JP3428869B2 - Fuel cell output fluctuation compensation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell output for suppressing fluctuations in fuel cell output current at the time of a sudden load change when power is supplied to a load by a fuel cell alone. it is to about <br/> the variation compensation how. 2. Description of the Related Art "Fuel cell power supply system" (Japanese Unexamined Patent Publication No.
123609) and "Instantaneous Load Compensator for Fuel Cell Power Generation System" (SPC-
FIG. 5 shows a configuration of a conventional fuel cell output fluctuation compensation system proposed as 93-85). In the figure, 1 is a fuel cell, 2 is a smoothing capacitor, 3 is an inverter, 4 is an AC load, 5 is a storage battery, 6 is a bidirectional converter, 7 and 8 are current detectors, 9 is a voltage detector, 102 is a limiter, 103 is a PWM circuit, 200
The control circuit, 201 lag filter, 202 is a V _'B regulation circuit. The operation of the conventional fuel cell output fluctuation compensation system will be described below with reference to the drawings. V _'B regulation circuit 202 output voltage V of the battery 5 at a point 9 on connection of Figure 5''as input deviation between _B ^*, V' output voltage command value V _B and the storage battery 5 _B modulating signal V ' Outputs _B1 . The current detector 8 detects the input current I of the inverter 3
Detect _O. The inverter input current _IO is input to the delay filter 201 to obtain the delay current _IO1 . Delay current I _O1 is compared subtracted an inverter input current I _O, the subtraction result is further compared subtracting the V _'B modulating signal V' _B1, the compensation current reference I _'CO is made. Compensation current reference I _'CO compensation current command value I through a limiter 102' PWM as _C ^* next, _C 'compensation current I detected by the _C ^* and the current detector 7' compensation current command value I matches The switch in the bidirectional converter 6 is turned on / off by the circuit 103. FIG. 6 shows current waveforms at various parts in the conventional fuel cell output fluctuation compensation system when the load suddenly changes. Figure 6 shows the case where the inverter input current I _O with the rapid increase of the AC load 4 at time t ₁ is abruptly increased from 0 to I _1. In the figure, I ₁ is the amount of change in the inverter input current I _O when the assumed maximum load change occurs.
Fuel cell output current I at time t ₁ 'as _FC increase rate of the maximum allowable rate of increase lag filter 201 and V' _B
The adjustment circuit 202 is adjusted. As shown in FIG. 6, the fuel cell output current I with the rapid increase in the inverter input current I _{O 'FC} increases gradually, the fuel cell output current I at time t _{2' FC} and the inverter input current I _O is coincident . Time t
Fuel cell output current I ₁ until time t ₂ 'current difference _FC and the inverter input current I _O is discharged from the battery 5 via a bidirectional converter 6, the time t ₂ after the fuel cell output current I' _FC The storage battery 5 is charged with a current equal to the difference between the current and the inverter input current _IO . [0007] Since at INVENTION Problems to be Solved conventional fuel cell output fluctuation compensation system is created using a filter delay compensation current I _'C of the command value I' _C ^*, as shown in FIG. 6 the rate of increase of the fuel cell output current _{I 'FC} decreases gradually at time _{t 2} from time _{t 1.} Therefore, the fuel cell 1 becomes to increase the _FC 'fuel cell output current I at a small rate of increase than the allowable maximum increase rate despite it is possible to increase the _FC' fuel cell output current I at the maximum allowed rate of increase , smaller charge than can be supplied charge from the fuel cell 1 in the fuel cell at time t ₂ from time t ₁ 1
Supplied from The difference between the charge that can be supplied from the fuel cell 1 and the charge that is actually supplied from the fuel cell 1 is supplied from the storage battery 5, and the storage battery capacity must be designed to be large by the difference. There was a problem that the price increased. The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel cell output variation compensation how that can reduce the power storage device capacity. [0008] In order to achieve the above object, the present invention converts DC power output from a fuel cell into AC power through an inverter and supplies the AC power to an AC load. The output current of the fuel cell is compensated by discharging or charging a storage battery connected to the fuel cell through the bidirectional converter, wherein the input current of the inverter is larger than the output current of the fuel cell. Sometimes, a reference for the current output from the bidirectional converter to the output line of the fuel cell is created so that the output current of the fuel cell constantly increases at the maximum increase rate allowed by the fuel cell , and Inn
The input current of the barter is equal to or less than the output current of the fuel cell;
The output voltage of the power storage device is the output voltage of the power storage device.
When the output voltage of the fuel cell is smaller than the voltage command value,
Flow increases steadily at the maximum rate allowed by the fuel cell
From the output line of the fuel cell to
Create a reference for the current input to the inverter, and
When the input current of the inverter is lower than the output current of the fuel cell,
And the output voltage of the power storage device is
When the output voltage is equal to or higher than the output voltage command value,
So that the current matches the input current of the inverter.
