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An analog behavioral model of high power gate turn-off thyristor (GTO) is developed in this paper. The fundamental methodology for the modeling of this power electronic circuit is based on the use of the realistic diode consideration of non-linear junctions. This modeling technique enables to perform different simulations taking into account the turn-on and turn-off transient behaviors in real-time. The equivalent circuits were simulated with analog software developed in our laboratory. It was shown that the tested simple and compact model allows the generation of accurate physical characteristics of power thyristors under dynamic conditions. The model understudy was validated with analog simulations based on operational amplifier devices.

The commands of variable-speed high-power drives are currently main problems for electronic power equipment designers faced with the increase of system complexity [

Principle of diagnosis based on the comparison between the real process and its equivalent model [

Therefore, this redundancy is expressed by analytical models described by mathematical equations (or other models) deduced from the fundamental physic laws, representing causal relationships between the signals in the system. The measurements obtained from different captors integrated in the system can then be connected by these models. The diagnosis is so explored by verifying a consistency control between the data collected by the observation system and those predicted by the model [

The difficulties encountered with the use of numerical mathematical models [

It is interesting to note that before the emergence of numerical simulations, the electronic and electrical engineering researchers suffer due to the lack of the adequate computation tools suitable for the achievement of relevant analog simulations. Since the numerical simulation widened its sphere of activity, it becomes the tool mostly used than analog simulation [

For this reason, we develop in this paper the principle of analog modeling dedicated to the most useful electronic components such as the capacitor, the inductor. These elements are simulated conventionally with an analog calculator from their characteristic equations based on the analysis of voltage variables. More importantly, for the usual case of reactive elements as the inductors and capacitors, one finds that that certain mathematical or analytical representations (as the differentiation and integration operations) are hardly to implement in numerical tools because they are too sensitive to the unrealistic variations of electrical signals. Facing to this finding, the cohabitation of analog and numerical simulations can become complementary.

Then, we give more attention to the simulation of the diode because it plays the role of basic element constituting the GTO modeling. Meanwhile, the verification result regarding the diode model is a prerequisite condition before the approach to the GTO modeling. Finally, we treat the model of this latter prior to four phenomena: the switching power, the tail phenomenon responsible for the switching losses, the delay in the starting time, and the derivative operation effect.

The aim of this paper is to develop an analog model of high-voltage GTO suitable to predict accurately the dynamic characteristics of command circuits. The GTO is widely used in high power, high voltage of about 8 kV, and high current of about 4 kA for switching applications such as traction system of electric vehicles. The model presented in this paper is based on the diode switching behavior and described by the equivalent circuit of passive components such as capacitor and inductance. These elements, characterized by the input and output voltages, are simulated by using a traditional analog solver. The model includes the high switching capacity, tail current, the delayed-time response, and

As reported in [

By considering the schematic shown in Figure

Equivalent circuit of a realistic inductance.

It is well known that the current flowing through a capacitor

Equivalent circuit of a realistic capacitor.

The Laplace transform of (

Equivalent circuit of a capacitor.

Since certain power system parameters (supply voltage, load current, etc.) with high values cannot be implemented to the analog operators considered (e.g., maximum voltage of about 15 V), to pass this constraint, we propose in this article to use a scale factor constant. By denoting

For the sake of simplification, an ideal diode can be modeled by a classical switch. In order to simulate this type of switch element, an adequate function is needed. In addition, in order to respect the scale factors between the real and simulated quantities, it is necessary to have a negligible voltage drop when the diode is switched on. Hence, the diode model was chosen because it is characterized by spontaneous switching at low voltage drop usually around 0.7 V. However, when this simulated voltage drop is applied on the high-power circuit, it must be multiplied by a factor, for example,

Real diode model that minimize high voltage drop.

Diode

Simulated diode input—(a) and output—(b) voltages.

The analog model is based on the model used in the Success software developed in our laboratory. In this software, the power diode dynamic behavior is compared to the capacitive phenomenon due to the stored charges during the conduction caused by the high-diffusion capacitor and the space charge region which appears when the diode is turned off (low-depletion capacitance). As can be seen in Figure

The diode reverse recovery: it depends on diode physics (size) and components including the commutation circuit (resistor or inductance load).

The diode voltage rises: when the diode switches from conducting to nonconducting state; the space charge region increases and power loss are dissipated by commutation.

The overshoot voltage at switching on, this parameter is not taken into account in our model because the switching-off state is more important in power diode.

Success diode circuit model.

A complete power diode model is obtained by adding a diffusion capacitor model to the real diode model.

As highlighted in Figure

Complete power diode model.

By using the models proposed previously, the real value of the diffusion capacitor

With the considered analog diode model, the following mesh relations are obtained:

In this section, the validity of the analog model presented previously in Figure

The circuit introduced in Figure

Half wave rectifier circuit simulation.

The simulation results shown in Figure

Transient simulation of

One underlines here that a diode element is ideally blocked when the current becomes zero. But, in reality, the typical power diode continues to conduct the current inversely due to the diffusion capacitor. This effect is known as the reverse recovery phenomenon. This corresponds to the negative alternation of the wave represented by Figure

The buck circuit described in Figure

Buck converter circuit.

This circuit allows the calculation of the scale factor for the current and voltage, respectively, given by

Transient evolution of inductive load turnoff with two different inductance values obtained by using analog diode model.

In order to validate the power diode analog model, the obtained model results are compared with the numerical model ones which are depicted in Figure

Transient evolution of inductive load turnoff with two different inductance values obtained by using numerical diode model.

As illustrated in Figures

Many research efforts are dedicated to the new models for GTO devices, particularly those intended for circuit simulation [

Equivalent circuit of GTO [

An analog simulation of GTO is proposed in order to evaluate, in real time, the behavior of this component in its environment. First of all, we studied the principal static characteristics and the dynamic behavior of the GTO. Then, we carried out an identification of the model parameters and modeling of principle features for the dynamic behavior of GTO: dynamic capability of blocking, reverse tail current, delayed turn-off time, and

Complete numerical model of GTO [

Therefore, for the simplicity of simulation, the methodology uses an ideal model which does not include the effect of diffusion capacitor and avalanche breakdown.

We recall that the main features of turnoff of GTO are: the dynamic turn-off performances, the reverse tail current, the delayed turn-off, time and the time derivative voltage

Complete schematic of the under-study analog model of GTO.

It is interesting to recall the following basic electronic functions during the switch control:

It is obvious that when the controlled switch is not strong enough, the total blocking of the junction

Simulated GTO output voltage (a) when the control current is less than the switching capability and output current (b) when the control current is higher than the switching capability.

During its operation, the GTO is subjected to severe failures due to tail phenomenon. The presence of tail current causes losses in the GTO structure. The tail current is simulated by including in the model the diffusion capacitor of junction

Simulation of tail current for two loads and for diffusion capacitor with gain (a)

The analog model of diffusion capacitor junction

Effects of load current (a) and diffusion capacitor (b) on the delayed turn-off time.

During the turn-off state, the GTO does not exceed a maximum value of

The behavioral modeling method developed in this paper is based on the analog modeling of diode and GTO with three junctions. Theoretical approach illustrating the methodology of this electronic power component modeling was presented. It was evidenced toward simulations that the model proposed provides interesting performances in the term of characterization of transient phenomena eventually appearing due to the switching modes. It is noteworthy that the analog behavior enables also to predict certain behaviors which cannot be expressed with classical numerical models [