TWI419345B - Photovoltaic power apparatus and analog circuit for tracking maximum power thereof - Google Patents

Description

Solar power generation device and analogous maximum power tracking circuit

The present invention relates to a power generating device, and more particularly to a solar power generating device and its analogous maximum power tracking circuit.

In recent years, due to the increasing awareness of environmental protection and the rapid development of solar cells, power electronics and microelectronics technology, solar power generation has gradually been realized and applied to life. In many solar applications, it has been proven that the economics of solar power systems are superior to diesel power generation systems. Because the solar power system is fully automatic, highly reliable, and requires no guards, it is ideal for use in remote areas. However, when using solar cells, it is necessary to understand the operating characteristics of the solar cells, and the solar cells are often affected by the difference in the current solar illuminance, so that different output powers are generated.

FIG. 1 is a schematic diagram showing changes in output power and output voltage of a solar cell corresponding to illuminance. Referring to FIG. 1, the corresponding relationship between the output power of the solar cell and the output voltage is different under different illumination conditions, so it is often necessary to pass the maximum power tracker to enable the solar cell to operate at the maximum power output point. Therefore, in solar power systems, the maximum power tracker often plays a very important role. Many different maximum power tracking technologies have been developed today. The most common maximum power tracking techniques are voltage feedback method, power feedback method, disturbance observation method and incremental conductivity method.

Perturb and observe algorithms (P&O) is a commonly used maximum power tracking method. Perturbation observation is a digital maximum power tracking technique. The principle of the disturbance observation method is to change the output voltage of the solar cell through the duty cycle of the disturbance switch, and then measure the power variation and compare it with the power before the disturbance. If the power increases after the disturbance, it indicates that the direction of the disturbance (ie, increasing the output voltage or reducing the output voltage) is correct, and the disturbance can continue in the same direction. Conversely, if the power is reduced after the disturbance, the disturbance direction is incorrect and must be reversed. Disturb until the maximum power point of the solar cell is tracked. However, the disturbance observation method will still disturb the solar power generation system when the solar cell is operated at the maximum power point, so that the output voltage of the solar cell will move back near the maximum power point, thereby causing the system to oscillate and increasing the solar power generation system. Power loss. In addition, the disturbance value of the disturbance observation method is an important operational parameter. When a larger disturbance value is selected, the maximum power point can be tracked relatively quickly, but the disturbance at the maximum power point is large, thereby causing a large disturbance. Power loss; conversely, when a smaller disturbance value is selected, the speed at which the maximum power point is tracked is slower, but the disturbance at the maximum power point is smaller, so the disturbance loss caused is smaller.

Incremental conductance algorithm is another commonly used maximum power tracking method, and incremental conductivity method is also a digital maximum power tracking technology. Figure 2 is a schematic diagram of the operation of the incremental conductance method. Referring to FIG. 2, the purpose of the incremental conductance method is to let the output voltage of the solar cell reach the maximum power point voltage Vmax to obtain the maximum output power. While the slope of the maximum power Pmax is zero, it can be seen from the following equations (1) and (2) that when the output voltage of the solar cell is operated to the left of the maximum power point (ie, the region smaller than the maximum power point), dP/dV)>0; conversely, when the output voltage of the solar cell is operated to the right of the maximum power point (ie, an area larger than the maximum power point), (dP/dV) < 0.

Where P is the output power of the solar cell, V is the output voltage of the solar cell, and I is the output current of the solar cell. When (dP/dV) = 0, it can be simplified after finishing (1)

When the above formula (2) is met, it means that the system has reached the maximum power point, and it is no longer necessary to make voltage changes to the system. In terms of programming, the voltage increase and voltage reduction will affect the speed at which the solar power system tracks the maximum power point, so that the program execution is more complicated than other maximum power tracking methods, and in actual measurement, the maximum power tracking The effect will vary depending on the accuracy of the voltage sensor and current sensor.

The constant voltage control method is one of the simplest maximum power tracking methods, and the constant voltage control method is an analogous maximum power tracking technique. Figure 3 is a schematic diagram of the operation of the constant voltage control method. Referring to FIG. 3, the constant voltage control method controls the output voltage of the solar cell to a voltage VOP, and the voltage VOP is preset to be an operating voltage corresponding to all the maximum power points. Since the specific voltage is not the maximum power operating point of the solar cell corresponding to the current illuminance, the solar tracking efficiency of the constant voltage control method is not good, that is, the power consumption of the solar cell as a whole is large.

