3-phase string inverter solutions
String inverters perform power conversion on series-connected photovoltaic panels, usually, these inverters are rated around a few kilowatts up to 200 kilowatts. String inverter typically relies on two-stage power conversion. In general, most of the inverter designs are transformer less or non-isolated.
First DC-DC stage converts variable DC voltage into a fixed DC voltage, at the same time ensures maximum power been extracted from PV panel via MPPT (Maximum Power Point Tracking) technique.
DC-AC stage converts DC power into grid compatible AC power. Either level 2 or level 3 topology is preferred in this stage. In particular, level 3 topology is widely used for its higher efficiency. Mainly for 1000 V PV array system, Level 3 NPC1 / NPC2 is preferred. Level 3 NPC1 enables to use of 600 V devices and allows more than 20 kHz switching frequency operation even for oversized PV panel. Level 3 NPC2 uses both 600 V and 1200 V device, the best fit topology for less than 20 kHz switching frequency operation. For the 1500 V PV system, Level 3 ANPC is widely used for its higher cosmic ray and its higher efficiency over the full range of power factor operation. The size and weight of the inverter highly depend on the AC filter and cooling system, the higher switching operation is desirable to reduce the size and cost of the system.
Infineon offerings for designs up to 200 kW
In commercial and utility-scale applications, inverter design ranges from 20 kW to 200 kW. It is possible to achieve the best in class power density and high ease of manufacturing by using Infineon’s module products. This includes our CoolSiC™ Easy Module and 3-level Easy module. All switches need a driver and all drivers need to be controlled. That is why we also offer the right EiceDRIVER™ gate driver as well as the XMC™ microcontroller for your inverter design. Finally, each functional block needs a sensor and auxiliary power supply, which is why we offer CoolSET™ and the TLI4971 current sensor.
Choosing the right solution for your 3-phase inverter design results in a combination of sophisticated digital control technology with efficient power conversion architecture to achieve excellent solar power harvesting and reliability. There are several main topologies used in the power stages of 3-phase string inverters. All of these topologies can be equipped with a booster stage to achieve a wide input voltage range and the opportunity to implement the MPPT algorithm.
Find the right products for your design topology within Infineon’s industry-leading power portfolio:
Trends and requirements of 3-phase string inverters
Lightweight String inverters are gaining popularity in these markets up to 20 MW. They enable great design flexibility, easy transportation and are also quickly and easily replaced by two persons with a few clicks.
Based on our deep application know-how in solar and related industries, we can reduce learning cycles and provide fast customization through proven short flow processes. In combination with the strength of Infineon’s 1200 V CoolSiC™ MOSFET and TRENCHSTOP™ IGBT7 and EiceDRIVER™ galvanically isolated gate drivers enable our customers not only to reduce system and operational cost significantly but furthermore help to harness never before seen levels of efficiency and power density.
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