DE102007031785A1 - Method and circuit for monitoring solar panels for theft - Google Patents

Abstract

The invention relates to a method and a circuit for monitoring individual solar panels in solar systems on theft. It is an addition to the patent application DE 102006049285.4 and allows the simultaneous monitoring of several parallel-connected solar panel strings. For this purpose, during the night operation of the solar system to the parallel circuit of the strings a larger compared to the output voltage of the solar system voltage with reverse polarity (Reversspannung) created. According to the invention, the sum of the currents flowing through the parallel-connected strings is monitored by means of a Wheatstone bridge. The circuit for carrying out the method has three voltage divider resistors (14, 17, 18), a trimmer (16) and a bridge resistor (15), which are connected together with the parallel connection of the strings (8.1) to form a Wheatstone bridge. A voltage divider point (20) of the bridge circuit is connected to the input of a voltage comparator (9). When a solar panel is stolen, the voltage at the voltage divider point (20) changes and the voltage comparator (9) activates an alarm reporting system (12). In addition, the circuit allows long-term monitoring of the total impedance of the solar system.

Description

The invention relates to a method and a circuit for monitoring solar panels for theft; it is an addition to the patent application DE 10 2006 049 285.4 , It enables the simultaneous monitoring of several parallel strings, ie series connections of solar panels.

In DE 10 2006 049 285.4 discloses a method for monitoring of solar panels on theft, according to the voltage applied at night or in idle mode to the series connection of the solar panels, which is referred to as a string, with a reverse polarity compared to output voltage of the solar system and the current flowing through the string is monitored. In case of a theft of a solar panel, the series connection of the string is interrupted. This leads to a reduction in the flow of current through the string and, as a result, to the triggering of an alarm.

to technical implementation of the method is also a Circuit for monitoring the solar panels for theft suggested that from a resistor that comes with the solar panels String is connected in series, and a voltage comparator circuit whose two inputs are connected to the series resistor for the purpose of measuring the voltage drop across it, connected in parallel are. If the voltage drops across the resistor due to the theft from a solar panel, turns on the voltage comparator circuit a relay located at its output, which in turn means a potential-free switching contact triggers an alarm message.

The However, most solar systems do not just consist of a solar panel String. Typically, in a plant three to five Strings connected in parallel. To these strings with the above Monitoring circuit would be equivalent to three to five separate monitoring circuits necessary which leads to a high material and circuit complexity would.

task The invention is simultaneously with a monitoring circuit monitor several parallel solar panel strings for theft.

These The object is achieved by the characterizing Features of claims 1 and 3 solved; advantageous Embodiments of the invention or an advantageous uses emerge from the claims 2, 4 to 6.

As already shown, when the output voltage of the solar system a predefined voltage limit, e.g. B. 42 V, below, so typically at night, compared to each string one to the output voltage greater voltage with reverse Polarity applied, whereby the series-connected power semiconductors, typically Schottky diodes, in the junction boxes of the solar panels be operated in the forward direction.

To According to the present invention, the sum of monitors several strings in parallel flowing currents.

in the Unlike monitoring a single string, at the theft of a solar panel to the full Interruption of the circuit results in several parallel strings only one of the strings formed by the strings Current paths interrupted. The resulting resistance or Voltage change is therefore much smaller and can can only be detected by very sensitive measuring circuits. Preferably This is a Wheatstone bridge, the circuit-technical Is calibrated to a non-zero voltage, used.

The Circuit for carrying out the method consists of a Test module, which is the application of voltage to the solar panel Strings serves a power monitoring device and an alarm unit. According to the invention resistor formed by several strings connected in parallel with three more voltage dividing resistors and one Bridge resistance in a Wheatstone bridge arrangement connected. One of the voltage divider resistors is as Series connection of a trimmer (potentiometer) and a fixed one Resistance performed. The bridge resistance is between the two voltage divider points of the Wheatstone bridge.

At one of the two voltage divider points of the bridge is a Voltage comparator connected. In addition, the trimmer adjusted so that the voltage at this voltage divider point only slightly different from the reference voltage of the voltage comparator differs. Theft of a solar panel changes the voltage at the voltage divider point, the voltage comparator switches and solves by means of a located at its output side Message unit an alarm.

