JPS61202215A - Output power controller for solar battery - Google Patents

Abstract

PURPOSE:To perform the fast follow-up control so as to set the output power of a solar battery at the maximum level by resetting properly a prescribed range of the output voltage used as a control standard in response to the relevant working environment. CONSTITUTION:A solar battery 1 supplies the DC power to a variable frequency inverter 5 via a reverse current stopping diode 2, etc. for conversion into the AC voltage of a variable frequency to control the speed of an AC motor 6. Both the output voltage VS and IS of the battery 1 are detected by detecting circuits 8 and 9 respectively and applied to s maximum power control circuit 10. Thus the inverter 5 delivers the maximum power via an inverter control circuit 11. Here both optimum Vmax and Vmin deciding blocks are added to the function block of a microcomputer of the circuit 10. Then the gate signal of the inverter 5 is cut off for detection of the no-load voltage of the battery 1. Thus the optimum Vmax and Vmin are decided. In such a way, the output power of the battery 1 is always kept at the maximum level despite the variation of the quantity of irradiated light, etc.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an output power control device for a solar cell, and particularly to a device for controlling the output power of a solar cell,
The present invention relates to an output power control device for a solar cell that controls the output of maximum power according to fluctuations in natural conditions such as temperature.

[Technical background of the invention]

In recent years, systems that use solar cells to convert solar energy into electricity have come into practical use. In order to efficiently convert solar energy into electricity and extract it, it is necessary to control the maximum output power of the solar cells. pump, blower.

A conventional circuit for driving a variable frequency inverter for an AC motor with a solar cell is shown in FIG. 5. The solar cell 1 supplies DC power to a variable frequency inverter 5 via a backflow blocking diode 2 and a smoothing reactor 3, and the inverter 5 applies a variable frequency AC voltage to an AC motor 6 to control its speed. do. The inverter 5 is a semiconductor switching element GU such as a giant transistor.

It consists of a GZ1 diode DU-Dl, etc., and consumes power in a pulsed manner, so a capacitor 4 is provided at its input terminal.This capacitor 4 and smoothing reactor 3 suppress the output current ripple of the solar cell and reduce the surge voltage. is suppressed. The output voltage (2) and output current (2) 8 of the solar cell 1 are detected by a voltage detection circuit 8 and a current detection circuit 9, respectively, and are applied to a maximum power l1111 circuit 10. Maximum power control circuit 10 provides a control signal to inverter control circuit 11 to control inverter 5 to output maximum power.

In general, the output of solar cells changes greatly depending on the amount of light irradiated! II. FIG. 6 shows typical output characteristics of commonly known solar cells. That is, the luminous intensity E, 1. E
2. The characteristics of output voltage V (solid line) and output power P8 (dashed line) with respect to output current I are shown using E, (E>E2>->Eo,) as parameters. In addition, the dashed-dotted line is the point P ・ where the output power P is maximum, plotted for each illuminance, and 1llax is the highest voltage at the point PIIlax within the planned illuminance range, and Vlo is the lowest voltage. be. When a variable frequency inverter is operated using a solar cell having the above output characteristics as a power source, frequency control is performed so that the output power of the solar cell is maximized (P□8). If the load on the AC motor 6 driven by the variable frequency inverter 5 is a pump, such as a load where the load torque increases according to the rotation speed, increasing the frequency will increase the speed and output of the AC motor 6. ,
The output current I8 of the solar cell 1 also increases. Generally, the inverter 5 is controlled so as to maintain the voltage/frequency ratio V/F constant (magnetic flux - constant). If it is proportional to the first power of degrees □ or more, the output power of the solar cell 1 also increases as the frequency of the inverter 5 increases. However, when the output current at the maximum output power P of the solar cell 1 is increased, the frequency ax is increased beyond 8, as shown in FIG.
The output "power" PS drops rapidly.

Considering the output characteristics of solar cells, in order to utilize solar energy that fluctuates greatly due to natural phenomena such as sunlight conditions as efficiently as possible, we developed the "Maximum Power III m Circuit" 10.
Follow-up control of the maximum single power output point ``Pg + ax'' of the solar cell is carried out using the . .

Thick! The output voltage (■) of the battery 1, and the output/current (■8) are respectively supplied to the multiplier 14 via the buffer 7 amplifier 12.13'.
The output power Ps of the solar cell is calculated here. This output power signal P8 is converted into a digital value by A/D conversion-1'b, and is converted into a digital value by the microcomputer 17.
In addition, the output voltage (2) of the solar cell, which is applied to the human-powered boat P1, is also converted into a digital value by the A/D converter 16, and is applied to the input boat P1 of the microcomputer 17.

