JP6544247B2 - Charging device, charging device control program and method thereof - Google Patents

Description

  The present invention relates to a charging device, a charging device control program, and a method for the same.

  There is known a charging device which supplies power generated by a solar cell to a charging unit without passing through a diode (see, for example, Patent Document 1). In one example, the charging device adjusts the switching frequency of the switch connected to the capacitor that charges the power generated by the solar cell, equalizes the reference voltage and the terminal voltage of the solar cell, and maximizes the solar cell efficiency. Control the voltage of the solar cell to the operating voltage. By controlling the voltage of the solar cell to match the reference voltage to the voltage that operates at maximum efficiency, the charging device maximizes the solar cell regardless of the intensity of light received by the solar cell and the variation of the temperature of the solar cell. It is possible to operate at efficiency.

JP 2005-45886 A

  However, since the voltage that operates the solar cell at maximum efficiency is based on various conditions such as the intensity of light received by the solar cell, the temperature of the solar cell, and manufacturing variations of the solar cell, the solar cell operates at maximum efficiency It is not easy to match the voltage to be generated with the reference voltage.

  In one embodiment, it is an object of the present invention to provide a charging device capable of operating the power generation device at maximum efficiency regardless of changes in operating conditions even when the voltage for operating the power generation device at maximum efficiency is unknown.

  In one aspect, the charging device includes an input voltage detection unit, a switched capacitor, a charging unit, and a control unit. The input voltage detection unit detects an input voltage input from the power generation device. The switched capacitor has a capacitor, a first terminal connected to one end of the capacitor to one end of the input voltage detection unit, and a switch connected alternately to the second terminal. The charging unit has one end connected to the second terminal. The control unit includes an input voltage acquisition unit, a switching frequency adjustment unit, and a switching signal output unit, and controls the switch. The input voltage acquisition unit acquires the input voltage, and the switching frequency adjustment unit maximizes the calculated value calculated by multiplying the switching frequency at which the switch is switched between the first terminal and the second terminal and the input voltage. Adjust the switching frequency as follows. The switching signal output unit outputs a switching signal indicating switching between the first terminal and the second terminal at the switching frequency to the switch.

  In one embodiment, it is possible to provide a charging device capable of operating the power generation device at maximum efficiency regardless of changes in operating conditions, even when the voltage that causes the power generation device to operate at maximum efficiency is unknown.

1 is a block diagram of a power generation system including a charging device according to a first embodiment. It is a flowchart of the charge process by the charging device shown in FIG. (A) is a figure which shows the switched capacitor shown in FIG. 1 of a charge condition, FIG.3 (b) is a figure which shows the switched capacitor shown in FIG. 1 of a discharge condition. It is a figure which shows the relationship between the switching frequency of the charge process by the charging device shown in FIG. 1, and the electric power of the solar cell shown in FIG. (A) is a SPICE net list for the operation verification of the charging device shown in FIG. 1, (b) is a figure which shows a time-dependent change of the charging current obtained by SPICE simulation by the SPICE net list shown to (a). is there. It is a block diagram of the electric power generation system containing the charging device concerning a 2nd embodiment. It is a flowchart of the charge process by the charging device shown in FIG. It is a block diagram of the electric power generation system containing the charging device concerning a 3rd embodiment.

  Hereinafter, a charging device, a charging device control program, and a method therefor according to the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to those embodiments.

(Overview of Charging Device According to Embodiment)
The charging device according to the embodiment charges the power input from the power generation device to the charging unit via the switched capacitor. By adjusting the switching frequency of the switched capacitor by multiplying the input voltage by the switching frequency so as to maximize the calculated value, even when the voltage for operating the power generation apparatus at maximum efficiency is unknown, the power generation apparatus Can be charged to operate at maximum efficiency.

(Configuration and Function of Power Generation System Including Charging Device According to First Embodiment)
FIG. 1 is a block diagram of a power generation system including the charging device according to the first embodiment.

  The power generation system 100 includes a charging device 1, a solar cell 101, and a load 102. The solar cell 101 is a power generation device that converts received light into electric power and outputs the electric power to the charging device 1. The charging device 1 charges the power input from the solar cell 101 and outputs the power to the load 102. The load 102 performs predetermined processing using the power input from the charging device 1. The charging device 1 includes an input voltage detection unit 10, a switched capacitor 11, a low pass filter 12, a charging unit 13, a storage unit 19, and a control unit 20.

