.
An inverter is a power conversion device that converts the DC power generated by the AC power into AC power. Further, 8 is a control valve provided on the oxidizing agent supply line 5, 9 is a flow rate detector for detecting the flow rate of the oxidizing agent flowing through the oxidizing agent supply line 5, and 10 is the output current of the fuel cell 1. ■It is a current detector that detects. Further, 11 is a supply flow rate command for the oxidizer according to the magnitude of the output current I detected by the current detector 10! 112 is an arithmetic unit that obtains a function, 13 is a subtractor that compares the supply flow rate command value 12 from this arithmetic unit 11 with a supply flow rate correction value 14 to be described later, and obtains the deviation signal 15 as a corrected supply flow rate command value, 16 is the deviation signal 15 from this subtracter 13 and the detection signal 17 from the flow rate detector 9.
a subtractor 19 which obtains a deviation signal 18 by comparing the subtractor 16 with the deviation signal 18; a first PI which provides an adjustment signal 20 to the control valve 8 to adjust its valve opening degree in accordance with the deviation signal 18 from the subtractor 16;
D computing unit, which constitutes a flow rate control means.

On the other hand, 21 is a voltage detector for detecting the output voltage of the fuel cell 1, and 22 is a subtractor that compares the detected voltage V from this voltage detector 21 with the aforementioned upper limit voltage vm of the battery to obtain a deviation signal 23. These constitute the voltage rise detection means. Further, 24 is a PIDmI device with a reset windup prevention function that obtains a load command correction value according to the deviation signal 23 from the subtracter 22 and outputs it as 26 via the lower limit zero limiter 25; The command correction value 26 is compared with the load command value Pa from the load command setter 28, and the deviation signal is set as the above-mentioned correction load command value 7.
These adders constitute load command correction means. Further, 31 is a PID calculator with a reset windup prevention function that outputs the first supply flow mountain correction value (q) as 33 via the lower limit zero limiter 32 in accordance with the deviation signal 23 from the subtracter 22. These constitute the first flow rate correction means.Furthermore, 34 is a power detector as an electric quantity detector for detecting the output electric quantity (for example, electric power Ps) from the inverter 6, and 35 is this electric power detector. Power detection 1i1P from power detector 34
A subtractor 37 obtains a deviation signal 36 by comparing s with the power command value PO as a load command value from the load command setter 28; Obtain the flow rate correction value and set it as the lower limit zero limiter 3.
This is a PID calculator with a reset windup prevention function that outputs as 39 through 8, and these constitute the second flow rate correction means. Furthermore, 40 is an adder for adding the first and second supply flow rate correction values 33 and 39, and the added signal is added to the supply flow rate correction value 14.
I am trying to output it as .

In the above, the function in the arithmetic unit 11 is set as follows. In other words, in the case of a fuel cell, as the oxidizer utilization rate increases, the cell electromotive force tends to decrease, so in order to prevent phenomena such as polarity reversal, the voltage must be lower than the allowable lower limit voltage. Therefore, if the utilization rate is determined below a certain value above,
The supply flow rate of the oxidizing agent relative to the battery output current is determined by the following formula.

lXNX3600X22.4 4X96500X1000X0.21X77 where, F
Supply flow rate of dioxide agent (Nm/H), I: Battery output current <
A), N: number of fuel cells connected in series, η dioxide utilization rate, and constant Faraday number 96500 (c/mo
l), the concentration of (7) II element in the oxidizing agent is 0.21.

Next, the operation of the fuel cell power generation system having such a configuration will be described using FIG. 5. In FIG. 5, ■ indicates the battery output voltage-output current characteristics during normal operation.

First, let's assume that the 8 points on the characteristic curve ■ (load command value PO:
Considering the case where the load command 11Po decreases to P2 during operation on day P), the battery output voltage V is
The voltage shifts to point b on the characteristic curve and exceeds the upper limit voltage limit Vm of the battery. Then, due to this voltage increase, the upper limit voltage Vm
A positive voltage deviation 23 is obtained by the subtracter 22, and a load command correction value 26 is obtained according to this deviation signal 23 via the PID calculator 24 and the lower limit zero limiter 25, which is sent to the load command setter 28. An adder 27 is added to the load command value Pa from
By adding , the load command value is increased to obtain a corrected load command value 7, and by giving this to the inverter 6, the output is increased to the 0 point where the voltage deviation becomes zero, and the output is suppressed to below the upper limit voltage limit. be done.

