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SOLAR INDUSTRY AWARDS I WINNERS


PV BALANCE OF SYSTEM


VarioString: Isolated Dual Channel High Voltage MPPT VARIOSTRING is a high power, isolated, dual channel MPPT solar charge controller for off-grid systems and battery based energy management systems up to 105kW. It is compatible with all battery technologies (lead-acid, lithium-ion, NiCd, etc.) due to its programming options for the charge cycle. Its fast and accurate algorithm ensures an MPPT efficiency of more than 99%.


The ability to arrange the dual MPPT inputs independently or in parallel (with max 600Voc) or in series (with max 900Voc) allows the VarioString to be used in a wide variety of PV configurations. While battery based MPPT solar charge controllers are typically used for off-grid applications, increasingly the DC-coupling of PV is used in battery based energy management systems with connection to the grid to increase system stability and system efficiency for energy consumed when the sun is not shining.


The VarioString responds to the need to decrease BOS costs, increase flexibility and modularity of BOS components and at the same time increases system performance and overall energy yield. The VarioString has been designed to meet the needs of battery based management systems. The high voltage DC input allows for longer


The VarioString allows for up to 900 Vdc maximum open circuit voltage with the dual MPPT inputs in series, which is the highest PV voltage allowable of any device in its class.


The VarioString responds to the toughest requirements in efficiency in solar installations. It also reduces the system costs by accepting PV strings up to 600 or 900Vdc. This allows for a more simple installation and reduces the installation time and material costs: reduction in cable cross-section and length, absence of junction box and string fuses.


Julie Studer, Comms Designer at Studer


strings of PV modules, much like is common with standard grid-tie inverters, which decreases the BOS costs and greatly simplifies installation. The fully programmable 4-step battery charger extends the life of batteries which reduces O&M costs and the amount of batteries being disposed of. The VarioString makes it possible to create flexible residential PV systems with only one device. Studer had the forethought to create a product with high power and high efficiency for different PV arrays.


42 www.solar-international.net I Issue V 2014


The VarioString contains dual MPPT inputs for a total flexibility in PV array configuration (in series, in parallel or independent). It allows for up to 900 Vdc maximum open circuit voltage with the dual MPPT inputs in series, which is the highest PV voltage allowable of any device in its class.


The VarioString has 120A max battery charge current.


It has the capability of connecting up to 15 PV panels in parallel on the same battery bank for a total PV array capacity of up to 105 kWp. The full isolation between PV and battery allows for any grounding scheme.


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