## 1 Introduction  
Photovoltaic (PV) systems have been established as one of the most important renewable energy sources around the world in recent years, reaching a cumulative installed capacity of 760.4 \(GW\), of which 139.4 \(GW\) were installed in 2020 [1]. Therefore, there is continuous research interest in improving power harvesting and mitigating the significant power reductions produced by non-homogeneous conditions over the PV arrays. When a PV array is operating under homogeneous conditions, i.e., all the modules operate at the same irradiance and temperature, there is only one maximum power point (MPP) in its power vs. voltage (P-V) curve [2]. However, real PV arrays operate under non-homogeneous conditions due to partial shading, soiling, not uniform aging, differences in the characteristics of the modules, etc. These non-homogeneous conditions generate multiple MPPs in the array P-V curve, where the global MPP (GMPP) is considerably smaller than the sum of the maximum power that can be produced by each module [2]. There are two main architectures to mitigate the power losses produced by non-homogeneous conditions. The first one uses a string or array inverter with an MPP tracking (MPPT) algorithm that is able to track the GMPP even if the array is operating under time-varying non-homogeneous conditions. However, those systems cannot extract all the power available in the PV modules since non-homogeneous conditions activate one or more bypass diodes in the PV modules, which avoids the power harvesting from the bypassed sub-modules [3]. The second architecture to mitigate the power losses produced by non-homogeneous conditions uses one inverter, called a microinverter, for each module, which allows the direct connection of a PV module to the grid. These devices allow the extraction of the maximum power from each module and reduce the number of active bypass diodes; as a consequence, there is an increment in the power production from an array operating in non-homogeneous conditions [4]. Moreover, microinverters provide a flexible design, commissioning, and maintenance of the PV system since each set module-microinverter can be independently connected and disconnected from the grid without de-energizing the whole string or array. Additionally, microinverters improve the system reliability because the failure of one set module-microinverter does not affect the rest of the system. Additionally, microinverters also increase safety because they avoid the presence of high dc voltages [5]. A microinverter is typically formed by two power stages connected through a dc-link capacitor [4]. The first stage is formed by a dc/dc converter with high voltage gain to generate the dc bus voltage required by the inverter (e.g., 200 V [6], 240 V [7], 311 V [8], 380 V [9], and 400 V [10]) from the voltage of a single PV module, whose voltage can be around 18 V [11] or 30 V [12]. This dc/dc converter is also used to implement the MPPT algorithm, which usually generates a voltage or current reference to find and track the MPP of the module. Such reference is tracked by a control system to improve the MPPT dynamic response and reject the 100 Hz or 120 Hz voltage oscillations reflected in the PV module from the grid [13]. Moreover, the second stage of a microinverter is a dc/ac converter that synchronizes with the grid and injects an ac current proportional to the power produced by the PV module. This stage includes a phase-locked loop (PLL) to generate a sinusoidal signal synchronized with the grid, which is used with a control system that regulates the dc bus voltage by modifying the amplitude of the ac current injected into the grid [4]. The dc/dc converter of the microinverters can be implemented with isolated or non-isolated topologies; nevertheless, isolated topologies are preferred since they provide galvanic isolation, high voltage gains, and a reduced number of components [4].