However, in this state, the target load command value P2
The actual output power does not match. Therefore, the PID8II calculator 31 calculates the first value according to the deviation signal 23 from the subtracter 22.
A correction value for the supply flow rate is obtained, and this is outputted to the adder 40 as 33 via the lower limit zero limiter 32, and on the other hand, the deviation signal 36 between the actual output power PI obtained by the subtracter 35 and the load command value P2 is Accordingly, a second supply flow rate correction value is obtained, and this is passed through the lower limit zero limiter 38 as 39 to the adder 4.
0, the adder 40 adds these first and second supply flow rate correction values 33 and 39, and the added signal is given to the subtractor 13 as the supply flow rate correction value 14, thereby performing the above calculation. A corrected supply flow rate command value 15 is obtained by correcting the supply flow rate command value 12 from the device 11. Then, this corrected supply flow rate command value 15 and the flow rate detector 9
By obtaining a deviation signal 18 from the flow rate detection value 17 from the subtracter 16 and giving it to the PID calculator 19, the PI
In response to the deviation signal 18 from the subtractor 16, the D calculator 19 applies an adjustment signal 20 to the control valve 8 to adjust its valve opening in the closing direction, thereby adjusting the amount of oxidant supplied to the oxidizer electrode 3. decrease. As a result, the oxidizing agent utilization rate increases and the battery output voltage decreases, eventually shifting to the output voltage-current characteristic shown by It is possible to shift to point d, which is the operating point below the upper limit voltage Vm, and continue stable operation.

As described above, this fuel cell power generation system includes a pair of electrodes, a fuel electrode 2 and an oxidizer electrode 3, arranged with an electrolyte layer in between, and the fuel electrode 2 is supplied with hydrogen, etc. via a fuel supply line 4. An oxidizing agent such as air is supplied to the oxidizing agent electrode 3 via an oxidizing agent supply line 5, and the electrochemical reaction that occurs at this time is used to generate electrical energy from between the electrodes. A fuel cell 1 that extracts DC power,
an inverter 6 as a power conversion device that converts DC power generated in the fuel cell 1 into AC power based on the corrected load command value 7; a control valve 8 provided on the oxidizer supply line 5; a flow rate detector 9 for detecting the flow rate of the oxidizer flowing through the oxidizer supply line 5; a current detector 10 for detecting the output current I of the fuel cell 1;
an arithmetic unit 11 that obtains the supply flow rate command value 12 of the oxidizer using a function according to the magnitude of the output current I detected by the output current I;
A subtractor 13 that compares the supply flow rate command 1112 from the calculator 11 with the supply flow rate correction value 14 and obtains the deviation signal 15 as the corrected supply flow rate command value. A subtracter 16 that compares the deviation signal 15 from this subtracter 13 with the detection signal 17 from the flow rate detector 9 to obtain a deviation signal 18. This subtractor 1
a flow rate control means comprising a first PID calculator 19 that provides an adjustment signal 20 to the control valve 8 to adjust its valve opening according to a deviation signal 18 from the control valve 6; and detects the output voltage of the fuel cell 1; Voltage detector 21. Voltage rise detection means includes a subtracter 22 that compares the detected voltage V from the voltage detector 21 with the upper limit voltage Vm of the battery to obtain a deviation signal 23; PI DwAlli 24, Ko (DfAWJ) with a reset windup prevention function that obtains the load command correction value and outputs it as 26 via the lower limit zero limiter 25.
load command correction means comprising an adder 27 which compares the command Wa positive value 26 with the power command 11Pn as a load command value from the load command setter 28 and obtains a deviation signal as the corrected load command value 7; Deviation signal 2 from device 22
a first flow rate correction means comprising a PID calculator 31 with a reset windup prevention function that obtains a first supply flow rate correction value in accordance with 3 and outputs it as 33 via a lower limit zero limiter 32; A power detector 34 as an electric detector detects the output power PS which is the amount of electricity output from the inverter 6, and the power detection value Ps from the power detector 34 and the load command value from the load command setting device 28. P
a subtracter 35 to obtain a deviation signal 36 by comparing with O; A P with a reset windup prevention function obtains a second supply flow rate correction value according to the deviation signal 36 from the subtracter 35 and outputs it as 39 via the lower limit zero limiter 38.
A second flow rate correction means consisting of an ID calculator 37 adds the first and second supply flow rate correction values 33 and the three, and the added signal is sent to the calculator 11 as the supply flow rate correction value 14. It is composed of an adder 40 that provides

Therefore, it is possible to suppress the output voltage of the battery to below the upper limit voltage Vm in any low load operation range of the battery, prevent a deterioration in battery performance, and improve the life of the battery. It is possible to control the battery operating state so that the actual load output value always matches the actual load output value. Also,
Regarding voltage upper limit suppression control during load change transients, first, battery output control with a quick response suppresses excess of the voltage upper limit, and then supply oxidizer flow rate control, which has a relatively slow response, maintains a steady operating state below the upper limit voltage vm. Since the pullback control is performed, it is possible to operate the battery in a state where the upper limit voltage m is not exceeded as much as possible throughout the transient change period.

In the above embodiment, two flow rate correction means, the first and the second, are provided as means for correcting the supply flow layer command value 12, but it is preferable to provide only one of the first and second flow rate correction means. The same effect can be obtained even if

Further, in the above embodiment, the inverter 6 that controls AC power is used as the power conversion device, but it is not limited to this, and it is also possible to apply devices that control DC power, such as a chopper device or a variable resistance device. .

Furthermore, in the above embodiment, the load command value is given as the power command value, and a power detector is used as the quantity of electricity detector.
The load command value may be given as a voltage command value or a current command value, and a voltage detector or a current detector may be used as the electrical quantity detector.

