JP2003009398A - Control method of system interconnection power generation system and the system interconnection power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate determination of increase in optimal step-up voltage which is delivered from a booster circuit to an inverter circuit. SOLUTION: In a photovoltaic power generation system 10, comprising solar cells 11, a circuit 14 for boosting DC power generated from the solar cells, an inverter circuit 15 for inverting DC power boosted by the booster circuit into AC power, and a microcomputer 17 for controlling the operation, such that the AC power inverted by the inverter circuit can be regenerated to a commercial power supply system 13, the microcomputer temporarily sets the output voltage from the booster circuit which is higher than an optimal step-sup voltage and then decreases it gradually. During this interval, a switching element 29 in the inverter circuit is controlled, and when the number of times of 100% ON-duty for blocking the switching in one period of AC power outputted from the inverter circuit reaches a specified value, step-up voltage at that time is determined as the optimal step-up voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a control method for a grid-connected power generation device and a grid-connected power generation device that can regenerate a commercial power system that is grid-connected (connected).

[0002]

2. Description of the Related Art In recent years, a solar power generation device as a grid-connected power generator that not only uses power generated by sunlight as an energy source for its own use but also regenerates excess power not used by itself to a commercial power supply system. Is becoming popular.

In such a photovoltaic power generator, after the voltage of the DC power generated by the solar cell is boosted by the booster circuit, the boosted DC power is substantially matched with the AC power of the commercial power supply system by the inverter circuit. It is converted to AC power.

[0004]

When the system voltage of the commercial power supply system is, for example, 200 V, the absolute value of the peak value (peak value) is about 280 V, so the AC power converted by the inverter circuit is commercialized. In order to regenerate the power supply system, the voltage of the DC power input to the inverter circuit needs to be 280V or higher. However, since the voltage of the DC power generated by the solar cell fluctuates depending on the amount of solar radiation and the outside temperature, in order to secure the input voltage required for the inverter circuit, The voltage of the generated DC power is boosted.

On the other hand, as a characteristic of the inverter circuit, the higher the input voltage, the larger the switching loss and the lower the conversion efficiency into AC power. Therefore,
The booster circuit is required to boost the voltage of the DC power generated by the solar cell to the minimum value that can be regenerated to the commercial power supply system.

As described above, the optimum value of the boosted voltage by the booster circuit is determined by the two-dimensional elements of the system voltage of the commercial power supply system and the amount of power regenerated from the inverter circuit to the commercial power supply system. Very difficult.

The object of the present invention was made in consideration of the above circumstances, and a method for controlling a grid-interconnected power generation device capable of easily determining the optimum boosted voltage to be boosted by a booster circuit and output to an inverter circuit, and It is to provide a grid-connected power generation device.

[0008]

According to the present invention, there is provided a power generation unit, a booster circuit for boosting DC power generated by the power generation unit, and a DC power boosted by the booster circuit. And an inverter circuit for converting to AC power,
In a method of controlling a grid interconnection power generation device capable of regenerating AC power converted by the inverter circuit to the commercial power supply system by controlling the booster circuit and the inverter circuit, a boosted voltage output from the booster circuit is used. After the voltage is once set to a voltage higher than the optimum boosted voltage, the voltage is gradually decreased, and during this period, the switching element of the inverter circuit is controlled to turn on 100% of the switching element in one cycle of the AC power output from the inverter circuit.
When the number of duty cycles reaches a prescribed number, the boosted voltage of the booster circuit at this time is determined as the optimum boosted voltage.

According to a second aspect of the present invention, in the first aspect of the invention, the power generation means is a solar cell that generates electric power according to the amount of received sunlight. .

According to a third aspect of the present invention, the power generation means, a booster circuit for boosting the DC power generated by the power generation means, and an inverter for converting the DC power boosted by the booster circuit to AC power. In a grid interconnection power generation device having a circuit and a control device for controlling the booster circuit and the inverter circuit so that the AC power converted by the inverter circuit can be regenerated to the commercial power supply system,
The controller once sets the boosted voltage output from the booster circuit to a voltage higher than the optimum boosted voltage, and then gradually reduces the voltage, and controls the switching element of the inverter circuit during this period to output the booster voltage from the inverter circuit. 100 of the switching elements in one cycle of the generated AC power
% When the number of ON duty reaches the specified number,
It is characterized in that the boosted voltage of the booster circuit at this time point is determined as the optimum boosted voltage.

