JPH0956180A - Maximum power follow-up control method for solar generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it controllable to obtain the maximum power by comparing output power values at a particular point in time, and making the output voltage constant and judging the presence or absence of fluctuation in the quantity of isolation by measuring the power after the elapse of a particular time period. SOLUTION: Power Pd of a solar cell system is determined (S13). Then, whether the power Pd measured this time (Δt point in time) is larger than the power Pd-1 measured previously (Δt-1 point in time) is judged (S14). If the result of judgment is YES (Pd>=Pd-1 ), then the power Pd+1 is measured Δt seconds later in a state where the voltage Vd of the solar cell system is maintained constant (S15a). And whether the power Pd+1 measured this time at (Δt+1 ) is equivalent to the power Pd measured previously (Δt) is judged (S16a). If the result of judgment is NO(Pd+1 ≠Pd), then it is apparent that quantity of insulation fluctuates, memory content is changed to Pd=Pd+1 (S15b) thereby returning to S15a, and this is repeated until Pd=Pd+1 occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a maximum power tracking control method for a solar power generation system, and more particularly, in a solar power generation system in which the output of a solar cell system is converted into a predetermined power by a power converter, the amount of solar radiation of the sun The present invention relates to a maximum power tracking control method for a photovoltaic power generation system that can reliably control the maximum power even if fluctuations occur.

[0002]

2. Description of the Related Art A conventional photovoltaic power generation system is constructed, for example, as shown in FIGS. In the figure,
Reference numeral 1 denotes a solar cell system, which is configured by connecting a plurality of solar cell arrays in series or parallel as appropriate. The solar cell system 1 converts the DC power into AC power for example PWM (P ulse W idth M od
It is connected to the DC side of the controlled inverter 2. Further, the AC side (output side) of the inverter 2 is connected to the system power source 4 via the interconnection reactor 3. On the other hand, the output voltage Vd and the output current Id of the solar cell system 1 are the voltage detection means 5 and the current detection means 6, respectively.
Is detected by, and input to the maximum power control means 7, and its output is supplied to the inverter 2 as a Vd setting signal (Vd *).

The maximum power control means 7 described above is, for example, a voltage
Output voltage detected by the detection means 5 and the current detection means 6
A / D conversion means for A / D converting Vd and output current Id
8 and 9 are multiplied by the output signals of the A / D conversion means 8 and 9.
The multiplier 10 and the current measured voltage output from the multiplier 10
Force Pd and previous measured power Pd_-1Storage means 1 for storing and
1, the current measured power Pd and the last measured power Pd_-1And
Based on the comparison means 13 for comparing and the judgment of the comparison means 13.
Up or down to count up or down
Counting means 14 and D / A conversion based on the count signal
D / A conversion means 15 for conversion and output of D / A conversion means 15
Force signal ΔVd and previous Vd setting signal Vd _-1* And add
And an adder 16 that

On the other hand, the above-mentioned Vd setting signal (Vd *) is generated as follows. Output voltage V of solar cell system 1
The d and the output current Id are input to the A / D conversion means 8 and 9, respectively, and are multiplied by the multiplier 10. The current (at Δt) measured power Pd and the last (at Δt ₋₁ ) measured power Pd _{−1 that} have been multiplied are stored in the storage unit 11. This time (△ t
Measurement power Pd and the previous time) (△ t and measuring power Pd _{-1 -1} point) and input to the comparison means 13 compares and judges. The comparison / determination result is counted by the up / down counting means 14 based on the determination of the up direction or the down direction, and is D / A converted by the D / A converting means 15. This D
The output signal ± ΔVd of the A / A conversion means 15 and the previous Vd setting signal (Vd _-1 *) are added by the adder 16 to generate the Vd setting signal (Vd *).

Generally, the solar cell system 1 has a mountain-shaped characteristic as shown in FIG. 6 between its output voltage Vd and output power Pd, and the output voltage Vd is Vd _max and the output power Pd is maximum. It is known that the output power Pd becomes the power Pd _max and the output voltage Vd decreases before and after the power Pd _max . Therefore, in order to operate the system efficiently, the output power Pd of the solar cell system 1 should be as low as possible. It is necessary to control the output voltage Vd _max to maximize the output voltage.

