JP3426947B2 - Solar 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 solar power generation device provided with a solar cell provided in a customer or the like and connected to a commercial power system thereof via a power conversion device.

[0002]

2. Description of the Related Art In recent years, solar power has been provided in which a distributed power supply facility of a relatively small capacity of several kW, which uses a DC power supply composed of solar cells, is connected to a commercial power system through a power converter to supply power to a load. Various power generators have been proposed.

FIG. 4 is a schematic configuration diagram of a conventional solar power generation device. In the figure, 21 is a solar cell that directly converts the energy of sunlight into DC power, and 22 is the solar cell 2
1 is an inverter main circuit as a power conversion device for converting the DC power output from 1 into AC, and the solar cell 2
The DC output from the inverter 1 is converted into AC by the inverter main circuit 22, and then the load 2 is passed through the system interconnection switch 23.
4 and the commercial power system 25.

The switch 23 has an inverter controller 26.
Is controlled by. This inverter control unit 26
Monitors the output voltage of the solar cell 21 and the system voltage of the commercial power system 25. When the voltage is excessive or insufficient, the switch 23 determines that the solar cell 21 or the commercial power system 25 is in an abnormal state. Is open. After that, when the cause of the abnormality is eliminated, the inverter control unit 26 closes the switch 23 after a predetermined time has passed, and then the inverter main circuit 2
2 is running.

In the above solar power generation device, in order to efficiently extract the maximum power from the solar cell 21, a control method for tracking the command operating point given to the solar cell to the maximum power point of the solar cell, a so-called MPPT method (mountain climbing). Law) has been adopted.

According to this method, the command operating point given to the solar cell 21 is changed, and if the output power from the solar cell 21 at that time is increasing, the direction in which the command operating point is changed is maintained as it is, and the output is changed. If the power is in the decreasing direction, the changing direction of the command operating point is reversed so that the operating point of the solar cell 21 is always controlled to be near the maximum power point.

On the other hand, it is known that the solar cell 21 generally changes the maximum amount of electric power that can be taken out from the solar cell 21, as shown in FIG.
The amount of solar radiation varies depending on the time (season) and the time zone, and the maximum amount of electric power that can be taken out from the solar cell 21 is small in the morning and evening when the amount of solar radiation is small at the same time.

[0008]

Therefore, when the maximum power point tracking control by the MPPT method is performed after the inverter main circuit 22 is started, as shown in FIG. 6 in the morning and evening when the amount of solar radiation is small. In addition, the maximum power point became less than the voltage value at which interconnection was possible, and the chattering phenomenon that repeatedly started and stopped frequently occurred, and smooth start-up could not be performed.

Further, in the case where the main body of the apparatus has a display section such as an operation display lamp, the display section repeatedly blinks for a long time, which may cause anxiety to the user.

Therefore, it is conceivable to change and set the starting voltage of the inverter main circuit 22 to an open circuit voltage value when the maximum power point of the solar cell 21 becomes equal to or higher than the voltage value that can be interconnected. It is necessary to reset the setting at each transition of the season, or to hold the calendar function inside the device, which is inconvenient for the user and complicates the device.

The present invention has been made in view of the above point, and enables continuous operation for a long time without causing anxiety or annoyance to the user, and does not complicate the apparatus. (EN) Provided is a solar power generation device that enables a smooth start-up of a power conversion device regardless of the time zone.

[0012]

According to the present invention, a power converter for converting a DC output generated from a solar cell into an AC output having a predetermined voltage and outputting the AC output is connected to a commercial power system to supply power to a load. In the solar power generation device, the power detection means for detecting the generated power of the solar cell and the command operating point given to the solar cell are changed, and the command operating point is increased in the direction in which the output power from the solar cell at that time increases. A maximum power tracking mode for shifting the, and a predetermined voltage mode for setting a command operating point to be given to the solar cell to a predetermined value equal to or higher than the open circuit voltage value at that time so that the solar cell operates near the open circuit voltage, Control means for controlling the output of the power conversion device so as to make the operating point of the solar cell follow the set command operating point in each mode, and the control means, the generated power of the solar cell is a constant power value or more. of Controlling the output of the power converter at the maximum power tracking mode in case, on the other hand, when the generated power of the solar cell is less than a predetermined power value and controls the output of the power converter at a predetermined voltage mode.

