JP3488348B2 - DC power supply device combined with solar cell and control method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an existing DC power feeding system including a rectifying device for converting power of a commercial power source into DC power for the purpose of utilizing clean energy,
The present invention relates to a DC power supply device used together with a solar cell, which is installed so as to convert the DC power of the solar battery into a constant voltage for use by a switching power supply device, and a control method thereof.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a block circuit of a conventional DC power supply device that also uses a solar cell. 1 is a commercial power source, 2 is a rectifying device, 3 is a load device, 4 is a solar cell, 5 is a diode, 6 is a switching power supply circuit, which is a control circuit 7, DC /
It is composed of a DC converter 8, an output voltage detection circuit 9, and the like. Further, the control circuit 7 includes a reference voltage 10 and an error amplifier 1
1, a dead time reference voltage 12, a triangular wave generator 13, comparators 14 and 15, and a gate circuit 16. The DC / DC converter 8 includes a high-frequency transformer 17, a switching element 18 provided on the primary side thereof, diodes 19, 20, 21 provided on the secondary side, and a choke coil 2
2. A rectifying / smoothing circuit including a capacitor 23 and the like. The purpose of this conventional DC power supply device that also uses solar cells is to use an existing DC power supply system that receives AC power from the commercial power supply 1, converts AC into DC by the rectifier 2, and supplies power to the load device 3 ( In the existing system), in order to suppress the deterioration of the electric power situation due to the increase in the load electric power, the solar cell 4 is used to the maximum when the solar cell 4 can be used as clean energy and the solar cell 4 can generate electric power. Possibly to reduce the labor of the existing system. The diode 5 prevents the backflow from the switching power supply device 6 to the solar cell 4.

In FIG. 7, the rectifying device 2 is usually a constant voltage source. On the other hand, the power from the solar cell 4 is converted by the switching power supply device 6, and if the power generated by the solar cell 4 is sufficiently higher than the load power consumption, the control circuit 7
The internal constant voltage circuit operates as a constant voltage source. That is,
This constant voltage circuit includes an output voltage detection circuit 9 and a control circuit 7, and the voltage detected by the output voltage detection circuit 9
The error amplifier 1 calculates the voltage difference from the preset reference voltage 10.
The value amplified by 1 is compared, and the amplified value and the triangular wave from the triangular wave generator 13 are compared by the comparator 14 to generate a constant voltage control pulse (a) . Also, in consideration of the storage time of the switching element 18, the maximum ON time of the switching element 18
In order to limit the width , the dead time reference voltage 12 and the triangular wave from the triangular wave generator 13 are compared by the comparator 15, and the dead time pulse (b) is similarly generated. Gate circuit 16
Then, of the constant voltage control pulse (a) and the dead time pulse (b), the one having a narrow ON time width is selected and input to the switching element 18 of the DC / DC converter 8.

Usually, when two constant voltage sources are connected in parallel, the one with a higher set voltage supplies power to the load. Therefore, if the set voltage of the switching power supply device 6 is made higher than the set voltage of the rectifier 2 of the existing system shown in FIG. 7, power can be supplied from the switching power supply device 6,
It is possible to supply the power generated by the solar cell 4 to the load device 3. Generally, the rectifier 2 of the existing system described above
In designing when a DC power supply device such as a solar cell 4 is connected between the load device 3 and the load device 3 and used together, the maximum conversion capacity is determined so that the output side becomes the maximum rating at the lower limit of the input side rated voltage. It is common to design it. Therefore, the design when the input is the solar cell 4 is based on the above design,
When the input side rating is the voltage at the maximum power point according to the typical characteristics of the solar cell and the variation in the characteristics of the solar cell is taken into consideration, the DC power supply unit will output a constant voltage rated on the output side when the amount of solar radiation is small. However, since the input electric power is insufficient, the ON time width of the switching element 18 becomes the maximum state limited by the dead time reference voltage 12. That is, O
It becomes an uncontrolled state with a fixed N time width .

