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This paper presents a torque ripple minimization method for a permanent magnet synchronous motor (PMSM) drive system that utilizes a modified quasi-Z-source (qZS) inverter. The proposed modified qZS network is designed by adding an extra switching device to the conventional qZS topology and provides a wider range of capabilities for inverter input voltage control, e.g., both step-up and step-down operations. It also allows for modification of the traditional switching sequence selection scheme when using the space vector modulation (SVM) for switching. The provided flexibilities are leveraged to develop a control system that minimizes the torque ripples during PMSM operation while satisfying conventional control objectives such as shaft speed control. The control system is comprised of an input voltage optimization subsystem with the goal of torque ripple minimization, which provides the reference for a cascaded modulated model predictive control subsystem for the modified qZS network control, and a motor side predictive control subsystem. The control system employs a new switching sequence selection scheme for SVM modulation to further reduce PMSM torque ripples. Experimental results are provided to validate the theoretical outcomes. [ABSTRACT FROM AUTHOR]

This paper develops a modulation based fault-tolerant (FT) strategy for restoring the operation of three-phase modular multilevel converters (MMCs) with faulty switches. This FT strategy is based on a proposed modified space vector modulation (SVM) technique that generates balanced line-to-line (line) voltages even in the case of a fault occurrence. In the postfault operation, the proposed strategy is able to restore the fundamental amplitude of the line to the neutral (load) voltages to that of the normal operation condition with a slightly increased voltage stress over the switches in the faulty phase. In this paper, first a brief background about MMCs and SVM technique is provided. Then, the proposed FT strategy and the modified SVM technique are presented. Finally, several simulation and experimental results are provided to validate operation of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a new modulated model predictive control method for the control of modular multilevel converters (MMCs) in voltage source converter-high voltage dc systems. The proposed method retains the advantages of the conventional finite control set-model predictive control methods by programing the nonlinear properties of the MMC into the design calculations while minimizing the ac line and circulating current ripples and steady-state error by generating modulated switching signals with a fixed switching frequency. In this paper, first, the predictive modeling of the MMC is provided. Next, the proposed control method is described. Then, the application of the proposed method to an MMC system is detailed. Finally, experimental results from an MMC system connected to a three-phase grid are provided to validate the theoretical outcomes. [ABSTRACT FROM AUTHOR]

This work proposes a new multiobjective modulated model predictive control (MPC) method for control of power electronic converters. The proposed method retains the advantages of conventional MPC methods in programing the nonlinear effects of the converter into the design calculations to improve the overall dynamic performance of the system and builds upon that by offering a new modulation technique for MPC to minimize the voltage and current ripples through by using a fixed switching frequency. To demonstrate the effectiveness of the proposed method, it has been used to overcome the stability problems caused by a constant power load in a multi converter system as a case study. Experimental results from a prototype cascaded converter system are provided to validate the theoretical outcomes. [ABSTRACT FROM PUBLISHER]

This paper presents a new high-frequency modulation method for multilevel converters. The proposed method provides a broad linear operating range and can be digitally implemented with minimal computational effort. This modulation method creates a phase voltage composed of a rectangular component superimposed on the top of a quasi-square-shaped reference function. The reference functions are defined such that the utilization of the dc-link voltage is maximized in any modulation index, while the dv/dt of the switches is always the minimum possible value. In order to implement the proposed method, an update time that is much shorter than the fundamental period is defined in the algorithm for updating the rectangular components of the reference voltage. The high-frequency rectangular component can then be imposed on the reference function to generate the final switching function by switching between two voltage levels during the time between two update instances. Several experimental results are provided to evaluate the performance of the proposed method and to compare its operation to conventional methods. [ABSTRACT FROM PUBLISHER]

This paper proposes a new fault-tolerant strategy for a multilevel converter with an integrated impedance-source network. The proposed fault-tolerant strategy leverages the flexibility provided by the impedance-source network to implement the fundamental phase-shift compensation (FPSC) method in order to restore operation of a multilevel converter with one or more faulty switches to the prefault conditions. In case of a fault occurrence, the proposed fault-tolerant strategy makes the most use of the remaining converter capacity and generates balanced line-to-line voltages, while evenly distributing an inevitable voltage stress increase, over all converter switches. In this paper, first, a brief background about an impedance-source based cascaded H-bridge converter and a suitable modulation method for it is provided. Then, the FPSC method is explained and the proposed fault-tolerant strategy based on this method is introduced. Finally, several experimental results from a prototype converter are provided to validate the operation of the proposed strategy. [ABSTRACT FROM PUBLISHER]

This paper proposes a new fault-tolerant strategy for the purpose of revamping the performance of three-phase multilevel (ML) converters with faulty switches. The proposed fault-tolerant strategy is based on an adaptation of the modified space vector modulation (SVM) technique to the fundamental phase-shift compensation method. The proposed fault-tolerant strategy generates balanced line-to-line voltages with increased voltage levels in the faulty condition. In this paper, first a brief background about cascaded H-bridge (CHB) ML converters and SVM technique is provided. Then the proposed fault-tolerant strategy and the modified SVM technique are presented. Finally, several experimental results are provided to validate operation of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a new fault-tolerant strategy to revamp performance of three-phase multilevel converters with a single faulty switch. The proposed fault-tolerant strategy is based on the application of a modified selective harmonic elimination (SHE) technique in conjunction with the fundamental phase-shift compensation method. The proposed fault-tolerant strategy makes the most use of the converter capacity in the faulty condition, generates balanced line voltages, and eliminates a wide range of lower order harmonics to limit the total harmonic distribution of the converter voltages in the faulty condition. In this paper, first, a brief background about cascaded H-bridge multilevel converters and SHE technique is provided. Then, the proposed fault-tolerant strategy and the modified SHE technique are presented. Finally, several experimental results are provided to validate the operation of the proposed strategy. [ABSTRACT FROM PUBLISHER]