JPH0642181B2 - Fuel cell power generation system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hybrid fuel cell power generation system used as an independent power source such as a mobile power source, and particularly to a control device therefor.

[Conventional technology]

Generally, in a fuel cell power generation system configured by combining a fuel cell and a fuel reformer, the fuel cell is used as a backup power source of the fuel cell in order to make the response speed of the reformer slow and to start / stop the power generation system. A storage battery is connected to the output side of the fuel cell, and at the time of start and stop, this storage battery is used as the control power supply of the power generation system to operate the control equipment required for start and stop operation, and during power generation, the power generation amount of the fuel cell against the sudden load increase. A hybrid fuel cell power generation system has been proposed in which the shortage of electric power until the vehicle follows the load is discharged from the storage battery, and the storage battery is recovered and charged by the surplus power of the fuel cell when the load is light.

By the way, if the storage battery is continuously charged from the fuel cell while the light load operation state continues for a long time, the storage battery becomes overcharged and the storage battery voltage rises. On the other hand, a constant voltage control device is usually used as a component of the fuel cell control device, and this constant voltage control device operates normally in a certain voltage range. The problem arises that the allowable range of the voltage device is exceeded and the control device does not operate normally.

[Problems to be Solved by the Invention]

As described above, in order to normally operate this type of fuel cell power generation system, it is necessary to always keep the voltage of the storage battery within a range in which the control device can normally operate. For this purpose, it is necessary to always maintain a proper charge amount of the storage battery and prevent overcharge.

An object of the present invention is to solve the above problems and keep the storage battery voltage within a predetermined range so that the fuel cell power generation system operates normally.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, according to the present invention, an auxiliary machine having a storage battery as a backup power source, a load circuit, and a constant voltage controller on the output side of a fuel cell via an output current detector and a DC / DC chopper In a hybrid fuel cell power generation system connected to a control circuit, a charging power calculation unit that receives a detection signal of the storage battery voltage and a set value signal thereof and issues a charging power signal of the storage battery proportional to the difference between the two signals, and A power generation amount calculation unit for adding the charging power signal, the auxiliary power detection signal, and the load power detection signal to generate the power generation signal of the fuel cell, and the power generation amount signal and the fuel cell voltage detection signal. DC received
/ DC chopper is provided with an operation control circuit including an output current operation unit that issues an output current command value signal, and D is calculated based on a difference between the output signal of the output current detector and the output current command value signal.
It is configured to control the C / DC chopper output current and the accessory control circuit.

[Action]

In the above means, the charging power required for recovering and charging the storage battery voltage to the set value by multiplying the difference in the detected value with respect to the set value of the storage battery voltage by the proportional coefficient corresponding to the power generation capacity of the fuel cell, for example, in the charging power calculation unit of the storage battery. Is calculated as a command signal, and the power generation amount calculation unit calculates the total power generation amount by adding the load power detection value and the auxiliary device power detection value to the charging power command value, and the output power calculation unit calculates the power generation amount calculation value as the fuel cell. The output power command value divided by the output voltage detection value of is calculated, and the command signal is adjusted in timing by the delay circuit according to the response speed of the reformer, and the DC / DC chopper control circuit and the auxiliary machine control circuit are controlled. In addition, when the storage battery supplies load power or auxiliary power and the terminal voltage drops when the fuel cell starts up or the load increases rapidly by configuring to control the amount of power generation and the chopper output current. Since the output current command value by spreading the difference between the detected voltage and the setting voltage is increased, the output current of the power generation amount and DC / DC chopper of the fuel cell increases based on this, this battery is recovered charged by,
The recovery charging of the storage battery ends when the detected value of the storage battery voltage reaches the set voltage. Therefore, the increase in the storage battery voltage is avoided, and the storage battery is overcharged due to the increase in the voltage.
Also, the unstable operation of the constant voltage control device provided in the auxiliary machine control circuit can be avoided, and the operation of the power generation system can be stabilized.

〔Example〕

 The present invention will be described below based on examples.

FIG. 1 is a system configuration diagram showing a simplified embodiment device of the present invention, FIG. 2 is a time chart showing the operation of the embodiment device when the load power rapidly increases, and FIG. 3 is a charging / discharging of a storage battery in the embodiment device. It is a voltage-current characteristic diagram which shows a characteristic. In FIG. 1, 1 is a raw fuel tank, 2 is a reformer for steam-reforming raw fuel to produce hydrogen-rich fuel gas, 3 is a fuel cell, and a raw material pump 7 reforms the raw material tank 1 For example, methanol as a raw fuel supplied to the reactor 2 is steam-reformed at a predetermined temperature by the off-gas sent from the fuel cell 3 to the burner of the reformer 2 and the combustion heat of the combustion air sent from the blower 8 to generate steam. The generated fuel gas electrochemically reacts with the reaction air sent from the blower 9 in the fuel cell 3 to generate electricity.

