JP2010063307A - Charging circuit and charging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently charge a storage battery by preventing deterioration of the storage battery due to a very small charging current. <P>SOLUTION: A current measuring unit 7 measures a current which is caused to flow to a solar battery 1 from an inductor 4 connected thereto. When the magnitude of the measured current exceeds a first threshold value, a control unit 8 executes control so that a charging current is caused to flow from the inductor 4 to an assembled battery 2. On the other hand, if the magnitude of the measured current becomes a second threshold value smaller than the first threshold value or below, the control unit 8 executes control so that a current returns from the inductor 4 to the solar battery 1 without going through the assembled battery 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging circuit and a charging method for charging an electric power generated by a solar battery to a storage battery, and more particularly to a charging circuit and a charging method capable of preventing deterioration of the storage battery due to a minute charging current.

  Conventionally, when weather observation or monitoring is performed in a place where it is difficult to secure a power supply infrastructure, a solar cell system combining a solar cell and a storage battery can be used as a power source for data collection and information transmission. In the solar cell system, for example, power generated by the solar cell is supplied to the load during the daytime, the storage battery is charged with surplus power, and necessary power is supplied by discharging from the storage battery at night.

  As an example of such a solar cell system, for example, Patent Documents 1 and 2 describe an independent solar power generation system in which a storage battery and a solar cell are combined. Specifically, Patent Document 1 discloses a Ni-MH (nickel-hydrogen) storage battery that is charged by a first converter connected to the output of the solar battery and a charger connected to the output of the first converter. And a second converter connected to the output of the first converter and the output of the electric double layer capacitor and connected to the Ni-MH battery via a backflow prevention diode, and connected to the output of the second converter. A stand-alone photovoltaic system with a load is described.

  Patent Document 2 discloses a solar cell that generates electric power by sunlight, a converter connected to the output of the solar cell, an electric double layer capacitor connected to the output of the converter, an output of the converter, and an electric double layer. Independent solar light comprising a plurality of chargers connected to capacitors, a plurality of Ni-MH batteries connected corresponding to the chargers, and a load connected to the outputs of the plurality of Ni-MH batteries A power generation system is described.

  Thus, when charging a storage battery with a solar battery, it is common to charge via a converter. The converter outputs a constant voltage to the storage battery with the solar battery as an input, and matches the output voltage with the charging voltage of the storage battery. Here, the generated electric power of the solar cell greatly fluctuates due to sunlight, but the fluctuation appears as an increase or decrease in the output current (charging current) of the converter. That is, even if the power generation amount decreases, the output voltage (charging voltage) of the converter does not change, and the output current (charging current) decreases.

JP 2000-250646 A JP 2001-069688 A

  However, normally, the optimum value is set for the charging current of the storage battery, and when the charging current becomes very small, the charging efficiency is remarkably lowered and the storage battery is not charged. In that case, most of the electric power input to the storage battery is converted into heat, but there is a problem that the deterioration of the storage battery proceeds due to this exothermic reaction.

  The present invention has been made to solve the above-described problems caused by the prior art, and an object thereof is to provide a charging circuit and a charging method capable of preventing deterioration of a storage battery due to a minute charging current.

  In order to solve the above-described problems and achieve the object, the present invention is a charging circuit for charging a storage battery with electric power generated by a solar battery, the inductance connected to the solar battery, and the solar battery from the solar battery. A current measuring means for measuring the current flowing to the inductance, and when the magnitude of the current measured by the current measuring means exceeds a first threshold, control so that a charging current flows from the inductance to the storage battery, Charge control means for controlling the current to return from the inductance to the solar cell without going through the storage battery when the magnitude of the measured current is equal to or smaller than a second threshold value smaller than the first threshold value. And.

  Further, the present invention is a charging method for charging a storage battery with electric power generated by a solar battery, the step of measuring the current flowing from the solar battery to an inductance connected to the solar battery, and the measurement of the measured current When the magnitude exceeds a first threshold, control is performed so that a charging current flows from the inductance to the storage battery, and the magnitude of the measured current is less than or equal to a second threshold smaller than the first threshold. And the step of controlling the current to return from the inductance to the solar cell without going through the storage battery.