  The input voltage detection unit 10 has one end connected to the positive electrode of the solar cell 101 and the other end grounded together with the negative electrode of the solar cell 101 to detect and detect the input voltage of the power input from the solar cell 101 to the charging device 1 The input voltage is output to the control unit 20. The input voltage detection unit 10 includes a voltmeter in one example.

  The switched capacitor 11 includes a capacitor 14, a switch 15, a first terminal 16 and a second terminal 17. One end of the capacitor 14 is connected to the switch 15, and the other end is grounded. The switch 15 alternately connects one end of the capacitor 14 to the first terminal 16 and the second terminal 17 in accordance with the switching signal input from the control unit 20. The switch 15 includes a pair of MOSFETs. The respective gates of the pair of MOSFETs are connected to the control unit 20, and the respective sources of the pair of MOSFETs are connected to one end of the capacitor 14. One drain of the pair of MOSFETs is connected to the first terminal 16, and the other drain of the pair of MOSFETs is connected to the second terminal 17. The first terminal 16 is connected to the positive electrode of the solar cell 101 and one end of the input voltage detection unit 10. The second terminal 17 is connected to one end of the low pass filter 12.

  The switched capacitor 11 charges the capacitor 14 with the power input from the solar cell 101 when the switch 15 connects the capacitor 14 and the first terminal 16. Further, when the switch 15 connects the capacitor 14 and the second terminal 17, the switched capacitor 11 outputs the charged power to the charging unit 13 and the load 102 via the low pass filter 12.

  One end of the low-pass filter 12 is connected to the second terminal 17, and the other end is input to the charging unit 13 and the load 102. The power input from the capacitor 14 is smoothed and output to the charging unit 13 and the load 102.

  The charging unit 13 is a secondary battery that charges the switched capacitor 11 and the low pass filter 12 from the solar cell 101. In one example, the charging unit 13 includes a lead storage battery.

  The storage unit 19 includes, for example, a semiconductor memory, and stores a driver program, an operating system program, an application program, data, and the like used for arithmetic processing by the control unit 20. In addition, the storage unit 19 stores, as an application program, a charging program or the like that controls the switch 15 to charge the voltage input from the solar cell 101. The computer program may be installed in the storage unit 19 from a computer-readable portable recording medium, such as a CD-ROM or a DVD-ROM, using a known setup program or the like.

  The control unit 20 includes one or more processors and their peripheral circuits. The control unit 20 executes various arithmetic processing, and is, for example, a CPU (Central Processing Unit). The control unit 20 controls the operation of the switch 15 so that various kinds of arithmetic processing are performed in an appropriate procedure in accordance with a program or the like stored in the storage unit 19. The control unit 20 executes a process based on a program (a driver program, an operating system program, an application program, etc.) stored in the storage unit 19. Further, the control unit 20 can execute a plurality of programs (application programs and the like) in parallel.

  The control unit 20 includes an input voltage acquisition unit 21, an input voltage determination unit 22, a switching frequency adjustment unit 23, and a switching signal output unit 24. The switching frequency adjustment unit 23 includes an operation unit 31, a calculation value determination unit 32, and a frequency adjustment unit 33. These units included in the control unit 20 are functional modules implemented by a program executed on a processor included in the control unit 20. Alternatively, these units included in the control unit 20 may be implemented in the charging device 1 as independent integrated circuits, microprocessors, or firmware.

(Operation of the charging device according to the first embodiment)
FIG. 2 is a flowchart of the charging process by the charging device 1. The charging process is mainly performed by the control unit 20 in cooperation with each element of the charging device 1 based on a program stored in advance in the storage unit 19.

First, the input voltage acquisition unit 21 acquires an input voltage V _in which the input voltage detection unit 10 is input from the solar battery 101 detected from the input voltage detection unit 10 (S101). Next, the input voltage determination unit 22 determines whether the input voltage V _in acquired by the input voltage detection unit 10 is larger than a predetermined threshold voltage V _th (S102). Since it is determined that the input voltage V _in is equal to or lower than the threshold voltage V _th (S102) because the power generated by the solar cell 101 at night or the like is small (S102), the process returns to S101. The processes of S101 to S102 are repeated until it is determined that the input voltage V _in is larger than the threshold voltage V _th (S102).

