JP3402387B2 - Maximum power tracking method for solar cells - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation system using a solar cell, and more particularly, to a maximum power of a solar cell which maintains an operating point so that an output is maximized. Related to tracking method. 2. Description of the Related Art Conventionally, a solar power generation system using a solar cell is used for charging a storage battery once with energy generated by the solar cell and reusing the storage battery, and for using a motor via a chopper or an inverter. It is used for driving, for use after being converted to a commercial frequency power supply by an inverter, or for use alone or in conjunction with a distribution network as a power supply. In that case, the solar cell is relatively expensive and the conversion efficiency is not high, so it is important to utilize the generated energy as effectively as possible. By the way, as for the characteristics of the solar cell, the output power with respect to the operating voltage or the operating current changes according to the change in the illuminance and the temperature. In other words, the operating point of the voltage or current at which the maximum power is output changes due to changes in illuminance or temperature, so that the solar cell automatically tracks its maximum power operating point under any conditions and uses solar energy efficiently. A system for performing the operation is disclosed (for example, Japanese Patent Application Laid-Open No. 61-97721). FIG. 3 is a basic configuration diagram showing the specific contents, in which the power generated by the solar cell 1 is transferred to a load such as a storage battery, a motor, and a power distribution network via a smoothing capacitor 2 and a power controller 3 such as a chopper or an inverter. Equipment 4
In a system having a main circuit 10 for supplying power to the power supply, the power controller 3 is feedback-controlled so that the output voltage of the solar cell 1 detected by the voltage detector 5 becomes a value set by the voltage setter 6, A minute signal is added to or subtracted from the voltage set value by the superimposing device 7. At this time, a power operation comparator 9 uses a signal from the voltage detector 5 and a current detector 8 for detecting an output current of the solar cell. Depending on whether the calculated power has increased or decreased, the voltage set value of the voltage setter 6 is corrected in a direction in which the output of the solar cell 1 increases. To explain the principle of correcting the voltage setting value of the voltage setting unit 6, for example, when increasing the voltage set value by the signal superposition unit 7, as shown in FIG. 4, during operation in the output voltage V _0, the superposed voltage If the amount of change ΔP in power P when ΔV is added is positive, it is determined that output voltage V ₀ is smaller than maximum power operating point voltage V _max , and V ₀ + ΔV
Is the new operating point. If the change amount ΔP is negative, it is determined that the output voltage V ₀ is higher than the maximum power operating point voltage V _max , and V ₀ −ΔV is set as a new operating point. By repeating this operation, the output of the solar cell 1 can be brought closer to the maximum power operating point for a while. In FIG. 4,
Although the case where the superimposed voltage ΔV is positive is shown, even when a negative value is given as ΔV, similar results can be obtained by reversing the method of determining the sign of the change amount ΔP. A similar operation can be performed using a current control loop instead of the voltage control loop. In the prior art, however, the operating point of the operating load device is varied in order to determine which side of the maximum operating point is the current operating point. There must be. This causes a change in the load state, and has a disadvantage that a desired load state cannot be maintained. In addition, depending on the characteristics of the load device, it may take time to follow the actual voltage with respect to the change in the voltage command value. There is a problem that an accurate operating point cannot be obtained due to the occurrence. An object of the present invention is to provide a solar cell maximum power tracking method capable of confirming a current operating point of a solar cell without changing an operating point of a load device. [0004] In order to solve the above problems, the present invention provides a main circuit for supplying power generated by a solar cell to a load device through a smoothing capacitor and a power controller. Controlling the output of the voltage detector or the current detector so that the output of the voltage detector for detecting the output voltage of the solar cell or the current detector for detecting the output current becomes equal to the set value of the voltage or current setting unit. The voltage is set so that the operating point of the solar cell moves in the direction in which the power increases in accordance with the amount of change in the power output from the power operation comparator from the output of the voltage detector and the output of the current detector. In the maximum power tracking method for a solar cell that corrects a value, the solar cell side of the main circuit with respect to the smoothing capacitor, a superimposed voltage for correcting a voltage set value or A superimposed current is applied. According to the above means, a superimposed voltage source or a superimposed current source for generating a superimposed voltage or a superimposed current for correcting a voltage set value is inserted closer to the solar cell than the smoothing capacitor of the main circuit. Therefore, the influence of the superimposed voltage or superimposed current on the load equipment is prevented by the smoothing capacitor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to embodiments shown in the drawings. FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, a voltage detected by a voltage detector 5 that detects an output voltage of the solar cell 1 in a main circuit 10 that supplies power generated by the solar cell 1 to a load device 4 via a smoothing capacitor 2 and a power controller 3. Is feedback-controlled so that the power controller 3 has a value set by the voltage setting device 6,
