JP2001224142A - Photovoltaic generation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give priority to link operation in daytime for quickly charging a discharged battery during night and day and maintain the battery in a full- charge state to prepare for the next self-contained operation. SOLUTION: A controller 9 of a power converter 5, which converts inversely DC power of a solar cell 2 and a battery 3 into AC powers and supplies the AC powers to a load in a link operation and a self-contained operation and converts an AC power of a power system 13 into a DC power for charging in a charging operation, has a means, which distinguishes between day and night according to the magnitude of the voltage of the solar cell 2, a means which monitors the voltage of the battery 3 and a means, which during in a daytime when the system is normal, controls the power converter 5 to be in a charging operation every time when the voltage of the battery 3 is lowered to a discharge limit voltage, predetermined to be in a neighborhood of an overdischaging voltage, and, at night when the system is normal, controls the power converter 5 to be in a charging operation, each time when the voltage of the battery 3 is lowered to a lower limit voltage in a charging state, which is higher than the discharging limit voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generator having a solar cell and a storage battery as a DC power supply and having a function of interconnection operation and independent operation, and more particularly to charging of the storage battery.

[0002]

2. Description of the Related Art Conventionally, a photovoltaic power generator having a function of interconnection operation and independent operation includes a solar cell and a storage battery as a DC power supply.

When the system is normal, the DC power of the solar cell and the storage battery is supplied to a static power converter (bidirectional converter), and the DC power is converted by the inverse conversion of the current control of the interconnection operation of the device. The power is converted into AC power synchronized with the system power supply, and this power is supplied to the system load to form a distributed power supply.

In the event of a power outage due to a disaster or the like, the power supply device is disconnected from the power system, and the DC power of the solar cell and the storage battery is replaced by the system power supply by the reverse conversion of the constant voltage control of the independent operation of the power conversion device. The AC power is supplied to an emergency load or the like.

[0005] By the way, at night, the output of the solar cell is lost, and it becomes difficult to maintain the interconnected operation only by the power of the storage battery. Therefore, the interconnected operation is stopped.

[0006] In order to charge the storage battery discharged by the self-sustaining operation, when the system is normal and at night, the power conversion device is controlled to the charging operation by stopping the power generation of the solar cell or by timer control. DC power for charging is formed based on the power supply, and the storage battery is charged with the DC power to prepare for the next independent operation.

[0007]

SUMMARY OF THE INVENTION In the case of the conventional device,
In the daytime when the output of the solar cell is large, the interconnection operation is prioritized, and the charging of the storage battery by the charging operation is performed only at night based on the stop of power generation of the solar cell and the timer control. Therefore, there are the following problems.

[0008] That is, when a system power failure occurs in the daytime and the operation is switched to the self-sustaining operation, the power that is insufficient with the output of the solar cell is supplemented by the storage battery during the self-sustaining operation.

[0009] By this self-sustaining operation, the discharged storage battery is not charged until night.

[0010] Therefore, if a power failure occurs again after the system is restored and before the storage battery is charged, shortage of power supply is caused in a short time even if the operation is switched to the independent operation, and the time during which the independent operation is possible is shortened. In some cases, self-sustaining operation cannot be performed.

Further, it takes a long time to charge the storage battery at night, and it takes a long time to complete the charging and to be able to operate independently.

In order to prepare for the self-sustaining operation, it is desirable to keep the storage battery in a fully charged state as much as possible.

According to the present invention, a storage battery discharged in priority in the daytime with a priority on interconnection operation is charged promptly without depending on day and night, and the storage battery is kept as fully charged as possible to prepare for the next independent operation. As an issue.

[0014]

In order to solve the above-mentioned problems, in a photovoltaic power generator according to the present invention, a solar cell and a storage battery forming a DC power supply, and a solar cell and a storage battery are operated by an interconnection operation and an independent operation. A stationary power converter that converts DC power of AC power into AC power in reverse, feeds the load, and performs charging operation to convert AC power of the power system into DC power for charging and supplies it to the storage battery. A control device for controlling the operation of the solar cell, the control device includes day / night determining means for determining daytime and nighttime from the magnitude of the voltage of the solar cell, charge / discharge monitoring means for monitoring the voltage of the storage battery, day / night determining means In the daytime when the system is normal, whenever the voltage of the storage battery drops to the discharge limit voltage set near the overdischarge voltage, the voltage of the storage battery changes to the set full charge voltage based on the determination of Rise Until the battery voltage drops to the lower limit voltage of the state of charge that is higher than the discharge limit voltage during the night when the system is normal, and the power converter continues to charge until the battery voltage rises to the full charge voltage. Charge control means for controlling the apparatus to perform a charge operation.

