JP2017169264A - Power conditioner and method of detecting theft of cable connected thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect theft of a power transmission cable of a photovoltaic power generation system in a power conditioner reliably and quickly.SOLUTION: A power conditioner includes: a DC input side connected to a solar panel via a cable; an AC output side connected to an electric power system; an inverter for converting a DC power input from the DC input side into AC power; voltage applying means for applying a DC voltage to a DC side circuit including the cable; a current detector for measuring a current flowing through the DC side circuit; and a disconnection detection processing unit for detecting disconnection of the cable on the basis of a DC current value measured by the current detector. Theft of the cable connected to the power conditioner can be detected by a disconnection detection signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conditioner used for a photovoltaic power generation system.

  In recent years, the spread of photovoltaic power generation systems is expanding. In a solar power generation system, solar light energy is converted into DC power by a solar panel, and this DC power is sent to a power conditioner via a cable, converted into AC power by the power conditioner, and connected to the power system. The power is sold.

  Japanese Unexamined Patent Application Publication No. 2012-233825 (Patent Document 1) is a conventional technique for measuring the insulation resistance and capacitance of a DC circuit of a DC power supply system. In this publication, “a measuring instrument and a measuring method capable of measuring a part of insulation resistance and capacitance in a DC circuit of a DC power supply system in a live state using a coupling capacitor and an AC power supply are disclosed. (0007) ”“ A variable AC power supply unit that is connected to a DC circuit to be measured by an electric circuit and applies an AC current having a constant voltage and a constant frequency, and a measurement of the DC circuit A clamp unit that is attached to a target part and acquires an AC component current; a voltage and frequency of an AC current applied by the variable AC power supply unit; and an AC component current in the measurement target part that is acquired by the clamp unit; And a calculation means for calculating an insulation resistance of a part to be measured of the DC circuit based on (1).

JP2012-233825A

In solar power generation systems, power transmission cables are severed and often stolen. Theft is performed at night when the output power of the solar cell is lost, and only the cable on the direct current side with a low risk of electric shock is often cut. Therefore, even if a security measure is applied to the current collection box or the power conditioner, if the cable is exposed, the possibility of being stolen increases.
It can be said that burying cables in the ground is a better countermeasure, but depending on the construction method, it may be dug up. Also, anti-theft measures such as fencing the site and installing a camera that can monitor the entire site are expensive, and depending on the construction method, what can be done to reduce damage reliably? I can not say.

  Patent Document 1 describes measuring insulation resistance and capacitance in a DC circuit of a DC power supply system, but does not detect theft of a power transmission cable.

  Therefore, an object of the present invention is to detect a theft of a power transmission cable of a solar power generation system reliably and quickly in a power conditioner.

  An example of the “power conditioner” of the present invention for solving the above problems is as follows. A solar panel is connected to the DC input side via a cable, a power system is connected to the AC output side, and a DC input is provided. A power conditioner having an inverter for converting DC power input from the AC side to AC power, voltage applying means for applying a DC voltage to a DC side circuit including a cable, and measuring a current flowing through the DC side circuit And a disconnection detection processing unit for detecting disconnection of the cable based on a direct current value measured by the current detector.

  In addition, if an example of “theft detection method of a cable connected to a power conditioner” of the present invention is given, a solar panel is connected to the DC input side via a cable, and a power system is connected to the AC output side. A method of detecting theft of a cable connected to a power conditioner having an inverter that converts DC power input from the DC input side into AC power, and applies a DC voltage to a DC side circuit including the cable by a voltage applying means. A step of measuring a current flowing in the circuit on the DC side with a current detector, and a disconnection detection processing unit determining that the measured DC current value is equal to or less than a set value and detecting a cable disconnection. And a step of outputting a disconnection detection signal and a step of outputting an alarm output based on the disconnection detection signal.

  ADVANTAGE OF THE INVENTION According to this invention, in a power conditioner, the theft of the power transmission cable of a solar power generation system can be detected reliably and rapidly.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of the block diagram of the solar energy power generation system of Example 1 of this invention. It is an example of a structure of the disconnection detection process part 30 of FIG. It is a flowchart explaining the process of the disconnection detection process part 30 of FIG. It is a time chart until it detects the theft of a power transmission cable.

  Embodiments of the present invention will be described below with reference to the drawings.

