US20080141998A1

US20080141998A1 - Maximum power point tracking system for the solar-supercapacitor power device and method using same

Info

Publication number: US20080141998A1
Application number: US11/954,219
Authority: US
Inventors: Ming-Hsin Sun
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-12-18
Filing date: 2007-12-12
Publication date: 2008-06-19
Also published as: TW200827974A

Abstract

A maximum power point tracking system, named flash supercapacitor-solar power device, and method for a solar power system, which mainly adds a pulse-power supercapacitor for being operated in a dynamic equilibrium are disclosed. The duty ratio D is changed and the voltage variance of the supercapacitor is observed to determine the next adjusting direction of the duty ratio D of the DC/DC converter. In the present invention, only a voltage value of the supercapacitor is needed to be monitored and no current-detection is needed. The output power of the solar power system can be actually estimated. The maximum power is traced in an oscillatory way. Therefore, the operation process of the perturbation and observation method, which is generally implemented currently, is simplified. By utilizing the steady-state equilibrium of the supercapacitor, only the voltage of the supercapacitor needs to be detected, and there is no need to measure and calculate the voltage and current values. The system is simple and easily accessible, which is a maximum power point tracking system and method with high efficiency for a solar power system.

Description

FIELD OF THE INVENTION

The present invention relates to a novel maximum power tracking point device and method for the solar power system, and more particularly to a system and method for utilizing solar energy to generate electricity.

