JP4457692B2 - Maximum power tracking control method and power conversion device - Google Patents

Maximum power tracking control method and power conversion device Download PDF

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JP4457692B2
JP4457692B2 JP2004046358A JP2004046358A JP4457692B2 JP 4457692 B2 JP4457692 B2 JP 4457692B2 JP 2004046358 A JP2004046358 A JP 2004046358A JP 2004046358 A JP2004046358 A JP 2004046358A JP 4457692 B2 JP4457692 B2 JP 4457692B2
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solar cell
voltage
output power
maximum output
maximum
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JP2005235082A (en
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晃 吉武
博昭 小新
信一郎 岡本
潔 後藤
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パナソニック電工株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy

Description

  The present invention relates to a maximum power tracking control method for maximizing the output of a solar cell that changes its output characteristics depending on the amount of solar radiation, temperature, and the like, and a power converter using the same.

  In a solar inventor using a solar cell as a power source, maximum power tracking control for tracking a maximum output operating point of a solar cell that changes every moment according to solar radiation, temperature, and the like has been conventionally performed (for example, Japanese Patent Laid-Open No. Hei 8). No. 44445).

A conventional maximum power tracking control method will be described with reference to FIG. FIG. 12 is a graph showing characteristics of the operating voltage and output power of a solar cell at a certain amount of solar radiation. Maximum power tracking control is performed by changing the operating voltage of the solar cell and comparing the output power before and after the change. If the operating voltage is changed in the increasing or decreasing direction and the output power increases as a result of the change, the next operating voltage changes in the same direction, and if the output power decreases as a result of the change, the next operating voltage changes The maximum output operating point of the solar cell is detected by repeating the above operation with the direction of reversal. The operation will be specifically described with reference to FIG. When the operating voltage of the solar cell outputting electric power P1 at the operating voltage V1 is changed in the decreasing direction V1 → V2, the output power of the solar cell changes from P1 → P2. Since P1 < P2, the direction in which the operating voltage is changed next is the decreasing direction as V1 → V2. Therefore, the operating voltage is changed from V2 to V3. In the same manner as described above, the output changes from P2 to P3 and P3> P2, so that the next operating voltage changes in the same decreasing direction. If the output power increases in this way, the operation voltage is repeatedly changed in the decreasing direction. When the solar cell outputs electric power P5 operating voltage V5, to the operating voltage for this case is also P5> P4 reduced from V5 to V6. As a result, the output power is P6, and P5> P6. Therefore, the next direction in which the operating voltage is changed is the reverse direction, that is, the increasing direction.

By repeating the above operation, the maximum output operating point of the solar cell is searched, and it is possible to operate near the maximum output operating point by this search. FIG. 13 shows the operation until reaching the maximum output operating point of the solar cell and the operation after reaching the maximum output operating point in time series.
Japanese Patent Application Laid-Open No. 8-44445

  By the way, in the conventional maximum power tracking control method described above, power loss always occurs because the operating voltage is changed near the maximum output operating point. FIG. 14 shows losses that occur near the maximum output operating point, and ΔP54 and ΔP56 in the figure are power losses that occur when the operating voltage is changed near the maximum output operating point. In order to reduce this loss, a method of reducing the change width ΔV of the operating voltage can be considered as a countermeasure. However, if the change width ΔV is small, there is a problem that when the voltage at the maximum output operating point and the current operating voltage are wide, the time required to reach the maximum output operating point becomes long. In addition, since the power change width caused by changing the operating voltage is small, there is a problem that a malfunction occurs in the maximum power tracking control due to the relationship between the accuracy of the current detection circuit and the voltage detection circuit.

