JPH06315231A - Charge controller and control method for battery and photovoltaic power generation system - Google Patents

Abstract

PURPOSE:To allow efficient charging of a battery almost to the full-charge while preventing overcharge. CONSTITUTION:Charging operation is started (t1, t4) when the terminal voltage of a battery is lower than VL and when the terminal voltage rises to VH (t6, t5), the charging operation is sustained for a predetermined time before the charging operation is stopped (t3, t6). This method realizes useful charging using solar cells.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar power generation system for storing power generated by a solar cell in a storage battery, and a charging control method and apparatus suitable for use in the storage battery of the system.

[0002]

2. Description of the Related Art As a solar power generation system for storing power generated by a solar cell in a storage battery, as shown in FIG. 3 or 4, the solar cell 100 and the storage battery 105 are connected via a backflow prevention diode 110, and A system in which the charging prevention circuit 115 or 117 is added is in practical use.

In the system of FIG. 3, if the terminal voltage of the storage battery 105 exceeds a certain value during charging, the thyristor 116 of the overcharge prevention circuit 115 turns on to short-circuit the output terminals of the solar cell 100 (diode 110). Is always turned off and the charging flow path is opened.) The charging of the storage battery 105 is stopped. As long as there is a generated current of the solar cell 100, that is, the charging stop state is continued until sunset. Recharging will resume after sunrise the next day.

In the system of FIG. 4, the overcharge prevention circuit 117 detects that the terminal voltage of the storage battery 105 has exceeded the charge cutoff value during charging, turns on the transistor 119, and turns on the solar cell 100. Charging is stopped by shorting the output terminals of. After that, when it is detected that the terminal voltage of the storage battery 105 has dropped to the charging restart value, the transistor 119 is turned off to restart charging.

[0005]

Lead storage batteries are mainly used as the storage batteries 105. Since lead storage batteries are vulnerable to overcharging, it is necessary to avoid overcharging the storage batteries 105. On the other hand, it is necessary to charge the storage battery 105 as efficiently as possible to a state sufficiently close to full charge.

The latter charging condition is not only important from the viewpoint of preventing over-discharge, that is, the life of the storage battery 105, but also extremely important from the purpose of installing this type of solar power generation system. That is, the generated power of the solar cell fluctuates greatly depending on the sunshine (weather) condition, and the generated power cannot be obtained at night. Depending on the season, it can be rainy or sunny for more than a week. This is because it is the purpose of installing this type of solar power generation system so that electric power can be taken out from the storage battery when necessary regardless of such fluctuations in sunshine (weather) conditions.

However, the conventional solar power generation system has the following problems. FIG. 5 shows the relationship between the temporal change of the terminal voltage of the storage battery 105 and the charge control in the system of FIG. When the terminal voltage is less than V1 at sunrise, the charging starts, and the charging is terminated when the terminal voltage rises to V1. After that, the terminal voltage decreases slowly as shown by the solid line when there is no load, and when the load is present, the terminal voltage decreases relatively rapidly as shown by the broken line and stabilizes at a certain value.

However, according to such a control method, it can be said that it is impossible to prevent overcharge and surely charge the battery to a fully charged state or a state close to the fully charged state. However, the overcharge prevention circuit 115 determines the termination of charging based on the terminal voltage (= electromotive force + charging current × internal resistance) of the storage battery 105 during charging, but the internal resistance changes considerably depending on the degree of deterioration of the storage battery 105. Moreover, the charging current fluctuates significantly depending on the conditions on the solar cell side (sunshine or weather). Therefore, it is impossible to uniquely determine the charging terminal voltage value V1 that does not cause overcharging or insufficient charging.

Further, the system of FIG. 3 has an overdischarge prevention circuit 1
Once 15 is activated, the charging is not resumed until the next day even if the charging is actually insufficient, so if the load is taken at night, over-discharging is likely to occur. Therefore, in order to avoid over-discharging in the case of continuous rainy weather, it is necessary to select the capacity of the storage battery 105 to be considerably larger than the value calculated from the maximum output of the solar cell 100, etc., which also increases the storage battery cost. there were.

