Design, Simulation and Comparison of Three-phase Symmetrical Hybrid Sinusoidal PWM fed Inverter with Different PWM Techniques Mohiuddin Mahbub Department of Electrical & Electronic Engineering Brac University Dhaka, Bangladesh mahbubrafi011@gmail.com Mohammad Ali Hossain Department of Electrical & Electronic Engineering Brac University Dhaka, Bangladesh ali.hossain.009@gmail.com Abstract—PWM technique can reduce switching and harmonic losses of the inverter. Hybrid PWM inverter utilizes half of the switches to operate at low-frequency signal and the other half of the switches to operate at high-frequency signal to reduce switching loss. But switching loss and heat dissipation among switches are uneven which reduces system reliability. Three-phase symmetrical hybrid sinusoidal PWM inverter is proposed where all switches operate at low and high-frequency signals alternatively which removes unequal switching loss and heat dissipation between switches. Switching loss, heat dissipation and total harmonic distortion of SHSPWM inverter don’t vary from HPWM. The SHSPWM inverter is simulated without and with a pie filter in MATLAB/Simulink software to understand performance differences. SHSPWM performance is compared with Sinusoidal PWM, Sixty-Degree PWM and Trapezoidal PWM. The analysis was done by varying modulation index and carrier frequency to see inverter output variation. Keywords—Three phase inverter, THD, Symmetrical Hybrid Sinusoidal PWM, SPWM, TPWM, SDPWM I. INTRODUCTION Inverters are used widely in household and industrial applications. There are semiconductor switches used in the inverter to convert dc signal to ac signal by turning the switches on and off via pulse width modulation (PWM) techniques. When DC is converted to AC, it contains some harmonic content, which affects the performance. The performance parameter of an inverter is total harmonic distortion (THD), distortion factor, lowest-order harmonic (LOH), etc. The THD measurement process shows the closeness between a waveform and its fundamental component. Efficiency, power factor, etc. of a system can be understood from THD [1-2]. Lower THD value of an inverter output means better efficiency, high power factor, etc. Therefore, THD plays an important role in power electronic systems. One of the most important types of power loss in switching devices are switching loss. Switching loss is proportional to the switching frequency. For low switching frequency, switching loss is negligible, but for the high switching frequency, switching loss increases significantly [3-4]. Even though the PWM techniques create better output wave quality but their switching loss is also higher. In the Hybrid PWM method [5], half of the switches are driven at high switching frequency PWM signals for high-quality output, and the other half are operated at low switching frequency PWM signals to reduce switching losses. Even though switching losses are nearly halved, the HPWM technique reduces system reliability due to uneven heat dissipation. Symmetrical hybrid sine PWM for a full bridge inverter has been implemented in recent years [6-7]. In this paper, a three-phase symmetrical hybrid sinusoidal PWM (SHSPWM) technique fed inverter is proposed to reduce switching losses with equally balanced switch heat dissipation, good harmonic performance similar to HPWM, and better system reliability than HPWM. This SHSPWM technique fed inverter is simulated using MATLAB/Simulink software. To create a sinusoidal output and reduce harmonic distortion, a pie filter [8] is added in simulation. SHSPWM method performance is analyzed by varying modulation index and carrier frequency to see the variation in the inverter output characteristics like voltage THD%, current THD%, etc. Also, SHSPWM technique fed inverter performance is compared with three popular PWM techniques like Sinusoidal PWM (SPWM), Sixty-Degree PWM (SDPWM) and Trapezoidal PWM (TPWM). All mentioned PWM techniques data taken for both without and with a pie filter added to inverter condition using software simulation and presented in a tabular format. Fig. 1 shows a general model of a three-phase inverter. Fig. 1. Three-phase inverter model [9]. II. PWM TECHNIQUES A. Symmetrical Hybrid Sinusoidal PWM (SHSPWM) Technique: PWM techniques use a higher frequency to operate all switches than output frequency, which creates higher switching harmonics. These harmonics are easier to filter and the filter cost is also low. However, the HPWM technique is widely used to reduce switching loss. The disadvantage of the HPWM is that the switching loss of all switches are not equal because they run at different switching frequencies. Due to high and low switching frequencies, heat dissipation in the switches is not the same as well which reduces the reliability of the system. The SHSPWM technique is the new innovative alternative of the HPWM technique, which utilizes different switching frequencies effectively [6-7]. The SHSPWM technique uses low and high-frequency switching signals alternatively to turn on-off inverter switch and applies this frequency combination to all the switches of the inverter. Due to this frequency combination, switching loss, heat dissipation, and THD of SHSPWM inverter are the same as 2nd International Conference on Robotics,Electrical and Signal Processing Techniques (ICREST'21) 978-0-7381-3042-2/21/$31.00 ©2021 IEEE Page 1