JP2003153434A - Power conditioner for solar power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conditioner with high safety capable of preventing arc discharge. SOLUTION: This power conditioner for solar power generation having a switching means for converting electric power generated from a solar battery to AC power detects voltage at a DC input end of the power conditioner and voltage at an input end of the switching means, and turns off the switching means when the voltage at the DC input end of the power conditioner increases more than the voltage at the input end of the switching means by a prescribed value.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a power conditioner for photovoltaic power generation.

[0002]

2. Description of the Related Art A solar power generation system is a system in which DC power generated by a solar cell is converted into AC power by a power conditioner and is generally connected to a grid to supply the power to a load. This system is extremely clean because it uses the renewable energy of sunlight, and it is being put to practical use worldwide because there is no depletion of resources.

FIG. 3 shows an example of the configuration of such a photovoltaic power generation system, 1 is a solar cell, 2 is a power conditioner,
3 is a load and 4 is a system. In this configuration example, the power conditioner 2 converts the power generated by the solar cell 1 into AC power, which is connected to the grid 4 and supplied to the load 3. At this time,
When the generated power of the solar cell 1 is smaller than the consumed power of the load 3, all the generated power is consumed by the load 3 and the shortage is supplied from the grid 4, but when the generated power is larger than the consumed power of the load 3. Surplus power is generated and is supplied to the grid 4 as reverse flow power.

In FIG. 3, a power conditioner 2 is composed of switching means such as an inverter and a protection device for converting the DC power of the solar cell 1 into AC power and supplying the AC power to the load 3 and the grid 4. . FIG. 4 is a configuration example of such a power conditioner, in which 21 and 22 are noise filters, 23 is a protection diode, 24 is a switching means, 25 is a reactor, 26 is an insulation transformer, and 27.
Is a protective device. In this configuration example, the DC power of the solar cell 1 is converted into AC power by the switching means 24,
It is supplied to the load 3 and the system 4 via the reactor 25 and the insulation transformer 26. The protection device 27 is installed to stop the switching means 24 when a failure occurs in the system 4. In addition, the protection diode 23 is installed in order to prevent electric power from flowing backward from the switching means 24 to the solar cell 1. Further, the high frequency component accompanying the switching of the switching means 24 is the solar cell 1.
Alternatively, noise filters 21 and 22 are built in in order to prevent the noise from flowing out to the system 4.

FIG. 5 shows another example of the configuration of the power conditioner, showing a case where the voltage of the solar cell 1 is boosted. In order to omit the insulating transformer, a reactor 28 and another switching means 29 are added as a step-up chopper. That is, in order to directly connect with the system 4, the system 4
If the voltage is 200V, the DC voltage is 300V
When the above voltage is required and the voltage of the solar cell 1 is lower than this, the reactor 28 and the switching means 29.
To boost the voltage.

[0006]

In the above conventional system, the voltage of the solar cell 1 is usually a relatively high voltage of 200 V or higher in order to improve the system efficiency. Further, the characteristics of the solar cell 1 are constant current characteristics as shown in FIG. 6, and the open circuit voltage Voc is higher than the maximum output operating voltage Va.

In the power conditioner 2, normally, in order to obtain the maximum power from the solar cell 1, the switching means is controlled so that the DC input voltage becomes the maximum output operating voltage Va. In this case, by any chance, a circuit reaching the DC input terminal (a) of the power conditioner 2 and the input terminal (b) of the switching means, that is, the noise filter 21 in FIG.
The protection diode 23 and the noise filter 2 in FIG.
1. If a connection failure occurs in the connection part of the protection diode 23, the reactor 28, etc., the open circuit voltage Voc is applied to the connection part.
The difference voltage (several tens of V) between the maximum output voltage Va and the maximum output voltage Va is instantaneously applied, and as a result of trying to keep the current flowing, arc discharge occurs at the connection failure part. That is, normally, in the power conditioner 2, the switching means is controlled so that the input voltage thereof becomes the point A in FIG. 6, but when a connection failure occurs, a voltage drop due to arc discharge occurs, and the operation of the solar cell 1 proceeds. The point moves to B.

At this time, the current I at the point B is present in the defective connection portion.
Electric power corresponding to the product of b and the voltage drop Vd is generated. For example, if the electric power is 20 A and 20 V, the electric power is 400 W, and a considerable amount of heat is generated. Further, as is well known, since there is no zero point of the current in the direct current, there is a problem that once the arc discharge starts, it does not disappear until a certain space distance is secured.

Accordingly, when such a situation occurs, the temperature inside the power conditioner instantly becomes high,
In some cases, it was a safety issue. An object of the present invention is to provide a highly safe power conditioner that prevents arc discharge by detecting such a connection failure.

[0010]

In order to solve the above problems, a power conditioner for photovoltaic power generation according to the present invention is a power conditioner for photovoltaic power generation having a switching means for converting generated power of a solar cell into AC power. In, the voltage at the DC input end of the power conditioner and the voltage at the input end of the switching means are detected, and the voltage at the DC input end of the power conditioner is higher than the voltage at the input end of the switching means by a predetermined value. The switching means is turned off when the value exceeds the value.

