JP2001218368A - Power converter and photovoltaic generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter capable of operating a solar battery at a maximum power point at all times, without having to use complicated operation in power converter equipment, in which a storage battery is connected in parallel with the solar battery. SOLUTION: This photovoltaic generation system is provided with the solar battery 1, the storage battery 12 connected in parallel with the solar battery, and a power converter 3 for converting power obtained from the solar battery into AC and is formed so as to conduct linkage operation with the other AC power source 6, where the system is provided with an output power detecting means 27 for detecting the output power of the solar battery, an input power detecting means 25 for detecting the input power of the power converter 3, and a controller 26 for controlling, so that the detected value of the point power detecting means and the detected value of the output power detecting means become substantially equal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation system and a power converter, and more particularly to a photovoltaic power generation system that converts generated DC power into alternating current and performs an interconnection operation with a power system or other power generation equipment. The present invention relates to a power converter.

[0002]

2. Description of the Related Art A system that converts DC power of a solar cell into AC and operates in connection with an existing power system has been put to practical use. For example, Japanese Patent Application Laid-Open No.
A structure as disclosed in Japanese Patent Publication No. 179643 is generally known and employed.

FIG. 2 shows a schematic system of the apparatus, wherein 1 is a solar cell, 3 is a power converter, 6 is a power system, and 7 is a load. The DC power obtained by the solar cell 1 is converted into AC by the power converter 3, and the power is supplied to the load 7 in connection with the power system 6. That is, the load 7
When the power required by the solar cell 1 cannot be covered by the solar cell 1 alone, the shortage is configured to be automatically supplied from the system 6, and the output of the solar cell 1 is When the power exceeds the power, the surplus is automatically discharged to the system 6.

The output voltage V of the solar cell 1 is detected by a voltage detector 2 and sent to a DC voltage control circuit 20. On the other hand, the output current and voltage of the power converter 3 are detected by the current detector 4 and the voltage detector 5 and then calculated by the power detector 23, and the output of the power converter 3 at the present time is calculated.

The output of the power detector 23 is sent to a maximum power follow-up control circuit 24, where an optimum operation voltage command is calculated, and a control command is output by the DC voltage control circuit 20 so that the solar cell voltage becomes the command value. And the current control circuit 21
By controlling the power converter 3 through the gate circuit 22 and the gate circuit 22, the operation is performed so that the output of the solar cell is maximized.

The maximum power follow-up control circuit 24 is a circuit for controlling the solar cell voltage so that the maximum power can always be obtained from the solar cell. Next, the operation thereof will be described. The output characteristics of a solar cell fluctuate depending on the solar radiation intensity or the temperature. FIG. 3 shows an example of output characteristics of the solar cell when the solar radiation intensity changes.

FIG. 3 shows the voltage-current characteristic L1 of the solar cell when the solar radiation intensity is I1, the voltage-power characteristic P1 of the solar cell calculated from the voltage-current characteristic L1, and the solar radiation intensity changing to I2. 7 shows the voltage-current characteristic L2 of the solar cell and the voltage-power characteristic P2 of the solar cell calculated from the voltage-current characteristic L2.

From this figure, the voltage at which the maximum power P1max is obtained from the solar cell power characteristic P1 when the solar radiation intensity is I1 is V
Although it is 1, the solar cell voltage must be operated at V2 in order to obtain the maximum power P2max when the solar radiation intensity changes to I2. In other words, the maximum output voltage of the solar cell changes when the solar radiation intensity, temperature conditions, and the like change, so that the maximum power cannot be obtained unless the operating voltage is changed.

[0009] The control that always operates at the voltage of the maximum power point of the solar cell even when the conditions of the solar cell change is the maximum power follow-up control. Until now, various methods have been proposed as the maximum power follow-up control method, but the one that is generally adopted performs a successive comparison of the output of the solar cell at certain time intervals. In this method, the power of the solar cell at the time of this detection is compared with the value of the solar cell output at the time of the previous detection, and the solar cell is always operated at the higher voltage value.

[0010]

In the power converter having the maximum power follow-up control circuit system formed as described above, a device which is constituted only by a solar cell as a power supply and is operated normally. However, there is no particular problem with solar cells.However, photovoltaic power generators can be operated even in an emergency or in the absence of sunlight, and can be used in parallel with solar cells for the purpose of peak load reduction. May be installed in such a case. In this case, there is a possibility that the maximum power tracking control cannot be performed.

That is, the above-described maximum power tracking control is as follows.
The DC voltage is changed according to the output characteristics of the solar cell, so that the maximum power can be obtained from the solar cell.In the case where such a control is performed, when a storage battery is connected in parallel with the solar cell, This means that the internal impedance of the storage battery is very small, and the DC voltage is determined by the storage battery voltage, so that the maximum power tracking control cannot be performed.