The linear approximation method is another simple maximum power tracking method, and the linear approximation method is also an analogous maximum power tracking technique. Figure 4 is a schematic diagram of the operation of the linear approximation. The linear approximation approximates the line 410 with a power approximating the plurality of maximum power points of the solar cell at different illumination levels, and operates the output voltage of the solar cell in accordance with the power asymptote 410 to achieve maximum power tracking. The maximum power tracking efficiency of the linear approximation method is better than the constant voltage control method, that is, the overall power consumption of the solar cell is low, but there is still a certain power loss.

The invention provides a solar power generation device and an analog-type maximum power tracking circuit thereof, which are selected by transmitting two power asymptotes respectively corresponding to maximum power points of different illumination ranges, and selecting the intersection voltages of the two power asymptotes The power asymptote used, and the power asymptote used to quickly find the maximum power voltage for the illuminance that should be down. Moreover, since the present invention transmits power asymptotes of two maximum power points respectively approximating different illumination ranges, the maximum power voltage found will be closer to the actual maximum power point to reduce the overall power consumption of the solar power generation device.

The invention provides a solar power generation device, which comprises a solar battery, a DC-to-DC conversion circuit, a current detecting unit, a voltage detecting unit, a control unit and an analog-type maximum power tracking circuit. Solar cells are used to provide output voltage and output current. The DC-to-DC conversion circuit is coupled to the solar cell and can receive the pulse width modulation signal to convert the output voltage and the output current into an operating voltage according to the pulse width modulation signal. The current detecting unit is coupled to the solar cell to detect the output current and output the first detecting voltage. The voltage detecting unit is coupled to the solar cell to detect the output voltage and output the second detecting voltage. The control unit is coupled to the voltage detecting unit and can receive the maximum power voltage to generate a pulse width modulation signal, and adjust the pulse of the pulse width modulation signal according to the comparison result of the second detection voltage and the maximum power voltage. Wave width. The analogy maximum power tracking circuit is coupled to the current detecting unit, the voltage detecting unit and the control unit to compare the second detecting voltage and the intersection voltage of the first power asymptote and the second power asymptote. Selecting one of a first power asymptote and a second power asymptote, and generating a maximum power voltage according to the selected first power asymptote or second power asymptote and the first detection voltage, wherein A power asymptote and a second power asymptote are used to approximate a plurality of maximum power points, and the slopes of the first power asymptote and the second power asymptote are not the same and correspond to different illumination ranges.

The invention proposes an analogous maximum power tracking circuit, which is suitable for use in a solar power generation device. The analog-type maximum power tracking circuit includes a switch, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a comparator, and a unity gain inverting amplifier. The switch has a first end, a second end, and a third end. The first resistor is coupled between the first voltage and the first end, wherein the first voltage corresponds to an output current of the solar cell. The second resistor is coupled between the reference voltage and the first end. The third resistor is coupled between the first voltage and the second end. The fourth resistor is coupled between the reference voltage and the second end. a comparator is coupled to the switch to compare the second voltage and the crossover voltage of the first power asymptote with the second power asymptote, and control the third end to be coupled to the first end or according to the comparison result The second end, wherein the second voltage corresponds to an output voltage of the solar cell. The operational amplifier has a first input end, a second input end, and an output end. The first input end is coupled to the third end, and the second input end is coupled to the ground voltage. The fifth resistor is coupled between the first input end and the output end. A unity gain inverting amplifier is coupled to the output to output a maximum power voltage. The first power asymptote is obtained by the values of the first resistor, the second resistor, the fifth resistor, the first voltage, and the reference voltage, and the third resistor, the fourth resistor, the fifth resistor, and the first The value of the voltage and the reference voltage can be used to obtain a second power asymptote. The resistance of the first resistor is different from the resistance of the third resistor. The first power asymptote and the second power asymptote correspond to different illumination ranges. .

In an embodiment of the present invention, the first power asymptote may be a‧V _IPV +b, and a=R5/R1, b=Vref×R5/R2, where R1 is the resistance value of the first resistor, and R2 is The resistance value of the second resistor, R5 is the resistance value of the fifth resistor, V _IPV is the first detection voltage, and Vref is the reference voltage.

In an embodiment of the present invention, the second power asymptote may be c‧V _IPV +d, and c=R5/R3, d=Vref×R5/R4, where R3 is the resistance value of the third resistor, and R4 is The resistance value of the fourth resistor, R5 is the resistance value of the fifth resistor, V _IPV is the first detection voltage, and Vref is the reference voltage.

