H-bridge | EPFL Graph Search

An H-bridge is an electronic circuit that switches the polarity of a voltage applied to a load. These circuits are often used in robotics and other applications to allow DC motors to run forwards or backwards. The name is derived from its common schematic diagram representation, with four switching elements configured as the branches of a letter "H" and the load connected as the cross-bar. Most DC-to-AC converters (power inverters), most AC/AC converters, the DC-to-DC push–pull converter, isolated DC-to-DC converter most motor controllers, and many other kinds of power electronics use H bridges. In particular, a bipolar stepper motor is almost always driven by a motor controller containing two H bridges. General H-bridges are available as integrated circuits, or can be built from discrete components. The term H-bridge is derived from the typical graphical representation of such a circuit. An H-bridge is built with four switches (solid-state

Etude formelle pour la synthèse de convertisseurs multiniveaux asymétriques

Jean-Sébastien Mariéthoz

The multilevel converters allow generating a voltage waveform whose magnitude and quality are higher than those of conventional converters. They are devoted to medium and high-voltage, high-switching-frequency applications. Among the series connected cell inverters, the symmetrical multilevel inverters are made of identical cells, which topology is generally the H-bridge inverter. This dissertation deals with asymmetrical multilevel converters, which combine high-voltage cells — made of low conduction loss switches — with low-voltage cells — made of low switching loss switches. The different cells play different roles. The goal is to design a converter that has both better energetic efficiency and higher resolution with the same number of cells. This dissertation develops a set of tools that allows synthesizing an asymmetrical multilevel converter. It develops the cell combination rules, which allow defining several cell association classes. The inverter step uniformity condition determines the finesse that can be reached. The optimized modulation condition allows to reduce the highvoltage cell switching frequency without changing the low-voltage cell switching frequency. This property is essential to derive benefit from combining switches of different characteristics. The power balance condition determine how to control the power sharing between the cells. These association classes are different for the single-phase converters and the three-phase converters — without neutral wire. They allow to select a configuration suitable for a given application. Furthermore, several ways that allow improving the inverter resolution are investigated. The modulation is essential to associate a high-quality signal (which will really be delivered to the load by means of the inverter levels) to the reference signal (which should ideally be applied to the load). The modulator evaluation methods are assessed. An approach—based on the modulated signal decomposition in elementary frames—is proposed. The main modulator drawbacks are highlighted. A modulator—which arrange the frames in order—allows to reduce the modulated signal distortion and number of transitions. The specific control methods that allow to minimize the inverter number of switchings are developed. The active power cell supply implies several conversion stages, which decrease the converter energetic efficiency. Some solutions that allow to reduce these losses are proposed. Finally, this dissertation attempts to determine, which are the more interesting solutions, depending on the application.

EPFL2005

Modular Converter Architecture for Medium Voltage Ultra Fast EV Charging Stations: Dual Half-Bridge-based Isolation Stage

Behrooz Bahrani, Niklaus Burger, Alfred Rufer, Michail Vasiladiotis

The concept of ultra fast charging of Electric Vehicles (EVs) is expected to contribute significantly to their widespread utilization in long-distance travels. Towards this direction, emerging power electronic topologies will be the key components of the developed charging infrastructures. Lately, a novel converter architecture has been proposed for such a purpose. The latter is based on a Cascaded H-Bridge (CHB) converter with integrated battery energy storage systems, which play the role of a buffer in such a power demanding application. This paper is focusing on the isolated DC/DC conversion stage, which is needed for the achievement of the high charging currents. The dual half-bridge (DHB) converter is chosen, which fulfills several requirements for the studied application. The soft switching operation of the converter under wide input-output voltage variations is discussed. Moreover, a current controller is designed, capable of dealing with the topology-specific challenges. Finally, the development of a down-scaled laboratory prototype is described and experimental results are provided.

2014

A flexible and robust power management mechanism based on single-phase Modular Multilevel Converter with integrated energy storage elements

Alfred Rufer, Rosa Martel Danoary Tsirinomeny, Minghao Xu

This paper deals with a power management mechanism using Modular Multilevel Converter (MMC) with integrated energy storage elements, the typical use of which could be a grid-interface for a photovoltaic park or a charging park for electric vehicles. In comparison with the currently commonly used topologies of MMC, which use submodule DC/DC converters to control the submodule voltages at the half-bridge side and see the energy storage elements as the distributed voltage sources of MMC, the proposed topology in this paper put additionally a buffer capacitor between the submodule halfbridge and the DC/DC converter, taking this capacitor as the direct voltage source of MMC. Consequently, the energy balancing system will be targeted on the energy stored in these buffer capacitors, regarding the power flow gone from these capacitors to the final energy storage elements as disturbances for the controllers. One of the main advantages of this proposal is the healthy operation of MMC under fault-condition of its submodule energy storage elements, which serves to guarantee a stable and robust connection to power grids. Moreover, the power flow of the energy storage elements is free from the energy balancing task and thus can be controlled independently and individually, ranging from zero to the maximum output power of the energy storage elements. This is a beneficial characteristic for a PV park with large scale and various input power of its battery packages or for an EV-charging park to charge different battery packages inside different vehicles with their own best charging profile at the same time within a single MMC.

2015

Etude formelle pour la synthèse de convertisseurs multiniveaux asymétriques

Jean-Sébastien Mariéthoz

EPFL2005