Robustness of Load Impedance-Based Multilevel Voltage Generation in Neutral-Point-Less H-Type Inverter Topology With Load Imbalance

Multilevel inverters (MLIs) are widely adopted in high power density systems for their efficiency and waveform quality. Conventional capacitor-based MLIs, however, face persistent challenges such as voltage imbalance and device stress induced by neutral currents. To address these limitations, the neutral-point-less H-type (NPL.H) inverter has been introduced, eliminating the static neutral point altogether. Unlike conventional designs, the NPL.H achieves its multilevel outputs through impedance-based voltage division rather than stacked capacitors, thereby offering a fundamentally different mechanism of voltage generation. Since voltage generation relies on the load impedance, the resulting waveforms exhibit inherent sensitivity to load balance. This paper develops an analytical framework for understanding multilevel voltage generation in NPL.H inverters and examines how load imbalance influences voltage symmetry and reliability. Theoretical derivations establish line-to-line voltage levels and neutral point dynamics for each switching state, demonstrating consistent production of half the dc-link voltage via impedance division in the load. An equivalent impedance model is further employed to quantify imbalance effects, introducing a scaling factor that predicts voltage behavior under asymmetric conditions. Simulation and experimental validations confirm the analysis, showing that eliminating the neutral point and accommodating up to 12% load imbalance only cause brief voltage overshoot before stabilizing at expected levels.