JPH104631A - Solar power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably start and stop a photovoltaic power generation system, by attaching a resistor having a preset resistance value to the output side of an auxiliary solar battery, provided near or side by side with a main solar battery and fetching the voltage value across both ends of the resistor to a controller. SOLUTION: A photovoltaic power generation system which supplies electric power to a load, by converting the DC output power of a solar battery 1 into AC power by means of a power converter 3 is provided with an auxiliary solar batter 2, and a resistor R, having a preset resistance value, is attached to the output side of the battery 2 so as to start and stop the system, in accordance with the voltage across both ends of the resistor. Consequently, when the condition of the intensity Pn of solar radiation of starting and stopping the system is set, the intensity Pn of solar radiation can be monitored by measuring the voltage across both ends of the resistor R, because the resistance value of the resistor R is fixed. Therefore, the operation of the system after starting can be controller stably with accuracy and, at the same time, whether or not electric power can be secured when the system is stopped, can also be discriminated surely, because the automatic starting and stopping conditions are decided, in accordance with the intensity Pn of solar radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photovoltaic power generation system.

[0002]

2. Description of the Related Art A photovoltaic power generation system mainly comprises a solar cell and a power converter such as an inverter.
It converts solar energy into electricity. This system is also roughly divided into two types, one of which is equipped with a storage battery, and is a system that charges the solar cell output power during the day and can be used at night. Another method is a method in which, when the output power amount of the photovoltaic power generation system becomes excessive, the power flow is reversed to the transmission line side. Since this method can sell surplus electric power, it has a great merit for the user, and the penetration rate is expanding. Regardless of the method, the amount of power obtained varies depending on the amount of solar radiation and temperature. Therefore, a method of efficiently using solar energy by controlling a power conversion device based on the output of a solar cell has been proposed.

For example, in Japanese Patent Publication No. Sho 62-52541, an auxiliary solar cell having the same characteristics as the main solar cell is mounted in addition to the main solar cell from which electric power is extracted, and the short-circuit current of the auxiliary solar cell is measured. It is controlled to estimate the maximum output current of the main solar cell. In the above-mentioned known example, although the auxiliary solar cell is used, since the purpose is to obtain the maximum value of the output power by using the auxiliary solar cell, the start and stop are not described. Photovoltaic power generation systems are difficult to perform easily due to the characteristics of solar cells, and various measures have been devised in the industry.

[0004] As an example of a method of controlling the start and stop of the photovoltaic power generation system, a method based on the open-circuit voltage of a solar cell is described in a research document issued by the New Energy Foundation. In this method, although what percentage of the operating voltage is used to start the solar cell, it does not mention that the output characteristics of the solar cell change depending on the solar radiation intensity or the temperature. The stop condition is determined by looking at the current value on the load side for 20 minutes. If the output of the power converter is reduced during this time due to the decrease in the intensity of solar radiation, the current on the system side is reduced by the capacitor on the power conversion side. Or as an exciting current of the transformer. Therefore, if the setting of the sensor detects a small current, the sensor may not stop due to a malfunction that is regarded as an output current from the power converter.

[0005]

In the above-mentioned conventional example, the control of the maximum output of the main solar cell using the open-circuit voltage or the short-circuit current of the auxiliary solar cell is described.・ The stop condition is not mentioned. Further, in the conventional example, the characteristics of the main solar cell and the auxiliary solar cell need to be the same.

In the method in which the solar cell is started by the open voltage of the solar cell, the open voltage becomes large even with a small solar radiation intensity which cannot take power. There are many factors that make it difficult to set operating conditions, such as high open circuit voltage and no start-up due to high open-circuit voltage, resulting in problems such as lack of stability.

An object of the present invention is to stably start and stop a photovoltaic power generation system.

[0008]

In order to achieve the above object, the present invention provides an auxiliary solar cell mounted near or adjacent to a main solar cell, and a resistance of a predetermined value is provided on the output side of the auxiliary solar cell. Was attached, and the voltage value at both ends of the resistor was taken into the control device. The magnitude of the solar radiation intensity was calculated from the voltage value at both ends of the resistor, and the system could be started / stopped by the set solar radiation intensity.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a schematic configuration of a solar power generation system for explaining the present invention, and FIGS. 2 and 3 show output characteristics of a solar cell.

1 is a main solar cell, 2 is an auxiliary solar cell, and 3 is a power converter. 10 is a main solar cell 1 and a power converter 3
A manual switch 5 for opening and closing the connection with the power supply 5 is a protection device for opening and closing the photovoltaic power generation system and the system side 8.