[0006] Thus, in the prior art, generally MPPT method which is referred to as the hill-climbing method (M ax P ower P oi
Output power Pd from the solar cell system 1 by nt T racking method) is constantly controlled to be maximized. This control method will be described below with reference to FIG.

First, the sampling timer is started (step S1). When the sampling timer times out, the output voltage Vd and the output current Id of the solar cell system 1 are detected by the voltage detection means 5 and the current detection means 6, and the data is input to the maximum power control means 7 ( Step S2). Specifically, the output voltage Vd and the output current Id are A / D converted by the A / D conversion means 8 and 9,
The output power Pd of the solar cell system 1 is obtained by multiplication by the multiplier 10 (step S3). Then, it is determined whether the up / down counting means 14 has counted up at the time of the previous sampling (step S4).

If the determination result in step S4 is YES, it is determined whether the output power Pd measured this time (at Δt) is larger than the output power Pd _-1 measured at the previous time (at Δt _-1 ). The determination is made in step 13 (step S5a).
In the case of YES, it is clear that the measured power Pd this time exists on the left side of the mountain shown in FIG.
Up / down counting means 14 so as to increase by Vd
Is counted up (step S6a) and output to the D / A conversion means 15 (step S7). In the case of NO in step S5a, it is clear that the measured power Pd this time has passed the maximum power and moved to the right side of the mountain shown in FIG. 6, so the up / down count is reduced so as to decrease by ΔVd. Count down the means 14 (step S6
b) and output to the D / A conversion means 15 (step S).
7).

On the other hand, the determination result in step S4 is N
In the case of O, the output power P measured this time (at Δt)
It is determined whether or not d is larger than the output power Pd _-1 measured last time (at the time of Δt _-1 ) (step S5b). In the case of YES, since it is clear that the measured power Pd this time exists on the right side of the mountain shown in FIG. 6, the up / down count means 14 counts down so as to decrease by ΔVd (step S6c). And outputs it to the D / A conversion means 15 (step S7). NO in step S5b
In this case, it is clear that the measured power Pd this time has passed the maximum power and moved to the left side of the mountain shown in FIG. 6, so the up / down count means 14 is counted up so as to increase by ΔVd. (Step S6d) D /
It is output to the A conversion means 15 (step S7). And
Vd ± ΔV added by the adder 16 to the inverter 2
The Vd setting signal Vd * of d is supplied, and the process returns to step S1. By executing the above steps, the output power Pd of the solar cell system 1 is always as shown in FIG.
Maximum power P corresponding to Vd _max of the Pd-Vd curve shown in FIG.
It is controlled to be d _max .

[0010]

By the way, according to this maximum power tracking control method, the output voltage Vd is increased or decreased by ΔVd regardless of whether the peak is on the left side or the right side of the Pd-Vd characteristic shown in FIG. The solar power generation system can be operated efficiently because the electric power from the solar cell system 1 is controlled to be always the maximum while comparing the measured electric powers before and after, but the following problems occur. is there.

The above control method can control the solar radiation without any trouble when the solar radiation is constant. For example, as shown in FIG. 8, the peak of the solar radiation is Δt. _-1 ,
A problem occurs when the values increase as shown by curves A, B, and C according to the elapsed time of Δt and Δt ₊₁ . That is, for example, in step S6a, the measured power Pd of this time (Δt) is shown in FIG.
Since it is clear that the measured power Pd exists on the left side of the mountain, the measured power Pd reaches the maximum power Pd _max by ΔV.
The operation increasing by d is repeatedly executed. However, as the amount of solar radiation increases, the Pd-Vd characteristics are changed to curves B and C.
In such a case, there is a region larger than the maximum power Pd _{max of the} curve A on the right side of the curves B and C, so that the measured power Pd passes the original maximum power Pd _max. Instead, the output voltage Vd is continuously increased. Then, when the power Pd on the curve B or C becomes smaller than the original maximum power Pd _max , ΔVd
Is stopped and the system is operated with this power as the maximum power Pd. Therefore, when the amount of solar radiation changes to return to the state of the curve A next time, the system obtains output power smaller than the original maximum power Pd _max (the voltage range higher than the maximum voltage Vd _max). There is a problem that you will be forced to drive inefficiently.

