Abstract
In this paper, a novel four-level single-phase multilevel converter is introduced, consisting of six active switches arranged in a quasi-nested configuration. The proposed topology synthesizes its output voltage levels with respect to a floating neutral point, using four cascaded capacitors with identical voltage levels. The proposed converter contains a reduced number of components compared to the neutral point clamped (NPC) or active-NPC topologies (ANPC) for the same number of output voltage levels, since it does not require diode or active switch clamping to a neutral point. Moreover, no floating capacitors with asymmetric voltage levels are employed, thereby simplifying the capacitor voltage balancing. The switching operation principles, modulation technique and control scheme for supplying a single-phase resistive-inductive load are addressed in detail. The proposed four-level inverter allows generating an additional output voltage level with the same semiconductor count as conventional three-level inverters such as NPC and ANPC which allows a superior waveform quality, with a THDv reduction of 32.69% in comparison the clamped inverters. Experimental tests carried out in a laboratory-scale setup verify the feasibility of the proposed topology.
Highlights
Nowadays, multilevel inverters (MLI) have become the main solution for applications where high power quality and dynamic performance are required, in mediumand high-power systems [1,2]
neutral-point clamped (NPC) and active-NPC topologies (ANPC) topologies with four levels or more, so as the flying capacitor (FC) topology, are not suitable for single-phase applications, in this paper we propose a novel single-phase MLI topology derived from the four-level double-star converter called four-level quasi-nested (4L-QN)
From the results presented in the Table, the proposed inverter offers conduction losses 6.25% lower than ANPC, 24.08% lower than NPC and 31.15% lower than H-bridge topologies
Summary
Multilevel inverters (MLI) have become the main solution for applications where high power quality and dynamic performance are required, in mediumand high-power systems [1,2]. Conventional MLI topologies are primarily the cascaded H-Bridge (CHB), the neutral-point clamped (NPC) and the flying capacitor (FC) configurations [5,6,7,8]. Even though conventional MLI topologies are considered as today’s standard because of their technological maturity, they are subject to intrinsic limitations that have motivated the design of alternative MLI configurations [9,10]. In the case of NPC, there is an important increase in its component count for configurations with higher number of levels. The 3-level NPC basic cell shown in Figure 1a has 4 active switches and 2 clamping diodes, whereas a 4-level configuration requires 6 of each devices and for 5-levels the component count reaches 8 active switches and 12 diodes. An additional drawback of the NPC topology is the requirement of complex capacitor voltage-balancing schemes [11]
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