JP2010259261A - Apparatus and method for charging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently charge a battery pack (storage battery) by preventing deterioration of the battery pack (storage battery) due to a very small charging current. <P>SOLUTION: A control part 7 stores a predetermined time which is a time equal to or more than the charge time required for charging the battery pack 5, and a predetermined voltage which is a voltage value allowing a charging current, flowing into a power storage battery by being discharged from a capacitor 3 by turning on a switch 6, to have a value equal to or higher than the lowest current value required for charging the battery pack 5 during a period when the predetermined time elapses. Then, the control part 7 controls the switch 6 to be switched on so that an electric charge accumulated in the capacitor 3 is charged into the battery pack 5 when a voltage of the capacitor 3 accumulating an output power of a solar cell 1 reaches a predetermined voltage, and also controls the switch 6 to be switched off so that the output power from the solar cell 1 is charged into the capacitor 3 when the predetermined time elapses from the point at which the voltage of the capacitor 3 reaches the predetermined voltage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charging device and a charging method.

  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, an independent solar power generation system in which a storage battery and a solar cell are combined is known. Specifically, a first converter connected to the output of the solar cell, a Ni-MH (nickel / hydrogen) storage battery charged by a charger connected to the output of the first converter, and the first converter And a second converter connected to the output of the electric double layer capacitor and connected to the Ni-MH battery via a backflow prevention diode, and a load connected to the output of the second converter An independent solar power generation system is known (see, for example, Patent Document 1).

  In addition, a solar cell that generates 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, and a plurality connected to the output of the converter and the electric double layer capacitor There is also known a stand-alone photovoltaic power generation system including a battery charger, a plurality of Ni-MH batteries connected to the chargers, and a load connected to outputs of the plurality of Ni-MH batteries. (For example, refer to Patent Document 2).

  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 provides a charging device and a charging method capable of preventing the deterioration of a storage battery due to a minute charging current and charging efficiently. With the goal.

  In order to solve the above-described problems and achieve the object, this device is a charging device that charges output power from a solar cell to a storage battery with a DC circuit, and a capacitor connected in parallel with the solar cell; A switch for switching charging / discharging of the capacitor, and switching the switch so that when the voltage of the capacitor reaches a predetermined voltage, the charge accumulated in the capacitor is discharged and charged to the storage battery. Control means for controlling the switch so that the output power from the solar cell is charged in the capacitor when a predetermined time has elapsed from the time when the voltage of the capacitor becomes the predetermined voltage. It is a requirement that

  Further, this method is a charging method in which the output power from the solar cell is charged to the storage battery in a DC circuit having a capacitor connected in parallel with the solar cell and a switch for switching charging / discharging of the capacitor. And when the voltage of the capacitor reaches a predetermined voltage, control is performed to switch the switch so that the electric charge accumulated in the capacitor is discharged and charged to the storage battery, and the voltage of the capacitor is It is a requirement to include a control step of controlling the switch so that the output power from the solar cell is charged in the capacitor when a predetermined time has elapsed from the time when the voltage is reached.

  According to the disclosed apparatus and method, it is possible to prevent the storage battery from being deteriorated due to a minute charging current and to efficiently charge the battery.

FIG. 1 is a diagram for explaining the configuration of the charging apparatus according to the present embodiment. FIG. 2 is a diagram for explaining a circuit when the switch is turned on in the charging device according to the present embodiment. FIG. 3 is a diagram for explaining the transition of the voltage of the parallel circuit and the charging current of the assembled battery during the operation of the charging device according to the present embodiment. FIG. 4 is a flowchart for explaining processing of the charging device in the embodiment.

  Embodiments of a charging device and a charging method according to the present invention will be described below with reference to the accompanying drawings. In the first embodiment, a charging device that executes the charging method according to the present invention will be described as an embodiment.

  First, the structure of the charging device in a present Example is demonstrated. FIG. 1 is a diagram for explaining the configuration of the charging apparatus according to the present embodiment. As shown in FIG. 1, the charging device in the present embodiment includes a solar cell 1, a diode 2, a capacitor 3, an assembled battery 5, a switch 6, and a control unit 7.