In an embodiment of the present invention, the analog-type maximum power tracking circuit may further include a voltage compensation unit coupled to the output of the unity gain inverting amplifier for outputting after temperature compensation of the maximum power voltage.

In an embodiment of the invention, the voltage compensation unit includes an adder to sum the maximum power voltage and the temperature compensation voltage output by the unity gain inversion amplifier, wherein when the operating temperature of the solar cell is increased, the temperature compensation voltage is negative. Voltage, when the operating temperature of the solar cell is reduced, the temperature compensation voltage is a positive voltage.

In an embodiment of the invention, the illuminance range corresponding to the first power asymptote is lower than the illuminance range corresponding to the second power asymptote.

In an embodiment of the invention, the third end is preset to be coupled to the first end.

In an embodiment of the invention, the open relationship is an analog switch.

In an embodiment of the invention, the first power asymptote line corresponds to the plurality of first maximum power points and the second maximum power point of the maximum power points, and the second power asymptote line corresponds to the maximum power points. The second maximum power point and the plurality of third maximum power points, the illuminance ranges corresponding to the first maximum power points are different from the illuminance ranges corresponding to the third maximum power points.

Based on the above description, the solar power generation device and the analogous maximum power tracking circuit of the embodiments of the present invention approximate a plurality of first power asymptotes and second power asymptotes corresponding to different illumination ranges and different slopes. The maximum power point, and according to the maximum power voltage generated by the first power asymptote and the second power asymptote, to reduce the power loss caused by the difference between the maximum power voltage and the corresponding maximum power point, and through analog operation To increase the speed of finding the maximum power voltage.

The above described features and advantages of the present invention will be more apparent from the following description.

FIG. 5 is a schematic diagram showing the correspondence between output power and output voltage and power asymptote of a solar cell under different illumination levels according to an embodiment of the invention. Referring to FIG. 5, in the embodiment, the output voltages of the solar cells and the characteristic lines 501-520 of the output current respectively have different illuminances, and the illuminances corresponding to the characteristic lines 501-520 respectively are from low to high. Further, assuming that the illuminance range of the solar cell is 0 to 1000 W/m ² , the illuminance corresponding to the characteristic line 501 is about 50 W/m ² , and the illuminance corresponding to the characteristic line 502 is about 100 W/m ² , and the rest is And so on, and the illuminance corresponding to the feature line 520 is about the maximum illuminance (ie, 1000 W/m ² ).

Each of the characteristic lines 501-520 has a maximum power point MPP, and the maximum power point MPP is a product of a corresponding output voltage and a corresponding output current being a maximum value on a corresponding characteristic line (eg, 501 to 520). In general, the technical manual of the solar cell provides at least the short-circuit current Isc of the solar cell, the open circuit current Voc, the optimum voltage Vopt, and the optimal current Iopt, wherein the optimum voltage Vopt and the optimal current Iopt are respectively corresponding to the maximum illuminance. The output voltage corresponding to the maximum power point MPP on the line (ie 520) and the corresponding output current. Moreover, the characteristic lines 501 to 520 of the output voltage and the output current of the solar cell can be obtained by calculating the short-circuit current Isc, the open circuit current Voc, the optimum voltage Vopt, and the optimum current Iopt provided by the technical manual of the solar cell, but in the present Other embodiments of the invention are not limited thereto.

Since the maximum power point MPP on the characteristic lines 501-520 is not linearly distributed, when approximated by a single power asymptote (such as the power asymptote 410 shown in FIG. 4), the maximum power point MPP of some characteristic lines will leave. The power asymptote is far away, resulting in a large power loss. In accordance with the above, an embodiment of the present invention approximates the maximum power point MPP on feature lines 501-520 with two power asymptotes (i.e., 530 and 540).

According to FIG. 5, the maximum power point MPP of the feature line 506 is the maximum power point MPP distribution turning point of the feature lines 501-520. Therefore, the maximum power point MPP (corresponding to the second maximum power point) of the feature line 506 is used in this embodiment. The demarcation point is calculated by using the maximum power point MPP of the feature lines 501-506 (corresponding to the plurality of first maximum power points and a second maximum power point) to calculate the power asymptote 530 (corresponding to the first power asymptote), using the feature line 506 A power asymptote 540 (corresponding to a second power asymptote) is calculated for the maximum power point MPP of ~520 (corresponding to a second maximum power point and a plurality of third maximum power points). Wherein, the slopes of the power asymptote lines 530 and 540 will be different, and the power asymptote line 530 corresponds to the voltage Vini at the output current=0.