  In addition, the following problems occur when the amount of sunlight changes. In other words, in the conventional maximum power tracking control method, the operating voltage is always changed, and the change direction of the next operating voltage is determined by the change in output power before and after the voltage change, so the voltage at the maximum output operating point due to fluctuations in the amount of sunlight. The direction of change of the current and the direction of change of the actual operating voltage are opposite to each other, and a malfunction that the potential difference between the voltage at the maximum output operating point and the actual operating voltage increases can be considered. FIG. 15 shows an example of a malfunction that occurs when the conventional maximum power tracking control method is performed when the amount of solar radiation increases. When the operating voltage is V1 and the output power is P1, and the operating voltage is changed from V1 to V2, if the solar radiation pattern 1 is constant, the operating voltage is V2, the output power is P2 ′, and P1> P2 ′ Therefore, if the solar radiation pattern changes from solar radiation pattern 1 to solar radiation pattern 2 at the same time as changing from V1 to V2, the operating voltage becomes V2 and the output power becomes P2, but P2> Since it is P1, the operating voltage changes in the same direction. That is, the change direction of the operating voltage determined by the maximum power tracking control method is a decreasing direction even though the changing direction of the voltage at the maximum output operating point of the solar cell is an increasing direction. If the above control is repeated during fluctuations in the amount of sunlight, the operating voltage is V1 → V2 → V3, that is, the change direction of the maximum output operating point regardless of the change of the voltage at the maximum output operating point from V1 → Va → Vb. Changes in the opposite direction, and the potential difference increases.

  Also, when the amount of solar radiation is low, such as in the morning and evening, as shown in FIG. 16, there is no potential difference between the inverter stop voltage Vstop and the maximum output operating point voltage Vmax. There is a problem that the inverter stops.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to reduce the loss of output power near the maximum output operating point of the solar cell and improve the utilization efficiency of the solar cell. An object of the present invention is to provide a maximum power tracking control method and a power converter using the same.

In order to achieve the above object, in the invention of the maximum power tracking control method of claim 1, the solar cell is used for solar power generation using an inverter unit as an input power source, and the inverter unit determines the operating voltage of the solar cell. predetermined voltage is varied, the operation voltage to the change in direction and the same direction when the output power by increasing the solar cell by a predetermined voltage change, the operating voltage by reversing the direction of change if reduced output power of the solar cell is In the maximum power tracking control method for detecting the maximum output operating point of the solar cell by repeatedly executing the operation of changing the predetermined voltage , when the operating voltage of the solar cell changes repeatedly at at least three potentials, determining that an operation in the vicinity of the maximum output operation point determination means of the inverter unit, the operation in the vicinity of the maximum output operation point of the solar cell is determined, the thickness The maximized by storing the maximum output power of the battery in the storage means, to set the operation voltage with the maximum output power value stored in the storage means in the central value of the potential is changing in the vicinity of the maximum output operation point The inverter unit is controlled so as to fix the operating voltage as the output power value to the median value, and then the output power value of the solar cell is detected, and the detected output power value and stored in the storage means Until the difference from the maximum output power value becomes equal to or greater than a predetermined value, the control to the inverter unit for fixing the operating voltage at the maximum output power value to the median value is continued .

  According to the invention of the maximum power tracking control method of claim 1, it is possible to operate the solar cell only at the maximum output operating point, and therefore it is possible to reduce the output power loss in the vicinity of the maximum output operating point. The utilization efficiency of the battery can be improved, and the output power of the solar battery can always be utilized to the maximum.

Further, according to according to the invention of the maximum power tracking control method of paragraph 1, only the operating voltage without taking into consideration the output power of the solar cell can be detected maximum output operation point by monitoring, detection of the maximum output operation point Becomes easier.

Furthermore, according to the invention of the maximum power tracking control method of claim 1 , the above-described action can be continued while the amount of solar radiation is constant.

In the invention of the maximum power tracking control method of claim 2 , in the invention of claim 1 , until the change of the output power value of the solar cell to be detected converges when the difference becomes the predetermined value or more. The operating voltage is maintained, and after the convergence, the operating voltage is changed to detect a maximum output operating point.

According to the maximum power tracking control method of claim 2 , when a variation in the amount of sunlight occurs, the variation in the amount of sunlight can be achieved by changing the operating voltage of the solar cell after the variation in the amount of solar radiation has converged. It is possible to prevent the malfunction of the accompanying maximum power antipodal control.