A fourth aspect of the invention is characterized in that, in the third aspect of the invention, the power generation means is a solar cell that generates electric power according to the amount of sunlight received. .

The invention according to any one of claims 1 to 4 has the following effects.

The boosted voltage output from the booster circuit is once set to a voltage higher than the optimum boosted voltage, and then gradually reduced, and during this period, the switching element of the inverter circuit is controlled to generate the AC power output from the inverter circuit. When the number of 100% ON duty of the switching element in one cycle reaches the specified number, the boost voltage of the boost circuit at this time is determined as the optimum boost voltage, and therefore, the system voltage of the commercial power system and the It is possible to easily determine the optimum boosted voltage of the booster circuit, which is determined based on the amount of power regenerated in the commercial power supply system.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing, together with a commercial power supply system, a photovoltaic power generator to which an embodiment of a grid interconnection power generator according to the present invention is applied.

As shown in FIG. 1, a photovoltaic power generation device 10 as a grid interconnection power generation device is configured to have a solar cell 11 as a power generation means and a grid interconnection device 12, and this grid interconnection device. The device 12 is connected (connected) to the single-phase three-wire of the commercial power supply system 13. And this solar power generation device 1
0 makes it possible for the grid interconnection device 12 to convert the DC power generated by the solar cell 11 by sunlight into AC power and supply (regenerate) it to the commercial power supply system 13.

The solar battery 11 has a large number of solar battery cells, and each of these solar battery cells receives direct sunlight to generate DC power.

The system interconnection device 12 includes a booster circuit 14,
An inverter circuit 15, a current smoothing circuit 16, and a microcomputer 17 as a control device are included in the configuration. The microcomputer 17 includes a boost voltage detection sensor 18, a first system voltage detection sensor 19, a second system voltage detection sensor 20, and an inverter output current detection sensor 21.
Are connected.

The booster circuit 14 inputs unstable DC power generated by the solar cell 11 via a noise filter (not shown) and boosts it to a voltage higher than the system voltage of the commercial power system 13. The smoothing capacitor 22, the choke coil 23, the switch circuit 24, the diode 25 and the capacitor 26 are provided.

The smoothing capacitor 22 is a switch circuit 24.
DC power input to is smoothed. Switch circuit 24
Is composed of a switching element 27 and a diode 28. As the switching element 27, a power transistor, a power MOSFET, an IGBT or the like is suitable. By the ON / OFF operation of the switching element 27, a boosted voltage is generated in the choke coil 23. The capacitor 26 also stores the high voltage power generated by the choke coil 23. Diode 25
Prevent the reverse flow of the high voltage power stored in the capacitor 26.

By adjusting the time for which the switching element 27 is turned on (that is, the ON duty),
The boosted voltage boosted by the booster circuit 14 is controlled. That is, when the system voltage of the commercial power system 13 is 200V, the peak value (peak value) is ± 280V as shown in FIG.
Therefore, in order to regenerate the AC power from the grid interconnection device 12 to the commercial power supply system 13, the boosted voltage by the booster circuit 14 needs to be set to the absolute value of the peak value (280 V) or more. Actually, the boosted voltage by the booster circuit 14 is equal to the switching element 29 of the inverter circuit 15.
ON resistance (described later) and reactor 3 of the current smoothing circuit 16
Considering the resistance of 1, the value is set to a value 20 to 30V higher than 280V.

The inverter circuit 15 is constructed by connecting a plurality of switching elements 29 in a bridge and providing a diode 30 (flywheel diode) corresponding to each switching element 29. The electric power is converted into AC electric power having a sine waveform having a phase and a frequency that substantially match the AC electric power of the commercial power supply system 13.

That is, the inverter circuit 15 performs pulse width modulation on the DC power input from the booster circuit 14 by converting the switching element 29 into ON and OFF, and converts the DC power into AC power. Furthermore, this inverter circuit 15
The switching element 29 is arranged so that the waveform (see FIG. 3) of the AC power (AC current, AC voltage) output from the AC power supply unit 13 matches the AC voltage waveform of the system voltage in the commercial power supply system 13.
The time (ON duty) for turning ON is adjusted.
Thereby, the phase and frequency of the AC power output from the inverter circuit 15 substantially match those of the system power of the commercial power system 13.

The current smoothing circuit 16 is formed of a reactor 31 and a capacitor 32 as shown in FIG. 1, and smoothes the AC power converted by the inverter circuit 15. The AC power smoothed by the current smoothing circuit 16 can be regenerated to the commercial power supply system 13.