  The solar cell 1 is a device that generates direct-current power by sunlight, and is connected in series with a diode 2 and further connected in parallel with a capacitor 3. That is, the solar cell 1 and the capacitor 3 constitute a parallel circuit 4 as shown by a dotted frame in FIG. The parallel circuit 4 can be connected to the assembled battery 5 via the switch 6.

  The diode 2 is an electronic element having a rectifying action. In the charging device according to this embodiment, the anode and cathode terminals of the diode 2 are connected as shown in FIG. Is prevented from flowing backward from the solar cell 1 to the solar cell 1.

  The capacitor 3 accumulates (charges) electric charge with the DC power output from the solar cell 1, and discharges the accumulated electric charge to the assembled battery 5. The charging / discharging of the capacitor 3 is controlled by opening / closing the switch 6.

  The assembled battery 5 has a configuration in which a plurality of storage batteries are connected in series or in parallel, and the output power of the solar cell 1 is charged by a DC circuit. Specifically, the assembled battery 5 in the present embodiment charges the electric charges discharged from the capacitor 3 that stores the DC power output from the solar battery 1. For example, the assembled battery 5 in the present embodiment is configured such that “nominal voltage: 12 V, nominal capacity: 100 Ah” is obtained by connecting in series 10 nickel-metal hydride storage battery cells having “nominal voltage: 1.2 V, nominal capacity: 100 Ah”. And has a power storage capacity of 1200 Wh.

Here, the assembled battery 5 has a minimum chargeable current. For example, in a nickel metal hydride storage battery cell, a charge current of 1 A is required at the minimum. If the charging is continued below the minimum current, the charging efficiency is remarkably lowered and the deterioration of the storage battery is promoted. Therefore, it is desirable that the assembled battery 5 is charged at the minimum current or more. For this reason, in this embodiment, for example, “1A” is determined as the minimum current “I _d ”.

Even if the charging current exceeds the minimum current, if the charging time is short, the assembled battery 5 does not cause a reaction that contributes to charging. For this reason, in the present embodiment, for example, “1 ms” is determined as the charging time “T _d ” required for charging the assembled battery 5.

  The switch 6 switches charging / discharging of the capacitor 3 under the control of the control unit 7 described later. That is, when the switch 6 is OFF (closed), the parallel circuit 4 and the assembled battery 5 are disconnected, and the output power of the solar battery 1 is charged to the capacitor 3. Further, when the switch 6 is ON (open), the parallel circuit 4 and the assembled battery 5 are connected, and the charge accumulated in the capacitor 3 is discharged to the assembled battery 5 and charged by the assembled battery 5. The

  For example, the switch 6 in this embodiment is realized by an FET (Field Effect Transistor) that is a switching element, and the control unit 7 described later transmits an ON signal to the control electrode of the switch 6 that is the switching element. Thus, the switch 6 is turned on and the switch 6 is turned off by resetting the ON signal.

  In the present embodiment, the case where the FET is the switch 6 will be described. However, the present invention is not limited to this, and if the switch has a function of switching charging / discharging of the capacitor 3, the switch 6 is used. It can be incorporated into a charging device.

  Thus, the charging device in the present embodiment is a DC circuit in which the parallel circuit 4 in which the solar cell 1 and the capacitor 3 are connected in parallel can be connected to the assembled battery 5 via the switch 6 that switches between charging and discharging of the capacitor 3. In the solar cell system, the output power from the solar cell 1 is stored in the capacitor 3 and then charged to the assembled battery 5. The following is a detailed description of the process using the control unit 7 described in detail. The main feature is that the battery 5 can be prevented from being deteriorated and charged efficiently.

  This main feature will be described with reference to FIGS. 2 and 3 together with FIG. FIG. 2 is a diagram for explaining a circuit when the switch is turned on in the charging device in the present embodiment, and FIG. 3 shows the voltage of the parallel circuit during operation of the charging device in the present embodiment. It is a figure for demonstrating transition of the charging current of an assembled battery.

