Solar inverter from Fronius uses CoolSiC MOSFETs

23rd November 2020
Alex Lynn

A few weeks ago Fronius International launched the Symo GEN24 Plus solar inverter which uses CoolSiC MOSFETs. Its Multiflow technology makes it suitable for a wide range of applications supporting energy self-sufficiency. Not only does it provide power for direct use in the household, but it also offers an interface for energy storage systems.

In addition, the hybrid inverter is designed for water heating and the charging of electric cars, and can be connected to external systems.

All this thanks to silicon carbide (SiC) from Infineon Technologies with an efficiency of over 98%. In combination with the high voltage storage from BYD, the Symo GEN24 Plus achieved a record value in the System Performance Index (SPI) of 94% in the 10 kW class. It was the only one in this combination to achieve Class A energy efficiency.

“SiC modules can be used to build very energy-efficient, robust, and reliable inverters,” said Andreas Luger, Head of R&D Power Electronics from the Solar Energy Business Unit at Fronius. “This technology enables a significant increase in switching frequency. Compared to the previous generation, the functionality is significantly improved, while its size remains comparable. Each device now also has an output for a secure power supply, and backup power, in addition to the standard connection options for a hybrid inverter.”

“To maximise the advantages of SiC, engineers from Fronius and Infineon have jointly optimised the layout and chip assembly of the modules,” added Peter Wawer, Division President Industrial Power Control at Infineon. “Ultimately, the close communication between the development teams enabled system advantages that correspond to customer needs. Based on our tried and tested Easy module, the inverter's booster stages now use 1200 V CoolSiC MOSFETs in combination with CoolSiC diodes. This full-SiC solution thus ensures maximum efficiency.”

Full-SiC is also used for the battery stage. One Easy 1B 1,200V with an R DS(on) of 45mΩ is used in the bidirectional DC/DC converter. The inverter stage implements a SiC hybrid solution in an Easy 2B module, which has also been tailored to the needs of Fronius. The NPC1 topology combines silicon-based 650V TRENCHSTOP 5 IGBTs and rapid diodes with CoolSiC Schottky diodes. The modules are controlled in all stages with an EiceDriver IC gate driver.

The combination of SiC MOSFET modules in the booster and battery input with hybrid modules in the inverter stage ensures the best possible ratio of efficiency and cost. As Infineon's SiC power semiconductors have a high power density, the Symo GEN24 Plus from Fronius offers many functions such as backup power, storage connection, multi-MPP tracker, and energy management.

The inverter weighs only 24 kg and has a small volume (594x527x180mm3). Its active air-cooling can reduce the temperature of the power electronics parts, and thus extend service life. The inverter is available in the power classes 6, 8, and 10kW. Fronius supplies this inverter primarily in Europe, South America, and Australia.

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