Multi-state and Interleaved Converters With Passive Impedances for Current Sharing

Abstract

This paper presents multilevel switching cells that allow the generation of high-power nonisolated dc-dc, ac-dc, dc-ac, and ac-ac converters. The cells are classified in two groups: multi-state switching cells based on autotransformer and interleaved switching cells based on inductors. Each switching cell has an impedance based on a small inductor connected between the legs, which is named current sharing circuit and guarantees zero average voltage across the involved magnetic components, therefore compensating eventual differences between the pulse width modulation duty cycles. The inductor should be small because it causes the duty cycle reduction. In order to verify the current sharing between the magnetic components, two dc-dc buck converters operating at 25 kHz and rated at 1 kW, where the input voltage is 200 V and the output voltage is 60 V, are implemented and evaluated in laboratory.

Survey on topologies based on the three‐state and multi‐state switching cells

“…In this case, slight differences regarding the inductors, switches, and diodes will not cause significant current unbalance as demonstrated in [35]. This issue is not expected in interleaved converters, which are prone to current unbalance and additional thermal stress on a given phase [36]. The very same aspects are valid for the converters operating in OM in Fig.…”

“…Besides, small differences in the duty cycle of the active switches may cause such undesirable effect, eventually leading magnetic components to saturation. This concern has justified the introduction of passive impedances between the legs of the MSSC based on small inductors to ensure zero average voltage across the windings of the magnetic components as in [36]. Active techniques can also be used for this purpose [73], but at the cost of higher complexity associated to a dedicated control circuit.…”