Multi-level converter

A multi-level converter (MLC) or (multi-level inverter) is a method of generating high-voltage wave-forms from lower-voltage components. MLC origins go back over a hundred years, when in the 1880s, the advantages of DC long-distance transmission became evident.^[1]

Modular multi-level converters (MMC) were investigated by Tricoli et al in 2017. Although their viability for electric vehicles (EV) was established, suitable low-cost semiconductors to make this topology competitive are not currently available (as of 2019).^[2]

In 1999, Tolbert described the use of MLC for battery operated electric motors.^[3]

Habib's 2018 review paper^[4] reviews multi-level inverters (a synonym for MLC) stating the advantages of bi-directional energy flows to power the motor or charge the battery system.

High-voltage DC converters

HVDC converters typically use series connected switched capacitors blocks. The blocks are switched in or out of the circuit to form the desired waveform, typically three-phase AC.

Low-voltage DC converters

Hydrogen generation via electrolysis requires DC currents over several thousand amperes, but DC voltages in the range of only 100...400 VDC. A high voltage modular multi-level converter (MMC) can be adapted by connecting a galvanically isolated LLC resonant converter to each module capacitor.^[5] Several half-bridge and full-bridge based MMC topologies are evaluated in.^[6] Such a converter can also be used to provide a centralized 400V DC power supply for data centers.

M2LeC

M²LeC (pronounced Emlek), is a form of multi-level converter that combines the functions of generating electric motor wave-forms, with battery charging and management in a single set of power electronics hardware, where the various functions are performed through software alone.