When it is determined that the input voltage V _in is larger than the threshold voltage V _th (S102), the arithmetic unit 31 sets the switching frequency to the initial frequency f ₀ (S103). Next, the calculation unit 31 multiplies the input voltage V _in by the switching frequency f set to the initial frequency f ₀ to calculate the calculation value M ₀ (S104). The calculated operation value M ₀ is stored in the storage unit 19.

Then, the frequency adjustment unit 33 adds the fluctuation frequency Δf to the switching frequency f is set to an initial frequency f ₀ (S105). Next, the input voltage acquisition unit 21 acquires the input voltage V _in input from the solar cell 101 from the input voltage detection unit 10 (S106). Then, the arithmetic unit 31 multiplies the calculated switching frequency f in is the processing of the input voltage V _in and S105 obtained in the processing in S106, and calculates the calculated value M (S107). The calculated operation value M is stored in the storage unit 19.

  Next, the calculation value determination unit 32 determines whether the calculation value M increases according to the change of the switching frequency f (S108). That is, the calculation value determination unit 32

Execute the judgment process of Here, M _{(t + 1)} is the calculated value M calculated in the process of S107, and M _(t) is the calculated value M ₀ calculated in the process of S104. Further, f _{(t + 1)} is the switching frequency f calculated in the process of S105, and f _(t) is the initial frequency f ₀ .

  FIG. 3A is a view showing the switched capacitor 11 in a charged state, and FIG. 3B is a view showing the switched capacitor 11 in a discharged state.

  The capacitance value C [F] of the capacitor 14 and the charge quantity q [C] per cycle from the input voltage V are

  It is indicated by. The charge amount Q [C] per second is obtained from the charge amount q [C] per cycle and the switching frequency f [Hz].

  It is indicated by. Since the current I [A] is equivalent to the charge quantity Q [C] per second,

  As indicated by

The variation of the magnitude of the operation value M is substantially equal to the variation of the power P (= IV _in ) input from the solar cell 101.

When it is determined that the calculated value M is increasing according to the change of the switching frequency f (S108), the frequency adjustment unit 33 adds the fluctuation frequency Δf to the switching frequency f calculated in S105, and the switching frequency f is further increased (S109). Further, if it is determined that the calculated value M is not increased according to the change of the switching frequency f (S108), the frequency adjustment unit 33 subtracts the fluctuation frequency Δf from the switching frequency f calculated in S105, The switching frequency f is decreased (S110). Next, the switching signal output unit 24 outputs, to the switch 15, a switching signal indicating switching between the first terminal 16 and the second terminal 17 at the switching frequency f (S111). Next, the input voltage determination unit 22 determines whether the input voltage V _in acquired by the input voltage detection unit 10 is larger than a predetermined threshold voltage V _th (S112).

Thereafter, the processes of S106 to S112 are repeated until it is determined that the input voltage V _in acquired by the input voltage detection unit 10 is equal to or less than the predetermined threshold voltage V _th (S112). Every time the processing of S106 to S112 is executed, a switch signal indicating switching between the first terminal 16 and the second terminal 17 with the switching frequency f adjusted according to the determination result in S108 is supplied to the switch 15 It is output.

  FIG. 4 is a diagram showing the relationship between the switching frequency f of the charging process by the charging device 1 and the power P of the solar cell 101. As shown in FIG. In FIG. 4, the horizontal axis indicates the switching frequency f, and the vertical axis indicates the power P of the solar cell 101.