Therefore, in the daytime when the system is normal, the interconnection operation is prioritized. Only when the storage battery is discharged to the discharge limit voltage or less by the self-sustaining operation, after the system is restored, the storage battery is immediately charged to the fully charged state by the charging operation. You.

If the storage battery falls to the lower limit voltage of the charge maintaining state due to spontaneous discharge or the like during the night when the system is normal, the charging operation is performed and the storage battery is reliably maintained in the fully charged state.

For this reason, the discharged storage battery is charged promptly in the daytime with priority given to the interconnection operation, day and night, and the storage battery is kept fully charged as much as possible by night charging to prepare for the next independent operation. it can.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a circuit configuration,
A plurality of AC array units 1a, 1b,.
Includes a solar cell 2 and a storage battery 3 as a DC power supply, supplies a DC output of the solar cell 2 to a stationary power converter 5 composed of a bidirectional inverter via a backflow prevention diode 4, and outputs a DC output of the storage battery 3 The power is supplied to the power converter 5 via the backflow prevention diode 6a of the charge / discharge path switching circuit 6.

At this time, the output voltage of the solar cell 2 is 20 V
Before and after the output voltage of the storage battery 3 is, for example, about 200 V according to the input rating of the power conversion device 5, the output of the solar cell 2 is boosted in the power conversion device 5 and is combined with the output of the storage battery 3 in parallel. Is done.

The voltages of the solar cell 2 and the storage battery 3 are detected by DC voltage detectors 7 and 8, and the detected output is supplied to a control device 9.

Further, the control device 9 is connected to the main control device 12 of the system interconnection protection device 11 via the communication line 10 and, when a system abnormality such as a power failure of the system power supply 14 of the power system 13 occurs, a voltage transformer for the instrument is provided. Each of the AC array units 1 through the communication line 10 from the main controller 12 based on the contact signal of the system interconnection protection relay 16 of the protection device 11 provided on the secondary side of the switch 15.
A system abnormality is notified to the control devices 9 of a to 1n.

The control device 9 has the following units by software processing of a microcomputer. (A) Day / night discriminating means for discriminating between daytime and nighttime from the magnitude of the voltage of the solar cell 2 based on the detection output of the DC voltage detector 7 (b) Storage battery 3 based on the detection output of the DC voltage detector 8
(C) Based on the determination by the day / night determining means and the monitoring by the charging / discharging monitoring means, the voltage of the storage battery 3 becomes close to the overdischarge voltage during the daytime when the system is normal and there is no notification of the system abnormality. Whenever the voltage of the storage battery 3 drops to the set discharge limit voltage, the power converter 5 is controlled to the charging operation until the voltage of the storage battery 3 rises to the set full charge voltage. Charge control means for controlling the power conversion device 5 to charge operation until the voltage of the storage battery 3 rises to the full charge voltage every time the voltage drops to the lower limit voltage of the high charge state

Based on these means, the control device 9 operates as shown in the flowchart of FIG. 2 to control the power conversion device 5 to the interconnection operation, the independent operation, and the charging operation.

Next, control of the control device 9 will be described. First, to determine the setting of the operating mode of the power converter 5 in step S ₁ in FIG. 2, when setting the interconnected operation mode determines whether the system normally proceeds to step S _2.

[0025] When the grid normal and interconnected operation mode is set, determines the day and night on the magnitude of the voltage of the solar cell 2 proceeds to step S _3.

By the way, when the daytime power generation voltage of the solar cell 2 is 20 V or more and the nighttime voltage becomes 10 V or less,
Since the power converter 5 so as not to hunting operation between autonomous operation and interconnected operation, in the determination of step S _2, based on the monitoring of the change tendency of the voltage of the solar cell 2,
As shown in FIG. 3, when the voltage of the solar cell 2 rises, the threshold value is set to 20 V. When the voltage rises to 20 V, the determination of the night time indicated by the broken line is changed to the determination of the daytime indicated by the solid line. Is reduced, the threshold is set to 10 V
When the voltage falls to 0 V or less, the judgment is changed from daytime judgment to nighttime judgment.

