DE9312710U1 - Modular diagnostic system for the detection and localization of faults in photovoltaic systems - Google Patents

Description

Description
title

Modular diagnostic system for detection and localization
of errors in photovoltaic systems

State of the art

Photovoltaic system technology is characterized by an array (series-parallel connection) of solar modules that are connected to an electrical network and/or one or more consumers via central power electronics. The following errors can occur in the solar generator:

Module: Interruption of an internal conductor track

Severe degradation of cells
Short circuit in the junction box

Diodes (bypass and string): power conduction in both directions

Interruption in both directions

Cabling: interruptions

Short circuits

In previous systems technology, a fault is detected by analyzing the energy yield of the system. This method only allows a statement about the existence of a fault, but only provides very limited information about the type and location of the failure. Certain faults that only lead to a partial failure of the system cannot be reliably detected.

Troubleshooting is carried out manually by taking measurements on site at the solar generator. These measurements can be very time-consuming. In certain systems, e.g. with a building-integrated photovoltaic generator, the measurement variables of interest (module voltage, current through the bypass diode) are difficult to access. In the event of a fault, this leads to long maintenance times, which have a negative impact on the operating result of the system.

influence.

Task

The invention specified in claim 1 is based on the object of creating a diagnostic system that significantly simplifies the detection and localization of faults in photovoltaic generators without requiring additional installation effort in the wiring of the system.

Advantages

Such a diagnostic system reduces the costs of maintaining photovoltaic systems by quickly localizing faults. Improved fault detection enables immediate response to system faults and thus reduces downtime. The energy yield and the utilization rate of the generator are increased in this way.

Further development of the invention

Advantageous embodiments of the invention are set out in claims 2-17.

The design according to claim 1 enables a simple and inexpensive implementation of the decentralized components, which consist only of passive elements and relays.

The further development according to claim 2 enables error detection in large systems through more precise frequency determination, e.g. via a quartz.

The further developments according to claims 3-7 show simple implementation options for a diagnostic system according to claim 1.

The further developments according to claims 8 and 9 show possibilities for generating the characteristic oscillation of the decentralized components for a diagnostic system according to claim 2.

The further developments according to claims 10 and 11 show possibilities for saving energy for the operation of a diagnostic system according to claim 2.

The further developments according to claims 12 and 13 show possibilities in a system according to claim 2 to impress the alternating quantity with the characteristic frequency on the module connections and thus also on the power lines.

The further developments according to claims 14 - 16 show advantageous properties and implementation options of the central evaluation unit.

The further development according to claim 17 shows an advantageous combination of decentralized diagnostic components with an inverter assigned to the respective module, whereby the dual function of the power electronics allows particularly cost-effective implementation options to be expected.

Description of the invention

Figure 1 shows a photovoltaic system with a diagnostic system according to claim 1.

Figures 2 and 3 show possibilities for the implementation of the decentralized components of a system according to claim 1.

The left circuit in Figure 2 corresponds to an implementation according to claim 6. The right circuit in Figure 2 corresponds to an implementation according to claim 4. The left circuit in Figure 3 corresponds to an implementation according to claim 7. The right circuit in Figure 3 corresponds to an implementation according to claim 5.

Figure 4 shows one possibility for implementing the decentralized components of a system according to claim 2.

The left circuit in Figure 4 corresponds to an implementation according to claim 13. The right circuit in Figure 4 corresponds to an implementation according to claim 12.

Figure 5 shows two possibilities for implementing the decentralized components of a system according to claim 2, if the energy processing is also carried out decentrally.

The left circuit in Figure 5 corresponds to a parallel connection of the decentralized diagnostic component with the decentralized energy preparation, while the right circuit shows a functionally integrated overall system according to claim 17.

Claims (1)