The output port P2 of the microcomputer 17 is connected to each chip select terminal C8 of the A/D converters 15 and 16.
．． 1. ” From 2.2, the control signal is given □1, A
Either one of /D converters 15 and 16 is selected.

selected and input to the microcomputer 17, -P,
is given a digital signal. Microcomputer 1
7 performs the control and determination described below.1. The frequency reference signal FH in digital form is output from the output terminal DB, and the analog frequency reference signal FH is applied to the inverter control circuit 1.1 via the D/A converter 18. The inverter control/control circuit 11 inputs the frequency@reference signal ゛FH, and receives the V/F111111. P, WMi'JIIIJ, D, J: A variable frequency control signal) is output to control the inverter 5 and drive the AC/current motor 6. ,
- FIG. 8 is a functional block diagram of the microcomputer 17 in FIG. 7. See Figure 8 below.

Meanwhile, a conventional output power control method will be explained.

First, when starting the electric motor, use a predetermined frequency f,
When startup is complete, solar cell output voltage V8 and output power P8
is read in block 21, and ■3 is read in voltage judgment block 23.
Determine the voltage range of

In block 25, VS>vmax or vs<■
If so, select Δf2 as the frequency change width, and if ■≧■8≧vmin, select the frequency change width ma.
Select Δf1 as ×. However, here, 8f1<Δ[2. The selected Δf1 or Δf2 are applied to addition/subtraction blocks 26, 27, respectively.

S when the voltage is in the range v > v or VS < vlo
111ax If Δf2 addition/subtraction block 27″C frequency f is Δ
Rough control is performed by increasing or decreasing f2, and on the other hand, if voltage ■3 is in the range of VII18x≧v3≧■min, Δf
In the 1 addition/subtraction block 26, the frequency f is increased or decreased by Δf1 to perform precise control. This increased/decreased signal is passed through the addition/subtraction frequency output block 28 to the inverter frequency reference FH.
is output as On the other hand, the output power Ps read in the block 21 is judged to be increased or decreased by the power increase/decrease determination block 22, and the output frequency f is increased or decreased by Δf1 via the Δf1 selection block 24 and the f1 addition/subtraction block, and then outputted from the addition/subtraction frequency output block 28. Output as F8. In block 28, vs>vIl18x or VS<vmi
If n, the output of the block 27 is given priority over the output of the block 26 and the inverter frequency is set to 1i quasi-FH.

Next, the operation of this microcomputer 17 will be explained using the flowcharts shown in FIGS. 9 and 10. First, the electric motor is started at a predetermined frequency f (step 31). Next, the solar cell output voltage v8 and the output power P8 are read (step S2), and the solar cell output voltage v3 is determined (step 83), ■3 is the setting range ■1.18X≧VS≧■wi
If it is n, increase the frequency f by Δf1 (step 34) and check the voltage v3 again in step S6゜S.
7), V3 is within the setting range ■ll1ax≧■8≧■ll1i
o, check the output power P8 (step S8)
, when the output power increases, the frequency is increased by 8f1 again (step 83.34>).

Conversely, when the output power does not increase, the frequency "is decreased by Δf1 (step S9), and the same procedure (step S1
1 to 814). On the other hand, if the voltage V3 is outside the setting range, that is, if V, > VIIlax or ■3 < ■ll1io (steps 85, 810° 814), as shown in the subroutine of FIG.゛Increase by 2 I! - (Steps 815, 81
6), When V8 is low vmin, reduce Δf2 (
Step S15°817). As described above, if the output voltage of the thick i-cell is outside the set range, control is performed to drastically change the inverter frequency and bring the solar cell rapidly close to the maximum output power point.

[Problems with background technology]

However, the conventional maximum power control method described above has the following problems. The output characteristics of solar cells are generally significantly affected not only by the amount of irradiation but also by the ambient temperature.
The figure is a graph showing the influence of the irradiation light amount and temperature on the output of a typical solar cell.