Therefore, an object of the present invention is to provide a photovoltaic power generation system capable of controlling the output voltage of the solar cell system so that the maximum power can be obtained even if the amount of solar radiation changes with a relatively simple structure. It is to provide a maximum power tracking control method.

[0013]

SUMMARY OF THE INVENTION Accordingly, the present invention is, in order to achieve the above object, appropriately changing the output voltage Vd of the solar cell system, △ t _-1 output power measured at point Pd _-1 And the output power Pd measured at the time point of Δt, the maximum power tracking control method for controlling the maximum power output while comparing the magnitude of the output power Pd measured at the time point of Δt _−1. After comparing the magnitudes of the electric power Pd ₋₁ and the output electric power Pd measured at the time point Δt, the output electric power Pd ₊₁ is changed after Δt ₊₁ hour while keeping the output voltage of the solar cell system constant. measured, △ t output power measured at point Pd and △ t ₊₁ output was measured at power Pd ₊₁
It is characterized in that whether or not the amount of solar radiation has changed is determined based on the result of comparison with.

[0014] The second aspect of the present invention is suitably changing the output voltage Vd of the solar cell system, △ t _-1 measured at the output power Pd _-1 △ output power P measured at the time t
In the maximum power follow-up control method of the control to photovoltaic systems as can output the maximum power by comparing the magnitude of the d, wherein △ t _-1 measured at the output power Pd _-1 △ t at time After comparing the magnitude with the measured output power Pd, the output power Pd ₊₁ was measured after Δt ₊₁ hour with the output voltage of the solar cell system kept constant, and
The magnitudes of the output power Pd measured at time t and the output power Pd ₊₁ measured at time Δt ₊₁ are compared. If the respective output powers Pd and Pd ₊₁ are not equal, the memory contents are changed. The output power Pd ₊₁ after the lapse of Δt time is measured again by changing to Pd = Pd ₊₁ and repeated until Pd ₊₁ and Pd become equal, while the output powers Pd ₊₁ and Pd are changed. Is equal to each other, the output voltage Vd is appropriately changed and controlled so that the maximum power can be output.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A solar power generation system according to the present invention is configured as shown in FIGS.
The same parts as those of the conventional example shown in FIGS. 4 to 5 are designated by the same reference numerals, and detailed description thereof will be omitted. In the figure,
The maximum power control means 7 is different. That is, the maximum power control means 7 includes, for example, A / D conversion means 8 and 9, a multiplier 10 that multiplies the output signals of the A / D conversion means 8 and 9, and the previous (Δt ₋₁₎ from the multiplier 10. measurement power Pd _-1 point), this (△ t time) measurement power Pd, △ t ₊₁ and storage means 11 for storing the measured power Pd ₊₁ time, △ measurement at time t power Pd and △ t _{- The first} comparing means 13a for comparing the measured power Pd _-1 at _one time point with the measured power Pd ₊₁ at the time point Δt ₊₁ and the first comparison means 13a.
Output and the second comparing means 13b for comparing the one output (Pd ≧ Pd _-1) comparing means 13a of a △ t ₊₁ time measurements power Pd ₊₁ of the other first comparator means 13a ( Pd <P
d ₋₁ ), one of the third comparing means 13c, one of the second comparing means 13b and the third comparing means 13c (P
Up / down counting means 1 having d = Pd _{+ 1} ) as an input
4, the first rewriting means 12a which receives the other output (Pd ≠ Pd _{+ 1} ) of the second comparing means 13b and the third comparing means 13c, and the output of the up / down counting means 14 The second rewriting means 12b, the D / A converting means 15, and the adder 16 are included.

Next, the method of the present invention will be described with reference to FIG. In the figure, the characteristic part of the present invention is Δt _-1
After comparing the magnitudes of the output power Pd ₋₁ measured at the time point and the output power Pd measured at the time point Δt, the output voltage is output after Δt ₊₁ hour with the output voltage of the solar cell system being kept constant. The power Pd ₊₁ is measured, and it is determined whether or not the amount of solar radiation fluctuates based on the result of comparison between the output power Pd measured at the time point Δt and the output power Pd ₊₁ measured at the time point Δt _+1. .

