BALANCING VOLTAGE IN MODULAR MULTILEVEL CONVERTER WITH NEAREST LEVEL CONTROL TECHNIQUE AND ASYMMETRIC MULTI-LEVEL INVERTER TOPOLOGY

Abstract

This paper proposes an asymmetric source configuration of multilevel inverter (MLI) topology with
Nearest Level Control (NLC) technique for efficient and cost-effective power conversion. The proposed
topology consists of eight unidirectional switches, two bidirectional switches, and four isolated DC sources,
producing 25-level and 21-level outputs with 1:5 and 1:4 source configurations, respectively. By using NLC
technique for switching control, the topology produces both positive and negative voltage levels without the
need for a separate backend H-bridge. Moreover, only four switches are in an ON mode in every state, resulting
in less per unit Total Standing Voltage and reduced semiconductor device costs.
High-switching frequency Pulse Width Modulation (PWM) techniques often lead to switching losses in highlevel inverters. Therefore, this paper proposes the use of NLC technique to reduce switching losses, making it
particularly suitable for high-level inverters. The proposed topology has potential applications in renewable
energy integration to the grid and drives application. Simulation results obtained using MATLAB/Simulink
validate the proposed topology and demonstrate that the inrush current at the input of DC sources has been
eliminated.