In the invention of the maximum power tracking control method of claim 3 , in the invention of claim 2 , the direction in which the operating voltage is changed after the convergence is the maximum output power stored in the storage means by the output power value of the solar cell after convergence. If it increases with respect to the value, it changes in the direction of voltage increase, and if the output power after convergence decreases with respect to the stored maximum output power, it changes in the direction of voltage decrease.

According to the invention of the maximum power tracking control method of claim 3 , when the fluctuation of the amount of sunshine occurs, the operating voltage of the solar cell is based on the increase or decrease of the amount of sunshine due to the fluctuation of the amount of sunlight after the generated fluctuation of the sunshine converges. By setting the change direction of, it becomes possible to reach the maximum output operating point of the fluctuating solar radiation amount sooner.

In the invention of the maximum power tracking control method according to claim 4, in the invention of any one of claims 1 to 3, the maximum output power maximum output power value memorized is at less than a predetermined value, stored in the storage means If the value is within a certain power fluctuation range, the operating voltage is increased.

According to the invention of the maximum power tracking control method of claim 4 , the solar cell can be operated at a higher voltage from the stop voltage of the inverter part while minimizing the output power loss at the time of low solar radiation.・ Stable operation can be continued even if the amount of solar radiation changes in the evening.

In the invention of the power conversion device of the invention of claim 5 , in the power conversion device including an inverter unit that converts the solar cell into an alternating current using an input power source, the inverter unit changes the operating voltage of the solar cell by a predetermined voltage, and the solar cell If the output power of the solar cell increases, the operating voltage is changed in the predetermined direction in the same direction as the changing direction, and if the output power of the solar cell decreases, the changing direction is reversed to change the operating voltage to the predetermined voltage. By detecting the output power value of the solar cell by repeatedly executing the operation, and when the operating voltage of the solar cell repeatedly changes at least three potentials, near the maximum output operating point of the solar cell determining means for determining that the operation, the operation in the vicinity of the maximum output operation point of the solar cell in said determining means is determined, the maximum output current of the solar cell Storage means for storing a value, the said maximum output power value by setting the operation voltage with the maximum output power value stored in the storage means in the central value of the potential is changing in the vicinity of the maximum output operation point Control means for controlling the inverter unit so as to fix an operating voltage at the median value, the control means comprising: an output power value detected by the detection means; and the maximum output stored in the storage means. Control of the inverter unit for fixing the operating voltage at the maximum output power value to the median value is continued until the difference from the power value becomes a predetermined value or more .

According to the invention of the method for controlling the maximum power of the power converter according to claim 5 , the solar cell can be operated only at the maximum output operating point, and therefore the output power loss near the maximum output operating point can be reduced. As a result, the utilization efficiency of the solar cell can be improved, and the output power of the solar cell can always be maximized.

  In the present invention, when the amount of solar radiation is constant, the solar cell can be operated only at the maximum output operating point, so that it is possible to reduce the output power loss in the vicinity of the maximum output operating point. There is an effect that the utilization efficiency can be improved and the output power of the solar cell can always be utilized to the maximum.

  FIG. 1 shows a configuration of a solar power generation device using a power conversion device configured using the maximum power tracking control method of the present invention. In this device, a solar cell 1, an inverter unit 2, and interconnection protection are shown. The inverter unit 2 converts the DC power from the solar cell 1 into AC power, and the commercial power source AC is connected via the connection protection unit 3.

  The inverter unit 2 includes a DC / DC converter 4 that converts a DC voltage output from the solar cell 1 into a predetermined DC voltage, and a DC / AC that converts the DC voltage output from the DC / DC converter 4 into an AC voltage. The inverter 5, a DC / DC converter drive circuit 61, a DC / AC inverter drive circuit 62, a DC / DC converter control circuit 7, a current control circuit 8, and a microcomputer 9 are included. 9, an operating voltage calculation function 10, a current amplitude calculation function 11, and a phase calculation function 12 are realized by software.