More specifically, the control means starts the activation of the power converter in a predetermined voltage mode, and the command operating point is the output voltage of the solar cell. By using this configuration, during the period when the operating point voltage of the solar cell at the maximum power point is not higher than the voltage value sufficient to operate the power converter, the voltage higher than the voltage that allows the solar cell to be connected is used. The solar cell operates near the maximum power point voltage during the period when the power generated by the solar cell exceeds a certain power value.

Further, since the solar cell is operated by giving a constant command operating voltage at the start of starting the power conversion device, a chattering phenomenon that frequently starts and stops can occur in the morning and evening when the amount of solar radiation is small. Without this, smooth startup is possible.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A solar power generator according to an embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a photovoltaic power generation device using a solar cell to which the present invention is applied.

In FIG. 1, a photovoltaic power generator is a solar cell 1 (a rated output of 3 kW in the present embodiment) for converting sunlight energy into DC power, and DC power for the solar cell 1 is converted into AC power. The main inverter circuit 2 is a power conversion device that supplies a predetermined AC voltage, and the power is supplied to the load 4 such as various home appliances connected to the distribution line in connection with the commercial power system 3. Is being supplied.

The inverter main circuit 2 is composed of a plurality of bridge-connected switching elements. The inverter main circuit 2 receives a pulse width modulated switching control signal from an inverter control unit 5 which performs various processes described later. To be The inverter control unit 5 is composed of a microcomputer.

A system interconnection relay (hereinafter abbreviated as relay) 6 and a breaker 7 for system protection are provided between the inverter main circuit 2 and the commercial power system 3.
The relay 6 opens or closes its contact point in accordance with a control signal from the inverter control unit 5 to be connected to or disconnected from the commercial power system 3. Further, the breaker 7 opens its contact to disconnect the commercial power system 3 in response to a control signal from the inverter control unit 5, and manually closes the contact to connect to the commercial power system 3.

Between the solar cell 1 and the inverter main circuit 2, a DC voltage detecting means 8 composed of an isolation amplifier for detecting the output voltage of the solar cell 1 and a DC voltage for detecting the output current of the solar cell 1 are provided. Current detection means 9 is provided, and both detection results are input to the inverter control unit 5. The detection value of the DC voltage detecting means 8 is also input to one of the differential amplifiers 10.

In the inverter control unit 5, the output power of the solar cell 1 is calculated based on the detection values of the DC voltage detection means 8 and the DC current detection means 9, and the output power is given to the solar cell 1 in the increasing direction. A maximum power tracking mode in which the command operating voltage is changed to track the maximum power point of the solar cell 1, and the command operating voltage applied to the solar cell 1 is fixed to a predetermined voltage value (set to 250 V in this embodiment). The predetermined voltage mode is switched and set based on the value of the output power of the solar cell 1, and the setting command operating voltage Vref is input to the other side of the differential amplifier 10.

Therefore, at the time of start-up, the operation is started with the set command operation voltage Vref in the predetermined voltage mode, and when the output power of the solar cell 1 becomes 50 W or more, the mode is switched to the maximum power tracking mode. As a result, the chattering phenomenon that repeatedly starts and stops frequently does not occur in the morning or evening when the amount of solar radiation is small. Here, solar cell 1
Output power of 50 W or more is the maximum power point voltage of the solar cell 1 at that time (150 in the present embodiment).
This is because V) is equal to or higher than the voltage (140 V in this embodiment) capable of connecting the inverter main circuit 2 to the commercial power system 3.