BACKGROUND OF THE INVENTION

Due to the highly-developing industry and hurriedly-increased population, the energy resources on earth are consumed with unprecedented speed. It is expectable that some energy resources, which prop up human civilization in recent hundreds years, will be exhausted within the coming generations. The petroleum on earth may run out in 40-50 years, while the generation of natural gas can last only 60 years and the mineral resources of uranium can only support the use for about 70 years. Even for coal mine, which is estimated to last longer, the period should be no more than about 200 years. Such finite energy resources are not nearly enough for the endlessly developing human civilization in the future. Accordingly, the exploitation of alternative energy sources is of great urgency and necessity, and renewable energy is exactly what human beings aspire to.
The use of most renewable energies is limited to special regions; only the solar energy can be applied in most general conditions and can be scaled-down in applications. The applications of solar energy are advantaged in (1) being safe, reliable, low-noisy, and non-pollutant; (2) causing no greenhouse gas (3) gaining energy anywhere, without consuming fuel and using moving mechanical parts; (4) easy maintenance, long life-time, short installing period, and flexible scale; (5) no need of security guard and installation of power-supply cables; (6) low cost in remote districts; and (7) convenient combination with buildings. Therefore, much of energy providers' attention has come to solar energy.
The solar energy photoelectric transform can roughly be divided into three types: photovoltaic cells, solar radiation, and solar-decomposed water serving as the fuel for electric power generations. Wherein, the solar radiation applications are most economic for large-scaled power generations, and photovoltaic cells (solar cells) are preferably using in the medium/small-scaled applications. Solar cells are made of the semiconductor. The sunshine lighting on the solar cell forms current on the semiconductor surface. The current is stored as a DC power or converted into an AC power being connected to an AC grid in parallel.
The critical techniques of the photovoltaic power are (A) solar cell/photovoltaic panel; (B) tracking and obtaining of the maximum power points; 15 (C) technique for charging the battery; and (D) technique for the solar system discharging. The solar cells are made by semiconductor processes. Generally speaking, there are single crystal, polycrystalline, and amorphous solar cells. Furthermore, much recent interest has been directed towards the development of flexible or organic solar cells. The maximum conversion efficiency of the current commercial photovoltaic panel is below 18%. The tracking and obtaining of the maximum power point is the most concerted critical technology which needs to be improved urgently. The most important energy-storage medium for the medium/small solar power energy system and the islanding operation of a large-scaled solar power system is the accumulator (battery). In the solar power applications, the accumulator charging technique is critical and necessary. On the other hand, the system discharging technique is getting more important since the requirement of the user to the quality of the discharging of the solar energy system becomes higher.
The solar energy is nevertheless not a perfect renewable energy. The electric power generated by the solar power system will change according to the variances of the sunshine surroundings, the sunshine angle, and the temperature. That is to say, the solar energy is a variable renewable energy. The solar power generated at different time may be different to varied sunshine. Therefore, a maximum power point tracking (MPPT) method must be applied to obtain the maximum electric power of a solar cell. Normally, the electric power is indicated by the voltage and current. Therefore, these variables are often taken into consideration in the operation of a solar energy system to track and obtain the maximum power.
There is not a linear relationship between the voltage and the current of the solar cell while unique working curves may occur in responding to different atmosphere surroundings with different sunshine conditions and temperatures. As shown in FIG. 1, the voltage/current curves respectively represent a strong sunshine condition, a medium sunshine condition, and a weak sunshine condition. Further refer to the power/voltage diagram of the photovoltaic panel indicated in FIG. 2. It is shown that each of the working curves has a maximum power point, which is the point that the maximum power is obtained from the photovoltaic panel. According to various maximum power point tracking techniques, the voltage/current state for obtaining the maximum power, which has different time points varied with different surrounding conditions, is tracked so that the energy can be quickly obtained and input into the system. The conventional maximum power point tracking techniques include (A) voltage feedback method; (B) power feedback method; (C) perturbation and observation method, (D) incremental and conductance method; (E) line fitting method; and (F) real measuring method.