  According to the present invention, there is an effect that it is possible to prevent the storage battery from being deteriorated due to a minute charging current and to charge efficiently.

  Exemplary embodiments of a charging circuit and a charging method according to the present invention will be explained below in detail with reference to the accompanying drawings. In addition, a present Example demonstrates the case where this invention is applied to the solar cell system which combined the solar cell and the storage battery, and demonstrates centering on the case where the electric power generated by the solar cell is charged to a storage battery.

  First, the structure of the solar cell system according to the present embodiment will be described. FIG. 1 is a block diagram illustrating a configuration of a solar cell system according to the present embodiment. As shown in the figure, this solar cell system includes a solar cell 1, an assembled battery 2, a series resistor 3, an inductance 4, a switching element 5, a diode 6, a current measuring unit 7, and a control unit 8. With.

  Of the two electric circuits connecting the solar cell 1 and the assembled battery 2, a series resistor 3, an inductance 4, and a diode 6 are inserted into one of the electric circuits in order from the solar cell 1 side. The electric circuit between the inductance 4 and the diode 6 is connected to the other electric circuit connecting the solar cell 1 and the assembled battery 2 via the switching element 5.

  Here, the series resistor 3, the inductance 4, the switching element 5, the diode 6, the current measuring unit 7, and the control unit 8 constitute a charging circuit that charges the assembled battery 2 with the electric power generated by the solar cell 1.

  The solar cell 1 generates electric power by converting solar energy into electric energy. For example, this solar cell 1 has a maximum power generation capacity of 90 W, an open circuit voltage of 20 V, and a short circuit current with a maximum value of 5 A.

The assembled battery 2 stores the electric power generated by the solar battery 1. For example, the assembled battery 2 is configured by connecting a plurality of Ni-MH storage batteries in 10 cells in series. Here, as each Ni-MH storage battery, for example, a rated voltage of 1.2 V, a rated capacity of 100 Ah, a maximum charging voltage of 1.6 V, and a discharge end voltage of 1.0 V are used. In this case, the maximum charging voltage (V _H ) of the assembled battery 2 is 16V, and the final discharge voltage (V _L ) is 10V.

  The series resistor 3 is used for current measurement, and its resistance value is negligibly small.

  The inductance 4 is, for example, a coil and has a property of holding a current output from the solar cell 1.

  The switching element 5 controls the supply of the charging current to the assembled battery 2 under the control of the control unit 8. When the switching element 5 is turned off (non-conducting state), a charging current flows from the inductance 4 to the assembled battery 2 via the diode 6. On the other hand, when the switching element 5 is turned on (conductive state), the current returns from the inductance 4 to the solar cell 1 via the switching element 5.

  The diode 6 has an anode terminal connected to the inductance 4 and a cathode terminal connected to the assembled battery 2. The direction of the current flowing to the assembled battery 2 is controlled by the diode 6 only in the direction in which the assembled battery 2 is charged.

  The current measuring unit 7 measures the current flowing from the solar cell 1 to the inductance 4. Specifically, the current measuring unit 7 measures a current flowing from the solar cell 1 to the inductance 4 by measuring a voltage generated at both ends of the series resistor 3.

  In addition, although a present Example demonstrates the case where a current is measured using the series resistance 3, the method of measuring the electric current which flows into the inductance 4 from the solar cell 1 is not necessarily restricted to this. For example, a component capable of measuring the magnitude of the magnetic field generated around the current and outputting a voltage corresponding to the measured magnitude of the magnetic field may be used. In that case, the said component is connected between the solar cell 1 and the inductance 4, and the output current from the solar cell 1 is made to conduct | electrically_connect to a component. And the current measurement part 7 measures the electric current which flows from the solar cell 1 to the inductance 4 by measuring the voltage output from components.

  The control unit 8 controls the supply of the charging current to the assembled battery 2 by switching on / off the switching element 5 based on the magnitude of the current measured by the current measuring unit 7. The control unit 8 constitutes a charge control means by cooperating with the switching element 5 and the diode 6.

  Specifically, the control unit 8 turns off the switching element 5 when the magnitude of the current measured by the current measurement unit 7 exceeds the first threshold value. Thereby, a charging current flows from the inductance 4 to the assembled battery 2. That is, the current output from the solar cell 1 returns to the solar cell 1 via the series resistor 3, the inductance 4, the diode 6, and the assembled battery 2 (the flow of the loop 2 shown in FIG. 1).

