E. Sanchis-Kilders

Improving the Efficiency of IGBT Series-Resonant Inverters Using Pulse Density Modulation

This paper analyzes a high-power (50 kW) high-frequency (150 kHz) voltage-fed inverter with a series-resonant load circuit for industrial induction heating applications, which is characterized by a full bridge inverter made of insulated-gate bipolar transistor and a power control based on pulse density modulation (PDM). This power control strategy allows the inverter to work close to the resonance frequency for all output-power levels. In this situation, zero-voltage switching and zero-current switching conditions are performed, and the switching losses are minimized. An additional improvement of inverter efficiency is achieved by choosing appropriate values of the modulation index. Results are verified experimentally using a prototype for induction hardening applications. A comparative study between the PDM and the classical power control by frequency variation will be made.

A bidirectional and isolated three-phase rectifier with soft-switching operation

A bidirectional-power-flow three-phase rectifier with high-frequency isolation and all-digital control, based on the matrix converter topology, is analyzed in this paper. The selected topology consists of a bidirectional three-phase-to-single-phase reduced matrix converter with power-factor correction and a bidirectional active rectifier. The inclusion of the isolation transformer at the switching frequency permits the reduction of volume and weight. By synchronizing the commutation of both converters and adding a saturable inductor and a blocking capacitor it is possible to achieve soft commutation for most of the semiconductor elements. An all-digital control based on a digital-signal-processor and a field-programmable gate array was used to implement space-vector modulation and output current regulation. This power converter is intended to feed the low-energy correction magnet of a particle accelerator. Experimental results of a 1.5-kW 20-kHz prototype are presented to illustrate the performance of the proposed topology.

Improving the Reliability of Series Resonant Inverters for Induction Heating Applications

This paper analyzes a high-power (100-kW) high-frequency (50-kHz) voltage-fed inverter with a series resonant load circuit for industrial induction heating applications which is characterized by a full-bridge inverter composed of isolated-gate bipolar transistors and a new power control based on phase-shift (PS) control. This power control circuit incorporates a load-adaptive variable-frequency controller and automated blanking time management in order to allow the inverter to work in zero-voltage switching for all output power levels and load conditions. An important improvement of the inverter reliability is achieved by choosing an appropriate and novel switching sequence for the PS inverter. The results are verified experimentally using a prototype for induction hardening applications. A comparative study between the proposed and standard PS power control will be made.

Soft switching bidirectional converter for battery discharging-charging

This paper presents the results of a project that looked after a high efficiency bidirectional converter which could be used as a battery discharge/charge regulator when the bus voltage is above the battery voltage. High efficiency, high stability and simplicity are the main goals, no galvanic isolation is required. Taking into account all these parameters, our proposed solution has been a new topology based on a boost converter with coupled inductors. The use of a bidirectional converter reduces the mass of the overall charge/discharge subsystem and lowers cost and component count. In the project, its use is intended for space applications, but telecom, automotive or similar applications can also benefit of this new concept.

High-Efficiency Regulation Method for a Zero-Current and Zero-Voltage Current-Fed Push–Pull Converter

A new high-efficiency regulation method for a zero-current and zero-voltage current-fed push-pull converter is presented. The method proposed is based on the use of a controlled transformer as a post-regulator, which adds or subtracts an additional voltage to the output filter of the converter. An auxiliary regulator, which only handles a percentage of the output power, controls this transformer, and therefore, results in much higher efficiency than a normal preregulator would have. The novelty of the presented converter is that regulation is achieved without affecting the zero-voltage and zero-current switching in any working conditions. Small- and large-signal models of the converter have been developed and a low-power prototype has been simulated and implemented. The good agreement, between the experimental simulations and theoretical results, validates the theoretical developments.

Comparative Study of a Single Inverter Bridge for Dual-Frequency Induction Heating Using Si and SiC MOSFETs

The induction surface hardening of parts with nonuniform cylindrical shape requires a multifrequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply composed by a single inverter circuit and a specially designed output resonant circuit. The whole circuit supplies simultaneously both medium- and high-frequency power signals to the heating inductor. An initial study is made to select the most appropriated topology for this application. The resonant output circuit is analyzed, and a design procedure is presented. The selected inverter operation is described and simulated. Simulations are experimentally verified on a 10-kW dual-frequency resonant inverter operating at 10 and 100 kHz using MOSFETs of silicon (Si) and silicon carbide (SiC) technology. A comparative study is presented based on the measurements of power losses and the energy efficiency of the inverter using both types of MOSFETs.

Induction heating inverter with simultaneous dual-frequency output

Induction surface hardening of parts with nonuniform cylindrical shape requires a multi-frequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply composed by a single inverter circuit and a specially designed output resonant circuit. The whole circuit supplies simultaneously both medium and high frequency power signals to the heating inductor.

High Power Resonant Inverter with Simultaneous Dual-frequency Output

Induction surface hardening of parts with non-uniform cylindrical shape requires a multi-frequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply constituted of an only inverter circuit and a specially designed output resonant circuit. The whole circuit supplies both medium and high frequency power signals to the heating inductor simultaneously

Bidirectional Coupled Inductors Step-up Converter for Battery Discharging-Charging

The present paper shows the preliminary results of a project that looks for a high power, high efficiency bidirectional step-up converter which could be used as a battery discharge/charge regulator. High efficiency and low mass are the main goals, no galvanic isolation is required and MTBF should be as large as possible. Taking into account all these parameters our proposed solution has been a new topology based on a boost converter with output filter and that couples input and output inductor. The use of a bidirectional converter reduces the mass of the overall charge/discharge subsystem and lowers cost and component count. Stability has been studied theoretically and verified experimentally

High power passive soft switched interleaved boost converters

The present project was developed in order to find a high power (/spl ges/5 kW), high efficiency step-up converter which could be used as a battery discharge regulator. Efficiency should be higher than 97%, mass should be lower than 2.5 kg, no galvanic isolation was required and MTBF should be as large as possible. Taking into account all these parameters our proposed solution has been two interleaved boost converters with passive soft switching.