A novel hybrid five-level voltage source converter for high-efficiency applications is investigated in this paper. Compared with traditional multilevel converters, this hybrid multilevel converter generates desired staircase voltage levels with a reduced number of power devices and isolated drivers at higher voltage levels. It has redundant switching state combinations in hybrid multilevel converter, which makes it easy to balance flying capacitor voltages and realize fault-tolerant operation. A voltage balancing control strategy based on switching state redundancies is presented for the hybrid multilevel converter, to generate desired levels and also keep voltage balance of flying capacitors at the same time. The performance of the hybrid multilevel converter under various operating conditions is investigated in MATLAB/Simulink. The effectiveness of the proposed hybrid multilevel converter is validated by experiment results.
- Hybrid multilevel converter
- T-type converter
- Redundant switching state
- Phase-disposition PWM
- Voltage balancing control
In this paper, a novel hybrid multilevel converter and its control strategy are presented. The proposed hybrid multilevel topologies can generate more levels with a reduced number of power switches and capacitors compared with traditional FC based multilevel converters. Another advantage of the proposed topology is modularity and symmetry in structure which enables it easy to be extended to more phases and more levels configurations. Since the optimum switching states are selected directly among redundant states, the method can be easily generalized for higher-level converter and also for different combinations of hybrid multilevel converter. A single-phase hybrid five-level converter system with RL-load is investigated in simulation and experiment validation. The high quality output voltage and current are obtained, and the voltages of flying capacitors are balanced by tracking their reference values effectively .Several transient cases are investigated, and good dynamic performances of the proposed hybrid multilevel converter and the control strategy are verified by the simulation and experiment results.
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