Carrier-Based PWM of Voltage Fed Five-Phase qZSI with Coupled Inductors Shaikh Moinoddin, Member, IEEE, Haitham Abu-Rub, Senior Member, IEEE, Atif Iqbal, Senior Member, IEEE. Abstract: Multiphase machines are considered for high power variable speed drive applications due to numerous advantages that they offer when compared to their three-phase counterparts. Multiphase VSI or CSI used to provide variable voltage and variable frequency supply with appropriate PWM control to multiphase machines. Carrier-based PWM and space vector PWM (SVPWM) are the most common options for controlling a multiphase converter. A new class of inverter called quasi impedance source (qZSI) employed mostly for solar PV applications, is presented in this paper for five-phase output. Although the application of multiphase inverters are mostly in motor drives, however, the proposed topology can be employed in conjunction with multiphase wind generator system as well. Another application of the proposed topology can be conceived in solar PV based multiphase water pumping solution. The major advantage of the proposed topology is the voltage boost and continuous source side current. This paper is aimed at providing boosted outputs of carrier-based PWM implementation of five- phase qZSI with coupled inductors with and without shoot- through states. The concept is verified by simulation using Matlab Simulink model. Keywords: Voltage Source Inverter; quasi-Z-Source Inverter; Coupled-inductors; Solar PV; Five-phase. I. INTRODUCTION Unlike traditional voltage/current source inverters, an impedance source inverter (ZSI) can be used for bucking and boosting the D.C. link voltage [1]. But the ZSI has the drawback of discontinuous input current which necessitates using a filter [2, 3] to maintain continuous current at the source side. However, in this kind of converters it is important to reduce the modulation index for boosting the low voltage received from the source such as PV cells, fuel cells etc. [4]. Trans-ZSI [5] and T-source inverter [6] tried to improve the relationship between voltage-gain (G) and modulation index (M) keeping the used high frequency transformer turn ratio greater than unity. The quasi impedance source inverter (qZSI) which is derived from traditional ZSI, has the advantages of lowering component ratings and drawing continuous dc current from the DC source [2]. Performance of qZSI was improved by using two-stage q-z-source [3]. In single-stage, boosting can be achieved by using coupled inductors [4]. The maximum boost control of ZSI is achieved by turning all zero states into shoot through states [7]. Modified version of conventional PWM strategies had been used for PWM of ZSI [8, 9, 10, and 11]. In impedance source inverters and their variants, sinusoidal carrier-based PWM scheme and space vector PWM schemes are employed, with the exception that the upper and lower switches of the same leg can be turned on simultaneously, in order to obtain boost operation. Relationship between space vector PWM and carrier based PWM for 3-phase [12] and 5-phase VSI [13, 14] were established. Improved torque-per-ampere characteristic, better fault tolerance, and reduction in per phase power, and consequently, lower rating of the semiconductors in the power electronic converter are some of the main reasons why multiphase machines are considered for applications such as marine electric propulsion, electric vehicles (EVs) and hybrid electric vehicles (HEVs), “more electric aircraft,” locomotive traction, and high-power applications in general [13]. In this paper a quasi-Z source, comprising of coupled inductors (all three inductors), is used to realize five-phase inverter with modified carrier based PWM scheme. The modification is that, in boosting mode, the shoot-through state is applied in one leg at a time to reduce the switching losses. The same circuit can be used to boost the voltage without shoot-through. The circuit is simulated using Matlab-Simulink software. II. POWER CIRCUIT TOPOLOGY The power circuit topology of the proposed inverter is shown in Fig. 1. The switching combination produces 32 switching states. The active states (total=30) are given in Table I. Table II contains the possible zero states (total=2) and shoot through states (total=31) and Table III shows possible two open zero states. If ‘n’ is number of phases then total states=(2 (n+1) -1), which includes active, zero, and shoot through states excluding the open-zero states. The active states are shown graphically in Figs. 2-4. Fig. 1. Power Circuit Table-I Switch-states in active modes Modes S1S3S5S7S9 S6S8S10S2S4 Modes S1S3S5S7S9 S6S8S10S2S4 Modes S1S3S5S7S9 S6S8S10S2S4 1 11001 00110 11 10000 01111 21 01001 10110 2 11000 00111 12 11101 00010 22 11010 00101 3 11100 00011 13 01000 10111 23 10100 01011 S9 S10 Ve S7 S8 Vd S5 S6 Vc S3 S4 Vb S1 S2 Va Battery L1 L2 L3 C1 D1 C2 VDC C3 Rc3 D2 D3 PV or Fuel Cells Coupled Inductors Vi IL1 IL2 IL3 ILink Iin 2013 IEEE GCC Conference and exhibition, November 17-20, Doha, Qatar 978-1-4799-0724-3/13/$31.00 ©2013 IEEE 390