The study of five-level inverters with the various PWM
The energy indicators of multilevel voltage converters are analyzed. The relevance of the research is indicated by the increasing demands of technological processes for the economic use of electric energy, the reduction in power consumed by semiconductor converters, and also to the level of regulated reactive power. The converter considered is a five-level voltage inverter. As the topology of the converter, the structure of the inverter on H-bridges is considered. The article presents two-stage three-phase circuits with the connection of inverter cells to wye. Possible states of electronic keys and their corresponding operating modes are described. The voltage of constant voltage sources is 535 V. In the article algorithms for the formation of pulse-width modulation (PWM) are considered: Phase Opposition Disposition, Alternative Phase Opposition Disposition and Hybrid methods with zero sequence sinusoidal shape of the modulate voltage or with triangular shape of the modulate voltage. As a criterion for evaluating the quality of the inverter's output voltage, total harmonic distortion and line-to-line voltage were adopted. A harmonic voltage spectrum is developed for various control methods of the converter. Possible ways of reducing the harmonic coefficient, as well as increasing the amplitude modulation factor, are shown, by using various methods of forming the pulse-width modulation.
Investigation on cascade multilevel inverter with symmetric, asymmetric, hybrid and multi-cell configurations
In recent past, numerous multilevel architectures came into existence. In this background, cascaded multilevel inverter (CMLI) is the promising structure. This type of multilevel inverters synthesizes a medium voltage output based on a series connection of power cells which use standard low-voltage component configurations. This characteristic allows one to achieve high-quality output voltage and current waveforms. However, when the number of levels increases switching components and the count of dc sources are also increased. This issue became a key motivation for the present paper. The present paper is devoted to investigate different types of CMLI which use less number of switching components and dc sources and finally proposed a new version of Multi-cell based CMLI. In order to verify the proposed topology, MATLAB – simulations and hardware verifications are carried out and results are presented.
New Control Strategy of Three-Phase Five-Level NPC Rectifier -Inverter System for Induction Machine Drive
Abstract This paper proposes a control strategy of a three –phase five-level double converter for induction motor drives. The converter consists of the five-level NPC rectifier, DC link, and the five-level NPC inverter. In this control strategy, the DC link voltages are controlled by using a closed loop with an optimized stabilization system called clamping bridge. It provides a fast and flexible control of the converter capacitor voltage. This method will redress the imbalance of DC link voltage. This control strategy is completely independent from the load control, leading to a simpler implementation. The three-phase five-level NPC rectifier-inverter system is an ideal interface between a utility and renewable energy sources such as photovoltaic or wind generator.