JP3011605B2 - Operation control method for photovoltaic power generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the operation of a photovoltaic power generation system in which an operating point of a solar cell follows a maximum power point. The present invention relates to an operation control method of a photovoltaic power generation device capable of performing parallel operation.

[0002]

2. Description of the Related Art A solar cell used in a photovoltaic power generator has a voltage-current characteristic (broken line) as shown in FIG.
Has power characteristics (solid line). As you can see from the figure,
Both power and current tend to increase as the amount of solar radiation increases. In the figure, P1, P2, and P3 indicate maximum power points, and Q1, Q
2. Q3 is a point that gives the voltage and current at the time of maximum power output.

As an operation control for efficiently extracting maximum power from a solar cell having such characteristics, a maximum power point tracking method (PPT control) for causing an operating point of the solar cell to follow the maximum power point, a so-called hill-climbing method. Used.

In this method, a solar cell is operated at two different points, and the output power is compared to control the operating point of the solar cell to be the maximum output point. That is, the voltage command value that is the control target value of the operating voltage of the solar cell is minutely changed at an appropriate cycle, and the increase or decrease of the output power of the solar cell in that case is determined. The operating point of the solar cell is optimized stepwise by changing (for example, increasing) the voltage command value in the direction, and changing (for example, decreasing) the voltage command value in the direction opposite to the previous direction if it is decreasing. Point (maximum power point).

In such PPT control, as shown in FIG. 6, the change width ΔV (absolute value of the change amount) of the voltage command value is determined according to the case where the operating point of the solar cell is far from Pmax. If the operating point is increased and decreased as the operating point approaches the optimal operating point Pmax, the operating point can be quickly brought close to the optimal operating point Pmax at the time of starting the inverter, and the operating point is near the optimal operating point Pmax. The fluctuation of the output power at the time can be suppressed. In other words, shortening the time required for transition from operation start to steady operation,
In addition, it is possible to effectively use the generated power during the steady operation. However, the output characteristics (IV characteristics) of the solar cell
Depends on the amount of solar radiation and the like, and the actual optimum operating point Pmax changes every moment.

Therefore, conventionally, the optimum operating voltage of the solar cell under a specific condition is defined as a reference voltage (virtual optimum operating voltage V).
sp), and the operating point at the virtual optimum operating voltage Vsp is set as the optimum operating point Pmax, and the value of the variation width ΔV of the voltage command value is set. Then, based on the actually measured value Vs of the output voltage of the solar cell and the change width ΔV of the voltage command value, the current command value Iamp that regulates the output current of the inverter that changes the DC output of the solar cell to the AC output is increased or decreased. I was letting it go.

[0007]

However, in the photovoltaic power generator, the amount of solar radiation changes considerably sharply due to the movement of clouds, and the output voltage of the solar cell may fluctuate greatly.

For this reason, when a large-capacity photovoltaic power generator is connected to a commercial power system, and the weather in the connection area is, for example, a lot of clouds and a clear view is seen in the place, the solar radiation may occur. Immediately after the inverter output suddenly rises due to the rapid increase in the amount, the inverter output may suddenly fall due to the rapid decrease in the amount of solar radiation caused by the cloud, and the supply power fluctuation due to the decrease in the inverter output at this time is large As a result, the commercial power system side cannot immediately follow the system, and there is a possibility that the system will be temporarily short-circuited and the system voltage will be reduced.

[0009] Further, when the inverter output sharply rises due to a rapid rise in the amount of solar radiation, a sudden increase in system voltage is caused, which may adversely affect equipment connected to the system. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and enables the operating point of the solar cell to quickly follow the maximum power point, and the interconnection in a weather condition in which the solar radiation condition fluctuates greatly. Provided is an operation control method for a photovoltaic power generation device that prevents disturbance at a point such as system voltage.

[0011]

According to the present invention, a control target value for controlling an operating point of a solar cell is increased or decreased in accordance with a difference between a measured value of an output voltage of the solar cell and a virtual optimum operating voltage. In the variation range of the value, while changing in a predetermined cycle, and when the output voltage of the solar cell sharply rises, regardless of the difference, the variation range is set to a small value for a certain period of time, It is an operation control method.

The output voltage of the solar cell may be used as a control target value for controlling the operating point of the solar cell.