Output from the bidirectional converter to the output line of the fuel cell
Create a reference of the current, the inverter input current I _O is
When larger than the fuel cell output current I _FC is the fuel collector
The sum of the pond output current I _FC and the fuel cell allowable increment current ΔI
Compared to the fuel cell rated current _{I FC0, I FC + ΔI <} I
_{If FC0} , the compensation current reference I _{C0 is set} to I ₀ − (I _FC
+ ΔI), and if I _FC + ΔI ≧ I _FC0 , compensation
The current reference _{I C0} and _I 0 _{-I FC,} the inverter input
The force current I ₀ is smaller than the fuel cell output current I _FC
Does time equal, battery voltage V _B and the battery voltage command value
Comparing V _{B ^*,} if ^* _V ^B _<V B, the fuel cell output
Fuel conductive the sum of the current I _FC and the fuel cell allowable increment current ΔI
Compared with the _battery rated current I _FC0 , I _FC + ΔI <I _FC0
Then, the compensation current reference I _{C0 is set} to I ₀ − (I _FC + Δ
I), and if I _FC + ΔI ≧ I _FC0 , the compensation current
The reference _{I C0} and _I 0 _{-I FC,} and the battery voltage _{V B}
Comparing the battery voltage command value _V ^{B *,} with _{V ^B} ≧ _{V B} ^*
If the compensation current reference _{I C0} is 0, the compensation current group
Compensation current command value quasi _{I C0} via the limiter _I ^{C *} and
The compensation current command value I _C ^* and the bidirectional converter output
Bidirectional by the PWM circuit as compensation current _{I C} are identical
A switch in the converter is turned on and off . According to the present invention, by the above means, the maximum charge that can be supplied from the fuel cell can be extracted from the fuel cell. Further, after the power storage device is discharged, the power storage device can be rapidly charged in preparation for the next discharge. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration explanatory view showing an embodiment of the present invention. In the figure, 10 is a current detector, 100 is a control circuit, and 101 is a compensation current calculation circuit. In the figure, the same parts as those in FIG. 5 are denoted by the same reference numerals, and the description thereof will not be repeated. FIG. 2 is a flowchart showing the operation of the compensation current calculation circuit 101 of FIG. In the figure, ΔI is the maximum value of the current that can be increased from the fuel cell 1 during one control cycle of the control circuit 100. The operation of the fuel cell output fluctuation compensation system according to this embodiment will be described below with reference to FIGS. The compensation current calculation circuit 101 calculates the point 9 on the connection in FIG.
Detecting the output voltage V _B of the battery 5 in. The current detector 8 detects the input current I of the inverter 3
Detect _O. Current detector 10 detects the output current I _FC of the fuel cell 1. Battery output voltage V _B, the inverter input current I _O, and the fuel cell output current I _FC is input to the compensation current computing circuit 101. [0017] In the compensation current computing circuit 101, as shown in FIG. 2, compare the inverter input current I _O and the fuel cell output current I _FC (S1). If I _O > I _FC in S1, the sum of the fuel cell output current I _FC and the allowable increase current ΔI of the fuel cell 1 is compared with the rated current I _FC0 of the fuel cell 1 (S2). If I _FC + ΔI <I _FC0 in S2, the compensation current reference I _{CO is set} to I _O − (I _FC + ΔI) (S3). If I _FC + ΔI ≧ I _FC0 in S2,
The compensation current reference I _{CO is set} to I _O −I _FC (S4). If I _O ≦ I _FC in S1, compares the battery voltage V _B and the battery voltage command value V _B ^* (S5). V _{B in} S5
If <V _B ^* , the fuel cell output current I _FC and the fuel cell 1
Of the fuel cell 1 with the allowable increase current ΔI
_Compare with _FC0 (S6). In S6, I _FC + ΔI <I
_{If FC0} , the compensation current reference I _{CO is set} to I _O − (I _FC + Δ
I) (S7). In step S6, I _FC + ΔI ≧ I _FC0
, The compensation current reference I _{CO is set} to I _O −I _FC (S
8). If V _B ≧ V _B ^* is in S5, the compensation current reference I _CO and 0 (S9). The compensation current reference I _CO compensation current command value I _C ^* next via the limiter 102, the compensation current command value I _C ^*
And the switch in the bidirectional converter 6 is turned on and off by the PWM circuit 103 so that the compensation current I _C detected by the current detector 7 matches the compensation current I _C. FIG. 3 is a characteristic diagram comparing the current waveform of each part in this embodiment at the time of a sudden change in load with the current waveform of each part in the conventional example. FIG. 3 shows a case where the input current I _O of the inverter 3 sharply increases from 0 to I ₁ at time t ₁ as the AC load 4 rapidly increases, similarly to FIG. In addition, the same portions as those in FIG. 6 are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 3, the fuel cell output current with the rapid increase in the inverter input current I _O I _FC increases constant at the maximum rate of increase of the fuel cell 1 is allowed, the fuel cell output current I _FC at time t ₃ And inverter input current I
_O matches. From time t ₁ to time t _3, a current having a difference between the fuel cell output current I _FC and the inverter input current I _O is discharged from the storage battery 5 via the bidirectional converter 6, and the time t
_{From 3} onwards, the fuel cell output current I _FC and inverter input current I
_The storage battery 5 is charged by the current of _O difference. The fuel cell output current I _FC also increases the time t ₃ or later, since the fuel cell output current I _FC reaches the fuel cell rated current I _FC0 at time t _4, the storage battery 5 at time t ₄ later I _FC0 -I ₁ Charge. Battery voltage V _B and the battery voltage command value V at time t ₅
Charging of the battery 5 has finished because _{the B} ^* match, the compensation current I _C becomes 0, the fuel cell output current I _FC and the inverter input current I _O is equal. As shown in FIG. 3, in this embodiment, the electric charge discharged from the storage battery 5 is smaller than the electric charge discharged in the conventional example only by the hatched portion, so that the storage battery capacity can be reduced accordingly. Can be. FIG. 4 is a diagram showing an "instantaneous load compensator for a fuel cell power generation system" (SPC, the Institute of Electrical Engineers of Japan).