[0027] Then, the daytime when the system successfully interconnection operation is performed on the basis of the daytime determination, the process proceeds to step S _4,
Voltage of the battery 3, it is determined whether or not the discharge limit voltages V ₁ below in FIG. 4 is set to over-discharge voltage near the example 180 V (a).

[0028] At this time, is higher than the voltage is V ₁ battery 3 is kept at a charged state, the process proceeds to step S ₆ through step S ₅ from step S _4, generates interconnected operation command.

Then, based on the interconnection operation command, the power converter 5 is operated in synchronization with the system power supply 14, and the DC output of the solar battery 2 and the storage battery 3 is changed to the reverse of the current control of the power converter 5. The conversion converts the AC power into AC power synchronized with the system power supply 14 and supplies the AC power to the load of the power system 14 to form a distributed power supply.

[0030] At mains failure a disaster or the like during the interconnected operation, stopping the interconnected operation moves from step S ₂ to step S _7.

[0031] After that, when automatically or manually isolated operation mode is set, the self-sustained operation command is issued shifts from step S ₁ to step S _8, based on the command, the power converter 5 from the power grid 13 Emergency load (not shown) etc. disconnected from the power system 13 by disconnecting and operating independently, inverting the DC output of the solar cell 2 and the storage battery 3 into AC power of a system frequency controlled at a constant voltage, and the like. Power.

At this time, in order to synchronize the AC array units 1a to 1n, for example, a timing signal for synchronization control is supplied from the main control unit 12 to the control unit 9 of each of the AC array units 1a to 1n. Based on the signal, each AC
The power converters 5 of the array units 1a to 1n are operated independently in synchronization.

[0033] Then, when the system power supply 14 is restored, moves from step S ₉ to step S _10, autonomous operation is stopped.

Thereafter, the operation mode is set to the interconnection operation mode. At this time, in the daytime, the processing of steps S ₁ , S ₂ , S ₃ , and S ₄ is sequentially performed.

Then, the storage battery 3 becomes
Discharge, and the voltage becomes the discharge limit voltage V ₁Has dropped below
Then, step S_FourTo step S₁₁Transfer to charging
Generate a rotation command.

Based on the charging operation command, the control device 9 instructs the power conversion device 5 to perform a charging operation and closes the charging path switch 6b of the charging / discharging path switching circuit 6.

Then, by the forward conversion of the power converter 5,
DC power for charging is formed from the system power supply 14, and the DC power is supplied to the storage battery 3 via the switch 6b, and the storage battery 3 is charged.

By this charging, the storage battery 3 is charged to a fully charged state, and its voltage is equal to the upper limit of the full charge voltage, for example, 230 V
When raised to a full charge voltage V ₂ of FIG. 4 (a) set at, and ends the charging operation shifts from step S ₁₂ to step S _13.

Then, the process returns to the step S _1. At this time, if the interconnected operation mode is set, the interconnected operation is instructed by the control of steps S ₂ , S ₃ , S ₄ , S ₅ and S _6. Then, the power conversion device 5 is connected again.

[0040] Thus, the daytime when the system normally, every time the voltage of the storage battery 3 is reduced to the discharge limit voltage V _1, as shown in (b) of FIG. 4, the power converter 5 charging operation from interconnected operation And the storage battery 3 is charged to a fully charged state.

At this time, the power generated by the solar cell 2 is large, and the storage battery 3 is charged by the generated power, and the charging of the storage battery 3 is completed in a short time.

[0042] Then, since the up storage battery 3 is reduced to the discharge limit voltages V ₁ not performed charge, in the daytime when the system normally discharges in isolated operation performed to minimize disturb the interconnected operation was the accumulator Charging is performed promptly.

Next, during the night when the system is normal, since the solar cell 2 stops generating power and its output disappears, the interconnection operation is not performed, and the voltage of the threshold for charging the storage battery 3 is changed to the daytime. been changed to the lower limit voltage V ₃ of the charge state of the discharge limit voltages V ₁ higher than FIG. 5 (a), the the voltage V _3, for example 225
V.

Once the storage battery 3 is charged to a full charge state, this voltage is changed from V ₂ to V ₃ by natural discharge or the like at night.
Each time drops, the flow proceeds to step S ₁₁ from step S ₃ through the step S _14, and charge operation of power converter 5 generates a charging operation instruction, then step S _14, S ₁₅ from the step S ₃ the repetition of the processing proceeds to step S ₁₂ via, for charging the battery 3 in a fully charged state.

