A wireless controlled circuit for PV panel disconnection in case of fire P. Guerriero, F. Di Napoli, V. d’Alessandro, S. Daliento Department of Electrical Engineering and Information Technology(DIETI), University of Naples Federico II, via Claudio 21, 80125 Naples, Italy. Phone: +39-081-7683122; e-mail: daliento@unina.it Abstract— This paper propose a new system to short circuit a photovoltaic panel, embedded in a photovoltaic string, with the aim to ensure safe operation of firemen in case of fire. The circuit is activated by a wireless command and doesn’t require additional wiring. Moreover it is self powered by the solar panel itself and can be either turned on or turned off in a fully reversible way. Keywords—fire protection, arc detection, monitoring, reconfigurable systems I. INTRODUCTION During the last decade photovoltaic technology reached full commercial maturity and its worldwide diffusion increased dramatically. Despite that, an unsolved, potentially harmful, security risk still exists. It comes from the topology of photovoltaic (PV) systems which require series connection of PV modules, thus forming PV strings, in order to reach the DC output voltage suitable for DC/AC converters. A high voltage of several hundred Volts is usually present at the string terminals; such a voltage is generated by the photovoltaic effect and cannot be switched off as long as sunlight reaches the PV string. There is a twofold drawback of this fact. The first drawback concerns the possible occurrence of voltaic arc, whose activation is the first cause of fire setting in PV plants. PV plants should be provided of reliable arc detection systems able to immediately and automatically extinguish the voltaic arc by resetting the string voltage in order to prevent fire propagation. However, even if the voltaic arc could be correctly detected, the reset of dangerous voltages could be achieved, for each point of the PV field, only if all solar modules were individually short circuited. The second drawback arises when, unfortunately, fire takes place. In this case the effective action of firefighters to tackle the blaze is prevented by the presence of dangerous voltages. There are few solutions right now. The Italian standard CEI 8225 V1 [1] says that “it is impossible to keep the system with no voltage under sunlight” and only requires the presence of information plaques at a distance of five meters each others to advise for potential risks. The above statement is not completely true. Some companies developed highly sticky foams [2] indeed which should be spread over PV panels to obscure them; unfortunately they are difficult to remove and may bring to the irreversible damaging of PV panels. In any case too much time is required to keep safe conditions. Recently, a more reliable approach has been proposed [3], it consists of a remote controlled relay which is mounted in parallel to each module and can be activate by pressing a devised main switch. The system is really effective but requires separate wiring schemes providing power supply and data communication. Thus, the number of wires in the PV plant increases. Active by pass devices [4,5], which are three terminal electronic devices that can be used instead of the conventional two terminal by-pass diodes, to reduce dissipated power, could be used as well but require special driving schemes. In a recent paper [6] features which should be accomplished by a reliable firefighter safety system have been revised and discussed according to the German Association for Electrical, Electronic & Information Technologies (VDE) application guide “VDE-AR-E 2100-712:2013-05 [7]. The following criteria for a reliable system were individuated: 1. Immunity to over-currents due to dc capacitor 2. Safe PV module voltage after disabling. 3. Low conduction losses. 4. Possibility of individual module bypassing 5. Cost efficiency. In [6] it was concluded that none of the existing solutions fulfills all criteria. In this paper we propose an innovative single panel short- circuiting system which both fulfills all above requirements and adds further new properties. The system exploits a parallel relay which is activated when a wireless command opens a MOSFET which is connected in series to the solar panel, thus the panel supplies both zero voltage and zero current. The system doesn’t require new wiring and can be easily installed on existing plants; morever it is fully self powered by a supercapacitor harvesting stage. It is fully reversible as well, in the sense that each module can be individually either disconnected or reconnected. The paper is organized as follows. In Section II the operating principle is described through circuit level simulations performed in the PSpice environment. In Section III the harvesting stage is described and experimentally tested on a prototype board. In Section IV experiments performed on a test PV field are shown. Conclusions are drawn in Section V. 978-1-4799-4749-2/14/$31.00 ©2014 IEEE 2014 International Symposium on Power Electronics, Electrical Drives, Automation and Motion 982