Enhanced Pulse-Density-Modulated Power Control for High-Frequency Induction Heating Inverters

Abstract

This paper presents a 100 kW, 100 kHz IGBT series resonant inverter for induction heating applications that uses an improved power control scheme based on the standard pulse density modulation (PDM). This standard power control is a good solution for the design of high frequency inverters because the output power factor is near to unity in a wide range of output power, resulting in a great reduction of switching losses and electromagnetic noise. However, the output current can be in discontinuous mode especially for resonant loads of low quality factor or for low output power or low load operation. This output current fluctuation produces a high output current ripple that can lead to an increase of power losses and loss of accuracy of the response of the frequency tracking control. The proposed control strategy, called enhanced pulse density modulation (EPDM), provides twice less output current ripple, thus resulting in an improved inverter behaviour in terms of frequency tracking accuracy and energy efficiency. Experimental tests have been made in order to compare the EPDM strategy with standard power control schemes.

Comprehensive Power Control Performance Investigations of Resonant Inverter for Induction Metal Surface Hardening

“…This results is reflected in the efficiency which remains as high as 82% over power variation range. This trend looks similar to the one found in [14,16,18,19]. …”

“…In this case, load adaptive operating frequency using phase locked loop, or slightly higher than resonance frequency are generally applied, in order to achieve inverter soft switching, and hence higher efficiency and power density [4-6-10-11-17]. In the present paper, the work focuses mainly on assessment of the control techniques over a large temperature variation and consequently power range, hence, load adaptation control is not considered at this stage in the present work in order to carry out a comprehensive and fair performance comparison [15][16]. In this case, and to highlight the contribution of this work, an experimental system has been built at low power to keep the cost at minimum, and to be able to conduct a thorough investigation into the system performance which appears later to be consistent and allows their prediction over a wide power range according to industrial standards criteria.…”

Autonomous Energy Matching Control in an LLC Induction Heating Generator

“…The application of the controlled LLC system has repercussions for the generator control system, especially the power control system [22]. On one hand, it creates new regulation capabilities (L s ), but at the same time it introduces new limitations, resulting from both the speed of the temperature changes that occur during induction heating (which affect the electrical parameters) and the mechanical and regulatory choke L s capabilities.…”

Pulse Density Modulation Applied to Series Resonant Inverter and Ac‐Ac Conversion

“…The control part decides the nature of switching cycles (active or inactive). Its application to series resonance inverters has the major advantage to cancel the switching losses and to produce an output power factor near to unity [6][7][8][9][10][11]. The integration of these inverters in the ac-ac conversion makes it possible to save the smoothing filter and to have a sine-wave absorption at full power [6,7].…”

“…The integration of these inverters in the ac-ac conversion makes it possible to save the smoothing filter and to have a sine-wave absorption at full power [6,7]. Several recent researches are devoted to the development of PDM control and to the valorization of its applications [8][9][10][11]. The operating analysis presented in these papers focus on the output current.…”