JP3493644B2 - Maximum power tracking method for photovoltaic system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of tracking the maximum output according to the illuminance and temperature in the operating state of a solar power generation system using solar cells.

[0002]

2. Description of the Related Art Conventionally, as a method of obtaining the maximum output in the operation state of a solar power generation system using a solar cell, the output current and voltage of the solar cell are input and the power and voltage of the solar cell are changed every predetermined sampling period. A method of controlling the output of the solar cell to the maximum by obtaining an appropriate power reference value or a current reference value that becomes the maximum power of the solar cell from the change or the change of the power and the current is disclosed. (For example, JP-A-61-194514). In addition, a pair of solar cells for detection are provided, one of which is used as a short-circuit current detection sensor, and the other of which is used as an open-circuit voltage detection sensor, and the amount of solar radiation is obtained by calculating the short-circuit current and open-circuit voltage from these sensors. Japanese Patent Application Laid-Open No. 63-181015 discloses that the output of the solar cell is controlled so that the output of the solar cell is maximized from this solar radiation amount.

[0003]

However, in the former prior art described above, the control response of the solar cell is poor, and the output power fluctuates due to load fluctuations, etc., so that there is a large range of variation in maximum power. was there. In addition, the latter prior art described above has a drawback in that a solar cell for a sensor is required, wiring is required from the installation location of the solar cell to a control device, and noise resistance is poor. An object of the present invention is to obtain a state of maximum power of a solar cell, which is accurate and has good responsiveness regardless of load fluctuation and which does not use a solar cell for a sensor.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a photovoltaic power generation system including a control device for supplying electric power generated by a solar cell to a load device via a power controller including an inverter. In the maximum power tracking method of, a short-circuit switch that short-circuits the output end of the solar cell,
An open switch for opening the output of the solar cell is provided,
The short circuit current when the output of the solar cell is short-circuited and the open circuit voltage when the open switch is opened are detected, and the illuminance and temperature at the time of detection are obtained from the short circuit current and the open circuit voltage, depending on the illuminance and temperature. The maximum power output condition proportional to the product of the short-circuit current and the open-circuit voltage is obtained from the characteristics of the solar cell determined by the above, and the maximum power output condition is input to the power controller.

[0005]

By the above means, the open switch is opened from the basic characteristics of the solar cell to obtain the open circuit voltage V _T of the solar cell to obtain the temperature in the operating state of the solar cell, and the short-circuit switch is short-circuited to the solar cell. Short circuit current I _L
Then, the illuminance of the solar cell in the operating state is obtained, and the maximum power point voltage V _MAX that is the maximum power is obtained for each temperature and each illuminance.

[0006]

EXAMPLES Examples of the present invention will be described below with reference to the drawings.
To do. FIG. 1 is a circuit diagram showing an embodiment of the present invention.
Power generated in 1 from smoothing capacitor 2 and inverter
Circuit for supplying power to the load device 4 via the power controller 3
In 10, the voltage detection for detecting the output voltage of the solar cell 1 is performed.
Output device 5, current detector 6 for detecting the output current, and solar power
Open the short circuit switch 7 that short-circuits the pond 1 and the main circuit 10.
And an opening switch 8 for opening. Voltage detector 5 and current
The output of the detector 6 is input to the power operation / comparator 9 for power consumption.
The output of the arithmetic comparator 9 is input to the voltage setter 11 and set.
The input voltage to the power controller 3 and feedback control
I am doing it. Here, FIG. 2 shows the temperature of the solar cell.
Current / electricity against voltage when changed as a parameter
It is an example of a force characteristic diagram. Figure 3 shows the parameters of the illuminance of the solar cell.
Current / power characteristics with respect to voltage when it changes as data
It is an example of the figure. In addition, the current with respect to the voltage of the solar cell 1
・ Power characteristics are voltage and current by changing temperature and illuminance in advance.
Output power was detected by detecting
Calculated as a dotted line curve by voltage and current,
Maximum power P for each temperature and illuminance_max Wanted
To be In Fig. 2, is there a change in the cell temperature of the solar cell?
Nevertheless, the short-circuit current I when the solar cell is short-circuited_L Is almost
It will be constant. On the other hand, the open circuit voltage V when the solar cell is opened
_T Indicates that there is a large change with temperature, and the maximum
Electric power P_max Is the short circuit current I _L And open circuit voltage V_T Proportional to the product of
ing. In Figure 3, according to the change of the illuminance of the solar cell
Short circuit current I_L Changes greatly, but the open circuit voltage V_T Is large
Shows that it does not change, and the maximum power P_max Is a short circuit
Flow I_L And open circuit voltage V_T Is proportional to the product of

