JP2003070167A - Power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generating system for improving controllability at a low cost although a plurality of power converting parts are provided. SOLUTION: Each distributed power supply 2 is provided with a DC power supply 21 and an inverter 22. Each inverter 22 is provided with a power converting part 22a for converting a DC voltage from the DC power supply 21 into an AC voltage. A protection apparatus 5 determines the existence of abnormality in the system, implements the protecting operation if there is the abnormality in the system and is provided with a zero-cross detecting circuit 23 for detecting a voltage phase from a commercial power supply 1 and a reference sinusoidal wave producing part 24 for producing a sinusoidal wave synchronized with the voltage waveform from the commercial power supply 1 based on an output from the zero-cross detecting circuit 23 and outputting the sinusoidal wave to each power converting part 22a. A fluctuation component produced by a fluctuation component producing part 51 is superimposed on the sinusoidal wave produced by the reference sinusoidal wave producing part 24 and supplied to each power converting part 22a. A reference setting means comprises the zero-cross detecting circuit 23 and the reference sinusoidal wave producing part 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation system that includes a plurality of distributed power sources that are grid-connected to a commercial power source and that supplies power to a load.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, there has been considered an in-house power generation system including a plurality of distributed power sources 2 grid-connected to a commercial power source 1 and supplying power to a load 3. Here, each distributed power source 2 is configured by a DC power source 21 such as a solar cell, and an inverter device 22 that converts a DC voltage output from the DC power source 21 into an AC voltage and outputs the AC voltage.

By the way, a solar cell generally used in an in-house power generation system is one in which a plurality of solar cell modules (a solar cell module is composed of many solar cells) are arranged and connected in series (so-called solar cell). Array). Therefore, when the number of solar cell modules is different in each DC power supply used in the private power generation system, or when the normal direction of the panel installation surface is different in each DC power supply,
Alternatively, when using direct current power supplies having different output characteristics such as a fuel cell and a wind power generator, if all the direct current power supplies are connected to one inverter device, there is a problem that the overall power generation efficiency is reduced. Therefore, in the above-described private power generation system, a small capacity inverter device 22 is provided for each small capacity DC power supply 1 in order to improve the overall power generation efficiency.

Since the distributed power source 2 needs to output a sinusoidal voltage waveform synchronized with the voltage waveform of the commercial power source 1,
In each inverter device 22, a power conversion unit 22a that converts a DC voltage output from the DC power supply 21 into a sinusoidal AC voltage and outputs the AC voltage, a zero-cross detection circuit 23 that detects the voltage phase of the commercial power supply 1, and a zero-cross detection circuit. There is provided a reference sine wave creating unit 24 that creates a sine wave signal synchronized with the voltage waveform of the commercial power supply 1 based on the output of the detection circuit 23 and outputs the sine wave signal to the power conversion unit 22a. The reference sine wave creating unit 24 described above is realized by incorporating software into a microcomputer. Further, each power conversion unit 22a includes, for example, a main circuit in which four switching elements are bridge-connected and each switching element of the main circuit is P
It is composed of a PWM control circuit for WM control.
The M control circuit uses the error between the sine wave signal and the output current signal of the main circuit as an input signal and compares it with a triangular wave composed of a switching carrier wave to determine the pulse width P.
Each switching element is PWM-controlled by the WM signal.

In the private power generation system as described above,
If the distributed power supply 2 continues to operate independently when the power supply from the commercial power supply 1 is stopped due to an accident in the power supply system of the commercial power supply 1 or maintenance work, the distributed power supply 2 will be distributed to the power supply system of the commercial power supply 1 A current may flow from the power source 2, and there is a possibility that a worker may get an electric shock, the damage of an accident may be expanded, or the load 3 may be damaged. Therefore, for example, when the commercial power supply 1 fails, it is required to reliably prevent the distributed power supply 2 from operating independently.