  On the other hand, the control unit 8 turns on the switching element 5 when the magnitude of the current measured by the current measurement unit 7 is equal to or smaller than a second threshold value that is smaller than the first threshold value. Thereby, the current returns from the inductance 4 to the solar cell 1 without passing through the assembled battery 2. At this time, since the diode 6 is connected to the assembled battery 2, the assembled battery 2 is not short-circuited by the switching element 5. That is, the current output from the solar cell 1 returns to the solar cell 1 via the series resistor 3, the inductance 4, and the switching element 5 (the flow of the loop 1 shown in FIG. 1).

  Here, the relationship between the current flowing from the solar cell 1 to the inductance 4 and the charging current supplied to the assembled battery 2 as a result of the control by the control unit 8 will be described. FIG. 2 is a diagram for explaining the relationship between the current flowing from the solar cell 1 to the inductance 4 and the charging current supplied to the assembled battery 2.

In the figure, (a) shows the change over time of the current _Ip output from the solar cell 1, the vertical axis shows the magnitude of the current _Ip , and the horizontal axis shows the time t. . On the other hand, (b) shows the change over time of the charging current I _C supplied to the assembled battery 2, the vertical axis shows the magnitude of the charging current I _C , and the horizontal axis shows the time t. .

Further, in the figure (a) and (b), I ₁ denotes the first threshold value, I ₂ represents a second threshold value. These I ₁ and I ₂ have a relationship of I ₁ > I ₂ , and I ₂ is set to be equal to or higher than the minimum current that can charge the assembled battery 2. For example, the first threshold value _{I 1} is 1A, the second threshold value _{I 2} is set to 0.5A.

First, as shown in the figure, it is assumed that at the time of t = 0, I _p and I _C are 0 and the switching element 5 is turned on.

When the time t elapses, I _p gradually increases as shown in FIG. Then, when I _p exceeds I ₁ , the control unit 8 turns off the switching element 5. As a result, the charging current I _C flows through the assembled battery 2 as shown in FIG.

Thereafter, when the time t further elapses, I _p gradually decreases as shown in FIG. Then, when I _p becomes I ₂ or less, the control unit 8 turns on the switching element 5. Thus, as shown in the same figure (b), the charging current I _C flowing through the assembled battery 2 becomes zero.

As described above, the control unit 8 repeats the control of the charging current I _C based on the change in the current I _p output from the solar cell 1, whereby the pulsed charging current I _C is sequentially supplied to the assembled battery 2. The

For example, many solar radiation, when the power generation by the solar cell 1 is sufficiently performed, I _p is I ₂ greater than, in other words, when the switching element 5 is turned off to continue. Therefore, in this state, the assembled battery 2 continues to be charged with a charging current I _C that is greater than or equal to the minimum charging current.

When the amount of solar radiation decreases during charging, the switching element 5 is turned on when the current _Ip flowing from the solar cell 1 to the inductance 4 becomes I ₂ or less. Here, if the addition amount of solar radiation is lowered, I _p becomes not reach the I _1, the state switching element 5 is ON continues. Therefore, in this state, charging of the assembled battery 2 is completely stopped.

  Next, the procedure of the charging method in the solar cell system according to the present embodiment will be described. FIG. 3 is a flowchart showing the procedure of the charging method in the solar cell system according to this example.

  As shown in the figure, in this solar cell system, first, the control unit 8 turns on the switching element 5 (step S1). Thereby, the current returns from the inductance 4 to the solar cell 1 without passing through the assembled battery 2.

Thereafter, the current measuring unit 7 measures the current I _p output from the solar cell 1 (step S2), and the control unit 8 determines whether or not the measured current I _p exceeds the first threshold value I ₁ . Determine.

Then, the current _{I p} is in the case of not exceed the first threshold value _{I 1} (step S3, Yes), the control unit 8 turns off the switching element 5 (step S4). Thereby, a charging current flows from the inductance 4 to the assembled battery 2.