Since the power P ₁ corresponding to the calculated value M when the initial frequency f ₀ f ₁ obtained by adding the fluctuation frequency Δf in is greater than the power P ₀ corresponding to the calculated value M when the initial frequency f _0, a frequency adjustment The unit 33 adds the fluctuation frequency Δf to the switching frequency f to make the switching frequency f ₂ . Then, power P ₂ corresponding to the calculated value M at the time of f ₂ is larger than the power P ₁ corresponding to the calculated value M when the switching frequency f _1, the frequency adjusting unit 33, the variation in the switching frequency f the switching frequency f to f ₃ by adding the frequency Δf. Then, power P ₃ corresponding to the calculated value M when the f _3, so is the power P ₂ below corresponding to the calculated value M when the switching frequency f _2, the frequency adjustment unit 33 varies the switching frequency f The switching frequency f is set to f ₂ by subtracting the frequency Δf. Then, power P ₂ corresponding to the calculated value M at the time of f ₂ is larger than the power P ₃ corresponding to the calculated value M when the switching frequency f _3, the frequency adjusting unit 33 varies the frequency from the switching frequency f The switching frequency f is set to f ₁ by subtracting Δf. Then, power P ₁ corresponding to the calculated value M when the f _1, so is the power P ₂ below corresponding to the calculated value M when the switching frequency f _2, the frequency adjustment unit 33 varies the switching frequency f The switching frequency f is set to f ₂ by adding the frequency Δf.

Switching frequency f is from f ₂ to f _3, the power P of the solar cell 101 is reduced from P ₂ to P _3, the decreasing direction, i.e. varying in the opposite direction of f ₂ the switching frequency f. On the other hand, the switching frequency f is from f ₂ to f _1, the power P of the solar cell 101 is reduced from P ₂ to P ₁ in the direction increasing the switching frequency f, i.e. varying in the opposite direction of f _2.

The frequency adjustment unit 33 changes the switching frequency f in the same direction when it is determined that the calculated value M is increasing according to the change of the switching frequency f. Further, the frequency adjustment unit 33 changes the switching frequency f in the opposite direction when it is determined that the calculated value M does not increase according to the change of the switching frequency f. By changing the switching frequency f in the opposite direction when the frequency adjustment unit 33 determines that the calculation value M is not increased according to the change of the switching frequency f, the power switching frequency f is equal to the power of the solar cell 101. It is controlled between f ₁ and f _{3 in} the vicinity of the optimum operating point where P is maximum. By repeating the processes of S106 to S112, the charging apparatus 1 can switch the switch 15 at the switching frequency f near the optimum operating point at which the power P of the solar cell 101 is maximized.

Then, when it is determined that the input voltage V _in acquired by the input voltage detection unit 10 is less than or equal to the predetermined threshold voltage V _th (S112), the process ends.

  FIG. 5 (a) is a SPICE net list for operation verification of the charging device 1, and FIG. 5 (b) is a time-dependent change of the charging current obtained by SPICE simulation by the SPICE net list shown in FIG. 5 (a). FIG. In FIG. 5B, the horizontal axis indicates the elapsed time since the solar cell 101 starts power generation, and the vertical axis indicates the charging current input to the capacitor 14.

  In the charging device 1, when the charging current input to the capacitor 14 is large because the power input from the solar cell 101 is large, the magnitude of the fluctuation of the charging current decreases in a relatively early time. On the other hand, when the charging current input to the capacitor 14 is small because the power input from the solar cell 101 is small, the fluctuation of the charging current continues for a relatively long time, but the fluctuation of the charging current according to the passage of time The width is smaller.

(Configuration and Function of Power Generation System Including Charging Device According to Second Embodiment)
FIG. 6 is a block diagram of a power generation system including the charging device according to the second embodiment.

  The power generation system 200 differs from the power generation system 100 in that the charging device 2 in which the control unit 40 is disposed instead of the control unit 20 is disposed instead of the charging device 1. The control unit 40 differs from the control unit 20 in having a switching frequency adjustment unit 43 having an operation unit 41 and an operation value determination unit 42 instead of the operation unit 31 and the operation value determination unit 32 instead of the switching frequency adjustment unit 23. Do. The configurations and functions of the components of the power generation system 200 other than the calculation unit 41 and the calculation value determination unit 42 are the same as the configurations and functions of the components of the power generation system 100 to which the same reference numerals are given. Do.

(Operation of Charging Device According to Second Embodiment)
FIG. 7 is a flowchart of the charging process by the charging device 2. The charging process is mainly performed by the control unit 40 in cooperation with each element of the charging device 2 based on a program stored in advance in the storage unit 19.