The most common used method is the perturbation and observation method. The system is as shown in FIG. 3. It is advantaged in its simple structure and fewer measuring parameters. Accordingly, this method is popularly used in the solar MPPT system. The basic algorithm is to periodically increase or decrease the resistance of the load 5 to change the terminal voltage of the photovoltaic panel 1 and to track and calculate the output power 2. Observe and compare the variance before and after the perturbation, and then accordingly determine whether to increase or decrease the resistance of the load 5 in the next period. If the output power increases, adjust the load 5 at the same trend. On. the other hand, if the output power decreases, change the variant direction of the load 5 at the next period. According to such repeatedly oscillatory perturbing and observing, a maximum power point of the solar cell will be approached.
The important character of the “perturbation and observation” MPPT method is to change the load of the output terminal by controlling the duty ratio D of the DC/DC converter 4 so as to perturb the output power of the photovoltaic panel in an oscillatory way, track and approach the maximum power point of the solar cell. When the maximum power point is approached, the oscillatory perturbing is not stopped and is still operated around the maximum power point. Once the incident intensity, the surrounding and the temperature of the sunshine are varied, the maximum power point for the operation of the solar power system will be changed accordingly, and the oscillatory perturbing will response to the change immediately to initiate a new maximum power point tracking.
The DC/DC converter is constructed by inductors, capacitors, diodes, and electric switches. The DC/DC converter can be a step-up, step-down, or step-up/step-down DC/DC converter, and a pulse signal is provided in cooperated with a pulse width modulation (PWM) device 3 or a pulse frequency modulation (PFM) device. The load of the terminal is adjusted by controlling the duty ratio so as to track the maximum power point.
The supercapacitors have excellent energy-storing ability, and, when being applied to solar energy devices, are advantaged in increased efficiency, long cycle life, maintain free, and extended operation time, etc. The U.S. patent No. 2004/0183982 discloses a solar energy charging system which utilizes a double-layered capacitor (i.e. a supercapacitor) as an energy-storing device. The solar system is adjusted and controlled by a DC/DC converter for tracking the maximum power point. In many electric applications such as the Real-Time Clock (RTC) reserving memory, and the solar energy LED lamp, the supercapacitors have substituted for the batteries. In the past, the energy density of the supercapacitors is far below that of the battery, and thus is limited in the energy-storing applications. However, in the recent years, the energy density of the supercapacitors increases rapidly, and thus the supercapacitors are implemented to substitute for batteries even more popularly. Even the DC power-accumulating of the solar power system are considered to utilize the supercapacitors, especially in the maximum power point tracking. U.S. patent No. 2006/0312102 further discloses an efficient solar power system charging to a supercapacitor circuit in the maximum power. It is designed to perform both the maximum power point tracking and the constant-current charging of a supercapacitor by one circuit. Furthermore, the supercapacitors are roughly divided into the energy-releasing type supercapacitors and the pulse-power type supercapacitors. The former has a battery-like characteristic, and is mainly used to store energy. Since the energy is stored in a physical way, the life and reliability of the energy-releasing type supercapacitors are far longer and higher than those of the chemical batteries. The latter is used to provide a strong pulse power. Its characteristic is similar to that of a capacitor with enormous power density.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a novel maximum power point tracking method and device for the solar power system, named “Peter perturbation-and-observation solar energy maximum power point tracking method” and device, which is a supercapacitor dynamic equilibrium method and able to be applied to all solar power energy systems.
The present invention provides a pulse-power supercapacitor electrically connected between a photovoltaic panel and a DC/DC converter. The supercapacitor with low internal resistance and fast response, servers as a steady-state input/output energy storing device. Accordingly, a novel, instant and efficient solar energy maximum power point tracking method is developed. Furthermore, an intelligent coordinating solar power system is designed based on this maximum power point tracking method.
Furthermore, the present invention provides a power tracking method applied to an solar power system comprising the steps of adding an pulse-power supercapacitor operated in a dynamic equilibrium; changing a duty ratio of a DC/DC converter; and observing a voltage variance of the said supercapacitor for determining a next adjusting manner of the said duty ratio of the said DC/DC converter, wherein only a voltage value of the supercapacitor is needed to be monitored and no current-detection is needed for calculating an output power of said solar power system, and tracking a maximum power point in an oscillatory way.

