JPS62154122A - Charging control system in solar generating device - Google Patents

Abstract

PURPOSE:To obtain a charging control system high in working efficiency by removing a DC/DC converter when the ratio between the input voltage and the output voltage of the DC/DC converter is kept between the conversion efficiency of the DC/DC converter and the reciprocal of said conversion efficiency. CONSTITUTION:When an accumulator 3 has a level less than a full charge mode, the DC voltage generated by a solar battery 1 is raised or dropped via a DC/DC converter 5 after a switch 12 is closed. Then a charging current and a load current are supplied to the accumulator 3 and the load 4 respectively in response to the output voltage of the converter 5. While the rise and drop are nor required for the output voltage of the battery 1 by the function of the converter 5 when the ratio between the output voltage V0 and the input voltage Vi of the converter 5 is kept between the conversion efficiency FC of the converter 5 and its reciprocal 1/FC. Thus an input/output voltage comparison control circuit 9 opens the switch 12 and separates the converter 5 from the load 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a charging control method for a storage battery in a solar power generation device using solar cells, and in particular, the present invention relates to a charging control method for a storage battery in a solar power generation device using a solar cell, and in particular, a method for controlling the charging of a storage battery by direct current from a solar cell via a DC/DC converter. The present invention relates to a charging control method in a solar power generation device configured to charge.

[Prior art]

FIG. 2 is a block diagram showing the system configuration of a solar power generation device equipped with a conventional DC/DC converter. The voltage of the direct current generated by the solar cell 1 is D C/D
The voltage is stepped up or stepped down by the C converter 5, and a charging current and a load X current according to the output voltage are supplied to the storage battery 3 and the load 4. When the terminal voltage of the storage battery 3 reaches the terminal voltage at full charge, the full charge detection control circuit 7 opens the switch 2 and disconnects the solar cell 1, thereby preventing overcharging of the storage battery 3.

FIG. 3 is a diagram showing the temperature characteristics of the output voltage -1 of the solar cell 1 using the amount of light as a parameter. As shown in the figure, the output voltage V and the output current ■ of the solar cell 1 change depending on the light ff1LQ, -LQ. Therefore, in order to effectively utilize the power generated by the solar cell 1 having such characteristics, the output current I and the output voltage V must be maintained so that the output becomes the maximum power point P, -P. That is, it is necessary to control the output current and the output voltage V so that the output of the solar cell 1 is on the dotted line A.

In the solar power generation device shown in FIG. 2, the maximum power point tracking control device 6 controls the output voltage V of the solar cell 1 and the output current ■ from the current sensor 8 to adjust the output of the solar cell 1 to the dotted line A in FIG. The output voltage of the DC/DC converter 5 is adjusted so that the voltage is maintained at the level above, and the charging current to the storage battery 3 and the load current to the load 4 are controlled.

[Problem that the invention seeks to solve]

In the conventional solar power generation device described above, the DC/DC converter 5 is always connected regardless of the magnitude of the input voltage and the thickness of the output voltage, so the conversion efficiency of the DC/DC converter 5 (approximately 95%). By the way, when the input voltage and the output voltage of the DC/DC converter 5 are substantially equal, the action of the DC/DC converter 5 to step up or step down the output voltage of the solar cell 1 becomes unnecessary. However, in the conventional solar power generation device shown in FIG. 2, since the input voltage and output voltage of the DC/DC converter 5 are connected even when they are close to each other, the loss caused by the DC/DC converter 5 is wasted. There is a drawback that the power is consumed, and in particular, the loss caused by the DC/DC converter 5 is an important problem that cannot be ignored in small-scale solar power generation devices.

The present invention has been made in view of the above-mentioned points, and eliminates the above-mentioned conventional drawbacks, and when the input voltage and output voltage of the DC/DC converter 5 approach
In a solar power generation device, in which the loss of the DC/DC converter 5 can be effectively used by separating the input side from the load side and directly connecting the input side to the load side, and supplying the output of the solar cell 1 directly to the storage battery 3. The object of the present invention is to provide a charging control method.

[Means for solving problems]

In order to solve the above problems, the present invention provides a solar cell and a D
In a solar power generation device comprising a C/DC converter and a storage battery connected to an output side of the DC/DC converter, a first switch that disconnects the DC/DC converter from a load side; A second switch that connects the input side of the converter directly to the load side compares the input voltage and output voltage of the DC/DC converter, and determines whether the ratio of the input voltage to the output voltage corresponds to the conversion efficiency of the DC/DC converter. When the conversion efficiency is between the reciprocals of the conversion efficiency, the first switch is opened to disconnect the DC/DC converter from the load side, and the second switch is closed to disconnect the input side of the DC/DC converter. It was configured to connect directly to the load side.

[Effect]

By configuring as above, the ratio of the input voltage to the output voltage is equal to the conversion efficiency of the DC/DC converter and the conversion efficiency, 7
When the voltage is between the reciprocals of become.

〔Example〕

FIG. 1 is a block diagram showing the system configuration of a solar power generation device to which a charging control method according to the present invention is applied. In this figure, parts given the same reference numerals as those in FIG. 2 indicate the same or equivalent parts. 11 is a switch that directly connects the input side of the DC/DC converter 5, that is, the output end of the solar cell 1 to the load side;
12 is a switch that disconnects the DC/DC converter 5 from the storage battery 3 and the load side of the load 4, and connects it to the load side; 9 is the input voltage Vi and output voltage (■) of the DC/DC converter 5; This is an input/output voltage comparison control circuit that compares the voltages and closes or opens the switch 12 and the switch 11 when the ratio reaches a predetermined relationship.