[0005]

FIG. 8 is a general voltage-current and voltage-power characteristic diagram of the solar cell 4. In the non-controlled state, according to the amount of solar radiation and temperature at that time,
It is stable at point A of the voltage-current characteristic (VPV-IPV) and point A'of the voltage-power characteristic (VPV-PPV). This A'point is
The problem that the generated power of the solar cell cannot be effectively used because the DC power supply device is deviated from the maximum power point B'depending on the amount of solar radiation and the temperature at that time by considering the variation when designing. There is. Even if the variation of solar cells is ignored and the power conversion capacity of the DC power supply is approximated to the typical characteristics due to the amount of solar radiation, it will be affected by temperature, the type of solar cell and the design characteristics of the manufacturer. Therefore, it becomes necessary to set operating conditions each time, which increases complexity. The temperature characteristic of the solar cell is expressed as a relative ratio of the maximum power Pm with reference to 25 ° C. as shown in FIG. 9, for example. As described above, in the conventional switching power supply device using the solar cell as an input, the DC power supply device operates in an uncontrolled state with a fixed ON time width , except when power is supplied within the power conversion capability of the DC power supply device. It was Therefore, if the solar cell is affected by the amount of solar radiation, temperature, characteristic differences between manufacturers, aging, etc. at the operating point in the uncontrolled state, it will not be the maximum power point of the solar cell and It was difficult to effectively use the power that can be generated.

[0006]

According to a first aspect of the present invention, there is provided a DC power supply device for use with a solar cell, wherein a DC power supplied from a commercial power supply is converted into DC power by a rectifying device and the DC power is supplied to a load device. In a power supply system, a DC / DC converter that converts DC power of a solar cell into a predetermined output voltage, and stabilize the output voltage of the DC / DC converter, and convert the DC / DC by a dead time reference voltage. Switchon
A solar cell provided so as to convert the DC power of the solar cell into a required constant voltage and supply it to the load device by a switching power supply circuit having a control circuit having a means for determining the ON time width of the switching element. In the combined use DC power supply device, an input power measuring unit that detects an input voltage and an input current from the solar cell to the DC / DC converting unit to obtain an input power, and an input power calculated by the input power measuring unit comparing means for comparing the temporary storing storage means as a digital value converted a / D, and the input power being temporarily stored and input power measured in the following by the input power measurement means, the comparison An arithmetic means for adding or subtracting a predetermined digital value to the digital value temporarily stored based on the comparison result of the means, and then D / A converting and outputting as a control voltage; And control means for the input power of the solar cell to control the output power so as to maximize by varying the ON time width before kissing switching element in the output voltage, before
If the specified voltage cannot be maintained and the dead
The switching element has the maximum O depending on the time reference voltage.
When the N time width is limited, the comparing means,
The said calculation means and said control means, by varying the ON time width of the switching element, the input power is obtained so as to control the output power so as to maximize.

A method for controlling a DC power supply device that also uses a solar cell according to the second invention of the present application is a DC power supply system that converts the power of a commercial power supply into DC power by a rectifier and supplies the DC power to a load device. And a DC / DC converter that converts the DC power of the solar cell into a predetermined output voltage, stabilizes the output voltage of the DC / DC converter, and switches the DC / DC converter by the dead time reference voltage. Elementary
A combined use of a solar cell installed so as to convert the DC power of the solar cell into a required constant voltage and supply it to the load device by a switching power supply circuit having a control circuit having means for determining the ON time width of the child. In the DC power supply of
Wherein detecting the input voltage and the input current from the solar battery to the DC / DC converter unit seeking input power, and stored at one and the digital value thus determined input power is converted A / D,
Next, the input power to be measured is compared with the temporarily stored input power, and if the comparison result shows that the input power is increased, a predetermined digital value is added to or subtracted from the digital value to decrease the input power. If there is, a predetermined digital value is subtracted from or added to the digital value, D / A converted and output as a control voltage, the ON time width of the switching element is varied by this control voltage, and this operation is repeated , Switching with the dead time reference voltage
When the element is in the state of being limited to the maximum ON time width,
The input power of the solar cell is controlled to be maximum.

