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The study presents a significant development of an advanced control strategy for stand-alone three-phase induction generators. The system under study consists of a squirrel-cage induction generator driven mechanically by an internal combustion engine and electrically by a fault-tolerant converter coupled with a LC filter. As a novelty, in this study three low-cost electrical contactors are introduced in order to re-arrange the converter topology after a fault occurrence and a proper re-starting procedure is developed, allowing the converter to operate with only two legs. The control architecture is mainly described with respect to this last operating condition, evidencing its intrinsic robustness. The study focuses on the composite control of the converter and the prime mover in order to improve the dynamic assessment of the whole system. The converter control is designed around the sliding mode technique, due to its attractive performance, especially as far as parameter uncertainties are concerned. In order to validate the theoretical framework, this study presents the first ever made experimental tests of this system with reference to a generation unit of about 10 kVA. The results confirm the high capability of the proposed system in regulating voltage and frequency with very good dynamic features.

The aim of the paper is to present an optimized procedure for the preliminary sizing of permanent magnet motors used for the hybrid parallel propulsion of passengers aircrafts. The procedure is finalized to obtain high values of the motor power density and is carried out by means of a non-gradient approach with evolutionary algorithm integrated with magnetic and thermal finite element analyses. The target of the procedure is the achievement of a preliminary sizing of the motor suitable for the aircraft propulsion, starting from motors usually employed in other traction applications. Some numerical results are discussed in the paper with reference to significant case studies.

In the context of Battery Electric Vehicles, conventional Voltage Source Inverters (VSI) have been associated with several types of Battery Management System, mainly to balance the state of charge of electrochemical cells and extend their lifetime. Modular Multilevel Converters (MMC) with embedded elementary cells represent a valid alternative, thanks to the possibility of integrating the balancing functionality, ensuring a negligible harmonic content of the output currents and reducing the ringing phenomenon. On the other hand, the MMC topology exposes the cells to a different current waveform, increasing the cells losses in comparison with VSI solutions. This paper analyzes how the cells current waveforms of a MMC topology produce an unbalanced distribution of active power among the cells and evaluates their loss increase with respect to VSI configurations.

In the last years the aerospace industry has put a growing effort to develop on-board electrification. The difficulties, which have emerged to implement the transition to the future aircraft, concern above all the constraints to be respected for aircraft applications (reliability, small size, reduced maintenance time, etc.). The present paper proposes to analyze and discuss the power devices and suitable converter topologies that bring the requirements of the airborne applications, especially devoted to match with the reliability and performance issues.

The actual trends in the design of AC drives are directed to the reduction of the total weight, volume and cost. Usually, this implies the necessity to adopt new motor topologies and converter architectures. An important role is played by the mono-inverter dual parallel motor (MIDP), which gives the possibility to reduce the total weight and costs of power converters. This paper proposes a novel model predictive control algorithm in order to improve the transient performances of a MIDP used for an overhead carrier. The effectiveness of the proposal control is verified through some numerical simulations.

The increase of electrical drives power density and reliability allows the possibility to develop an all-electric propulsion systems for the aircraft. A configuration based on a mono-inverter dual-parallel (MIDP) permanent magnet synchronous motors could be suitable in order to reduce the cost and the weight of the propulsion systems. This paper proposes a novel current references limitation strategy to improve the overall dynamic behaviour of the system during transient operations, without the worsening of oscillations damping. The effectiveness of the proposed solution is demonstrated through numerical simulations.

Objective:This paper analyses the Modular Multilevel Converter (MMC) topology, where each individual Sub Module (SM), in half bridge configuration, is directly fed by an elementary electrochemical cell.Methods:The aim is to investigate how the reference voltages influence the cells currents waveforms, determining how the active powers and the losses are distributed among the cells. Considering a 2-level Voltage Source Inverter (VSI) topology working in the same conditions, the ratio between the MMC total cells losses and VSI total cells losses is calculated. After showing the system architecture and mathematical model, the cells current waveform investigation is presented and detailed both for triangular and sinusoidal voltage reference waveform.Results:Finally, the results are critically discussed with particular focus on the comparison between the MMC and the VSI topologies.

