Design Optimization of Transformerless Grid-Connected PV Inverters Including Reliability

Abstract

This paper presents a new methodology for optimal design of transformerless photovoltaic (PV) inverters targeting a cost-effective deployment of grid-connected PV systems. The optimal switching frequency as well as the optimal values and types of the PV inverter components is calculated such that the PV inverter LCOE generated during the PV system lifetime period is minimized. The LCOE is also calculated considering the failure rates of the components, which affect the reliability performance and lifetime maintenance cost of the PV inverter. A design example is presented, demonstrating that compared to the nonoptimized PV inverter structures, the PV inverters designed using the proposed optimization methodology exhibit lower total manufacturing and lifetime maintenance cost and inject more energy into the electricgrid and by that minimizing LCOE.Index Terms-DC-AC power conversion, failure analysis, optimization methods, photovoltaic (PV) power systems, reliability.

Power electronics - the key technology for renewable energy system integration

“…Furthermore, similar to the WTS, reliability is getting more importance in power electronics (including PV systems). This can contribute to extended total energy production and reduced cost of energy [18], [33], [34]. Finally, because of exposure or smaller housing chamber, the PV converter should be more temperature insensitive, which in return is good from the reliability point of view.…”

“…Generally, a Levelized Cost of Energy (LCOE) index is adopted to quantify and compare the cost for different renewables [33], [59], [60]. The possibilities to lower the cost of energy are: a) to reduce the cost for development, capital, operation and maintenance and b) to extend the energy production or increase the lifetime of the generation system.…”

Design for reliability in power electronics in renewable energy systems – status and future

“…Recent research has been devoted to the reliability performance of power electronic components [11]- [12], converters [13]- [15] and systems [16]- [17]. However, the reliability research in the area of power electronics has the following limitations: DFR process discussed in [10] is too broad in focus which could not reveal the specific challenges and new opportunities for reliability design of power electronic systems; over reliance on the value of Mean-Time-BetweenFailures (MTBF) which is found to be inappropriate to most practical cases as discussed in [4] and [18]; and over reliance on handbook-based models and statistics.…”

Design and Implementation of a Three-Phase Active T-Type NPC Inverter for Low-Voltage Microgrids

“…Although various converter topologies have been developed for medium voltage applications, the three-level neutral-point clamped (NPC) converter topology is the most frequently selected for industrial applications due to its advantages of simplicity and reliability [3] [4] [5]. With the advances of modularized power devices developed for the implementation of active T-type NPC inverters [6] [7] [8] [9], AT-NPC inverters are becoming a competitive choice for PV inverters and …”