[0013]

According to the present invention, the range of change of the operating point for maximum power tracking of the solar cell is increased or decreased according to the difference between the measured value of the output voltage of the solar cell and the virtual optimal operating voltage.
At the time of steady operation, the operating point of the solar cell quickly and periodically fluctuates within a range including the optimal operating point located near the virtual optimal operating point.

Further, when the solar radiation condition fluctuates greatly and the output voltage of the solar cell suddenly rises, the operating point changes regardless of the difference between the measured value of the output voltage of the solar cell and the virtual optimum operating voltage. Is set to a small value for a certain period, so that the output supplied from the solar cell does not rise sharply.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a method for controlling the operation of a photovoltaic power generator according to the present invention. FIG.
It is a block diagram showing the whole solar power generation device 1 composition of the present invention.

As shown in FIG. 1, a solar power generation device 1 includes a solar cell 2 and a connection inverter device 3 for converting a DC output of the solar cell 2 into an AC output and supplying a predetermined AC output. It is connected to the commercial power system 4 via a protection relay (not shown). A load 6 such as various home appliances is connected to the distribution line 5.

Next, the configuration of the interconnection inverter device 3 will be described. In FIG. 1, reference numeral 11 denotes an inverter circuit including a plurality of switching elements and the like, 12 denotes a main control unit constituted by a one-chip microcomputer, 13 denotes an inverter output control unit constituted by a digital signal processor (DSP), and 14 denotes The first voltage detecting means 15 for detecting the output voltage Vo of the inverter circuit 11 is constituted by a transformer PT1, and the first voltage detecting means 15 is constituted by a current transformer CT1.
The first current detecting means 16 for detecting the output current Io of the first unit 16 is constituted by a transformer PT2, the second voltage detecting means for detecting the output voltage Vs of the solar cell 2, and the first unit 17 is constituted by a current transformer CT2. It is a second current detecting means for detecting the output current Is of the battery 2.

Reference numeral 18 denotes an A / D converter for converting the detection voltage Vo ', the detection current Io', the detection voltage Vs ', and the detection current Is' into digital signals, respectively. Reference numeral 19 denotes an A / D converter which is generated by an inverter output control unit 13 described later. The gate circuit sends the pulse width modulation signal (PWM signal) to the drive circuit 20 that drives and controls the switching element.

Numeral 21 receives the digitally converted detection values Vo 'and Io' of the first voltage detecting means 14 and the first current detecting means 15, and inputs an effective value, a maximum value, a frequency of the inverter voltage,
Output state calculating means for calculating an effective value, a maximum value, a frequency of the inverter current, a voltage thereof, and a phase difference between the currents.

Reference numeral 22 denotes the effective value, frequency, and the like of each of the inverter voltage and current calculated by the output state calculation means 21.
And the phase difference between the voltage and the current, and the second voltage detecting means 1
6, the digitally converted detection value Vs 'and the digitally converted detection value Is' of the second current detecting means 17 are input,
This is a failure determination unit that detects occurrence of an abnormality in the solar battery 2 and the commercial power system 4. In this failure determination means 22,
Abnormal voltage or abnormal current on the output side of the inverter circuit 11;
In addition to detecting whether a frequency abnormality or a synchronizing power factor abnormality with the system has occurred, it also detects whether a voltage abnormality or a current abnormality has occurred on the solar cell 2 side.

Reference numeral 23 denotes the input of the effective values of the inverter voltage and current calculated by the output state calculation means 21 and the digitally converted detection value Vs' of the second voltage detection means 16, and the current amplitude of the inverter current Io. It is a current amplitude command value calculation means for generating a command value Iamp.

In the current amplitude command value calculation means 23, 0.5
The power change amount ΔP is calculated based on the power calculated based on the effective voltage value and the effective current value from the output state calculation means 21 read out in the second cycle, and the second power change amount is calculated at the same timing.
The detection value Vs' from the voltage detection means 16 is read, and as described later, the solar cell 1 is detected based on the sign of the power change amount ΔP.
The direction of change of the voltage command value, which is the control target value of the operating voltage of the operation voltage, is determined, and the change width ΔV of the voltage command value
(In the present embodiment, it is set in the range of 0.7 V to 15 V). Then, based on the detected value Vs ′ and the variation width ΔV of the voltage command value, the inverter current Io
Is calculated.

