JPS6297264A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To improve the extent of responsiveness to a load variation as well as to improve preservability in a system to gap differential pressure, by composing each valve opening command signal out of a stationary characteristic compensating part and a transient characteristic compensating part separately and thereby controlling a degree of valve opening. CONSTITUTION:Each detection signal out of both first and second flow detectors 51A and 51B and a differential pressure detector 52, each desired value signal corresponding to these detections signals, a detection signal out of a differential pressure detector 53, and each valve opening detection signal out of first to fourth flow control valves 4A-4D are all inputted into an optimum arithmetic unit 31. With a load variation in a fuel cell, either of these two inputted signals is varied whereby at least one side of respective value opening command signals is varied. With this constitution, each valve opening of these first to fourth flow control valves 4A-4D is controlled in an optimum condition. Therefore, responsiveness is improved and, what is more, system preservability to gap differential pressure is improved so better.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a fuel cell power generation system, and in particular to flow control of fuel gas and oxidant gas to a fuel cell and differential pressure between a fuel electrode and an oxidizer electrode. The present invention relates to a fuel cell power generation system equipped with a pressure flow rate optimum control device that optimally controls pressure (hereinafter referred to as interelectrode differential pressure).

[Technical background of the invention and its problems]

Conventionally, fuel cells have been known as devices that directly convert chemical energy contained in fuel into electrical energy. This fuel cell normally has a pair of electrodes, a fuel electrode and an oxidizer electrode, sandwiched between an electrolyte-impregnated matrix with a thickness of 1 mm or less, and a fuel gas such as hydrogen gas is supplied to the fuel electrode, and an oxidizer An oxidant gas such as air is supplied to the electrodes, and the electrochemical reaction that occurs at this time is used to extract electrical energy from between the two electrodes.
As long as the above fuel gas and oxidant gas are supplied, electrical energy can be extracted with high conversion efficiency.

In such fuel cells, fuel gas or oxidant gas easily permeates due to the pressure difference between the fuel electrode and the oxidizer electrode, which not only reduces the power generation efficiency but also accelerates the deterioration of the device. It turns out. Furthermore, it has been confirmed that if this interelectrode differential pressure exceeds a certain permissible value, the matrix constituting the fuel cell will be damaged. On the other hand, a fuel cell requires a high degree of load followability in its operating method, so it is necessary to ensure appropriate gas flow rates at the fuel electrode and oxidizer electrode in response to load fluctuations. Therefore, as a device for controlling the pressure and quantity in such a fuel cell, it is necessary to suppress the differential pressure between the electrodes to maintain the system, and to control the gas flow rates at the fuel electrode and oxidizer electrode to ensure load responsiveness. control is required at the same time.

By the way, in order to perform control that satisfies such requirements, it is generally necessary to operate a plurality of flow control valves. Conventionally, each gas flow rate of the fuel electrode and oxidizer electrode was controlled by each flow control valve provided on the supply line of fuel gas and oxidant gas to the fuel cell, and also on the discharge line of fuel gas and oxidant gas. Proportional and integral (P, T) operations are performed on the differential pressure between the fuel electrode and the oxidizer electrode by the respective flow control valves provided in the P.

It has a total of four independent units each controlled by 111 nodes, and is a single combination of all individual output control systems in which the control unit and the operation target correspond one-to-one. However, the problem with such a method is that
The two flow control valves can only be operated independently.

In other words, the flow rate and pressure of gas in a fuel cell follow a physical relationship, and the fuel electrode and oxidizer electrode are connected at the pressure difference between the electrodes for control purposes, so this control object, which has four operation objects, is In the end, it turns out that it is a mutual interference system with multiple input inputs and multiple outputs. Therefore, in the control configuration as described above, P,
A total of eight design parameters for the I controller should originally be set in consideration of their mutual relationships, but with such conventional control methods, it is not possible to set the parameters in a mutually coordinated manner, and in the end, Since the settings are made for each operation target through trial and error, the control performance of the control system as a whole is extremely poor.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and its purpose is to optimally adjust the four flow control valves that are to be operated in coordination with each other, and to control the load fluctuation of the fuel cell. Highly reliable fuel cell power generation equipped with a pressure flow control device with good control performance that can improve response to pressure differences between the fuel electrode and the oxidizer electrode, as well as system integrity with respect to the differential pressure between the fuel electrode and the oxidizer electrode. The goal is to provide a system.