Moreover, since the illuminance range corresponding to the characteristic lines 501 to 505 (ie, 50 to 300 W/m ² ) is lower than the illuminance range corresponding to the characteristic lines 507 to 520 (ie, 400 to 1000 W/m ² ), that is, the characteristic line 501~ The illuminance range corresponding to the maximum power point MPP of the 505 is lower than the illuminance range corresponding to the maximum power point MPP of the characteristic lines 507-520, so the illuminance range corresponding to the power asymptote 530 obtained by the maximum power point MPP of the characteristic lines 501-506 is used. (ie, 50 to 350 W/m ² ) is lower than the illuminance range of the power asymptote 540 (ie, 350 to 1000 W/m ² ) obtained by using the maximum power point MPP of the characteristic lines 506 to 520.

Moreover, the intersection voltage Vx of the power asymptote lines 530 and 540 can be calculated according to the power asymptote lines 530 and 540 to select the power asymptote 530 or 540 using the intersection voltage Vx and the output voltage of the solar cell, and utilize the selected power. The asymptote (such as 530 or 540) takes the maximum power voltage for the down illuminance. Further, in this embodiment, the power asymptote 530 or 540 is selected according to the comparison result of the cross point voltage Vx and the output voltage of the solar cell, and the selected power asymptote (such as 530 or 540) and the output current of the solar cell are utilized. Calculate the maximum power voltage for the lower illuminance. Therefore, since the power asymptote lines 530 and 540 are used to approximate the maximum power point MPP of the characteristic lines 501 to 520, the power consumption caused by the difference between the maximum power voltage and the corresponding maximum power point MPP is reduced, and the analog operation mode is transmitted. To increase the speed of finding the maximum power voltage.

According to the above description, a solar power generation device is proposed correspondingly below. 6 is a schematic diagram of a system of a solar power generating apparatus according to an embodiment of the present invention. Referring to FIG. 5 and FIG. 6 , in the embodiment, the solar power generation device 600 includes a solar cell 610 , a DC-DC conversion circuit 620 , a current detecting unit 630 , a voltage detecting unit 640 , a control unit 650 , and an analog-type maximum power. Tracking circuit 660. The solar cell 610 is configured to provide an output voltage Vpv and an output current Ipv, wherein the output voltage Vpv and the output current Ipv can be referred to FIG. The DC-DC conversion circuit 620 is coupled to the solar cell 610 and receives the pulse width modulation signal PWM for converting the output voltage Vpv and the output current Ipv into the operating voltage Vcc according to the PWM signal PWM.

The current detecting unit 630 is coupled to the solar cell 610 for detecting the output current Ipv to output the first detecting voltage V _IPV , wherein the value of the first detecting voltage V _IPV can be equal to the value of the output current Ipv, such as the output current Ipv For 900 mA, the first detection voltage V _IPV is 900 mV. The voltage detecting unit 640 is coupled to the solar cell 610 for detecting the output voltage Vpv to output a second detecting voltage V _VPV , wherein the second detecting voltage V _VPV can be equal to the output voltage Vpv. The control unit 650 is coupled to the voltage detecting unit 640 and receives the maximum power voltage command Vmp* for generating the pulse width modulation signal PWM, wherein the maximum power voltage command Vmp* is corresponding to the power asymptote 530 or 540. The maximum power voltage of the illuminance, that is, the maximum power voltage command Vmp* can be regarded as the maximum power voltage corresponding to the illuminance. The control unit 650 adjusts the pulse width of the pulse width modulation signal PWM according to the comparison result of the second detection voltage V _VPV and the maximum power voltage command Vmp*, wherein the control unit 650 can adjust by using a proportional integral (PI) control method. Pulse width modulation signal PWM pulse width.

Further, when the second detection voltage V _{VPV is} higher than the maximum power voltage command Vmp*, it means that the DC-to-DC conversion circuit 620 should draw more current from the solar cell 610, thus widening the pulse of the PWM signal PWM. Wave width, such that the output voltage Vpv of the solar cell 610 is lowered to a second detection voltage V _VPV equal to the maximum power voltage command Vmp*, even if the output voltage Vpv of the solar cell 610 is reduced to a maximum power voltage corresponding to the lower illumination; When the detection voltage V _{VPV is} lower than the maximum power voltage command Vmp*, it represents that the DC-to-DC conversion circuit 620 draws too much current from the solar cell 610, thereby narrowing the pulse width of the PWM signal to make the solar energy The output voltage Vpv of the battery 610 is increased until the second detected voltage V _VPV is equal to the maximum power voltage command Vmp*, even if the output voltage Vpv of the solar cell 610 is increased to the maximum power voltage for the lower illuminance.

