JPS63292576A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To improve the controllability of the reforming vapor flow by calculating the unbalance quantity of the transient cell cooling heat quantity based on the load command applied to a system. CONSTITUTION:A correction quantity arithmetic means constituted of two generated heat function generators 11-1, 11-2 calculating the cell generated heat quantity for the load command applied to a system, a delay arithmetic unit 12 delay-calculating the calculation value calculated by one generated heat function generator 11-2, and a dimension conversion coefficient multiplier 13 proportionally calculating the deviation signal DELTAQ between the calculation value from this delay arithmetic unit 12 and the calculation value from the other generated heat function generator 11-1 to generate the feed-forward signal is added. The feed-forward signal calculated by this correction quantity arithmetic means is added to the pressure target value signal Pref of a cell cooling system as its correction signal. The unbalance quantity of the transient cell cooling heat quantity from the load command applied to this fuel cell power generating system is calculated, and the feed-forward signal is generated based on it. The controllability of the reforming vapor flow is thereby improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel cell power generation system equipped with a battery cooling system, and in particular, the separator pressure of the battery cooling system in response to system load changes. This invention relates to a fuel cell power generation system that is capable of improving controllability.

(Prior Art) Fuel cells are conventionally 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, with an electrolyte layer in between, and supplies fuel gas to the fuel electrode and oxidizer gas to the oxidizer electrode, and the electricity generated at this time. Electrical energy is extracted from between the two electrodes using a chemical reaction, and electrical energy can be extracted with high conversion efficiency as long as the fuel gas and oxidant gas are supplied. .

Now, fuel cells currently being considered include fuel cells using hydrazine as fuel, alkaline aqueous electrolyte, and phosphoric acid aqueous electrolyte as the electrolyte. Fuel cells of this type can be used in general because they can use reformed gas, and are increasingly being used for industrial or power generation purposes.

This type of fuel cell is equipped with a fuel reformer for reforming raw fuel gas with steam to obtain reformed gas, and the reformed gas obtained by this fuel reformer is used as fuel gas to fuel the cell. In addition, a cell cooling system with a separator is installed, and the cooling water in a two-phase flow state after absorbing the heat generated by the electrochemical reaction in the fuel cell is separated into water vapor and saturated water through the separator. In many cases, a fuel cell power generation system is configured to separate this water vapor into a fuel reformer and supply this water vapor as reforming water vapor to a fuel reformer.

FIG. 3 shows an example of such a fuel cell power generation system.

In FIG. 3, 1 is a fuel reformer that steam-reforms methane as raw fuel gas to produce reformed gas containing a large amount of hydrogen, and 2 is a fuel reformer that produces reformed gas containing a large amount of hydrogen. A fuel cell in which gas is introduced into the fuel electrode as a fuel gas and oxidizing gas is introduced into the oxidizing electrode, respectively, and electrical energy is extracted from between the two electrodes by the electrochemical reaction that occurs at this time, and 3 is a part of the cell cooling system. This is the separator that makes up the .

That is, the cooling water supplied to the fuel cell 2 absorbs the heat generated by the electrochemical reaction in the cell, and becomes a two-phase flow state at its outlet. A separator 3 in the battery cooling system separates this cooling water into water vapor and saturated water. This separated water vapor is then supplied to the fuel reformer 1 and used as reforming water vapor.

Now, in a fuel cell power generation system equipped with such a battery cooling system, fluctuations in energy within the battery cooling system first appear as pressure fluctuations in the separator 3. For this reason, proportional-integral (hereinafter referred to as PI) control has conventionally been used as a means for controlling the pressure of the separator 3. That is, as shown in FIG. 3, the deviation between the pressure detection signal from the pressure detector 4 that detects the internal pressure of the separator 3 and the pressure target value signal p ref is introduced into the PI calculator 5, and this deviation is The PI calculator 5
It performs control calculations and outputs a heat amount operation signal U. In addition, as an operation end for the amount of heat, a heater 8 connected to a power source 7 via a variable resistor 6 is used for operation in the positive direction.
As a negative direction operation, a hot stone control valve 9 is used to adjust the vent amount of water vapor inside the separator 3. Therefore,
The heat amount operation signal U from the PI computing unit 5 is determined as positive or negative by the positive/negative discriminator 10 and branched, and its absolute value is given to each operation terminal to supply or remove heat from the battery cooling system. It looks like this.

As mentioned above, the role of the cell cooling system in such a fuel cell power generation system is not only to prevent the fuel cell 2 from overheating, but also to supply reforming steam to the fuel reformer-〇-1. There are things to do. This reforming steam flow rate is determined based on the load state of the fuel cell power generation system.

Therefore, a change in the load on the fuel cell power generation system directly causes a change in the flow rate of the reforming steam, which in turn affects the pressure in the separator 3 of the cell cooling system. That is, when the load increases, the pressure in the separator 3 tends to decrease, and conversely, when the load decreases, the pressure in the separator 3 tends to increase. and.

This fluctuation in the pressure of the separator 3 is caused by the flow of reforming steam ω
This will have an adverse effect on control as a variation in process gain.

