Design and Simulation Analysis of a Novel Bidirectional 7-Level Multilevel Inverter Topology for Energy Storage Systems

Abstract

Conventional multilevel inverter (MLI) topologies, such as Neutral Point Clamped (NPC) and Cascaded H-Bridge (CHB), are widely utilized to improve power quality; however, they often require a high number of isolated DC sources and suffer from high switching losses and increased circuit complex- ity. To address these limitations, this paper presents a novel 7- level bidirectional MLI topology specifically designed for applica- tions requiring bidirectional power flow, such as energy storage systems (ESS) and mobile power storage units. The proposed topology utilizes a single DC source integrated with a capacitive voltage divider to generate the required intermediate levels. To minimize switching losses and computational complexity, a Modified Nearest Level Control (NLC) strategy is employed. The switching angles are analytically pre-calculated to synthesize a 7-level staircase waveform with minimized low-order harmonics, ensuring a fundamental output voltage that meets design speci- fications while inherently maintaining capacitor voltage balance through optimized state selection. This approach eliminates the need for high-frequency carriers, real-time reference tracking, or complex external balancing circuits. Performance of the topology was evaluated through extensive simulations at a 5 kW full-load operating point. The results demonstrate a remarkable efficiency of 98.8% in inverter and 98.5% in rectifier operating modes. By generating a 7-level staircase waveform at the output, the proposed configuration provides an effective power conversion interface while minimizing thermal management constraints. These findings indicate that the proposed topology offers a high-power-density and cost-effective solution for modern power electronic interfaces in bidirectional energy management systems.