JP2003288126A - Photovoltaic power generation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photovoltaic power generation device for performing the power generation control accurately by comprehending an AC output power from a DC power, using an efficiency table of a DC/AC converter. <P>SOLUTION: A self-sustaining operation method of a photovoltaic power generating device, which converts a DC power of a solar battery by a DC/AC convert, consisting of a chopper and an inverter and outputs the prescribed AC power, comprises a voltage detecting means which detects a DC voltage of the solar battery; a current detecting means which detects a DC current output from the solar battery; an input power calculation means which calculates an input power for the DC/AC converter by the multiplication of the detected DC voltage and the DC current; an efficiency table which specifies the relation obtained previously between the input power and the convert efficiency of the DC/AC converter; and an output power calculation means, which calculates an output power of the photovoltaic power generation device by the multiplication of the input power and the efficiency value of the efficiency table, and performs output control, based on the calculated output power value. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generator, and more particularly to a method for calculating output power when the photovoltaic power generator is operated independently.

[0002]

2. Description of the Related Art When performing a self-sustaining operation by a photovoltaic power generator, it is necessary to grasp the active power supplied to a load to control the power generation output, and to detect the voltage and current at the self-sustaining output end to determine the voltage and current. Find the value of cosφ from the phase difference between
It is desirable to calculate active power and perform output power generation control. However, in a device with a small capacity output, it is customary not to detect the current at the self-sustained output end from the viewpoint of reducing the number of parts and cost, and as shown in FIG. 3, the DC detected by the current detector 21 is not used. The self-sustained operation output power is calculated from the output current Iac of the / AC converter 11 and the self-sustained operation output voltage Vind. That is, the self-sustained operation output power P
out is Pout = Iac × Vind (where Ia
c is the output current of the DC / AC converter, and Vind is the self-sustained operation output voltage), and power generation control of the output is performed.

[0003]

However, in the above-mentioned method, there is no current detector at the self-sustained output end, and the current at the connection point between the DC / AC converter and the sine filter, that is, the combined current of the load current and the filter current. However, unlike the actual current at the load connection point, because of the use of, the output power cannot be grasped accurately and power generation control cannot be performed accurately. Further, if a current detector is provided at the self-sustained output end in order to accurately control the power generation, there is a problem that the cost of the device increases.

The present invention has been made under such a background, and the AC output power can be grasped from the DC power by using the efficiency table provided in the DC / AC converter, and the power generation output control can be performed accurately. It is an object of the present invention to provide a solar power generation device that can perform the above.

[0005]

According to a first aspect of the present invention, in a self-sustaining operation system of a solar power generation device, the generated power of a solar cell is converted into a predetermined AC power by a DC / AC converter and output. A voltage detecting means for detecting a direct current voltage of the solar cell, a current detecting means for detecting a direct current output by the solar cell, and a product of the detected direct current voltage and the direct current of the DC / AC converter. Input power calculation means for calculating input power, an efficiency table showing a relationship between the input power and the conversion efficiency of the DC / AC conversion unit acquired in advance, and an efficiency value based on the input power and the efficiency table. Output power calculation means for calculating the output power of the solar power generation device by the product of, and the power generation output control is performed based on the calculated output power value. To provide a location.

According to the present invention, the output power can be calculated from the input power of the DC / AC converter and the efficiency table showing the relationship between the input power and the conversion efficiency of the DC / AC converter. Power generation output control can be performed accurately based on the calculated output power value.

According to a second aspect of the present invention, in the solar power generation device according to the first aspect, the DC / AC conversion unit includes a chopper and an inverter.

According to the present invention, by configuring the DC / AC converter by an inverter, the generated voltage of the solar cell can be converted into a desired DC voltage for obtaining an AC output of 100 V, and the DC voltage can be applied to the inverter. A transformer or the like is unnecessary, and the configuration of the device can be simplified.
To obtain a 200V AC output, the DC / AC converter 1
It can be realized by being driven by the first chopper and the inverter.

The invention described in claim 3 is the same as claim 1
Alternatively, in the solar power generation device described in item 2, the calculated output power value is displayed on a display.

According to the present invention, the output power value can be obtained without detecting the current at the self-sustained output point and can be displayed on the display.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a solar power generation device according to an embodiment of the present invention. In this figure, reference numeral 10 is a solar cell, which generates DC power when it is exposed to sunlight. The generated DC power is input to the DC / AC converter 11 and converted into AC power.