In the solar power generation device configured as described above, first, when the storage battery 3 is less than fully charged, when the switch 12 is closed, the DC voltage 1 generated by the solar cell 1 is boosted via the DC/DC converter 5. Alternatively, the voltage is stepped down, and the current and load IE current corresponding to the output voltage of the DC/DC converter 5 can be supplied to the storage battery 3 and the load 4. At this time, the input voltage Vi and input current If of the solar cell 1 to the DC/DC converter 5 are input to the maximum power point tracking control device 6, and the maximum power point tracking control device 6 controls the DC/DC converter 5. Control is performed so that battery 1 reaches its maximum output point. Second, the terminal voltage of the storage battery 3, that is, the output voltage Vo of the DC/DC converter 5, and the output voltage of the solar cell 1, that is, D C/D C
When the input voltage Vi of the converter 5 reaches a predetermined relationship, the input/output voltage comparison control circuit 9 opens the switch 12 to disconnect the DC/DC converter 5 from the so-called load side of the storage battery 3 and the load 4. Close the switch 11 and
The input side of the DC converter 5 is directly connected to the load side. As a result, the direct current generated by solar cell 1 is D C/D C
Since the power is supplied to the storage battery 3 and the load 4 without passing through the converter 5, there is no current loss caused by the DC/DC converter 5, and the power generated by the solar cell 1 can be effectively used. Further, when the storage battery 3 is charged to full charge, the input/output voltage comparison control circuit 9 detects this and opens the switch 12 to prevent the storage battery 3 from being overcharged.

Now, if the conversion efficiency of the DC/DC converter 5 (7) is Fc, and the ratio (Vo/Vi) of the output voltage Vo to the input voltage Vi of the DC/DC converter 5 is Cp, then the above DC/DC converter 5, when the relationship between the output voltage and the input voltage becomes a predetermined relationship, it means when the following equation is established.

Fc<Cp<1/Fc
(1) That is, the ratio of the output voltage VO to the input voltage Vi of the DC/DC converter 5 is between the conversion efficiency Fc of the DC/DC converter 5 and the reciprocal of the conversion efficiency 1/Fc, and this When the input voltage of the DC/DC converter 5 approaches the output voltage, the DC/DC converter 5
Therefore, the input/output voltage comparison control circuit 9 opens the switch 12 to disconnect the DC/DC converter 5 from the load side, and also opens the switch 11. Close the DC/DC converter 5
By directly connecting the input side of the
The solar cell 1 that does not pass through the DC converter 5 is directly connected to the storage battery 3
and connect to load 4. This prevents the current loss of the DC/DC converter 5 from being wasted when the output voltage vO of the DC/DC converter 5 and the input voltage Vi have the relationship expressed by the above equation (1).

As explained above, according to the above embodiment, the DC/DC
A first switch 12 that disconnects the converter 5 from the load side
and a second switch 11 that directly connects the input side of the DC/DC converter 5 to the load side, and compares the input voltage and output voltage of the DC/DC converter 5 to determine the ratio of the input voltage and output voltage. is between the conversion efficiency of the DC/DC converter 5 and the reciprocal of the conversion efficiency, the first switch 12 is opened,
Since the DC/DC converter 5 is disconnected from the load side and the second switch 11 is closed to connect the input side of the DC/DC converter 5 directly to the load side, the input voltage and output voltage are When the ratio is between the conversion efficiency of the DC/DC converter 5 and the reciprocal of the conversion efficiency, that is, DC/D
When the input voltage Vi of the C converter 5 approaches the output voltage Vo, the DC/DC converter 5 is disconnected from the load side, so the current loss of the DC/DC converter 5, which was wasted in the past, can be effectively used. I will do it.

Note that various types of maximum power point tracking control device 6 shown in FIG.
The technique orally passed down in Japanese Patent Application Laid-open No. 69 or Japanese Patent Application Laid-open No. 132174/1984 may be used.

Further, in the above embodiment, the DC/DC converter 5
is disconnected from the load side and the DC/DC converter 5
The switch 12 is used as a means to directly connect the input side of the switch to the load side.
Although the switch 11 and the switch 11 are used, the present invention is not limited to this. For example, a non-contact switching means using a semiconductor element may be used.

〔Effect of the invention〕

As explained above, according to the present invention, when the ratio of the input voltage to the output voltage of the DC/DC converter is between the conversion efficiency of the DC/DC converter and the reciprocal of the conversion efficiency, the DC
/Since the DC converter is separated from the solar power generation device,
An excellent effect can be obtained in that the loss that was conventionally consumed in a DC/DC converter can be effectively utilized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the system configuration of a solar power generation device to which the charging control method according to the present invention is applied, and FIG. 2 is a block diagram showing the system configuration of a solar power generation device equipped with a conventional DC/DC converter. Block diagram No. 3r2LJ is a diagram showing the output voltage-current characteristics of the solar cell with the amount of light as a parameter. In the figure, 1...solar battery, 3...storage battery, 4...
...Load, 5...DC/DC converter, 6...
・Maximum power point tracking control device, 8...Current sensor, 9
...Input/output voltage comparison control circuit, 11.12...
switch.

Claims (1)

[Claims] A solar cell, a DC/DC converter that boosts or steps down the DC voltage generated by the solar cell, and the DC/DC converter.
In a solar power generation device comprising a storage battery or the like connected to the output side of a converter, means is provided for separating the DC/DC converter from the load side and directly connecting the input side of the DC/DC converter to the load side, DC/DC
Compare the input voltage and output voltage of the converter, and if the ratio of the input voltage to the output voltage is between the conversion efficiency of the DC/DC converter and the reciprocal of the conversion efficiency, disconnect the DC/DC converter from the load side and A charging control method for a solar power generation device characterized by directly connecting the input side to the load side.