Buck-boost Voltage Source Inverter Research Articles

A Novel Single-Stage Buck–Boost Inverter

Traditional nonisolated multilevel inverters based on the buck–boost principle usually have some disadvantage such as necessary dead time or capacitor precharging. To overcome these, a new transformerless single-stage buck–boost voltage source inverter topology and its control method are proposed. In addition, the proposed topology has greater advantages in cost and loss. In this letter, the topological characteristics and working mode of the inverter are analyzed, and a modulation scheme that can ensure the balance of the output capacitor voltage is designed. Finally, a hardware experimental prototype is built, and the proposed scheme is experimentally verified based on DSP TMS320F28335 and FPGA XC6SLX9-2TQG144C digital controller.

Multi-Input Ćuk-Derived Buck-Boost Voltage Source Inverter for Photovoltaic Systems in Microgrid Applications

This paper presents a multi-input Ćuk-derived Buck-Boost voltage source inverter (CBBVSI) for Photovoltaic (PV) systems. The proposed topology consists of a single-stage DC-AC inverter that combines both DC-DC and DC-AC stages. The DC-DC stage is used for stepping-up the voltage from the PV generator. Simultaneously, the DC-AC stage is used for interfacing the PV source with the AC grid. The topology allows three sources to utilize the antiparallel diodes for each inverter leg for transferring the energy. The proposed system exhibits several features such as a reduction of the number of components compared to typical two-stage structures, and Split-Source Inverter (SSI), and Z-Source Inverter (ZSI) topologies. Moreover, the power of each PV source can be harvested either simultaneously or separately since independent Maximum Power Point Tracking (MPPT) is performed. The system was simulated using MATLAB/SIMULINK software and a 1 kW laboratory prototype was implemented to verify the operation of the proposed CBBVSI. The numerical simulations are presented together with the experimental results, showing a good agreement.

Operation Modes Analysis and Limitation for Diode-Assisted Buck–Boost Voltage Source Inverter With Small Voltage Vector

Diode-assisted buck-boost voltage source inverter (VSI) boosts the dc source voltage by introducing diode-assisted capacitor network. With parallel capacitive charging and series capacitive discharging, the new topology extends voltage regulation range and avoids extreme duty ratio of switching devices in the front boost circuit. As for the unique structure, various novel pulse-width modulation strategies are provided to obtain the linear voltage gain with regard to the chopped intermediate dc-link voltage of the inverter bridge in one switching time period. It provides a competitive solution for high voltage gain applications. However, when the inverter supplies inductive or capacitive load with extreme low load power factor, the unidirectional current flow of the diode may limit the application of the converter utilizing small voltage vectors for ac output voltage extension. As a result, diode-assisted buck-boost VSI exhibits new operation mode that has not been discussed before. This paper makes a detailed circuit analysis of the relationship between the undesired operation condition and load power factor. Then, a simple approach to totally eliminate the undesired limitation by replacing the diodes with controlled switching devices is provided. Finally, the related simulations and experiments are implemented to verify all the theoretical findings and solutions.

Improved Pulse –Width Modulation Strategies for Voltage Source Inverter

The power electronics are gaining more popularity because of their user friendly behavior. Here the recently proposed improved PWM strategies are compared and the performances in the field of harmonic reduction are traced out. The strategies one prior to other helps in reducing the harmonics and gives the topology a major breakthrough in the field of voltage source inverters. The diode assisted buck-boost voltage source inverter with the recently proposed improved strategies enhances the voltage boost capability with a low boost duty ratio. The efficient use of the intermediate DC-link voltage by the two improved strategies achieves high gain and alleviates the stresses occurring across the switches in the circuit. The work exposes the performance of the respective strategies with help of the harmonic spectra and graphs are drawn to analyze the dependence of the THD with the variation of the load inductance and the duty ratios.

Improved Pulse-Width Modulation Strategies for Diode-Assisted Buck–Boost Voltage Source Inverter

The recently proposed diode-assisted buck–boost voltage source inverter (VSI) enhances the voltage boost capability greatly without extreme large boost duty ratio, which is more suitable for wide range voltage regulation in dc/ac power conversion. This paper mainly explores pulse-width modulation (PWM) strategies for diode-assisted buck–boost VSI and their relationship of voltage gain versus voltage boost duty ratio. In view of variable intermediate dc-link voltage, two kinds of improved PWM strategies with high dc-link voltage utilization are presented to obtain the maximum linear voltage gain in theory, as well as to minimize the voltage stress of switching devices. The operation principle, and the relationship of voltage gain versus voltage boost duty ratio and switching device voltage stress versus voltage gain are analyzed in detail. The related simulation and experiments are implemented to verify the theoretical analysis. Compared with existing counterparts, diode-assisted buck–boost VSI with improved PWM strategies demonstrates good performances: less switching device requirement and higher efficiency at high voltage gain. Owing to improved performance, diode-assisted buck–boost VSI is more promising and competitive topology for wide range dc/ac power conversion in a renewable energy application. Furthermore, the idea of improved modulation strategies can also be extended to the control of diode-assisted buck–boost current source inverter.