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Cascaded H-bridge (CHB) multilevel inverters (MLIs) have been widely used for power electronics systems. While high-voltage blocking across power switches is not a constraint for low voltage applications, the research trend has been oriented to the design of more compact module topologies as an alternative for CHB. Despite the generation of more voltage levels with reduced switch count, the existing module topologies in recent literature take no account of the freewheeling current path during dead-time, thus, inducing multistep jumps in voltage levels and giving rise to undesirable voltage spikes. Addressing this concern, this paper proposes two symmetrical compact-module topologies for cascaded MLI, where freewheeling current path during dead-time is provided for smooth transition between voltage levels to prevent voltage spikes. The proposed 7-level and 13-level compact-modules demonstrated low number of conducting switches for all voltage levels. Comprehensive analysis and comparison with the latest module topologies are conducted. To validate the operation of the proposed compact-module topologies, simulation and experimental results are presented. [ABSTRACT FROM PUBLISHER]

This letter proposes an improved symmetrical 4-level submodule as a basic cell for generating multiple dc voltage levels. A hybrid cascaded multilevel inverter (HCMLI) topology is formed by the combination of n submodules and a full-bridge. A comparative analysis against the recent multilevel inverters reveals that the proposed topology requires less number of switches and dc sources. In addition, the proposed submodule reduces the number of conducting switch and gate driver requirements compared to the widely used half-bridge submodule. To validate the operation of the proposed HCMLI topology, experimental results of a 9-level single-phase inverter controlled by selective harmonic elimination pulse-width-modulation is presented. [ABSTRACT FROM AUTHOR]

This paper presents a boost-multilevel inverter design with integrated battery energy storage system for standalone application. The inverter consists of modular switched-battery cells and a full-bridge. It is multifunctional and has two modes of operation: 1) the charging mode, which charges the battery bank and 2) the inverter mode, which supplies ac power to the load. This inverter topology requires significantly less power switches compared to conventional topology such as cascaded H-bridge multilevel inverter, leading to reduced size/cost and improved reliability. To selectively eliminate low-order harmonics and control the desired fundamental component, nonlinear system equations are represented in fitness function through the manipulation of modulation index and the genetic algorithm (GA) is employed to find the optimum switching angles. A seven-level inverter prototype is implemented and experimental results are provided to verify the feasibility of the proposed inverter design. [ABSTRACT FROM AUTHOR]

This paper presents a simple dynamic overmodulation method to obtain a fast dynamic torque response in direct torque control (DTC) of induction machines with constant-switching-frequency controller. A fast dynamic torque response can be obtained by switching only the most optimized voltage vector during torque dynamic condition. The optimized voltage vector can be identified by comparing the rate of change of torque produced between applications of two possible active voltage vectors, according to the flux position. The selection of the optimized voltage vector can be simply implemented by modifying the flux error status before it is being fed to the lookup table. It will be shown that the proposed switching strategy facilitates the DTC to perform under six-step mode to achieve the fastest dynamic torque response. The effectiveness of the proposed dynamic overmodulation to obtain the fast torque response is verified with some experimental results. [ABSTRACT FROM AUTHOR]

A dynamic overmodulation strategy for fast dynamic torque control in direct torque control (DTC)-hysteresis-based induction machine is proposed. The fastest dynamic torque response with a six-step mode can be achieved in the proposed method by switching only the most optimized voltage vector that produces the largest tangential component to the circular flux locus. This paper also discusses the performance of dynamic torque control in basic DTC in order to justify on how the proposed selected voltage vector results in excellent dynamic torque performance. The main benefit of the proposed method is its simplicity, since it only requires a minor modification to the conventional DTC-hysteresis-based structure and does not require a space vector modulator. To verify the feasibility of the proposed dynamic overmodulation strategy, simulation and experimentation, as well as comparison with the conventional DTC scheme, are carried out. Results showed a significant improvement in the dynamic torque response when compared to the conventional DTC-hysteresis-based method. [ABSTRACT FROM PUBLISHER]