The analog-type maximum power tracking circuit 660 is coupled to the current detecting unit 630, the voltage detecting unit 640, and the control unit 650 for comparing the cross-point voltage Vx of the second detecting voltage V _VPV with the power asymptote lines 530 and 540. One of the power asymptote lines 530 and 540 is selected, and a maximum power voltage command Vmp* is generated according to the selected power asymptote (such as 530 or 540) and the first detection voltage V _IPV . That is, when the second detection voltage V _{VPV is} less than or equal to the cross-point voltage Vx, the power-asymptotic line 530 selected by the analog-type maximum power tracking circuit 660 and the first detection voltage V _IPV generates a maximum power voltage command Vmp*; When the second detection voltage V _{VPV is} greater than the intersection voltage Vx, the power asymptote 540 selected by the analog maximum power tracking circuit 660 and the first detection voltage V _IPV generates a maximum power voltage command Vmp*.

Moreover, since the value of the first detection voltage V _IPV is set here to be equal to the value of the output current Ipv, the maximum power voltage command Vmp is generated according to the selected power asymptote (such as 530 or 540) and the first detection voltage V _{IPV .} * Equivalent to generate the maximum power voltage command Vmp* based on the selected power asymptote (such as 530 or 540) and the output current Ipv.

7 is a circuit diagram of an analog-like maximum power tracking circuit according to an embodiment of the invention. Referring to FIG. 5, FIG. 6, and FIG. 7, in the embodiment, the analog-type maximum power tracking circuit 660 includes resistors R1 R R5 (corresponding to the first resistor, the second resistor, the third resistor, the fourth resistor, and the fifth, respectively). Resistor), switch SW, comparator (implemented here by operational amplifier OP1), operational amplifier OP2, unity gain inverting amplifier UA, and voltage compensation unit 710. The switch SW has a first end A, a second end B, and a third end C, and is controlled by the voltage of the output end of the operational amplifier OP1 to determine that the third end C is electrically connected to the first end A or the second end B, wherein The embodiment is that the preset third end C is coupled to the first end A, and the switch SW can be an analog switch.

The resistor R1 is coupled between the current detecting unit 630 and the first end A of the switch SW to receive the first detecting voltage V _IPV . The resistor R2 is coupled between the reference voltage Vref and the first end A of the switch SW. The resistor R3 is coupled between the current detecting unit 630 and the second end B of the switch SW to receive the first detecting voltage V _IPV . The resistor R4 is coupled between the reference voltage Vref and the second end B of the switch SW. The reference voltage Vref may be the voltage Vini shown in FIG. 5, but may be any positive voltage value.

The positive input terminal of the operational amplifier OP1 receives the second detection voltage V _VPV , the negative input terminal of the operational amplifier OP1 receives the intersection voltage Vx of the power asymptote lines 530 and 540, and the output end of the operational amplifier OP1 is coupled to the switch SW. The operational amplifier OP1 is configured to compare the second detection voltage V _VPV with the intersection voltage Vx, and when the comparison result indicates that the second detection voltage V _{VPV is} less than or equal to the intersection voltage Vx, the third end C of the control switch SW is coupled. The first end A of the control switch SW is coupled to the second end B when the comparison result indicates that the second detection voltage V _{VPV is} greater than the intersection voltage Vx. Further, when the comparison result indicates that the second detection voltage V _{VPV is} less than or equal to the cross-point voltage Vx, the voltage of the output terminal of the operational amplifier OP1 is at a low level to control the third end C of the switch SW to be coupled to the first Terminal A, when the comparison result indicates that the second detection voltage V _{VPV is} greater than the intersection voltage Vx, the voltage at the output of the operational amplifier OP1 is at a high level to control the third end C of the switch SW to be coupled to the second end B thereof. .

