JP2003134661A - Load interruption detecting device and photovoltaic power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load interruption detecting device for photovoltaic power generator in which voltage rise can be minimized even if a load interruption occurs. SOLUTION: A load interruption detecting system in a photovoltaic power generator performing linkage operation with a power system comprises means for detecting the instantaneous output voltage from the photovoltaic power generator, and means for detecting deviation of a current of the photovoltaic power generator from a command value, wherein occurrence of load interruption of the photovoltaic power generator is determined when the instantaneous value of the output voltage exceeds a predetermined value and/or the deviation of the electric current from the command for exceeds a predetermined value, and when a state of load interruption takes place, an inverter is suspended by a gate blocking means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting load shedding in a photovoltaic power generator that is interconnected with a power system.

[0002]

2. Description of the Related Art Photovoltaic power generation using solar cells, unlike other power generation systems using natural energy, can be easily installed on the roof or wall of a building, and there is no concern about noise or other pollution. It has come to be expected as a pollution power generation system. In recent years, it has become possible to perform interconnection operation with an electric power system, and when performing solar power generation in a general household, it has become common to perform system interconnection with a commercial AC power source by a grid interconnection inverter.

When the photovoltaic power generator is operating in an interconnected manner with the power system, a so-called load cut-off state occurs in which the photovoltaic power generator is suddenly disconnected and the photovoltaic power generator is unloaded. There is. When the load is cut off, the current that has been flowing up to now suddenly becomes zero, causing an abnormal increase in the output voltage of the photovoltaic power generator, which may adversely affect the device. A method of monitoring the current at the system point, detecting an abnormality by detecting a voltage rise, and stopping the inverter by a gate block has been put into practical use.

[0004]

However, in the above method, there is a problem that detection means for monitoring the current at the interconnection point is required, which hinders downsizing and cost reduction of the device. . Further, in the method of detecting the voltage rise, the voltage rise value increases due to the detection delay, so that it is necessary to increase the withstand voltage value of the internal parts, which causes a problem of increasing the cost of the device.

The present invention has been made under such a background, and provides a load cutoff detection device capable of minimizing a voltage rise even if a load cutoff occurs, and a photovoltaic power generation device including the load cutoff detection device. The purpose is to do.

[0006]

According to a first aspect of the present invention, there is provided a load shedding detection device for a photovoltaic power generator that is interconnected with an electric power system, wherein an instantaneous value of an output voltage of the photovoltaic power generator is detected. There is provided a load shedding detection device for a photovoltaic power generation device, comprising: an output voltage instantaneous value detection means for detecting; and a current deviation detection means for detecting a deviation of a current of the photovoltaic power generation device from a command value. .

According to the present invention, means for monitoring the instantaneous value of the output voltage of the photovoltaic power generator and detecting an abnormality when the output voltage exceeds a predetermined ratio with respect to the rated voltage, and an actual value for the command value of the current are detected. Since the load shedding is detected by including means for detecting an abnormality when the deviation of the current exceeds a predetermined value, it is possible to detect the load shedding at any timing at high speed. .

According to a second aspect of the present invention, in the load cutoff detecting device according to the first aspect, the instantaneous value of the output voltage exceeds a predetermined level, or the deviation of the current from the command value exceeds a predetermined level. When it exceeds, it is characterized as a load shedding of the solar power generation device.

According to the present invention, when the instantaneous value of the output voltage exceeds the predetermined level, and when the deviation between the command value of the current and the inverter output current is detected and the deviation exceeds the predetermined value, In both cases, the device protection is performed by recognizing that the load is cut off, so that the peak of the output voltage can be suppressed to a certain value or less, and the safety can be improved.

According to a third aspect of the present invention, in the load cutoff detecting device according to the first aspect, the instantaneous value of the output voltage exceeds a predetermined level, and the deviation of the current from the command value exceeds a predetermined level. When it exceeds, it is characterized as a load shedding of the solar power generation device.

According to the present invention, when the instantaneous value of the output voltage exceeds the predetermined level and the detection deviation between the command value of the current and the inverter output current exceeds the predetermined value, it is determined that the load is cut off and the device protection is performed. Therefore, the reliability can be improved.

According to a fourth aspect of the present invention, in the load cutoff detecting device according to the first aspect, the instantaneous value of the output voltage exceeds a predetermined level and the command value of the current is not zero. When the flowing current is zero, it is characterized by comprising a detection means for recognizing that the load of the photovoltaic power generation device is cut off.

According to the present invention, when the instantaneous value of the output voltage exceeds a predetermined level and the flowing current is zero even though the command value of the current is not zero, it is recognized as a load cutoff and device protection is performed. Therefore, the reliability can be improved.

The invention described in claim 5 is from claim 1 to claim 4.
A load blockage detection device according to any one of, and a gate block means for blocking a gate control signal of an inverter that reversely converts a solar cell output to AC power, and when a condition recognized as the load blockage occurs, There is provided a photovoltaic power generation device characterized in that the inverter is stopped by the gate block means.

