Single Phase String Inverters
Single-phase string inverter systems convert the DC power generated by the photovoltaic (PV) panel arrays or ‘string’ into AC power fed into a 120 V / 220V single-phase grid connection. The power rating typically ranges from 1 kW up to 8 kW and are mostly used in the residential market.
The main components of the system are the PV panels, the DC link capacitors and the inverter module which handles the DC/AC conversion. Often DC-DC boost stages are used between the PV strings and the DC link. These systems elevate the output voltage of the PV string to the DC link operating level and also run the MPPT (Maximum Power Point Tracking) function, that maximizes the power generated by the PV strings in different environmental and sun irradiation conditions. In situations where the PV string can reach the DC link operating voltage level, the DC/DC converter is bypassed (via a low VF diode) in order to maximize efficiency. Single-phase string inverter systems need to deliver high efficiencies – typically with a target above 97 % (including DC/DC stage) - ensure reliability and be cost optimized.
Architecture and technologies
Single-phase inverter stages are commonly implemented in H-based topologies, either in traditional two-level architecture or in more advanced three-level and multilevel architectures, such as the HERIC or H6. Discrete and integrated solutions are common for single-phase invertes. Power integrated modules (PIM) such as the H6.5 (3-level) - which features 650 V FieldStop 4 Trench IGBTs - simplify the design and manufacture, reduce the thermal dissipation effort and deliver power-dense solutions. Inverters with medium voltage MOSFETs are also an option in some multi-level topologies. Galvanic isolation is very often required for the high side switches, and used often for the low-side as well. Dual-channel gate drivers like the NCP51XXX and NCD5725X offer a simplified and compact solution for your design.
Tailor the design to your needs with ON Semiconductor's versatile portfolio
ON Semiconductor portfolio comprises of both discrete and module solutions, with a full range of power switches including SJ MOSFET, IGBTs, SiC MOSFETs and Schottky diodes. This variety helps you tailor the design to meet the required performance and efficiency at the right cost. Beyond that, you can realize the complete systems with our analog ICs, drivers, opAmps, and current sense amplifiers plus transceivers and wireless connectivity devices.