BRIEF DESCRIPTIONS OF DRAWINGS

The invention as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a voltage-current diagram of a photovoltaic panel exposed on sunlight with various intensities;

FIG. 2 is a power-voltage diagram of a photovoltaic panel exposed on sunlight with various intensities;

FIG. 3 is a flow diagram of a conventional perturbation and observation maximum power tracking method for a solar energy system;

FIG. 4 schematically illustrates the flow and system structure of the present invention;

FIG. 5 is a flowchart of a power tracking according to an embodiment of the present invention; and

FIG. 6 schematically illustrates the system structure according to another embodiment of the present invention.

DETAILED DESCRIPTIONS OF THE INVENTION

Normally, the output power P of the photovoltaic panel is needed to be calculated in a perturbation and observation MPPT method. If the power is not at the maximum point, the duty ratio of the DC/DC converter is adjusted so as to change the resistance of the load and thus vary the output of the photovoltaic panel. The output power P of the solar power system is then be calculated again. The two calculated output powers are compared to obtain the power change situation, and then the duty ratio of the DC/DC converter is adjusted accordingly. The process steps are repeated to obtain the maximum power in an oscillatory way.
The primary process is shown in FIG. 5. The value of the power P is indicated by the voltage and the current of the circuit. Therefore, the values of the voltage V and the current I of the system must be detected to calculate the power P: P=I×V.
As shown in FIGS. 4-6, in the present invention, the current I is not necessary to be detected and only the voltage V needs to be detected. In the method of the present invention, the pulse-power supercapacitor 7 is disposed between the photovoltaic panel 6 and the DC/DC converter 8 for serving as an electric energy buffer. The electric energy is generated by the photovoltaic panel 6, inputted into the pulse-power supercapacitor 7, and then outputted to the DC/DC converter 8. In a steady state, it can be seen that the net electric energy inputted in/outputted from the pulse-power supercapacitor 7 is zero, i.e. there is no electric energy accumulated and lost in the supercapacitor. The energy generated by the photovoltaic panel 6 totally flows into the DC/DC converter 8, and a dynamic equilibrium is established (i.e. steady state).