From the above basic characteristics of the solar cell, the open switch 8 is opened to obtain the open circuit voltage V _T of the solar cell 1 to obtain the temperature in the operating state of the solar cell, and the short-circuit switch 7 is short-circuited to reduce the temperature of the solar cell. Short circuit current I of battery 1
By obtaining _L , it is possible to obtain the illuminance of the solar cell in the operating state and obtain the maximum power point voltage V _MAX that is the maximum power for each temperature and each illuminance. For example,
According to FIG. 2, the maximum power point voltage V _MAX is 1 at 75 ° C.
13.5V at 25V, 15.5V at 3.5V and 50 ° C
It becomes 7.5V. The characteristics of the relationship between the open-circuit voltage V _T of the solar cell 1 and the maximum power point voltage V _MAX and the relationship between the short-circuit current _IL and the maximum power point voltage V _MAX are stored in the power calculation comparator 9. Note that the power operation comparator 9 may be provided with a function generator for _{obtaining the} maximum power point voltage V _MAX from the open circuit voltage V _T and the short circuit current I _L. When obtaining the maximum power point voltage V _MAX in the operating state, it is instantaneous (1 m per several tens of seconds.
(about sec.) to open the open switch 8 to a no-load state or to make a short-circuit state by the short-circuit switch 7 and detect the open-circuit voltage V _T and short-circuit current I _L at that time by the voltage detector 5 and the current detector 6. Then, the power calculation comparator 9 obtains an approximate value of the maximum power point voltage V _MAX from the relationship with the temperature or the illuminance, and inputs it to the voltage setter 11 to set the power controller 3 to the sun. The output voltage of the battery 1 is controlled so as to have the maximum power. Further, the approximate value of the maximum power point voltage V _MAX obtained by setting the temperature by the open circuit voltage V _{T and} the maximum power point voltage V obtained by setting the illuminance by the short circuit current I _L
A more accurate maximum power may be obtained by performing correction such as taking the average value from the approximate value of _MAX .

[0008]

As described above, according to the present invention, from the power characteristics with the temperature and illuminance of the solar cell as parameters,
Obtain the voltage that gives the maximum power, and use that voltage as the set voltage to control it with the solar cell controller, so obtain the state of the maximum power of the solar cell that is accurate and does not use the sensor solar cell, regardless of load fluctuations. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a current / power characteristic diagram when the illuminance of the solar cell is constant and the temperature is a parameter.

FIG. 3 is a current / power characteristic diagram when the temperature of the solar cell is constant and the illuminance is used as a parameter.

[Explanation of symbols]

1 solar cell, 2 smoothing capacitor, 3 power controller,
4 load, 5 voltage detector, 6 current detector, 7 short-circuit switch, 8 open switch, 9 power calculation comparator, 1
0 main circuit, 11 voltage setting device

Claims (3)

(57) [Claims] 1. A maximum power tracking method for a solar power generation system including a control device for supplying electric power generated by a solar cell to a load device via a power controller including an inverter, wherein an output end of the solar cell is short-circuited. Short-circuit switch
An open switch for opening the output of the solar cell is provided,
The short circuit current when the output of the solar cell is short-circuited and the open circuit voltage when the open switch is opened are detected, and the illuminance and temperature at the time of detection are obtained from the short circuit current and the open circuit voltage, depending on the illuminance and temperature. The solar power generation system is characterized in that the maximum power output condition proportional to the product of the short-circuit current and the open-circuit voltage is obtained from the characteristics of the solar cell, and the maximum power output condition is input to the power controller. Maximum power tracking method. 2. The maximum power tracking method for a photovoltaic power generation system according to claim 1, wherein the characteristics of the solar cell are stored in the control device in advance, and the maximum power output condition is determined from the short-circuit current and the open circuit voltage. . 3. The maximum power tracking method for a photovoltaic power generation system according to claim 1, wherein the control device is provided with a function generator that determines a maximum power point voltage from the open circuit voltage and the short circuit current.