Thereafter, the current measuring unit 7 continues the measurement of the current I _p (step S5), and the control unit 8 determines whether the measured current I _p becomes the second threshold value I ₂ below.

Then, the current _{I p} is in the case of a second threshold value _{I 2} below (step S6, Yes), the control unit 8 turns on the switching element 5 (step S1). Thereby, the current returns from the inductance 4 to the solar cell 1 without passing through the assembled battery 2.

  By repeating the above procedure, the solar cell system intermittently repeats charging of the assembled battery 2.

  As described above, in this embodiment, the current measuring unit 7 measures the current flowing from the solar cell 1 to the inductance 4 connected to the solar cell 1. Then, the control unit 8 performs control so that the charging current flows from the inductance 4 to the assembled battery 2 when the magnitude of the measured current exceeds the first threshold value. On the other hand, the control unit 8 causes the current to return from the inductance 4 to the solar cell 1 without passing through the assembled battery 2 when the magnitude of the measured current becomes equal to or smaller than the second threshold value that is smaller than the first threshold value. To control.

  As a result, the charging current lower than the second threshold value does not flow to the assembled battery 2, so that it is possible to prevent the assembled battery 2 from being deteriorated by a minute charging current. In addition, since it is possible to prevent a decrease in charging efficiency due to a minute charging current being supplied to the assembled battery 2, it is possible to charge the assembled battery 2 efficiently.

  In the present embodiment, the second threshold value is set to be equal to or larger than the minimum current that can charge the assembled battery 2, so that a charging current that is so small that charging is impossible is set. Supply to the battery 2 can be prevented, and the assembled battery 2 can be more efficiently charged.

  In addition, although the present Example demonstrated the case where the assembled battery 2 comprised from a some Ni-MH storage battery was used, this invention is not restricted to this, The case where another kind of storage battery is used But it can be applied as well. That is, the same effect as in the present embodiment can be obtained if a storage battery that is deteriorated by a minute charging current or has a lower charging efficiency is used as in the case of the Ni-MH storage battery.

  As described above, the charging circuit and the charging method according to the present invention are useful when charging the storage battery with the electric power generated by the solar battery, and in particular, the deterioration of the storage battery and the reduction of the charging efficiency due to a small charging current. Suitable for cases where prevention is required.

It is a block diagram which shows the structure of the solar cell system which concerns on a present Example. It is a figure for demonstrating the relationship between the electric current which flows into an inductance from a solar cell, and the charging current supplied to an assembled battery. It is a flowchart which shows the procedure of the charging method in the solar cell system which concerns on a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Assembly battery 3 Series resistance 4 Inductance 5 Switching element 6 Diode 7 Current measurement part 8 Control part

Claims (5)

A charging circuit for charging a storage battery with electric power generated by a solar battery,
An inductance connected to the solar cell;
Current measuring means for measuring a current flowing from the solar cell to the inductance; and
When the magnitude of the current measured by the current measuring means exceeds a first threshold, control is performed so that a charging current flows from the inductance to the storage battery, and the magnitude of the measured current is the first Charge control means for controlling the current to return from the inductance to the solar cell without going through the storage battery when the second threshold value is less than the second threshold value,
A charging circuit comprising: The charge control means includes
Control is performed so that a charging current flows from the inductance to the storage battery when the battery is in a non-conducting state. Switch means to control;
When the magnitude of the current measured by the current measuring means exceeds the first threshold value, the switch means is brought into a non-conductive state, and the magnitude of the measured current is equal to or less than the second threshold value. Switch control means for bringing the switch means into a conductive state,
The charging circuit according to claim 1, further comprising:   3. The charging circuit according to claim 1, wherein the second threshold value is set so as to be equal to or greater than a minimum current capable of charging the storage battery.   The charging circuit according to claim 3, wherein the second threshold value is set so as to be a minimum current capable of charging the storage battery. A charging method for charging a storage battery with electric power generated by a solar battery,
Measuring the current flowing from the solar cell to the inductance connected to the solar cell;
When the measured current exceeds a first threshold, control is performed so that a charging current flows from the inductance to the storage battery, and the measured current is smaller than the first threshold. A step of controlling the current to return from the inductance to the solar cell without going through the storage battery when the threshold value is less than or equal to two threshold values;
The charging method characterized by including.

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