JPS6180761A - Control system of fuel cell power generation system - Google Patents

Abstract

PURPOSE:To enable immediate and accurate response to load variation, by controlling constant the system backpressure and the compressor discharge pressure in a feedback control, as well as controlling burning of the auxiliary furnace and opening of nozzle of the turbine in a feedforward control depending on a program. CONSTITUTION:In an ordinary operation, the discharge pressure of the compres sor 3b is controlled constant by burning control of the auxiliary furnace 27 so as to control to minimize energy loss as far as the turbine power is not lost. On the other hand, when the system load is changed, the burning control of the auxiliary furnace 27 and opening control of nozzle 3c of the turbine 3a are feedforward-controlled depending on a preset program. In this case, at the same time, a constant exhaust gas pressure of the system is feedback- controlled by a turbine bypass valve 4. However, a temporary increase of the system exhaust gas and the compressor discharge in a transition stage are discharged to the air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a load control method for a fuel cell power generation system equipped with a turbo compressor.

(b) Conventional fuel cell power generation systems can achieve higher thermal efficiency than steam power generation systems that use oil, coal, etc. as fuel, and are also environmentally friendly and have flexibility in terms of location. are doing. Therefore, in recent years, various uses are being considered not only as power sources for special purposes such as space exploration, but also as power sources for commercial power, and development is becoming more active with the aim of putting them into practical use.
1. A fuel cell power generation system consists of a fuel cell that has an electrolyte layer interposed between an air electrode and a hydrogen electrode, and hydrogen gas that is produced by reforming a hydrocarbon fuel such as natural gas and serves as fuel for the hydrogen electrode. and an air supply means for supplying air to the air electrode and the reformer. and,
The performance of the fuel cell tends to improve as the pressure of each reaction gas increases. Therefore, the operating pressure of each of the reaction gases is set to a value of about 4 to 6 kg/cta2g, for example. At this time, compressing the air requires a large amount of power, which amounts to about 20% of the energy generated by the battery. On the other hand, the reforming reaction for producing fuel gas for the battery is carried out at a high temperature of about 800° C., and high temperature exhaust gas is discharged from the reformer.

Therefore, if the power to compress the air can be found in the exhaust gas energy of the system.

This has a great effect on improving system efficiency.

Due to these circumstances, recent fuel cell power generation systems
It has become common to use a turbo compressor as the air supply means. That is, the turbo compressor includes a turbine driven by surplus air at the outlet of the air electrode of the fuel cell and exhaust gas from the reformer, and a turbine that is directly connected to the turbine and is energized by the turbine to drive the fuel cell and the reformer. It is equipped with a compressor that supplies the necessary compressed air, and the energy contained in the exhaust gas, etc. is recovered by a turbine and used to compress the air, improving system efficiency. .

Incidentally, in such a fuel cell power generation system, wide and quick load response control is required as a so-called power generation system. Therefore, the amount of air supplied to the fuel cell and the reformer is required to be controlled in a range of, for example, 25 to 100%. On the other hand, the pressure of the air supplied to the fuel cell is adjusted even during load fluctuations in order to maintain the characteristics of the fuel cell and to suppress the differential pressure with the fuel side pressure to prevent gas leakage between the two electrodes, that is, the crossover phenomenon. Control to maintain a constant value is required.