FIG. 6 shows a storage battery 1 in the system of FIG.
5 shows the relationship between the time change of the terminal voltage of 05 and the charge control. Charging starts when the terminal voltage is less than V11 at sunrise and is terminated when the terminal voltage rises to V12. If the terminal voltage is no load, the terminal voltage decreases slowly as shown by the solid line and the load is applied. Even so, it drops relatively rapidly as shown by the broken line. When the terminal voltage drops to V12, charging starts again.

According to the control method of repeating the charging as described above, the charging is less likely to be insufficient as compared with the system of FIG.
However, since the storage battery 105 of the solar power generation system is often in a no-load state (or a state close to it) during the daytime, the charging suspension time T (see FIG. 6) is long and the generated power cannot be effectively used during that time. There is a problem that it is not possible to perform efficient charging by making maximum use of solar energy.
(Even when charged to about 80% of full charge,
Since the time required for the open circuit voltage to stabilize is 30 minutes or more, the rest time T is considerably long. ) In addition, if the sunset time or the weather deteriorates during the charging suspension time, charging cannot be restarted, and the problem of insufficient charging tends to occur. Therefore, it is necessary to allow a considerable margin in the capacity of the storage battery 105.

Even when there is a load, the single down time is shortened as shown by the broken line in FIG. 6, but as a result of this being repeated frequently in a short cycle, the charging efficiency is not necessarily improved. is not.

Therefore, it is an object of the present invention to provide a solar power generation system that solves the above problems. Another object of the present invention is to provide a charging control method that can be suitably applied to a storage battery or the like in a solar power generation system, and an apparatus therefor.

[0014]

According to a first aspect of the present invention, there is provided a charging method, wherein a terminal voltage of a storage battery during a charge stop is a predetermined value V by control of a device interposed between the storage battery and its charge source.
When the storage battery is less than L, charging of the storage battery by the charging source is started, and then the terminal voltage of the storage battery is a predetermined value VH (> VL).
It is characterized in that the charging of the storage battery is stopped after a lapse of a certain time from the time when the battery has risen.

According to a second aspect of the present invention, there is provided a charge control device, wherein switch means for opening and closing a charge flow path between a storage battery and its charge source, voltage monitoring means for monitoring a terminal voltage of the storage battery, and a charge flow path. When the terminal voltage of the storage battery is detected to be less than the predetermined value VL by the voltage monitoring means in the state where is opened, the charging means is closed by the switching means,
Thereafter, the control means performs control to open the charging flow path by the switch means after a predetermined time has elapsed from the time when the voltage monitoring means detects that the terminal voltage of the storage battery has risen to the predetermined value VH (> VL). It is characterized by doing.

A solar power generation system according to a third aspect of the present invention includes a storage battery, a solar cell as a charging source for the storage battery, and a charge control device according to the second aspect of the present invention. It is a configuration for controlling the charging of the storage battery by the above method.

[0017]

According to the invention of claim 1, for example, VL is selected to the same extent as the stable open terminal voltage of the storage battery in the fully charged state,
By selecting VH to be slightly higher than that, it is possible to efficiently charge the storage battery up to a fully charged state or a state close to it while preventing overcharging.

According to the second aspect of the invention, the storage battery can be efficiently charged by the charge control method of the first aspect of the invention with a simple device configuration.

According to the third aspect of the present invention, when the generated power of the solar cell can be obtained, the storage battery can be efficiently charged up to a fully charged state or a state close to the fully charged state within a range where overcharge does not occur, and insufficient charging occurs. Since it is less likely to occur, it is not necessary to give a margin to the capacity of the storage battery as in the conventional system, and the storage battery cost can be reduced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 120 denotes a charging control device according to the present invention, which is a contact point 126 of a relay 125 as a switch means.
By (normally open contact), solar cell 100 and storage battery 1
The charging flow path between 05 is directly opened and closed to control the charging of the storage battery 100. The relay 125 may be replaced with a semiconductor switch element.

The timer 125 controls the relay 125. In this embodiment, an electronic timer H3FA-BU manufactured by OMRON Corporation is used as the timer 130,
It operates in one-shot output mode. Relay 12
The excitation coil 127 of No. 5 is connected to the 13th and 16th terminals of the timer 130 in series with the storage battery 105. The set time of the timer 130 can be changed by the variable resistor 135 connected to the 21st and 23rd terminals.