  The control unit 7 shown in FIG. 1 switches the switch 6 to ON so that when the voltage of the capacitor 3 becomes a predetermined voltage, the charge accumulated in the capacitor 3 is discharged and charged to the assembled battery 5. The switch is turned off so that the output power from the solar cell 1 is charged in the capacitor 3 when a predetermined time has elapsed from the time when the voltage of the capacitor 3 becomes a predetermined voltage. That is, the condition for turning on the switch 6 is when the voltage of the parallel circuit 4 equal to the voltage across the capacitor 3 becomes equal to or higher than the predetermined voltage, and the condition for turning off the switch 6 is predetermined after the ON state. The time has passed.

Here, the “predetermined time” and the “predetermined voltage” used when the control unit 7 performs switching control of ON / OFF of the switch 6 are set as follows. In other words, "predetermined time" is the charging time required for the assembled battery 5 is charged "T _d" or longer, the "predetermined voltage", by the switch 6 is ON, the capacitor 3 The value of the charging current that flows into the storage battery by being discharged is a voltage value that is equal to or greater than the minimum current value “I _d ” required for charging the assembled battery 5 until the “predetermined time” elapses. Hereinafter, a calculation method for calculating “predetermined time” and “predetermined voltage” will be described.

  First, when the switch 6 is ON, the magnitude of the charging current flowing from the capacitor 3 to the assembled battery 5 and the change with time of the magnitude of the charging current are as follows: the capacity of the capacitor 3 and the voltage value of the assembled battery 5 The voltage can be calculated in advance from the internal resistance value of the assembled battery 5 and the voltage value of the parallel circuit 4 at the moment when the switch 6 is turned on.

  This will be described with reference to the circuit configuration shown in FIG. In addition, since the condition which switches ON / OFF of the switch 6 is determined in order to prevent deterioration of the assembled battery 5 due to a minute charging current and to efficiently charge the battery, it is assumed that the amount of solar radiation is small. In the circuit shown in FIG. 1, the solar cell 1 shown in FIG. 1 is omitted.

  First, in the circuit of FIG. 2, the charge stored in the capacitor 3 having the capacity “C” is “q”. In the circuit of FIG. 2, the assembled battery 5 is represented by a series connection of a voltage source 8 having a voltage value “Vb” and an internal resistor 9 having a resistance value “R”. The direction in which i ”flows is the direction in which the assembled battery 5 is charged. Note that “v” shown in FIG. 2 is the voltage of the parallel circuit 4 determined by the accumulated charge “q”.

  Here, when Kirchhoff's voltage law is applied to the circuit of FIG. 2, the following equation (1) is obtained.

  Further, the following relational expression (2) is established between the change amount of the accumulated charge “q” with the elapsed time “t” and the charging current “i” from the capacitor 3.

Then, by solving equation (1) using equation (2), equation (3) shown below is obtained. Note that “i ₀ ” in Equation (3) is a current value (current initial value) immediately after the switch 6 is turned on.

Here, since the voltage at both ends of the parallel circuit 4 is a continuous value even when the switch 6 is turned on, the voltage “V ₁ ” and the current initial value “i ₀ ” when the switch 6 is turned on are The following equation (4) holds.

Therefore, the current initial value “i ₀ ” is obtained by the following equation (5).

According to the equation (3), the charging current value “i” at the elapsed time “t” is expressed as decay from the current initial value “i ₀ ”, and the charging time is related to “RC” which is a time constant. . For example, when the charging time, that is, the “predetermined time” described above is defined as a time “t _1/2 ” in which the current initial value “i ₀ ” decreases to half in Equation (3), “i = i ₀ / Since “2”, “t _1/2 ” is obtained by the following equation (6).

Here, the charging current at the time has elapsed "t _1/2", since it is "i _0/2", after the switch 6 is turned ON until after the "t _1/2", the charge conditions for the assembled battery 5 is charged with the lowest current "I _d" than necessary, "i _0/2 ≧ I _d" and by the equation (5), the formula (7) shown below.

