20 SOLAR POWER www.panasonic.com/global/industry/ Issue 3 2023 Power Electronics Europe www.power-mag.com Eco-friendly choices shine through for clean energy As the world moves towards making more eco-friendly responsible choices, the demand for sustainable and renewable energy has driven consistent high growth in the solar inverter market. By Panasonic Industry. A solar inverter (also called a photovoltaic or PV inverter) converts direct current (DC) into alternating current (AC), and is widely used in solar photovoltaic power generation systems. Solar inverters available today are generally divided into three types: central inverters, string inverters and micro inverters. Central inverters are mainly used in large-scale ground power stations, suitable for high voltage grid connection. The power range is normally between 100kW and 2500kW. String inverters, also known as distributed inverters, are mainly used in industrial, commercial and residential areas. Power stations that use string inverters are not generally very large, and they are integrated into the national supply through full or surplus power grid connection. Power range is normally up to 200kW. String inverters are most commonly used and encountered in our daily lives. Micro inverters are mainly used for direct integration on battery boards, that are suitable for small household power stations. Standard film capacitors Film capacitors can optimise the design of string inverters. Regardless of the type of solar inverter, the key requirements are high efficiency, high reliability and input voltage with a wide range of capacitance values. Metallised PP(polyproylene) film capacitors can play an essential role in a solar inverter’s circuit design because they feature a large current handling ability, high reliability and proven safety performance. They can be used for I/O filtering, EMI suppression, snubber and DC link circuits. On the input side of the primary DC filter circuit as well as for the DC-link circuit, DC-rated film capacitors provide DC filtering. For example, parts with voltage ratings of up to 1300V DC and a wide capacitance range of up to 110 F are available as one single component in Panasonic’s EZPV series; both two-pin and four-pin terminal devices are available. On the input side of the DC/DC converter circuit, as well as in snubber circuits, capacitors such as Panasonic’s DCrated ECWFD series (coating type), ECWFE and ECWFG (box type) film capacitors, are suitable for smoothing. Various rated voltage values are available from 450V DC up to 1100V DC with a capacitance range from 0.01 F to 12 F. The built-in fuse provides safety performance which, together with high frequency characteristics and high ripple current capacity help film capacitor devices to optimise the high voltage circuit of a solar inverter. Film capacitors with a higher rated voltage of 250 to 600V AC, for example Panasonic’s AC-rated EZPQ industrial-grade AC capacitors, can be used as an output filter. Reliability - especially in humid conditions - is critical for solar inverters which are used outdoors. To achieve high humidity resistance, for example, Panasonic has developed enclosure sealing technology and 100% aluminium vapour deposition processes (Figure 2). Polymer aluminium capacitors Conductive polymer solid aluminium capacitors play a major role in the optimisation of solar inverters. To efficiently generate energy from the sun, the solar panel must absorb energy from the sun Figure 1: Structure of patterned metallisation (fuse function). Figure 2: Aluminium for metallisation and vacuum control contribute to the capacitor seal.
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