KR20060087822A - Maximum power point tracking method of solar cell for solar powered cellular phone and tracking device adapted the method - Google Patents

Abstract

The present invention relates to a method of tracking the maximum power point of a solar cell for a solar cell rechargeable cell phone and a maximum power point tracker of the solar cell to which the method is applied in a solar cell rechargeable cell phone to obtain the maximum power from the solar cell. .

The maximum power point tracking method of a solar cell according to the present invention is a maximum power point tracking method of a solar cell for a solar cell rechargeable cell phone consisting of a maximum power point controller and a battery controller, the maximum power point controller while scanning the control input The maximum power point of the solar cell is tracked by finding the maximum value of the output current and then holding the value.

Description

Maximum Power Point Tracking Method for Solar Cell Rechargeable Cell Phone and Tracker Applied with the Method {MAXIMUM POWER POINT TRACKING METHOD OF SOLAR CELL FOR SOLAR POWERED CELLULAR PHONE AND TRACKING DEVICE ADAPTED THE METHOD}             

1 is a voltage-current and power versus voltage characteristic curve of a solar cell in the prior art.

(a) Solar cell current-voltage characteristics (b) Solar cell power-voltage characteristics

2 is a voltage / current waveform diagram of a battery and a solar cell during pulse discharge in the prior art.

3 is a maximum power point tracking capability test results for each mode according to the present invention.

The present invention relates to a method for tracking the maximum power point of a solar cell for a solar cell rechargeable cell phone, in particular, the maximum of the solar cell for a solar cell rechargeable cell phone of a new method for obtaining the maximum power from the solar cell in the solar cell rechargeable cell phone The present invention relates to a power point tracking method and a maximum power point tracker of a solar cell to which the method is applied.

The present invention focuses on the fact that the conventional tracking method does not operate correctly under pulse load discharge conditions, and proposes and implements a new tracking method and proved it by experiment.

The prior art used a method called Perturb & Observation (P & O), which is a method of finding the maximum power point by observing a change in solar cell output generated by changing the solar cell voltage little by little.

However, in the prior art as described above, under the pulse load discharge situation, the battery voltage, the current, the solar cell voltage, and the current all change abruptly. In this case, there is a problem that the conventional P & O method may malfunction.

The solar cell rechargeable cell phone consists of a solar cell, a cell phone battery, and a solar cell controller. The solar cell is a non-linear current source that generates current in proportion to the amount of light incident, and the generated voltage is proportional to the band-gap voltage of the diode, and in general silicon solar cell, at 25 [oC] 0.56 [V] is maintained.

1 is a voltage-current and power vs. voltage characteristic curve of a solar cell in the prior art, and FIG. 2 is a voltage / current waveform diagram of a battery and a solar cell during pulse discharge in the prior art.

As shown in the figure, since the state of the solar cell varies depending on the temperature and the amount of light, the power that can be obtained from the solar cell also changes. That is, in the case of 5 [Watt] solar cell, it is the value obtained from the reference light quantity (AM0) of 25 [oC]. Therefore, the power generated when the temperature changes or the light quantity varies from 70 [%] to 130 [%] of the reference value. Will change. Therefore, in order to obtain the maximum power from the solar cell under changing circumstances, the maximum power point controller is required. Algorithms for tracking the maximum power point of a solar cell have been developed for several decades, and the most commonly used Perturb & Observation (P & O) method is to observe the change in power generated by changing the solar cell voltage. The generated power is multiplied by the solar cell voltage and the current, and the power change relative to the voltage is shown in FIG. 1.

However, the main disadvantage of this method is that it requires a memory to store the previous state value and a multiplier to multiply the voltage and current. In addition, when the pulse load is connected, the battery voltage is also reduced because the battery is discharged during a high rate of discharge period, since the voltage and current of the solar cell and the voltage and output current of the battery have a correlation, The current will change as well. This relationship is shown graphically in Figure 2.

Under these conditions, when the conventional P & O method is used, there is a sudden change in battery voltage and solar cell voltage. It may malfunction. Therefore, other algorithms must be used instead of P & O.

The present invention has been proposed in order to solve the problems in the prior art as described above, the maximum power point tracker of the solar cell to accurately track the maximum power point of the solar cell even in the pulse load discharge applied in the mobile phone The purpose is to provide.

In addition, another object of the present invention is to provide a method for tracking the maximum power point of the solar cell to accurately track the maximum power point of the solar cell even when the pulse load discharge applied in the mobile phone.

According to a preferred embodiment of the present invention for achieving the object as described above, in the maximum power point tracking method of the solar cell for a solar cell rechargeable cell phone consisting of a maximum power point controller and a battery controller, the maximum power point controller is A method of tracking the maximum power point of a solar cell is provided by tracking the maximum power point of the solar cell by finding the maximum value of the output current while scanning the control input and then holding the value.

