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In several electrical dc–ac power conversions, the ac output voltage is higher than the input voltage. If a voltage-source inverter (VSI) is used, then an additional dc–dc boosting stage is required to overcome the step-down VSI limitations. Recently, several impedance source converters are gaining higher attentions [1], [2], as they are able to provide buck-boost capability in a single conversion stage. This paper proposes the merging of the boost stage and the VSI stage in a single stage dc–ac power conversion, denoted as split-source inverter (SSI). The proposed topology requires the same number of active switches of the VSI, three additional diodes, and the same eight states of a conventional space-vector modulation. It also shows some merits compared to Z-source inverters, especially in terms of reduced switch voltage stress for voltage gains higher than 1.15. This paper presents the analysis of the SSI and compares different modulation schemes. Moreover, it presents a modified modulation scheme to eliminate the low frequency ripple in the input current and the voltage across the inverter bridge. The proposed analysis has been verified by simulation and experimental results on a 2.0-kW prototype. [ABSTRACT FROM PUBLISHER]

This paper discusses the use of a cascaded multilevel converter for flexible power conditioning in smart-grid applications. The main feature of the proposed scheme is the use of independent dc links with reduced voltages, which makes such a topology an ideal candidate for medium- and high-power applications with increased reliability. The developed control strategy regulates independent dc-link voltages in each H-bridge cell, and allows the selective and flexible compensation of disturbing currents under a variety of voltage conditions without requiring any reference frame transformation. The selective control strategies are based on the decompositions proposed in the conservative power theory, which result in several current-related terms associated with specific load characteristics. These current components are independent of each other and may be used to define different compensation strategies, which can be selective in minimizing particular effects of disturbing loads. Experimental results are provided to validate the possibilities and performance of the proposed control strategies, considering ideal and deteriorated voltage conditions. [ABSTRACT FROM PUBLISHER]

In order to increase the output voltage levels and reduce the isolated dc sources, a symmetrical hybrid nine-level inverter for high-speed motor drive applications is presented in this paper. Each phase of this inverter is composed of a five-level dc/dc converter cell and an H-bridge cell. The dc/dc converter is operated at high frequency with low-voltage devices and the H-bridge is operated at fundamental frequency with high-voltage devices. The three phases are connected to a common dc-link and each drives an isolated winding of an open-winding motor. The operating principles and modulation method are introduced. A detailed analysis of the average currents through the flying capacitor and neutral point of the dc-link is presented and a capacitor voltage balancing method based on phase-shifted pulse-width modulation is proposed. Simulation and experimental results are presented to demonstrate the feasibility of this topology and control method. [ABSTRACT FROM PUBLISHER]

A new zero-sequence circulating current (ZSCC) reduction method for multimodule voltage source inverters (MVSIs) consisting of P three-phase inverters that are connected in parallel is proposed in this paper. Four-switch inverter modules are used instead of the conventional six-switch modules to reduce the cost. In this paper, the effectiveness of the proposed ZSCC reduction method is studied using selective harmonic elimination pulse width modulation. The proposed ZSCC reduction method can remove about P times the number of harmonics using the same switching frequency as compared to more conventional methods, as explained later in this paper. The concepts discussed in the paper are confirmed with results obtained from an MVSI experimental prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a unified PWM method for matrix converters so as to establish a common platform which can generate various types of PWM methods in real time by adjusting the free parameters in the modulation algorithm. As a foundation for unification, the general form of the modulation functions for matrix converters is derived using geometric transformation approach. All eligible direct modulation matrices are shown to be of indirect form and are expressed in terms of instantaneous phase quantities. This paper also presents a new viewpoint to consider a matrix converter as a generalized three-level inverter and to apply the double-carrier-based dipolar modulation technique of the three-level inverter to the matrix converter. Several concepts of the two-level PWM inverters are then generalized to the matrix converters for better visualization and understanding of the modulation process. [ABSTRACT FROM AUTHOR]

Hybrid cascade multilevel inverters combine semiconductor devices of different voltage ratings and technologies, which theoretically allow high efficiency to be achieved. The bottlenecks of these topologies are, however, the need for isolated supplies for the cells and the lack of modularity. This paper focuses on the design and control of high-resolution, high-efficiency multilevel inverters with simplified dc power supplies. It introduces several rules for systematically designing the dc voltages of the cells, for which all unsupplied capacitor voltages can be regulated. Six classes of inverters are obtained covering single- and three-phase, staircase and pulsewidth-modulated (PWM) inverters. New configurations of hybrid cascade multilevel inverters are obtained for each class. A double modulation strategy with two different frequencies is proposed that allows switching losses of PWM inverters to be reduced. Decoupled mechanisms are proposed for the total and internal energy balances. It is shown how to make the design robust by taking into account conversion losses and large dc-voltage imbalances in the design and control. An analysis of the maximum voltage utilization and efficiency of the resulting configurations is carried out. The effectiveness of the novel concepts is validated experimentally for two of the proposed topologies. [ABSTRACT FROM PUBLISHER]

The advancement in power electronics has made the use of any number of phases in ac machines possible since with the inverter, any number of phase voltages can be realized as long as the corresponding inverter exists. To supply multiphase drives requires multiphase voltage source inverters (VSIs) whose output voltages depend very much on the methods of generating the pulses to turn on and turn off the inverter devices appropriately. This paper presents an analytical technique for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse width modulation schemes for two-level, five-phase voltage source converters. These expressions can be used for both balanced and unbalanced phase voltages generated by any two-level multiphase inverter, in generating the required reference signals appropriately. An example of a five-phase VSI is presented to illustrate the strategy. Simulation and experimental results are presented in which a close examination shows that both results are similar for the balanced and unbalanced load voltage cases. [ABSTRACT FROM AUTHOR]

This paper extends the Z-source concept to matrix converters and explores a family of Z-source matrix converters. Their principles and characteristics are analyzed, and a simplified voltage-fed Z-source matrix converter is used as an example to demonstrate its operation, voltage gain versus modulation index, PWM method, boost control, and implementation of the control. Both simulation and experimental results verify operation of the proposed Z-source matrix converter, analytical results, and control method. The Z-source converters can achieve buck and boost operation with reduced number of switches needed, therefore achieving low cost, high efficiency, and reliability, compared to the traditional matrix converters. [ABSTRACT FROM AUTHOR]

This paper presents first an overview of the well-known voltage and current dc-link converter topologies used to implement a three-phase PWM ac–ac converter system. Starting from the voltage source inverter and the current source rectifier, the basics of space vector modulation are summarized. Based on that, the topology of the indirect matrix converter (IMC) and its modulation are gradually developed from a voltage dc-link back-to-back converter by omitting the dc-link capacitor. In the next step, the topology of the conventional (direct) matrix converter (CMC) is introduced, and the relationship between the IMC and the CMCs is discussed in a figurative manner by investigating the switching states. Subsequently, three-phase ac–ac buck-type chopper circuits are considered as a special case of matrix converters (MCs), and a summary of extended MC topologies is provided, including three-level and hybrid MCs. Therewith, a common knowledge basis of the individual converter topologies is established. [ABSTRACT FROM PUBLISHER]