As a specific method, a conventional example proposed in Japanese Unexamined Patent Publication No. 58-12268 is shown in FIG. In the figure, 1 is a fuel cell, and 1a, 1b, and 1c indicate an air electrode, a fuel electrode, and an electrolyte portion of the fuel cell 1, respectively. Reference numeral 2 denotes a reformer for converting hydrocarbon fuel into hydrogen-rich gas, and 2a and 2b indicate the eighth section and reaction section of the reformer 2. 3 is a turbo compressor, 3a and 3b indicate a turbine part and a compressor part of this turbo compressor @ 3, 4.5.6 is a compressor, a mechanism for controlling the discharge pressure, and 4 is a mechanism for regulating the pressure. Atmospheric release valve for,
5 indicates a pressure transmitter, 6 indicates a pressure controller, 7.8
．． 9 is a flow rate adjustment mechanism for adjusting the amount of air supplied to the fuel cell, 7 is a flow iyAm valve, 8 is a flow rate transmitter, and 9 is a flow rate controller. 10 is an air supply pipe (compressor discharge pipe) that guides air from the compressor 3b to the fuel cell l; 11 is an excess air pipe that guides exhaust air from the fuel cell air electrode 1a to the turbine 3a; and 12 is a reformer burner section 2a. A combustion exhaust gas pipe 13 is connected to the turbine 3 after the surplus air pipe 11 and the combustion exhaust gas pipe 12 join together.
A system exhaust gas pipe 14 is a pipe open to the atmosphere until it is introduced into a. Further, 15, 16, and 17 are mechanisms for controlling the reaction air pressure of the fuel cell 1, 15 is a pressure m regulating valve, 16 is a differential pressure transmitter that detects the differential pressure between the compressor discharge pressure and the reaction air pressure, 17 indicates a pressure controller, 18, 19, and 20 a mechanism for controlling the reaction fuel gas pressure of the fuel cell l, 18 a pressure regulating valve, and 19 detecting the differential pressure between the reaction air pressure and the reaction fuel gas pressure. 20 is a pressure controller. 21 is a fuel supply pipe to the reforming reaction section 2b, 22 is a fuel cell fuel electrode 1b
The reformed gas supply pipe 23 is a surplus fuel supply pipe that supplies surplus fuel from the fuel cell 1 to the reformer burner section 2a. 24, 25, and 26 are mechanisms for adjusting the amount of fuel to the reformer reaction section 2b, 24 is a flow control valve, 25 is a flow transmitter, and 26 is a flow controller. - Although omitted in the conventional example of No. 12268, it is branched from the air supply piping 10 to the reformer burner section 2a.
A burner air supply pipe for combustion is added to FIG.

The operation at the time of load fluctuation described in such a conventional example will be explained. In the process of reducing the load on the fuel cell 1, the compressor discharge pressure also decreases as the amount of air supplied to the compressor 3b decreases. We are trying to maintain it. First, in the range from the rated load to a certain load range, the compressor discharge pressure is kept constant by the throttle y4m of the atmosphere release valve 4, and the reaction air pressure is maintained. In the range below the load range where there is no adjustment allowance for the atmospheric release valve 4, the reaction air pressure is linked to the decrease in the compressor discharge pressure, that is, the pressure regulating valve 15 maintains the differential pressure of the reaction air pressure with respect to the compressor discharge pressure. Also, the pressure regulating valve 18 controls and adjusts the differential pressure between the reaction fuel gas pressure and the reaction air pressure to keep it constant.

This makes it possible to stably supply air to the fuel cell, maintain the differential pressure between the reaction air and the reaction fuel gas, and prevent a crossover phenomenon from occurring. That is,
This system basically maintains a constant air pressure by adjusting the atmosphere release valve 4, but once the adjustment amount of the atmosphere release valve 4 is eliminated, the pressure of the reactant gas of the fuel cell decreases as the compressor discharge pressure decreases. This is an attempt to lower the

[Problems to be Solved by the Invention] However, such a conventional structure has a drawback that battery characteristics are not necessarily maintained for the following reason.

In other words, a fuel cell is usually installed in a case pressurized with nitrogen gas due to pressure-resistant seals of the manifolds for each reaction and gas attached to the cell body, and the nitrogen gas pressure is approximately equal to the reaction gas pressure. However, since the volume of nitrogen gas in the housing is large, it is difficult to change the nitrogen gas pressure in the housing to follow the rate of change in the reaction gas pressure. In other words, if the reactant gas pressure of the battery is changed during load fluctuations, a large pressure difference will occur between the battery's reaction gas pressure and the casing nitrogen gas pressure, causing the manifold seal to rupture and nitrogen gas leaking into the reactant gas, or vice versa. There is a problem in that gas leaks into the housing and deteriorates the characteristics of the fuel cell.

In addition, the conventional technology shown in Figure 1 does not actively control the system exhaust gas pressure, so there is a problem that it is difficult to quickly respond to load fluctuations, and if the load changes rapidly, the reformer There is a risk that the internal pressure of the reactor may temporarily fluctuate, impairing the stability of combustion, or that the reactant gas pressure of the fuel cell fluctuates, causing the aforementioned crossover phenomenon.

