Research On The Hybrid-clamped Three-level Half Bridge Inverter

Recent years, in response to the growing demand for high voltage, large VA applications such asutility and large motor drive, multilevel power converters have attracted extensive contributorscompared with the conventional2-level converters, because of the advantages: more sinusoidal outputvoltage, lower voltage stress, lower EMI, etc.First of all, this paper introduces the background of the task and the main topologies andmodulation strategies of the multilevel inverters. It compares the working principle and mainproblems between the conventional diode-clamped three-level inverter and the improvedhybrid-clamped three-level inverter, and analyzes the advantages of the hybrid-clamped three-levelinverter. This paper uses the hybrid-clamped three-level topology and SPWM modulation strategy toimprove the voltage stress and to keep the capacitors’voltage balanced.Secondly, the paper constructs the system modeling of the hybrid-clamped three-level inverterwhich has two closed loops and designs the compensative network of the voltage control loop andcurrent control loop. The inner current loop helps to increase the response speed, while the outervoltage loop assures the output voltage sinusoidal and stable. In addition, the outer voltage loopbrings in a resonant controller to increase the stability of voltage precision. The simulation resultsverified the feasibility of control strategy and the high output voltage quality of the system.At last, this paper designs a experimental platform of digital controlled hybrid-clampedthree-level inverter which core control device is TMS320F2812. The simulation and experimentalresults verified the topology, modulation strategy and control strategy are all correct and feasible.Theresults also verified this scheme can improve the voltage stress and keep the capacitors’voltagebalanced.