Here, the solid line indicates illuminance E1. The broken line shows the output characteristics at temperature T1 when E, ..., Eo are parameters, and the broken line shows the output characteristics at temperature T2 (T2>T1) when illuminance E, E, ..., Eo is used as parameters. shows. As the temperature rises, the voltage decreases even if the illuminance remains the same, and the short-circuit current increases. The dashed line is the point PlI18 when the output power P is maximum.
x is plotted for each illuminance, and P(T)
is the temperature T1, and max I P (T2) is the plot at the temperature T2 l1a
x Point PIIl within the illuminance range planned in this way
The highest and lowest voltages taken by ax are at temperatures T and T2, respectively.
As shown in graph I11@, V (T
), V, (T1), V (T2) Illa
x 1 man
max, V・(T2). Therefore, if the operating temperature range of the solar cell is T-T2, the value of VIllax must be set to V (T1), and the value of V□in must be set to ax Vl, (T2). In other words, the voltage range at temperature T1 is 1llax (T1)
~■1o (T1) or frost moon range at temperature T2■
(T2) to V1o (i2), the voltage range is much wider than 1lax. If the temperature setting range is further expanded, the voltage setting range must also be further expanded.

However, if the voltage setting range is wide, the conventional control method cannot perform sufficient control.

This is because, as mentioned above, in the conventional method, the voltage is kept within a set range, and at certain times precise control is performed using a small Δf1 as the frequency change width, so even if the voltage is within a set range, even at a point quite far from the actual maximum power point. This is because if it is within the set range, close control will be performed and responsiveness will be extremely poor. In this way, the responsiveness is poor, and the maximum 1*′i″11 tr +, fj 3
a ′t”j 6 ′″& S T 8 'l <'
K 6 t ゛ Efficient use of solar cells will no longer be possible.

[Purpose of the invention]

Therefore, an object of the present invention is to provide an output power control device for a solar cell that can quickly follow the output power of the solar cell so that it always reaches the maximum even if the temperature changes due to the irradiation light IF3. .

[Summary of the invention]

A feature of the present invention is an output power control device for a solar cell that controls the power of a solar cell and supplies it to a load so that the output power is maximized, the device converting the power of the solar cell to the load. a voltage determining means for determining whether or not the output voltage of the Moekai solar cell is within a predetermined range;
output power increase/decrease determination means for determining an increase or decrease in output power of the solar cell; and a first power conversion means for adjusting the power conversion means so that the output power is maximized when the output voltage is outside the predetermined range. an adjusting means; when the output voltage is within the predetermined range and the output power is increased or decreased;
the power conversion means so that the output power is maximized;
a second adjustment means that adjusts with a finer adjustment range than the first 11111 means; detecting the no-load voltage of the solar cell multiple times at regular intervals; Further, voltage range determining means is provided for determining the predetermined range based on the maximum value of the detected value, and the voltage range determining means is provided so that the voltage range is always determined even when the irradiation light and the temperature change.
4 quickly so that the output power of solar cell 1 is maximum.
It is at the point where you can do the tracking.

・[Embodiments of the invention], 1: The 51st embodiment of the present invention in which a variable frequency inverter for an AC, YL motor is driven by a solar cell 1 is shown in the 11th m... ,show. This circuit is shown in Figure 56.
did. In the conventional circuit, the maximum N flow control circuit 10
A gate cutoff signal G is sent from the inverter to the control circuit 11. , give , , , , and other elements, the 51st, 2, , :2:=2τ:yu=:″
mm"t=L=:2::...:2, In the conventional example shown in FIG. It is also possible to output the cutoff signal G., so there is.3rd
The diagram is shown in Figure 2.
This is a functional block diagram of. This is an addition of the optimal V□x, ``+in determination block 29 to the conventional and conventional example shown in FIG. 8. As shown in FIG. 11, even at the same illuminance, the output characteristic of the solar cell is t! 11F. However, if the temperature is constant, the no-load voltage (18" =
The voltage (V8) at 0 does not change much with respect to Terumaro. Therefore, by making use of this property and detecting the no-load voltage of the solar cell, it is possible to easily estimate the almost optimal values of V and V at that temperature. X,, lln Now you can do the conventional f! Like control■+nax
There is no need to make a large voltage difference between and v1n. In block 29 of FIG.
.

Appropriate ■wax and ■sin are determined.

゛°°“Oy 929.”“it 6 t2 +”[/
)-%゛2゜The flow of Fig. 4 will be explained with reference to Fig. □. First, using the timer counter built into the microphone and computer 17, interrupts are made at regular intervals (step 818). , interrupts and micro.

Inverter tag gate cutoff signal G from boat P2.3 of computer 17. , is output (step 519)
. The inverter control circuit 11 receives an inverter gate cutoff signal G. , the gate of the inverter 5 is cut off, and the output of the solar cell is placed in a no-load state.

