Topology Investigation For Multi-level Inversion Using A 3-Terminal Switch-Network

Multi-level topologies are widely applied for power inversion techniques due to lower voltage stress on switches and smaller output filter sizes. Multi-level inverters have recently drawn attention of low voltage applications in industries, such as solar inverters, low power motor drives, and uninterruptible power system(UPS). The basic 3-level inverters, included I-type and T-type 3-level topologies, exhibit significant advantages, such as higher efficiency, samller filter inductor volume, and lower harmonics, compared to the conventional 2-level half-bridge inverter. These inverters have the limitations of industrial applications in terms of more complicated system structure and high number power switches.The idea of a 3-terminal switch network is proposed in the thesis, using interleaving technique and coupled-inductor into the inverter topologies at the first time. Otherwise, with the thinking from the dual-Buck inverter, another idea of a new 3-terminal switch network is proposed again. Both of 3-terminal switch network and new 3-terminal switch network can be used in 2-level and basic 3-level inverter topologies. As a result, the topologies of 3-level half and full-bridge inverter using 3-terminal switch network, 4-level half and full-bridge inverter using 4-terminal switch network, 3-level half and full-bridge inverter using new 3-terminal switch network, and ∏-type, II-type, flying capacitor type, cascaded H-bridge multi-level inverter using new 3-terminal switch network, are analysized, simulated, tes ted, and developed.These new multi-level inverters can use the SPWM modulation strategy. The sine wave output voltage can be achieved with simple and conventional output filter. The topologies and control strategies are effective with the verification of simulation and prototype test. The ripple frequency of output filtering inductor is higher, even double with appropriate phase-shift control. Otherwise, the inverter middle poin t is with multi-level, as a result, the output filtering inductor can be smaller with lower output harmonic current. Finally, the basic 3-level inverter topologies can achieve better performance using new 3-terminal switch network, such lower power losses, lower costs in the output filtering inductor, and higher inverter efficiency. The new multi-level inverter topology family together interleaving technique, coupled-inductor, with inverter topologies, effectively develops research range and application field, and indicates wide research direction of multi-level topologies. These multi-level inverter topologies can be used in the solar inverter. On the other hand, they can also be used in other fields, such as UPS, wind inverter, and variable frequency power system etc.