[0008]

1 is a block circuit diagram of an embodiment of a DC power supply device for use with a solar cell of the present invention.
Is an input voltage detection circuit, 32 is an input current detection circuit, 33 is a multiplier, 34 is an A / D converter, 35 is a microcomputer (CPU), 36 is RAM, 37 is RO M, and 38 is a D / A converter . , 39 is a comparator. The same parts as those in the block circuit diagram of the DC power supply device combined with the solar cell shown in FIG. 7 are denoted by the same symbols. Next, the operation will be described. The input power input from the solar cell 4 to the DC / DC converter 8 is detected by the input voltage detection circuit 31 and the input current detection circuit 32, and the detected levels are multiplied by the multiplier 3
The input power is obtained by multiplying by 3 and is sequentially converted into digital values by the A / D converter 34. The converted digital value is temporarily stored in the RAM 36 and is compared with the digital value of the input power which is also similarly converted and temporarily stored in the RAM 36, and the D / D is increased in the increasing direction.
The output voltage of the A converter 38 is changed each time. This operation is performed by operating the microcomputer 35 by the program written in the ROM 37.

The output voltage of the D / A converter 38 described above is
The triangular wave from the triangular wave generator 13 is compared with the comparator 39 to generate a power control pulse (c). Gate circuit 16
Then, as described in the conventional example of FIG. 7, a constant voltage control pulse (a) and a dead time pulse (b), and a pulse with a narrow ON time width of this power control pulse (c) are selected. / Inputted to the switching element 18 of the DC converter 8. Therefore, for example, when the amount of solar radiation decreases and the switching element 18 is driven by the dead time pulse (b) (uncontrolled state), the output power of the so-called solar cell 4 is not maximized, The maximum power of the solar cell 4 is generated by detecting the input power of the solar cell 4 with the multiplier 33 and generating the power control pulse (c) in the direction of increasing the input power while repeating the contents of the program of the ROM 37. It is to follow a point.

FIG. 2 (a) shows a flow chart of the program of the ROM 37 for making the maximum power point of the solar cell 4 follow.
It shows in (b). FIG. 2 (a) defines a cycle for performing tracking of the maximum power point of the solar cell 4, and increases the power operation amount S (n) during tracking and increases the power operation amount S (n-1) +1. Alternatively, it is a flowchart for determining the direction of the initial state of decrease S (n-1) -1. The tracking cycle (interruption cycle) is usually several tens to several hundreds of ms. 2 (b) is
The amount of electric power W (n) (digital value converted by A / D conversion) detected by the multiplier 33 is detected last time by the increase / decrease of the amount of electric power operation S (n) in the basic flowchart of FIG. If the power amount W (n) is increased, the power amount W (n-1) is maintained in the operation amount direction (increase or decrease) of the power operation amount S (n), and the power amount W (n If n) is decreasing, the operation amount direction of the power operation amount S (n) is reversed. This operation is repeated, but in this process, the power operation amount S (n) is the limit of the operation amount (maximum operation amount S (n) (max) or minimum operation amount S (n)).
Even if (n) (min) is exceeded, the operation amount direction is reversed.

FIG. 3 shows the voltage V according to the amount of solar radiation of the solar cell 4.
It shows the characteristics of PV and power PPV, and the power conversion capability characteristics of the power PC of the DC power supply device with respect to the voltage VPV of the solar cell 4. That is, by directly controlling the ON time width of the DC power supply, the power of the solar cell moves from A to B when the amount of solar radiation is large, and from A'to B'when the amount of solar radiation is small, and the maximum power of the solar cell is increased. Can be operated in points. FIG. 4 is a characteristic diagram of the irradiance on the solar cell 4 and its generated power. Control by the conventional switching power supply device shown in FIG. 7 and control by the switching power supply device of the present invention shown in FIG. 6 is a comparison of the generated power with and without the maximum power tracking control. As is apparent from the comparison data, the present invention makes it possible to improve the generated electric power by several% as compared with the conventional one.