The photovoltaic power generation system converts DC output power of the solar cell 1 into AC power by a power converter 3 and supplies power to a load (not shown). Recently, when the condition of the power characteristic is satisfied, surplus power after use in the load can be reversely flown to the system side 8. The condition of the power characteristics is as follows.
Is determined by measuring the values of
The protection device 5 is opened and closed according to the state. Therefore, the computer 6 determines that the output of the power converter 3 is
It is necessary to determine whether or not coordination is possible, and to start or stop the photovoltaic power generation system.

There are various determination methods for operating the photovoltaic power generation system. In the present invention, the auxiliary solar cell 2 is used as shown in FIG. A resistor R having a predetermined value is attached to the output side of the auxiliary solar cell 2, and the voltage across the resistor is used to start and stop the solar power generation system. The reason for providing the auxiliary solar cell 2 is that a resistor having a specific resistance value R is connected to the output side of the solar cell, the power is continuously consumed, and the solar radiation intensity is monitored. This is because it is achievable and the smaller the capacity, the less cooling is required.

Although the method of setting the resistance value R is important, an example will be described with reference to FIGS. In FIG. 2, the horizontal axis represents the resistance value R, the vertical axis represents the output power P of the auxiliary solar cell 2, and Pn in the figure represents the solar radiation intensity. As an example, the solar radiation intensity Pn is 1.
It shows the characteristics of 0.5, 0.2 (kw / m ² ),
As can be seen from the figure, at each solar radiation intensity Pn, the output power P becomes maximum at a certain resistance value. A plot of this maximum output point is the characteristic indicated by an asterisk. When the solar irradiance Pn decreases, the maximum output point moves to the higher resistance value R. This indicates that when the solar irradiance Pn is low, power cannot be extracted if the resistance value R is low. The maximum output point where the solar radiation intensity Pn is 0.2 (kw / m ² ) is the resistance value R = 230 (Ω) in this example, but the resistance value R = 230 ( Ω) output power P
Is larger than the maximum output power of 0.2 (kw / m ² ). That is, if the condition of the solar radiation intensity Pn for starting and stopping the photovoltaic power generation system is set, the voltage across the resistor may be measured and monitored by fixing the resistance value R. Although this tendency is not shown, even if there is a change in the temperature of the auxiliary solar cell 2, it is hardly affected, and this is a stable determination method.

An example of setting the solar radiation intensity Pn will be described with reference to FIG. The horizontal axis in FIG. 3 indicates the solar radiation intensity Pn, and the vertical axis indicates the operating voltage when the maximum power is output. The operating voltage is the power converter 3
Since the output voltage value is determined, it cannot be reduced too much. Therefore, as an example, in the present invention, the solar radiation intensity P
It is set to start when n = 0.2 (kw / m ² ) or higher, and to stop when n = 0.2 (kw / m ² ) or lower. Therefore, in FIG.
Resistance value R = 230 indicating the maximum output at 0.2 (kw / m ² )
(Ω). The voltage V across the resistor at that time
r is as follows, for example, assuming that the conversion efficiency of the auxiliary solar cell 2 is 0.1 and the ground area is 0.5 m ² .

Vr = (P × R) ⁰⁵ = (200 × 0.1 × 0.1.
5 × 230) ⁰⁵ = 48 (V) The terminal voltage Vr set as described above is taken into the computer 6 via the I / F board, and when the terminal voltage Vr becomes 48 (V), a start command is given to the system. Will be. Upon receiving the start command, the computer 6 sets the system side 8
The power supply state of the power converter 3 is checked by a voltage sensor 7 and the like. Next, when the terminal voltage Vr falls below 48 (V), the computer 6 stops the entire system. The stop condition is controlled so as to stop when the conditions are not satisfied while checking the values of the DC voltage sensor 11, the current sensor 9, and the voltage sensor 7 as well as the solar radiation intensity Pn.

If the terminal voltage at the time of starting and the terminal voltage at the time of stopping are the same, it is possible to stop immediately after starting, so that the starting voltage is larger than the resolution of the computer 6 than at the time of stopping. By making the value larger than the value, an operation such as chattering can be prevented.

