Abstract
A three-phase trinary-asymmetric cascaded H-bridge multilevel inverter topology with single dc source per phase is presented in this paper. Only one of the H-bridges (called Main bridge) is fed from a dc source and all others (called auxiliary bridges) derive their dc links from floating capacitors. Existing literature mostly depend on closed loop control schemes to stabilize the dc link voltage. This paper proposes a new open loop control strategy for balancing of voltage across floating capacitors naturally. DC bus voltages of the auxiliary bridges are converged to maintain a trinary asymmetric ratio with the main-bridge by selecting the right set of space-vectors. Modulation of the inverter is carried out by exploring the space-vector redundancies that will help in achieving natural balancing of capacitor voltages. Selection of number bridges to be cascaded depends on criteria such as the allowable time of convergence, number of switching devices, acceptable power quality indices etc. Considering such constraints, a system with three cascaded cells per phase is found to exhibit satisfactory performances. Hence in this paper, simulation results obtained in MATLAB/ Simulink based model corresponding to such a system are presented. Experimental results observed on a laboratory prototype matched well with the simulation.
Highlights
Multilevel inverters (MLI) have been developed as an emerging technology in recent years [1] and play an important role in energy conversion systems, such as solar, wind, electricdrives, vehicular electrical systems [2] and many other applications
A PV power conditioning system (PCS) based on trinary asymmetric MLI is proposed in [20] where dc links of the Hbridges are fed from coupled inductors
This paper presents a three-phase trinary asymmetric Cascaded H-Bridge (CHB) multilevel inverter with a single dc source per phase
Summary
Multilevel inverters (MLI) have been developed as an emerging technology in recent years [1] and play an important role in energy conversion systems, such as solar, wind, electricdrives, vehicular electrical systems [2] and many other applications. Single dc source topology put forward in [2] requires a greater number of switches and capacitors to generate a nine-level output voltage. A PV power conditioning system (PCS) based on trinary asymmetric MLI is proposed in [20] where dc links of the Hbridges are fed from coupled inductors This makes use of the jumping modulation to avoid regeneration of the auxiliary units. Using the principle of level-doubling [14], a binary asymmetric cascaded multilevel inverter is presented in [23] This topology generates a multilevel voltage waveform with only one bridge fed from dc source and all other bridges have floating capacitors with the ability of balancing in open loop.
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