[Summary of the Invention] In order to achieve the above object, the present invention comprises a pair of electrodes, a fuel electrode and an oxidizer electrode, which are arranged with a matrix impregnated with an electrolyte sandwiched therebetween. In a fuel cell in which an oxidant gas is supplied to each electrode and electrical energy is extracted from between the two electrodes through an electrochemical reaction that occurs, a fuel cell is provided on a fuel gas supply line and a discharge line for the fuel cell, respectively. a first flow control valve and a second flow control valve; a third flow control valve and a fourth flow control valve provided on the supply line and discharge line of the oxidant gas to the fuel cell, respectively; a first flow ω detector and a second flow rate detector that detect the gas flow rates passing through the fuel gas and oxidizing gas supply lines, respectively; a pressure detector that detects the pressure of the fuel electrode; and a pressure detector that detects the pressure of the fuel electrode; and the oxidizer electrode (interelectrode pressure difference); The detection signals from the "second flow" detector and the pressure detector, the target value signals corresponding to these detection signals, and the detection signal from the differential pressure detector are respectively inputted, and the detection signals from the "second flow" detector and the pressure detector are respectively input. For each comparison signal obtained by comparing and calculating each detection signal from the second flow rate detector and the pressure detector and each target value signal corresponding thereto, and the detection signal from the differential pressure detector, respectively. Steady characteristic compensation for obtaining first valve opening command signals corresponding to each of the first to fourth flow rate control valves by performing different proportional calculations, synthesizing these respective proportional calculation signals, and performing integral calculations. Department,
and each detection signal from the pressure detector, the differential pressure detector, and each valve opening detection signal of the first to fourth flow control valves are respectively input, and the detection signal from the pressure detector and the differential pressure detection are input. Different proportional calculations are performed on the comparison signal obtained by comparing the detection signal from the pressure sensor, the detection signal from the pressure sensor, and each valve opening detection signal.

and a transient characteristic compensator for synthesizing each of these proportional calculation signals to obtain a second valve opening command signal corresponding to each of the first to fourth flow m control valves; Each signal obtained by separately synthesizing each first valve opening command signal and each second valve opening command signal from the transient characteristic compensator is applied to the first to fourth flow rate control valves. By being equipped with an optimal calculation device that outputs a valve opening command signal, the fuel electrode flow rate and oxidizer electrode waterfall basin can be made to follow their respective target values without offset, and the differential pressure between the electrodes can be adjusted to the flow rate change of the 8 poles and disturbances. It is characterized by instantaneously regulating the input to zero.

First, the basic idea that is the premise of the present invention will be described.

FIG. 3 is a block diagram schematically showing a configuration example of a control system applied to the present invention. In other words, this control system performs a proportional (H) calculation on the deviation lie, which is a comparison signal obtained by comparing the control 0Ily from the process and the corresponding target value r, and On the other hand, there is a steady characteristic compensator that performs an integral (S) operation to obtain the first manipulated variable for the process, and a state quantity x from the process.
The proportional (G) operation is performed on the second
and a transient characteristic compensator that obtains the manipulated variable of the process. The configuration is such that it is given as lu.

Here, G is the process characteristic improvement factor, H is the integral (S)
Together with the elements, they are elements that compensate for steady-state values, and each form a matrix. And this G which is a control parameter
, H are determined as follows. That is, in FIG. 3, the control amount y and the state amount X. Production weight, target value r, width deviation e
are vectors each having appropriate elements. Then, the process is a linear model X-AX+Bu... (1a) y-cx
......When described in (1b), the evaluation index J-f (efi' Qe+uTRQ) dt with appropriate weight matrices Q and R is given.
The control law that minimizes (2) is
-Gx+Hf" edt+ua...13)
The coefficient matrices G and H at this time are (1a)
, (1b), and (2) can be given as a unique solution from the coefficient matrix of equations. From the above, since this control system implements a control method based on the state space method, the settings of the control parameters G and H can be determined mathematically so as to satisfy certain optimal conditions. Note that in the above, the cross represents the differential (d/dt), T represents the vertical matrix, and un represents the initial value of the manipulated variable U, respectively.

[Embodiments of the invention]

An embodiment of the present invention based on the above concept will be described below with reference to the drawings. FIG. 1 shows in block form an example of the configuration of a fuel cell power generation system equipped with a pressure flow rate optimum control device according to the present invention.

In the figure, 1 consists of a pair of N electrodes, a fuel electrode 2 and an oxidizer electrode 3, arranged with an electrolyte-impregnated matrix in between, and the fuel electrode 2 is supplied with a fuel gas such as hydrogen, and the oxidizer electrode 3 is supplied with a fuel gas such as hydrogen, etc. This is a fuel cell in which oxidizing gases are supplied to each electrode, and electrical energy is extracted from between the two electrodes 2 and 3 through the electrochemical reaction that occurs at this time. On the other hand, 4A and 4B are a first flow control valve and a second flow control valve provided on the fuel gas supply line and discharge line for the fuel cell 1, respectively, and 4C and 4D are oxidant gas for the fuel cell 1, respectively. a third flow control valve and a fourth flow control valve provided on the supply line and the discharge line, respectively, of 51A and 51;
B is a first in detector and a second flow rate detector that respectively detect the gas flow rates passing through the fuel gas and oxidant gas supply lines; 52 is a pressure detector that detects the pressure of the fuel electrode 2; Reference numeral 53 denotes a differential pressure detector for detecting the differential pressure between the fuel electrode 2 and the oxidizer electrode 3. Reference numeral 31 denotes an optimal calculation device whose details will be described later, and each detection signal FAND from the first flow rate detector 51A, second flow rate detector 51B, and pressure detector 52.

