The question is what scheme of conduction to be used for PV grid tied flyback inverter. Either the Discontinous Conduction Mode (DCM) or the Boundary Conduction Mode (BCM). So here is the literature review for this question.

Difference between BCM and DCM

The difference between DCM and BCM is shown in the figure above. Now that it is clear that DCM has dead bands in it while BCM operates at the boundary of CCM lets have evaluation of these conduction modes.




Boundary Conduction Mode

• BCM is feasible for high power levels.
• The control of BCM is much complicated because of variable switching frequency.
• We need to sense both the transformer current paths, that means, more component count, less reliability more expensive and more complicated algorithm.
• Output filter design is much complicated because the cutoff frequency need to cater for the online and load conditions.
• The use of BCM however, doubles the inverter power processed. Which means that the energy density is higher and it fits well for PV applications with smallest desired volumes. See reference 2 for filter design.

Discontinous Conduction Mode


References:

1. Kyritsis, A.Ch.; Tatakis, E.C.; Papanikolaou, N.P., "Optimum Design of the Current-Source Flyback Inverter for Decentralized Grid-Connected Photovoltaic Systems," Energy Conversion, IEEE Transactions on , vol.23, no.1, pp.281,293, March 2008
2. Yesl Shin; June-Hee Lee; June-Seok Lee; Kyo-Beum Lee, "CLC filter design of a flyback-inverter for photovoltaic systems," Power Electronics Conference (IPEC-Hiroshima 2014 - ECCE-ASIA), 2014 International , vol., no., pp.493,497, 18-21 May 2014
3. Meneses, D.; Garcia, O.; Alou, P.; Oliver, J.A.; Prieto, R.; Cobos, J.A., "Forward micro-inverter with primary-parallel secondary-series multicore transformer," Applied Power Electronics Conference and Exposition (APEC), 2014 Twenty-Ninth Annual IEEE , vol., no., pp.2965,2971, 16-20 March 2014