4. Protection claims 1. Diagnostic system for error detection and fault localization in photovoltaic systems consisting of at least two decentralized components that are assigned to the modules or module groups or parts of modules (hereinafter referred to as modules) and at least one central evaluation unit that determines and displays errors and failures in the photovoltaic generator based on the information transmitted or received by the decentralized components, where the information is transmitted via the power lines characterized, that the decentralized components consist of frequency-dependent impedances connected to the external connections of the modules, the frequency response of which is characteristic of the respective module and its operating state, and the central evaluation unit carries out an impedance measurement of the power lines over the frequency range of interest in order to obtain information about the state of the system. 2. Diagnostic system for fault detection and fault localization in photovoltaic systems consisting of at least two decentralized components that are assigned to the modules or module groups or parts of modules and at least one central evaluation unit that determines and displays errors and failures in the photovoltaic generator based on the information transmitted or received by the decentralized components, whereby the information is transmitted via the power lines characterized, that the decentralized components consist of active circuits that impress an alternating voltage or an alternating current on the terminals of the module or superimpose it on the direct voltage or direct current of the module, where the frequency or frequency spectrum of the alternating quantity is characteristic of the respective module and its operating state and the central evaluation unit measures the frequency spectrum of voltage and/or current on the power lines and thus determines the operating status of the system. 3. System according to claim 1,
characterized, that the frequency-dependent impedance is formed with a series resonant circuit, which consists of at least one capacitor and one inductance, in parallel with another capacitor, whereby the series resonant circuit is connected to the terminals of the module with the aid of a relay, the excitation coil of which is connected in series with a bypass diode, so that, depending on the connection of the relay, the occurrence or absence of the resonance frequency specific to this module indicates an error and the parallel capacitor allows the analysis of further modules connected in series and a further inductance, which decouples the module from the resonant circuit in terms of alternating voltage, prevents the resonant circuit from being damped by the module. 4. System according to claim 1,
characterized, that the frequency-dependent impedance is formed with a series resonant circuit consisting of a capacitor and an inductance, parallel to another capacitor, whereby the series resonant circuit is connected to the terminals of the module with the aid of a relay whose excitation coil is connected in series with a solar cell, so that depending on the connection of the relay, the occurrence or absence of the resonance frequency specific to this module indicates an error and the capacitor connected in parallel to the resonant circuit allows the analysis of other modules connected in series and a further inductance, which decouples the module from the resonant circuit in terms of alternating voltage, prevents the resonant circuit from being damped by the module. 5. System according to claim 1,
characterized, that the frequency-dependent impedance is formed with a series resonant circuit, which consists of at least one capacitor and one inductance, in parallel with another capacitor, the inductance of the resonant circuit being magnetically coupled via a common core to another inductance, which is connected in series with a bypass diode of the module, in such a way that the core is saturated by a current through the bypass diode and therefore the inductance in the series resonant circuit is reduced, so that the resonance frequency increases, which can be detected by the central evaluation unit, the capacitor connected in parallel with the resonant circuit allowing the analysis of other modules connected in series and a further inductance, which decouples the module from the resonant circuit in terms of alternating voltage, preventing the resonant circuit from being damped by the module. 6. System according to claim 1,
characterized, that the frequency-dependent impedance is formed with a series resonant circuit, which consists of at least one capacitor and one inductance, in parallel with another capacitor, the inductance of the resonant circuit being magnetically coupled via a common core to another inductance, which is connected in series with a cell of the module, in such a way that the core is saturated by a current through the cell and therefore the inductance in the series resonant circuit is reduced, so that the resonance frequency increases, which can be detected by the central evaluation unit, the capacitor connected in parallel with the resonant circuit allowing the analysis of other modules connected in series and another inductance, which decouples the module from the resonant circuit in terms of alternating voltage, preventing the resonant circuit from being damped by the module. 7. System according to claim 1,
characterized, that the solar cells' own capacitance contributes to the formation of the characteristic frequency, for example by forming an oscillating circuit with the help of an external inductance, whereby a shift in the resonance frequency allows conclusions to be drawn about the capacitance and thus about the condition of the respective module. 8. System according to claim 2,
characterized, that the generation of the characteristic frequency of the respective decentralized component is generated with the aid of a quartz oscillator and a digital divider circuit. 9. System according to claim 2,
characterized, that the generation of the characteristic frequency of the respective decentralized component is generated with the help of an analog oscillator circuit. 10. System according to claim 2,
characterized, that the oscillator circuit of the decentralized component is only operated intermittently to save energy, whereby the circuit is expanded to include a corresponding timer part to control this intermittent operation and the evaluation unit takes this intermittent operation into account accordingly. 11. System according to claim 2,
characterized, that the oscillator circuit of the decentralized component is only operated to save energy if the central evaluation unit requests it via a corresponding signal, which is also transmitted via the power lines, whereby the decentralized unit is expanded by a corresponding receiver circuit and the central evaluation unit is expanded by a corresponding transmitter circuit to detect this control signal. 12. System according to claim 2,
characterized, that the oscillation is applied to the module terminals via a suitably controllable circuit breaker which is located parallel to the module terminals, whereby the circuit breaker changes the voltage at the module terminals by controlled or regulated absorption of part of the module current. 13. System according to claim 2, characterized, that the oscillation is applied to the module connections capacitively or with a transformer, whereby the solar cells connected in series can be decoupled from the module connections in terms of alternating voltage via an inductance in order to reduce the necessary alternating power. 14. System according to claim 1 or 2, characterized, that in the absence of irradiation, the central evaluation unit additionally impresses a direct voltage, which can correspond to or be opposite to the polarity of the output voltage of the solar generator, onto the solar generator in order to obtain further information about the system. 15. System according to claim 1 or 2,
characterized, that the central evaluation unit carries out the analysis using digital signal processing methods, e.g. signal processors. 16. System according to claim 1 or 2,
characterized, that the central evaluation unit is structurally and/or functionally integrated into the central power electronics, e.g. the inverter: 17. System according to claim 2,
characterized, that the decentralized component is structurally integrated into an inverter assigned to the module and describes the state of the module through a characteristic variation of the clock frequency of the power electronics, which is recognized by the central evaluation unit.