Therefore, the above-described private power generation system is provided with a protection device 5 which determines whether or not there is a system abnormality and performs a predetermined protection operation if there is a system abnormality. The protection device 5 stops the operation of the inverter device 22 when a system abnormality is detected, and disconnects (that is, opens) the disconnection relay (not shown) provided at the interconnection point 4. I am trying to do. Here, in the protection device 5, an overvoltage detection function for detecting a voltage change of the commercial power supply 1 to detect that the voltage has become overvoltage, and a voltage change to an undervoltage for detecting the voltage change of the commercial power supply 1 (regulation Undervoltage detection function to detect (lower than the value), frequency rise detection function to detect the frequency change of the commercial power supply 1 and detect that the frequency has risen, frequency decrease to detect the frequency change of the commercial power supply 1 Since it has four functions of the frequency drop detection function to detect such a situation, when the power supply from the commercial power source 1 is stopped due to an accident in the power system of the commercial power source 1 or maintenance work, Although it is possible to prevent the islanding operation from being continued, it may not be possible to detect the islanding operation of the distributed power source 2 with only these four functions. It is also available reliably detect the islanding operation of the distributed power supply 2 by combining the two methods of dynamic systems.

The passive method is a method of detecting a sudden change in voltage phase, frequency, etc., which occurs when the distributed power source 2 shifts to an independent operation, and is generally characterized by being excellent in high speed. On the other hand, the active method means that the output current of the inverter device 22 is obtained by superposing the fluctuation component created by the fluctuation component creation unit 51 provided in the protection device 5 on the sine wave signal created by the reference sine wave creation unit 24. To the normal power supply of the commercial power supply 1 (that is, the distributed power supply 2
Is connected to commercial power source 1), commercial power source 1
Change of the voltage at the interconnection point 4 with the power supply system does not appear, and the voltage at the interconnection point 4 appears when the commercial power source 1 is abnormal (for example, when the distributed power source 2 is in the independent operation state). In this system, the independent operation of the distributed power source 2 is determined by detecting the voltage change at the interconnection point 4. Here, the fluctuation component created by the fluctuation component creation unit 51 of the protection device 5 is transmitted to each inverter device 22 via a communication line or the like, and the PWM control circuit of the power conversion unit 22 a in each inverter device 22 uses the reference A fluctuation component is superimposed on the sine wave signal created by the sine wave creating unit 24 and is input. In addition, each DC power source 21
When a solar cell is used as the solar cell, the output voltage of each DC power supply 21 changes according to the amount of solar radiation, so that the output current of each inverter device 22 also changes according to the output voltage of the DC power supply 21. is there.

Further, when the above-described private power generation system is disconnected from the commercial power source 1 for independent operation, only one of the plurality of inverter devices 22 is operated independently or synchronization between the plurality of inverter devices 22 is performed. A plurality of inverter devices 22 are provided by providing a control line for taking them and synchronously operating the plurality of inverter devices 22 independently, or by controlling the voltage of only one inverter device 22 and controlling the current of the other inverter device 22. 22 is operated independently, or a plurality of inverter devices 22 are operated independently by a control method in which all inverter devices 22 are current-controlled and gradually synchronized.

[0009]

However, in the above-described private power generation system, the zero-cross detection circuit 23 and the reference sine wave generation unit 24 are required in the number of the power conversion units 22a, and the sine wave signal described above is not necessary. When it is generated by a computer, there is a problem that the number of power conversion units 22a requires a capacity for recording data for creating a sine wave signal. In addition, the fluctuation component created by the fluctuation component creation unit 51 of the protection device 5 is converted into the power conversion unit 22.
a must be frequently transmitted to a through a communication line or the like, and when all the power conversion units 22a are operated independently, there is a problem that a synchronization line is provided or complicated control is required. It was

The present invention has been made in view of the above circumstances, and an object thereof is to provide a power generation system that has a plurality of power conversion units, is inexpensive, and has improved controllability.

[0011]

In order to achieve the above object, the invention of claim 1 is a DC power source for generating DC power, and a power converter for converting a DC voltage output from the DC power source into an AC voltage. And a plurality of distributed power sources including
In a power generation system that systematically links these distributed power sources with a commercial power source and supplies the power generated by each distributed power source to a load connected to the commercial power source, the output frequency of the power conversion unit is the commercial power source. The reference setting means for creating a sine wave signal as a reference for making the frequency substantially equal to is shared by at least two or more power conversion units, and the reference setting means is at least two. Since it is shared by two or more power conversion units, it is not necessary to provide reference setting means for the number of power conversion units, and a power generation system that has a plurality of power conversion units and is inexpensive and has improved controllability can be provided. Can be provided.