Electric energy of the solar power system W=P×t, wherein
P: power
t: time
therefore, W=I×V×t;
if we eliminate the time factor, i.e. let t−1 sec, then W=P=I×V.

At any moment, energy flowing into the pulse-power supercapacitor 7=energy flowing out of the pulse-power supercapacitor 7, i.e., the energy flowing from the photovoltaic panel 6 into the pulse-power supercapacitor 7 is equal to the energy flowing from the pulse-power supercapacitor 7 into the DC/DC converter 8. The energy generated by the photovoltaic panel 6=The energy flowing into the pulse-power supercapacitor 7=The energy flowing out of the pulse-power supercapacitor 7=The energy flowing into the DC/DC converter 8.
Therefore, the conventional perturbation and observation method for tracking the maximum solar power can only detect the power generated by the photovoltaic panel 6. In the present invention, the same function can be performed by detecting the energy or power of the pulse-power supercapacitor 7. The energy of the pulse-power supercapacitor 7 is related to its electric capacity:
W=½C×V ²

W: energy of the pulse-power supercapacitor 7,
C: electric capacity of the pulse-power supercapacitor 7,
V: voltage of the pulse-power supercapacitor 7.

Since the value of the electric capacity C of the pulse-power supercapacitor 7 is a constant, the energy of the pulse-power supercapacitor 7 can be indicated by the voltage of the pulse-power supercapacitor 7. That is, when the voltage of the pulse-power supercapacitor 7 is obtained, the energy of the pulse-power supercapacitor 7 is thus known, and so is the power of the photovoltaic panel. Since the method of the present invention only has to detect the voltage of the pulse-power supercapacitor 7, it is a simple and efficient method. The operation flowchart is shown in FIG. 5 and explained below.

(A) first detect the voltage Vc of the pulse-power supercapacitor 7; when the voltage value Vc exceeds a pre-set value, activate a maximum power point tracking system;
(B) change the duty ratio D of the DC/DC converter 8;
(C) detect the voltage again to obtain a new Vc; (D) if the new Vc is higher than the original Vc, adjust the duty ratio D of the DC/DC converter 8 in a trend toward the original variant direction; if the new Vc is lower than the original Vc, adjust the duty ratio D of the DC/DC converter 8 in a trend toward a reverse direction of the original variant direction,
(E) reset the value of Vc as new Vc value;
(F) repeat the above-mentioned steps.

When the maximum power of the photovoltaic panel 6 is obtained according to the method of the invention, the logic control circuit 10A will determine the charging mode according to the voltage situation of the accumulator 11. The accumulator 11 is charged by the current/voltage adjusted by the DC/DC converter 8.
When the accumulator 11 is in a low voltage, it is charged in a pulse-charging mode by the system until the voltage is above the present voltage. The energy generated by the photovoltaic panel 6 on the instance is totally charged into the accumulator 11. In the later stage of the charging, the accumulator 11 is charged to be full in a pulse-charging mode. According to a three-stage charging method, the charging is efficient, fast, and low energy lost.
The present invention provides an intelligent adjustable discharging mode. The discharging of the solar power system according to the present invention is adjustable. The discharging mode is determined by the logic control circuit 10A, and is controlled by the DC/DC converter 8 to execute a constant voltage/constant current/constant power discharging or other discharging operations. The DC/DC converter 8 is capable of changing the output condition of the accumulator.
The load 10 of the system can be a LED array, a lamp, a mechanical device, a monitoring equipment, a detecting apparatus, or a signal communicator, etc . . . . In case the load 10 is a LED array, the constant current is needed to control the luminance. The accumulator used for a solar power system is usually a 12V lead-acid battery for storing energy and discharging. When the accumulator is full-charged, the voltage is up to 16V, while the utilizing voltage range is between 13.8V to 11V. When the LED is driven by the accumulator 11, the driving current will vary because of the variation of the voltage of the lead-acid battery. Hence, the luminance of the LED will be getting darker. The constant power of the intelligent adjustable discharging is capable of keeping a constant luminance of the LED. The constant power control is capable of keeping the serial current passing through the LED constant, and thus preventing the streetlamp using the LED from getting darker. In some other cases such as a mechanical device, a monitoring equipment, or a detecting apparatus, the load 10 must operate in a constant voltage. A constant voltage can stabilize an operation of a machine. The system is capable of being discharging in a constant voltage, and thus is efficient. Even more, the constant voltage outputted to the load 10 can be turned higher.
In another embodiment of the present invention, a solar energy device utilizing an intelligent solar energy charging/discharging method based on the present invention is provided. It can be applied on solar energy LED lamp sources such as the solar street lights, the solar traffic signals lights, and various solar lights.
Generally speaking, the system based on the present invention is added with a pulse-power supercapacitor 7 for a dynamic equilibrium operation. By changing a duty ratio D of a DC/DC converter 8 and observing a voltage variance of the pulse-power supercapacitor 7, a next adjusting manner of the duty ratio D of the DC/DC converter 8 is determined. Accordingly, the maximum power can be traced in an oscillatory way.
In this method, only the voltage of the pulse-power supercapacitor 7 has to be monitored, and the current does not need to be measured. The output power of the solar power system can be actually estimated accordingly.
According to the concept, the present invention at least includes a photovoltaic panel 6, a pulse-power supercapacitor 7, a DC/DC converter 8, a logic control circuit 9, and a load 10.
The method of the invention includes the following steps of:

- (a) detecting a voltage value of the pulse-power supercapacitor 7;
- (b) when the voltage value of the pulse-power supercapacitor 7 exceeds a pre-set value, activating a maximum power point tracking system;
- (c) adjusting the duty ratio D of the DC/DC converter 8;
- (d) detecting a new voltage value of the pulse-power supercapacitor 7 again;
- (e) comparing the new and original voltage values of the pulse-power supercapacitor 7;
- (f) in case that the new voltage value is higher than the original voltage value, adjusting the duty ratio D of the DC/DC converter 8 in a trend toward an original variation direction;
- (g) in case that the new voltage value is lower than the original voltage value, adjusting the duty ratio D of the DC/DC converter 8 in a trend toward an reverse variation direction of the original variation direction; and
- (h) repeating steps (a)-(g) in sequence.

According to the above-mentioned method of the present invention, another novel intelligent coordinating solar power system, named flash supercapacitor 7-solar power device, is provided.
The flash supercapacitor 7-solar power device at least includes a photovoltaic panel 6, a pulse-power supercapacitor 7, a DC/DC step-up/step-down converter 8, an accumulator 11, a voltage detector for pulse-power supercapacitor 7 and first electric switch 12, a logic control circuit 10A, a second electric switch 13, a voltage/current guard circuit, a load 10, and a current detector. The operation processes include generating the electric energy through the photovoltaic transform of the photovoltaic panel; executing a maximum power tracking through the pulse-power supercapacitor 7 and the DC/DC converter 8; accumulating the solar energy by charging the accumulator 11 in a three-stage-charging controlled by the logic control circuit 10A; and driving the load 10 in an intelligent adjusting method at final. In case the load 10 is a LED array, it is driven by a constant current, voltage or power stably. Accordingly, the luminance of the LED array will not be getting darker due to a voltage variance of the accumulator 11.
The photovoltaic panel 6 of the present invention is a photovoltaic unit array. The photovoltaic units can be connected in serial/parallel according to desired output voltage/current. The solar energy is transferred into electric power under sunshine in various strengths.
Furthermore, according to the above descriptions, the pulse-power supercapacitor 7 of the present invention is a capacitor with low internal resistance and high capacity and is capable of being an electric energy buffer. The pulse-power supercapacitor 7, operated in a dynamic equilibrium and a steady state, receives the electric energy outputted from the photovoltaic panel 6 and outputs electric energy to the DC/DC converter 8. The pulse-power supercapacitor 7 might be a metal-oxide supercapacitor, a carbon supercapacitor, a polymer supercapacitor, a hybrid supercapacitor, an aluminum electrolytic supercapacitor, or other similar high-capacity capacitors.
Moreover, the DC/DC converter 8 of the present invention is preferably a step-up converter 8 capable of adjusting the resistance of the load 10 so as to change the output voltage of the photovoltaic panel 6. The DC/DC converter 8 also might be a step-down converter 8, a step-up/step-down converter 8, or any other similar DC/DC converter 8.
In addition, a pulse signal is provided by a pulse width modulator to control the duty ratio D of the DC/DC converter 8, so as to adjust the output of the photovoltaic panel 8. The flash supercapacitor 7-solar power system of the present invention is a novel intelligent coordinating solar power system, which integrates functions of the maximum power tracking, the three-stage-charging, and the intelligent adjustable discharging.
The photovoltaic panel 6 of the present invention is a photovoltaic unit array. The photovoltaic units can be connected in serial/parallel according to desired output voltage/current. The solar energy is transferred into electric power under sunshine in various strengths. Furthermore, according to the above descriptions, the pulse-power supercapacitor 7 of the present invention is a capacitor with low internal resistance and high capacity and is capable of being an electric energy buffer. The pulse-power supercapacitor 7, operated in a dynamic equilibrium and a steady state, receives the electric energy outputted from the photovoltaic panel 6 and outputs electric energy to the DC/DC converter 8. The pulse-power supercapacitor 7 can be a metal-oxide supercapacitor, a carbon supercapacitor, a polymer supercapacitor, a hybrid supercapacitor, an aluminum electrolytic supercapacitor, or similar high-capacity capacitors. Besides, when the sunshine is weak, the weak current can be accumulated to a strong current before stored to the accumulator 11 or driving the load 10 directly.
When the sunshine is strong and the accumulator 11 is full-charged or almost full-charged, it is inefficient to accumulate the solar energy into the accumulator 11. In such a situation, the electric energy of the supercapacitor is preferably used for driving the load 10 directly. That is to say, the supercapacitor serves as a second accumulator 11. Accordingly, the designed capacity of the accumulator 11 of the solar power system can be reduced and thus the cost of the system construction is also reduced.
In the embodiment of the present invention shown in FIG. 6, the DC/DC step-up/step-down converter 8 receives the signal from the logic control circuit 10A to execute a maximum power point tracking on the solar energy outputted by the supercapacitor. The duty ratio D of the converter 8 is adjusted to obtain the maximum power of the photovoltaic panel 6. The charging method applied in the system of the present invention is an adjustable charging method. Furthermore, in the discharging process, the DC/DC step-up/step-down converter 8, under the control of the logic control circuit 10A, has the accumulator 11 to drive the load 10 in an intelligent adjustable way.
Moreover, the accumulator 11 is a secondary (rechargeable) battery, and is preferably in the system a lead-acid battery. It can also be a nickel-metal hydride (Ni-MH) battery or a lithium battery. In this system, the accumulator 11 serves as the first energy-storing device. The voltage detector of the pulse-power supercapacitor 7 of the present invention and the first electric switch 12 is connected among the photovoltaic panel 6, the supercapacitor 7, and the DC/DC step-up/step-down converter 8, and is controlled to be switched by the logic control circuit 10A. The voltage detector of the pulse-power supercapacitor 7 is the detecting point of the maximum power tracking of the solar energy system. The first electric switch 12 is capable of switching the connection of the photovoltaic panel input system/photovoltaic panel 6 to the pulse-power supercapacitor 7, the pulse-power supercapacitor 7 to the second electric switch 13, the pulse-power supercapacitor 7 to the DC/DC step-up/step-down supercapacitor 8, and the photovoltaic panel 6 to the DC/DC step-up/step-down converter supercapacitor 8. In addition, the logic control circuit 10A of the present invention is the control center of the pulse-power supercapacitor 7-solar power system, which receives the voltage status of the voltage detector of the pulse-power supercapacitor 7 and the accumulator 11, and the voltage/current status of the load 10. When executing the maximum power tracking of the system, the logic control circuit 10A controls the input of the photovoltaic panel, the output of the supercapacitor, and the duty ratio D of the DC/DC step-up/step-down converter 8 to adjust the resistance of the load 10. The logic control circuit 10A also controls the three-stage-charging during the charging process, and controls the electric energy to drive the load 10 in an intelligent adjustable way during the discharging process. The second electric switch 13 of the present invention is located behind the circuit relating to the photovoltaic panel maximum power tracking, and is connected between the accumulator 11 and the load 10, so as to switch the solar power system to the accumulator 11 for charging, or to the load 10 for discharging.
The voltage/current guard circuit is used for preventing damages caused by the over-charging or over-discharging of the accumulator 11, so as to extend the life of the accumulator 11. The load 10 of the system can be a LED array, a lamp, a mechanical device, a monitoring equipment, a detecting apparatus, or a signal communicator, etc . . . . Some of these devices, such as LED arrays, need to be operated in a constant current to control the luminance. Some other devices, such as mechanical devices, monitoring equipments, detecting apparatuses, etc . . . , need to be operated in a constant for stable operations. The system can drive the load 10 for various desired conditions in an intelligent adjustable and most efficient way.
Furthermore, the present invention further includes a current detector 14 for detecting a current of the load 10 and generating a detecting signal. The detecting signal is transmitted to the logic control circuit 10A through the voltage/current guard circuit 15 for controlling a current outputted from the accumulator to the load 10.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.

