A PV Power Conditioning System Using Nonregenerative Single-Sourced Trinary Asymmetric Multilevel Inverter With Hybrid Control Scheme and Reduced Leakage Current

Frequency-PWM hybrid controller of single-switch forward-flyback converter for DC-link regulation of 27-level cascaded H-bridge inverter

“…Then the multi-output converter has two voltage gains. The gain of the CCM forward converter is (1), that of the DCM flyback converter is (2).…”

“…Recently, Multi-Level Inverters (MLI) have been studied because they have many advantages such as reducing Total Harmonic Distortions (THDs), output filters size, and switch stresses, so on [1,2,3]. From the advantages, they have been gradually extended even to small-scale rooftop inverters and building integrated photovoltaic (PV) systems [4].…”

“…Among the topologies, Cascaded H-Bridge (CHB) inverters, called multi-cell inverters, are supposed to be the most promising candidate, because they require the minimum number of switches, diodes, and capacitors compared to others, in order to achieve the same number of levels [3]. The CHB structures are generally categorized into two types: symmetric and asymmetric types [1]. Actually, asymmetric CHB inverters can make more levels than symmetric ones, which contributes to the reduction of the THDs, common-mode voltages, output filter size, and the switching losses [5].…”

“…Actually, asymmetric CHB inverters can make more levels than symmetric ones, which contributes to the reduction of the THDs, common-mode voltages, output filter size, and the switching losses [5]. Additionally, asymmetric CHB inverter achieves higher efficiency because most of the inverter power is processed through the 50/60-Hz main H-bridge cell [1,5]. Despite these advantages, however, this topology has a drawback of need of pre-stage isolated, floating, and well balanced.…”

“…However, the HFL topology needs additional switches, diode-bridges, and an extra reset circuit for the ferrite transformer. Another one is using a boost DC-DC module based on a coupled inductor and charge-pump circuit for 27-level inverter [1]. Although this topology can make floating and isolated voltages for feeding each auxiliary H-bridge cell, these voltages produced by coupled inductor of the boost converter is not precisely controlled because the secondary sides are passive-circuited.…”