The negative input terminal (corresponding to the first input terminal) of the operational amplifier OP2 is coupled to the third terminal C of the switch SW, and the positive input terminal (corresponding to the second input terminal) of the operational amplifier OP2 is coupled to the ground voltage. The fifth resistor is coupled between the negative input terminal and the output terminal of the operational amplifier OP2. The unity gain inverting amplifier UA is coupled to the output of the operational amplifier OP2 for outputting the maximum power voltage command Vmp without temperature compensation. The voltage compensation unit 710 is coupled to the output end of the unity gain inverting amplifier UA for temperature compensation of the temperature-compensated maximum power voltage command Vmp and outputs a maximum power voltage command Vmp*.

In this embodiment, the resistors R1, R2, R5, the first detection voltage V _IPV and the reference voltage Vref are used to form a first power asymptote 530, resistors R3, R4, R5, a first detection voltage V _IPV and a reference. Voltage Vref is formed for a second power asymptote 540. Further, assuming that the equation of the first power asymptote 530 is a‧Ipv+b, since the value of the first detection voltage V _IPV is set equal to the value of the output current Ipv, the equation of the first power asymptote 530 can be replaced. For a‧V _IPV +b. Wherein, a=R5/R1, b=Vref×R5/R2, wherein R1 is a resistance value of the first resistor, R2 is a resistance value of the second resistor, and R5 is a resistance value of the fifth resistor, and the V _IPV is The voltage value of the first detection voltage V _IPV , and the above Vref is the voltage value of the reference voltage Vref. Similarly, assuming the second power asymptote is c‧Ipv+d, it can be replaced by c‧V _IPV +d. Wherein, c=R5/R3, d=Vref×R5/R4, wherein R3 is a resistance value of the third resistor, R4 is a resistance value of the fourth resistor, and R5 is a resistance value of the fifth resistor, and the V _IPV is The voltage value of the first detection voltage V _IPV , and the above Vref is a voltage value of the reference voltage Vref.

As shown in FIG. 5, the slope of the power asymptote 530 will be different from the slope of the power asymptote 540, that is, the above a will be different from c, so the resistance of the resistor R1 will be different from the resistance of the resistor R3.

In the present embodiment, the voltage compensating unit 710 includes an adder 711 for summing the uncompensated maximum power voltage Vmp and the temperature compensating voltage V _T output by the unity gain inverting amplifier UA, wherein the temperature compensating voltage V _{T is} reversed. When the operating temperature of the solar cell 610, that is, the operating temperature of the solar cell 610 increases, the temperature compensation voltage V _T is a negative voltage, and when the operating temperature of the solar cell 610 decreases, the temperature compensation voltage V _T is a positive voltage. The temperature compensation voltage V _T can be obtained according to the content of the technical manual of the solar cell.

According to Table 1, the effect of approximating the maximum power point MPP of the feature lines 501-520 with the power asymptotes 530 and 540 is better than approximating the maximum power point of the feature lines 501-520 by a linear approximation. The effect of the MPP, that is, the power consumption of the embodiment of the present invention, is lower than the linear approximation.

In addition, in the above embodiment, the value of the first detection voltage V _IPV is equal to the value of the output current IpV, and the second detection voltage V _VPV is equal to the output voltage Vpv, that is, the first detection voltage output by the current detecting unit 630. The value of V _IPV is 1 times the value of the output current Ipv, and the value of the second detection voltage V _VPV output by the voltage detecting unit 640 is 1 times the value of the output voltage Vpv. However, in other embodiments, the voltage value output by the current detecting unit 630 can be k times the value of the output current Ipv (that is, k times the first detecting voltage V _IPV ), and the voltage value output by the voltage detecting unit 640. It can be k times the value of the output voltage Vpv (that is, k times the second detection voltage V _VPV ), and the analog-type maximum power tracking circuit 660 receives k times the cross-point voltage Vx, so that the analogy maximum power tracking Circuit 660 outputs k times the maximum power voltage Vmp*, where k is an arbitrary number.

Moreover, in the above embodiment, the maximum power point MPP of the feature lines 501-520 is approximated by the power asymptote lines 530 and 540. However, in other embodiments, more than three power asymptotes may be used to approximate the feature line 501. The maximum power point MPP of ~520, for example, the power point MPP of the characteristic lines 501-506 is approximated by two power asymptotes, and is not limited thereto.