The condition for the assembled battery 5 is charged by the charging time "T _d" or more, since it is "t _1/2 ≧ T _d", the equation (6), and Equation (8) below Become.

That is, by setting “V ₁ ” and “t _1/2 = RCn2” satisfying the expressions (7) and (8) to “predetermined voltage” and “predetermined time”, the assembled battery 5 With a current value equal to or greater than “I _d ”, the capacitor 3 is continuously charged by discharging from the capacitor 3 with a charging time equal to or greater than “T _d ”. That is, even when there is little sunlight, the assembled battery 5 is efficiently charged without deterioration.

For example, from the data of the assembled battery 5 incorporated in the charging device, “Vb = 12 V (nominal voltage)”, “R = 1Ω”, “I _d = 1 A”, and “T _d = 1 ms”. If it is known, “V ₁ ” is “14 V” or more and “C” is “1.44 mF” or more from equations (7) and (8). Therefore, the administrator of the charging device selects the capacitor 3 having a capacity close to “1.44 mF”, sets the predetermined voltage to “14 V”, and sets the predetermined time to “1 ms”. 7 is stored in the internal memory.

  And the control part 7 starts charge of the capacitor | condenser 3 by controlling the switch 6 to be turned OFF when the operation of the charging device is started, and as shown in FIG. Measurement of the voltage “v” is started. Then, the control unit 7 starts charging the assembled battery 5 by controlling the switch 6 to be turned on when the voltage “v” becomes “14V”, and the switch 6 is turned on. When “1 ms” elapses from the time point, the switch 6 is controlled to be turned OFF to finish charging the assembled battery 5 and start charging the capacitor 3 again.

In the above description, the case where the “predetermined time” is set to the time “t _1/2 ” when the current initial value “i ₀ ” is reduced to half has been described, but the present invention is not limited to this. Instead, for example, the “predetermined time” may be set as a time when the current initial value decreases to an arbitrary value, such as a time when the current initial value “i ₀ ” decreases to 1/10.

Here, the case where the “predetermined time” is generally set as the time “t _{1 / a} ” when the current initial value “i ₀ ” decreases to _{1 / a} will be described. “A” is defined as a real number of 1 or more.

First, “t _{1 / a} ” is obtained from Expression (3) according to Expression (9) shown below.

Therefore, the condition for charging the battery pack 5 at the minimum current “I _d ” or more necessary for charging until “t _{1 / a} ” elapses after the switch 6 is turned on is “i ₀ / a ≧ Since “I _d ”, the following equation (10) is obtained from equation (5).

Further, since the condition for charging the assembled battery 5 in the charging time “T _d ” or longer is “t _{1 / a} ≧ T _d ”, the following equation (11) is obtained from the equation (9). Become.

That is, “V ₁ ” and “t _{1 / a} = RClna” satisfying the expressions (10) and (11) are defined as “predetermined voltage” and “predetermined time”.

For example, if “Vb”, “R”, “I _d ”, and “T _d ” are already known from the data of the assembled battery 5 incorporated in the charging device, the administrator sets “V ₁ ” to the formula (10). The capacitor 3 having a capacity close to the value of “C” that satisfies the equation (11) is selected, and the known “T _d ” is set as a predetermined time (charging time). Operate the device.

In addition, the administrator obtains “C” and “a” satisfying Expression (10) and Expression (11) from “V ₁ ” set in advance, and selects the capacitor 3 and sets a predetermined time (charging time). A decision may be made.

Alternatively, the administrator obtains “V ₁ ” and “a” by using the capacity “C” of the capacitor 3 that has been selected in advance by using the expressions (10) and (11), and the predetermined voltage Further, a predetermined time may be determined.

In the above, the description has been given of the case of determining expression when equality holds in (10) to "V _1" as the predetermined voltage, the present invention is not limited to this, Equation (10) and the formula If (11) is satisfied, “V ₁ ” in which the left side is larger than the right side in Equation (10) may be determined as the predetermined voltage.