This paper presents an overview of the most recent state of the art in the field of high-speed electric machines fed through high-frequency converters. This type of systems is rapidly wide spreading in aeronautical and automotive applications, as well as microturbines. Each typology has its own advantages and downsides, which are analytically presented in this paper. Some types of high-speed electric machines require high-frequency voltage supply, highly stressing the dielectric materials of the winding insulation system. For this reason, in high-speed electric drives, premature failure may occur and a reduction of the total system reliability has been observed in the past years. Such issues are comprehensively investigated in this paper.

This paper proposes a simplified optimum control strategy for a monoinverter dual parallel (MIDP) permanent magnet synchronous motor (PMSM). With reference to the parallel PMSM unified model, two different auxiliary conditions are investigated. The first minimizes the supplied inverter current, and the second maximizes the motor's efficiency. Their formal expressions are derived by the introduction of three new normalized variables, linked to the load conditions. Thus, the optimum tracking considerations are general, and the parameters are independent. Simplified closed analytical forms are found for the optimum tracking, independently under steady-state and transient conditions. The selection of the best solution is then found via a parameter independent look-up table, and imposed through a closed-loop control diagram. The proposed control is compared to the present state of the art via experiments on a 1400-W MIDP PMSM test bench, showing an equivalent performance, with a lower computational burden.

This paper proposes a new mathematical model of modular multilevel converters for battery electric vehicles with space-vectors enabling a critical analysis of cell balancing for the battery management system. In particular, the requirements for power balancing and the actual number of degrees of freedom of the control are investigated. The paper shows that the traditional approach of cell balancing is a special case of the proposed control methodology. Numerical analyses with Matlab/Simulink™ highlight the reasons of the slow response of the standard balancing technique for specific operating conditions of the battery electric vehicle. The paper suggests potential improvements that could be introduced through the proposed generalised approach.

In the context of grid connected photovoitaic (PV) generation systems, there are two paramount aspects regarding the Maximum Power Point Tracking (MPPT) of the photovoltaic units and the continuity of the service. The most diffused MPPT algorithms are based on either perturb and observe, or on an incremental conductance approach and need both PV current and voltage measurements. Several topology reconfigurable converters are also associated with the PV plants, guaranteeing fault-tolerant features. The generation continuity can also be assured by interleaved inverters, which keep the system operating at reduced maximum power in case of failure. In this paper, an evolution of a hysteresis based MPPT algorithm is presented, based on the measurement of only one voltage, together with a novel space vector modulation suitable for a two-channel three-phase grid connected interleaved inverter. The proposed MMPT algorithm and modulation technique are tested by means of several numerical analyses on a PV generation system of about 200 kW maximum power. The results testify the validity of the proposed strategies, showing good performance, even during a fault occurrence and in the presence of deep shading conditions.

With reference to a strong variable parameters AC brushless machine, the paper deals with an online method of fault detection for closed loop controlled PMSM. The proposed technique exploits the monitoring of the motor d,q axes inductances via a Recursive Least Square Algorithm (RLS). The motor parameters, which have been pre-mapped with reference to the d,q axes current components, are compared to the results of the online identification procedure and their discrepancy is evaluated in real time. A fault indicator index is derived and its behavior conditioned in order to properly recognize any anomalous condition. The proposed method is tested via numerical simulations on the basis of a real PM brushless machine whose parameter have been evaluated in different operating conditions by means of several off-line experimental measurements.

The study deals with a novel torque derivative control of induction motor drives. The proposed technique is mainly finalised to improve the motor dynamic response regardless of speed operating conditions, ensuring satisfactory values of both motor currents distortion and torque ripple. The core of the discussed approach is a special look-up table, in which the converter voltage space vectors are sorted with respect to their influence on the torque derivative, taking also into account their influence on the flux magnitude. The table is indeed accessed by a desired torque derivative value, obtained by properly processing the output of hysteresis controllers. Moreover, a variable duty-cycle technique is implemented in order to ensure a satisfactory torque ripple in steady-state conditions. The proposed algorithm, suitable for a general multilevel inverter, is numerically tested on a three-level neutral point clamped inverter and its performance are compared with the ones obtained by a traditional direct torque control method based on three speed ranges look-up tables. The control is then validated experimentally by means of a reduced scale laboratory prototype fixing the same condition used for numerical analysis.