Therefore, in the case of a conventional solar power generation device in which a solar cell and a storage battery are connected in series, (1) the solar cell and the storage battery are simply connected in parallel so that the maximum power tracking control itself is not performed. To (2) Always connect the storage battery only when necessary without connecting the storage battery, and do not execute the maximum power tracking control of the solar cell during the period when the storage battery is connected. And so on.

As described above, in the conventional apparatus, in any case, the maximum power cannot be obtained from the solar cell, and there is a dislike that the energy cannot be effectively used. In addition, the storage battery is connected only when necessary. In this case, there is a problem in that the operation of the storage battery must be switched each time, and the operation is complicated.

The present invention has been made in view of the above, and it is an object of the present invention to provide a power conversion system in which a storage battery is arranged in parallel with a solar cell, without having to perform a complicated operation and keeping the solar cell at a maximum power point. It is an object of the present invention to provide a power conversion device of this kind which can be operated with a power converter.

[0015]

That is, the present invention provides a DC power supply, a DC / DC converter for converting the output of the DC power supply to another voltage, and an AC power supply obtained by the DC / DC converter. A power converter that converts to another AC power supply and performs an interconnection operation, and a storage battery connected between the DC-DC converter and the power converter. Output power detection means for detecting output power of the DC power supply, input power detection means for detecting input power of the power converter, a detection value of the input power detection means and a detection value of the output power detection means A control means for controlling the power converters so as to be substantially equal to each other is provided to achieve an intended purpose.

Also, the present invention provides a DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and a converter for converting the power obtained by the DC-DC converter to AC and converting it to another AC. A power converter for interconnecting operation with a power supply,
In a power conversion device including a DC converter and a storage battery connected between the power converter, an output power detection unit that detects output power of the DC power supply, and an input of the power converter. Input power detection means for detecting power,
And control means for controlling the input power of the power converter equal to a value obtained by multiplying the output power of the DC power supply by a coefficient.

Also, the present invention provides a DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and a converter for converting the power obtained by the DC-DC converter into an AC and converting the AC power to another AC. A power converter for interconnecting operation with a power supply,
In a power conversion device including a DC converter and a storage battery connected between the power converter, an output power detection unit that detects output power of the DC power supply, and an input of the power converter. Input power detection means for detecting power,
A control device is provided for controlling the input power of the power converter to be equal to a value obtained by adding an output command from the outside to the output power of the DC power supply.

Further, the present invention provides a DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and a converter for converting the electric power obtained by the DC-DC converter into an AC and converting the AC power to another AC. A power converter for interconnecting operation with a power supply,
In a power converter including a DC converter and a storage battery connected between the power converter, an output power detection unit that detects output power of the DC power supply, and an output of the power converter. Output power detection means for detecting power,
And control means for controlling a value obtained by multiplying the output power of the power converter by a coefficient to be equal to the output of the DC power supply.

Further, the present invention provides a DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and a converter for converting the power obtained by the DC-DC converter into an AC and converting the AC power to another AC. A power converter for interconnecting operation with a power supply,
In a power converter including a DC converter and a storage battery connected between the power converter, an output power detection unit that detects output power of the DC power supply, and an output of the power converter. Output power detection means for detecting power,
There is provided control means for controlling a value obtained by multiplying the output power of the power converter by a coefficient to be equal to a value obtained by adding an output command from the outside to the output power of the DC power supply.

Also, the present invention provides a solar cell, a DC-DC converter for converting the output of the solar cell to another voltage, and a converter for converting the power obtained by the DC-DC converter into an AC to obtain another AC. In a photovoltaic power generation system including a power converter that performs an interconnection operation with a power supply and a storage battery that stores power generated by the solar cell, the system includes an output power detection unit that detects output power of the solar cell. An input power detection means for detecting an input power of the power converter, and a control means for controlling a detection value of the input power detection means and a detection value of the output power detection means to be substantially equal. It was done.

Further, the present invention provides a solar cell, a DC-DC converter for converting the output of the solar cell to another voltage, and a converter for converting the power obtained by the DC-DC converter into an alternating current to produce another alternating current. In a photovoltaic power generation system including a power converter that performs an interconnection operation with a power supply and a storage battery that stores power generated by the solar cell, a maximum current following of the solar cell by the DC-DC converter to the power generation system A control device for controlling the power converter using an output power value of the solar cell obtained during the control operation as an input power command value is provided.