The boosted voltage detection sensor 18 is provided with, for example, an isolation amplifier, and detects the boosted voltage boosted and output by the booster circuit 14. The first system voltage detection sensor 19 and the second system voltage detection sensor 20 each include a transformer and detect the system voltage of the system power in the commercial power system 13. Further, the inverter output current detection sensor 21 includes, for example, a current transformer, and detects the alternating current converted by the inverter circuit 15.

The microcomputer 17 regenerates electric power from the system interconnection device 12 to the commercial power system 13, the system voltage detected by the first system voltage detection sensor 19 and the second system voltage detection sensor 20, and the boosted voltage. Based on the boosted voltage detected by the detection sensor 18, the ON duty of the switching element 27 in the booster circuit 14 is adjusted, and the boosted voltage by the booster circuit 14 is controlled as described later.

Further, the microcomputer 17 has a first
System voltage detection sensor 19 and second system voltage detection sensor 2
Based on the waveform of the system voltage (sine wave) detected by 0 and the waveform of the output current detected by the inverter output current detection sensor 21, the ON duty of the switching element 29 in the inverter circuit 15 is changed as described later. Adjust and control. By the control of the booster circuit 14 and the inverter circuit 15 by the microcomputer 17, it is possible to regenerate the AC power that is substantially the same as the AC power of the commercial power system 13 from the system interconnection device 12 to the commercial power system 13.

Next, the control of the booster circuit 14 and the inverter circuit 15 by the microcomputer 17 will be described in detail below.

First, the microcomputer 17 first regenerates electric power from the system interconnection device 12 to the commercial power system 13, and the commercial power system detected by the first system voltage detection sensor 19 and the second system voltage detection sensor 20. On-duty in the switching element 27 of the booster circuit 14 in order to boost the boosted voltage boosted by the booster circuit 14 to a voltage equal to or higher than the optimum boosted power slightly higher than the peak value of the system voltage on the basis of the system voltage of 13. To control.

For example, when the system voltage is 200 V, as shown in FIG. 2, the absolute value of the peak value is 280 V, so that the microcomputer 17 causes the ON resistance of the switching element 29 and the reactor 31 of the current smoothing circuit 16 to operate. In consideration of the resistance of the switching element 27 of the booster circuit 14,
The ON duty in is adjusted and the boost voltage boosted by the boost circuit 14 is controlled to about 320V.

After that, the microcomputer 17 gradually reduces the ON duty in the switching element 27 of the booster circuit 14 to gradually reduce the boosted voltage by the booster circuit 14.

The microcomputer 17 includes a booster circuit 1
While executing the control of 4 described above, the switching element 29 of the inverter circuit 15 is turned on / off (that is, switched) to convert the AC power (AC current, AC voltage) to be converted by the inverter circuit 15. Control to a sine waveform. When the inverter circuit 15 outputs AC power of 50 Hz, for example, the switching of the switching element 29 is 350 per cycle of this AC power.
It is carried out once.

When the boosted voltage by the booster circuit 14 decreases, the phase angles near 90 ° and 270 ° in the AC current waveform of the AC power converted and output by the inverter circuit 15 collapse as shown by the alternate long and short dash line in FIG. . The microcomputer 17 includes an inverter output current detection sensor 21.
When the above collapse of the sine waveform is detected based on the detection information, the ON duty of switching in the switching element 29 is set to be long near the phase angles of 90 ° and 270 ° in the waveform of the alternating current output from the inverter circuit 15. Then, the collapse of the sine waveform is corrected. The microcomputer 17 sets the ON duty to 100% O according to the further decrease of the boosted voltage by the booster circuit 14.
N duty is set, and the number of 100% ON duty is increased to further correct the collapse of the sine waveform in the AC current of the AC power converted by the inverter circuit 15.

The microcomputer 17 controls the switching element 29 10 times for each cycle of the waveform of the AC power (AC current, AC voltage) output from the inverter circuit 15.
Count the number of 0% ON duty switching,
When the number of times of switching reaches the prescribed number of times, the boosted voltage by the booster circuit 14 at that time is set as the optimum boosted voltage, and further reduction of the boosted voltage by the booster circuit 14 is stopped.

The specified number of times is the maximum number of times that the AC current waveform of the AC power converted and output by the inverter circuit 15 can maintain a sine waveform, for example, any number within the range of 20 to 30 times. is there.

Therefore, according to the above embodiment, the following effects can be obtained.

