JP3516101B2 - Solar power generator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar power generation device that uses a solar cell to generate electric power, and more specifically, in order to efficiently use solar energy, maximum power can always be obtained from the solar cell. The present invention relates to a solar power generation device including maximum power tracking control means (hereinafter, referred to as MPPT control means) for tracking and controlling a maximum power point.

[0002]

2. Description of the Related Art FIG. 10 shows, for example, JP-A-61-19772.
FIG. 1 is a block diagram showing a schematic configuration of a conventional solar power generation device including MPPT control means disclosed in Japanese Patent Laid-Open No.
FIG. 11 is a specific configuration diagram thereof. In these figures, 50 is a solar cell, 51 is a storage battery, 52 is a load, and 53.
Is a voltage commander, 54 is a control circuit, and 55 is a power converter.

The power converter 55 is composed of a step-down chopper having a structure as shown in FIG. 11, and the voltage commander 53 is provided with an input current Iin and a current to the step-down chopper 55 detected by a current sensor CT1. Piezoresistors R1 and R
Input power Pin obtained by multiplying the input voltage Vin to the step-down chopper 55 extracted from the intermediate point of 2 by the multiplier 56
Is input, and this is compared with a past voltage, and a predetermined voltage ΔV is applied in the direction in which the power increases, and a command Vref is output. The control circuit 54 includes a triangular wave generating circuit 57 and a comparator 58, and in accordance with the command Vref output from the voltage command device 53, the output current Iout from the step-down chopper 55 detected by the current sensor CT2 and the command described above. The rate corresponding to Vref is added to change the ON / OFF ratio of the switching transistor Tr in the step-down chopper 55, that is, the energization rate at every predetermined time interval so that the power change rate becomes zero, that is, Vin = It is controlled to become Vref. In FIG. 11, A is an amplifier having different gains, and D is a backflow prevention diode.

By the way, the solar cell has a low energy conversion efficiency, and its output characteristics largely vary depending on the amount of solar radiation, the temperature of the solar cell element, and the like. Incidentally, FIG. 12 shows the static characteristics (P-V characteristics) of the solar cell, and the portion marked with black dots in the figure is the maximum power point Pmax. The maximum power point fluctuates in the direction of arrow X in FIG. 12A, and the PV characteristics and the maximum power point are shown in FIG.
It changes in the arrow Y direction of (b).

Therefore, in the above-described conventional photovoltaic power generator, the predetermined operating voltage command Vref is determined by increasing or decreasing the predetermined voltage ΔV applied to the voltage command device 53 and increasing or decreasing the power change ΔP at that time. It was That is, as shown in FIG. 13, when the command Vref is increased by ΔV from time k−1 to time k, ΔP = P
If k-Pk-1> 0, Vref ← Vref + ΔV (> 0)
And Further, when ΔP <0 when the voltage is increased, Vref ← Vref−ΔV (> 0).
That is, the next command Vre is determined by the sign of ΔV and the sign of ΔP.
Decide whether to increase or decrease f. As a result, finally ΔP≈0
The operating point of the solar cell is set to near the maximum power.

[0006]

However, the MPPT control means of the above-mentioned conventional photovoltaic power generator measures the output power of the solar cell and controls the operating point of the solar cell so that the power change rate becomes zero. And the output characteristic (P-
Since the maximum power point is searched by moving the operating point by a certain amount in the direction of increasing power on the V characteristic), the voltage and power fluctuate near the maximum power point Pmax as shown by the solid line in FIG. Will move, and therefore
Not only is it not always possible to obtain the maximum electric power, but there is also the problem that in the steady state, power loss due to oscillation occurs and conversion efficiency (power generation efficiency) is reduced. In particular,
When the amount of solar radiation is large, the maximum power point Pmax of the PV characteristic
Since the slope in the vicinity is large, the power fluctuation is larger and the loss is larger.

Further, as shown by the dotted line in FIG. 14, it is possible to suppress the swing near the maximum power point Pmax by moving the operating point small, but in this case, the maximum power point is reached. It takes a long time until MPPT
Another problem occurs that the control responsiveness deteriorates.

The present invention has been made in view of the above-mentioned circumstances, and while maintaining the quick response until reaching the maximum power point, the power loss in the vicinity of the maximum power point is reduced to generate power in a steady state. It is an object of the present invention to provide a photovoltaic power generation device that can improve efficiency.