  The current detection transformer CT1 constitutes means for detecting the output current Iin from the solar cell 1, and the voltage detection transformer PT1 constitutes means for detecting the output voltage Vin of the solar cell 1. The detection outputs of both transformers CT1 and PT1 are taken into the operating voltage calculation function 10, and the detection output of the voltage detection transformer PT1 is taken into the current amplitude calculation function 11. The current detection transformer CT2 is for detecting the output current Iout output from the DC / AC inverter 5 to the interconnection protection unit 3, and the detection output is taken into the current control circuit 8, and also for voltage detection. The transformer PT2 detects the output voltage Vout from the DC / AC inverter 5, and the detected output is taken into the phase calculation function 12. Further, the voltage detection transformer PT3 detects the output voltage Vb of the DC / DC converter 4, and the detection output is taken into the DC / DC converter control circuit 7.

Next, a basic form and an embodiment of the present invention will be described using the photovoltaic power generation apparatus shown in FIG.

( Basic form )
The inverter unit 2 in FIG. 1 converts the DC power output from the solar cell 1 into AC power and is connected to the commercial power source AC. Here, since the output voltage Vin of the solar cell 1 input to the inverter unit 2 is a low voltage with respect to the commercial power supply AC, the voltage is boosted by the DC / DC converter 4 and then orthogonally placed in the subsequent stage of the DC / DC converter 4. It is converted into alternating current by a DC / AC inverter 5 which is a transformer, and is connected to the commercial power supply AC via the connection protection unit 3.

  The control device for the DC / DC converter 4 and the DC / AC inverter 5 includes an operating voltage calculation function 10, a current amplitude calculation function 11, a phase calculation function 12 configured using a microcomputer 10, an analog circuit, and high-speed calculation. A DC / DC converter control circuit 7 and a current control circuit 8 each comprising a DSP are included.

  The output voltage Vin and the output current Iin of the solar cell 1 are detected by the voltage detection transformer PT1 and the current detection transformer CT1, and input to the operating voltage calculation function 10 constituted by the microcomputer 9. The operating voltage calculation function 10 calculates the output power Pin of the solar cell 1 at a preset timing periodically from the output voltage Vin and the output current Iin, and the calculated output power Pin and the output power Pin calculated at the previous sampling time. Thus, the target operating voltage Vref of the solar cell 1 is calculated, and a signal is output to the current amplitude calculation function 11 of the microcomputer 9. The current amplitude calculation function 11 outputs the peak value Ipeak of the alternating current output to the commercial power supply AC so that the target operating voltage Vref and the output voltage Vin of the solar cell 1 match.

  Further, the phase calculation function 12 detects the zero point of the system voltage and calculates the phase from the zero point so as to output the phase data sin θ so that the output current Iout of the inverter unit 2 has a power factor of 1 with respect to the system voltage. The output value Ipeak of the current amplitude calculation function 11 and the output value of the phase calculation function 12 are multiplied by the multiplication function 13, and an instantaneous command value I of the output current is output to the current control circuit 8.

  The current control circuit 8 calculates the necessary pulse width signal PWM2 by feedback control calculation so that the instantaneous command value I matches the output current Iout to the commercial power supply AC, and outputs it to the DC / AC inverter 5 via the driver circuit 62. is doing.

  Further, the DC / DC converter control circuit 7 calculates a necessary pulse width signal PWM1 by feed hack control calculation so that the output voltage Vb of the DC / DC converter 4 becomes constant, and sends it to the DC / DC converter 4 via the driver circuit 61. Output.

  Furthermore, the inverter unit 2 performs an interconnection operation on the commercial power supply AC via the interconnection protection unit 3. The interconnection protection unit 3 disconnects the inverter unit 2 and the commercial power source AC by detecting a frequency variation, a voltage variation, a power failure, or the like of the commercial power source AC.

  FIG. 2 is a flowchart showing details of the operation of the operating voltage calculation function 10. The operating voltage calculation function 10 calculates the output power Pin of the solar cell 1 from the output voltage Vin and output current Iin of the solar cell 1 every sampling (step S1), and the output power Pin and the operating voltage Vin at that time are built in the microcomputer 9. (Step S2). The operating voltage calculation function 10 switches between a mode for searching for the maximum output operating point by changing the operating voltage (Mode 1: hereinafter referred to as a search mode) and a mode for holding an operating voltage (Mode 2: hereinafter referred to as a voltage holding mode). Perform (step S3).