In summary, the solar power generation device and the analog-type maximum power tracking circuit of the embodiments of the present invention use two power asymptotes corresponding to different illumination ranges to approximate multiple maximum power points of different illumination levels to reduce the maximum power. The power loss caused by the difference between the voltage and the corresponding maximum power point, and the speed of finding the maximum power voltage through the analog operation mode. Also, the maximum power voltage is temperature compensated to increase the accuracy of the maximum power voltage.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

410, 530, 540. . . Power approximation line

501~520. . . Characteristic line

600. . . Solar power plant

610. . . Solar battery

620. . . DC to DC conversion circuit

630. . . Current detection unit

640. . . Voltage detection unit

650. . . control unit

660. . . Analogous maximum power tracking circuit

710. . . Voltage compensation unit

711. . . Adder

A. . . First end

B. . . Second end

C. . . Third end

Iopt. . . Optimum current

Ipv. . . Output current

Isc. . . Short circuit current

MPP. . . Maximum power point

OP1, OP2. . . Operational Amplifier

Pmax. . . Maximum power

PWM. . . Pulse width modulation signal

R1~R5. . . resistance

SW. . . switch

UA. . . Unity gain inverting amplifier

Vcc. . . Operating voltage

V _IPV . . . First detection voltage

Vmax. . . Maximum power point voltage

Vmp. . . Maximum power voltage command without temperature compensation

Vmp*. . . Maximum power voltage command

Voc. . . Open circuit current

VOP, Vini. . . Voltage

Vopt. . . Optimum voltage

Vpv. . . The output voltage

Vref. . . Reference voltage

V _T . . . Temperature compensation voltage

V _VPV . . . Second detection voltage

Vx. . . Crosspoint voltage

FIG. 1 is a schematic diagram showing changes in illumination intensity corresponding to output power and output voltage of a solar cell.

Figure 2 is a schematic diagram of the operation of the incremental conductance method.

Figure 3 is a schematic diagram of the operation of the constant voltage control method.

Figure 4 is a schematic diagram of the operation of the linear approximation.

FIG. 5 is a schematic diagram showing the correspondence between output current and output voltage and power asymptote of a solar cell under different illumination levels according to an embodiment of the invention.

6 is a schematic diagram of a system of a solar power generating apparatus according to an embodiment of the present invention.

7 is a circuit diagram of an analog-like maximum power tracking circuit according to an embodiment of the invention.

660. . . Analogous maximum power tracking circuit

710. . . Voltage compensation unit

711. . . Adder

A. . . First end

B. . . Second end

C. . . Third end

OP1, OP2. . . Operational Amplifier

R1~R5. . . resistance

SW. . . switch

UA. . . Unity gain inverting amplifier

V _IPV . . . First detection voltage

Vmp. . . Maximum power voltage command without temperature compensation

Vmp*. . . Maximum power voltage command

Vref. . . Reference voltage

V _T . . . Temperature compensation voltage

V _VPV . . . Second detection voltage

Vx. . . Crosspoint voltage

Claims (10)

