Comparative Evaluation of Three-phase Voltage and Current Source Inverter in Renewable Energy System

S A Azmi,J H Leong,S Y Chong

doi:10.13189/ujeee.2019.061507

Abstract

In the renewable energy power generation system, voltage source inverters (VSIs) are commonly used due to its stable operation, high efficiency and low cost. However, a dc-dc boost converter is necessary for VSI to operate has increased the system complexity. Thus, current source inverters (CSIs) has become an alternative of VSI due to its ability of voltage boosting and can provide a better output waveform. This paper presents a comparative evaluation of VSI and CSI focusing on topological circuits and basic operational parameters of these inverters. The performances of VSI and CSI are analyzed in MATLAB/Simulink focusing on two operational characteristics which are modulation index, ma and switching frequency, fsw. The performance of VSI and CSI are dependent on the modulation index, increasing ma increase the inverter efficiency. In term of switching frequency, it does not affect much on the efficiency of inverters, yet a normalized switching frequency of odd multiple of three provides better fundamental output and harmonic minimization. Furthermore, CSI presents its voltage boosting capability which can boost 6-27% within ma of 0.05-1.0 and using the same modulation technique, VSI and CSI have present duality relationship in term of output voltage and current wave shapes.

Highlights

In recent year, renewable energy source is rising due to increasing concern on environment pollutions and potential scarcity of fossil fuels
Inverter can be classified as voltage source inverter (VSI) and current source inverter (CSI) based on their input source
This paper presents a comparative evaluation of VSI and CSI based on the operational characteristics of modulation index, ma and switching frequency, fsw

Summary

Introduction

Renewable energy source is rising due to increasing concern on environment pollutions and potential scarcity of fossil fuels. VSI always required a dc-dc boost converter for boosting and regulating its input voltage [3,4] This increase the circuit complexity and power losses for overall system. In [5], a VSI and a CSI with an intermediate step-down converter are implemented to a low-power induction motor which its power is below 1kW Both inverters are compared in term of motor efficiency, insulation stress and common voltage. The comparative analyses from low to high switching frequency applications establish in [2], which state VSI has lower total semiconductor power losses at low switching frequency while CSI has lower total semiconductor power losses at high switching frequency From these previous researches, they indicate that the selection of inverter topology should be always based on the industrial requirement. The open-loop performance of both inverters is investigated in term of fundamental output and THD in MATLAB/Simulink

System Configuration

Test I

Test II

Duality of VSI and CSI

Conclusion