JP4268948B2 - Operation method of solar system - Google Patents

Description

  The present invention relates to a method for operating a solar system.

  As is well known, a solar cell, a converter electrically connected to the solar cell, a load electrically connected to the converter, a storage battery electrically connected to the converter, and the storage battery A solar system is known that includes an external power generation device that is electrically connected to the power source.

  In such a solar system, when determining the storage battery specifications of the solar independent power supply base, conventionally, comparing the safety factor to the extent that the system failure does not occur due to the occurrence of non-sunshine from the average load current from the past days The storage battery capacity that was largely estimated was determined.

  However, in this case, since the design is performed so as to cover all the periods of non-sunshine in the past data, the maximum specification is reached, and a battery having an excessive capacity has been installed. Also, if the sun continues beyond the design expectations, the system will go down.

  Therefore, regardless of the state of the storage battery, the administrator periodically went to the site to manually operate the power generator installed regularly to perform supplementary charging / charging of the storage battery.

Conventionally, Patent Documents 1 to 3 listed below are known as technologies relating to a device for measuring the remaining amount of a battery, a spontaneous road sign device using a solar cell, and the like. Patent Document 1 relates to a method and an apparatus for measuring the remaining amount of a battery based on a binary value of a voltage and a leaving time. In Patent Document 2, an external power input terminal is provided on a self-luminous road sign body, and an external power supply device is connected to the external power input terminal, so that external power from the external power supply device is also generated in addition to power generated by a solar cell. The present invention relates to a self-light-emitting road sign body and a self-light-emitting road sign device configured to charge a power storage device. Patent Document 3 relates to a power supply apparatus that enables power supply to a built-in battery from both a solar battery and an external power supply and that can automatically confirm that power is being supplied.
JP-A-11-133122 JP-A-11-222824 JP 2003-111303 A

  The present invention has been made in consideration of such circumstances, and avoids excessive design of the storage battery capacity to cover all the non-sunshine periods of the past data, and avoids the administrator visiting the site for charging work. Furthermore, it is an object of the present invention to provide a method for operating a solar independent power supply base station that can avoid a system down in a non-sunshine period exceeding the specification.

A method for operating a solar system according to the present invention includes a solar cell, a converter electrically connected to the solar cell, a load electrically connected to the converter, and an electrical connection to the converter. In a method for operating a solar system comprising a storage battery and an external power generation device electrically connected to the storage battery,
If the storage battery is not charged due to non-sunshine days, the battery voltage data from the battery voltage characteristics at a fixed time will be used to pass the data 3 points from the 3 points where the battery voltage tends to decrease. A step of calculating a secondary expression of voltage and time, a step of predicting a battery voltage drop state from this secondary expression, and calculating a time to reach a battery voltage at a discharge caution level; and And charging the storage battery with an external power generator.

  According to the present invention, even if the battery capacity decreases, the capacity can be recovered automatically by charging with the power generation device, and it is not necessary to overdesign the storage battery capacity so as to cover all the non-sunshine periods of past data. The system down due to the voltage drop can be avoided. In addition, the manager does not go to the site to charge. Furthermore, long-term unmanned operation is possible.

Hereinafter, the present invention will be described in more detail.
First, a solar system according to the present invention will be described with reference to FIG.
Reference numeral 1 in the figure indicates, for example, a solar cell (PV: Photovoltaic) installed on the roof of a building. A load 3 such as a transmission / reception unit or an electric lamp is electrically connected to the solar cell 1 via a DC / DC converter (converter) 2. The converter 2 is connected to a storage battery 4 that charges power from the solar battery 1 or supplies power to the load 3. A measuring unit 5, a processing unit 6, a determination unit 7 and an external power generator 8 are sequentially electrically connected to the storage battery 4. The external power generator 8 is electrically connected to the storage battery 4. The measurement unit 5 has a function of measuring the voltage of the storage battery 4. As will be described in detail later, the processing unit 5 has a function of performing a process such as approximately obtaining a quadratic expression based on voltage and time based on voltage data of three points of the storage battery, or obtaining an expected discharge end voltage. Have The determination unit 7 has a function of determining whether or not to turn on the external power generation device 8 by comparing the calculated expected end-of-discharge voltage date with a set value.

  In such a system, the power from the solar cell 1 is supplied to the load 3 via the converter 2 or the storage battery 4 is charged during sunshine. On the other hand, electric power is supplied from the storage battery 4 to the load 3 during non-sunshine hours or at night, and thus the output voltage of the storage battery decreases. Therefore, the measurement unit 5 always measures the voltage of the storage battery 4, and the processing unit 6 obtains the above secondary expression based on predetermined three points of data to obtain the expected end-of-discharge voltage date. Then, the determination unit 7 determines whether or not the external power generation device 8 is to be turned on by comparing a preset set value with the calculated expected date. When it is determined to be ON, the external power generation device 8 is operated to supply power to the storage battery 4 to compensate for the shortage of the storage battery 4.