In the above example, the solar radiation intensity Pn under the start / stop condition
Was set to 0.2 (kw / m ² ). This is because the characteristic of the auxiliary solar cell 2 taken as an example is that the solar radiation intensity Pn = 0.2
(Kw / m ² ) or less, because the operating voltage sharply decreases.
The solar radiation intensity Pn of the start / stop condition may be set by actually measuring the characteristics of the solar cell used. In the example, the solar radiation intensity P
Although the maximum output value of n = 0.2 (kw / m ² ) is set, the output of the auxiliary solar cell 2 can be used for the power source of the computer 6 and so on, so that the larger output is more advantageous. This is because the maximum point is better than the maximum point. However, there is no problem if the characteristic is measured in advance and set at a point deviated from the maximum value. However, if the resistance value R is shifted to a smaller value, the power consumed by the resistance increases when the solar radiation intensity Pn is large. , It is better to shift to the larger resistance value R.

In the present invention, a single-phase circuit in which the transformer 4 is inserted on the output side of the power converter 3 has been described. However, a single-phase circuit without the transformer 4 or a three-phase circuit system can be started and operated in the same manner. Stop conditions can be defined.

Although the characteristics of the auxiliary solar cell 2 are not mentioned in the present invention, the purpose is to measure the solar irradiance Pn to perform the start / stop operation.
There is no problem even if they do not have the same characteristics.

Another embodiment of the present invention will be described with reference to FIG. In FIG. 4, instead of a pure resistance, a display such as a lamp holding a set resistance value is connected.
In the present invention, since the resistor R consumes power, the power can be used to display whether the system is operating or not so that the operating state can be visually confirmed.

FIG. 5 shows an embodiment of the mounting position of the auxiliary solar cell 2 according to the present invention. Although the auxiliary solar cell 2 is described separately from the main solar cell 1 in FIG. 1, in the present embodiment, one of the arrays of the main solar cell 1 is used, and the main solar cell 1 is used.
Is used as the auxiliary solar cell 2. By arranging the auxiliary solar cell 2 in the center, there is a feature that the influence when a part is shaded can be reduced.

Another embodiment of the present invention will be described with reference to FIG. In this embodiment, the end portion 2 in the main solar cell 1 array is used.
In this embodiment, auxiliary solar cells 21 and 22 are arranged at individual locations.
As the size of the main solar cell 1 increases, the influence of shadows on trees and objects nearby increases. Especially in the early hours in the morning when starting / stopping, or in the evening, the length of the shadow becomes longer, and the effect becomes more susceptible. In such a case, as in this embodiment,
There is a feature that more accurate judgment can be made by performing processing such as measurement at a plurality of locations and taking an average value. In addition, when providing in several places, it is desirable to arrange so that it may become a symmetrical position in the array of the main solar cell 1. FIG.

[0024]

According to the present invention, since the automatic start / stop condition is determined by the magnitude of the solar radiation intensity Pn, the operation after the start can be controlled accurately and stably, and whether or not the power can be secured even at the time of stop. Has the effect of being able to reliably determine whether
Further, there is a feature that the voltage across the resistor can be used as a power supply for display or control.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of the system of the present invention.

FIG. 2 is a characteristic diagram of the solar cell of the present invention.

FIG. 3 is a characteristic diagram of solar radiation intensity and operating voltage according to the present invention.

FIG. 4 is an explanatory view of a second embodiment of the present invention.

FIG. 5 is an explanatory view of a third embodiment of the present invention.

FIG. 6 is an explanatory view of a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Main solar cell, 2 ... Auxiliary solar cell, 3 ... Power conversion device, 6 ... Computer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H02N 6/00 H01L 31/04 K (72) Inventor Masatoshi Mimori 7-chome 1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Makoto Minase 4-3, Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi Techno Engineering Co., Ltd.

Claims (6)

[Claims] 1. A system that includes a solar cell and a power converter, converts DC power into AC power, and supplies power to a load. The system includes an auxiliary solar cell that is provided in parallel with a main solar cell that supplies power. A photovoltaic power generation system comprising: a resistor connected to the output of the auxiliary solar cell; a means for measuring a terminal voltage of the resistor; and a function for starting and stopping a system according to the magnitude of the terminal voltage. system. 2. The solar power generation system according to claim 1, wherein a display device of a lamp is used as said resistor. 3. The photovoltaic power generation system according to claim 1, wherein the output voltage set value of the auxiliary photovoltaic cell differs between when the system is started and when it is stopped. 4. The photovoltaic power generation system according to claim 1, wherein said auxiliary solar cells are arranged in a part of an array of said main solar cells. 5. The photovoltaic power generation system according to claim 4, wherein when one auxiliary solar cell is provided, the auxiliary solar cell is arranged near a central portion of the main solar cell array. 6. When a plurality of auxiliary solar cells are provided,
The photovoltaic power generation system according to claim 4, wherein the photovoltaic power generation system is arranged at a symmetric position in the main solar cell array.