According to a second aspect of the present invention, in the first aspect of the invention, the reference setting means detects the voltage phase of the commercial power source, and the voltage of the commercial power source based on the output of the zero cross detection circuit. Since it has a reference sine wave creation unit that creates a sine wave signal synchronized with the waveform,
Since the reference setting means has a reference sine wave creation unit that creates a sine wave signal and outputs it to each power conversion unit,
When a sine wave signal is created by a microcomputer, the sine wave signal can be created by a smaller number of microcomputers than the number of power conversion units, so an inexpensive power generation system can be provided.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the reference setting means includes a fluctuation component creating section for adding a fluctuation component to the output current of the power conversion section, and the sine wave signal. Since the fluctuation component is superimposed on and output to the power conversion unit, it is possible to reliably detect the isolated operation of the distributed power source, but the fluctuation component is frequently transmitted to each power conversion unit via a communication line or the like. Need not be transmitted to each power converter, and each power converter can be stably controlled with a simple configuration.

The invention of claim 4 is the first to third aspects of the invention.
In the invention of, the reference setting means, when the commercial power source and the distributed power source are not interconnected, creates a reference sine wave signal of a preset frequency, and gives common synchronization to each power conversion unit, All the power converters can be easily and stably operated when the commercial power source and the distributed power source are not interconnected without providing a synchronization line for synchronizing the plurality of power converters or performing complicated control. Can be operated independently.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) A power generation system according to this embodiment is a private power generation system as shown in FIG. 1, and includes a commercial power source 1 and a plurality of distributed power sources 2 which are grid-connected to a load 3 Is configured to supply power to. Here, each distributed power source 2 is a DC power source 2 such as a solar cell.
1 and an inverter device 22 that converts a DC voltage output from the DC power supply 21 into an AC voltage and outputs the AC voltage. It should be noted that the same components as those of the conventional configuration shown in FIG. Further, the DC power supply 1 is not limited to a solar cell, but a fuel cell, a wind power generator, or the like may be used.

Since the distributed power source 2 needs to output a sinusoidal voltage waveform synchronized with the voltage waveform of the commercial power source 1,
Each inverter device 22 is provided with a power conversion unit 22a that converts a DC voltage output from the DC power supply 21 into a sinusoidal AC voltage and outputs the AC voltage. Each power conversion unit 22a includes a main circuit in which four switching elements are bridge-connected and a PWM control circuit that PWM-controls each switching element of the main circuit. The PWM control circuit will be described later. An error between a sine wave signal and an output signal of the main circuit is used as an input signal, and each switching element is PWM-controlled by a PWM signal whose pulse width is determined by comparison with a triangular wave composed of a switching carrier wave.

Further, in the private power generation system of this embodiment, the operation of the inverter device 22 is stopped when a system abnormality is detected, and the system is connected to the power system of the commercial power source 1 as in the conventional configuration shown in FIG. A protection device 5 for disconnecting (that is, opening) a disconnection relay (not shown) provided at the system point 4 is provided. Like the conventional configuration, the protection device 5 has four functions of an overvoltage detection function, an undervoltage detection function, a frequency rise detection function, and a frequency fall detection function, and is independent by using two methods, a passive method and an active method. The operation can be detected reliably.

In the present embodiment, the fluctuation component created by the fluctuation component creation unit 51 of the protection device 5 is superimposed on the sine wave signal created by the reference sine wave creation unit 24, so that the output current of the inverter device 22 changes by a predetermined amount. When the commercial power supply 1 is normal (that is, when the distributed power supply 2 is in the interconnected operation with the commercial power supply 1), the voltage at the interconnection point 4 does not change and the commercial power supply is abnormal ( For example, when the distributed power source 2 is in the independent operation state), the voltage at the interconnection point 4 is changed, and the voltage change at the interconnection point 4 is detected to determine the independent operation of the distributed power source 2. The method is adopted.