  Theft of a power transmission cable of a solar power generation system is often stolen from a DC side cable with a low risk of electric shock. In this embodiment, a theft of a power transmission cable is detected by applying a DC voltage to a circuit on the DC side of the photovoltaic power generation system and detecting a current.

FIG. 1 shows an example of a configuration diagram of a photovoltaic power generation system.
The solar power generation system includes a solar panel (solar cell) 1, a connection box 3, a power conditioner 100, and a power system 2.

The solar panel 1 outputs the generated DC power to the power conditioner 100 via the connection box 3. At this time, the P (+) side cable connecting the junction box 3 and the power conditioner 100 may have the diode 4. The diode 4 is for preventing the current on the DC side from flowing in the reverse direction, and may be attached to the cable on the N (−) side with the direction reversed.
The power conditioner 100 converts DC power into AC power, and exchanges AC power with the existing power system 2.

  The power conditioner 100 generally includes an inverter unit 21, an insulating transformer 11, an AC side MC (Magnetic Contactor) 12, a system side breaker 13, a DC side breaker 14, a DC unit capacitor 15, and a power supply circuit 16.

The inverter unit 21 converts the input DC power into AC power and outputs it.
The insulation transformer 11 is a transformer provided between the inverter unit 21 and the power system 2 and insulates the inverter unit 21 and the power system 2.
The system side breaker 13 is a circuit breaker that is inserted when the power system 2 and the power conditioner 100 are connected, and is also used as protection on the AC side.
The AC side MC 12 is input when the inverter unit 21 and the power system 2 are connected via the system side breaker 13.
The DC side breaker 14 is a breaker that is inserted when the solar panel 1 and the power conditioner 100 are connected, and is also used as a DC side protection.
The DC unit capacitor 15 is a capacitor provided on the DC side of the power conditioner 100 and smoothes the DC voltage.
The power supply circuit 16 converts the power supplied from the AC side or the DC side into a control power supply and supplies it to the control circuit 40. In addition, while power is being supplied to the power supply circuit 16, a signal is output to the power supply detection output terminal 9.

  The power conditioner 100 according to the present embodiment is configured to apply a voltage to a DC side circuit including the cable and detect a current flowing through the DC side circuit including the cable in order to detect disconnection of the power transmission cable. The control circuit 40 is provided.

As a configuration (voltage applying means) for applying a voltage to a DC side circuit including a cable, a DC voltage conversion circuit 22, a DC voltage application switch 23, a DC side MC 18, a reactor 20, and a switch 19 are provided.
The DC voltage conversion circuit 22 converts the power supply on the system side to DC, and applies a DC voltage to the DC side circuit when the DC voltage application switch 23 is turned on. At this time, the polarity to which the DC voltage conversion circuit 22 applies the DC voltage is a polarity that is not obstructed by the diode 4.
The DC side MC 18 is always turned on and is disconnected only when the DC voltage application switch 23 is turned on.
The reactor 20 is connected between the P (+) side wiring and the N (−) side wiring, and suppresses a direct current when the direct current voltage conversion circuit 22 is driven.
The switch 19 connected in series with the reactor 20 is turned on when a direct current is passed through the circuit on the direct current side.

  As a configuration for detecting a current flowing in a DC side circuit including a cable, a current detector 17 is provided, and the current detector 17 detects a DC current value flowing in the circuit.

The control circuit 40 includes a disconnection detection processing unit 30 and an alarm output circuit 41.
The disconnection detection processing unit 30 performs a disconnection detection process described below and outputs a cable disconnection detection signal.
The alarm output circuit 41 outputs an alarm output to the alarm output terminal 8 based on the disconnection detection signal input from the disconnection detection processing unit 30.

  An alarm means such as a display means or an alarm means may be connected to the alarm output terminal 8 so that an abnormality is notified when an alarm output is output from the alarm output terminal 8. The alarm means may be provided in the power conditioner.

FIG. 2 shows an example of the configuration of the disconnection detection processing unit 30.
The disconnection detection processing unit 30 includes a circuit drive determination unit 31 and a comparison calculation unit 32.