Further, since the setting command operating voltage Vref in the predetermined voltage mode is set to 250V, the period when the open circuit voltage of the solar cell 1 is 250V or less, that is, the solar cell 1
During a period in which the power generated from the solar cell is small, the solar cell 1 operates near the open circuit voltage at that time. Therefore, in the predetermined voltage mode, since the interconnection operation is performed in a state where the inverter main circuit 2 supplies almost no electric power to the commercial power grid 3 and the load 4, the output voltage of the solar cell 1 is supplied by the power supplied to the commercial power grid 3 side. Does not fall below the voltage that can be interconnected.

The differential amplifier 10 compares the output voltage value of the solar cell 1 with the set command operating voltage value, amplifies the error, and inputs it to one of the multipliers 11. In addition, between the inverter main circuit 2 and the relay 6, the inverter main circuit 2
AC current detection means 12 for detecting the output current of the inverter is provided, and AC voltage detection means 13 for detecting the output voltage of the inverter main circuit 2 is provided between the relay 6 and the breaker 7. ing.

Then, the fundamental wave frequency component of the interconnection point voltage detected by the AC voltage detecting means 13 is extracted by the band pass filter 14, and the extracted fundamental wave frequency component of the interconnection point voltage of the multiplier 11 is extracted. It is input to the other.

The multiplier 11 multiplies the error signal from the differential amplifier 10 and the fundamental frequency component signal from the bandpass filter 14 to generate a current command value of the inverter current phase-synchronized with the system voltage. ing. Therefore, this current command value becomes a value for synchronizing the output voltage of the solar cell 1 to the set command operating voltage Vref in synchronization with the system voltage during the interconnection operation with the commercial power system 3.

The current command value from the multiplier 11 and
An error amplifier 15 amplifies the difference from the inverter current of the inverter main circuit 2 detected by the AC current detecting means 12 and inputs it to the inverter controller 5 as a current error signal.

In the inverter control section 5, the error amplifier 1
The current error signal from 5 is compared with a reference triangular wave signal of about 20 kHz, and the switching signal is supplied to the switching element of the inverter main circuit 2 so that the current error signal from the error amplifier 15 becomes zero. 2 is PWM (pulse width modulation) controlled, and the inverter operation of the inverter main circuit 2 is started or stopped.

Next, the operation contents of the inverter control unit 5 in the solar power generation device configured as described above will be described with reference to the flowchart of FIG. First, it is determined whether the open circuit voltage of the solar cell 1 is 180 V or more (S1), and if YES, the process proceeds to step S3.
It operates in a predetermined voltage mode and outputs 250 V as a command operation voltage Vref to be given to the solar cell 1. Then, a PWM control signal for controlling the inverter current is sent to the inverter main circuit 2 so that the output voltage of the solar cell 1 becomes 250 V, and the interconnection operation is started.

Next, the generated power of the solar cell 1 is detected, and it is determined whether or not the generated power exceeds a certain power value (set to 50 W in the present embodiment) (S5), and YE
In the case of S, the process proceeds to step S7 and the operation mode is switched from the predetermined voltage mode to the maximum power tracking mode, while N
If it is O, the process proceeds to step S9, and it is determined whether or not the output voltage of the solar cell 1 is equal to or higher than the voltage that can be interconnected (set to 140 V in this embodiment), and if YES, step S9.
Returning to step 5, if NO, the relay 6 is opened, the sending of the PWM control signal to the inverter main circuit 2 is stopped to stop the inverter operation (S15), and the process returns to step S1.

Then, in step S7, the generated power of the solar cell 1 is detected, and a value obtained by changing the command operating voltage Vref given to the solar cell 1 in the direction in which the generated power increases is output, and the solar cell is output to Vref. The PWM control signal for controlling the inverter current is sent to the inverter main circuit 2 so that the output voltage of 1 becomes 1.

In step S11, it is determined whether or not the output voltage of the solar cell 1 is equal to or higher than the voltage (= 140 V) that can be interconnected.
If YES, the process proceeds to step S13, and if NO, the process proceeds to step S15.

