Voltage boosting capability of three phase current source inverter for standalone system

Abstract

This paper presents a three-phase current source inverter (CSI) topology with voltage boosting capability for standalone system. Current source inverter (CSI) and voltage source inverter (VSI) are two competitive options to be used as an interfacing unit between variable dc input resource and ac output fed into on-grid, off-grid and industrial used. Among the two topologies, VSI is widely used due to its variable controllable output voltage and ability to operate steadily with open loop V/Hz control. Yet, it suffers circuit complexity due to the need of extra converter stage to meet the required output. On the other hand, CSI has an advantage of voltage boosting capability and better quality of output waveshape, thus no extra converter stage is needed. Most of research works were focusing on studying the suitability and practicality of CSI, along with the advancement using silicon carbide-based power switches and improved modulation techniques to minimize the harmonics suffer by CSI. There is lack of research in investigating the boosting capability particularly on how high CSI able to boost the fundamental output and its impact to overall performance in both open and closedloop standalone system. Thus, this work is intended to highlight in detail the boosting capability of CSI and compare with VSI based on the several circuity and operational features. To support the work, three modulators are implemented namely sinusoidal pulse width modulation (SPWM), third harmonic injection PWM (THIPWM) and space vector modulation (SVM). A dedicated synchronous frame proportional-integral (PI) control in used in closed-loop condition. Result shows that CSI topology able to boost the fundamental output voltage by 52% to 58% by using smaller modulation index as compared to VSI. Interestingly, CSI able to achieve comparable quality and harmonic minimization of output voltage and current as in VSI but with smaller PI control gain. All works are analyzed and verified using MATLAB/Simulink platform.