This paper describes the implementation of a hybrid energy storage system (HESS) using ultracapacitors (UCs) to protect the batteries of an electrical vehicle (EV) from high-peak currents and therefore extend their lifetime. A field-programmable gate array (FPGA) controlled interleaved bidirectional buck-boost converter working in a discontinuous conduction mode, has been designed to transfer the energy between the batteries and the UCs. The FPGA is responsible of generating all the converter gate signals and implements the control stage needed to smooth the battery current peaks. The control strategy is based on dividing the current demand of the motor into two parts (high-frequency current and low-frequency current), the batteries supply the low frequency part and the UCs supply the high-frequency part. Experimental tests have been carried out driving the EV under different scenarios. Experimental results demonstrate the good behavior of the proposed HESS, although the potential battery life extension is still under quantification. The consumption of the EV has been increased due to the converter losses, this increase is minimum under typical driving scenarios, but is quite important in start-stop driving cycles.

In this paper, a new method to calculate the five parameters of the single-diode model of a photovoltaic cell or panel is presented. This new method takes into account the intrinsic properties of the model equation and the technique of linear least-squares fitting; so, the computational complexity and costs are very low. Moreover, the proposed method, named two-step linear least-squares method, is able to work absolutely blindly with any kind of I-V curve. It does not need initial guesses at all and, consequently, it is not necessary to know previously any information of any parameter. The proposed method provides the parameters of the single-diode model just using the coordinates of N points (N ≥ 5) of the I-V curve. The results provided by this method in a first stage have the same order of accuracy of the best documented methods in the field of parameters extraction, but, furthermore, in a second stage, the best accuracy documented until now is obtained in two important case studies usually used in the literature as well as in a large-scale I-V curve repository with more than one million of curves.

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.

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.

This paper presents a comparison of the behavior of the intrinsic diode of silicon (Si) and silicon carbide (SiC) MOSFETs. The study was done for 1200 V Si and SiC MOSFETs. The data sheet from manufacturers shows the characteristics of MOSFET' intrinsic diode when gate source voltage (V_GS) is 0 V. There are applications where the MOSFET' intrinsic diode is used while V_GS is different than 0 V. One of these applications is induction heating, where depending on the load and the regulation system, the diode can conduct a significant part of the inverter current. In most applications which use the MOSFET' intrinsic diode, the turn ON of the intrinsic diode happens at V_GS = 0 V. After a blanking time, the MOSFET' gate is activated waiting for the direction change of current in the circuit. Therefore, most of the current through the MOSFET' intrinsic diode occurs with a V_GS different of 0 V. This paper shows the direct output characterization of Si and SiC MOSFET' intrinsic diode under different gate voltages. The gate resistor (R_G) is an important parameter of the characterization. Depending on the input capacitance of the Si or SiC MOSFET, different R_G are needed. The turn-on and turn-off behaviors are obtained when RG is optimized for each Si and SiC MOSFET. This has result in the turn-off robustness of intrinsic diode with optimum R_G. This paper presents a surprising result for the reverse characteristic of Si and SiC MOSFETs for the same current at different V_GS. The technology of Si MOSFET has different behavior depending on the manufacturer. The technology of SiC MOSFET presents a very similar behavior to low-voltage Si MOSFETs.