The operation of the timer 130 is controlled by turning on / off the transistor 145 connected to the 4th terminal (reset) and 6th terminal (start) of the timer 130 by the output of the OP amplifier 140 which functions as a means for monitoring the storage battery terminal voltage. It is done by

As the operating voltage of the timer 130 and the OP amplifier 140, a voltage obtained by stabilizing the output voltage of the solar cell 100 by the three-terminal regulator (MC7812) 150 is used. Further, the diode string 165 connected to the output terminal of the three-terminal regulator 150 via the resistor 160 creates a reference voltage to be applied to the non-inverting input of the voltage OP amplifier 140. For the inverting input of the OP amplifier 140,
A voltage obtained by dividing the terminal voltage of the storage battery 150 by the resistor 170 and the variable resistor 175 is applied.

The operating voltage of the charging control device 120 is
It may be supplied from a power source independent of the solar cell 100.
However, if a separate power source is provided, its maintenance is required, and it is meaningless to operate the charging control device 120 when the output of the solar cell 100 is not obtained. Therefore, the configuration of this embodiment is general. Would be rational.

Further, in the present embodiment, the charging path is directly opened / closed by the relay contact 126, but the solar cell 1
The switching element (1
26 ′) may be connected and the backflow prevention diode may be turned on / off by opening / closing the switch element to indirectly open / close the charging flow path. However, in this case, the charge control device 120 is supplied from a power source independent of the solar cell 100.
It is necessary to supply the operating voltage of.

Reference numerals 180 and 185 denote light emitting diodes provided for visually confirming the operating state. Reference numeral 190 is a capacitor for absorbing output ripple or surge voltage of the solar cell 100, 191 is a capacitor for smoothing the output of the three-terminal regulator 150, 191 and 193 are capacitors required for the operation of the three-terminal regulator 150, 19
Reference numerals 4,195,196 are resistors for limiting the base current of the transistor 145 or the current of the light emitting diodes 180,185.

Next, the charge control operation of this solar power generation system will be described with reference to FIG. Here, as the storage battery 105, the stable open terminal voltage in a fully charged state is 1
It is assumed that a lead storage battery having a capacity of 120 amperes and a capacity of 120 amperes is used at 2.80 V (20 degrees Celsius), and the solar cell 100 has a general characteristic of 200 W class. In this case, the variable resistor 175 has a terminal voltage of the storage battery 105 of 12.80V.
When less than (= VL), the transistor 145 is turned on,
When the terminal voltage is 12.98 V (= VH) or higher, the transistor 145 is adjusted to be turned off, and the variable resistor 135 is adjusted so that the set time of the timer 130 is about 45 minutes. It was confirmed by experiments that good results could be obtained with such settings. However, the setting conditions are not necessarily limited to these.

At night when the power generated by the solar cell 100 is not obtained, it is natural that the exciting current does not flow through the relay exciting coil 127, and the relay contact 126 is open.

As the sun rises, the output of the solar cell 100 rises and the output voltage of the three-terminal regulator 150 rises. At this rising stage, if the terminal voltage (open terminal voltage) of the storage battery 105 is less than VL (12.80V), the inverting input voltage of the OP amplifier 140 becomes less than the non-inverting input voltage (reference voltage). A sufficient current flows from the output of the amplifier 140 to the base of the transistor 145,
The transistor 145 is turned on. As a result, the timer 130 short-circuits the 13th and 16th terminals, so that a current flows through the relay exciting coil 127. As a result, the relay contact 126 is closed, the charging current flows from the solar cell 100 to the storage battery 105, and the charging starts (time t
1).

When charging is started in this way, the terminal voltage of the storage battery 105 rises, and when it reaches VH (12.98 V), the inverting input voltage of the OP amplifier 140 becomes equal to or higher than the non-inverting input voltage, and the transistor 145 is turned on. Turn off (time t2). In the conventional system of FIG. 4, charging was stopped at this point. However, in this system, the timer 130
Since the 4th terminal (reset) and the 6th terminal (start) are driven at the same time, since the 13th and 16th terminals are not opened at this time, charging continues.

Then, from the time t2, a set time (45 minutes)
At time (t3), the timer 130 opens the terminals 13 and 16 to cut off the exciting current to the relay exciting coil 127. As a result, the relay contact 126 opens, the solar cell 100 is disconnected from the storage battery 105, and charging stops.

