IEEE Transactions on Power Electronics Abstract-This paper presents new Space Vector Pulse-Width Modulation (SVPWM) strategies for a single-phase three-level buck-boost Neutral Point Clamped (NPC) inverter coupled with Impedance-Source (IS) networks. These strategies can be implemented for systems with any IS networks with neutral point. The case study system is based on the quasi-Z-source inverter with continuous input current. To demonstrate an improved performance, the strategies are compared with a traditional pulsewidth modulation strategy. The advantages lie in reduced switching number, without output voltage quality distortion. The simulation and experimental results confirm the theoretical predictions.
I. INTRODUCTION Present technologies and innovations have led to the expansion of Photovoltaic (PV) energy generation systems worldwide [1]-[4]. PV energy sources are characterized by a wide output voltage and power variation. The solar irradiation level changes significantly during the day and gives a variable output power. Also, the shading or high operating temperature of the PV module leads to a significant out-voltage drop. Therefore, the converter for a PV system should have a wide input voltage and output load regulation range.To extend the input voltage regulation range, solutions based on Impedance-Source (IS) networks have been proposed [5]- [11]. They have a buck mode, a boost mode and do not suffer from the Shoot-Through (ST) [5] states compare to the conventional grid-connected inverters.
This paper presents a comprehensive analytical comparison of the impedance-source-based dc-dc and dc-ac converters in terms of the passive component count and size, semiconductor stress, and range of input voltage variation. The conventional solution with a boost converter was considered as a reference value. The main criterion of the comprehensive comparison was the energy stored in the passive elements, which was considered both under a constant and predefined high frequency current ripple in the inductors and the voltage ripple across the capacitors. Main impedance-source converters with or without a transformer and with or without inductor coupling were analyzed. Dc-dc and dc-ac applications were considered. Selective simulation results along with experimental verification are shown. The conclusions provide a selection guide of impedance-source networks for different applications taking into account its advantages and disadvantages.
This paper provides an analytical overview of different impedance sources networks. General classification and main properties of different impedance source networks and their modifications are summarized and presented.
Solutions for a family of the novel three-level neutral-point-clamped (NPC) inductor-capacitor-capacitor-transformer (LCCT)-derived three-phase inverters are described and compared. Component design guidelines and steady state analysis, current and voltage waveforms are given. The authors' simulation results confirm the theoretical predictions. It was found that an asymmetrical three-level NPC LCCT-derived inverter with a single diode in the impedance source network is the most promising solution. Experimental results for an asymmetrical three-level NPC LCCT-derived inverter with a single input voltage source and continuous input current are presented. The main advantages and design requirements are discussed.
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