  Next, the operation in each mode will be described. In the search mode, it is first determined whether or not it is operating near the maximum output operating point (step S4). If it is determined that it is not operating near the maximum output operating point, the operation target operating voltage Vref is changed to change the maximum output operating point. Explore. The search method compares the current output power Pin with the stored output power Pin ′ at the previous sampling (step S5), and if it increases, the target operating voltage Vref is changed by ΔV in the same direction as the previous (step S6) If it is decreased, the target operating voltage Vref is changed by ΔV in the direction opposite to the previous time. By repeating the search mode, the operating voltage of the solar cell 1 gradually approaches the maximum output operating point as shown in the period A of FIG. 3, and reaches the maximum output operating point in the period B of FIG. The operation shown is performed.

  In the period B, the amount of change in power repeatedly increases and decreases each time the operating voltage ΔV is changed, and the operating voltage also operates around the voltage at the maximum output operating point.

  When the operation in the period B is detected in (step S4), the maximum value of the output power among the plurality of output powers Pin and Vin near the maximum output operation point stored in (step S2) is Pmax, The operating voltage that outputs the maximum value Pmax is set to Vmax (step S8), and the operation mode is switched from the search mode to the voltage holding mode. The following processing is performed in the voltage holding mode.

  In the voltage holding mode, the target operating voltage Vref is always set to the voltage Vmax set in (Step S8) (Step S10). Similarly, the difference between the power Pmax set in (step S8) and the current generated power (output power) Pin is compared with a predetermined threshold value α (step S11). If the threshold α is equal to or greater than the threshold value α, the target operating voltage Vref is changed by ΔV, and the operation mode is switched from the voltage holding mode (step S15) to the search mode (step S12).

  The actual operation when the maximum power tracking control method described above is performed will be described with reference to FIG.

  When there is no variation in the amount of sunlight as in the solar radiation pattern 1 and the solar radiation pattern 2, the operating voltage calculation function 10 searches for the voltage at the maximum output operating point in the search mode, and then the maximum output operating point (1) (3) in the voltage holding mode. Are operated so as to hold the voltages (solar radiation pattern 1: Vmax1, solar radiation pattern 2: Vmax2).

Also, when the amount of sunshine changes, such as from the solar radiation pattern 1 to the solar radiation pattern 2, the output power at the operating voltage Vmax1 held in the voltage holding mode changes. When (2) is detected, the mode is switched from the voltage holding mode to the search mode, the target operating voltage Vref is changed to search for the voltage Vmax2 at the maximum output operating point after fluctuation of the amount of sunlight, and the voltage is detected after the voltage Vmax2 is detected. Switch to the hold mode and operate to hold the voltage Vmax2. It operates similarly when the solar radiation pattern is changed with the patterns 2 → solar radiation pattern 1.

This basic form is demonstrated based on FIG.

  When operating near the maximum output operating point in the search mode described above, the operating voltage of the solar cell 1 is approximately three potentials V2 and V1 centering on the voltage V1 at the maximum output operating point as shown in FIG. , V3. Therefore, in the process of determining the switching from the search mode to the voltage holding mode (step S4) in the flowchart of FIG. 2, it is possible to make a determination only by monitoring the operating voltage history of the solar cell 2, and the voltage holding mode Thus, the voltage Vmax at the maximum output operating point, which becomes the target operating voltage Vref, is set to the median value among the three potentials, so that the operation at one potential of the voltage at the maximum output operating point can be performed. For example, in FIG. 5A, the operating voltages of the operating points (1), (3), (5), and (7) are equal and the operating voltages of the operating points (4) and (8) and the operating points (2) and (6) are equal. In this case, it is determined that the operation is in the vicinity of the maximum output operation point, and the operation at the operation points (1), (3), (5), and (7) where the voltage Vmax at the maximum output operation point is the median value among the three potentials As the voltage V1, the search mode is switched to the voltage holding mode.