(Problems to be Solved by the Invention) As described above, in the conventional fuel cell power generation system, the controllability of the separator pressure in the battery cooling system in response to system load fluctuations is poor, and as a result, the separator pressure is There was a problem in that the controllability of the reforming steam flow rate to the pressure was reduced, and the stability of the system as a whole was reduced.

The present invention was made in order to solve the above-mentioned problems, and its purpose is to improve the controllability of the separator pressure of the battery cooling system in response to system load fluctuations, and to quickly absorb the fluctuations in separator pressure. It is an object of the present invention to provide a highly stable fuel cell power generation system that can match a target value and thereby improve the controllability of the reforming steam flow rate.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a fuel reformer that generates reformed gas by reforming raw fuel gas with steam; A fuel cell is a fuel cell in which the reformed gas obtained in a fuel reformer is introduced as a fuel gas into a fuel electrode, and the oxidizing gas is introduced into an oxidizing electrode, and electrical energy is extracted from between the two electrodes through the electrochemical reaction that occurs. After absorbing the heat generated by the electrochemical reaction in the fuel cell, the two-phase cooling water is separated into steam and saturated water, and the separated steam is sent to a fuel reformer for reforming. In a fuel cell power generation system comprising a battery cooling system equipped with a separator supplied as water vapor, a pressure detection means for detecting the internal pressure of the separator, and a pressure detection signal and a pressure target value signal from the pressure detection means are provided. control calculation means that takes as input, performs control calculations so that the deviation of each of these signals becomes zero, and outputs a heat amount manipulation signal; Alternatively, calculate the transient unbalanced amount of heat in the battery cooling system from the heat amount operation signal for heat removal and the load command given to the system, generate a feedforward signal based on this, and convert this feedforward signal into pressure The present invention is characterized in that it includes a correction amount calculation means for adding a correction signal to the target value signal or the heat amount operation signal.

(Function) In the above fuel cell power generation system, the feedforward signal obtained based on the transient unbalanced amount of heat in the battery cooling system calculated from the load command given to the system is the pressure target value signal of the battery cooling system. Alternatively, since it is added to the heat amount operation signal as a correction signal, the imbalance in the heat balance due to the delay in the fluctuation of generated heat within the fuel cell is corrected.
This reduces the variation in separator pressure with respect to load changes.

(Example) First, the concept of the present invention will be described.

When controlling the pressure of the separator in the battery cooling system, the reason for the delay in control response is that it relies only on feedback control. Therefore, in the present invention, the amount of change in the amount of heat generated by the battery due to a change in the load of the fuel cell power generation system is calculated, and this is used as feedforward control in separator pressure control. That is, based on the load command given to the fuel cell power generation system, the amount of change in the amount of heat generated by the battery is calculated in advance, and this heat change calculation 14iff is calculated in advance.
i is applied in advance to the heat quantity control end of the battery cooling system.

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 according to the present invention. The same parts as in FIG. state In other words, in Fig. 1, there are two heat generation function generators 11-1 and 11-2 that calculate the amount of heat generated by the battery in response to the load command given to the system, and one heat function generator 11-2. A delay calculator 12 that calculates a calculated value with a delay (transfer function: 1/(1+TS)), a calculated value from this delay calculator 12, and a calculated value from the other generated heat function generator 11-1. A correction amount calculation means consisting of a dimensional conversion coefficient unit 13 which performs a proportional operation (gain K) on the deviation (calorific value deviation) signal ΔQ and generates a feedforward signal is added to FIG. 3, and by this correction amount calculation means, The calculated feedforward signal is added to the pressure target value signal p ref of the battery cooling system as its correction signal. That is, this correction amount calculation means calculates the transient unbalanced amount of heat in the battery cooling system from the load command given to the present fuel cell power generation system, and generates a feedforward signal based on this.

Next, the operation of the fuel cell power generation system equipped with such correction amount calculation means will be explained.

In FIG. 1, two heat function generators 11-1.1
1-2, the amount of heat generated by the battery relative to the load command given to the system is calculated. On the other hand, actual fluctuations in heat input to the battery cooling system are accompanied by a time delay with respect to the load command. This is related to the dynamic characteristics from the load command to the variation in the amount of heat generated by the current output 2 to the variation in the amount of heat absorbed by the battery cooling water due to heat transfer. Therefore, the above-mentioned time delay is simulated by performing a delay calculation on the calculation value calculated by one of the generated heat function generators 11-2 in the delay calculation unit 12. Then, the deviation between the calculated value from the delay calculator 12 and the calculated value from the other generated heat function generator 11-1 is taken, that is, the difference between the amount of heat without delay and the amount of heat with delay is taken. Thus, the heat amount deviation at the time of calculation is calculated. This heat amount deviation is an amount of imbalance in the thermal energy balance of the battery cooling system. Therefore, the deviation signal ΔQ, which is equivalent to the heat amount deviation, is
Proportional calculation is performed in step 3 to generate a feedforward signal,
By adding this feedforward signal in advance as a correction signal to the input part of the pressure target value signal prer of the battery cooling system, the heater 8 or the flow rate regulating valve 9, which is the heat quantity control end of the battery cooling system, can be controlled. It can speed up the operation.