  The circuit drive determining unit 31 outputs the MC disconnection command and disconnects the DC side MC 18 when the DC voltage of the DC unit capacitor 15 is sufficiently low. Next, a DC voltage application command is output to the DC voltage application switch 23, and the DC voltage output from the DC voltage conversion circuit 22 is applied to both ends of the DC side MC 18, thereby applying the DC voltage to the DC side circuit. Thereafter, a switch input command is output to the switch 19 so that a current flows through the circuit on the DC side via the reactor 20. At this time, if the switch 19 is continuously turned on, the current detector 17 may be damaged. Therefore, the switch is turned on to the switch 19 so that the DC current value detected by the current detector 17 does not exceed a certain current value. The command is preferably a PWM output.

  The comparison calculation unit 32 determines whether the DC current value detected by the current detector 17 is greater than a set value, for example, 0, detects cable disconnection, and outputs a disconnection detection signal to the alarm output circuit 41. .

FIG. 3 shows a flowchart for explaining the processing of the disconnection detection processing unit 30.
First, the circuit drive determination unit 31 confirms whether or not the DC voltage of the DC unit capacitor 15 is sufficiently low (S301), and if low, outputs an MC disconnection command to the DC side MC 18 (S302). For example, at night, the output power of the solar cell disappears, and the DC voltage of the DC capacitor 15 decreases. Thereafter, a DC voltage application command is output to the DC voltage application switch 23 (S303), and the DC voltage is applied from the DC voltage conversion circuit 22 to the DC side circuit. Then, a switch input command is output to the switch 19 (S304), and a circuit including the reactor 20 is configured. In S301, if the DC voltage value of the DC unit capacitor 15 is not sufficiently low, monitoring is performed until it becomes low.

  Next, the current detector 17 measures the current flowing through the circuit on the DC side. Then, the comparison calculation unit 32 compares whether the DC current value detected by the current detector 17 is larger than a set value, for example, 0 (S305). If the DC current value is larger than the set value, the cable is not disconnected, so that it waits for a certain time (S306), and it is confirmed again whether the DC current value is larger than the set value. If the direct current value is smaller than the set value, it is determined that the cable is disconnected, and a disconnection detection signal is output to the alarm output circuit 41 (S307).

FIG. 4 shows a time chart until the power cable is detected.
When it is detected that the DC voltage value of the DC capacitor 15 has become sufficiently low at time t1, the MC disconnection command is sent to the DC side MC 18, the DC voltage application command is sent to the DC voltage application switch 23, and the switch input command is sent to the switch 19. DC current flows through the circuit on the DC side including the cable. Thereafter, the current detector 17 continues to detect the current flowing through the DC side circuit. When the cable is disconnected, the direct current stops flowing, and when the disconnection is detected by the comparison calculation unit 32 at t2, a disconnection detection signal is output. As shown in the figure, the switch input command applied to the switch 19 is a periodic pulse signal, and the current flowing through the circuit is a periodic pulse current.

A part or all of the control circuit 40 may be realized by hardware by designing, for example, an integrated circuit. Alternatively, the processor may be realized by software by interpreting and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.
Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  In the power conditioner of this embodiment, a solar panel is connected to the DC input side via a cable, an electric power system is connected to the AC output side, and an inverter that converts DC power input from the DC input side into AC power is provided. A power conditioner having a voltage applying means for applying a DC voltage to a DC side circuit including a cable, a current detector for measuring a current flowing through the DC side circuit, and a DC measured by the current detector A disconnection detection processing unit configured to detect disconnection of the cable based on a current value;

  Also, the cable theft detection method of this embodiment is such that a solar panel is connected to the DC input side via a cable, a power system is connected to the AC output side, and DC power input from the DC input side is converted to AC power. A method of detecting theft of a cable connected to a power conditioner having an inverter for conversion, the step of applying a DC voltage to a DC side circuit including the cable by a voltage applying means, and a current detector to the DC side circuit A step of measuring a flowing current, a step of detecting a disconnection of the cable by determining that the DC current value measured by the disconnection detection processing unit is equal to or less than a set value, outputting a disconnection detection signal, and the disconnection detection signal And outputting a warning output based on the above.

  According to the present embodiment, it is possible to detect theft of the power transmission cable of the photovoltaic power generation system reliably and quickly by applying a voltage to the DC side circuit including the cable and detecting the current flowing through the circuit. And the cable theft can be prevented by detecting and notifying the disconnection of the cable at night when the output power of the solar battery is lost.

