G. Tomasso

Position Measurement in Industrial Drives by Means of Low-Cost Resolver-to-Digital Converter

A fully integrated board for resolver-to-digital conversion is proposed in this paper. It is based on a combined analog/digital circuit, which allows one to track the shaft angle of a standard resolver in a digital form. Furthermore, the board also provides the feeding signal for the resolver-rotor circuit. All the tuning and configuration settings, which allow one to adapt different kind of resolvers to the proposed system, can be easily implemented directly on the board. The final assembly is a compact low-cost resolver-to-digital converter. The entire board design and implementation are described in this paper. In addition, several tests at different resolver speeds have been performed for validation.

A novel SVM strategy for VSI dead-time-effect reduction

A novel high-efficiency space vector modulation (SVM) strategy is proposed in this paper. It is based on the simultaneous and combined use of two strategies. The former consists of commutating only one switch of each inverter leg within each modulation period. In this way, there is no need to impose the dead time. The latter performs a step-by-step change of the modulation frequency in order to reduce the distortion of the inverter output voltage. The proposed system has been implemented and carried out on a programmable logic device (PLD) digital board. For validation, an experiment has been set up and several tests have been performed. The results have been compared with the ones achieved by means of the traditional SVM technique.

Predictive compensation of dead time effects in VSI feeding induction motors

A predictive algorithm is presented in the paper, which allows the compensation of the dead time effects in a voltage source inverter feeding an induction motor, with space vector PWM. It is based on the modification of the reference space vector of the feeding voltage according to a step-by-step analytical prediction of the stator phase currents. In this way the effects of the dead time can be taken into account and compensated. The validity and feasibility of the proposed algorithm are confirmed by simulation and proved by experimental implementation.

High performances supercapacitor recovery system for industrial drive applications

Recent developments in the field of supercapacitors make very promising the use of these equipments in a large range of applications. In particular, it is useful to introduce supercapacitors in all the drive applications, in which an energy recovery it is possible. In this paper, a predictive control of the supercapacitor storage system is proposed and tested in the field of the automatic warehouse. Experimental results show the increased performances of the systems thanks to supercapacitors energy recovery capability.

High Performance Digital Hysteresis Control for Single Source Cascaded Inverters

A digital modulation technique for cascaded inverters, which allows achieving high performance with low power losses, is proposed in this paper. It consists in a variable slope-fixed band current hysteresis control applied to a cascaded voltage source inverter structure, fed by a single dc source. The proposed technique can be used to supply ac motors, as well as generic ac loads. A considerable reduction of the switching losses is achieved, without increasing the total harmonic distortion on the load side. This result has been validated by means of a preliminary numeric analysis and confirmed by an experiment implementation.

A low cost resolver-to-digital converter

In this paper, the full implementation on a combined analog-digital board of the resolver-to-digital conversion is proposed. It represents a low cost solution for measuring the position by means of standard resolvers. Some experimental results are presented and a comparison with the performances achieved by means of an incremental encoder is performed.

Vectorial torque control: a novel approach to torque and flux control of induction motor drives

A general approach to torque and flux control of an induction motor fed by a voltage-source inverter is described in this paper. It is independent of whether rotor or stator flux is controlled. Based on this, an algorithm can be set up which allows the generation of the inverter switching patterns as a function of the reference values, both of the electromagnetic torque and of the controlled flux. Experimental comparisons with traditional direct torque control and field-oriented control techniques confirm the possibility of achieving very high dynamic performance with the proposed strategy.

Three-Phase Three-Level active NPC converters for high power systems

In last years the multilevel converter topologies have gained much attention both in the field of scientific research and in the one of high power applications. This paper proposes a comparative analysis between the classical structure of Neutral Point Clamped (NPC) converter and the emerging Active NPC converter. In particular, numerical analysis of losses distribution among power devices for some known carrier based PWM techniques are reported in the case of ANPC topology. Furthermore, experimental results concerning the design and the implementation of a Three-Phase Three-Level ANPC converter are analysed.

Direct torque and flux control of induction motor drives

A general approach to direct torque and flux control of an induction motor fed by a VSI is presented in the paper. The inverter switching patterns are generated as a function of the reference values of both the electromagnetic torque and of the controlled flux. In particular, the proposed control algorithm is independent of which kind of flux is controlled-rotor or stator. The results obtained by means of a real-time simulation show that the proposed control strategy allows very fast and accurate response of the drive.

Space Vector Modulation Algorithm for Power Losses and THD Reduction in VSI Based Drives

Abstract A novel modulation technique for optimizing the performances of voltage source inverter feeding induction motor drives is presented. It is based on a variable frequency modulation technique, changing step-by-step the switching frequency of the power modules in order to achieve a reduction both of the switching losses and of the output voltage distortion. In addition, this technique is combined with the “single switch commutation” one, which allows to reduce the blank time imposition during the switches commutations. The proposed modulation strategy has been implemented by means of a digital modulator and several tests have been performed in order to verify its validity and feasibility.