The width W of the voltages V ₂ and V ₃ shown in FIG.
(= V ₂ −V ₃ ) is the charge maintenance width of the storage battery 3.

Therefore, during the night when the system is normal, every time the voltage of the storage battery 3 drops to the lower limit voltage V ₃ of the charged state, the power converter 5 is charged and operated as shown in FIG. The storage battery 3 is charged to a fully charged state, and the storage battery 3 can be always ready for the next self-sustaining operation in the fully charged state.

Therefore, during the daytime, the discharged storage battery 3 can be quickly charged day and night while giving priority to the interconnection operation to prepare for the next self-sustaining operation. In addition, power supply such as an emergency load can be performed by the self-sustaining operation.

In addition, during the night, the storage battery 3 can be maintained in a fully charged state by charging even for spontaneous discharge, and the time during which the battery can be operated independently can be sufficiently lengthened.

The voltages V ₁ , V ₂ , and V ₃ may be appropriately set according to the characteristics of the storage battery 3 and the like.

It is needless to say that the present invention can be similarly applied to a photovoltaic power generator or the like formed by one AC array section.
INDUSTRIAL APPLICABILITY The present invention can be applied to various solar power generation devices that include a storage battery in addition to a solar battery as a DC power supply, and charge the storage battery by forward conversion of a power conversion device.

[0051]

The present invention has the following effects. Due to the operation control of the power conversion device 5 by the control device 9, the interconnection operation is prioritized in the daytime when the system is normal, and only when the storage battery 3 is discharged to the discharge limit voltage or less by the independent operation, after the system is restored, the storage operation is performed by the charging operation. 3 can be charged to a fully charged state.

In addition, during the night when the system is normal, the charging operation is performed every time the storage battery 3 drops to the lower limit voltage of the charge maintaining state due to spontaneous discharge or the like, and the storage battery 3 can be reliably maintained in the fully charged state.

Accordingly, during the daytime, the discharged storage battery 3 is charged promptly in the daytime and nighttime while giving priority to the interconnection operation, and the storage battery 3 is kept as fully charged as possible by nighttime charging to prepare for the next independent operation. As a result, the charging performance of the storage battery 3 of this type of solar power generation device can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a block connection diagram of an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG. 1;

FIG. 3 is an explanatory diagram of determination of daytime and nighttime in FIG. 1;

FIGS. 4A and 4B are explanatory diagrams of a voltage waveform and a charging period of a storage battery during daytime.

FIGS. 5A and 5B are explanatory diagrams of a voltage waveform and a charging period of a storage battery at night.

[Explanation of symbols]

 2 solar cell 3 storage battery 5 power conversion device 9 control device 13 power system 14 system power supply

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/35 H02J 7/35 K (72) Inventor Norio Saka 47-Umezu Takaune-cho, Ukyo-ku, Kyoto Nissin Electric F term (reference) in stock 5G003 AA01 AA06 BA01 CA14 CC02 DA07 DA13 DA18 GB06 5G015 GA02 GA05 JA05 JA06 JA26 JA32 JA34 JA52 JA64 5G066 HA30 HB06 HB09 JA07 JB03 5H420 BB03 BB14 CC03 CC06 DD03 EA48 EB13 EB26 EB39 FF39 EB39 FF39

Claims (1)

[Claims] A solar cell and a storage battery forming a DC power supply in a photovoltaic power generation device that forms a distributed power supply by grid-connected operation when the system is normal and that is disconnected from the power system and operates independently when a power outage occurs The DC power of the solar cell and the storage battery is inversely converted into AC power by a grid connection operation and an independent operation to supply AC power to the load, and the AC power of the power system is converted into DC power for charging by a charging operation. A stationary power converter that supplies the storage battery; and a controller that controls the operation of the power converter. The controller has a day / night determining unit that determines day and night based on the voltage of the solar cell. Charge / discharge monitoring means for monitoring the voltage of the storage battery; and, based on the determination by the day / night determination means and the monitoring by the charge / discharge monitoring means, the voltage of the storage battery is set to be close to the overdischarge voltage during daytime when the system is normal. Control the power converter to a charging operation until the voltage of the storage battery rises to the set full charge voltage every time the battery voltage drops to the discharge limit voltage, and the voltage of the storage battery becomes lower than the discharge limit voltage at night when the system is normal. Charge control means for controlling the power converter to perform a charge operation until the voltage of the storage battery rises to the full charge voltage each time the voltage drops to the lower limit voltage of a high state of charge; .