[0009]

In order to achieve the above object, the solar power generation device according to the invention of claim 1 is an operating voltage for generating maximum power based on voltage, current or power information of a solar cell. Or a command device for obtaining and commanding an operating current, and a correction device that determines the characteristic change of the solar cell based on the voltage, current or power information of the solar cell, and outputs correction information to the command device. e Bei a control device for controlling the power converter based on the output information from the command device and the correction device, the command device, the solar cell voltage or
Generates maximum power based on current change sign and power change
The operating voltage or operating current
In addition, the above-mentioned correction device
The power used in the above command device based on the sign of
It is characterized in that it outputs the correction value of the change value .
It

[0010]

Further, the correction value in the correction device is calculated by using a fuzzy operation based on the voltage or current change of the solar cell, as in claim 2 .
Further, in the above fuzzy operation, as claimed in claim 3, the membership form capable of changing parameters of the function, it is desirable that the change by the command information from the calendar information or external to internal.

[0012]

According to the invention of claim 1, the command device searches for the maximum power point on the PV characteristic of the solar cell based on the voltage, current or power information of the solar cell and commands it. On the other hand, the correction device determines changes in solar cell characteristics such as the amount of solar radiation and element temperature, and outputs correction information.
By correcting the command from the command device based on this correction information, the command change width in the vicinity of the maximum power point is suppressed to the minimum regardless of the change in the characteristics of the solar cell such as the amount of solar radiation and the element temperature. As a result, it is possible to suppress swinging in the vicinity of the maximum power point and reduce power loss while maintaining responsiveness until reaching the maximum power point.

[0013] Also, the upper SL command device and correction device are both if and to output the command and the correction value on the basis of the code and power variation of the voltage or current change of the solar cell, solar radiation Ya Regardless of whether the element temperature or the like fluctuates in either direction of increase or decrease, it is possible to suppress fluctuations near the maximum power point and reduce power loss as described above.

Further, the correction value in the correction device is
As in claim 2, the calculation is performed by using a fuzzy operation based on the voltage change or the current change of the solar cell, and in the fuzzy operation, the form of the membership function is defined as in claim 3. If the changeable parameter is changed according to the built-in calendar information or the command information from the outside, the correction is performed based on the control law that is determined according to the amount of change in the PV characteristics of the solar cell. Since the value is calculated, it is possible to smoothly follow the maximum power point under the sensitivity adapted to the magnitude of change.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a concrete example of a voltage commander 1 which is a main part of a photovoltaic power generator according to an embodiment of the present invention and a power value corrector 2 which outputs correction information for correcting the power value in the voltage commander 1. FIG. 12 is a block configuration diagram showing only the configuration, and a solar cell 50, a storage battery 51, a load 52, a voltage conversion device (step-down chopper) 55, a control circuit 57, and the like, which are components not shown here, are shown in FIG. 11. The same description is omitted, and the same reference numerals are used in the following description.

In FIG. 1, the voltage commander 1 includes a difference calculation section 3 for calculating a change amount ΔVin of the input voltage Vin from the solar cell 50, and a code determination unit 4 for determining a code sgn of the change amount ΔVin. , A multiplication unit 5 for obtaining an input voltage Pin from the input voltage Vin and the input current Iin, a difference calculation unit 6 for calculating a change amount ΔPin of the input power Pin, a change amount ΔPin of the input power Pin and the power value correction A multiplier 7 for multiplying the difference ΔP of the correction value ΔPr output from the device 2 by the code sgn of the variation ΔVin output from the code determiner 4, and a value K output from the multiplier 7 Operation voltage command Vref by the gain adjusted value ΔVref
And a calculator 8 that calculates and outputs

Further, the power value corrector 2 uses the input voltage change ΔVin output from the difference calculator 3 and the input power change ΔPin output from the difference calculator 6 in the voltage commander 1. Change in input power used ΔP
It is configured to calculate the correction value ΔPr of in.

Next, the operation of the main part of the solar power generation device having the above structure will be described. First, in the voltage commander 1, when the input voltage Vin from the solar cell 50 deviates greatly from the optimum operating voltage Vop which is the maximum power point of the PV characteristic, as shown in FIG. The amount of change ΔPin is also large. Therefore, the value of ΔVref becomes a large value such as ΔVref = sgn (ΔVin) · ΔPin (1), and the operating voltage command Vref largely moves. In addition, the input voltage Vin is the optimum operating voltage Vop
As the change ΔPin of the input power Pin becomes smaller as the value approaches, the value of ΔVr
The value of ef becomes small, and the movement of the operating voltage command Vref is small. Incidentally, where reference numeral sgn outputted from top Kifu No. discriminating unit 4 is to determine the sign of .DELTA.Vref.
When ΔPin is 0, ΔVref → 0, V
ref → Vop, and maximum power is obtained.