The output side of the fuel cell 3 is connected to the load circuit 5 via the DC / DC chopper 4 to supply the generated electric power to the load circuit 5, and the output side of the DC / DC chopper 4 has a storage battery 6 as a backup power source. Is provided to supply a shortage of the generated power of the fuel cell 3 when the device is started up or when the load power rapidly increases, and is recovered and charged by the surplus power when the load is light.

Reference numeral 10 denotes a control unit of the above-described power generator, which includes an accessory control circuit 14 connected to the output side of the DC / DC chopper via a constant voltage controller (AVR) 13, and the accessory control circuit 14 and the DC.
The control circuit 16 of the / DC chopper 4 and the operation control unit 20 which issues the current command signal I _fc .

The arithmetic and control unit 20 detects the detection signal V _b of the detector 11 for the storage battery voltage.
If, battery charging power P _{b =} K (V _bs -V obtained by multiplying a proportional coefficient K to the difference between the output signal V _bs of the voltage set value 15
a charging power calculating unit 21 for _b) calculating an output, the output signal P _o, and the auxiliary power supply to the auxiliary device 7, 8, and 9 of the charging power command signal P _b to the load power detector 17 of the storage battery Generation power calculation unit for calculating and outputting the output signal P _c of the detector 18 of
22 and an output current command value I obtained by dividing the obtained generated power P by the detection signal V _fc of the output voltage detector 19 of the fuel cell 3.
_The delay circuit 24 includes three calculation units, an output current calculation unit 23 that calculates and outputs _fc .

The output command signal I _fc of the arithmetic control unit 20 has its output timing controlled by the delay circuit 24 in accordance with the response speed of the reformer 2 and the fuel cell 3, and is supplied to the accessory control circuit 14 to be supplied by the pump 7. The control of the raw fuel and the air amount control by the blowers 8 and 9 are controlled corresponding to the output current command value I _fc, and the output current actual value _If of the detector 12 of the output current of the fuel cell 3 and its command value. by the control device 16 of the DC / DC chopper 4 is feedback controlled based on the difference I _fc -I _f the I _fc, the output current of the DC / DC chopper 4 is controlled so as to approach the command value I _fc.

In the fuel cell power generation system of the embodiment configured as described above, a time chart when the load power _Po is rapidly increased is shown in FIG. 2, and a change in the voltage-current characteristic of the storage battery at this time is shown in FIG. , The load power P _o is operated at a light load P _o1 , and therefore at time t ₁ , the storage battery 6 is recovered and charged by the charging current IBA by a part of the fuel cell output PA, and its terminal voltage VB is recovered and charged to VBA,
It is assumed that the load power P _o sharply increases to P _o2 in a state where the remaining capacity x ₁ % indicated by point A in FIG. 3 is reached. The increase in the load power _Po is due to the discharge current I of the storage battery 6 as a backup power source.
B is supplied by the rapid increase of IBB, and the storage battery voltage VB decreases from VBA corresponding to the point A in FIG. 3 to VBB corresponding to the point B and VBC corresponding to the point C, and the remaining capacity thereof is x. It decreases from ₁ % to x ₂ %.

At this time, proliferation of load power P _o is the load power detection signal input to the charging power calculation unit is detected by the load power detector 17 is updated from P _o1 to P _o2, decrease in battery voltage VB is the voltage detected Since the difference between the detection signal V _b detected by the device 11 and its setting signal V _bs increases, the charging power command signal P _b proportional to this difference increases. Therefore, the output signal P of the generated power calculating unit 21, and the output command signal I _fc of output power calculating unit 23 also increases, the command signal I _fc is DC / DC chopper 4 to determine the increase in the output current through the delay circuit 24 Is output to the control circuit 16 and the accessory control circuit 14.
As a result, the output power P of the fuel cell 3 changes from time t ₁ to t
_As it increases from PA to PD over ₃ , the discharge current IBB of this storage battery decreases from point C to point D in FIG. 3, changes from the discharge current to the charge current at time t ₂ , and changes to time t ₃ At point D, point D is reached, and the battery is recovered and charged toward point E. The storage battery voltage VB is also changed from VBC to VB with the recovery charge due to the decrease of the discharge current and the increase of the charge current.
When the voltage rises to D, VBE and becomes equal to the set voltage VBS at VBE, the charging power command signal P of the charging power calculation unit 21
_b becomes zero, and the storage battery voltage VB maintains the state in which VBS is held, and the load power P _o and the auxiliary device power P _c are all in the steady operation state supplied by the output power P of the fuel cell 3.

In this way, since the storage battery voltage VB is held at the substantially constant set voltage value VBS by the recovery charge, overcharge of the storage battery 6 is prevented and the stable operation of the constant voltage controller 13 is held. In addition, the rate of increase of the current command signal I _fc
Since it is controlled according to the response speed of the reformer and the fuel cell 3 by the 24, the DC / DC chopper 4 does not exert an adverse effect such as fuel shortage or voltage drop on the fuel cell 3 by requesting an excessive current. The generated power P can be controlled to increase within the range.