Subsequently, in this state, the no-load voltage of the solar cell is read multiple times, and the maximum value is set as V3. For example, if we consider the case of reading N times, first set the reading counter I to 01.
The initial value of v8 is set to O (step S20>. Next, the no-load voltage V, (1) of the solar cell at that time is read (step 521), and this is compared with V8 (step 522).Here If V8 (I)>■8, the value of V8 is replaced with the value of VS (I) (step 523).

Next, step 52 executes a routine for a predetermined period of time.
4) Increment the read counter ■ by 1 (step 525). In this way, from step S21 to step S25
The routine up to this point is repeated until 1=N (step 826). The value of Vs finally obtained in this way is the maximum value among the values read N times. From this maximum value, refer to the output characteristics graph of the solar cell and find the almost optimal ■
Then, from this VIllax, experience a+a
The value of min is determined by subtracting the predetermined width V, which is calculated according to the equation (step 527). This value is stored in the register of the microcomputer 17 (step 828), and the original control is returned from the timer counter interrupt routine, and the main tIllm is performed until the timer counter interrupt occurs again.

Conventionally, the voltage judgment block 23 judges the voltage of the solar cell based on the value of max' which is stored in advance in the register, but in the present invention, the value of v and ll1io is always new. ma
× is stored in a register, and v in that register, ■
The voltage ax of the solar cell is determined based on the latest value of ll1io. This eliminates the need to unnecessarily widen the voltage setting range, and also provides a voltage setting range that is optimal for the operating temperature.

The reason why the maximum value among the values read a plurality of times is taken as the no-load voltage (8) of the thick battery is to cope with the fact that the no-load voltage fluctuates over a short period of time. That is, the no-load voltage of the solar cell largely depends on the temperature as shown in FIG. 11, but it also depends to some extent on the illuminance. In general, temperature changes are relatively slow, so the detected no-load voltage is unlikely to have errors due to short-term temperature fluctuations, but illuminance may change over a short period of time, and fluctuations in illuminance may occur by chance. When detection is performed at the point in time, V, V, are set to appropriate values and max
+n+n, and optimal output power control cannot be achieved.

[Effects of the Invention] As described above, according to the present invention, the output power control device for the solar cell is configured to reset the predetermined range of the output voltage used as the control reference in a timely manner according to the operating environment. Always thick even if the light intensity and temperature change;
Rapid follow-up control becomes possible to control the maximum output power of battery A.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the control device according to the present invention, FIG. 2 is a circuit diagram of the maximum power control circuit in FIG. 1, and FIG.
Figure 2 shows the functional block diagram of the microcomputer, and Figure 4 shows the optimal
A flowchart showing the processing procedure ax of the decision block, FIG. 5 is a circuit diagram of an example of a conventional control iD wave device, FIG. A circuit diagram of the maximum power control circuit, Fig. 8 is a functional block diagram of the microcomputer in Fig. 7, Figs. 9 and 10 are flow charts explaining the operation of the microcomputer in Fig. 7, and Fig. 11 is a general diagram. 2 is a graph showing the output characteristics of a solar cell. 1... Solar cell, 2... Backflow blocking diode, 3
...Smooth reactor, 4...Condenser length, 5...
Variable frequency inverter, 6... AC motor, 7...
load, 8... voltage detection circuit, 9... current detection circuit,
10... Maximum power 1tII+ control circuit, 11... Inverter control circuit, 12.13... Buffer amplifier, 1
4... Multiplier, 15.16... A/D converter, 17
...Microcomputer, 18...D/A converter. Figure 1 Figure S FM ・ Figure 4 Figure 5 FM ・ Figure 9 Figure 11 X! Battery output voltage>t(Is)

Claims (1)

[Claims] 1. An output power control device for a solar cell that controls the power of a solar cell and supplies it to a load so that the output power is maximized, which converts the power of the solar cell to a power conversion means for applying to a load; a voltage determination means for determining whether the output voltage of the solar cell is within a predetermined range; an output power increase/decrease determination means for determining an increase or decrease in the output power of the solar cell; a first adjusting means that adjusts the power conversion means so that the output power is maximized when the output voltage is outside the predetermined range; and when the output voltage is within the predetermined range and the output When the power increases or decreases, the power conversion means detects the no-load voltage of the solar cell a plurality of times at each first fixed time so that the output power becomes the maximum, and based on the maximum value of the detected values. An output power control device for a solar cell, further comprising voltage range determining means for determining the predetermined range.