  In addition, the solar system mentioned above shows an example, The structure is not limited to the thing of FIG.

The method for obtaining the approximate expression from the voltage data is as follows. Here, since the approximate expression is a quadratic expression, it can be determined if there are three data points.
[How to find 3 data points]
First, three points where the battery voltage tends to decrease are used. The data uses a certain time on the discharge side in a time zone without sunlight, for example, a battery voltage at 4 am. For example, data 1, data 2 and data 3 are stored in a data box and used in comparison with newly obtained data 4.

[How to find an approximate curve that passes through three points]
Next, an approximate curve passing through three points is obtained. Here, each data 1-3 is always
“Data 1> Data 2> Data 3”
Are in a relationship. The comparison method is performed as follows.

1. When data 3> data 4
A quadratic expression is calculated from data 2, data 3, and data 4.
2. When data 3 = data 4
A quadratic expression is calculated from data 1, data 2, and data 3.
3. When data 3 <data 4
(3-1) Data 2> Data 4
A quadratic expression is calculated from data 1, data 2, and data 4.
(3-2) When data 2 = data 4
Not calculated → not estimated
(3-3) Data 2 <Data 4
(3-3-1) When data 1> data 4
Not calculated → not estimated
(3-3-2) When data 1 = data 4
Not calculated → not estimated
(3-3-3) When data 1 <data 4
Not calculated → not estimated Only when there are three data points in the data box, it is considered that the voltage tends to decrease due to lack of sunshine, and the time for non-sunshine compensation is estimated. In addition, when there is an empty space in the other data boxes, it is considered that the state of charge is in a recovery tendency, and thus the estimation of the non-sunshine compensation time is not performed.

Next, a method for estimating the non-sunshine compensation time from three points of data will be described.
First, using the fact that the discharge characteristics up to the final discharge (1.9 V) of the battery can be approximated by a quadratic equation, a quadratic equation passing through three measured points is obtained. Next, the time of non-sunshine compensation (time to reach the discharge end voltage) is calculated from the equation.

First, the quadratic expression to be obtained is
aX ² + bX + c = Y (1)
Put it. Next, three points of data (time X, voltage Y) are set as, for example, (X ₁ , Y ₁ ), (X ₂ , Y ₂ ), (X ₃ , Y ₃ ), and these are substituted into the above equation (1). ,
a (X ₁ ) ² + bX ₁ + c = Y ₁
a (X ₂ ) ² + bX ₂ + c = Y ₂
a (X ₃ ) ² + bX ₃ + c = Y ₃
And If these are rearranged, the relationship shown in the following formula (2) is established. Further, in the equation (2), when the symbol A is the equation (3) shown in the following equation 2, the equation (2) becomes the equation (4) shown in the following equation 3.

When A ⁻¹ (inverse matrix of matrix A) is applied to both sides of the above equation (4), equation (5) shown in the following equation 4 is obtained, and the coefficients a, b, and c of the quadratic equation can be obtained.

Next, in order to obtain the coefficients a, b, and c, if the three points of data are (−1, V ₁ ), (0, V ₂ ), (1, V ₃ ), the following equation (5) 6), and A ⁻¹ is represented by Equation (7) shown in Equation 6 below.

When the coefficients a, b, and c are obtained from the above equation (7),
a = (− Y ₁ + 2Y ₂ −Y ₃ ) / (− 2)
b = (Y ₁ −Y ₃ ) / (− 2)
c = Y ₂
It becomes.

[Calculation method of time to reach end-of-discharge voltage of 1.9V]
Next, the time to reach the discharge end voltage 1.9V is calculated.
First, X where Y = 1.9V is obtained from the above equation (1). Substitute Y = 1.9 into equation (1).
aX ² + bX + c = 1.9
If we put c-1.9 = d,
aX ² + bX + d = 0
And
1) When b ² -4ac ≧ 0
X is obtained by the following equation.
X = {− b ± (b ² −4ad) ^1/2 } / 2a
2) When b ² -4ac <0
Although there is no solution, there is a tendency to discharge, but the amount of charge increases compared to the previous day, and it is considered that there is a tendency to recover, and time calculation is not performed.

Here, the solutions X ₁ and X ₂ (X ₁ ≦ X ₂ ) obtained from 1) above are compared, and the values of X ₁ −1 and X ₂ −1 are compared. The time required to reach a final voltage of 1.9V.

  The above-described method is a method for obtaining a quadratic expression that passes through three data points. When this expression becomes a primary expression, X that reaches the discharge end voltage of 1.9 V is obtained by this primary expression, and X− Let 1 be the time to reach the discharge end voltage.

