Carrier-based PWM Techniques for Current-fed Quasi-Z-Source Converters

The conventional Current Source Converters (CSCs) are preferred in different applications than the Voltage Source Converters (VSCs) due to their simple construction and sinusoidal input/output voltage and current waveforms. However, the current source converters are unidirectional converters. Moreover, it can operate only in the voltage boosting or current bucking mode of operation. Therefore, current-fed impedance source converters (CF-ZSC) are proposed to overcome the shortcoming of the conventional CSCs. This paper proposes a new and simple Carrier-Based PWM (CBPWM) technique to modulate the CF-ZSCs. This technique modifies the CBPWM of the CSC to modulate the CF-ZSC switches to obtain buck/boost operations in addition to the bidirectional power flow. The theoretical analysis and operating principles of the proposed technique are explained and modeled. Unlike the traditional VSCs and CSCs, CF-ZSC has an additional open-circuit state by turning off all switches. Therefore, in this paper, additional zero states can achieve by one of following control methods, simple and maximum approach. Besides the implementation simplicity, the proposed methods have a lot of advantages such as reduction of switching frequency, no penalty in the output line current harmonic distortion. A comparison between the proposed methods has been introduced. The performance of the proposed technique is verified using MATLAB/Simulink. The simulation results show that the effectiveness of using these methods in controlling CF-ZSC.