According to the present invention, the gate block means for shutting off the gate control signal of the inverter is provided, and when the condition recognized as load shedding occurs, the inverter is stopped by the gate block, so that it is safe and reliable. High-power solar power generation can be implemented.

[0016]

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

<First Embodiment> FIG. 1 is a block diagram showing a structure of a solar power generation apparatus according to a first embodiment of the present invention. In this figure, reference numeral 1 is a solar cell output, which includes a solar cell panel, a connection box, a step-up chopper, and the like, and outputs DC power. The inverter 2 reverse-converts the DC power of the solar cell output 1 into AC power, removes the waveform distortion by the sine filter 4, and performs the interconnection operation with the power system 5 to which the load 6 is connected.

The inverter 2 needs to control the output current in order to be connected to the electric power system 5, and the signal output from the current command value generation means 12 and the current signal from the current sensor 3 are used as the current deviation detection means 13. In the inverter gate control means 14, a gate control signal is generated so that the deviation becomes zero, and the inverter 2 is driven. The solar power generation device with such a configuration is connected to the power grid 5 near the interconnection point.
When the so-called load shedding occurs, where the interconnection with and suddenly becomes unloaded, causing a so-called load shedding, the current that has been flowing up to now suddenly becomes zero, causing an abnormal increase in the output voltage of the photovoltaic power generator, which adversely affects the device. Therefore, it is necessary to stop the inverter 2 promptly.

Therefore, the output voltage instantaneous value detecting means 11 constantly monitors the instantaneous value of the voltage at the interconnection point, and immediately when the instantaneous value of the voltage exceeds 120% of the peak value of the rated voltage, it is immediately detected. A signal is sent to the gate block means 15 to block the gate control signal output from the inverter gate control means 14 to stop the inverter 2.

Further, the current deviation detecting means 13 detects a deviation between the current command value of the current command value generating means 12 and the current signal of the current sensor 3, and the inverter gate control means 14 gates the deviation so as to reduce the deviation. Although the inverter 2 is driven by outputting a signal, the deviation becomes large when the load is cut off. At this time, therefore, a signal is sent to the gate block means 15 to output the gate control from the inverter gate control means 14. The signal is blocked and the inverter 2 is stopped.

In this embodiment, since the inverter is stopped both when the output voltage rises and when the current deviation from the command value becomes large, the peak value of the output voltage can be suppressed to 150% or less. Therefore, the protection method can be made extremely safe.

<Second Embodiment> FIG. 2 is a block diagram showing the configuration of a photovoltaic power generator according to a second embodiment of the present invention. In this figure, reference numeral 1 is a solar cell output, which includes a solar cell panel, a connection box, a step-up chopper, and the like, and outputs DC power. The inverter 2 reverse-converts the DC power of the solar cell output 1 into AC power, removes the waveform distortion by the sine filter 4, and performs the interconnection operation with the power system 5 to which the load 6 is connected.

The inverter 2 needs to control the output current in order to connect with the power system 5, and the signal output from the current command value generating means 12 and the current signal from the current sensor 3 are used as the current deviation detecting means 13. In the inverter gate control means 14, a gate control signal is generated so that the deviation becomes zero, and the inverter 2 is driven. The solar power generation device with such a configuration is connected to the power grid 5 near the interconnection point.
When the so-called load shedding occurs, where the interconnection with and suddenly becomes unloaded, causing a so-called load shedding, the current that has been flowing up to now suddenly becomes zero, causing an abnormal increase in the output voltage of the photovoltaic power generator, which adversely affects the device. Therefore, it is necessary to stop the inverter 2 promptly.

For this reason, the output voltage instantaneous value detecting means 11 constantly monitors the instantaneous value of the voltage at the interconnection point, and when the instantaneous value of the voltage exceeds 120% of the peak value of the rated voltage, it immediately occurs. A signal is sent to the AND circuit 16.
Further, the current deviation detecting means 13 detects a deviation between the current command value of the current command value generating means 12 and the current signal of the current sensor 3, and outputs a gate signal in the inverter gate control means 14 so as to reduce the deviation. Then, the inverter 2 is driven, but when the load is cut off, the deviation becomes large. Therefore, at this time, a signal is sent to the AND circuit 16.

When both the signal of the output voltage instantaneous value detecting means 11 and the signal of the large deviation value from the current deviation detecting means 13 are given to the AND circuit 16, the signal is sent to the gate block means 15. The gate control signal output from the inverter gate control means 14 is blocked to stop the inverter 2. In this embodiment, since the inverter is stopped when the output voltage rises and the current deviation from the current command value becomes large, a highly reliable protection system can be provided.

<Third Embodiment> FIG. 2 is a block diagram showing the structure of a photovoltaic power generator according to a third embodiment of the present invention, which has the same structure as that of the second embodiment. Is. When the so-called load shedding occurs, in which the photovoltaic power generator configured as shown in FIG. 2 is suddenly disconnected from the interconnection with the power system 5 near the interconnection point, resulting in no load, the current that has been flowing up to now suddenly becomes zero. Therefore, the output voltage of the photovoltaic power generator abnormally rises, which may adversely affect the device. Therefore, it is necessary to stop the inverter 2 promptly.