Based on this feature, the maximum power tracking control method will be specifically described. First, the sampling timer is started (step S11). When the sampling timer times out, the output voltage Vd and the output current Id of the solar cell system 1 are detected by the voltage detecting means 5 and the current detecting means 6, and the data thereof is controlled by the maximum power control means 7.
(Step S12). Specifically, the output voltage Vd and the output current Id are A and D converted by the A / D conversion means 8 and 9.
The output power Pd of the solar cell system 1 is obtained by being / D converted and multiplied by the multiplier 10 (step S13) and stored in the storage means 11. Then, the first comparing means 13a determines whether the output power Pd measured this time (time Δt) is larger than the output power Pd ₋₁ measured last time (time Δt ₋₁ ) (step S14).

The determination result in step S14 is YES.
(Pd ≧ Pd_-1), The output of the solar cell system 1
After Δt seconds (for example, 3 when the force voltage Vd is kept constant)
~ 4 seconds later) output power Pd₊₁Is measured (step S1
5a). And this time (△ t ₊₁) Output power P measured in
d₊₁Is equal to the output power Pd measured last time (Δt)
Is determined by the second comparing means 13b (step S16
a). The determination result is YES (Pd₊₁= Pd),
It is clear that there is no fluctuation in the amount of solar radiation,
Go to step S17a. In addition, NO (Pd₊₁≠ Pd)
It is clear that there is a fluctuation in the amount of solar radiation,
_max The memory contents of the command value are transferred to the first rewriting means 12a.
Pd = Pd₊₁Change to (Step S15b)
Return to step S15a, Pd = Pd₊₁Repeat until.
In step S17a, up at the time of the last sampling
Determines whether the down-counting means 14 has been counted up
I do. If the determination result is YES, the current measured power P
It is clear that d exists on the left side of the mountain shown in FIG.
Since there is, up and down to increase by ΔVd
Count up the counting means 14 (step S18
a) and output to the D / A conversion means 15 (step S1)
9a). When the determination result of step S17a is NO
Shows that the measured power Pd this time has passed the maximum power and is shown in FIG.
It is clear that it has moved to the right side of the mountain, so △
Up / down counting means 14 so as to decrease by Vd
Is counted down (step S18b) and D / A converted.
It is output to the means 15 (step S19a). And the second
Pd by the second rewriting means 12b_-1Memory contents of Pd
₊₁(Step S20a) and returns to step S11
You.

The determination result in step S14 is NO.
If (Pd <Pd ₋₁ ), the output power Pd ₊₁ is measured after Δt seconds while maintaining the output voltage Vd of the solar cell system 1 constant (step S15c). Then, it is determined whether the output power Pd ₊₁ measured this time (Δt ₊₁ ) is equal to the output power Pd measured last time (Δt) by the third comparing means 13.
The determination is made at c (step S16b). The judgment result is YE
In the case of S (Pd = Pd _{+ 1} ), it is clear that there is no change in the solar radiation amount of sunlight, and the process proceeds to step S17b.
Further, in the case of NO (Pd ≠ Pd ₊₁ ), it is clear that the amount of solar radiation varies, and the memory content of the Pd _max command value is set to Pd = Pd ₊₁ by the first rewriting means 12a. Change (step S15d) and return to step S15c, P
Repeat until d = Pd _{+ 1} . In step S17b, it is determined whether the up / down counting means 14 has counted up at the time of the previous sampling. Judgment result is Y
In the case of ES, it is clear that the measured power Pd this time exists on the right side of the mountain shown in FIG.
The up / down counting means 14 is counted down so as to decrease by d (step S18c) and output to the D / A conversion means 15 (step S19b). Step S1
In the case of NO in 7b, it is clear that the measured power Pd this time has passed the maximum power and moved to the left side of the mountain shown in FIG. 6, so the up / down count means is increased by ΔVd. 14 is counted up (step S18d) and output to the D / A conversion means 15 (step S19b). Then, the second rewriting means 12b changes the memory contents of Pd _-1 to Pd ₊₁ (step S20).
b) and returns to step S11. By executing the above steps, the output power Pd of the solar cell system 1
Is always controlled to be the maximum power Pd _max corresponding to Vd _max of the Pd-Vd curve shown in FIG.