In step S13, the generated power of the solar cell 1 is detected, and the generated power is the above constant power value (= 50).
W) or more is determined, and if YES, the process returns to step S7, and if NO, the operation is set to the predetermined voltage mode (S17), and then the process returns to step S11.

As a result of the above operation, as shown in FIG. 3, when the operating point voltage of the solar cell 1 at the maximum power point is not higher than the voltage value sufficient for interconnecting the inverter main circuit 2, During a period in which the battery 1 is operated at a voltage that is equal to or higher than the voltage that can be interconnected and the generated power of the solar cell 1 is equal to or higher than a constant power value, the solar cell 1 is operated near the maximum power point voltage.

Further, since the solar cell 1 is operated by giving a constant command operating voltage at the time of starting the activation of the inverter main circuit 2, it is frequently activated in the morning or evening when the amount of solar radiation is small,
Chattering phenomenon that repeats stoppage does not occur.

The above description of the embodiments is for explaining the present invention and should not be construed as limiting the invention described in the claims or reducing the scope. Further, the configuration of each part of the present invention is not limited to the above embodiment,
It goes without saying that various modifications can be made within the technical scope described in the claims.

For example, in the above embodiment, the case where the output from the inverter main circuit 2 is current-controlled has been described, but the present invention is not limited to this configuration, and for example, a circuit configuration for controlling the output voltage from the inverter main circuit 2. It doesn't matter.

[0037]

As described above, according to the present invention, when the operating point voltage of the solar cell at the maximum power point is not higher than the voltage value sufficient to interconnect the power converter, the solar cell is not operated. The solar cell operates near the maximum power point voltage during the period when the power generated by the solar cell exceeds a certain power value and the voltage is higher than the voltage that can be interconnected. Stable interconnection operation can be performed for a long time without causing a chattering phenomenon in which start and stop are frequently repeated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a photovoltaic power generator according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation content of an inverter control unit 5 in the device shown in FIG.

FIG. 3 is an explanatory diagram of changes in the output voltage and the command operating voltage of the solar cell 1 in the morning in the device of FIG.

FIG. 4 is a schematic configuration diagram of a conventional solar power generation device.

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

FIG. 6 is an explanatory diagram of a solar cell output voltage change in the morning in the conventional device.

[Explanation of symbols]

1 solar cell 2 Inverter main circuit 3 commercial power system 4 load 5 Inverter control unit 6 grid interconnection relay 7 breakers 8 DC voltage detection means 9 DC current detection means 10 Differential amplifier 11 multiplier 12 AC current detection means 13 AC voltage detection means 14 bandpass filter 15 Error amplifier

Front page continuation (72) Inventor Masahiro Maekawa 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP-A-9-179643 (JP, A) JP-A-8- 80054 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 3/00-5/00 G05F 1/67

Claims (3)

(57) [Claims] 1. A solar power generation device for converting a DC output generated from a solar cell into an AC output of a predetermined voltage and outputting the AC output to a commercial power system to supply electric power to a load. And a maximum power tracking mode that changes the command operating point given to the solar cell, and shifts the command operating point in the direction in which the output power from the solar cell increases at that time. , Solar cells open
It works in the vicinity of voltage discharge, and a predetermined voltage mode for setting the command operating point to be given to the solar cell on the open-circuit voltage value or more at value at that time, the solar cell setting command operating point of each mode A control unit that controls the output of the power conversion device so as to follow the operating point, and the control unit is the power conversion device in the maximum power tracking mode when the generated power of the solar cell is equal to or higher than a constant power value. And controlling the output of the power conversion device in a predetermined voltage mode when the generated power of the solar cell is smaller than a constant power value. 2. The control means starts the activation of the power conversion device in a predetermined voltage mode.
The solar power generation device described. 3. The solar power generation device according to claim 1, wherein the command operating point is an output voltage of a solar cell.