That is, in such a power converter, the power converter is controlled by the control means provided in the device so that the input power of the power converter and the output power of the DC power supply become substantially equal. With such control, operation is performed in a state where the output power of the DC power supply (solar cell) and the input power of the power converter are always equal, and the DC power supply whose maximum output is controlled is operated at the maximum power. Since the output of the DC power supply and the input power of the power converter 3 are equal, the charge and discharge of the power from the storage battery can be ignored if the loss of the circuit is ignored, which affects the storage power of the storage battery. It is possible to operate the solar cell at the maximum power point without complicated operation even in a power conversion facility in which a storage battery is arranged in parallel with the solar cell. Bet is to become possible.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows a schematic system of the power converter. 1 is a solar cell (DC power supply), 12 is a storage battery, 9 is a DC-DC converter, 3 is a power converter, 24 is a maximum power tracking control circuit, 6 is a power system, 7
Is the load.

The electric power generated by the solar cell 1 is input to a DC-DC converter 9 and converted into a predetermined DC voltage by the DC-DC converter 9. After the conversion, the storage battery 12 and the power converter 3 Supplied to The power converter 3 converts the power supplied from the DC-DC converter 9 and the DC power of the storage battery 12 into AC power to supply power to the power system 6.

The output portion of the solar cell 1 includes a voltage detector 2
And a current detector 8, and the output of each detector is sent to a power detection circuit 27, where the output power of the solar cell is calculated. The output of the power detection circuit 27 is sent to the maximum power tracking control circuit 24, which controls the DC-DC converter 9 according to the principle described previously with reference to FIGS. 2 and 3, so that the maximum power is always extracted from the solar cell 1. Is controlled.

On the other hand, an input current and a voltage of the power converter 3 are detected by a voltage detector 10 and a current detector 11 and multiplied by a power detector (input power detecting means) 25, and thereafter, as a signal 25a, a power control circuit. 26. The power control circuit 26 has an input power signal 2 from the power detector 25.
In addition to 5a, an output signal 27a from a power control circuit (output power detection means) 27 is input. The power control circuit 26 uses an output signal 27a from the power control circuit 27 as a reference signal,
Using the signal 25a from the power detector 25 as a control target signal, a control command is output to the power converter 3 so that the signal 25a always becomes the same as the signal 27a.

By controlling in this way, it is possible to operate with the output power of the solar cell 1 and the input power of the power converter 3 always equal. Moreover, since the maximum power of the solar cell 1 is controlled by the DC-DC converter 9, the power converter 3 is equivalent to operating the solar cell 1 at the maximum power. Further, since the output of the solar cell 1 and the input power of the power converter 3 are equal, the charge and discharge of the power from the storage battery can be ignored if the loss of the circuit is ignored, so that the storage power of the storage battery is not affected. Driving can be performed. That is, even when the solar cell and the storage battery are connected in parallel, the maximum power control operation of the solar cell can be performed without being affected by the storage battery.

FIG. 4 is a diagram showing a second embodiment, in which an output signal 27a of a power control circuit 27 is input to a multiplier 28, and the output signal 27a is multiplied by an output 29a from an external coefficient circuit 29. This is an example in which the power converter 3 is controlled with an output signal having a different value.

FIG. 5 is a diagram showing a third embodiment, in which a power converter 27 outputs an output signal 27a of a power control circuit 27 and an output signal 31a of an external power command circuit 31 using a signal synthesized by an adder 30. 3 is controlled. In addition,
In this embodiment, since the power command from the power command circuit 31 is added to the solar cell output power, the power command of the power command circuit 31 is output from the storage battery. That is, by adding the external power command, it is possible to perform the peak cut operation independently of the solar cell output while using the solar cell at the maximum power output.

FIG. 6 shows a fourth embodiment.
The output current of the power converter 3 is detected by the current detector 33 and the output voltage is detected by the voltage detector 34 and sent to the power detector 35, and the output power of the power converter 3 is calculated. The output signal 35a of the power detector 35 is sent to the arithmetic circuit 32. The arithmetic circuit 32 outputs the signal 35a to the power converter 3
By dividing by the power conversion efficiency η, a value 32a corresponding to the input power of the power converter 3 is obtained.

By sending the signal 32a compiled here to the power control circuit 26 and controlling it to be the same as the signal 27a of the power control circuit 27, the same effect as in the above-described embodiment can be obtained.

As described above with reference to the various embodiments, according to the power converter of the present invention, even in a facility in which a storage battery is arranged in parallel with a solar battery, the solar battery can always be operated without complicated operations. It is possible to operate at the maximum power point, and effective use of energy can be achieved. Also,
By adding signals from the outside, it is possible to use complicated operation control while operating the solar cell at the maximum power point.

[0033]

As described above, according to the present invention, even in a power conversion facility in which a storage battery is arranged in parallel with a solar cell, the solar cell can always be operated at the maximum power point without complicated operation. This type of power conversion device capable of performing the above can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing one embodiment of a power converter of the present invention.

