Analysis and Control of N-level Neutral-point Clamped Dual Active Bridge DC-DC Converter with Capacitor Voltage Balance

Dual active bridge (DAB) dc-dc converter combined with multilevel topology is popular in medium and high voltage areas. This paper proposes an n-level neutral-point clamped (NPC) dual active bridge dc-dc Converter, of which has multilevel diode-clamped bridges. The modulation of the proposed converter is introduced and the power flow equations under different phase shift angles are deduced. Similar to other NPC topology, capacitor voltage unbalance also exists in the proposed converter. In order to realize capacitor voltage balance, the capacitor currents are analyzed using space vector and the relationship between capacitor currents and voltage waveforms of the bridge output is presented. The voltage balancing strategy is designed based on adjusting the length of vectors. The theory and control scheme are confirmed with the simulations.