  Although the case of operating at three potentials V2, V1, and V3 has been described, it goes without saying that the voltage of the maximum output operating point may be found by operating at five potentials or averaging.

(Embodiment 1 )
The present embodiment will be described with reference to FIGS. The flowchart of FIG. 6 shows the details of the operation of the operating voltage calculation function 10 in this embodiment. In the present embodiment, even when the operating voltage calculation function 10 detects that a variation in the amount of solar radiation occurs during operation in the voltage holding mode and the change width of the output power Pin is equal to or greater than the threshold value α (step S12). If the power change width for each sampling (| Pin−Pin ′ |) is equal to or greater than the predetermined threshold value β, the voltage holding mode is continued, and if it is equal to or less than the threshold value β (step S13), the operation mode is changed from the voltage holding mode to the search mode. (Step S12) is performed. That is in the present embodiment differs from the basic embodiment in that added flowchart in a step S13 in the basic form, processing in other steps is the same as the basic form.

  Thus, according to the above processing, when a variation in the amount of solar radiation occurs during the voltage holding mode operation, the target operating voltage Vref in the voltage holding mode is the maximum output operating point before the variation in the sunlight amount during the variation in the sunlight amount. The operation mode is switched from the voltage holding mode to the search mode after the voltage Vmax is held and the variation in the amount of solar radiation has converged.

  Next, the operation of the solar cell 1 when this embodiment is used will be described with reference to FIG. FIG. 7 shows the operation of the solar cell 1 when the variation in the amount of solar radiation occurs as follows: solar radiation pattern 1 → solar radiation pattern 2. (1) to (8) indicate operating points for each sampling, and change from (1) to (8). When sunshine fluctuation occurs during operation in voltage hold mode at operating point (1) in solar radiation pattern 1, the operating point changes from (1) → (2) → (3) → (4) for each sampling at operating voltage Vmax1. To do. Although the power change amount: | Pmax−Pin | becomes greater than or equal to the threshold value α due to the change of the operating point (1) → (2), the voltage holding mode is maintained because the power change amount for each sampling is greater than or equal to the threshold value β. Similarly, in (2) → (3) and (3) → (4), the amount of power change is equal to or greater than the threshold value β, and the voltage holding mode is similarly maintained. (4) → (5), since the amount of power change becomes equal to or less than the threshold value β, the operating voltage calculation function 10 determines that the variation in the amount of solar radiation has converged as in the solar radiation pattern 2, and changes the operation mode from the voltage holding mode to the search mode. Switch. In the search mode, the operating point is changed in the order of (5) → (6) → (7) → (8), and the voltage Vmax2 at the maximum output operating point in the solar radiation pattern 2 is detected.

(Embodiment 2 )
This embodiment will be described with reference to FIGS.

The flowchart of FIG. 8 shows details of the operation of the operating voltage calculation function 10 in this embodiment. As shown in FIG. 8, when | Pmax−Pin |> threshold α (step S11) and | Pin−Pin ′ | <threshold β (step S13), that is, fluctuations in the amount of sunlight occur during the voltage holding mode operation. However, when the fluctuation of the amount of sunlight has subsided, when Pmax <Pin, that is, when the amount of solar radiation increases, the maximum output operating voltage after the change in the amount of sunlight is higher than the operating voltage in the voltage holding mode. (Step S14), the next target operating voltage Vref is increased by ΔV to switch to the search mode. When Pmax> Pin, that is, when the solar radiation amount decreases, the voltage at the maximum output operating point at the changed solar radiation amount. Is determined to be lower than the operating voltage in the voltage holding mode (step S14), the next target operating voltage Vref is decreased by ΔV (step S16), and the mode is switched to the search mode. That is, this embodiment is different from the first embodiment in that steps S14 and S16 are added to the flowchart in the first embodiment, and the processing in other steps is the same as that in the first embodiment.

  Next, the operation of the solar cell 1 when this embodiment is used will be described with reference to FIG.

  First, the operating point in the voltage holding mode is (1), and the operating point when | Pmax−Pin |> threshold α and | Pin−Pin ′ | <threshold β (step S13) is satisfied (2) (2). 'And.