As shown in FIG. 2, the current amplitude command value calculating means 23 calculates a change width Δ with respect to the actually measured solar cell voltage Vs when the virtual optimum operating voltage Vsp is 200 V.
V data is stored in advance, and when Vs = 200 V, the variation width ΔV = 0.7 V, Vs <180 V, or Vs> 2
At 20V, the change width ΔV = 15V, 180V <Vs <
When 200 V or 200 V <Vs <220 V, the variation width ΔV is set to gradually increase from 0.7 V to 15 V as Vs moves away from the virtual optimum operating voltage Vsp.

Then, the main control unit 12 controls the failure determination means 2
2. When the output of the current amplitude command value calculation means 23 is input and the failure determination means 22 determines that the system is abnormal or the solar cell is abnormal, a gate block signal is output to the gate circuit 19 and the interconnection is performed. Inverter device 3
From the commercial power system 4 to the disconnection switch 7. The main controller 12 sends the current amplitude command value Iamp calculated by the current amplitude command value calculator 23 to the inverter output controller 13.

Next, the configuration of the inverter output control unit 13 will be described in more detail. FIG. 3 is a block diagram showing a configuration of the inverter output control unit 13. In FIG.
Reference numeral 131 denotes a band-pass filter processing unit that receives the digitally converted detection value Vo ′ of the first voltage detection unit 14 and extracts a fundamental frequency component (60 Hz in this embodiment) of the interconnection point voltage. And the main control unit 12
, And a current command value signal Sb, which is a product of the current amplitude command value Iamp from the control unit and the interconnection point voltage waveform signal Sa from the band-pass filter processing unit 131.

Reference numeral 133 denotes an error amplifier processing section, which is a current obtained by multiplying a deviation eI between the current command value signal Sb and the digitally converted detection value Io 'of the first current detection means 15 by an amplification factor A. An error signal E is output.

Reference numeral 134 denotes a PWM generator which outputs a pulse width modulation signal (PWM signal) based on the current error signal E from the error amplifier processing unit 133. Specifically, the PWM generator 134 stores the current error signal E and the current error signal E in advance. The PWM signal which is a switching control signal to the switching element of the inverter circuit 11 is supplied to the gate circuit 19 so that the current error signal E becomes zero by comparing the reference triangular wave signal.

Next, the operation control of the photovoltaic power generator 1 configured as described above will be described with reference to the flowchart of FIG. First, the current amplitude command value Iamp is set to 2 A as a start-up process, switching control of the inverter circuit 11 is performed, and the previous inverter power P0 and the previous solar cell voltage Vs0 are set to zero as initial values (S1). ).

Next, in the current amplitude command value calculating means 23, based on the detected voltage Vo 'from the first voltage detecting means 14 and the detected current Io' from the first current detecting means 15, the current inverter output power P1 is calculated. And its power change amount ΔP (= P1
-P0) is calculated (S3).

Then, the current amplitude command value calculating means 23 calculates the sign of the power change amount ΔP and the second voltage detecting means 16.
Then, the change direction and the change width ΔV of the solar cell voltage are determined based on the solar cell voltage Vs calculated from the detected voltage Vs ′, and the current amplitude command value Iamp is calculated based on the result (S5).

Next, switching control of the inverter circuit 11 is performed based on the current amplitude command value Iamp (S
7) Substitute P1 for P0 and Vs for Vs0 (S
9).

In the next step S11, it is determined whether or not 0.5 seconds have elapsed.
3 and the solar cell voltage V from the second voltage detector 16
Read s.

Then, it is determined whether or not the difference between the current solar cell voltage Vs and the previous solar cell voltage Vs0 is equal to or larger than a predetermined range (in this embodiment, set to 20 V which is 10% of the rated voltage) (S15). In the case of YES, that is, when it is determined that the amount of solar radiation has rapidly increased, the process proceeds to step S17,
If NO, the process returns to step S3.

In step S17, the mode is set to the solar radiation rapid rise mode, the variation width ΔV of the solar cell voltage is set to the minimum value of 0.7V, and the variation width ΔV is input to the current amplitude command value calculation means 23.

In the next step S19, the current amplitude command value calculating means 23 determines the current current based on the detected voltage Vo 'from the first voltage detecting means 14 and the detected current Io' from the first current detecting means 15. The inverter output power P1 and its power change amount ΔP (= P1−P0) are calculated, and the process proceeds to step S21.

