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2000
Conference Paper
Titel
Hochfrequenzeigenschaften von photovoltaischen Generatoren - Die Ausbreitung von Funkstörungen in Photovoltaikanlagen
Alternative
High-frequency characteristics of photovoltaic generators - the propagation of radio interferences in photovoltaic systems.
Abstract
Die vom Leistungsteil eines PV-Wechselrichters erzeugten hochfrequenten Störsignale können sich im Fehlerfall über die angeschlossenen Leitungen ausbreiten. Dies kann zu hochfrequenten Störströmen auf Gleichspannungsleitungen von Photovoltaik (PV)-Generatoren führen, die unter Umständen Probleme bezüglich der elektromagnetischen Verträglichkeit (EMV) in benachbarten elektronischen Systemen hervorrufen. Die Störströme auf den Gleichspannungsleitungen werden im wesentlichen durch die hochfrequenten Impedanzeigenschaften der Komponenten auf der Gleichspannungs (DC)-Seite beeinflußt. Im Rahmen des europäischen Projekts ESDEPS wird am ISET das Impedanzverhalten von photovoltaischen Generatoren mit Mitteln und Methoden der Hochfrequenztechnik untersucht. Mit Hilfe dieser Untersuchungen soll ermittelt werden, unter welchen Bedingungen sich Funkstörungen auf der DC-Seite ausbreiten können. Das Ziel ist schließlich Maßnahmen abzuleiten, die die Störsignalausbreitung unterbinden und die EMV auf der DC-Seite von PV-Anlagen sicherstellen.
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In the case of defects in photovoltaie (PV) inverters high frequency disturbances generated in the power electronics part can propagate in cables connected to the inverter. This may lead to high frequency interference currents in DC cables of PV generators which possibly cause problems regarding the electromagnetic compatibility (EMC) of adjacent electronic systems. Systems like communication equipment in the vicinity of the PV system are potentially affected by means of radiated and field coupled interferences. Interference currents on DC cables are mainly influenced by high frequency impedance characteristics of the components on the DC side. Within the scope of the European project ESDEPS (Electromagnetic Compatibility and Safety Design for Photovoltaic Systems) the impedance properties (i.e. the complex input impedance) of PV generators is investigated by means of methods and measurement techniques of high frequency engineering. In this investigation the PV inverter is considered as RF source. It delivers the maximal power to a load in the case of power matching. The load consists of DC cables and the PV generator. With the aid of these investigations, it should be determined under which conditions interferences can propagate on the DC side. Therefore the high frequency properties of components on the DC side must be characterised. Within these investigations the impedance of PV cells at frequencies from 300 kHz to 3 GHz and of PV modules from 300 kHz to 300 MHz are determined by means of measurements. With exception of a single resonance at 270 MHz the real part of the PV cell is low-impedance. The imaginary part is mainly caused by the inductive lead wire and the conductor configuration on top of the PV cell. In contrast to this, the impedance of a PV module shows a great number of resonance points because of several series connected PV cells. Series and parallel resonances alternate. In addition to the measurements numerical simulations of the high frequency characteristics of PV modules have been performed by means of the program package CONCEPT II.
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