As described above, the charging is not immediately stopped when the terminal voltage rises to VH, but the charging is not performed for a fixed time after that, so that the charging is efficiently performed in a shorter time than the conventional system of FIG. It can be charged to full charge or close to it. This means that the solar battery 10 whose generated power depends on weather changes and time of day
A solar power generation system using 0 as a charging source has an extremely large effect.

In addition, from time t2 to time t3,
The terminal voltage of the storage battery 105 is VL (12.
When the voltage drops to less than 80 V and the transistor 145 is turned on, charging continues until the set time elapses from that time.

The next charging starts when the terminal voltage is VL.
It is time t4 when the voltage falls below (12.80 V) and the transistor 145 is turned on. Also in this case, charging continues until the set time elapses from time t5 when the terminal voltage rises to VH (12.98V) and the transistor 145 is turned off thereafter.

As described above, the charging is performed again even when the terminal is not fully charged in the previous charging or when the terminal voltage drops due to the load being connected to the storage battery 105. There is no problem like the conventional system of No. 3.

The charging control device of the present invention is most suitable for controlling the charging of the storage battery of the solar power generation system described above, but is weak against overcharging and needs to be maintained at or near full charge. It can be effectively applied to general charge control.

[0037]

As described above in detail, according to the present invention, the following effects can be obtained. (1) It is possible to efficiently charge the storage battery to a fully charged state or a state close to the fully charged state within a range where overcharge does not occur. (2) Such efficient charging control can be performed with a simple device configuration. (3) In the solar power generation system, when the generated power can be obtained in sunny weather, the storage battery can be efficiently charged to a full charge or a state close to it within a range where overcharge does not occur, resulting in insufficient charging. Hateful. As a result, even if the storage battery's capacity is not excessively large, it is less likely to be over-discharged in the case of continuous rain,
The storage battery cost can be reduced.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 shows a relationship between time change of a storage battery terminal voltage and charge control in the solar power generation system of the same embodiment.

FIG. 3 shows a conventional example of a solar power generation system.

FIG. 4 shows another conventional example of a solar power generation system.

FIG. 5 shows a time change of a storage battery terminal voltage and charge control in the system of FIG.

FIG. 6 shows a time change of a storage battery terminal voltage and charge control in the system of FIG.

[Explanation of symbols]

 100 Solar Battery (Charging Source) 105 Storage Battery (Lead Storage Battery) 110 Backflow Prevention Diode 120 Charge Control Device 125 Relay (Switch Means) 130 Timer 135 Variable Resistor 140 OP Amp (Comparator) 145 Transistor 150 Three-Terminal Regulator 165 Diode Array 175 Variable resistor

Claims (3)

[Claims] 1. The control of a device interposed between the storage battery and its charging source causes the charging source to start charging the storage battery when the terminal voltage during charging stop of the storage battery is less than a predetermined value VL. Then, after that, charging of the storage battery is stopped after a lapse of a certain time from when the terminal voltage of the storage battery rises to a predetermined value VH (> VL). 2. A switch means for opening and closing a charging flow path between the storage battery and its charging source, a voltage monitoring means for monitoring a terminal voltage of the storage battery, and the charging flow path in the opened state. When the voltage monitoring means detects that the terminal voltage of the storage battery is less than the predetermined value VL, the switch means closes the charging flow path, and thereafter,
Control means for controlling the opening of the charging flow path by the switch means after a lapse of a fixed time from the time when the voltage monitoring means detects that the terminal voltage of the storage battery has risen to a predetermined value VH (> VL). A charging control device comprising: 3. A storage battery, a solar cell as a charging source thereof, and a charge control device, wherein the charge control device opens and closes a charging flow path between the storage battery and the solar cell. Means, voltage monitoring means for monitoring the terminal voltage of the storage battery, and when the voltage monitoring means detects that the terminal voltage of the storage battery is less than a predetermined value VL in a state where the charging flow path is opened. The charging means is closed by the switch means, and then the terminal voltage of the storage battery is set to a predetermined value VH (> V) by the voltage monitoring means.
L), a solar power generation system comprising: a control unit that performs control to open the charging flow path by the switch unit after a lapse of a certain time from when it is detected that the temperature has risen to L).