  When the output power Pin increases and the fluctuation converges as in the case where the solar radiation pattern is the solar radiation pattern 1 → the solar radiation pattern 2, the voltage at the maximum output operating point increases from Vmax1 to Vmax2. Since the output power at the operating point (2) is increased with respect to the operating point (1), the change direction of the target operating voltage Vref when switching to the search mode is the voltage increasing direction. On the other hand, when the solar radiation pattern decreases as the solar radiation pattern 1 → the solar radiation pattern 2 'and the fluctuation converges, the voltage at the maximum output operating point is as low as Vmax11 → Vmax2'. Since the output power at the operating point (2) decreases with respect to the operating point (1), the change direction of the target operating voltage Vref when switching to the search mode is the voltage decreasing direction.

  In this embodiment, since the operation is as described above, the direction of the maximum output operating voltage after the change in the amount of sunshine coincides with the changing direction of the target operating voltage Vref.

(Embodiment 3 )
This embodiment will be described with reference to FIGS. The flowchart of FIG. 10 shows the detailed operation of the operating voltage calculation function 10 in this embodiment. As shown in FIG. 10, when the output power Pin is low in the voltage holding mode (step S17), if the maximum output power Pmax is less than the predetermined threshold δ (step S18), the target operating voltage Vref is increased (step S18). Step S19). If the operation continues and becomes equal to or higher than the threshold value δ (step S18), the target operating voltage Vref is decreased (step 20). In this case, the setting method of the threshold value δ needs to be smaller than the threshold value α used for determination of switching to the search mode. Further, if the threshold value δ is increased too much, a power loss occurs with respect to the maximum output power Pmax. Therefore, it is desirable to set the value so as not to cause a problem in actual use.

Further, in the flowchart of FIG. 10, the function (steps S18 to S20) is added to the flowchart shown in FIG. 2 of the basic form , but of course, the function may be increased to the flowcharts of FIGS. .

  Next, operation | movement of the solar cell 1 at the time of using this embodiment is demonstrated with reference to FIG. In FIG. 11, (1) to (7) indicate operating points for each sampling, and change in the order of (1) → (7). When operating in the voltage holding mode at the operating point (1) of the maximum output power, if the target operating voltage Vref is increased by ΔV for each sampling, the operating point is (2) → (3) → (4) → (5 ) → (6) → (7). Since the difference between the output power P7 and the maximum output power Pmax at the operating point (7) is equal to or greater than the threshold δ, the target operating voltage Vref is decreased by ΔV and changed to the operating point (6). Since the output power at the operating point (6) is less than or equal to the threshold value δ, the target operating voltage Vref is increased by ΔV. As a result, the operating point changes to (7). P7 indicates the output power at the operating point (7).

  As described above, as long as the solar radiation amount does not vary, the operating point (6) and the operating point (7) operate alternately for each sampling.

It is a flock figure which shows the whole structure of the power converter device which concerns on this invention. It is a flowchart of the maximum electric power tracking control method in a basic form . It is operation | movement explanatory drawing of the maximum output operating point vicinity in a basic form . It is operation | movement explanatory drawing of the solar cell at the time of using the maximum electric power tracking control method in a basic form . It is explanatory drawing of the setting method of the voltage of the maximum output operating point in a basic form . It is a flowchart of the maximum power tracking control method in Embodiment 1. FIG. 5 is an operation explanatory diagram of a solar cell when using the maximum power tracking control method according to Embodiment 1 . 6 is a flowchart of a maximum power tracking control method according to the second embodiment. It is operation | movement explanatory drawing of the solar cell at the time of using the maximum electric power tracking control method in Embodiment 2. FIG. 10 is a flowchart of a maximum power tracking control method according to Embodiment 3 . It is operation | movement explanatory drawing of the solar cell when the maximum electric power tracking control method in Embodiment 3 is used. It is operation | movement explanatory drawing of the solar cell at the time of using the conventional maximum electric power tracking control method. It is explanatory drawing of the change of the operating point at the time of using the conventional maximum power tracking control method. It is explanatory drawing of the power loss in the vicinity of the maximum output operating point at the time of using the conventional maximum power tracking control method. It is explanatory drawing of the malfunction which generate | occur | produces at the time of the fluctuation | variation of the amount of sunlight at the time of using the conventional maximum electric power tracking control method. It is explanatory drawing of the operation | movement at the time of the low solar radiation amount at the time of using the conventional maximum electric power tracking control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Inverter part 3 Connection protection part 4 DC / DC converter 5 DC / AC inverter 61 Drive circuit 62 Drive circuit 7 DC / DC converter control circuit 8 Current control circuit 9 Microcomputer 10 Operating voltage calculation function 11 Current amplitude calculation Function 12 Phase calculation function 13 Multiplication function AC Commercial power supply