[0019] On the other hand, the above-mentioned power value correction unit 2, try to assume the operation when the amount of solar radiation is changed by such as shadow caused Ri by the weather changes and the building. As described above, the PV characteristic changes in the direction of arrow X in FIG. 12A when the amount of solar radiation changes. At this time, the voltage commander 1 considers that the amount of change ΔPin of the input power Pin has significantly changed, and ΔVref is output as a large value, so that the operating voltage command Vref may greatly change. . On the other hand, in the power value corrector 2, when the variation ΔVin of the input voltage Vin is small, the input power P
If in the variation ΔPin varies greatly, and regarded also of the Ru good to insolation changes, the correction value ΔPr addition to the input power variation ΔPin of the voltage commander 1, thereby,
The fluctuation of the operating voltage command Vref will be suppressed.

For example, when the input power change ΔPin changes to a small value and the input power change ΔPin changes to a large negative value as the amount of solar radiation decreases, a correction value ΔPr> 0 is added to the input power change ΔPin. By this, ΔP = ΔPin +
It decreases with ΔPr, and therefore ΔVref decreases, and the fluctuation of the operating voltage command Vref is suppressed.

As described above, the voltage commander 1 having the function of searching for the maximum power point on the PV characteristic of the solar cell and outputting a command, and the voltage commander 1 when the amount of sunshine changes.
Due to the coexistence with the power value corrector 2 having the function of correcting the command from, the operating voltage command Vref is largely moved while the operating voltage command Vref is largely shifted from the optimum operating voltage Vop which is the maximum power point. , The change width of the operating voltage command Vref becomes small,
Power fluctuations near the maximum power point are reduced, output power characteristics as shown in FIG. 3 are obtained, and power loss can be reduced. In addition, efficient power generation is possible even when there is a large change in the characteristics of the solar cell, such as when clouds flow rapidly.

The power value corrector 2 in the above embodiment
As a method of calculating the correction value ΔPr by the method, a method of using a fuzzy operation based on the magnitude of the input voltage change ΔVin and the input power change ΔPin is adopted.
The fuzzy calculation method will be described by taking as an example the case where the PV characteristic of the solar cell 50 changes between P1 and P2 shown in FIG.

When .DELTA.Vin is positive and small and .DELTA.Pin is positive and large, a large negative .DELTA.Pr is output in order not to change the voltage command Vref. When ΔPin is small even though ΔVin is positive and large and is largely deviated from the optimum operating voltage Vop, ΔPr> 0 is output in order to greatly change the voltage command Vref. When ΔVin is positive and large and ΔPin is positive and very large in accordance with the change in the amount of sunshine, the voltage command Vref moves to the optimum operating voltage Vop side, so the voltage command Vref is hardly added. When .DELTA.Vin is positive and large and .DELTA.Pin is large and negative, .DELTA.Vref <0 is left as it is, and it departs from the optimum operating voltage Vop. Therefore, a large .DELTA.Pr is added. In addition, since the case of ΔVin is negative and the calculation corresponding to is performed, the description thereof will be omitted.

FIG. 5 shows the correction value Δ in the above cases
The rule matrix of Pr is shown in FIG.
Positive (sign is positive), Z: Zero (zero),
N: Negative (sign is negative), and the circled numbers represent the operation as indicated by the arrow in FIG. 4.

6 (a) to 6 (c) show examples of the shape of the membership function used in the fuzzy calculation of the above-mentioned correction value ΔPr. Depending on the calendar information built into the device or the command information input from the outside, the above ΔVin, ΔP
By appropriately changing the magnitudes of P, Z, and N of in and ΔPr, that is, the parameters of the membership function, the correction value ΔPr is obtained by using, for example, the min-max single centroid method.
Can be calculated and optimum MPPT control can be performed. In particular, the amount of solar radiation differs greatly between summer and winter, and the PV characteristic changes greatly. Therefore, depending on the season, the magnitudes of P, Z, and N of ΔVin, ΔPin, and ΔPr, that is, the member The parameters of the ship function are shown in FIG.
The optimum MP throughout the year by adjusting like
It is possible to perform PT control.

In the above embodiment, the case where the step-down chopper is used as the power converter to convert the direct current into the direct current is explained. However, as shown in FIG. 8, the voltage type inverter 9 and the alternating current power source 10 are incorporated. It is also possible to apply to a solar power generation device that converts direct current to alternating current.