FCAT, PAND and their detection signals FAND, F
cxv, each target value signal F*AND corresponding to PAND,
F*CAT, P*AND, the detection signal DP1 from the differential pressure detector 53, and each valve opening detection signal ■1 to v4 of the first to fourth flow control valves 4A to 4D are input, respectively. Based on the signal, the first to fourth flow control valves 4A to 4D
The optimum valve opening command signals u1 to U4 are output for each of the valve opening command signals u1 to U4.

Next, FIG. 2 shows a detailed configuration example of the optimal arithmetic unit 31. In Figure 2, 231.232,2
33 is a first flow rate detector 51A.

Each detector @FAND, FCAT, PAND and each target value signal F* from the second flow rate detector 51B and pressure detector 52
Adder/subtractor that compares AND, F*OAT, and P*AND separately to obtain a deviation signal, 241, 242.24
3 and 244 perform different proportional calculations (hil, h12. h13. h14. h2) on these deviation signals and the detection signal DP from the differential pressure detector 53, respectively.
1. h31. h41. ....

The adders/subtractors 211, 212, 213, and 214 which synthesize the respective proportional operation signals obtained by performing the above-mentioned adder/subtractors 241, 242, 243, and 224 integrate (S) the output signals from the respective adders/subtractors 241, 242, 243, and 224, and perform the above-mentioned This is an integrator that obtains a first valve opening command signal corresponding to each of the first to fourth flow rate control valves 4A to 4D, and these elements constitute a steady-state characteristic compensator. Further, 22 is the pressure detector 5
251, 252; 253 and 254 are the pressure detectors mentioned above; 251, 252; 253 and 254; Detection signal from 51 PA pi
o, deviation signal Pc AT from the adder/subtractor 25
, different proportional calculations (qll, Q12°Q13.014.
Q15. Q16. Q21. Q31. Q41.・
....

an adder/subtractor that synthesizes each proportional calculation signal obtained by performing (oij) and obtains a second valve opening command signal corresponding to each of the first to fourth flow rate control valves 4A-40, Each of these elements constitutes a transient characteristic compensator. Then, each of the first valve opening degree command signals from the steady-state characteristic compensation section and each of the second valve opening degree command signals from the transient characteristic compensation section are separately synthesized by adders and subtractors 261 to 264. A so-called multi-input multi-output control configuration is adopted in which each signal is output as valve opening command signals u1 to u4 for the first to fourth flow rate control valves 4A to 4D. Note that in the above, Qij
(i = 1.2, 3.4, j = 1.2.3°4), hij
(i=1.2.3.4, j=1.2°3.4.5.6)
represent proportional gains, which form a matrix and correspond to G and H in FIG. 3 described above.

Next, the operation of the fuel cell power generation system using the pressure flow optimization control device constructed as described above will be described.

First, in FIG. 1, by supplying a fuel gas such as hydrogen to the fuel electrode 2 and an oxidant gas such as air to the oxidizer electrode 3 according to the load amount of the fuel cell 1, these are electrochemically In response to this, electrical energy is extracted from between the two electrodes 2.3 to generate electricity. In addition, each detection signal FAND, FCAT, PAND from the first flow rate detector 51A, second flow rate detector 51B, and pressure detector 52, and each target value signal corresponding to these detection signals FAND, FCAT, and PAND. F*AND, F*CAT.

P*A No, detection signal DP from differential pressure detector 53
.

The valve opening detection signals V1 to V4 of the first to fourth flow rate control valves 4A to 4D are input to the optimum calculation device 31, respectively.

Now, if the load amount of the fuel cell 1 changes from this state,
Optimal calculation! Since 131 has a multivariable control configuration as described above, the first valve opening degree command obtained by the steady-state characteristic correction section is determined by changing any one input signal as the load of the fuel cell 1 changes. At least one of the signal and the second valve opening command signal obtained by the transient characteristic correction section changes under the influence thereof. As a result, the final valve opening command signals u1 to u4 obtained by the adjusters 261 to 264 also change, and the first flow mountain control valve 4A, the second FIL pot control valve 4B, and the third flow rate control The respective valve opening degrees of the valve 4C and the fourth flow control valve 4D are optimally controlled while cooperating with each other. As a result, the gas flow rate FAND of the fuel electrode 2 and the gas flow rate 1IFc A of the oxidizer electrode 3 are determined.
r follows the respective targets 1i1F*ANn and F*CAT without offset, and the differential pressure DP between the fuel electrode 2 and oxidizer electrode 3 is instantly regulated to zero in response to flow rate changes and disturbance inputs in winter. will be done. Therefore, the responsiveness of the fuel cell 1 to load fluctuations is improved, and
It is now possible to improve the system integrity with respect to the interelectrode pressure difference DP between the fuel electrode 2 and oxidizer electrode 3, resulting in an extremely reliable fuel cell power generation system equipped with a pressure flow rate optimization control device with good control performance. Obtainable.