In the above description, the case where the predetermined time “RClna” is set as “T _d ” has been described. However, the present invention is not limited to this, and the expression (10) and the expression (11) are satisfied. For example, the predetermined time “RClna” may be set as a value larger than “T _d ”.

  Here, the transition of the voltage “v” of the parallel circuit 4 and the charging current “i” of the assembled battery 5 during operation of the charging device in the present embodiment will be described again with reference to FIG.

As shown in FIG. 3, when the voltage “v” of the parallel circuit 4 reaches a predetermined voltage “V ₁ ”, the switch 6 is turned on by the control unit 7, and the assembled battery 5 at the current initial value “i ₀ ”. Charging starts. The switch 6 is turned off by the control unit 7 when the predetermined time “t _{1 / a} = RClna” elapses and the charging current “i” decreases to “i ₀ / a”. The operation of the switch 6 is repeated by the processing of the control unit 7 in which a predetermined voltage and a predetermined time are set in the internal memory, and the time required for charging the assembled battery 5 (or the time required for charging the assembled battery 5 is exceeded. For a long time), the assembled battery 5 is always charged with a charging current equal to or higher than the minimum current.

Next, processing of the charging device in the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart for explaining processing of the charging device in the present embodiment. In the following, a process after a predetermined time “t _{1 / a} ” and a predetermined voltage “V ₁ ” are stored in the internal memory of the control unit 7 by the administrator of the charging device will be described with reference to FIG. .

  As shown in FIG. 4, when the control unit 7 of the charging device in the present embodiment receives an instruction to start operating the charging device from the administrator (Yes in Step S101), the control unit 7 controls the switch 6 to be turned off (Step S102). ). In addition, the control part 7 starts the measurement of the voltage of the parallel circuit 4 from the time of receiving the operation start instruction of the charging device from the administrator.

Then, the control unit 7 determines whether the voltage of the parallel circuit 4 is "V _1" or more (step S103).

Here, when the voltage of the parallel circuit 4 is less than “V ₁ ” (No at Step S <b> 103), the control unit 7 continuously executes the comparison determination between the voltage of the parallel circuit 4 and “V ₁ ”.

On the other hand, when the voltage of the parallel circuit 4 is “V ₁ ” or higher (Yes at Step S103), the control unit 7 controls the switch 6 to be turned on (Step S104).

After that, the control unit 7 determines whether or not a predetermined time “t _{1 / a} ” that is _a charging time has elapsed since the switch 6 was turned on (step S105).

Here, when “t _{1 / a} ” has not elapsed (No at Step S105), the control unit 7 continues to make a comparison between “t _{1 / a} ” and the elapsed time since the switch 6 is turned on. And run.

On the other hand, when “t _{1 / a} ” has elapsed (Yes at Step S105), the control unit 7 returns to Step S102 and performs control so that the switch 6 is turned OFF, and thereafter, the processing after Step S103 is continued. And execute.

As described above, in the present embodiment, the control unit 7 turns on the switch 6 when the “predetermined time” that is longer than the charging time “T _d ” required for charging the assembled battery 5 is reached. Thus, a voltage that is equal to or higher than the minimum current value “I _d ” required for charging the assembled battery 5 until the value of the charging current flowing into the storage battery by discharging from the capacitor 3 elapses for the “predetermined time”. The value “predetermined voltage” is stored in the internal memory. And the control part 7 is discharged so that the electric charge accumulate | stored in the capacitor | condenser 3 may be discharged and the assembled battery 5 may be charged, when the voltage of the capacitor | condenser 3 which accumulated the output electric power of the solar cell 1 becomes a predetermined voltage. The switch 6 is controlled to be turned on, and the switch is turned off so that the output power from the solar cell 1 is charged into the capacitor 3 when a predetermined time has elapsed from the time when the voltage of the capacitor 3 becomes a predetermined voltage. Control to switch to.