In addition, this system performs steady pressure control by adjusting the atmosphere release around the rated load, and it is assumed that the turbine power is surplus to the required power of the combination lever, but in the actual system, the turbine power is Since the power required by the compressor may be equal to or even insufficient, it is expected that control using the adjustment allowance of the atmosphere release valve will be difficult.

Turbine power shortage is particularly noticeable at partial loads.

The present invention was made with the aim of solving these problems all at once, and it does not cause the turbine to run out of power in any operating range, and also prevents combustion in the reformer from becoming unstable. The object of the present invention is to provide a control method for a fuel cell power generation system that can respond extremely quickly and accurately to a wide range of load fluctuations without causing the aforementioned deterioration of battery characteristics or the crossover phenomenon.

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a fuel cell power generation system equipped with the above-mentioned atmosphere release valve, in which the exhaust gas piping is connected to the turbine of the turbo compressor. An auxiliary combustion furnace is arranged to compensate for the insufficient power of the turbine. The amount of exhaust gas released into the atmosphere through the bypass pipe branched from the exhaust gas pipe leading to the turbine is: l! ! A turbine bypass valve is provided, and the turbine of the turbo compressor is of a variable nozzle type. Then, during steady operation of the system, the combustion amount of the auxiliary combustion furnace is controlled by feedback control with the turbine bypass valve and the atmosphere release valve fully closed or slightly opened so that the compressor discharge pressure remains within a certain range. (Or, in addition,
(The turbine bypass valve is controlled so that the system back pressure is within a certain range.) Also, when the system load fluctuates, the combustion control of the auxiliary combustion furnace and the turbine nozzle opening control are performed by feedforward control based on a program. The present invention is characterized in that a bypass valve performs feedback control to keep the system back pressure constant, and the atmosphere release valve performs feedback control to keep the compressor discharge pressure constant.

[Function] According to such a configuration, during steady operation, the turbine bypass valve and the atmosphere release valve are maintained in a fully closed or slightly open state, and the compressor discharge pressure is kept constant by combustion control of the auxiliary combustion furnace. energy loss is minimized to the extent that turbine power is not insufficient. On the other hand, when the load on the system fluctuates, the combustion control of the auxiliary combustion furnace and the nozzle opening control of the turbine are performed by feedforward control based on a preset program. In that case, at the same time, the turbine bypass valve performs feedback control to keep the system exhaust gas pressure constant, and the atmosphere release valve performs feedback control to keep the compressor discharge pressure constant, resulting in a temporary system exhaust gas amount during the transition period. The increased amount of air discharged from the compressor is discharged to the atmosphere. As a result of such control, the system back pressure and the compressor discharge pressure are always actively maintained at a constant value, and the pressure between each reactant gas in the fuel cell and the reactant gas pressure and the casing are constantly maintained. The differential pressure with the body nitrogen gas pressure can always be kept constant.

In addition, when the inlet pressure is constant, the power of the turbine is proportional to (inlet absolute temperature T) y and the nozzle area S, so when the load fluctuates, not only the combustion amount of the auxiliary combustion furnace is controlled, but also the nozzle area is controlled. By doing so, the turbine power can be increased to a desired value while keeping the turbine inlet temperature (exhaust gas temperature) relatively suppressed. Therefore, in combination with the fact that the system back pressure can be kept constant as described above, the time required to vary the load can be reasonably and reliably shortened.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 2 and 3.

Note that parts that are the same as or correspond to those shown in FIG. 1 are given the same symbols and their explanations will be omitted. Furthermore, the load 42 shown in FIG. 2 is a collective representation of the fuel cell 1, reformer 2, and related equipment shown in FIG.