In addition, in Figure 4, the load on the fuel cell 1 is changed from 50% to 100%.
This shows the response when the target value is raised stepwise to 0. Since the target values are all held at their initial values, the deviation quickly converges to zero as shown by the solid line. As is clear from the figure, the fluctuation range is reduced and the convergence is faster compared to the conventional control shown by the broken line. Further, FIG. 5 shows the response when the target gas flow rate value F*AND of the fuel electrode 2 of the fuel cell 1 is increased in steps. From the figure, it can be seen that the gas flow IFAND of the fuel electrode 2 quickly reaches the target value as shown by the solid line, while the gas flow IFO of the oxidizer electrode 3 quickly reaches the target value as shown by the solid line, whereas the conventional control shown by the broken line fluctuates greatly.
It can be seen that NT and the interelectrode differential pressure DP hardly change and are maintained at almost zero as shown by the solid line.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without changing the gist thereof.

〔Effect of the invention〕

As explained above, according to the present invention, the four flow rate III valves to be operated are optimally adjusted in coordination with each other, improving the response to load fluctuations of the fuel cell, and improving the fuel electrode and oxidation Till[
An extremely reliable fuel cell power generation system equipped with a pressure control device with good performance can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG.
The figure is a block diagram showing the details of the optimal arithmetic unit in the same embodiment, FIG. 3 is a schematic diagram for explaining the present invention in detail, and FIG.
This figure and FIG. 5 are diagrams for explaining the operation of the same embodiment. DESCRIPTION OF SYMBOLS 1... Fuel cell, 2... Fuel electrode, 3... Oxidizer electrode, 31... Optimal performance WI device, 4A to 4D... First to
Fourth flow layer control valve, 51A, 51B...first. Second flow rate detector, 52... Pressure detector, 53... Differential pressure detector, 211-214... Integrator, 22.231-2
33°241~244.251~254°261~264...addition/subtraction device. Applicant's representative Patent attorney Takehiko Suzue Figure 1 1 Bacteria 506 mu 100
figure

Claims (1)

[Claims] (1) A pair of electrodes, a fuel electrode and an oxidizer electrode, are arranged with an electrolyte-impregnated matrix in between, and the electricity generated by supplying fuel gas to the fuel electrode and oxidant gas to the oxidizer electrode, respectively. In a fuel cell that extracts electrical energy from between two electrodes through a chemical reaction, a first flow control valve and a second flow control valve are provided on a supply line and a discharge line of fuel gas to the fuel cell, respectively. a third flow control valve and a fourth flow control valve provided on the oxidant gas supply line and discharge line for the fuel cell, respectively; and gas passing through the fuel gas and oxidant gas supply lines. The first one detects the flow rate respectively.
a flow rate detector and a second flow rate detector, a pressure detector that detects the pressure of the fuel electrode, and a pressure difference that detects the differential pressure between the fuel electrode and the oxidizer electrode (interelectrode differential pressure). Each detection signal from the detector, the first and second flow rate detectors, and the pressure detector, each target value signal corresponding to these detection signals, and the detection signal from the differential pressure detector are respectively input, and the 1st, 2nd
Each comparison signal obtained by comparing each detection signal from the flow rate detector and the pressure sensor with each corresponding target value signal and the detection signal from the differential pressure detector, respectively, is different. A proportional calculation is performed, and each of these proportional calculation signals is combined and an integral calculation is performed to obtain the first to fourth signals.
a steady-state characteristic compensation unit that obtains a first valve opening command signal corresponding to each of the flow rate control valves, and each detection signal from the pressure detector and the differential pressure detector and the first to fourth flow rate control valves; A comparison signal obtained by comparing and calculating the detection signal from the pressure detector and the detection signal from the differential pressure detector with each valve opening detection signal as input, and the detection signal from the pressure detector, respectively. Different proportional calculations are performed on the valve opening detection signals, and these proportional calculation signals are combined to generate a second valve opening command signal corresponding to each of the first to fourth flow rate control valves. the first valve opening command signal from the steady characteristic compensator and the second valve opening command signal from the transient characteristic compensator, respectively. and an optimum arithmetic unit that outputs each signal as a valve opening command signal for the first to fourth flow rate control valves.