N. Rotondale

Torque and speed regulation of induction motors using the passivity theory approach

This paper deals with the passivity-based control of induction motors. This nonlinear control method is considered here mainly from the experimental point of view. Two different configurations have been considered: a current-regulated pulsewidth modulation inverter with hysteresis controllers and a space-vector-modulated voltage-source inverter. Experimental results show that both schemes give precise, fast, and robust torque and speed tracking in the full speed range. The first configuration is more attractive due to its better transient response and reduced complexity.

Supercapacitor to provide current step variation in FC PEM

The adoption of fuel cells for industrial applications, transportations and home power generation has widely increased during recent years. The performance evaluation of a fuel cell system requires both static and dynamic model, especially for the automotive applications which involve step variations of electric load. Besides, current step variations abruptly change the fuel cell voltage causing a non-linear behavior. In this case, a parallel supercapacitor becomes an important element to provide energy during transients. Fuel cell dynamic models presented in literature adopt chemical-physic-electrical parameters that are not usually provided by factories. In this paper, we concern the implementation of dynamic fuel cell model during step current transients from the electrical point of view. The model is used to evaluate the transient performance of the whole system, i.e. fuel cell and supercapacitor, by means of simulation software SIMULINK. Simulation results show gradual variations of fuel cell terminal voltage from initial steady state to final steady state values when a supercapacitor is parallel connected.

Minimum supercapacitor choice to provide current step variation in FC PEM

The adoption of fuel cells for industrial applications, transportations and home power generation has widely increased during recent years. The performance evaluation of a fuel cell system requires both static and dynamic model, especially for the automotive applications which involve step variations of electric load. Besides, current step variations abruptly change the fuel cell voltage causing a non-linear behavior (under-voltages). In this case, a parallel supercapacitor becomes an important element to provide energy during transients. Fuel cell dynamic models presented in literature adopt chemical-physic-electrical parameters that are not usually provided by factories. In this paper, we deal with the implementation of dynamic fuel cell model during step current transients from the electrical point of view [1]. The FC model is used to compute the minimum capacitance of the supercapacitor needed to obtain gradual variations of fuel cell terminal voltage from initial steady state to final steady state values.

The evaluation of the effects of the voltage amplitude modulations on induction motors

The voltage fluctuations of the electrical power supply can generate many undesirable effects on both industrial and domestic apparatuses. The aim of this paper is the evaluation of the effects of the low-frequency voltage amplitude modulation on induction motors. An experimental analysis has been applied to a three phase, 7.5 kW induction motor with the adoption of an ad hoc system for the EMC low-frequency immunity testing. The experimental results show that a few percent amplitude modulations can involve a critical behavior in terms of torque. As for the light flicker effect measurement, a statistical approach can be adopted for the evaluation of the torque fluctuation.

Analysis of PEM fuel cell – Supercapacitor – Battery pack system during standard cycle

Today the application of PEM (Polymer Electrolyte Membrane) fuel cell stack in the automotive field is a topic on central interest. Unfortunately, a PEM fuel cell stack cannot directly supply variable speed drives because of their non-linear behaviour in dynamic conditions. This paper is mostly concerned with the sizing of the supply system, PEM fuel cell-supercapacitor-battery pack, of an electric vehicle, based on the urban/suburban drive cycle NEDC (New European Driving Cycle). The average required power is used to design the fuel cell stack by imposing a preset operating point; the battery capacity is chosen in order to satisfy the constrain on the minimum value of the state of charge during the cycle; finally, the supercapacitor is determined by imposing the current sharing between battery and supercapacitor in transient condition.

Optimal modulation strategy for active front-end inverter feeding induction motors

Torque ripple in inverter fed induction motors is a critical problem if high switching frequency cannot be achieved because of the drive power rating or when switching losses must be kept low. In that case, the torque ripple minimisation should be one of the goals of the control strategies. The paper presents a PWM technique that can be used to minimise the steady state torque ripple of variable speed induction motor drives when high dynamic is not required, i.e. scalar control. The torque ripple is expressed as function of the DC bus voltage and of the notches introduced in the output voltage waveform of a VSI and it is minimised by finding out the optimum dc voltage value and modulation pattern. The control of the DC voltage does not increase the cost of the whole drive when a PWM AC/DC converter is already used to reduce the current harmonics and to improve the power factor. The proposed PWM strategy is compared with the space vector modulation and experimental results are reported and examined.

Indirect measurements for the on-line characterization of linear induction motors

This paper deals with the problem of tile characterization of linear induction motors (LIMs) and specifically with the on-line measurement of some quantities, such as thrust, current density in the sheet and air-gap flux. In this paper we propose a solution based on the indirect estimation of these quantities, starting from the measurement of the supply voltages. The proposed measurement system can be also advantageously adopted to solve the problem of the dynamical response of the transducers, such as those adopted for the measurement of the strain.<<ETX>>

Development issues of a Neural observer-based and fault-adaptive sensorless strategy for a multiphase BLDC motor

In this paper there will be presented basically two main subjects: the development procedure of a particular fault-adaptive multiphase sensorless strategy, based on Neural techniques, and the design issues involved by the fault-detection and isolation stages included in the proposed sensorless method. The proposed strategy is particularly suitable to be applied for the implementation of a cheap additional redundancy feature in order to augment the still existing fault-tolerant capabilities of some multiphase drives employed in safety-critical applications. In particular this unusual sensorless strategy is based on a back-EMF observer plus a proper set of coordinate transformations and possesses reconfiguration capabilities with respect to the occurrence of some certain classes of phase faults, gained through the use of a specific fault-adaptation mechanism. At first, the developmental steps of the fault-adaptive strategy will be described in detail after a preliminary motor modeling section, while, in a second step, the design issues linked with the fault-detection and remedial stages will be deeper investigated. Detailed simulation results will be shown at the end to validate the fault-adaptive properties of the proposed multiphase sensorless strategy.

System PEM fuel cell-supercapacitor: Analysis in transitory conditions

Today the application of PEM (Polymer Electrolyte Membrane) fuel cell stack in the automotive field is a topic on central interest. Unfortunately, a PEM fuel cell stack cannot directly supply variable speed drives because of their non-linear behaviour in dynamic conditions. This paper is mostly concerned with the performance evaluation of the PEM fuel cell - supercapacitor system during repetitions of current step variations; in those cases, the supercapacitors cannot be completely recharged before supplying the load in the next dynamic, and the fuel cell stack can be overloaded. We propose the introduction of lithium battery packs and of a DC/DC converter. The obtained results show that with the proposed configuration. That will be useful in the design of the control strategy of variable speed drives supplied by the proposed system.

The measurement of the RMS instantaneous power for the power distortion evaluation

The measurement of both electric power and energy, especially in non sinusoidal conditions, is today a still open research problem in the metrology community. Harmonic distortion, noise, transients, over-voltages and voltage dips have increased the difficulty in achieving accurate measurements. Besides, many of non-active power component definitions that have been proposed cannot be implemented in the traditional electro-mechanical or solid-state meters. This paper goes on to investigate about the possibility to process the instantaneous power signal when harmonics are likely to occur. The intent is not to resolve theoretical controversies, but instead to investigate about the possibility to easily process the instantaneous power signal in order to reduce the meter cost. Specifically, in the paper the measurement of a power parameter A*, which is sensible to the harmonic interferences with the fundamental component of the instantaneous power, is proposed. This parameter can be adopted for the development of a simplified single-phase electric energy meter able to operate in non sinusoidal conditions and to supply distortion information. Additionally, some simulation results are proposed, to confirm the applicability of the proposed measurement technique.