[0012]

FIG. 5 is a block circuit diagram of another embodiment of a DC power supply device for use with solar cells according to the present invention. The difference from the embodiment of FIG. 1 is that the voltage value of the dead time reference voltage 12 is changed by the output voltage operation of the D / A converter 38 and output to the comparator 15 via the electronic potentiometer 40. is there. That is, the output voltage of the D / A converter 38 is not directly compared with the triangular wave from the triangular wave generator 13, but the output voltage of the D / A converter 38 changes the voltage value of the dead time reference voltage 12 in the upward direction. Then, a control pulse corresponding to the power control pulse (c) for outputting the maximum amount of electric power, which has an ON time width narrower than that of the dead time pulse (b), is generated, and the DC / DC converter 8 is supplied via the gate circuit 16. Is input to the switching element 18. Figure 6
In the block circuit diagram of the other embodiment of the DC power supply device used together with the solar cell of the present invention, an output current detection circuit 41 is provided on the output side of the DC / DC conversion unit 8 so that the output current is maximized. / D converter 34, CPU 35, RAM 36,
ROM 37, D / A converter 38, etc. Solar cell 4
The maximum output power of is tracked.

[0013]

EFFECTS OF THE INVENTION The solar cell is affected by the amount of solar radiation, the temperature, the characteristic difference between manufacturers, the secular change, etc., and the output power is controlled by the dead time pulse (b), so that the maximum power output cannot be obtained. By trying to track the maximum power point at that time, it is possible to maximize the amount of power generated by the solar cell, which can be effectively used. Further, the solar cell characteristics of the solar cell manufacturer are not affected by the difference, so that the versatility is improved.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of a DC power supply device used together with a solar cell according to the present invention.

FIG. 2 is a flowchart for tracking the maximum power point of the solar cell according to the present invention.

FIG. 3 is a voltage characteristic diagram of a solar cell and a power characteristic diagram of a solar cell voltage and a DC power supply device.

FIG. 4 is a comparison diagram of generated power characteristics of the DC power supply device of the conventional example and the DC power supply device of the present invention.

FIG. 5 is a block circuit diagram of another embodiment of the DC power supply device used together with a solar cell of the present invention.

FIG. 6 is a block circuit diagram of another embodiment of the DC power supply device used together with the solar cell of the present invention.

FIG. 7 is a block diagram showing an embodiment of a conventional switching power supply control system.

FIG. 8 is a characteristic diagram of voltage and current, and voltage and power of a solar cell.

FIG. 9 is a characteristic diagram of relative output with respect to temperature of a solar cell.

[Explanation of symbols]

1 Commercial power supply 2 rectifier 3 load device 4 solar cells 5,19,20,21 Diode 6 Switching power supply circuit 7 control circuit 8 DC / DC converter 9 Output voltage detection circuit 10 Reference voltage 11 Error amplifier 12 dead time reference voltage 13 Triangle wave generator 14, 15, 39 comparator 16 gate circuit 17 High frequency transformer 18 switching elements 22 choke coil 23 Capacitor 31 Input voltage detection circuit 32 Input current detection circuit 33 Multiplier 34 A / D converter 35 Microcomputer 36 RAM 37 ROM 38 D / A converter 40 electronic volume 41 Output current detection circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidaka ▼ Tetsuyi 1-34 Roppongi, Minato-ku, Tokyo Inside NTT Teficiaries Co., Ltd. (72) Masahiro Sasaki Minamimachi, Hanno City, Saitama Prefecture 10-13 No. 13 Shindengen Kogyo Co., Ltd. (56) Reference JP-A-6-259152 (JP, A) JP-A-6-165518 (JP, A) JP-A-61-277374 (JP, A) Actual Kaihei 5-70189 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 1 / 00,1 / 10 G05F 1/67 H02J 1/00 H02M 3/28 H02J 7/35

Claims (4)