In FIG. 2, reference numeral 27 indicates an auxiliary combustion furnace installed in the middle of the system exhaust gas pipe 13 to compensate for the lack of turbine power of the turbo pressure 1II engine 3, 28 indicates a fuel supply pipe for this auxiliary combustion furnace 27, and 29 indicates this fuel supply pipe 28. A fuel flow control valve 30 installed in the auxiliary combustion furnace is a fuel flow controller for detecting the fuel flow rate flowing through the fuel supply pipe 28 and adjusting the fuel flow control valve 29 . The turbo compressor 3 is
Unlike the one shown in FIG. 1, this is a so-called variable nozzle type in which a turbine 3a is equipped with a variable nozzle 3C. In the variable nozzle 3C, for example, as shown in Japanese Patent Application No. 58-103160, a valve body is driven by a stepping motor or the like operated by an electric signal, and the opening of the re-nozzle is controlled by the movement of the valve body. It is constructed in such a way that the area can be changed. The auxiliary combustion furnace 27 burns the fuel sequentially supplied from the fuel supply pipe 28 and imparts thermal energy to the exhaust gas flowing through the system exhaust gas pipe 13. Further, 31 is an air pipe branched from the air supply pipe 10 that guides air discharged from the compressor 3b of the turbo compressor 113 and connected to the auxiliary combustion furnace 27, and 32 is air for combustion in the auxiliary combustion furnace installed in this air pipe 31. A flow rate control valve 33 is an air flow controller for auxiliary combustion furnace combustion for detecting the air flow rate flowing through the air pipe 31 and adjusting the air flow control valve 32; 34 is installed at the outlet of the compressor 3b of the turbo compressor 3.
A pressure controller 35 is a pressure controller for giving control signals to an auxiliary furnace fuel flow controller 30 and an auxiliary furnace firing air flow controller 33 in accordance with the compressor discharge pressure detected by the pressure detector 5; This is an arithmetic unit for adjusting the operation signal given to the turbo compressor 4 depending on whether the turbo compressor 3 is in steady operation or in overdrive. Further, 36 is a bypass pipe branched from the system exhaust gas pipe 13, 37 is a turbine bypass valve interposed in the middle of this bypass pipe 36,
38 is a pressure transmitter that detects the exhaust gas pressure in the system exhaust gas pipe 13, that is, system back pressure; 39 is a pressure transmitter that controls the opening and closing of the turbine bypass valve 37 based on the system back pressure detected by the pressure transmitter 38; A pressure controller 40 converts the operation signal given from the pressure controller 39 to the turbine bypass valve 37 to the turbo pressure lit machine 3.
This is a computing unit for making adjustments depending on whether the engine is in steady operation or over-operation. Further, 41 indicates the turbine 3 according to the load command.
This is a nozzle controller for controlling the nozzle opening degree of a.

Next, we will discuss the operation of this system.

During steady operation of the system, that is, during steady operation of the turbo compressor 3, the atmospheric release valve 4 and the turbine bypass valve 37 are held fully open or at a constant minute opening by the action of the computing units 35 and 40, and the pressure controller 6 .39
doesn't actually work. The reason why the atmosphere release valve 4 and the turbine bypass valve 37 are fully opened or kept at a small constant opening is to minimize energy loss during steady operation. At this time, since the system is in steady operation, all process quantities within the system should originally be maintained at constant values, but changes in the compressor suction conditions due to changes in outside temperature and humidity during operation, and system emissions In reality, process quantities such as temperature and pressure gradually change due to changes in the amount of heat. As described above, it is important to always keep the compressor discharge pressure constant even with such changes. At this time, the pressure controller 34 controls the compressor discharge pressure.
The flow rate controller 3 controls the combustion amount of the auxiliary combustion furnace 27 so that the pressure detected from the pressure detector 5 becomes a constant target value.
0.33, i.e.
During steady system operation, by adjusting the combustion amount of the auxiliary furnace,
Feedback control is performed to keep the compressor discharge pressure within a certain range.