By the way, in the conventional configuration shown in FIG. 4, for each inverter device 22, a zero-cross detection circuit 23 for detecting the voltage phase of the commercial power supply 1 and a voltage waveform of the commercial power supply 1 based on the output of the zero-cross detection circuit 23 are obtained. A reference sine wave creating unit 24 that creates a synchronized sine wave signal and outputs it to the power conversion unit 22a is provided. On the other hand, in the private power generation system of the present embodiment, the zero-cross detection circuit that detects the voltage phase of the commercial power supply 1 in the protection device 5 that determines whether there is a system abnormality and performs a predetermined protection operation if there is a system abnormality. 23 and a reference sine wave creating unit 24 that creates a sine wave signal synchronized with the voltage waveform of the commercial power source 1 based on the output of the zero-cross detection circuit 23 and outputs the sine wave signal to each power conversion unit 22a. The fluctuation component created by the creating unit 51 is superimposed on the sine wave signal created by the reference sine wave creating unit 24, and is provided to each power conversion unit 22a. in short,
PW of the power converter 22a in each inverter device 22
The fluctuation component is superimposed on the sine wave signal created by the reference sine wave creating unit 24 and input to the M control circuit. However, in the present embodiment, the variation component is superimposed on the sine wave signal in each inverter device 22. In this embodiment, the protection device 5 constitutes a protection means, and the inverter device 22 constitutes a fluctuation component superposition means.

The protection device 5 in this embodiment is mainly composed of a microcomputer, and the above-mentioned functions, the fluctuation component creating section 51, the reference sine wave creating section 24, etc. are realized by incorporating appropriate software into the microcomputer. However, using the zero-cross detection circuit 23 and the reference sine wave generator 24 provided in the protection device 5, the commercial power source 1
The sine wave signal that is synchronized with the voltage phase of is generated in an analog manner, and the protection device 5 has a function of simultaneously outputting the sine wave signal to each inverter device 22. On the other hand, each power converter 22a of each inverter device 22 outputs an AC voltage having a waveform substantially similar to that of the sine wave signal.

In this embodiment, the zero-cross detection circuit 23 and the reference sine wave generator 24 provided in the protection device 5 serve as a reference for making the output frequency of each power converter 22a substantially equal to the frequency of the commercial power source 1. The reference setting means for creating the sine wave signal is formed. In other words, in this embodiment, one reference setting unit is shared by all the power conversion units 22a.

In this embodiment, however, since one reference setting means is shared by the plurality of power converters 22a, the reference setting means composed of the zero-cross detection circuit 23 and the reference sine wave generator 24 is used for power conversion. It is not necessary to provide the number of units 22a, and it is possible to provide a private power generation system that has a plurality of power conversion units 22a, is inexpensive, and has improved controllability.

Further, the reference setting means creates a zero-cross detection circuit 23 for detecting the voltage phase of the commercial power supply 1 and a sine wave signal synchronized with the voltage waveform of the commercial power supply 1 based on the output of the zero-cross detection circuit 23. And a reference sine wave creating unit 24 for outputting to each power conversion unit 22a.
Since 2a outputs an AC voltage that is substantially the same as the sine wave signal, when the sine wave signal is created by a microcomputer, it can be created by a single microcomputer regardless of the number of power conversion units 22a, which is inexpensive. A system can be provided.

(Embodiment 2) The basic configuration of the private power generation system of this embodiment is substantially the same as that of Embodiment 1, and as shown in FIG. It is characterized in that it has a function of superimposing the fluctuation component created by the fluctuation component creation unit 51 on the sine wave signal and transmitting the superimposed signal to each power conversion unit 22a. That is, in the present embodiment, since the protection device 5 is provided with the fluctuation component superimposing means that superimposes the fluctuation component created by the fluctuation component creation unit 51 on the sine wave signal created by the reference sine wave creation unit 24, each inverter device is provided. Since it is not necessary to provide the function of superimposing the fluctuation component on the sine wave signal at 22, the cost can be reduced compared to the first embodiment. Note that the other configurations and operations are the same as those in the first embodiment, and thus the description thereof will be omitted.

By the way, the protection device 5 in this embodiment
When the commercial power source 1 and the distributed power source 2 are not interconnected (when the dispersed power source 2 is operated independently), as shown in FIG.
The reference sine wave creating unit 24 has a function of generating a sine wave signal having a preset frequency and outputting the sine wave signal to each power conversion unit 22a, that is, a function of giving common synchronization to each power conversion unit 22a, Multiple inverter devices 2
Even when the two are synchronized and operated independently, it is possible to easily and stably operate all the power conversion units 22a without providing a synchronization line for synchronizing the plurality of power conversion units 22a or performing complicated control. Can be operated independently.