Claims

1. A maximum power tracking point method applied to an solar power system comprising the steps of adding an pulse-power supercapacitor. operated in a dynamic equilibrium; changing a duty ratio of a DC/DC converter; and observing a voltage variance of said supercapacitor for determining a next adjusting manner of said duty ratio of said DC/DC converter, wherein only a voltage value of said supercapacitor is needed to be monitored and no current-detection is needed for calculating an output power of said solar power system, and tracking a maximum power point in an oscillatory way.

2. The maximum power tracking point method of claim 1, comprising the following steps of:

(a) detecting an original voltage value of said pulse-power supercapacitor;

(b) when said voltage value of said pulse-power supercapacitor exceeds a pre-set value, activating a maximum power point tracking system;

(c) adjusting said duty ratio of said DC/DC converter;

(d) detecting a new voltage value of said pulse-power supercapacitor;

(e) comparing said original and new voltage values of said pulse-power supercapacitor;

(f) in case that said new voltage value is higher than said first voltage value, adjusting said duty ratio of said DC/DC converter in a trend toward an original variation direction of said duty ratio;

(g) in case that said second voltage value is lower than said original voltage value, adjusting said duty ratio of said DC/DC converter in a trend reverse to said original variation direction of said duty ratio; and

(h) repeating said steps (a)-(g) in sequence.

3. The maximum power tracking point method of claim 1, wherein said pulse-power supercapacitor is selected from various high energy-density and high power-density supercapacitors, ruthenium dioxide supercapacitors, carbon supercapacitors, metal oxide supercapacitors, polymer supercapacitors, gold capacitors, and aluminum electrolytic capacitors having high capacities.

4. The maximum power tracking point of claim 1, wherein said DC/DC converter is a step-up converter, a step-down converter, a step-up/step-down converter, or any other similar converter.

5. The maximum power tracking point method of claim 1, wherein solar energy inputted into/outputted from said pulse-power supercapacitor is in a dynamic equilibrium state, and said solar energy is transferred to said DC/DC converter; an output voltage of said photovoltaic panel and an input energy of said pulse-power supercapacitor are changed by adjusting said duty ratio of said DC/DC converter; the voltage value of said pulse-power supercapacitor serves as an energy characteristic of said pulse-power supercapacitor and is measured and compared at different times for observing an output energy change trend of said photovoltaic panel, so as to track a maximum power point of said solar power system.