Advantageously, the algorithm for generating a reference voltage in the maximum power point controller may be characterized by increasing Iout (k)> Iout (k-1) => Vsa_ref, decreasing Iout (k) <Iout (k-1) => Vsa_ref. Characterized in the same way.

According to another aspect of the present invention, in the maximum power point tracker of the solar cell for a solar cell rechargeable cell phone consisting of a maximum power point controller and a battery controller, the maximum power point controller scans the control input while the maximum value of the output current The maximum power point tracker of the solar cell is provided by tracking the maximum power point of the solar cell by finding and then holding this value.

Hereinafter, a maximum power point tracking method of a solar cell for a solar cell rechargeable mobile phone according to the present invention and a maximum power point tracker of the solar cell to which the method is applied will be described in detail with reference to the accompanying drawings.

The battery of the cell phone powers the cell phone to make a call, and periodically discharges pulses in a slot mode. Since the solar cell is a non-linear current source and its operating characteristics vary in proportion to the external temperature and the amount of incident light, a solar cell controller capable of detecting and controlling the state of the solar cell is required. The solar cell controller is largely composed of a maximum power point controller and a battery controller, the present invention relates to a device for designing and operating the maximum power point controller.

Referring to FIG. 2, in the existing technology, if there is no loss of power stage, the energy of the solar cell is equal to the product of the current flowing through the output stage and the voltage of the battery. Therefore, if the voltage of the battery changes very slowly and is assumed to be constant, the maximum value of the output current corresponds to the maximum power point of the solar cell.

Psa = Vsa * Isa = Vbat * Iout (1)

Psa (max) becomes proportional to Iout (max). In other words, the maximum power point can be obtained by tracking the maximum value of the output current. In this case, there is no need for a multiplier or differential to control, and no information about the voltage / current of the solar cell is required. However, only a very small filter is needed to cope with the instantaneous reduction of the output current due to pulse discharge. It can also be implemented in very simple hardware and software.

To implement the above description, the algorithm for generating the reference voltage is as follows.

Iout (k)> Iout (k-1) => increase Vsa_ref

Iout (k) <Iout (k-1) => Vsa_ref reduction (2)

This configuration results in a very simple and highly reliable maximum power point controller.

In order to examine the performance of the maximum power controller, three characteristic curves of the solar cell were given by using the solar cell simulator, and in each case, an experiment was conducted to determine whether the maximum power point was followed. Table 1 below gives the solar cell parameter settings for each mode. The definitions of the parameters given in the table are as follows.

Voc: Open circuit voltage

Vmp: Maximum power point voltage

Imp: Maximum power point current

Pmp: Maximum power point power

mode Voc [V] Vmp [V] Imp [mA] Pmp [W] One 7.54 6.03 90 0.58 2 9.67 7.67 90 0.74 3 12.43 10.36 90 0.95

3 is a maximum power point tracking capability test results for each mode according to the present invention.

Here, the process of finding the maximum value of the output current while scanning the control input using the algorithm of Equation (2) to show that it accurately follows the maximum power point is shown. . In other words, it shows the maximum power point during the tracking process and maintains this value during the MPPT holding phase. The experiment was carried out by changing the parameters of the solar cell for each mode, and the result shows that it has a very good maximum power point tracking ability. Looking at the change in output current value for the control input in the experimental diagram of mode 1, it can be seen that it is a very simple structure that scans the control input and finds the maximum value of the corresponding output current. As shown in FIG. 3, the pulse discharge load influences all of the solar cell voltage, the control input, and the output current due to the periodic pulse discharge load. However, there is no problem in finding and maintaining the maximum current. The experimental diagrams of modes 2 and 3 also show robust maximum power point tracking capability despite discharge disturbance.

According to the present invention, a method for tracking the maximum power point of a solar cell and a maximum power point tracker of the solar cell to which the method is applied, the effect of obtaining the maximum power from the solar cell in the solar cell rechargeable cell phone. There is a useful invention.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited thereto, and various modifications can be made based on the following claims.

Claims (4)

In the solar cell maximum power point tracking method for a solar cell rechargeable cell phone consisting of a maximum power point controller and a battery controller, The maximum power point controller tracks the maximum power point of the solar cell by scanning the control input to find the maximum value of the output current and then holding the value. Way. The method of claim 1, wherein the algorithm for generating a reference voltage in the maximum power point controller Iout (k)> Iout (k-1) => increase Vsa_ref Iout (k) <Iout (k-1) => Vsa_ref Decrease Maximum power point tracking method of a solar cell, characterized in that made in the same manner. In the solar cell maximum power point tracker for a solar cell rechargeable cell phone consisting of a maximum power point controller and a battery controller, The maximum power point controller tracks the maximum power point of the solar cell by scanning the control input to find the maximum value of the output current and then holding the value. . The method of claim 3, wherein the algorithm for generating a reference voltage in the maximum power point controller Iout (k)> Iout (k-1) => increase Vsa_ref Iout (k) <Iout (k-1) => Vsa_ref Decrease Maximum power point tracker of the solar cell, characterized in that made in the same manner.

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