The microcomputer 17 includes a booster circuit 1
The boosted voltage output from 4 is once set to a voltage higher than the optimum boosted voltage, and then gradually reduced, and during this period, the switching element 29 of the inverter circuit 15 is controlled to control the AC power output from the inverter circuit 15. When the number of 100% ON duty of the switching element 29 in one cycle reaches the specified number, the boosted voltage of the booster circuit 14 at this time is determined as the optimum boosted voltage. From this, it is possible to easily determine the optimum boosted voltage of the booster circuit 14 that is determined based on the system voltage of the commercial power supply system 13 and the amount of power regenerated in the commercial power supply system 13.

Although the present invention has been described based on the above embodiment, the present invention is not limited to this.

For example, in the above-described embodiment, the case where the power generation means is the solar cell 11 and the grid interconnection power generation device is the solar power generation device 10 has been described, but other power generation means such as a wind power generation device is used. In addition, another system interconnection generator that regenerates generated power to a commercial power system may be used.

[0040]

As described above, according to the control method for the grid interconnection power generator of the present invention, it is possible to easily determine the optimum boosted voltage boosted by the booster circuit and output to the inverter circuit. .

According to the grid-connected power generation device of the third aspect of the present invention, the optimum boosted voltage boosted by the booster circuit and output to the inverter circuit can be easily determined.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing, together with a commercial power supply system, a photovoltaic power generation device to which an embodiment of a grid interconnection power generation device according to the present invention is applied.

FIG. 2 is a graph showing a waveform of a system voltage in the commercial power supply system of FIG.

FIG. 3 is a graph showing a waveform of an output current converted and output by the inverter circuit of FIG.

[Explanation of symbols]

10 Photovoltaic power generators (system interconnection power generators) 11 Solar cells (power generation means) 12 system interconnection device 13 Commercial power supply system 14 Booster circuit 15 Inverter circuit 17 Microcomputer (control device) 27 switching elements 29 switching elements

Continued front page    (72) Inventor Masaki Koji Masaki             1 Otsuki-cho, Ashikaga City, Tochigi Prefecture Sanyo Electric Air Conditioning             Within the corporation (72) Inventor Yasuhiro Makino             1 Otsuki-cho, Ashikaga City, Tochigi Prefecture Sanyo Electric Air Conditioning             Within the corporation F-term (reference) 5G066 HA30 HB06                 5H007 AA12 BB01 BB07 CA01 CB04                       CB05 CC12 DA06 DB12 DC02                       DC05 EA02                 5H420 BB12 CC02 DD03 DD10 EA11                       EA45 EB09 EB16 EB26 EB39                       FF03 FF04 FF24 FF25

Claims (4)

[Claims] 1. A power generation means, a booster circuit for boosting the DC power generated by the power generation means, and an inverter circuit for converting the DC power boosted by the booster circuit into AC power. In a method of controlling a grid interconnection power generation device capable of regenerating AC power converted by the inverter circuit to a commercial power system by controlling the boost circuit and the inverter circuit, the boost voltage output from the boost circuit is optimally boosted. After setting once to a voltage higher than the voltage, gradually decrease it, while controlling the switching element of the inverter circuit during this,
When the number of 100% ON duty of the switching element in one cycle of the AC power output from the inverter circuit reaches a prescribed number, the boosted voltage of the booster circuit at this time is determined as the optimum boosted voltage. A method for controlling a grid-connected power generation device characterized. 2. The method for controlling a grid interconnection power generation device according to claim 1, wherein the power generation means is a solar cell that generates electric power according to the amount of received sunlight. 3. A power generation unit, a booster circuit for boosting the DC power generated by the power generation unit, an inverter circuit for converting the DC power boosted by the booster circuit to AC power, and the inverter circuit. In a grid interconnection power generator having a controller that controls the booster circuit and the inverter circuit so that the converted AC power can be regenerated to a commercial power supply system, the controller outputs the booster circuit from the booster circuit. Once the boosted voltage is set to a voltage higher than the optimum boosted voltage, the boosted voltage is gradually decreased, and the switching element of the inverter circuit is controlled during this period to perform the switching in one cycle of the AC power output from the inverter circuit. 100 of elements
% When the number of ON duty reaches the specified number,
A system interconnection power generator configured to determine the boosted voltage of the booster circuit at this time as an optimum boosted voltage. 4. The grid-connected power generator according to claim 3, wherein the power generation means is a solar cell that generates electric power according to the amount of received sunlight.