A. Raciti

Fuzzy adaptive vector control of induction motor drives

This paper deals with the design and experimental realization of a model reference adaptive control (MRAC) system for the speed control of indirect field-oriented (IFO) induction motor drives based on using fuzzy laws for the adaptive process and a neuro-fuzzy procedure to optimize the fuzzy rules. Variation of the rotor time constant is also accounted for by performing a fuzzy fusion of three simple compensation strategies. A performance comparison between the new controller and a conventional MRAC control scheme is carried out by extensive simulations confirming the superiority of the proposed fuzzy adaptive regulator. A prototype based on an induction motor drive has been assembled and used to practically verify the features of the proposed control strategy.

A robust adaptive controller for PM motor drives in robotic applications

The paper deals with theoretical development and practical implementation of an adaptive speed and position regulator suitable for robotic applications. The proposed adaptive control scheme is characterized by a reduced amount of computation and is based on the model reference adaptive control approach to compensate the variations of the system parameters, such as inertia and torque constant. A disturbance torque observer is employed to balance the required load torque and reduce the complexity of the adaptive algorithm. Simulation tests of a robotic drive, including an interior type permanent magnet synchronous (IPMS) motor, are reported in order to compare the proposed control scheme with standard speed and position regulators. Experimental results, obtained from a prototype based on a commercial PC board, are also reported in order to practically evaluate the feasibility and the features of the proposed adaptive control scheme. >

Sensorless vector and speed control of brushless motor drives

In the present paper an approach is presented to the speed control of permanent magnet synchronous motors without mechanical transducers. The rotor position, which is an essential component of any vector control scheme, is calculated through the instantaneous stator flux position and an estimated value of the load angle. A closed-loop state observer is implemented to compute the speed feedback signal. Experimental results on a laboratory tested motor drive are presented to validate the proposed procedure. >

Generalized PWM–VSI Control Algorithm Based on a Universal Duty-Cycle Expression: Theoretical Analysis, Simulation Results, and Experimental Validations

This paper presents a new approach in realizing various carrier-based pulsewidth-modulation techniques by a generalized control algorithm, which is referred to as the universal control algorithm and is obtained via unequal sharing of null states. The flexibility of such an approach allows one to easily and quickly control two-level inverters. Furthermore, this approach may be also extended with few changes to the control of multilevel inverters. The algorithm that is presented here for two-level voltage-source inverters (VSIs) also obtains efficient detection and management of both the linear and overmodulation ranges. In the overmodulation range, which is treated by using the alpha-beta components of the reference-voltage space vector, the algorithm shows the advantage of lower calculation time, thus allowing one, if required, to increase the switching frequency. Several simulation runs have been performed, aiming to test the proposed procedure for both two-level and multilevel VSIs. Finally, the new algorithm was experimentally validated in the case of two-level inverters by using it in a VSI workbench that can carry out several experimental tests

A new driving circuit for IGBT devices

IGBT devices are increasingly used in power electronic equipment due to their high power handling capability. This paper deals with the problems that concern the turn-on, turn-off, and short-circuit of these devices. An optimal new driving circuit is proposed which gives excellent device output performances. Experimental oscillogram traces of transient condition tests are given, which demonstrate the advantages of using the new driving circuit. The suitability of the driving circuit for integration is analyzed. >

Control of the switching transients of IGBT series strings by high-performance drive units

In the field of power electronics, the use of series-connected insulated gate devices, such as insulated gate bipolar transistors or power MOSFETs, is interesting in order to obtain fast and efficient power switches in medium-range power converters. In this kind of application, the control of the voltage sharing across the series strings of devices is an important aspect to be considered. The proposed technique allows obtaining safe commutations of the switches by simple and effective control circuits acting on the gate side of the power devices. In particular, the gate drive units are arranged in order to ensure good performance during the switching transients, while preventing overvoltage peaks on the devices. Both the design criteria and analysis of the control circuit are developed. Several experimental tests are reported in order to demonstrate the validity and correctness of the proposed approach.

Analysis of permanent magnet synchronous motors

A detailed representation of buried permanent magnet synchronous motors at steady state is presented. An equivalent circuit is proposed that accounts for the saliency of the machine and the particular influence of iron core losses on the machine operations. No-load as well as loaded conditions were analyzed and experimentally tested in order to describe the influence of the armature current on the rotor flux distribution. It is shown that several performances of permanent magnet motors can be predicted by the circuit.<<ETX>>

A logistical model for performance evaluations of hybrid generation systems

In order to evaluate fuel and energy savings, and to focus on the problems related to the exploitation of combined renewable and conventional energy resources, a logistical model for hybrid generation systems (HGSs) has been prepared. A software package written in ACSL, allowing easy handling of the models and data of the HGS components, is presented. A special feature of the proposed model is that an auxiliary fictitious source is introduced in order to obtain the power electric balance at the busbars during the simulation stage, as well as in the case of ill-sized components. The observed unbalanced powers are then used to update the system design. As a case of study, the simulation program is applied to evaluate the energetic performance of a power plant relative to a small isolated community, an island in the Mediterranean Sea, in order to establish the potential improvement achievable via an optimal integration of renewable energy sources in conventional plants. Evaluations and comparison among different sized wind, photovoltaic and diesel groups as well as of different management strategies have been performed using the simulation package and are reported and discussed aiming to present the track followed to select the final design.

Energy flows management in hybrid vehicles by fuzzy logic controller

Hybrid vehicles for public transportation seem to be a good solution to avoid air pollution and high level of noises in the city centres. The optimal management of energy flows concerned with such vehicles is a difficult task due to the complexity of the whole system including electrical, mechanical, and electrochemical components. In this paper a fuzzy logic based regulator is proposed to improve the efficiency of the vehicle. The system is simulated to demonstrate the validity and the convenience of a qualitative approach instead of a deterministic one. The simulation results confirm the feasibility and encourage more research towards an actual application.<<ETX>>

A Physics-Based Model for a SiC JFET Accounting for Electric-Field-Dependent Mobility

In this paper, a physical model for a SiC Junction Field Effect Transistor (JFET) is presented. The novel feature of the model is that the mobility dependence on both temperature and electric field is taken into account. This is particularly important for high-current power devices where the maximum conduction current is limited by drift velocity saturation in the channel. The model equations are described in detail, emphasizing the differences introduced by the field-dependent mobility model. The model is then implemented in Pspice. Both static and dynamic simulation results are given. The results are validated with experimental results under static conditions and under resistive and inductive switching conditions.