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This paper proposes a cascaded single phase multilevel inverter using an off-the-shelf three-phase inverter and transformer. The concept is based on a cascaded connection of two inverter legs using a typical three phase inverter in such a way that the third leg is shared between the other two phases. The cascaded connection is achieved through an integrated series transformer with a typical three-phase transformer core. Utilization of a special transformer design has been previously proposed in the Custom Power Active Transformer. However, cascaded connection of inverter legs has not been previously investigated with such a concept. In this way, a three-leg inverter and a three-phase transformer are converted into an isolated multilevel single-phase inverter based on an unique configuration and modulation technique.

The three-level neutral-point-clamped (3L-NPC) topology is competitive in the large wind energy conversion systems (WECS) thanks to its simple implementation and proper performance compared to other topologies. However, the 3L-NPC topology does not allow distributing power losses evenly among the switching devices, which limits its output power capability. Current literature focuses on the three-level active neutral-point-clamped (3L-ANPC) as an evolution of the 3L-NPC, enabling a more even power loss distribution. However, some devices still suffer from significant switching and conduction power losses with typical commutation sequences. This paper proposes a novel commutation sequence for a 3L-ANPC inverter leg to force that each device mainly withstands either switching or conduction losses. This enables the selection of optimum devices for each position, resulting in an improved converter loss distribution, thermal performance, efficiency, and output power capability. A 2 MW low-voltage WECS is simulated with an electro-thermal model developed in PLECS, reaching a reduction of around 16% in total switching losses. In addition, an enhanced thermal performance is achieved, reducing the maximum junction temperature increase above ambient temperature, on average for all devices, around 4%. The thermal advantages are considerably higher in certain devices, reaching maximum reductions of around 17% in the maximum junction temperature increase above ambient temperature and about 40% in the maximum device junction temperature variation. All reductions are with reference to the conventional commutation sequence.

n flying capacitor (FC) converters, phase-shifted pulse-width modulation (PS-PWM) provides natural voltage balancing. However, for a practical application, a more robust balancing mechanism of maintaining the FC voltages at the desired values is required. This paper proposes a new closed-loop voltage balancing method for multilevel FC converters using PS-PWM. The proposed method balances the voltages of the FCs by modifying the duty cycle of each switch of the FC converter using a proportional (P) controller. The crossed effect between FC currents and duty cycles is considered and is used for FC voltage balancing. The Simulation results verify that the proposed voltage balancing method is very robust to different operating conditions, such as load transients and non-linear loads.

The teaching of Power Electronics at university Level can be simplified and can be more effective by employing the Switching Function Technique. A unified approach to the operation and analysis of any power converter circuit is possible. The authors tried this approach for a number of years at the Cyprus University of Technology and at Brunel University. This teaching approach is based on the identification of the appropriate switching function which can be applied to a power converter. The switching function is a series of pulses of unity magnitude and it is expressed as a series of sinusoids and its parameters are the ON period of the pulses as well as their phase angles. Analytical expressions of current and voltage waveforms are derived at any point of the circuit -preferably the input and output- as a series of sinusoids. This makes the identification of the order of the harmonics straightforward and the calculation of harmonic magnitude & phase, THD, PF etc. possible.

This research investigates the distortion on the electrical distribution system for a high voltage DC Integrated Power System (IPS). The analysis was concentrated on the power supplied to a propulsion motor driven by an inverter with simulated silicon carbide switches. Theoretically, silicon carbide switches have the advantage of being able to withstand a very large blocking voltage and carry very large forward currents. Silicon carbide switches are also very efficient due to their quick rise and fall times. Since silicon carbide switches can withstand high voltage differentials and switch faster than silicon switches, the switching effects on the electrical distribution system were investigated. The current state of silicon carbide power electronics was also investigated. This research quantifies the current and voltage distortion over various operating conditions. A system model was developed using Matlab, Simulink, and SimPowerSystems. The model consisted of a synchronous generator supplying a rectifier and inverter set driving an induction motor. This induction motor simulates the propulsion motor for a Navy ship. This model had a DC link voltage of 10 kV in order to simulate future Navy IPS systems. The current and voltage distortion were compared to MIL STD 1399 and IEEE STD 519 and 45. http://archive.org/details/analysisofsystem109453006 Contract Number: N62271-97-G-0026 Approved for public release; distribution is unlimited.

