Abstract
It is required to reduce the cost of PV energy to be competitive as an alternative energy source. The efficiency and reliability of PV inverters are important aspects to be enhanced to reduce the cost of PV energy since they contribute to the reduction of operational and maintenance costs and to the increase of annual energy production. Therefore, more comprehensive analysis on both efficiency and reliability together including the impacts of various factors is required. In this paper, single-phase five-level NPC inverter topologies for photovoltaic systems are comparatively evaluated in terms of efficiency and reliability by simulations and experiments, in which the impacts of pulse width modulation (PWM) methods and installation locations are considered. The results are expected to give an insight to determine the proper topology and PWM method depending on its installation location considering the reliability as well as the efficiency and total harmonic distortion (THD).
Highlights
Renewable energy based electricity generation is rapidly growing in the last decade to replace fossil fuels for reducing carbon emission
If it is assumed that the required B1 lifetime is 20 years and the reliability and efficiency are emphasized, the T-type NPC inverter is not recommended for the mission profile in Iza due to the relatively low B1 lifetime under both UP-pulse width modulation (PWM) and one-pole clamping pulse width modulation (OPC-PWM) even if it has the highest efficiency especially when the one-pole clamping (OPC)-PWM is applied
The efficiency and lifetime of single-phase fivelevel I-type and T-type NPC inverters are comparatively evaluated with two PWM methods under the mission profiles from Iza and Aalborg
Summary
Renewable energy based electricity generation is rapidly growing in the last decade to replace fossil fuels for reducing carbon emission. In [6], [21], asymmetric single-phase five-level Ttype and I-type NPC inverters have been proposed, where one T-type leg and one I-type leg are replaced with halfbridge leg, respectively These topologies reduce the number of power devices and improve the efficiency compared with conventional I-type and T-type NPC inverters. The comparative performance analysis of single-phase five-level PV inverters is performed by considering the impacts of topology, pulse width modulation method and installation location. The lifetime evaluation of NPC inverters with two PWM methods under different locations are performed first at component-level and system-level reliability assessment is carried out The efficiency of both inverters depending on the PWM methods at different switching frequencies and power levels are analyzed and verified by experiments with prototype PV inverter systems
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