FIG. 9 is a characteristic diagram comparing an experimental example in (-93-85) and the present embodiment. FIG. 4 shows that the inverter input current _IO is 6
A case where the current sharply increases from 3A to 126A, which is the rated current of the fuel cell, is shown. In addition, the same parts as those in FIG.
The same reference numerals are used, and duplicate description is omitted. In FIG. 4, the ratio of the area of the oblique line a to the sum of the area of the oblique line a and the area of the oblique line b was about 23%. That is, it is understood that the storage battery capacity can be reduced by about 23% according to the present embodiment. It goes without saying that an electrolytic capacitor or an electric double-layer capacitor can be used instead of the storage battery 5 used in this embodiment. [0022] As is evident from the foregoing description, according to the present invention, it is possible to provide a fuel cell output variation compensation how that can reduce the power storage device capacity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory view showing one embodiment of the present invention. FIG. 2 is a flowchart illustrating an example of an operation of a compensation current calculation circuit according to the present invention. FIG. 3 is a characteristic diagram comparing a current waveform of each section in the embodiment of the present invention at the time of a sudden change in load with a current waveform of each section in the conventional example. FIG. 4 is a characteristic diagram comparing an experimental example in a conventional fuel cell output fluctuation compensation system and an embodiment of the present invention. FIG. 5 is a configuration explanatory view showing a conventional fuel cell output fluctuation compensation system. FIG. 6 is a characteristic diagram showing a current waveform of each part at the time of a sudden load change in a conventional example. [Description of Signs] 1 Fuel cell 2 Smoothing capacitor 3 Inverter 4 AC load 5 Storage battery 6 Bidirectional converters 7, 8, 10 Current detector 9 Voltage detector 100, 200 Control circuit 101 Compensation current calculation circuit 102 Limiter 103 PWM circuit 201 lag filter 202 V _'B regulating circuit

(56) References JP-A-7-123609 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/04 H01M 8/06

Claims (1)

(57) [Claims 1] DC power output from a fuel cell is converted into AC power through an inverter to supply power to an AC load. In a fuel cell output fluctuation compensation method for compensating by discharging or charging a storage battery connected to a fuel cell through a bidirectional converter, when the input current of the inverter is larger than the output current of the fuel cell, the output current of the fuel cell is A reference for a current output from the bidirectional converter to an output line of the fuel cell is created so as to constantly increase at a maximum increase rate allowed by the fuel cell ;
The input current is less than or equal to the output current of the fuel cell and
The output voltage of the power storage device is an output voltage command of the power storage device.
When the output current of the fuel cell is smaller than the
Increase at a constant rate at the maximum rate that the fuel cell allows
From the output line of the fuel cell to the bidirectional converter
A reference for the current to be input to the
The input current of the fuel cell is less than or equal to the output current of the fuel cell.
And the output voltage of the power storage device is the output voltage of the power storage device.
When it is equal to or more than the command value, the output current of the fuel cell
Make sure that the bidirectional core
Output from the inverter to the output line of the fuel cell
Create a reference flow, the inverter input current I O is the fuel cell output current I FC
When is large, the fuel cell output current I FC and the fuel cell
The sum of the allowable increase current ΔI and the fuel cell rated current IFC0 is
If I FC + ΔI <I FC0 , the compensation current base
A quasi-I C0 I 0 - and (I FC + ΔI), I FC + ΔI
If ≧ I FC0 , the compensation current reference I C0 is set to I 0 −I
FC , and the inverter input current I 0 is
When less than or equal to the output current I FC is battery
Compares the voltage V B and the battery voltage command value V B *, V B <V
If B *, the fuel cell output current I FC and the fuel cell tolerance
Compare the sum with the increased current ΔI with the fuel cell rated current IFC0
If I FC + ΔI <I FC0 , the compensation current reference I
Let C0 be I 0 − (I FC + ΔI), and I FC + ΔI ≧ I
If FC0, and the compensation current reference I C0 I 0 -I FC
And, he said with the battery voltage V B battery voltage command value V B *
And if V B ≧ V B * , the compensation current reference I C0
Is set to 0, and the compensation current reference IC0 is set to a compensation current reference via a limiter.
A decree value I C *, the compensation current command value I C * bidirectionally co
PWM circuit as the converter output compensation current I C are identical
And a switch in the bidirectional converter for turning on and off the fuel cell output fluctuation compensation method.