[Effects of the Invention] As explained above, according to the present invention, the battery output voltage can be suppressed to below the upper limit voltage even during low load operation of the battery, thereby preventing deterioration in battery performance and improving the battery life. It is possible to provide an extremely reliable fuel cell power generation system that is capable of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing output current-output voltage characteristics of a battery, FIGS. 3 and 4 are diagrams for explaining the present invention in detail, FIG. 5 is a diagram for explaining the operation of the embodiment. DESCRIPTION OF SYMBOLS 1... Fuel cell, 2... Fuel electrode, 3... Oxidizer electrode, 4... Fuel supply line, 5... Oxidizer supply line, 6... Inverter, 8... Adjustment Valve, 9...Flow rate detector, 10...Current detector, 11...Arithmetic unit, 1
3.16, 22.35...Subtractor, 19.24, 31
．． 37... PID calculator, 21... Voltage detector, 2
5.32.38...lower zero limiter, 27.40...
- Adder, 28... Load command setter, 34... Power detector. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 4 Figure 5 It 'IL'A5';

Claims (2)

[Claims] (1) Arrange a pair of electrodes, a fuel electrode and an oxidizer electrode, with an electrolyte layer in between, and supply fuel to the fuel electrode and oxidizer to the oxidizer electrode, and utilize the electrochemical reaction that occurs at this time. a fuel cell that extracts electrical energy from between the electrodes, a power converter that converts the electrical energy generated by the fuel cell into an amount of electricity commensurate with a load command value, and a power converter installed on the oxidizing agent supply line. a control valve;
a flow rate detector that detects the flow rate of the oxidizer flowing through the oxidizer supply line; a current detector that detects the output current of the fuel cell; A computing device for obtaining the supply flow rate command value of the oxidizing agent, which compares the command flow rate from this computing device with the detected flow rate from the flow rate detector, and adjusts the valve opening of the control valve based on the comparison result. A flow rate control means comprising means for giving an adjustment signal to be adjusted, a voltage detector for detecting the output voltage of the fuel cell, and a voltage rise detection for comparing the detected voltage from the voltage detector with the upper limit voltage limit of the battery. means and
and a flow rate correction means for obtaining a supply flow rate correction value based on the comparison result of the voltage increase detection means, and is characterized in that the supply flow rate correction value of the flow rate correction means is given to the supply flow rate command value as the correction value. A fuel cell power generation system. (2) A pair of electrodes, a fuel electrode and an oxidizer electrode, are arranged with an N solute layer in between, and a fuel is supplied to the fuel electrode, and an oxidizer is supplied to the oxidizer electrode, and the electrochemical reaction that occurs at this time a fuel cell that extracts electrical energy from between the electrodes by using a a control valve,
a flow rate detector for detecting the flow rate of the oxidizer flowing through the oxidizer supply line; a current detector for detecting the output 'R flow of the fuel cell; and a magnitude of the output current detected by the current detector. Accordingly, the supply flow rate command value of the oxidizing agent is increased by 1q.
a processor that compares the command flow from this calculator with the detected flow rate from the flow rate detector, and provides an adjustment signal to the control valve to adjust its valve opening degree based on the comparison result. a voltage detector for detecting the output voltage of the fuel cell; a voltage rise detection means for comparing the detected voltage from the voltage detector with an upper limit voltage of the battery; A load command correction value is obtained based on the comparison result of the means, and the load command correction value and the load command value are compared to correct the electric power detection value from the electric quantity detector and the load command value. and a flow rate correction means for obtaining a supply flow rate correction value based on the comparison result, the fuel cell power generation characterized in that the supply flow rate correction value of the flow rate correction means is given to the supply flow rate command value as the correction value. system. (3) Arranging a pair of electrodes, a fuel electrode and an oxidizer electrode, with an electrolyte layer in between, and supplying fuel to the fuel electrode and oxidizer to the oxidizer electrode, and utilizing the electrochemical reaction that occurs at this time. a fuel cell that extracts electrical energy from between the electrodes, a power converter that converts the electrical energy generated by the fuel cell into electricity commensurate with a load command value, and a power converter installed on the oxidizing agent supply line. a control valve;
a flow rate detector that detects a flow mountain of the oxidizer flowing through the oxidizer supply line; a current detector that detects the output N flow of the fuel cell; a computing unit that obtains a command value of the supply flow rate of the oxidizing agent; and a computing unit that compares the command flow rate from the computing unit with the detected flow rate from the flow rate detector, and determines the valve opening of the control valve based on the comparison result. a voltage detector for detecting the output voltage of the fuel cell; and comparing the detected voltage from the voltage detector with the upper limit voltage of the cell. Voltage rise detection means; and load command correction means for obtaining a load command correction value based on a comparison result of the voltage rise detection means and for obtaining a corrected load command value by comparing the load command correction value and the load command value. , a first flow rate correction means for obtaining a first supply flow rate correction value based on the comparison result of the voltage increase detection means;
an electricity quantity detector that detects the output electricity quantity from the power converter; a electricity quantity detection value from the electricity quantity detector and the load command value; and a second supply flow rate correction based on the comparison result. a second flow rate correction means for obtaining a value, and provides each of the first and second supply flow rate correction values to the supply flow rate command value as the correction value.