[0020]

As described above, according to the present invention, Δt _-1
After comparing the magnitudes of the output power Pd ₋₁ measured at the time point and the output power Pd measured at the time point Δt, the output voltage is output after Δt ₊₁ hour with the output voltage of the solar cell system being kept constant. The electric power Pd ₊₁ is measured, and it is determined whether or not the solar radiation amount fluctuates based on the comparison result of the output power Pd measured at the time point Δt and the output power Pd ₊₁ measured at the time point Δt _+1. Since the MPPT method is used together when there is no change in Vd in the Pd-Vd characteristic of the solar cell system,
_The maximum power Pd _max corresponding to _max can be controlled. Therefore, since only a simple control method is added, an economically excellent control method can be provided.

Especially, after the measured power Pd of this time and the measured power Pd _{-1 of the} previous time are compared and judged, the current voltage (Vd) of the solar cell system is maintained at a constant value and measured after Δt seconds. Output power Pd ₊₁ of Δt ₊₁ ) and the previous time (△
When the output power Pd measured in t) is not equal,
The memory contents of pd _max command value is changed to Pd = Pd _+1, steps are cyclically until Pd = Pd _+1. Therefore, it is possible to minimize the influence of fluctuations in the amount of solar radiation during Pd _max control and improve the efficiency of the system.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.

FIG. 2 is an electric circuit diagram of the present invention.

FIG. 3 is a detailed view of the maximum power control means shown in FIG.

FIG. 4 is an electric circuit diagram of a conventional example.

5 is a detailed view of the maximum power control means shown in FIG.

FIG. 6 is a diagram showing output power-output voltage characteristics of the solar cell system.

FIG. 7 is a flowchart for explaining a conventional maximum power tracking control method.

FIG. 8 is a diagram showing an output power-output voltage characteristic that varies depending on the amount of solar radiation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solar cell system 2 Inverter 4 System power supply 5 Voltage detection means 6 Current detection means 7 Maximum power control means 8, 9 A / D conversion means 10 Multiplier 11 Storage means 12a First rewriting means 12b Second writing Changing means 13a First comparing means 13b Second comparing means 13c Third comparing means 14 Up / down counting means 15 D / A converting means 16 Adder

Claims (2)

[Claims] 1. Output power Pd ₋₁ and Δ measured at Δt ₋₁ by appropriately changing the output voltage Vd of the solar cell system.
In the maximum power tracking control method for a photovoltaic power generation system, which controls so that maximum power can be output while comparing the magnitude with the output power Pd measured at time t, the output power Pd measured at time Δt _{-1 -1} and the magnitude of the output power Pd measured at the time point of Δt are compared, and then the output power Pd ₊₁ is measured after the time of Δt ₊₁ hours while maintaining the output voltage of the solar cell system constant. , A solar power generation system characterized by determining whether or not the amount of solar radiation varies based on the result of comparison between the output power Pd measured at the time point Δt and the output power Pd ₊₁ measured at the time point Δt ₊₁ . Maximum power tracking control method. 2. The output power Pd ₋₁ and Δ measured at Δt ₋₁ by appropriately changing the output voltage Vd of the solar cell system.
In the maximum power tracking control method for a photovoltaic power generation system, which controls so that maximum power can be output while comparing the magnitude with the output power Pd measured at time t, the output power Pd measured at time Δt _{-1 -1} and the magnitude of the output power Pd measured at the time point of Δt are compared, and then the output power Pd ₊₁ is measured after the time of Δt ₊₁ hours while maintaining the output voltage of the solar cell system constant. , The magnitudes of the output power Pd measured at the time point Δt and the output power Pd ₊₁ measured at the time point Δt ₊₁ are compared, and if the respective output powers Pd and Pd ₊₁ are not equal, the memory The content is changed to Pd = Pd _{+ 1,} and the output power Pd _{+ 1} after the lapse of Δt time is measured again, and Pd _{+ 1}
And Pd are repeated until they become equal, while if the output powers Pd _{+ 1} and Pd are equal, the output voltage V
A maximum power follow-up control method for a solar power generation system, which is controlled so that maximum power can be output while appropriately changing d.