Although not shown, the DC / AC converter 11
Is composed of an inverter, and converts the direct current voltage of the solar cell 10 into a desired direct current voltage in order to obtain an alternating current output of 100 V and supplies it to the inverter. Also, 20
In order to obtain a 0V AC output, the DC / AC converter 11 is driven by a chopper and an inverter. Since the AC power output from the DC / AC converter 11 contains harmonic components, it is sine-converted by the filter 12 and supplied to the load 13.

The control unit 15 controls the inverter of the DC / AC conversion unit 11 so that the solar cell 10 can supply the load 13 with AC power having a predetermined voltage and a predetermined frequency. In order to obtain a 200V AC output, the DC / AC converter 11 is driven by a chopper and an inverter. The control unit 15 is provided with, as an efficiency table 151, data indicating the relationship between the DC input power measured in advance and the conversion efficiency of the DC / AC conversion unit 11.

FIG. 2 is a graph showing a data example of the efficiency table 151. Point a is the efficiency when the DC power is at the rated load, and point b is the efficiency when the DC power is at 1/2 the load. Usually, the maximum efficiency point is near the load factor of 70 to 80%. Further, point c is the power consumption when there is no load, and of course the efficiency is zero. For simplification, the data of the efficiency table 151 is the data of the representative value of the DC voltage when generating each DC power, but the DC voltage may be used as a parameter to have a plurality of data for each DC power value. .

The output power calculation means 152 is for the solar cell 10.
Power generation voltage Vdc and the direct current I by the current detector 14
dc is detected, and the DC input power is calculated by the product of these detected values. Further, the product of the calculated value of the DC input power and the efficiency value obtained from the efficiency table is calculated as the AC output power value. This AC output power value is control means 1
The signal is input to 53, is used as a signal for controlling the DC / AC converter 11, and is sent to the display 17 to display the output power. With this method, the AC output power value can be obtained without detecting the current at the self-sustained output point, and the DC / AC converter 11 can be controlled with high accuracy.

The operation of one embodiment of the present invention has been described in detail above with reference to the drawings. However, the present invention is not limited to this embodiment, and the design is within the scope of the present invention. The present invention includes modifications and the like.

[0017]

As described above, according to the present invention, the following effects can be obtained. According to the invention of claim 1, the input power of the DC / AC converter, the input power and the DC
The output power can be calculated from the efficiency table showing the relationship with the conversion efficiency of the / AC converter, and the power generation output control can be performed accurately based on the calculated output power value.

According to the second aspect of the present invention, the DC / AC conversion unit is constituted by an inverter, so that the generated voltage of the solar cell is converted into a desired DC voltage for obtaining an AC output of 100 V and is applied to the inverter. Therefore, a transformer or the like is not needed, and the structure of the device can be simplified. In addition, in order to obtain 200V AC output, DC /
It can be realized by driving the AC converter 11 with a chopper and an inverter.

According to the invention of claim 3, the output power value can be obtained without detecting the current at the self-sustained output point and can be displayed on the display.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a solar power generation device according to an embodiment of the present invention.

FIG. 2 is a graph showing a data example of an efficiency table.

FIG. 3 is a block diagram showing a configuration of a solar power generation device according to a conventional technique.

[Explanation of symbols]

10 ... Solar cell 11 ... DC / AC converter 12 ... Filter 13 ... Load 14 ... Current detector 15 ... Control unit 16 ... Current detector 17 ... Display 21 ... Current detector 22 ... Control unit 121 ... Reactor 122 ... Capacitor 151 ... Efficiency table 152 ... Output power calculation means 153 ... Control means

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Claims (3)

[Claims] 1. A self-sustaining operation system of a photovoltaic power generation device for converting the generated power of a solar cell into a predetermined AC power by a DC / AC converter and outputting the AC power, and a voltage detection means for detecting a DC voltage of the solar cell. A current detection unit that detects a direct current output by the solar cell; an input power calculation unit that calculates an input power of the DC / AC conversion unit by a product of the detected DC voltage and the DC current; The output power of the photovoltaic power generation device is calculated by the product of the efficiency table showing the relationship between the input power and the conversion efficiency of the DC / AC conversion unit, and the product of the input power and the efficiency value of the efficiency table. And a power generation output control means for performing power generation output control based on the calculated output power value. 2. The solar power generation device according to claim 1, wherein the DC / AC conversion unit includes a chopper and an inverter. 3. The solar power generation device according to claim 1, wherein the calculated output power value is displayed on a display.