  Therefore, even when the amount of solar radiation is small, the charging current required for charging can be secured for the time required for charging. Therefore, as described above, the deterioration of the assembled battery 5 due to the minute charging current is prevented and charging is performed efficiently. Is possible.

  In addition, the capacitor 3 and the assembled battery 5 to be incorporated into the charging device are selected so as to satisfy the above expressions (10) and (11), or based on the characteristics of the capacitor 3 and the assembled battery 5 incorporated into the charging device. Thus, the manager of the charging device can easily operate a solar cell system that efficiently charges the battery pack 5 by preventing deterioration of the assembled battery 5 due to a minute charging current. It becomes possible.

  In addition, although the present Example demonstrated the case where the storage battery which comprises the assembled battery 5 is a nickel hydride storage battery, this invention is not limited to this, The storage battery which comprises the assembled battery 5 is, for example, The case where it comprises with another kind of storage batteries, such as a lead storage battery, a nickel cadmium storage battery, and a lithium ion storage battery, may be sufficient.

  If the capacitor 3 is a storage element that satisfies the relationship of “Q = CV” between the storage amount “Q”, the storage capacity “C”, and the bipolar voltage “V”, such as a capacitor, It is possible to apply to the invention.

  As described above, the charging device and the charging method according to the present invention are useful when the output power from the solar battery is charged to the storage battery with a DC circuit, and in particular, prevents deterioration of the storage battery due to a minute charging current, Suitable for charging efficiently.

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Diode 3 Capacitor 4 Parallel circuit 5 Battery assembly 6 Switch 7 Control part 8 Voltage source 9 Internal resistance

Claims (6)

A charging device for charging output power from a solar battery to a storage battery with a DC circuit,
A capacitor connected in parallel with the solar cell;
A switch for switching charge and discharge of the capacitor;
When the voltage of the capacitor reaches a predetermined voltage, control is performed to switch the switch so that the charge accumulated in the capacitor is discharged and charged to the storage battery, and the voltage of the capacitor is the predetermined voltage. Control means for controlling the switch so that the output power from the solar cell is charged in the capacitor when a predetermined time has elapsed from
A charging device comprising: The predetermined time uses “a” which is a real number of 1 or more, “R” which is an internal resistance of the storage battery, and “C” which is a capacity of the capacitor, thereby charging current to the storage battery. Is represented by the mathematical expression on the left side of the following formula (1) as the time from immediately after the start of charging to 1 / a, and “T _d ” which is the charging time required for charging the storage battery, The charging device according to claim 1, wherein a relational expression represented by the following formula (1) is satisfied.

Wherein the predetermined voltage "V _1" is the minimum current value required for charging the storage battery and the "I _d", when the voltage of the storage battery and the "V _b" satisfy the relation represented by the following formula (2) The charging device according to claim 2.

In a DC circuit having a capacitor connected in parallel with a solar cell and a switch for switching charging and discharging of the capacitor, a charging method for charging the storage battery with output power from the solar cell,
When the voltage of the capacitor reaches a predetermined voltage, control is performed to switch the switch so that the charge accumulated in the capacitor is discharged and charged to the storage battery, and the voltage of the capacitor is the predetermined voltage. A charging method comprising a control step of controlling the switch so that the output power from the solar cell is charged in the capacitor when a predetermined time has elapsed from the time point. The predetermined time uses “a” which is a real number of 1 or more, “R” which is an internal resistance of the storage battery, and “C” which is a capacity of the capacitor, thereby charging current to the storage battery. Is represented by the mathematical expression on the left side of the following formula (3) as the time from immediately after the start of charging to 1 / a, and “T _d ” which is the charging time required for charging the storage battery, The charging method according to claim 4, wherein a relational expression of an inequality sign shown in the following formula (3) is satisfied.

The predetermined voltage “V ₁ ” satisfies the relational expression shown in the following formula (4) when the minimum current value required for charging the storage battery is “I _d ” and the voltage of the storage battery is “V _b ”. The charging method according to claim 5.

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