  The detection method described in the first embodiment cannot be detected when the power supply to the power supply circuit 16 is interrupted, such as when the system breaker 13 is interrupted when the cable is stolen. The second embodiment is provided with a countermeasure for that. While the power is supplied to the power supply circuit 16, a signal is always output from the power supply detection output terminal 9, and when the cable is disconnected or the system breaker 13 is connected. An alarm means is provided to notify the user of an abnormal condition of the power conditioner when the signal from the power supply detection output terminal 9 is interrupted at the time of interruption. Specifically, an alarm unit such as a display unit or an alarm unit may be connected to the power detection output terminal 9 so that an abnormality is notified when the signal from the power detection output terminal 9 is interrupted.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Solar power panel 2 ... Electric power system 3 ... Connection box 4 ... Diode 8 ... Alarm output terminal 9 ... Power supply detection output terminal 11 ... Insulation transformer 12 ... AC side MC (Magnetic Contactor)
DESCRIPTION OF SYMBOLS 13 ... System side breaker 14 ... DC side breaker 15 ... DC part capacitor 16 ... Power supply circuit 17 ... Current detector 18 ... DC side MC
DESCRIPTION OF SYMBOLS 19 ... Switch 20 ... Reactor 21 ... Inverter part 22 ... DC voltage conversion circuit 23 ... DC voltage application switch 30 ... Disconnection detection processing part 31 ... Circuit drive determination part 32 ... Comparison calculating part 40 ... Control circuit 41 ... Alarm output circuit

Claims (11)

A solar inverter is connected to the DC input side via a cable, a power system is connected to the AC output side, and a power conditioner having an inverter that converts DC power input from the DC input side into AC power,
Voltage application means for applying a DC voltage to a circuit on the DC side including the cable;
A current detector for measuring the current flowing in the circuit on the DC side;
A power conditioner comprising: a disconnection detection processing unit that detects disconnection of the cable based on a direct current value measured by the current detector. In the power conditioner of Claim 1,
The disconnection detection processing unit is a power conditioner that determines that a DC current value measured by the current detector is equal to or less than a set value and outputs a disconnection detection signal. The inverter according to claim 1, further comprising:
A power conditioner comprising an alarm output circuit that outputs an alarm output based on a disconnection detection signal of the disconnection detector. In the power conditioner of Claim 3,
The warning output is a power conditioner that represents theft of the cable. In the power conditioner of Claim 1,
The voltage application means includes a DC side MC inserted in a DC side circuit, a DC voltage conversion circuit that converts a power source on the system side into a DC voltage, and a DC voltage that is an output of the DC voltage conversion circuit. A power conditioner comprising a DC voltage application switch applied to both ends of the side MC. In the power conditioner of Claim 5,
The voltage applying means is a power conditioner further comprising a series circuit of a reactor and a switch connected between the P (+) side wiring and the N (−) side wiring of the DC side circuit. The inverter according to claim 1, further comprising:
A power conditioner comprising a circuit drive determination unit that detects a decrease in DC voltage of a DC capacitor provided on the DC side of the inverter and outputs a DC voltage application command to the voltage application means. The inverter according to claim 1, further comprising:
A power conditioner provided with an alarm means for detecting power supply to a power supply circuit of the power conditioner and notifying the abnormal state of the power conditioner when the power supply is interrupted. A solar panel is connected to the DC input side via a cable, a power system is connected to the AC output side, and a cable connected to a power conditioner having an inverter that converts DC power input from the DC input side to AC power. A theft detection method,
Applying a DC voltage to the DC side circuit including the cable by means of voltage application;
Measuring a current flowing in the circuit on the DC side with a current detector; and
A step of determining that the measured DC current value is equal to or less than a set value by the disconnection detection processing unit, detecting disconnection of the cable, and outputting a disconnection detection signal;
Outputting an alarm output based on the disconnection detection signal;
Theft detection method for cables connected to inverters equipped with The cable theft detection method according to claim 9, further comprising:
A method of detecting a theft of a cable connected to a power conditioner, comprising: detecting a drop in a DC voltage of a DC capacitor provided on the DC side of the inverter and outputting a voltage application command to the voltage application means. The cable theft detection method according to claim 9, further comprising:
A method of detecting theft of a cable connected to a power conditioner, comprising: detecting power supply to a power supply circuit of the power conditioner and notifying an abnormal state of the power conditioner when the power supply is interrupted.

Images