When the load power _Po increases sharply, the difference between the detected value of the storage battery voltage and the set value also increases sharply, and the calculation control unit 20 requests a sharp increase in the output power P of the fuel cell based on this, but the charging power By providing a limiter for saturating the output command signal P _b at a predetermined level in the calculation unit 21, it is possible to easily suppress the current command signal I _fc, and to prevent the adverse effect on the fuel cell 3 together with the delay circuit 24. Can be eliminated.

Even when the power generation operation in the light load state continues, the storage battery voltage VB is held at the set voltage VBS, so that the overcharge of the storage battery 6 can be prevented. Further, even when the storage battery voltage VB is lowered by the storage battery supplying the auxiliary power at the time of startup, the calculation control unit 20 obtains the generated power P corresponding to the sum of the charging power command signal P _b and the auxiliary power P _c , By outputting the output current command signal I _fc corresponding to this to the DC / DC chopper 4 and the auxiliary machine control circuit 14, the regenerative charging of the storage battery 6 is performed with the increase of the generated power P of the fuel cell 3, and thereafter. When the load circuit 5 is connected, control can be performed in the same manner as when the load power is rapidly increased.

〔The invention's effect〕

As described above, the present invention provides a charging power calculation unit that outputs a charging power command signal for a storage battery that is proportional to the difference between the detection signal of the storage battery voltage and its setting signal, and a load power detection signal and a supplementary signal for this charging power command signal. A generated power calculation unit that adds a machine power detection signal and outputs a generated power signal of the fuel cell; and an output current calculation unit that outputs an output current command signal obtained by dividing the generated power signal by the output voltage detection signal of the fuel cell, And a delay circuit for timing-controlling and outputting the output current command signal to form an arithmetic control unit, and supplying the current command signal to the accessory control unit and the control circuit of the DC / DC chopper to output the output power of the fuel cell and It is configured to control the output current of the DC / DC chopper. As a result, the load power and the auxiliary power that account for the output power of the fuel cell are based on the measured value, and the charging power of the remaining storage battery is a command value proportional to the difference voltage that the measured value of the storage battery voltage has with respect to the set value. Given,
In addition, since the power generation capacity of the fuel cell can be adjusted by adjusting the proportional constant K that is multiplied by the difference voltage, the recovery charge of the storage battery can be adjusted so as to reduce the load power and auxiliary power, and the fuel cell will not be overloaded. Since it can be performed in a range, and because the storage battery voltage can be suppressed to a range that does not exceed the set value, overcharge of the storage battery caused by the increase in the storage battery voltage and a deterioration of the storage battery based on this, which are problems in the conventional technology,
The instability of the operation of the constant voltage control device caused by the voltage rise is eliminated, and the recovery charge can be performed within the range where the fuel cell can operate normally even when the load power suddenly increases or at the time of startup, and the light load state It is possible to provide a fuel cell power generation system in which the storage battery voltage is stably maintained at the set value even if the above condition continues, and stable operation can be performed without causing overcharge of the storage battery.

[Brief description of drawings]

FIG. 1 is a system configuration diagram schematically showing an embodiment apparatus of the present invention, FIG. 2 is a time chart showing an operation when the load of the embodiment apparatus is suddenly increased, and FIG. 3 is a charging / discharging state of a storage battery in the embodiment apparatus. It is a voltage-current characteristic diagram which shows. 2: reformer, 3: fuel cell, 4: DC / DC chopper,
5: Load circuit, 6: Storage battery, 7,8,9: Auxiliary equipment, 10: Control device, 11,19: Voltage detector, 12: Current detector, 13: Constant voltage control device, 14: Auxiliary equipment control circuit , 15: voltage setting device, 16: chopper control circuit, 17: load power detector, 18: auxiliary device power detector, 20: calculation control unit, 21: charging power calculation unit, 22: generated power calculation unit, 23: Output current calculator, 24: delay circuit, V
B: battery voltage, _{V b:} battery voltage detection signal, V _bs: battery voltage setting signal, K: proportional coefficient, _{P b:} charging power command signal, _{P o} is the load power detection signal, _{P c:} auxiliary power detection signal , P: generated power signal, V _fc : fuel cell output voltage detection signal, I _fc : output current command signal, IB: charge / discharge current,
_If : output current detection signal of the fuel cell.

Claims (1)

[Claims] 1. A hybrid system in which an output side of a fuel cell is connected to a storage battery as a backup power source, a load circuit, and an auxiliary machine control circuit having a constant voltage control device through an output current detector and a DC / DC chopper. In the fuel cell power generation system, a charging power calculation unit that receives the detection signal of the storage battery voltage and its set value signal and issues a charging power signal of the storage battery proportional to the difference between the two signals, and the detection of the charging power signal and auxiliary power Signal and a detection signal of load power, and outputs a power generation amount signal of the fuel cell, and an output current command of the DC / DC chopper which receives the power generation amount signal and the detection signal of the fuel cell voltage An arithmetic control circuit including an output current arithmetic unit that issues a value signal,
A fuel cell power generation system configured to control a DC / DC chopper output current and an accessory control circuit based on a difference between an output signal of the output current detector and an output current command value signal.