I. Introduction
As global installed PV capacity continues to grow at an exponential rate [1], power electronic concepts and converters used in PV plants are evolving. In distributed maximum power point (DMPPT) applications, a maximum power point tracking (MPPT) converter is embedded with every PV module [2], [3]. While increasing the energy yield, by mitigating the negative effects of partial shading and module mismatching [4], such architecture provides opportunities for enhanced data gathering, diagnostic and safety. At the start of 2017, in [5], it was estimated that more than 70% of U.S. residential installations would use module integrated converters by the end of that same year. On one hand, dc-ac module integrated converters (ac-MICs or microinverters) can be used to interface each PV module directly to the ac grid, however due to the large voltage step-up ratio required, they demand high-voltage rated components, together with double stage conversion or galvanic isolation, challenging low costs and high efficiencies [6]. On the other hand, dc-dc module integrated converters (dc-MICs or power optimizers), require a much lower voltage conversion ratio, since a PV inverter is still used for interfacing to the ac grid. dc-MICs are implemented with low voltage rated components and they do not need galvanic isolation, hence representing an economically attractive and highly efficient solution [7]. It is estimated that power optimizers increase the PV system annual performance up to 6%, recovering on average 36% of the power lost from partial shading [8]. A system deploying dc-MICs is shown in Fig. 1. In this configuration, the dc-MICs are preferred to have both buck and boost capability [6]. The non-inverting buck-boost is a well suitable dc-MIC topology [4], [9], due to its versatility, basic structure [10], [11] and high efficiency [4].