6. The maximum power tracking point method of claim 1, wherein when an intensity of a sunshine is strong, said pulse-power supercapacitor undergoes a maximum power point tracking; when said intensity of said sunshine is weak or it is in a worse weather that only a weak solar energy generates, said supercapacitor accumulates weak electric energy transferred from said weak solar energy and charges a accumulator when accumulated energy become higher, wherein said pulse-power supercapacitor serves as an energy accumulator of said weak electric energy.

7. The maximum power tracking point method of claim 6, wherein a charging mode of said accumulator is based on a detected voltage of said accumulator, undergoing a pulse charging in an initial period, a full-speed charging in a middle period, and a pulse charging in an ending period, wherein in said full-speed charging, said electric energy generated by solar energy system is totally charged into said accumulator.

8. The maximum power tracking point method of claim 6, wherein said charging mode can be replaced by a normal charging mode such as a constant current charging, a constant voltage charging, a constant power, a two/three stages charging, or a speed charging.

9. The maximum power tracking point method of claim 6, wherein said steps of charging said accumulator include an intelligent-adjustable discharging step in which an output of said accumulator is set in an adjustable constant current, an adjustable constant voltage or an adjustable constant power for driving a load.

10. The maximum power tracking point method of claim 9, wherein in said discharging mode, said accumulator is controlled by a logic control circuit through a DC/DC step-up/step-down converter to keep a constant output which is not influenced when the voltage of said accumulator is reduced and said constant output can be raised to strengthen power outputted to said load.

11. The maximum power tracking point method of claim 10, wherein when said accumulator is going to be full-charged by said discharging step and there is still solar energy converted, said pulse-power supercapacitor will serve as a second accumulator for outputting power to said load without passing through said accumulator.

12. A maximum power tracking point method applied to a solar power system comprising:

a photovoltaic panel;

a pulse-power supercapacitor, which is a dynamic-equilibrium energy-storing device for receiving energy outputted from said photovoltaic panel and outputting electric energy to a DC/DC converter;

said DC/DC converter, which is capable of adjusting an output voltage and energy of said solar power system; and a pulse width modulation driver for delivering pulse signal to control said DC/DC converter.

13. The maximum power tracking point method of claim 12, wherein said photovoltaic panel is constructed by a plurality of photovoltaic units connected in serial/parallel as needed; and

wherein said DC/DC converter is a step-up converter a step-down converter, a step-up/step-down converter or any other similar converter.

14. (canceled)

15. The maximum power tracking point method of claim 12, wherein said pulse-power supercapacitor is electrically connected to a logic control circuit which is electrically connected to a voltage/circuit guard circuit.

16. The power tracking method of claim 15, wherein said voltage/current circuit is connected to an accumulator electrically connected to a load for preventing said load from a damage caused by over charging/discharging of said accumulator.

17. The power tracking method of claim 16, wherein said load is selected from an LED array, a lamp, a mechanical device, a monitoring equipment, a detecting apparatus, and a signal-communicator, and said load is further connected to a current detector for detecting a current on said load.

18. The maximum power tracking point power tracking method of claim 16, wherein said accumulator is a Lead-acid storage battery, or a rechargeable battery selected from a Nickel-Cadmium battery, a Nickel-Metal Hydride battery, a Lithium-ion battery, a Lithium-polymer battery, and a Lead-acid storage battery.

19. The maximum power tracking point method of claim 1, wherein said photovoltaic panel is connected to a first electric switch, said first electric switch is electrically connected to said DC/DC converter, and said DC/DC converter is electrically connected to a second electric switch.

20. The maximum power tracking point method of claim 19, wherein said first and second electric switches are semiconductor electric switches which include higher operational speed than analog switches; and

wherein said logic control circuit is a microcontroller or a microcontroller-like controller.

21. (canceled)

22. The maximum power tracking point method of claim 15, further comprising a current detector for detecting a current of said load and generating a detecting signal transmitted to said logic control circuit through said voltage/current guard circuit for controlling a current outputted from a battery to said load.