Claims (5)

  1. Used the AC as the input power of the solar cell to the solar power obtained by the inverter unit, the inverter unit is a predetermined voltage change the operating voltage of the solar cell, the direction of change in the same direction when increased power output of the solar cell wherein said operating voltage to a predetermined voltage is changed, by performing the operation voltage output power by inverting the direction of change if reduction of the solar cell by repeating the operation that the predetermined voltage change, the maximum output of the solar cell In the maximum power tracking control method for detecting the operating point,
    When the operating voltage of the solar cell repeatedly changes at least at three potentials, the inverter unit determines that the operation is near the maximum output operating point, and the operation near the maximum output operating point of the solar cell. Is determined, the maximum output power value of the solar cell is stored in the storage means, and the operating voltage that is the maximum output power value stored in the storage means is the median value of the potential changing near the maximum output operating point. The inverter unit is controlled so as to fix the operating voltage at which the maximum output power value is set to the median value, and then the output power value of the solar cell is detected, and the detected output power value and Until the difference from the maximum output power value stored in the storage means becomes equal to or greater than a predetermined value, the control to the inverter unit for fixing the operating voltage at the maximum output power value to the median value. Maximum power tracking control method, characterized by continuing.
  2. When the difference is greater than or equal to the predetermined value, the operating voltage is maintained until the change in the output power value of the solar cell to be detected converges, and after the convergence, the operating voltage is changed to obtain a maximum output operating point. The maximum power tracking control method according to claim 1, wherein the maximum power tracking control method is detected .
  3. The direction in which the operating voltage is changed after convergence is such that if the output power value of the solar cell after convergence is increased with respect to the maximum output power value stored in the storage means, the output power after convergence is in the direction of increasing voltage. 3. The maximum power tracking control method according to claim 2, wherein if it decreases with respect to the stored maximum output power, the maximum power tracking control method is changed in a voltage decreasing direction .
  4. The operating voltage is increased when a stored maximum output power value is lower than a predetermined value, if the power output is within a certain power fluctuation range with respect to the maximum output power value stored in the storage means. 4. The maximum power tracking control method according to any one of 1 to 3 .
  5. In a power conversion device including an inverter unit that converts a solar cell into an alternating current as an input power source,
    If the inverter unit changes the operating voltage of the solar cell by a predetermined voltage and the output power of the solar cell increases, the operating voltage is changed by the predetermined voltage in the same direction as the changing direction, and the output power of the solar cell is reduced. Detecting means for detecting the output power value of the solar cell by repeatedly performing the operation of reversing the change direction and changing the operating voltage by the predetermined voltage ;
    Determining means for determining that the operation of the solar cell is an operation near the maximum output operating point when the operating voltage of the solar cell repeatedly changes at at least three potentials ;
    When the determination means determines an operation near the maximum output operating point of the solar cell, storage means for storing the maximum output power value of the solar cell;
    The operating voltage that becomes the maximum output power value is fixed to the median value by setting the operating voltage that becomes the maximum output power value stored in the storage means to the median value of the potential changing near the maximum output operating point. And a control means for controlling the inverter unit ,
    The control means sets the operating voltage that becomes the maximum output power value until a difference between the output power value detected by the detection means and the maximum output power value stored by the storage means becomes equal to or greater than a predetermined value. The power conversion device is characterized in that the control to the inverter unit for fixing to the median value is continued .
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