As described above, in the fuel cell power generation system according to the present embodiment, the feedforward signal obtained by the correction amount calculation means is based on the transient unbalanced amount of heat in the battery cooling system calculated from the load command given to the system. is added as a correction signal to the pressure target value signal P ref of the battery cooling system, so that the imbalance in the heat balance due to the delay in the fluctuation of generated heat within the fuel cell 2 is corrected.
This improves the controllability of the pressure in the separator 3 with respect to changes in the system load and suppresses pressure fluctuations to a small level. As a result, the controllability of the reforming steam flow rate in the fuel reformer 1, which uses the pressure of the separator 3 as the source pressure, is also improved, making it possible to realize a system with good overall stability.

It should be noted that the present invention is not limited to the embodiments described above, but can also be implemented in the following manner.

FIG. 2 shows in block form an example of the configuration of a part of a fuel cell power generation system according to another embodiment of the present invention, and the same parts as in FIG. Only the different parts will be described here.

That is, FIG. 2 shows a heat generation function generator 14 that calculates the amount of heat generated by the battery in response to a load command given to the system as the above-mentioned correction amount calculation means, and Lead/lag calculation unit 15 based on lead/lag calculation (transfer function: TS/ (1+TS))
and a dimension conversion coefficient unit 16 which performs a proportional calculation (gain K) on the calculated value ΔQ from the lead/lag calculation unit 15 to generate a feedforward signal, and the correction amount calculation means calculates the The feedforward signal is already added to the heat quantity operation signal U of the battery cooling system as its correction signal. The fuel cell power generation system shown in FIG. 2 also provides the same effects as described above.

〔Effect of the invention〕

As explained above, according to the present invention, the transient unbalanced amount of heat in the battery cooling system is calculated from the load command given to the system, a feedforward signal is generated based on this, and the feedforward signal is and a correction amount calculating means that adds the correction signal to the pressure target value signal or the heat amount operation signal, so that the controllability of the separator pressure of the battery cooling system in response to system load fluctuations is improved, and the separator pressure It is possible to provide a highly stable fuel cell power generation system that can quickly absorb fluctuations in the target value to match the target value, thereby improving the controllability of the reforming steam flow.

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram showing one embodiment of the fuel cell power generation system according to the present invention, FIG. 2 is a configuration block diagram showing another embodiment of the fuel cell power generation system according to the present invention, and FIG.
The figure is a configuration block diagram showing a conventional fuel cell power generation system. DESCRIPTION OF SYMBOLS 1... Fuel reformer, 2... Fuel cell, 3... Separator, 4... Pressure detector, 5... PI calculator,
6... Variable resistance, 7... Power supply, 8... Heater,
9...Flow control valve, 10...Positive/negative discriminator, 11-1
．． 11-2... Generated heat function generator, 12... Delay calculator, 13... Dimensional conversion coefficient unit, 14... Generated heat function generator, 15... Lead/delay calculator, 16. ...Dimension conversion coefficient unit.

Claims (3)

[Claims] (1) A fuel reformer that reformes raw fuel gas with steam to generate reformed gas, and the reformed gas obtained by this fuel reformer is used as a fuel gas to be supplied to the fuel electrode and oxidizes the oxidizing gas. A fuel cell that extracts electrical energy from between the two electrodes through the electrochemical reaction that occurs when the agent is introduced into each electrode, and cooling in a two-phase flow state after absorbing the heat generated by the electrochemical reaction in this fuel cell. A fuel cell power generation system comprising a cell cooling system equipped with a separator that separates water into steam and saturated water and supplies the separated steam to the fuel reformer as reforming steam, A pressure detection means for detecting the internal pressure of the separator, a pressure detection signal from this pressure detection means and a pressure target value signal are input, and a control calculation is performed so that the deviation of each of these signals becomes zero, thereby controlling the amount of heat. A control calculation means for outputting a signal; a heat amount operation means for supplying or removing heat from the battery cooling system based on a heat amount manipulation signal from the control calculation means; A correction amount calculating means for calculating an unbalanced amount of heat in the cooling system, generating a feedforward signal based on the unbalanced amount, and adding the feedforward signal to the pressure target value signal or the heat amount operation signal as a correction signal thereof. A fuel cell power generation system characterized by comprising: (2) The correction amount calculation means generates, as a feedback signal, a deviation signal between the calculated value of the battery generated heat amount in response to the load command given to the system and the calculated value obtained by performing a delayed calculation on the battery generated heat amount calculated value. A fuel cell power generation system according to claim (1), characterized in that: (3) A patent claim characterized in that the correction amount calculation means generates, as a feedback signal, a calculated value signal obtained by performing a lead/lag calculation on the calculated value of the amount of heat generated by the battery in response to a load command given to the system. The range of (
The fuel cell power generation system described in section 1).