Further, another power conditioner for photovoltaic power generation of the present invention is a solar light having a step-up chopper for boosting the generated power of the solar cell and a switching means for converting the boosted generated power into AC power. In the power conditioner for power generation, the step-up chopper is provided with another switching means, detects the voltage at the DC input terminal of this power conditioner and the voltage at the input terminal of the other switching means, and detects the DC voltage of the power conditioner. The switch means and / or the other switch means are turned off when the voltage at the input end is higher than the voltage at the input end of the other switching means by a predetermined value or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the voltage at the DC input terminal of the power conditioner and the voltage at the input terminal of the switching means are detected. When the voltage at the input end of the switching means is pulse width modulated, the average value is obtained by a filter. Next, the difference between each of these voltages is obtained and compared with a predetermined value. If it is equal to or greater than this value, the switching means is stopped. That is, usually, the difference between the voltages is a value determined by the product of the DC resistance of the circuit and the DC current of the power conditioner, and is a value of about several V at most even during the rated operation of the power conditioner. In the unlikely event that a connection failure occurs, this difference voltage rises to several tens of volts, so that the connection failure can be easily detected.

As a switching means, IGBT or F
ET is applicable, and DC power can be converted to AC power by the switching means. It is preferably combined with a boost chopper.

The boost chopper may be an IGBT or F
It is preferable to have another switching means using ET, and more preferable to be one including a reactor and the other switching means. When the other switching means is provided, the voltage is detected at the input terminal of the other switching means. Then, it is compared with the voltage at the DC input terminal of the power conditioner.

[0015]

1 is an embodiment according to the present invention, in which 51 and 52 are voltage divider circuits, 53 is a constant voltage diode, and 54 is a comparison circuit. Others are the same as the conventional configuration example. In the present embodiment, in a normal condition, the voltage at the DC input end of the power conditioner 2 is an IG that converts DC power into AC power.
Since it is about several V higher than the voltage at the input end of the switching means 24 composed of BT, if this voltage is equal to or lower than the voltage of the constant voltage diode 53 (here, 10 V is used), the voltage dividing circuit 51 The output voltage is lower than the output voltage of the voltage dividing circuit 52, and the output of the comparison circuit 54 is L.

In the unlikely event that a connection failure occurs in the DC circuit of the power conditioner 2, this voltage drop is caused by the constant voltage diode 5
When the voltage exceeds 3, the output voltage of the voltage dividing circuit 51 becomes higher than the output voltage of the voltage dividing circuit 52, the output of the comparison circuit 54 becomes H, and the switching means 24 stops.

FIG. 2 shows another embodiment according to the present invention.
This is the case where the power conditioner 2 has a built-in booster chopper including a reactor 28 for boosting the generated power and another switching means 29 including an IGBT. The configuration in this case is almost the same as that of FIG. 1, but since the input of the other switching means 29 in the step-up chopper is pulse-width modulated, a simple filter capacitor 55 is added to the voltage dividing circuit 52. Thereby, the average voltage at the input end of the other switching means 29 can be detected, and similarly, the voltage drop due to the connection failure can be detected and at least one of the switching means 24 and the other switching means 29 can be stopped. .

As described above, by stopping the switching means, the current path from the solar cell is cut off and the arc discharge can be extinguished. In addition, the difference voltage for detecting the connection failure, that is, the value of the constant voltage diode,
It has been confirmed that 5 to 20 V is preferable, and about 10 V is more preferable.

[0019]

As described above, according to the present invention, the voltage at the DC input end of the power conditioner and the voltage at the input end of the switching means are detected, and the voltage at the DC input end of the power conditioner is detected. Since the switching means is turned off when the voltage rises above a certain value compared to the input terminal voltage, even if a connection failure occurs, it is possible to prevent heat generation due to arc discharge, and it is extremely safe. The effect is that a high power conditioner can be configured.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a power conditioner for photovoltaic power generation according to the present invention.

FIG. 2 is a diagram showing another embodiment of the power conditioner for photovoltaic power generation according to the present invention.

FIG. 3 is a diagram showing an outline of a solar power generation system.

FIG. 4 is a diagram showing an example of a conventional power conditioner for photovoltaic power generation.

FIG. 5 is a diagram showing another example of a conventional power conditioner for photovoltaic power generation.

FIG. 6 is a diagram showing output characteristics of a solar cell.

[Explanation of symbols]

1 solar cell 2 power conditioner 3 load 4 lines 21, 22 Noise filter 23 Protection diode 24, 29 switching means 25, 28 reactor 26 Isolation transformer 27 Protective device 51, 52 voltage divider circuit 53 Constant voltage diode 54 Comparison circuit 55 Filter capacitor

Continued front page    (72) Inventor Tatsuya Kawamatsu             Kyoto Prefecture Kyoto City Minami-ku Kichijoin Nishinosho Inono Babacho             No. 1 within Japan Battery Co., Ltd. F-term (reference) 5G053 AA07 AA09 BA04 CA02 EB01                       FA01                 5H007 BB07 CC01 DB01 DC02 GA08

Claims (2)

[Claims] 1. A power conditioner for photovoltaic power generation having switching means for converting generated power of a solar cell into alternating current power, wherein a voltage at a DC input end of the power conditioner and a voltage at an input end of the switching means are set. Detecting, when the voltage at the DC input end of the power conditioner rises by a predetermined value or more as compared with the voltage at the input end of the switching means, the switching means is turned off. Conditioner. 2. A power conditioner for photovoltaic power generation, comprising: a boosting chopper for boosting the generated power of a solar cell; and a switching means for converting the boosted generated power into AC power. Means for detecting the voltage at the DC input end of the power conditioner and the voltage at the input end of the other switching means, and the voltage at the DC input end of the power conditioner is detected at the input end of the other switching means. A power conditioner for photovoltaic power generation, characterized in that when the voltage rises by a predetermined value or more, the switch means and / or the other switch means are turned off.