Next, the operation during load fluctuations will be described. First, immediately before a load command is issued, the control circuits in the computing units 35 and 4o are operated to place the atmospheric release valve 4 under the control of the pressure controller 6, and the turbine bypass valve 37 is controlled by the pressure controller 39.
be under the control of Next, set values for the auxiliary furnace fuel flow rate and the combustion air flow rate are directly given to the flow rate controller 30.33 as load commands to increase the turbine power. As a result, the discharge pressure of the compressor 3b tends to rise, but the discharge pressure of the compressor 3b is increased by adjusting the atmosphere release valve 4 by one movement of the pressure controller 6, that is, adjusting the amount of air released via the atmosphere release pipe 14. Constant control is performed. In this way, at the time of load command, the turbine power is increased by the feedforward operation of the combustion amount of the auxiliary combustion furnace, and a part of the increase in the discharge air flow rate of the compressor 3b due to this is kept at the compressor outlet side in order to keep the compressor discharge pressure constant. In this state, the turbo copressor 3 is powered up to satisfy the system required air amount. When the amount of air released from the atmosphere release valve 4 (opening degree of the atmosphere release valve) reaches a certain level, the system air flow control valve 7 is opened according to the system demand, and air from the turbo compressor enters the system. supplied to At this time, the opening degree of the nozzle 3C of the turbine 3a is changed by feedforward control based on a preprogrammed load command to cope with the change in the exhaust gas flow rate.

That is, when the opening degree of the system air flow control valve 7 is changed, the flow rate of the system exhaust gas increases or decreases, so the opening degree of the nozzle 3c is programmed to be controlled in a direction that absorbs this change in flow rate. In this system, the opening of the nozzle 3C is controlled relatively roughly, and the delicate constant control of system back pressure is achieved by adjusting the opening of the turbine bypass valve 37 through the action of the pressure controller 39. By giving the set value of the system air flow rate directly to the flow controller 9 as a load command to adjust the opening y4 of the flow rate control valve 7,
The set value of the nozzle opening degree is given to the nozzle controller 41 to adjust the nozzle opening degree. At this time, the system back pressure may try to fluctuate. Bypass valve 37
In other words, it is maintained at a constant value by adjusting the amount of exhaust gas released via the turbine bypass piping 36.

When the state change in response to the load command is completed and the system is stabilized, control of the compressor discharge pressure is transferred to the pressure controller 34, and the opening degrees of the atmosphere release valve 4 and the turbine bypass valve 37 are controlled by the computing units 35 and 40. The current opening degree is gradually narrowed down until it is finally fully closed, or the opening degree is maintained at a very small opening degree. As mentioned earlier, this operation is for the purpose of minimizing energy loss in the system, and the air release valve 4 and turbine bypass valve 37 are throttled down by fine adjustment so as not to disturb the control balance of the turbo compressor 3. The compressor discharge pressure is constantly controlled by adjusting the combustion amount of the auxiliary combustion furnace through the flow rate controllers 30 and 33. After the atmospheric release valve 4 and the turbine bypass valve 37 are closed, the state returns to the state under steady load.

FIG. 3 shows the change in the process amount of the turbo compressor when the load fluctuates according to this embodiment. When a load command is given at time t1, the auxiliary furnace fuel flow rate F1 changes in feedforward according to the load command. When the control operation increases, the combustion exhaust gas from the auxiliary combustion furnace 27 is added to the system exhaust gas, the turbine power increases, and the rotation speed of the turbo compressor 3 increases. At this time, since the system air flow rate F4 is still maintained at the value before the load command, the compressor discharge pressure P1 is about to rise. In response to this, constant pressure control by the pressure controller 6 works to release the excess air amount to the atmosphere as compressor discharge atmosphere open air S Fit F 1 , thereby increasing the compressor discharge pressure P.
1 is kept constant. Further, since the nozzle opening degree S is still maintained at the value before the load command, the system exhaust gas pressure pi also tends to increase. On the other hand, the system back pressure constant control by the pressure controller 39 is activated and the excess exhaust gas is discharged to the atmosphere as the turbine bypass air volume Fs, thereby maintaining the system back pressure P1 constant.

When the feedforward operation for the auxiliary combustion furnace 27 becomes stable, the flow rate control valve 7 is opened to increase the system air flow rate F.
4 to the load command to the target value, and the nozzle opening of the turbine 3a of the turbo compressor 3 is increased by feedforward operation. During this process, the compressor outlet atmospheric release valve 4 is The opening degree is adjusted and Fl changes, and the opening degree of the turbine bypass valve 37 is adjusted by a constant control operation of Pl, F5.
changes. The time when F4 reaches the target value (time 1z) is the first settling point for load fluctuations, and at this point the control of the compressor discharge pressure P1 changes from the control by adjusting the air discharge amount from the compressor outlet atmospheric release valve 4 to the auxiliary combustion furnace. The control is switched to the combustion amount adjustment of No. 27. Thereafter, the atmospheric release valve 4 and the turbine bypass valve 37 are gradually opened according to commands from the computing unit 35.40, and the time point (time 11) when the atmospheric release valve 4 and the turbine bypass valve 37 are completely throttled is reached. This is the second (final) settling point. 11 to t
In the process leading to Pl, control is performed to narrow down the auxiliary furnace fuel flow rate F1 through a constant control operation of Pl.

