Cascaded stage Single phase load Level Generator Polarity Generator a Single phase load Single phase topology Phase arm-a Phase arm-b Phase arm-c Y- connected Three phase load R S T PG stage A B C J g Y-connected Three phase load d e b c Da2 Da1 Sa1 Sa2 Sa3 Sa4 Sb3 Sb4 Sc3 Sc4 load load load J Bi-directional switches Conventional 3-phase 2- level inverter g N A B C Vc BD-switch-B BD-switch-C PGS cell-C Fig. 1. Block diagrams: (a) the level generator and polarity generator based CMLI topology, (b) the CMLI topology which don’t need polarity generator, (c) the 3-phase CMLI topologies, (d) the proposed new three phase CMLI, (e) Circuital model of the PG-stage A novel generalized concept for three phase cascaded multilevel inverter topologies Md Mubashwar Hasan, A. Abu-Siada, Syed M. Islam, and S. M. Muyeen Department of Electrical and Computer Engineering, Curtin University, Perth, Australia m.hasan12@postgrad.curtin.edu.au, a.abusiada@curtin.edu.au, S.Islam@curtin.edu.au, Sm.Muyeen@curtin.edu.au Abstract— Many new cascaded multilevel inverter (MLI) topologies have recently been proposed and published in the literature. All proposed topologies demand significant amount of semiconductor components and input dc supplies, which is considered the main drawback for the implementation of three phase cascaded MLIs. This paper proposes a new generalized concept that could be employed within any existing cascaded MLI topology in order to reduce its size in terms of device count including semiconductor switches, diodes, and dc power supplies. The new generalized concept involves two stages namely; cascaded stage (CS) and phase generator stage (PGS). The PGS stage is a combination of conventional three phase two level inverter (CTPTLI) and three bidirectional (BD) switches, while the cascaded stage can be modified using any existing cascaded topology. The proposed concept is validated through extensive simulation and experimental analyses. Results show the capability of the proposed technique in reducing device count of the existing topologies while maintaining its performance. Keywords—Power electronic device counts, new cascaded topology, THD. I. INTRODUCTION Owing to the several advantages of cascaded multi-level inverters (CMLIs) including its ability to generate high voltage by utilizing low voltage power electronic devices [1-3], low voltage stress (dv⁄dt) on the switches [4, 5], and low harmonic distortion in the output waveforms, applications of CMLIs in power systems have received much attention and several CMLI topologies have been recently proposed and published in the literature [5-13]. Based on the operating principle and the structure, CMLI topologies can be classified into three groups: (1) topologies with level generator and polarity generator [5, 7, 13, 14]; (2) modified CMLI topologies [6, 8, 9, 12, 15-18] and (3) three phase CMLI topologies [1, 3, 10, 19-22]. There are many cascaded MLI topologies, which contain two parts; level generator and polarity generator as shown in Fig. 1a [23-27]. The level generator is a cascaded connection of series cells, which is responsible to generate multilevel unipolar voltage while the polarity generator converts this unipolar voltage into bipolar voltages [5, 27, 28]. While level generator structure is unique for different topologies, the structure of polarity generator has been always an H-bridge connection involving four semiconductor switches. The number of cascaded cells in the level generator may be increased to enhance the number of voltage levels in the output without any change in the polarity generator [5, 27]. The level generator switches may work with high frequency, but the polarity generator switches always work with line voltage frequency [27]. Many new CMLI topologies are proposed, which are able to generate bipolar voltage without using polarity generator and they can be classified under the modified CMLI category as shown in Fig. 1b [29-33]. Some other creative CMLI topologies such as cross-switched topologies and modified H- bridge topologies also undergoes in this classification [12, 15, 16, 34-36]. Some CMLI topologies are mainly developed for three phase applications, they can’t be directly used for single phase applications [4, 37-43]. These topologies are considered within the category of three phase CMLI topologies as depicted in Fig. 1c, they have three identical phase arms. A few hybrid three phase topologies can also be included under this category such as topologies published in [19, 37, 41]. This is the author's version of the paper published in this conference. Changes may appear in the published version. DOI: 10.1109/GreenTech.2017.22