[0026]

According to the invention of claim 1, a plurality of distributed power supplies are provided, each of which comprises a DC power supply for generating DC power and a power converter for converting a DC voltage output from the DC power supply into an AC voltage. In a power generation system that systematically links these distributed power sources with a commercial power source and supplies the power generated by each distributed power source to a load connected to the commercial power source, the output frequency of the power conversion unit is the commercial power source. The reference setting means for creating a sine wave signal serving as a reference for making the frequency substantially equal to the frequency of 1 is shared by at least two or more power converters, and the reference setting means is at least two or more power converters. Since it is shared by the power conversion units, it is not necessary to provide reference setting means for the number of power conversion units, and it is possible to provide a power generation system that has a plurality of power conversion units, is inexpensive, and has improved controllability. There is an effect that that.

According to a second aspect of the present invention, in the first aspect of the invention, the reference setting means detects a voltage phase of the commercial power source, and a voltage of the commercial power source based on an output of the zero cross detection circuit. Since it has a reference sine wave creation unit that creates a sine wave signal synchronized with the waveform,
Since the reference setting means has a reference sine wave creation unit that creates a sine wave signal and outputs it to each power conversion unit,
When a sine wave signal is created by a microcomputer, the sine wave signal can be created by a smaller number of microcomputers than the number of power conversion units, so that an inexpensive power generation system can be provided.

According to a third aspect of the present invention, in the first or the second aspect of the invention, the reference setting means includes a fluctuation component creating section for adding a fluctuation component to the output current of the power conversion section, and the sine wave signal. Since the fluctuation component is superimposed on and output to the power conversion unit, it is possible to reliably detect the isolated operation of the distributed power source, but the fluctuation component is frequently transmitted to each power conversion unit via a communication line or the like. Therefore, there is an effect that each power conversion unit can be stably controlled with a simple configuration without needing to transmit to each of the power conversion units.

The invention of claim 4 is the invention of claims 1 to 3.
In the invention of, the reference setting means, when the commercial power source and the distributed power source are not interconnected, creates a reference sine wave signal of a preset frequency, and gives common synchronization to each power conversion unit, All the power converters can be easily and stably operated when the commercial power source and the distributed power source are not interconnected without providing a synchronization line for synchronizing the plurality of power converters or performing complicated control. The effect is that it can be operated independently.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a private power generation system showing a first embodiment.

FIG. 2 is a schematic configuration diagram of a private power generation system showing a second embodiment.

FIG. 3 is a schematic configuration diagram when the distributed power source operates independently in the same as above.

FIG. 4 is a schematic configuration diagram of a private power generation system showing a conventional example.

[Explanation of symbols]

1 Commercial power supply 2 distributed power sources 3 load 4 interconnection points 5 Protective device 21 DC power supply 22 Inverter device 22a Power converter 23 Zero cross detection circuit 24 Reference sine wave generator 51 Varying component creation section

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyoshi Goto             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company (72) Inventor Akira Yoshitake             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F-term (reference) 5G066 HA02 HB03 HB06                 5H007 AA05 AA06 BB07 CB04 CC05                       DA03 DA06 DB01 DB05 DC05                 5H420 BB03 BB12 CC02 DD03 EA39                       EA43 EA48 EB39 FF03 FF11                       FF25

Claims (4)

[Claims] 1. A plurality of distributed power supplies comprising a DC power supply for generating DC power and a power conversion unit for converting a DC voltage output from the DC power supply into an AC voltage, and the distributed power supplies are commercial power supplies. In a power generation system that is systematically connected to each other and supplies the power generated by each distributed power source to the load connected to the commercial power source, in order to make the output frequency of the power conversion unit approximately equal to the frequency of the commercial power source. The power generation system is characterized in that the reference setting means for creating a sine wave signal as a reference of is shared by at least two or more power conversion units. 2. The zero-cross detection circuit for detecting the voltage phase of the commercial power supply, and the reference sine for creating a sine wave signal synchronized with the voltage waveform of the commercial power supply based on the output of the zero-cross detection circuit. The power generation system according to claim 1, further comprising a wave generator. 3. The reference setting means includes a fluctuation component creation unit that adds a fluctuation component to an output current of the power converter, and superimposes the fluctuation component on the sine wave signal and outputs the superimposed signal to the power converter. The power generation system according to claim 1 or 2, characterized in that. 4. The reference setting means, when the commercial power source and the distributed power source are not interconnected, creates a sine wave signal of a preset frequency to give common synchronization to each power conversion unit. The power generation system according to any one of claims 1 to 3, which is characterized.