In the above embodiment, feedback control of the combustion amount of the auxiliary furnace is performed so that the discharge pressure of the compressor 9 remains constant during steady system operation, but at this time, the system back pressure does not change with changes in the process amount. Similarly, it is also conceivable to constantly control the system back pressure by the controller 39. At this time, the turbine bypass valve 37 is used to maintain constant system back pressure during steady operation.
1. It is necessary to maintain the minimum opening degree.

In this case, instead of the controller 39's feedback judgment that the system back pressure is constant, the calculator 40 is provided with a limiter function, and if the pressure exceeds a certain level, the calculation 840 is applied to the turbine bypass valve 37. It is also conceivable to issue an opening operation command to determine that the system back pressure falls within a certain range during steady operation.

Furthermore, in the above embodiment, the feedforward operation of the nozzle opening was started at the time when the system air flow IF4 started increasing (time t).
The same operation may be started in step 1). At this time, nozzle control is performed to suppress a temporary increase in system back pressure due to increased combustion in the auxiliary furnace.

[Effects of the Invention] Since the present invention has the above configuration, the following effects can be obtained.

(a) First, since the auxiliary combustion furnace is provided in the middle of the exhaust gas piping, the turbine does not run out of power in any load operating range.

(b) Then, keep the compressor discharge pressure and system back pressure within a constant range <? This makes it possible to keep the differential pressure between the reactant gas pressure in the fuel cell manifold and the nitrogen gas pressure in the casing constant at all times. It does not cause deterioration etc.

(C) Furthermore, since the system back pressure can be maintained constant even during load fluctuations, there is an advantage that combustion in the reformer is stabilized.

(d) Furthermore, when the load is constant, the atmosphere release valve and the turbine bypass valve can be kept fully open or slightly open, making it possible to minimize wasted energy. , enabling highly efficient operation.

(e) Furthermore, in this method, the turbine is of a variable nozzle type, and in addition to controlling the combustion of the auxiliary combustion furnace when the load fluctuates, the nozzle opening degree is also changed by feedforward control to actively adapt the turbine power to load fluctuations. I am trying to change it accordingly. Therefore, excellent responsiveness can be expected.
It becomes possible to quickly change the load on the fuel cell, in other words, the system flow rate.

A concrete explanation of this based on the above embodiment will be as follows. First, assuming that the inlet pressure P1 is constant, the turbine power is proportional to (inlet absolute temperature T) y and the nozzle area S. Therefore, when trying to cope with load fluctuations by changing only the turbine inlet temperature without changing the nozzle area, as shown by the imaginary line in Fig. 3, by increasing the combustion amount of the auxiliary combustion furnace 27 considerably. Unless the discharge air volume F1 of the atmosphere release valve 4 is made sufficiently large and the system air flow rate F4 is then changed to the target value, it is not possible to change the load while leaving a margin A for the discharge air volume. According to the present invention, when the system air flow rate F4 is changed to the target value, the nozzle area S can be changed almost simultaneously by feedforward control to measure the power amplifier of the turbine 3a, so that the power amplifier of the turbine 3a can be measured. Even if you start changing the system air flow rate F4 from a state where the discharge air lx F x of valve 4 is relatively small, the first settling time L
1, it is possible to reasonably secure the margin A of the discharge flow rate. Therefore, compared to a system without a variable nozzle function, it is possible to reduce the amount of combustion in the auxiliary combustion furnace during load fluctuations, which not only saves fuel, but also the time required to raise the temperature of the system exhaust gas (1+ ~t) and the time required to change the system air flow rate (1-
17) can both be shortened.