In step S21, the current amplitude command value calculation means 23 determines the direction of change of the solar cell voltage based on the sign of the power change amount ΔP.
s, current amplitude command value Iamp based on ΔV (= 0.7V)
Is calculated.

Then, in the next step S23, switching control of the inverter circuit 11 is performed based on the current amplitude command value Iamp, and the process proceeds to step S25. In step S25, it is determined whether or not 30 seconds have elapsed since the setting of the solar radiation rapid increase mode.
9 and in the case of NO, the process proceeds to step S27.

In step S27, P1 is set to Vs0 as P0.
Is substituted for Vs, and the process proceeds to the next step S29. In the step S29, it is determined whether or not 0.5 seconds have elapsed, and after the elapse, the process returns to the step S19.

By repeating the above-described routine, the operating point of the solar cell 2 is moved in a direction in which the inverter output power P increases, and eventually swings right and left around the maximum power point. When the solar radiation amount rises rapidly, the inverter output does not rise rapidly but rises gradually.

In the above embodiment, the case where the virtual optimum operating voltage Vsp of the solar cell is fixed in advance has been described. In addition to this, the average value of the solar cell voltage Vs is calculated at regular intervals, and the virtual optimum operating voltage Vsp is calculated. The optimum operating voltage may be replaced with the average value.

In the above embodiment, the inverter circuit 1
Although the case where the operating point of the solar cell 1 is changed so that the output power of the solar cell 1 increases is described above, the operating point of the solar cell 1 is changed so that the output power of the solar cell 1 increases. It does not matter.

[0042]

As described above, according to the present invention, the range of change of the operating point for maximum power tracking of the solar cell is determined according to the difference between the actually measured value of the output voltage of the solar cell and the virtual optimum operating voltage. Since the operating point is increased or decreased, the operating point of the solar cell can be quickly changed to the vicinity of the optimum operating point during the steady operation, and the accuracy and stability of following the optimum operating point can be improved.

When the solar radiation condition fluctuates greatly and the output voltage of the solar cell rises sharply, the operating point changes regardless of the difference between the measured value of the output voltage of the solar cell and the virtual optimum operating voltage. Is set to a small value for a certain period of time, so that the output supplied from the solar cell does not rise sharply, and disturbance such as system voltage at the interconnection point can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a solar power generation device according to the present invention.

FIG. 2 is an explanatory diagram showing the contents of a change width ΔV data stored in a current amplitude command value calculating means.

FIG. 3 is a block diagram illustrating a configuration of an inverter output control unit.

FIG. 4 is a flowchart illustrating the operation control method of the present invention.

FIG. 5 is a voltage-current and voltage-power characteristic diagram of a solar cell when the amount of solar radiation is used as a parameter.

FIG. 6 is an explanatory diagram for describing an outline of maximum power point tracking.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photovoltaic power generator 2 Solar cell 3 Interconnected inverter device 4 Commercial power system 5 Distribution line 6 Load 7 Off switch 11 Inverter circuit 12 Main control unit 13 Inverter output control unit 14 First voltage detection means 15 First current detection means Reference Signs List 16 second voltage detecting means 17 second current detecting means 18 A / D converter 19 gate circuit 20 drive circuit 21 output state calculating means 22 failure determining means 23 current amplitude command value calculating means

Continuation of the front page (72) Inventor Masaaki Konofuji 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. (72) Kuniho Tanaka 2-5-5-1 Keihanhondori, Moriguchi-shi, Osaka No. Sanyo Electric Co., Ltd. (56) References JP-A-60-234468 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05F 1/67 H01L 31/04 H02J 3/38

Claims (2)

(57) [Claims] 1. A solar cell, comprising: a solar cell; and a power converter for converting a DC output generated from the solar cell into an AC output having a predetermined voltage and outputting the AC output. In the photovoltaic power generation device, the control target value for controlling the operating point of the solar cell is a change width of the control target value that increases or decreases according to the difference between the actually measured value of the output voltage of the solar cell and the virtual optimum operating voltage. The operation control of the photovoltaic power generator, wherein the change width is set to a small value for a certain period, regardless of the difference, when the output voltage of the solar cell is rapidly increased while being changed at a predetermined cycle. Method. 2. A method according to claim 1, wherein the control target value is an output voltage of a solar cell.