Around the test current depending on the number of monitored Being able to set strings is the test module Advantageously equipped with a constant current source, the over an adjustment of the current to integer multiples a base value. The size of the Current is always at the base value times the number of checks To set strings.

at The solar systems used today are three to maximum operated five strings in parallel. That's why the circuit is for economic reasons to three to a maximum of five Strings designed.

By Measuring the voltage drop at the Wheatstone bridge In addition, there is a long-term monitoring of the system total impedance in the powerless state, d. H. at night or with strong shading, possible. For intact diodes, the variance is the voltage drop an indication of increasing contact resistance in cables, plugs and solar panels as a result of pollution, Corrosion, partial damage u. Ä. The early Detecting the impedance change allows a promptly eliminating the causes, causing creeping reductions the performance of solar systems and expensive consequential damage can be avoided.

The Invention will be described below with reference to an embodiment explained in more detail; to show this in more schematic Presentation:

1 : a circuit for monitoring multiple strings

1 shows the three voltage divider resistors 14 . 17 . 18 and the bridge resistance 15 constructed Wheatstone bridge circuit. The fourth voltage dividing resistor 8.1 is formed by the parallel connection of the solar panel strings. Besides, the solid resistance is 17 in series with the trimmers 16 switched, whereby an adjustable voltage divider resistor of the bridge is formed.

Due to the small resistance of the grounded resistor 14 of 51 Ω in combination with the high resistance of the bridge resistor 15 of 1 MΩ, the following circuit components will precede the series connection of the solar panels 8.1 protected voltage peaks protected. Prolonged overvoltages lead to a melting of the fuse 19 ,

The voltage comparator 9 is with the voltage divider point 20 connected. Impedance changes of the parallel connection of the strings 8.1 cause a voltage change proportional to this impedance change at the voltage divider point 20 , In order to enable a sensitive response of the voltage comparator and the triggering of the alarm, the voltage at the voltage divider point must be 20 with the help of the trimmer 16 be set to a value which, depending on the operation of the comparator (exceeding or falling below the reference voltage) slightly smaller or larger than the reference voltage of the voltage comparator 9 is.

8.1

parallel connection the series resistances of the strings

9

voltage

12

Theft alarm notification system.

13

Constant current source

14

second Voltage divider resistor

15

bridge resistance

16

Trimmer / Potentiometer

17

third Voltage divider resistor

18

fourth Voltage divider resistor

19

backup

20

Voltage dividing point

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102006049285 [0001, 0002]

Claims (6)

Method for monitoring solar panels in solar systems for theft according to DE 10 2006 049 285.4 in which, when the output voltage of the system falls below a predefined voltage limit in the range of 1 to 60 V, a greater voltage compared to the output voltage with reverse polarity is applied to the series connection of the solar panels, which power semiconductors in boxes, the electrical connection of the Serving panels, operated in the forward direction, and the current flowing through the series connection of the panels is monitored, characterized in that the sum of the currents flowing through a plurality of parallel strings is monitored. Method according to claim 1, characterized in that that the sum of the strings flowing through the parallel strings Streams using a Wheatstone bridge, the is balanced to a voltage not equal to zero, monitored becomes. Circuit for carrying out the method according to claim 1 and 2, which consists of a test module, which serves to apply the voltage to the solar panel strings with a reverse polarity compared to the output voltage of the solar system, a current monitoring device and an alarm signaling unit ( 12 ), characterized in that the resistor formed by a plurality of parallel strings ( 8.1 ) with the second and third voltage divider resistor ( 14 . 17 ), with the series connection of the fourth voltage divider resistor ( 18 ) and the trimmer ( 16 ) as well as with the bridge resistance ( 15 ) are interconnected in a Wheatstone bridge arrangement and the input of a voltage comparator ( 9 ), at whose output an alarm signaling unit ( 12 ) is connected to a voltage divider point ( 20 ) of the Wheatstone bridge, the trimmer ( 16 ) is adjusted so that the voltage at the voltage divider point ( 20 ) slightly different from the reference voltage of the voltage comparator ( 9 ) deviates. Circuit according to Claim 3, characterized in that the test module is a constant current source ( 13 ), which has an adjustment possibility of the current to integer multiples of a basic value, which serves to adapt the total current to the number of parallel-connected strings. Circuit according to Claims 3 and 4, characterized that three to five strings are connected in parallel. Circuit according to Claims 2 to 5, characterized that they provide long-term monitoring of the total impedance the solar system is used.