FIG. 2 is a schematic system diagram showing a conventional power converter.

FIG. 3 is a diagram illustrating output characteristics of a solar cell.

FIG. 4 is a schematic system diagram showing another embodiment of the power converter of the present invention.

FIG. 5 is a schematic system diagram showing another embodiment of the power converter of the present invention.

FIG. 6 is a schematic system diagram showing another embodiment of the power converter of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solar cell (DC power supply), 2 ... Voltage detector, 3 ... Power converter, 4 ... Current detector, 5 ... Voltage detector, 6 ... Power system, 7 ... Load, 8 ... Current detector, 9 ... DC-DC converter, 10: voltage detector, 11: current detector, 12: storage battery, 20: DC voltage control circuit, 21: current control circuit, 2
2 gate circuit, 22c gate circuit, 23 power detection circuit, 24 maximum power tracking control circuit, 25 power detection circuit (input power detection means), 25a power detection circuit output signal, 26 power control circuit ( Control means), 27 ... power detection circuit (output power detection means), 27a ... power detection circuit output signal, 28 ... multiplier, 29 ... external coefficient circuit, 30 ... adder, 31 ... power command circuit, 31a ... power command Circuit output,
32: arithmetic circuit, 32a: arithmetic circuit output signal, 33: current detection circuit, 34: voltage detection circuit, 35: power detection circuit, 35a: power detection circuit output signal.

Claims (7)

[Claims] 1. A DC power supply, a DC-DC converter for converting an output of the DC power supply to another voltage, and a power obtained by the DC-DC converter converted to AC and connected to another AC power supply. In a power converter including a power converter performing system operation and a storage battery connected between the DC-DC converter and the power converter, the device detects output power of the DC power supply. Output power detection means, input power detection means for detecting input power of the power converter, and a power converter such that a detection value of the input power detection means is substantially equal to a detection value of the output power detection means. A power conversion device, comprising: control means for controlling. 2. A DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and a power obtained by the DC-DC converter converted to AC and connected to another AC power supply. In a power converter including a power converter performing system operation and a storage battery connected between the DC-DC converter and the power converter, the device detects output power of the DC power supply. Output power detection means, input power detection means for detecting the input power of the power converter, and control means for controlling the input power of the power converter equal to a value obtained by multiplying the output power of the DC power supply by a coefficient. A power converter, comprising: 3. A DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and converting the power obtained by the DC-DC converter to AC and connecting with another AC power supply. In a power converter including a power converter performing system operation and a storage battery connected between the DC-DC converter and the power converter, the device detects output power of the DC power supply. Output power detecting means, input power detecting means for detecting the input power of the power converter, and controlling the input power of the power converter to be equal to a value obtained by adding an external output command to the output power of the DC power supply. A power conversion device comprising a control device. 4. A DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and converting the power obtained by the DC-DC converter to AC and connecting with another AC power supply. In a power converter including a power converter performing system operation and a storage battery connected between the DC-DC converter and the power converter, the device detects output power of the DC power supply. Output power detection means, output power detection means for detecting output power of the power converter, and control means for controlling a value obtained by multiplying the output power of the power converter by a coefficient to be equal to the output of the DC power supply And a power converter. 5. A DC power supply, a DC-DC converter for converting the output of the DC power supply to another voltage, and converting the power obtained by the DC-DC converter to AC and connecting with another AC power supply. In a power converter including a power converter performing system operation and a storage battery connected between the DC-DC converter and the power converter, the device detects output power of the DC power supply. Output power detection means, output power detection means for detecting the output power of the power converter, and a value obtained by multiplying the output power of the power converter by a coefficient adds an external output command to the output power of the DC power supply. And a control means for performing control so as to be equal to the set value. 6. A solar cell, a DC-DC converter for converting an output of the solar cell to another voltage, and a power obtained by the DC-DC converter for converting to an AC and connecting with another AC power supply. In a photovoltaic power generation system including a power converter performing system operation and a storage battery storing power generated by the solar cell, the system includes: an output power detection unit configured to detect an output power of the solar cell; Input power detection means for detecting the input power of the converter; and control means for controlling the detection value of the input power detection means and the detection value of the output power detection means to be substantially equal. Solar power system. 7. A solar cell, a DC-DC converter for converting the output of the solar cell to another voltage, and converting the power obtained by the DC-DC converter to AC and connecting with another AC power supply. In a photovoltaic power generation system including a power converter that performs system operation and a storage battery that stores power generated by the solar cell, the power generation system has a maximum current follow-up control operation of the solar cell using the DC-DC converter. A photovoltaic power generation system, comprising: a control device that controls the power converter, using an obtained output power value of the solar cell as an input power command value.