Necesidades tecnológicas en la docencia universitaria requieren un sistema para proporcionar electricidad a partir de enchufes en los escritorios del alumnado. Este sistema debe proporcionar una gran movilidad de las mesas para que puedan colocarse según los requerimientos de cada clase. También se deben facilitar las tareas de mantenimiento y limpieza, y evitar el cableado por el suelo para mejorar la accesibilidad a las aulas con silla de ruedas. El sistema consistirá en la alimentación de pequeñas redes de mesas interconectadas entre sí y situadas según la conveniencia de la clase. Las mesas de cada red se proporcionarán electricidad las unas a las otras a partir de una única toma de corriente situada en la pared. Además, el diseño de la mesa tendrá en cuenta los problemas generados por los campos electromagnéticos del cableado. Esto será posible en gran parte por el sistema de descarga electrostática mediante de las propias patas, evitando así el síndrome de lipoatrofia semicircular y pudiéndose aplicar a la gran mayoría de mesas y escritorios con esta misma problemática. En este proyecto, se demuestra la viabilidad de fabricación de este producto mediante el diseño de esta mesa a partir de componentes disponibles en el mercado y componentes fabricados a medida. También se demuestra la viabilidad económica del proyecto, consiguiendo un precio competitivo para una mesa con grandes valores añadidos comparándola con el resto del mercado.

The flying capacitor (FC) multilevel converter requires a capacitor voltage balancing mechanism for proper operation. This paper proposes a voltage balancing scheme for a five-level FC converter based on phase disposition pulse-width modulation (PD-PWM) using transitions that produce the minimum number of switching events. This strategy will be called optimal-transition voltage balancing (OTVB) scheme. Since multiple optimum switching transitions between two consecutive voltage levels may be available, such a redundancy is used to regulate the FC voltages at their desired levels. Those transitions that produce more switching events are avoided. The rest of transitions are evaluated by means of a cost function and the one that produces the minimum value is selected. Simulation results show a significant reduction of the average switching frequency as compared to the use of the optimal-state voltage balancing (OSVB) scheme, while maintaining the balance of the FC voltages. Moreover, the proposed PD-PWM voltage balancing strategy is robust to static and dynamic load conditions.

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This paper proposes a new device by combining features of an interline dual H-bridge current flow controller with the core idea of a hybrid HVdc circuit breaker for meshed HVdc grid application. The proposed device can substitute two dc circuit breakers at a dc bus with at least two adjacent transmission lines. In addition to the current interruption action, the current in one of the adjacent lines can be controlled by the embedded current flow controller. The system-level behavior of the proposed current flow controlling hybrid dc circuit breaker is similar to that of the typical hybrid dc circuit breaker and the interline dual H-bridge current flow controller. The operation principles of the proposed device are introduced and analyzed in this work. The component ratings are compared to the existing solution, and the functionality of the proposed device is verified by simulation.

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works The conventional design of voltage-source power converters is based on a two-level half-bridge configuration and the selection of power devices designed to meet the full application specifications (voltage, current, etc.). This leads to the need to design and optimize a large number of different devices and their ancillary circuitry and prevents taking advantage from scale economies. This paper proposes a paradigm shift in the design of power converters through the use of a novel configurable device consisting on a matrix arrangement of highly-optimized switching cells at a single voltage class. Each switching cell consists of a controlled switch with antiparallel diode together with a self-powered gate driver. By properly interconnecting the switching cells, the switching cell array (SCA) can be configured as a multilevel active-clamped leg with different number of levels. Thus, the SCA presents adjustable voltage and current ratings, according to the selected configuration. For maximum compactness, the SCA can be conceived to be only configurable by the device manufacturer upon the customer needs. For minimum cost, it can also be conceived to be configurable by the customer, leading to field-configurable SCAs. Experimental results of a 6x3 field-configurable SCA are provided to illustrate and validate this design approach.