Sharif Digital Repository

In Z-source family inverters, shoot-through (ST) states are applied as a part of passive state in each switching cycle. The distribution of ST intervals along a switching period affects the system parameters as total harmonic distortion (THD), switching loss and common-mode voltage (CMV). In this paper, ST methods in a three-phase quasi-Z-source inverter (q-ZSI) are compared due to the CMV level. High-frequency harmonics of CMV cause leakage current flow in a transformerless grid-connected photovoltaic (PV) system. Through the comparison of the ST methods, the method with minimum CMV is identified. The experimental results are Prasented for a low voltage q-ZSI prototype. © 2018 IEEE  

A PWM controlled class-D amplifier generates harmonics at switching frequency and its multiples. In this paper, the Random PWM (RPWM) technique is applied in order to spread the noise spectrum over a wide range, thus, considerably reducing amplitudes of these harmonics and the consequent EMI problems. A Line Impedance Stabilization Network (LISN) is used to study the RF noise emanating from the converter. Simulation and experimental results confirm the validity method and demonstrate the effectiveness of applying the RPWM technique in reducing the RF noise level  

Random pulse width modulation (RPWM) technique has been employed to generate the control signals of Vienna-type rectifier. This technique is compared to two conventional techniques (Hysteresis-band and ramp comparison with fix frequency carrier signal). Simulation results are illustrated for three approaches. The results verify significantly reduction of high frequency harmonics magnitude; and consequently overcome electromagnetic interference (EMI) problem in this active type of rectifier. ©2009 IEEE  

Leakage current is originated from common-mode voltage (CMV) time variations in a grid-connected photovoltaic (PV) system and results in several deficiencies. In this paper, a new method is proposed for CMV reduction in a three-phase voltage source inverter (VSI) system. The proposed method is based on space vector modulation and it utilizes only odd and zero vectors. By using the proposed method, the number of fluctuations of the CMV waveform per switching cycle is reduced; therefore, the amount of high-frequency harmonics of CMV is decreased. In addition, because of applying both active and zero vectors by the proposed method, the total harmonic distortion becomes less than most of other... 

Z-source family has been widespread in photovoltaic (PV) applications. In trasformerless grid-connected PV systems, the common mode voltage (CMV) time variations, cause the leakage current flow. This current flows through the stray capacitance of the PV panels. For a Z-Source Inverter (ZSI), the CMV would have higher high-frequency harmonics, due to the shoot through states within the switching cycles. In this paper, the CMV of a ZSI is analyzed and a simple method is proposed for the harmonic reduction of the CMV in the ZSI. The CMV reduction method is based on changing the switching states. The CMV in reduced method is compared to the CMV in the traditional ZSI in frequency domain by using... 

The leakage current originated from the fluctuations of the common-mode voltage (CMV) is an issue in a transformerless grid-connected photovoltaic (PV) system. In this paper, a modified space vector modulation based on the Fourier transform analysis is proposed to reduce the leakage current in a three-phase quasi-Z-source inverter (qZSI). The CMV harmonic content in a qZSI contains low and high-frequency harmonics which cause safety and EMI problems respectively. By implementing the proposed modulation in a three-phase qZSI, the low-frequency harmonics of the CMV are mainly reduced. The distribution of the high-frequency harmonics is also modified in a way they can be simply filtered.... 

The leakage current originated from the fluctuations of the common-mode voltage (CMV) is an issue in a transformerless grid-connected photovoltaic system. In this paper, a modified space vector modulation based on the Fourier transform analysis is proposed to reduce the leakage current in a three-phase quasi-Z-source inverter (qZSI). The CMV harmonic content in a qZSI contains low-and high-frequency harmonics that cause safety and electromagnetic interference problems, respectively. By implementing the proposed modulation in a three-phase qZSI, the low-frequency harmonics of the CMV are mainly reduced. The distribution of the high-frequency harmonics is also modified in a way they can be...