Based on the signals from the voltage detector 5 and the current detector 8 for detecting the output current of the solar cell 1, whether the power calculated by the power calculation comparator 9 has increased or decreased, the voltage setting unit 6 The configuration in which the voltage set value is corrected in the direction in which the output of the solar cell 1 increases is substantially the same as the configuration of the conventional example shown in FIG. The difference from the conventional example is as follows. That is, conventionally, the addition or subtraction of a small signal to or from the voltage set value by the signal superimposing device is stopped, and instead, the voltage set value described with reference to FIG. A superimposed voltage source 11 for generating a superimposed voltage ΔV for correction is inserted. By the way, since the voltage of the smoothing capacitor 2 cannot be changed suddenly, it can be regarded as constant for a short time. Therefore, if the voltage generated by the superimposed voltage source 11 is short, the operating point of the solar cell 1 changes by that voltage, but the voltage of the smoothing capacitor 2 is constant, so there is no effect on the load device 4. . Strictly, the detected voltage of the voltage detector 5 changes, which affects the load device 4 through the control system. However, since it takes only a short time, it can be absorbed by the time constant of the control system and the load device. In this manner, when the power operation comparator 9 is operated in synchronization with the timing of applying the superimposed voltage ΔV, the current operation with respect to the maximum power operation point is performed based on the principle of correcting the voltage set value described earlier with reference to FIG. Point determination is possible. FIG.
FIG. 14 is a configuration diagram showing another embodiment, in which a current set by a current setting unit 6 ′ is superimposed instead of a voltage when a voltage set value is corrected. Superimposed current source 12 in parallel with solar cell 1
And a reactor 13 is inserted into the smoothing capacitor 2 on the solar cell 1 side. The reactor 13 is a superimposed current power supply 1
This is to prevent a short-time current from the second circuit from flowing into the smoothing capacitor. The current control is used as the control system, the current operating point is determined from the change in power when the current operating point is changed, and the operation of approaching the maximum power operating point is the same as the operation of superimposing a voltage. The superimposition of the voltage and the current can be easily achieved by preparing the superimposed voltage source 11 or the superimposed current source 12 separately and switching over by a semiconductor switch or the like. As described above, according to the present invention, the operating point of a solar cell can be determined in a short time without changing the operating point of a load device, and based on this, highly accurate operation can be performed. There is an effect that a maximum power tracking method for a solar cell that tracks the maximum power can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a basic configuration of an embodiment of the present invention. FIG. 2 is a block diagram showing a basic configuration of another embodiment of the present invention. FIG. 3 is a block diagram showing a basic configuration of a conventional example. FIG. 4 is an explanatory diagram illustrating a principle of correcting a voltage set value of a voltage setter 6; [Description of Signs] 1 solar cell, 2 smoothing capacitor, 3 power controller,
4 Load equipment, 5 Voltage detector, 6 Voltage setting device, 6 '
Current setting device, 8 current detector, 9 power operation comparator,
10 main circuit, 11 superimposed voltage source, 12 superimposed current source,
13 Reactor

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadao Ishii 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Inside Yaskawa Electric Co., Ltd. (56) References JP-A-4-308431 (JP, A) JP-A Heihei 4-149712 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05F 1/67 G05F 1/10 H01L 31/04

Claims (1)

(57) [Claim 1] A main circuit for supplying power generated by a solar cell to a load device via a smoothing capacitor and a power controller, and a voltage for detecting an output voltage of the solar cell. The output of the voltage detector or the current detector is fed back to the power controller so that the output of the detector or the current detector that detects the output current becomes the set value of the voltage or the current setter. The maximum power tracking of the solar cell in which the voltage set value is corrected so that the operating point of the solar cell moves in the direction in which the power increases in accordance with the amount of change in the power output from the power detector and the output of the current detector. In the method, a superimposed voltage or current for correcting a voltage set value is applied to the solar cell side of the main circuit with respect to the smoothing capacitor. Power tracking method.