Julio Walter

A New Simplified Multilevel Inverter Topology for DC–AC Conversion

Multilevel converters offer high power capability, associated with lower output harmonics and lower commutation losses. Their main disadvantage is their complexity, requiring a great number of power devices and passive components, and a rather complex control circuitry. This work reports a new multilevel inverter topology using an H-bridge output stage with a bidirectional auxiliary switch. The new topology produces a significant reduction in the number of power devices and capacitors required to implement a multilevel output. The new topology is used in the design of a five-level inverter; only five controlled switches, eight diodes, and two capacitors are required to implement the five-level inverter using the proposed topology. The new topology achieves a 37.5% reduction in the number of main power switches required (five in the new against eight in any of the other three configurations) and uses no more diodes or capacitors that the second best topology in the literature, the Asymmetric Cascade configuration. Additionally, the dedicated modulator circuit required for multilevel inverter operation is implemented using a FPGA circuit, reducing overall system cost and complexity. Theoretical predictions are validated using simulation in SPICE, and satisfactory circuit operation is proved with experimental tests performed on a laboratory prototype

Training platform for teaching power electronics Using PIC microcontrollers

This paper presents a low cost, high efficiency, power electronics training platform of modular architecture for educational purposes, based on the PIC family of microcontrollers. It can operate both as a stand-alone system or connected to a standard PC. It is design to be programmed with microchip freeware MPLAB. The platform supports laboratory work in the study of the power stages and the study of power electronics controls in real time. A digital light dimmer is developed as one introductory application for the training platform

Simulation of simplified seven level multilevel converter circuit

At present multilevel converters are technically interesting due to their high power handling capabilities, low output harmonics level and reduced requirements in blocking voltages in the switching devices ratings and lower commutation stresses and losses. The multilevel converter configurations now in use have as their main disadvantage their circuit complexity, requiring a great number of power devices and passive components in their implementation, and increasing control circuit complexity. System costs is rather high, and therefore the multilevel inverters are considered cost effective only in very high power applications. In this work a new seven level inverter having a reduced component count is presented, based upon the H bridge with auxiliary switch 5 level architecture. This new configuration may be of interest for applications working at lower and medium power levels. Also a new seven level inverter controller is introduced. The combination of the new power converter topology and the new controller circuit reduces both system cost and complexity.

Using Numerical Methods to Design and Control Heating Induction Systems

Although induction heating systems exists since 1906 (Curtis, 1950) its design always has been an art, with a great emphasis in the designer’s experience. This state of things has not really changed much until the advent of computers and analysis software powerful enough. Now it is possible to use relatively common programs, even free software in some cases, to design and simulate the heating system before any physical device needs to be mounted. This chapter is devoted to show some of these techniques and to present examples that illustrates it.

High frequency generator for an inductive shrinking unit

This work presents the design and tests of a low power (10 kW), medium frequency (100 kHz), inductive heating system, to provide energy to a shrinking unit dedicated to replace the mechanical tool-holders used at present in different machine-tools. The tool holder is a solid ring, which is expanded by the inductive heater to change tools, and cooled to shrink it, holding the tool with a bigger force than the standard mechanical units. The power generator works in resonance, the power switches operate in zero current switching mode (ZCS), and the power control operates in a modified delta mode also known as pulse density control. The power output is continually controlled from 10% to a 100% of maximum, and is regulated against external factors such as variations in input voltage, temperature, and different tool holder sizes and shapes

Active energy recovering snubber for the asymmetric inverter

This paper presents a single capacitor active snubber circuit for the asymmetric inverters used to drive switched reluctance motors. The proposed configuration uses the motor coil inductance as an integral component in the snubber process, acting in sequence to ensure the low-loss commutation of each inverter main power device. The two auxiliary snubber switches naturally commutate in ZCS mode. Only one minor change in the inverter firing sequence is required to include the snubber. Initial simulations in AIMSPICE show that the snubber produces significant reduction in commutation losses without affecting the asymmetric inverter operation. A laboratory prototype is undergoing tests to study the complete operating envelope of the modified inverter driving a switched reluctance motor under DTC control.

Control model of a closed loop power-controlled series-type resonant induction heating system

This work presents the mathematical modeling of a power controlled, resonant operated inductive heating system. Experimentally the power is measured over the heating coil and processed to have the real power as a feedback signal that manages a pulse density (delta) modulator topology with a PID compensation network. The results shows that it is possible to directly control the real output power of the inverter, opening the possibility to obtain information about the energy transferred to the load in situations where this is critical, for example, in precise heating processes.

An improved power electronics training platform using PIC microcontrollers

This work presents an improved Power Electronics Training Platform implemented with PIC microcontrollers. The original training platform, presented in [7], has been improved transferring to a FPGA circuit the control of peripheral components such as LCD displays, keyboards, A/D and D/A converters, and I/O ports. This control transfer reduces the computational load in the PIC, enabling the PIC to perform the main tasks in a faster and more precise way. These enhancements increase the usefulness of the Training Platform as a low cost training tool in a Power Electronics Laboratory.

Experimental Results for the Single Capacitor Single Inductor Active Snubber

In this work the practical results obtained with the Single Capacitor Single Inductor Active Snubber (SCSIAS) circuit using the Diode Bridge Switch Configuration are presented, proving the advantages of this proposed topology, which can be implemented with minimum component count. The SCSIAS configuration ensures that the main power devices undergo a ZVS off-commutation and a ZCS on-commutation, minimizing commutation losses in all operating conditions. Snubber topology also ensures that most auxiliary commutations take place under zero voltage/zero current conditions.