  Next, the time required to reach the end-of-discharge voltage is calculated, and if the time is within 2 days, it is expected that the system will be down due to a decrease in the storage voltage. Then, this result is obtained, and an operation signal is input to the power generator for automatic operation control, which is movable for a preset time, and charges the storage battery. In this way, system down due to a decrease in the storage voltage is prevented.

  Note that the setting time described above is two days, and the present invention is not limited to this time.

Next, a specific example will be described.
(Example)
Part of battery voltage data for December 2003 is as shown in Table 1 below. However, the battery voltage indicates data at 4 am.

  The battery voltage data, the data daily average, and the land-based sunshine hours are as shown in FIG.

Next, a quadratic expression is determined in order to make a prediction until the discharge end voltage is reached. Here, three points of data for determination are selected according to the rules described above. That is, since the battery voltage was 2.039 V on December 10, this is stored as data 1 in the data box. Since the storage battery voltage dropped to 2.038 V on the following 11th day, this is stored as data 2. However, since it recovered to 2.059 V on the 12th, the previous data 2 is deleted, and 2.059 V on the 12th is newly stored as data 1. And since it dropped to 2.056V on the 13th, it was stored as data 2 and was the same as 2.056V until the 15th, so 2.059V on the 12th and 2.056V on the 13th Continue to store two values. Next, since it decreased to 2.054V on the 16th, it was stored as data 3, and now the condition of data 1> data 2> data 3 was satisfied. Will be calculated. Further, since the data 4 on the next 17th is further lowered to 2.043 V, the data 2 is stored at 2.056, the data 3 is 2.054, and the data 4 is 2.043. The data selected (stored) according to the rules are as shown in Table 2 below.

  In Table 2 above, when the data are arranged side by side, a quadratic expression is determined and prediction is performed. The graph at that time is as shown in FIG. In FIG. 3, the horizontal axis represents the days of December 2003.

Then, a quadratic equation is determined, and a time for reaching the discharge end voltage of 1.9 V is predicted. For example, let's predict on the 16th and 17th. A quadratic equation is determined from the data on the 16th and 17th. When this equation and the curve drawn are shown in the graph, it is as shown in FIG. In FIG. 4, the horizontal axis shows the days of December 2003. Moreover, the curve (a) in FIG. 4 is a curve predicted by the 16th day, and becomes Y = 0.000X ² −0.0085x + 2.089. On the other hand, the curve (b) is a curve predicted on the 17th, and becomes Y = −0.0045X ² −0.0565x + 1.879.

Here, in the prediction on the 16th, the battery voltage is in a downward trend, but since the amount of charge has increased compared to the previous day, it is determined that there is a recovery tendency and there is no concern of reaching the end-of-discharge voltage. . Further, in the prediction on the 17th, the discharge end voltage is reached in about 4 days.
In the same manner, when the time to reach the final discharge voltage is 2 days or less, the power generation device is automatically operated to charge the storage battery.

  Thus, according to the above embodiment, when the storage battery voltage is constantly measured by the measurement unit and the non-sunshine day continues and the storage battery is not charged, the battery discharge characteristics are obtained from the storage battery voltage data at a fixed time. After calculating the secondary expression of the voltage and time passing through the three data points using the, and predicting the battery voltage drop state from the secondary expression, and calculating the time to reach the battery voltage of the discharge attention level Based on the calculated time, the storage battery is charged by the external power generator. Therefore, even if the battery capacity is reduced, it is automatically charged by the external power generator, so the capacity can be recovered, and there is no need to overdesign the storage battery capacity to cover all the non-sunshine periods of past data, and the battery voltage drops. System down due to can be avoided. In addition, the manager does not go to the site to charge. Furthermore, long-term unmanned operation is possible.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The block diagram for demonstrating the solar system which concerns on this invention. The characteristic view which shows the relationship between the battery voltage data which concerns on the Example of this invention, a data daily average, and the sunshine time according to land. The battery voltage characteristic view based on the data for determining the quadratic formula which concerns on the Example of this invention. The figure which shows the quadratic curve for estimating the discharge end voltage which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2 ... Converter, 3 ... Load, 4 ... Storage battery, 5 ... Measuring part, 6 ... Processing part, 7 ... Judgment part, 8 ... External power generator.

Claims (1)

A solar cell, a converter electrically connected to the solar cell, a load electrically connected to the converter, a storage battery electrically connected to the converter, and an electrical connection to the storage battery In a method for operating a solar system including a connected external power generator,
If the storage battery is not charged due to non-sunshine days, the battery voltage data from the battery voltage characteristics at a fixed time will be used to pass the data 3 points from the 3 points where the battery voltage tends to decrease. A step of calculating a secondary expression of voltage and time, a step of predicting a battery voltage drop state from this secondary expression, and calculating a time to reach a battery voltage at a discharge caution level; and And a step of charging the storage battery with an external power generator based on the method.

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