Therefore, the output voltage instantaneous value detection means 11 constantly monitors the instantaneous value of the voltage at the interconnection point, and immediately when the instantaneous value of the voltage exceeds 120% of the peak value of the rated voltage, it is immediately detected. A signal is sent to the AND circuit 16.
Further, the current deviation detecting means 13 detects a deviation between the current command value of the current command value generating means 12 and the current signal of the current sensor 3, and outputs a gate signal in the inverter gate control means 14 so as to reduce the deviation. Then, the inverter 2 is driven, but when the signal of the current sensor 3 becomes zero even though the current command value is not zero, it is judged that the load is cut off and the signal is sent to the AND circuit 16.

When both the signal of the output voltage instantaneous value detecting means 11 and the signal of the large deviation value from the current deviation detecting means 13 are given to the AND circuit 16, the signal is sent to the gate block means 15. The gate control signal output from the inverter gate control means 14 is blocked to stop the inverter 2. In this embodiment, since the inverter is stopped when the output voltage rises and the actual current value is zero even though the current command value is not zero, a very reliable protection method can be provided. it can.

The operation of the embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and design changes within the scope not departing from the gist of the present invention. Etc. are included in the present invention.

[0030]

As described above, according to the present invention, the following effects can be obtained. According to the invention of claim 1, means for monitoring the instantaneous value of the output voltage of the photovoltaic power generator and detecting an abnormality when the output voltage rises above a predetermined ratio with respect to the rated voltage, and an actual value for the command value of the current. Since the load shedding is detected by including means for detecting an abnormality when the deviation of the current exceeds a predetermined value, it is possible to detect the load shedding at any timing at high speed. .

According to the second aspect of the invention, when the instantaneous value of the output voltage exceeds the predetermined level, and when the deviation between the command value of the current and the inverter output current is detected, the deviation exceeds the predetermined value. In both cases, since the device protection is performed by recognizing that the load is cut off, the peak of the output voltage can be suppressed to a certain value or less, and the safety can be improved.

According to the third aspect of the present invention, when the instantaneous value of the output voltage exceeds the predetermined level and the detection deviation between the current command value and the inverter output current exceeds the predetermined value, it is determined that the load is cut off. Since the device is protected by the device, the reliability can be improved.

According to the invention of claim 4, when the instantaneous value of the output voltage exceeds a predetermined level and the flowing current is zero even though the command value of the current is not zero, it is determined that the load is cut off. Since the device is protected by the device, the reliability can be improved.

According to the fifth aspect of the present invention, the gate block means for shutting off the gate control signal of the inverter is provided, and when the state recognized as the load shedding occurs, the inverter is stopped by the gate block. In addition, highly reliable solar power generation can be implemented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a solar power generation device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a solar power generation device according to a second or third embodiment of the present invention.

[Explanation of symbols]

1 ... Solar cell output 2 ... Inverter 3 ... Current sensor 4 ... Sine filter 5 ... Power system 6 ... load 11 ... Output voltage instantaneous value detection means 12 ... Current command value generating means 13 ... Current deviation detecting means 14 ... Inverter gate control means 15 ... Gate block means 16 ... AND circuit

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5F051 KA05 KA08 KA10                 5G053 AA07 AA09 BA01 BA04 CA02                       EB01 FA01                 5G066 HA13 HB06                 5H420 BB13 CC03 DD03 DD09 DD10                       FF03 FF04 FF25 LL02 LL05

Claims (5)

[Claims] 1. A load shedding detection device in a photovoltaic power generation device that is interconnected with an electric power system, the output voltage instantaneous value detection means detecting an instantaneous value of an output voltage of the photovoltaic power generation device; A load-disconnection detecting device, comprising: a current deviation detecting means for detecting a deviation of a current of the power generator from a command value. 2. When the instantaneous value of the output voltage exceeds a predetermined level or the deviation of the current from a command value exceeds a predetermined level, it is determined that the load of the photovoltaic power generation device is cut off. The load shedding detection device according to claim 1. 3. When the instantaneous value of the output voltage exceeds a predetermined level and the deviation of the current from a command value exceeds a predetermined level, it is determined that the load on the photovoltaic power generator is cut off. The load shedding detection device according to claim 1. 4. When the instantaneous value of the output voltage exceeds a predetermined level and the flowing current is zero even though the command value of the current is not zero, the load of the photovoltaic power generator is cut off. The load shedding detection device according to claim 1, further comprising a detection unit that certifies the load. 5. The load cutoff detection device according to claim 1, and a gate block means for cutting off a gate control signal of an inverter for inversely converting the output of the solar cell into AC power. A photovoltaic power generation device characterized in that the inverter is stopped by the gate block means when a condition that is recognized as occurs.