The Genesis chip is an IGBT module co-developed with, and produced by, Vishay for use in photovoltaic systems in private homes. The module is used as the power unit in inverters for converting the DC voltage generated by the solar cells into AC voltage that can be fed into the grid. The big players in the inverter industry use patented technologies in the power unit, but there are also numerous not-so-large inverter manufacturers who do not use patented topologies. It is precisely these companies, which rely on standard topologies, that traditionally struggle to keep up with the big companies because of the challenge of meeting market requirements in terms of efficiency while simultaneously achieving a very high level of reliability.
Genesis is designed to enable these companies to compete better, with only minimal software changes required in order to integrate Genesis into an existing solution. The solution employs a standard boost topology with a bridge configuration. For the casing, EBV and Vishay consciously opted for a well-proven technology in the form of the ECONO2 (Econopack 2). Although cheaper casings than ECONO2 are available, which are also used in some of the latest generation of inverters, there is another important element that has to be factored into the equation, namely that the Econo2 casing permits an exceptionally high level of reliability. Since end customers base their calculations of the amortisation period for their photovoltaic systems on a functional period of more than 10 and sometimes even more than 20 years, it is unacceptable for them to have to exchange the inverter after only five or six years.
Background
The basic idea of Genesis involves offering inverter developers a solution that is extremely easy to use, which they can integrate into their existing design within the scope of a migration path and without major effort, and that works with a high level of efficiency and reliability, whilst offering good electromagnetic compatibility. The success of Genesis in meeting these targets can be gauged by the fact that over 50 prospective customers in Europe, who could use this RoHS-compliant module, have already expressed serious interest, from Spain to Turkey and from Italy to Germany through to Eastern Europe. EBV defined the design initially with one key account customer, whereas the subsequent fine tuning ensued in close collaboration with several customers and developers from Vishay.
EBV developed Genesis for designs in which six-pack modules are already used. Many of the target customers already had ideas as to what they required, but the high NRE costs of a customer-specific design halted implementation. It is precisely here that the performance of the EBVchips comes into play, since Genesis is not designed for one customer only and not just for one national market, but can be used the world over.
EBV supplied the first samples without a built-in thermistor as a means of thermal protection, since most customers did not want this functionality. Nevertheless, EBV is capable of developing variants with a built-in thermistor within the space of two months. Since the responsible engineers at the Vishay and EBV factories communicate with each other via a direct communication channel, EBV insists it is possible to make changes to the design in real-time.
Technical data
Genesis is a complete power unit integrated into one module for single-phase inverters in photovoltaic applications. With its ratings of 600 V/50 A (in continuous operation) for a conversion frequency of 4 to 30 kHz, Genesis is targeted at applications in the residential sector, which mostly have a power rating of between 2,5 and 6 kVA.
The choice of semiconductor devices integrated into the module were chosen with an eye towards an extremely high-quality end product. For instance, the trench IGBTs, with their low collector to emitter saturation voltage of just 1,65 V, constitute a very desirable compromise between conduction and switching losses, whilst the silicon carbide diodes ensure particularly low switching losses and, at the same time, excellent EMC performance, since the blocking interval recovery time of SiC diodes is zero, such that the additional snubbing required can be significantly less than with conventional solutions.
The FRED silicon diodes act in turn as a boost bypass in the case of high input voltages, such that the module is provided with an effective means of protection against reverse polarity of the solar panels. As such, Genesis is ideally equipped for use in boost stages, which implement the concept of ‘maximum power point tracking’ of the photovoltaic modules with a downstream single-phase bridge for DC/AC conversion.
Genesis’ Econo2 casing, although not the cheapest, exhibits excellent electrical and thermal properties. With its solid copper base plate, the low thermal resistance between the chip and the casing improves the thermal performance, which is then further enhanced by being installed directly on the heatsink. Furthermore, the installation of a module is much easier than the installation of individual components, which boosts reliability and lowers system production costs.
EBV did not design Genesis to be the cheapest solution on the market, but rather focused on making it cost-effective. Since the cost of the IGBT module is fairly small proportionate to the cost of the whole inverter, EBV believes that a more efficient and reliable solution in a better casing represents the cheaper option at the end of the day. Consequently, it does not view this as a low-cost migration solution, but a migration towards higher performance coupled with higher efficiency.
For more information contact EBV Electrolink, +27 (0)21 402 1940, capetown@ebv.com, www.ebv.com
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