In the above embodiment, the input voltage change Δ
The configuration using Vin and the input power change ΔPin has been described, but a configuration using the current change may be used.

Further, in the above embodiment, the output from the corrector 2 is the correction value ΔPr of the electric power value, but as shown in FIG. 9, the operating voltage command output from the voltage commander 1 as the voltage correction value ΔVr. Vref may be corrected.

[0029]

As described above, according to the invention of claim 1, the maximum power point on the PV characteristic of the solar cell is searched based on the voltage, current or power information of the solar cell, While instructing it, the above command is corrected based on the correction information that is output by determining changes in solar cell characteristics such as the amount of solar radiation and element temperature. Even when the characteristics of the solar cell change significantly, such as when the power consumption is severe, the command change width near the maximum power point can be minimized. Therefore, while maintaining the responsiveness until reaching the maximum power point, it is possible to suppress fluctuations near the maximum power point, reduce power loss, and improve conversion efficiency and power generation efficiency. .

Further, as in claim 2 and claim 3,
If both the command device and the correction device output the command and the correction value based on the sign of the voltage change or the current change of the solar cell and the power change amount, the amount of solar radiation or the element temperature will increase or decrease in either direction. Even if it fluctuates, fluctuations near the maximum power point can be suppressed as described above to reduce power loss.

Further, the correction value in the correction device is
As in claim 4, the calculation is performed using a fuzzy operation based on the voltage change or the current change of the solar cell, and further, in the fuzzy operation, the form of the membership function is defined as in claim 5. When the changeable parameter is changed by the built-in calendar information or the command information from the outside, the correction value is set based on the control rule determined according to the magnitude of the change amount of the PV characteristic of the solar cell. Since it is calculated, it is possible to smoothly follow the maximum power point under the sensitivity adapted to the magnitude of the change amount and always execute the optimum MPPT control.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing only a specific configuration of a voltage commander and a power value corrector, which are main parts in a photovoltaic power generator according to an embodiment of the present invention.

FIG. 2 is a main part P- for explaining the operation of the embodiment.
It is a V characteristic view.

FIG. 3 is an output power characteristic diagram according to the embodiment.

FIG. 4 is a diagram illustrating a method of calculating a correction value by fuzzy calculation.

FIG. 5 is a table showing a rule matrix of correction values by fuzzy calculation.

FIG. 6 is an exemplary diagram of a membership function.

FIG. 7 is an exemplary diagram of membership functions corresponding to seasons.

FIG. 8 is a block diagram of a photovoltaic power generator according to another embodiment of the present invention.

FIG. 9 is a block configuration diagram of a main part of a solar power generation device according to another embodiment of the present invention.

FIG. 10 is a block diagram showing a schematic configuration of a conventional solar power generation device.

11 is a specific configuration diagram of FIG.

FIG. 12 is a PV characteristic diagram of a solar cell.

FIG. 13 is a P-V characteristic diagram of a main part for explaining a conventional MPPT control operation.

FIG. 14 is an output power characteristic diagram of a conventional solar power generation device.

[Explanation of symbols]

1 Voltage command device (command device) 2 Power value corrector (correction device) 50 solar cells 54 Control circuit (control device)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-251911 (JP, A) JP 62-85312 (JP, A) JP 7-31157 (JP, A) JP 63- 58517 (JP, A) JP 62-139017 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G05F 1/00-7/00 H02M 3/00-3/44 H02M 7/42-7/98

Claims (3)

(57) [Claims] 1. A solar power generation device for generating electric power by using a solar cell, wherein a command is obtained by obtaining an operating voltage or operating current for generating maximum power based on the voltage, current or power information of the solar cell. From the command device and the correction device, which determines the characteristic change of the solar cell based on the voltage, current or power information of the solar cell, and outputs correction information to the command device. e Bei a control device for controlling the power converter based on the output information, the command device, a voltage or current change marks in the solar cell
And the operating voltage that produces the maximum power
Or the correction device
Is the sign of the solar cell voltage or current change and the power change
Based on the minute, the correction value of the power change value used in the above command device
A solar power generation device characterized by being output . 2. The correction value in the correction device is fuzzy based on the voltage or current change and the power change of the solar cell.
Photovoltaic device according to claim 1 which is shall be calculated using the I operation. 3. In the fuzzy operation, membership
The parameters that can change the form of the
The solar power generation device according to claim 2 , wherein the solar power generation device is changed according to render information or command information from the outside .