(57) [Claims] 1. A DC / DC converter for converting the DC power of a solar cell into a predetermined output voltage in a DC power supply system for converting the power of a commercial power source into DC power by a rectifier and supplying the DC power to a load device. The DC converter and the output voltage of the DC / DC converter are stabilized, and the ON time of the switching element of the DC / DC converter is adjusted by the dead time reference voltage.
A switching power supply circuit having a control circuit having means for determining a width converts the direct current power of the solar cell into a desired constant voltage and supplies it to the load device together with the solar cell. In, the input power measuring means for detecting the input voltage and the input current from the solar cell to the DC / DC converter to obtain the input power, and the input power calculated by the input power measuring means
A temporary storing storage means as a digital value D conversion, and comparing means for comparing the input power being temporarily stored and input power measured in the following by the input power measuring means, the said comparison means After adding or subtracting a predetermined digital value to the digital value temporarily stored based on the comparison result, D
/ Calculating means for A conversion and output as the control voltage, when ON of the output voltage before kissing switching elements of said computing means
And a control means for controlling the output power so that the input power of the solar cell is maximized by varying the interval width , the constant voltage cannot be maintained, and
The switching element has the maximum
When the state of ON time width is limited, the comparison means, by said calculating means and said control means, by varying the ON time width of the switching element, the output power as the input power is maximum A DC power supply device used together with a solar cell, characterized in that it is controlled. 2. A DC / DC converter for converting the DC power of a solar cell into a predetermined output voltage in a DC power supply system for converting the power of a commercial power supply into DC power by a rectifier and supplying the DC power to a load device. The DC converter and the output voltage of the DC / DC converter are stabilized, and the ON time of the switching element of the DC / DC converter is adjusted by the dead time reference voltage.
A switching power supply circuit having a control circuit having means for determining a width converts the direct current power of the solar cell into a desired constant voltage and supplies it to the load device together with the solar cell. In output current detection means for detecting the output current of the DC / DC converter, and the output current detected by the output current detection means is A / D
A temporary storing storage means as a digital value converted, and comparing means for comparing the output current being temporarily stored and output current detected in the following by the output current detecting means, comparison of the comparison means After adding or subtracting a predetermined digital value to the digital value temporarily stored based on the result, D
/ Calculating means for A conversion and output as the control voltage, when ON of the output voltage before kissing switching elements of said computing means
And a control means for controlling the output power so that the output current of the solar cell is maximized by varying the interval width , the constant voltage cannot be maintained, and
The switching element has the maximum
When the state of ON time width is limited, the comparison means, by said calculating means and said control means, by varying the ON time width of the switching element, the output power so that the output current is maximized A DC power supply device used together with a solar cell, characterized in that it is controlled. 3. A DC / DC converter for converting the DC power of a solar cell into a predetermined output voltage in a DC power supply system for converting the power of a commercial power supply into DC power by a rectifier and supplying the DC power to a load device. The DC converter and the output voltage of the DC / DC converter are stabilized, and the ON time of the switching element of the DC / DC converter is adjusted by the dead time reference voltage.
A switching power supply circuit having a control circuit having means for determining a width converts the direct current power of the solar cell into a desired constant voltage and supplies it to the load device together with the solar cell. In, the input voltage and the input current from the solar cell to the DC / DC conversion unit are detected to obtain the input power, the obtained input power is A / D converted, and temporarily stored as a digital value. The measured input power is compared with the temporarily stored input power, and if the comparison result is an increase in the input power, a predetermined digital value is added to or subtracted from the digital value, and if the input power is decreased. It said predetermined digital value from the digital value subtraction or addition was after D / a converted and output as a control voltage, and varies the ON time width before kissing switching element by the control voltage, this By repeating the operation, the dead time reference
The switching element has a maximum ON time width depending on the voltage.
When Restricted state, the control method of a solar cell combination of the DC power supply device, characterized in that the input power of the solar cell was so that Gyosu braking so as to maximize. 4. A DC / DC converter for converting the DC power of a solar cell into a predetermined output voltage in a DC power supply system for converting the power of a commercial power source into DC power by a rectifying device and supplying the DC power to a load device. The DC converter and the output voltage of the DC / DC converter are stabilized, and the ON time of the switching element of the DC / DC converter is adjusted by the dead time reference voltage.
A switching power supply circuit provided with a control circuit having a means for determining the width converts the direct current power of the solar cell into a required constant voltage and supplies it to the load device. In a DC power supply device that also uses a battery, the output current of the DC / DC converter is detected and
/ D conversion is performed to temporarily store as a digital value, then the detected output current is compared with the temporarily stored output current, and if the comparison result is an increase in output current, a predetermined value is set to the digital value. and adding or subtracting the digital value, a predetermined digital value from said digital value if the output current decrease subtraction or addition was after D / a converted and output as a control voltage, this control voltage before kissing switching element By changing the ON time width and repeating this operation , the dead time reference
The switching element has a maximum ON time width depending on the voltage.
A method for controlling a DC power supply device used together with a solar cell, wherein the output current of the solar cell is controlled to be maximum when in a limited state .