An analog-type maximum power tracking circuit is applicable to a solar power generation device, comprising: a switch having a first end, a second end and a third end; and a first resistor coupled to the first Between a voltage and the first end, wherein the first voltage corresponds to an output current of a solar cell; a second resistor is coupled between a reference voltage and the first end; a third resistor, The first resistor is coupled between the first voltage and the second end; a fourth resistor is coupled between the reference voltage and the second end; a comparator coupled to the switch Comparing a second voltage and a first power asymptote with a crossover voltage of a second power asymptote, and controlling the third end to be coupled to the first end or the second according to the comparison result The second voltage corresponds to an output voltage of the solar cell; an operational amplifier having a first input end, a second input end, and an output end, the first input end being coupled to the a third end, the second input is coupled to a ground voltage a fifth resistor coupled between the first input terminal and the output terminal; and a unity gain inversion amplifier coupled to the output terminal to output a maximum power voltage; wherein The first power asymptote is obtained by determining a value of the first resistor, the second resistor, the fifth resistor, the first voltage, and the reference voltage, and the third resistor, the fourth resistor, and the fifth And determining, by the resistance, the first voltage and the value of the reference voltage, the second power asymptote, the resistance of the first resistor is different from the resistance of the third resistor, and the first power asymptote and The second power asymptote line corresponds to different illumination ranges. The analogy maximum power tracking circuit according to claim 1, wherein the first power asymptote is a‧V _IPV +b, and a=R5/R1, b=Vref×R5/R2, wherein R1 For the resistance value of the first resistor, R2 is the resistance value of the second resistor, R5 is the resistance value of the fifth resistor, V _{IPV is} the first voltage, and Vref is the reference voltage. The analogy maximum power tracking circuit according to claim 1, wherein the second power asymptote is c‧V _IPV +d, and c=R5/R3, d=Vref×R5/R4, wherein R3 For the resistance value of the third resistor, R4 is the resistance value of the fourth resistor, R5 is the resistance value of the fifth resistor, V _{IPV is} the first voltage, and Vref is the reference voltage. The analogy maximum power tracking circuit of claim 1, further comprising a voltage compensation unit coupled to the output of the unity gain inverting amplifier for temperature compensation of the maximum power voltage. The analogy maximum power tracking circuit of claim 4, wherein the voltage compensation unit comprises an adder to calculate a sum of the maximum power voltage and a temperature compensation voltage output by the unity gain inverting amplifier, wherein When the operating temperature of the solar cell is increased, the temperature compensation voltage is a negative voltage, and when the operating temperature of the solar cell is decreased, the compensation voltage is a positive voltage. The analogy maximum power tracking circuit of claim 1, wherein the first power asymptote line corresponds to a plurality of first maximum power points and a second maximum power point, and the second power asymptote system Corresponding to the second maximum power point and the plurality of third maximum power points, the illuminance ranges corresponding to the first maximum power points are different from the illuminance ranges corresponding to the third maximum power points. The analogy maximum power tracking circuit according to claim 1, wherein the illumination range corresponding to the first power asymptote is lower than the illumination range corresponding to the second power asymptote. An analog-type maximum power tracking circuit is applicable to a solar power generation device, comprising: an analog switch having a first end, a second end and a third end; and a first resistor coupled to the first resistor Between the first voltage and the first end, wherein the first voltage corresponds to an output current of a solar cell; a second resistor is coupled between a reference voltage and the first end; a third resistor The first resistor is coupled between the first voltage and the second end; a fourth resistor coupled between the reference voltage and the second end; a comparator coupled to the analogy a switch to compare a second voltage and a first power asymptote with a crossover voltage of a second power asymptote, and control the third end to be coupled to the first end or according to the comparison result a second end, wherein the second voltage corresponds to an output voltage of the solar cell; an operational amplifier having a first input end, a second input end, and an output end, the first input end being coupled Up to the third end, the second input end is coupled to the first a ground voltage; a fifth resistor coupled between the first input terminal and the output terminal; and a unity gain inverting amplifier coupled to the output terminal to output a maximum power voltage; And determining, by the first resistor, the second resistor, the fifth resistor, the first voltage, and the reference voltage, the first power asymptote, and the third resistor, the fourth resistor, And determining, by the fifth resistor, the first voltage, and the reference voltage, the second power asymptote, the resistance of the first resistor is different from the resistance of the third resistor, and the first power The asymptote and the second power asymptote correspond to different illumination ranges. A solar power generation device comprising: a solar cell for providing an output voltage and an output current; a DC-to-DC conversion circuit coupled to the solar cell and receiving a pulse width modulation signal to Converting the output voltage and the output current into an operating voltage according to the pulse width modulation signal; a current detecting unit coupled to the solar cell to detect the output current and output a first detection a voltage detecting unit coupled to the solar cell to detect the output voltage and output a second detecting voltage; a control unit coupled to the voltage detecting unit to receive a voltage a maximum power voltage, generating the pulse width modulation signal, and adjusting a pulse width of the pulse width modulation signal according to a comparison result of the second detection voltage and the maximum power voltage; and The analogous maximum power tracking circuit of any of the above. A solar power generation device comprising: a solar cell for providing an output voltage and an output current; a DC-to-DC conversion circuit coupled to the solar cell and receiving a pulse width modulation signal to Converting the output voltage and the output current into an operating voltage according to the pulse width modulation signal; a current detecting unit coupled to the solar cell to detect the output current and output a first detection a voltage detecting unit coupled to the solar cell to detect the output voltage and output a second detecting voltage; a control unit coupled to the voltage detecting unit to receive a voltage a maximum power voltage, generating the pulse width modulation signal, and adjusting a pulse width of the pulse width modulation signal according to a comparison result of the second detection voltage and the maximum power voltage; and a analogous maximum power tracking circuit Is coupled to the current detecting unit, the voltage detecting unit and the control unit, according to the second detecting voltage and a first power asymptote and a second power asymptote Comparing a cross-point voltage to select one of the first power asymptote and the second power asymptote, and depending on the selected first power asymptote or the second power asymptote and the Detecting a voltage to generate the maximum power voltage, wherein the first power asymptote and the second power asymptote are used to approximate a plurality of maximum power points, the first power asymptote and the second power asymptote The slopes are not the same and correspond to different illumination ranges.