Since the processes of S201 to S203 are the same as the processes of S101 to S103, detailed description will be omitted here. Then, the arithmetic unit 41 multiplies the switching frequency f is set to a square and initial frequency f ₀ of the input voltage V _in, and calculates the calculated value S ₀ (S204). The calculated operation value S ₀ is stored in the storage unit 19. Then, the frequency adjustment unit 33 adds the fluctuation frequency Δf to the switching frequency f is set to an initial frequency f ₀ (S205). Next, the input voltage acquisition unit 21 acquires the input voltage V _in input from the solar cell 101 from the input voltage detection unit 10 (S206). Next, the calculation unit 31 calculates a calculation value S by multiplying the square of the input voltage V _in acquired in the process of S106 and the switching frequency f calculated in the process of S105 (S207). The calculated operation value S is stored in the storage unit 19.

  Next, the calculation value determination unit 42 determines whether the calculation value M increases according to the change of the switching frequency f (S208). That is, the calculation value determination unit 42

Execute the judgment process of Here, S _{(t + 1)} is the calculated value S calculated in the process of S207, and S _(t) is the calculated value S ₀ calculated in the process of S204. Further, f _{(t + 1)} is the switching frequency f calculated in the process of S205, and f _(t) is the initial frequency f ₀ .

The power P input from the solar cell 101 is

  As indicated by

  The variation of the magnitude of the operation value S is proportional to the variation of the power P input from the solar cell 101. Since the processes of S209 to S212 are the same as the processes of S109 to S112, detailed description will be omitted here.

  The frequency adjustment unit 33 changes the switching frequency f in the same direction when it is determined that the calculated value S is increasing according to the change of the switching frequency f. Further, the frequency adjustment unit 33 changes the switching frequency f in the opposite direction when it is determined that the calculated value S does not increase according to the change of the switching frequency f. By changing the switching frequency f in the opposite direction when it is determined that the frequency adjustment unit 33 does not increase the calculated value S according to the change of the switching frequency f, the power switching frequency f is the power of the solar cell 101 It is controlled at a frequency near the optimum operating point at which P is maximum. By repeating the processing of S206 to S212, the charging apparatus 1 can switch the switch 15 at the switching frequency f near the optimum operating point at which the power P of the solar cell 101 is maximized.

(Configuration and Function of Power Generation System Including Charging Device According to Third Embodiment)
FIG. 8 is a block diagram of a power generation system including the charging device according to the third embodiment.

  The power generation system 300 differs from the power generation system 100 in that a charging device 3 having a DC-DC converter 18 is disposed instead of the charging device 1. The configurations and functions of the components of the power generation system 300 other than the DC-DC converter 18 are the same as the configurations and functions of the components of the power generation system 100 to which the same reference numerals are attached.

  The DC-DC converter 18 is disposed between the input voltage detection unit 10 and the switched capacitor 11, converts the voltage input from the solar cell 101 into a predetermined conversion voltage, and outputs the converted voltage to the switched capacitor 11.

  In the power generation system 300, since the DC-DC converter 18 outputs a predetermined conversion voltage to the switched capacitor 11, a constant voltage can be input to the switched capacitor 11 regardless of the fluctuation of the input voltage input from the solar cell 101. It is. In the power generation system 300, a constant voltage is input to the switched capacitor 11 regardless of the fluctuation of the input voltage input from the solar cell 101, so that the charge charged to the capacitor 14 per unit time can be made constant. it can.

(Operation effect of the charging device according to the embodiment)
Since the charging device according to the embodiment adjusts the switching frequency of the switched capacitor so that the calculated value calculated from the input voltage and the switching frequency is maximized, when the voltage for operating the power generation device at maximum efficiency is unknown However, the generator can be charged with a voltage that operates at maximum efficiency.

  In addition, since the charging device according to the embodiment can cut off the electrical connection between the solar cell 101 and the charging unit 13 by the switched capacitor 11, the diode for backflow prevention is used as the solar cell 101 and the charging unit 13. There is no need to place between them. Since the charging device according to the embodiment does not arrange the backflow preventing diode between the solar cell 101 and the charging unit 13, there is a possibility that a loss due to a voltage drop due to the forward voltage of the backflow preventing diode may occur. Absent.