(f) Furthermore, when changing the system air flow rate and adjusting the turbine nozzle opening degree, the discharge air volume of the turbine bypass valve is adjusted by feedback control to keep the system back pressure constant. , there is no restriction that the nozzle opening must be precisely varied in a well-balanced manner so as not to fluctuate the system back pressure.

This makes it possible, in particular, to set the time required to change the system air flow rate (t '' tz ) very short.

Therefore, in combination with the circumstances described in the above section e, it is possible to provide a control method for a fuel cell power generation system that can perform extremely quick and accurate load control.

[Brief explanation of drawings]

FIG. 1 is a system explanatory diagram showing a conventional example, FIG. 2 is a system explanatory diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing process behavior in the same embodiment. 1...Fuel cell 1a...Air electrode lb...-Fuel electrode 2...Reformer 3...Turbo compressor 3aIII-Turbine 3b+11 Fun plate 2S 3c・1 Nozzle 4...Atmospheric release valve 10...φ Compressor discharge piping 14...Atmospheric release piping 36 Fist・φ/Haypass piping

Claims (2)

[Claims] (1) A fuel cell, a reformer for reforming hydrocarbon fuel and supplying hydrogen gas to the fuel cell, and an exhaust gas from the reformer or a surplus at the air electrode outlet of the fuel cell. A turbo compressor that operates a compressor using a variable nozzle turbine driven by both air and reformer exhaust gas and supplies compressed air necessary for the fuel cell and the reformer from the compressor; An auxiliary combustion furnace is placed on the exhaust gas piping leading to the turbine of the compressor to make up for the insufficient power of the turbine, and an auxiliary combustion furnace is provided on a bypass piping branched from the exhaust gas piping leading from the auxiliary furnace to the turbine, and the gas is discharged into the atmosphere through the piping. A turbine bypass valve that adjusts the amount of exhaust gas, and an atmosphere release valve that is provided on an atmosphere release pipe branched from a compressor discharge pipe of the turbo compressor and that adjusts the amount of air discharged to the atmosphere through the pipe. In this fuel cell power generation system, during steady operation of the system, the combustion amount of the auxiliary combustion furnace is controlled with the turbine bypass valve and the atmosphere release valve fully closed or slightly opened so that the compressor discharge pressure falls within a certain range. In addition, when the system load fluctuates, the combustion control of the auxiliary furnace and the turbine nozzle opening control are performed by feedforward control based on a program, and the feedback control of the system back pressure by the turbine bypass valve and the control of the atmospheric pressure are performed. A control method for a fuel cell power generation system characterized by feedback control of a constant compressor discharge pressure using an open valve. (2) A fuel cell, a reformer for reforming hydrocarbon fuel and supplying hydrogen gas to the fuel cell, and an exhaust gas from the reformer or a surplus at the air electrode outlet of the fuel cell. A turbo compressor that operates a compressor using a variable nozzle turbine driven by both air and reformer exhaust gas and supplies compressed air necessary for the fuel cell and the reformer from the compressor; An auxiliary combustion furnace is placed on the exhaust gas piping leading to the turbine of the compressor to make up for the insufficient power of the turbine, and an auxiliary combustion furnace is provided on a bypass piping branched from the exhaust gas piping leading from the auxiliary furnace to the turbine, and the gas is discharged into the atmosphere through the piping. A turbine bypass valve that adjusts the amount of exhaust gas, and an atmosphere release valve that is provided on an atmosphere release pipe branched from a compressor discharge pipe of the turbo compressor and that adjusts the amount of air discharged to the atmosphere through the pipe. In this fuel cell power generation system, during steady operation of the system, the combustion amount of the auxiliary furnace is fed back so that the compressor discharge pressure is kept within a certain range with the turbine bypass valve and the atmosphere release valve fully closed or slightly opened. In addition to control, the turbine bypass valve is controlled to keep the system back pressure within a certain range, and when the system load fluctuates, the combustion control of the auxiliary combustion furnace and the turbine nozzle opening control are based on the program. 1. A control method for a fuel cell power generation system, characterized in that feed forward control is performed, feedback control is performed using the turbine bypass valve to maintain a constant system back pressure, and feedback control is performed using the atmosphere release valve to maintain a constant compressor discharge pressure.