Abstract
The flyback converter has been widely used in Photovoltaic microinverters, operating either in Discontinuous, Boundary, or Continuous Conduction Mode (DCM, BCM, CCM). The recently proposed hybrid DBCM operation inherits the merits of both DCM and BCM. In this work, the necessary analytical equations describing the converter operation for any given condition under DBCM are derived, and are needed due to the hybrid nature of the modulation strategy during each sinusoidal wave. Based on this analysis, a design optimization sequence used to maximize the weighted efficiency of the inverter under DBCM is then applied. The design procedure is based on a power loss analysis for each converter component and focuses on the appropriate selection of the converter parameters. To achieve this, accurate, fully parameterized loss models of the converter components are implemented. The power loss analysis is then validated by applying the optimization methodology to build an experimental prototype operating in DBCM.
Highlights
A hybrid discontinuous/boundary conduction mode (DBCM) modulation, which aims to combine the individual advantages of Discontinuous Conduction Mode (DCM)
As will be shown due to the two different operating modes that exist within a sinusoidal wave half cycle, as well as because of the variable switching frequency imposed by the i-BCM operation during a segment of the sinusoidal wave, complex mathematical manipulations need to be carried out in order to derive precise equations for the DBCM operation during the full sinusoidal period
The achieved weighted efficiency is always higher than the one of the converter operating in pure i-BCM, underlining the performance benefit of the flyback inverter designed for DBCM
Summary
Distributed power generation in residential areas using solar panels has seen great progress during the last decade, to the point where the module-level microinverters are a strong alternative solution to central inverters, due to their improved energy harvest, ease of installation, modularity, and flexibility [1,2,3,4]. A hybrid discontinuous/boundary conduction mode (DBCM) modulation, which aims to combine the individual advantages of DCM and i-BCM, has been proposed and analyzed [22]. Rms current equations of Inthis thispaper, paper,the thederivation derivationof of the average and rms current equations ofall all the conIn the derivation ofthe theaverage average and rms current equations of the all conthe verter key components for operation in is analytically described. The derived formulas, as well as the inverter specifications and constraints, are integrated into an optimization algorithm, created for DBCM, which determines the component design values. The application of this methodology is afterwards evaluated on a laboratory experimental prototype. The converter efficiency is compared to a flyback inverter with equivalent characteristics, designed for operation in i-BCM
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