  Further, in the charging device according to the embodiment, the solar cell 101 and the charging unit 13 are not shorted except when the pair of MOSFETs forming the switched capacitor 11 simultaneously cause a short circuit failure. In the charging device according to the embodiment, the solar cell 101 and the charging unit 13 are not shorted if the pair of MOSFETs forming the switched capacitor 11 do not have a short circuit failure at the same time. Therefore, the risk of overcharging the charging unit 13 is low.

  In addition, since the charging apparatus according to the embodiment adjusts the switching frequency f so that the solar cell 101 has the maximum efficiency without detecting the input current input from the solar cell 101, the current detection for detecting the input current Since the device can be omitted, the cost can be reduced.

  Further, in the charging device 3 according to the third embodiment, since the output current of the DC-DC converter 18 can be calculated from the switching frequency f, the current detection device for measuring the output current of the DC-DC converter 18 can be omitted. Cost can be achieved.

(Modification of the charging device according to the embodiment)
Although the power generation system 100 to 300 adopts the solar cell 101 as a power generation device, other power generation devices including an environmental power generation device such as a wind power generation device, a Seebeck temperature difference power generation device, or a geothermal power generation device may be adopted.

1 to 3 Charging Device 10 Input Voltage Detection Unit 11 Switched Capacitor 13 Charging Unit 20, 40 Control Unit 21 Input Voltage Acquisition Unit 22 Input Voltage Determination Unit 23, 43 Switching Frequency Adjustment Unit 24 Switching Signal Output Unit 31, 41 Calculation Unit 32 , 42 Calculated value determination unit 33 Frequency adjustment unit 101 Solar cell (power generation device)

Claims (7)

An input voltage detection unit that detects an input voltage input from the power generation device;
A switched capacitor having a capacitor, and a switch that alternately connects one end of the capacitor to one end of the input voltage detection unit and a second terminal to the second terminal;
A charging unit whose one end is connected to the second terminal;
A control unit that controls the switch, the control unit including:
An input voltage acquisition unit that acquires the input voltage;
Switching frequency adjustment unit for adjusting the switching frequency such that the operation value calculated by multiplying the switching voltage by which the switch is switched between the first terminal and the second terminal and the input voltage is maximized When,
A switching signal output unit that outputs a switching signal indicating switching between the first terminal and the second terminal at the switching frequency to the switch;
With a charging device. The switching frequency adjustment unit is
An arithmetic unit that generates the arithmetic value by multiplying the switching frequency by the input voltage;
A value determination unit that determines whether the calculated value increases according to a change in switching frequency;
When it is determined that the calculated value is increased according to the change of the switching frequency, it is determined that the changed frequency is changed in the same direction, and the calculated value is decreased according to the change of the switched frequency. A frequency adjustment unit that changes the switching frequency in the opposite direction when
The charging device according to claim 1, comprising:   The charging device according to claim 1, wherein the power generation device includes a solar cell.   The charging device according to any one of claims 1 to 3, wherein the operation value is calculated by multiplying the switching frequency and the input voltage.   The charging device according to any one of claims 1 to 3, wherein the operation value is calculated by multiplying the switching frequency by the square of the input voltage. An input voltage detection unit that detects an input voltage input from the power generation device;
A switched capacitor having a capacitor, and a switch that alternately connects one end of the capacitor to one end of the input voltage detection unit and a second terminal to the second terminal;
A charging unit whose one end is connected to the second terminal;
And a control unit that controls the switch.
Get the input voltage,
The switching frequency is adjusted so that the operation value calculated by multiplying the switching voltage by which the switch is switched between the first terminal and the second terminal, and the input voltage becomes maximum.
A switching signal indicating switching between the first terminal and the second terminal at the switching frequency is output to the switch.
Control method of the charging device including. An input voltage detection unit that detects an input voltage input from the power generation device;
A switched capacitor having a capacitor, and a switch that alternately connects one end of the capacitor to one end of the input voltage detection unit and a second terminal to the second terminal;
A charging unit whose one end is connected to the second terminal;
And a control unit that controls the switch.
Get the input voltage,
The switching frequency is adjusted so that the operation value calculated by multiplying the switching voltage by which the switch is switched between the first terminal and the second terminal, and the input voltage becomes maximum.
A switching signal indicating switching between the first terminal and the second terminal at the switching frequency is output to the switch.
A charging device control program that causes the control unit to execute a process.

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