Journal of Engineering Science and Technology Review 13 (6) (2020) 130 - 136 Research Article Detailed Mathematical Analysis of Harmonics in Multi-Phase Inverters for Hybrid Electric Vehicles Sangeeta Sahu*, Byamakesh Nayak and Rudra Narayan Dash KIIT, Bhubaneswar, Odisha, 751024, India Received 3 December 2019; Accepted 6 November 2020 ____________________________________________________________________________________________ Abstract This paper presents a comparative analysis of power handling capability, harmonics, losses and cost of three phase, five phase and seven phase inverter which are the main criteria for selection of inverter applied to hybrid electric vehicle. The above performances of the multiphase inverter with different conduction angle are presented to trade off the best suited inverter for hybrid electric vehicle application. The 6 th harmonic pulsating torque created due to 5 th and 7 th harmonic component and 12 th harmonic pulsating torque created due to 11 th and 13 th harmonic which affect the smooth movement of the vehicle at the time of starting and braking condition. This paper gives a clear idea about the comparison of the above harmonic component for different conduction angle scenario of 3phase, 5phase and 7phase inverter. The equations of the performance criteria such output voltage, THD, power handling, losses, etc has been mathematically estimated and verified through Matlab Simulink Power Graphical User Interface. Keywords: Harmonics, Multi-Phase Inverter, Phase Voltage, THD, Hybrid Electric Vehicle ____________________________________________________________________________________________ 1. Introduction An inverter circuit topology uses two switches connected in series as one inverter arm. The number of inverter arms depends on number of phases. That is, a three phase inverter will have three inverter arms whereas a seven phase inverter circuit will have seven inverter arms. All the inverter circuits used in literature for multiphase inverters employ the same topology. In multi phase inverters, the conduction angle can be varied to get optimum output. Depending on the application, the switches used in inverters can be IGBT, MOSFET, GTO, etc. Each of the switches have diodes connected across them and these diodes act as feedback diodes which returns the energy stored in the inductive load to the dc supply. A comparative study on the total harmonic distortion of the output phase voltage at different conduction angle has been presented in this paper. With the decrease in harmonic profile, the ripple in the torque produced in electric vehicles is reduced. For 5th and 7th harmonic, the torque ripple is pulsating with 6 times the fundamental frequency. For 11th and 13th harmonic, the torque ripple is pulsating at 12 times the fundamental frequency. Due to these harmonics, it produces noise, humming sound and jerking at the time of braking. For the same input voltage the power handling capability increases with the increase in the number of phases of the motor. But at the same time, the cost of inverter as well as of the control procedure increases with increase in number of phases. So, there must be a tradeoff between power handling capability, THD and cost of inverter. The 5 th and 7 th phase inverters can be used in hybrid electric vehicles. Multisource inverter can drive traction motors from variable DC voltages without using additional power converters has application in electrified power trains [1]. The transient analysis of high power VSI shows that a VSI is always a stable system with nonlinearities and unstable with respect to control signal [2]. The THD and switching losses are reduced considerably a dual voltage source inverter which is implemented through a modified space vector modulation [3]. A six phase current reconstruction scheme for dual inverters that have application in hybrid electric vehicle is presented in [4]. In this method the simulation and experimental results proof that the cost and volume of dual inverters are reduced as less number of current sensors are used. A bidirectional Z – source inverter has been recommended for the hybrid electric vehicle drive system in which the DC-link voltage is controlled such that the permanent magnet synchronous motor can operate at high speed without weakening the field [5]. The magnetic field created by the inverter in electric vehicles is evaluated using finite element method [6] and few design guidelines have been provided to minimize the same. The fast development of power electronic devices and modern control theory had made the study and applications of five phase permanent magnet synchronous motor as well as its driving system that is the voltage source inverters attract more and more attention. Five phase PMSM has wide applications requiring high DC bus voltage utilization, reliability and power output [7]. THD comparison for a three phase inverter at different conduction mode concludes that 150 deg conduction mode has least THD [8-9]. PWM operation of a five phase voltage source inverter with hysteresis controller can be applied to a variable speed induction motor drive under asymmetrical connections [10]. A comparative study of performance of five phase three level inverter with five phase two level inverter for equal loading shows that five phase three level gives better performance [11]. A five phase inverter fed five phase star connected load operating with five different excitations has been simulated JOURNAL OF Engineering Science and Technology Review www.jestr.org Jestr r ______________ *E-mail address: Sahu.sangeeta@gmail.com ISSN: 1791-2377 © 2020 School of Science, IHU. All rights reserved. doi:10.25103/jestr.136.18