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EMILIO CARFAGNA

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Scienze e Metodi dell'Ingegneria
Docente a contratto
Dipartimento di Scienze e Metodi dell'Ingegneria

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Pubblicazioni

2023 - Active Thermal Control for Lifetime Equalization in CSI7-based Modular Photovoltaic Integration System [Relazione in Atti di Convegno]
Peng, Q.; Buticchi, G.; Migliazza, G.; Tan, N. M. L.; Guenter, S.; Carfagna, E.; Fidone, G. L.
abstract

2023 - Common Architectures and Devices for Current Source Inverter in Motor-Drive Applications: A Comprehensive Review [Articolo su rivista]
Fidone, G. L.; Migliazza, G.; Carfagna, E.; Benatti, D.; Immovilli, F.; Buticchi, G.; Lorenzani, E.
abstract

When compared to the much more common voltage-source inverter (VSI), the current-source inverter (CSI) is rarely used for variable speed drive applications, due to its disadvantages: the need of a constant DC-link current, typically realized with a front-end converter, and the need for reverse-voltage blocking (RVB) devices, typically implemented with in-series diodes. This limits the overall efficiency of the architecture. This paper investigates latest progress of the CSI research, with the aim of demonstrating why CSI could come back in the near future. Different architectures based on modern wide-bandgap (WBG) switches are analyzed, with an emphasis on why CSI can be advantageous compared to VSI.

2023 - Novel Single-Stage Current Source Inverter: Extension to Low-Speed Region in Motor Drive Applications [Articolo su rivista]
Benatti, D.; Migliazza, G.; Carfagna, E.; Immovilli, F.; Lorenzani, E.
abstract

In motor drive applications, single-stage current source inverters (CSIs) can manage only a limited speed range when the output voltage is greater than input voltage, due to the intrinsic boost capability. The classical solution adopted in low-speed region to control the input dc current, consists in the insertion of a prestage power converter. This article proposes a single-stage CSI that replaces the input inductance Ldc with coupled inductor. In this way, it is possible to add the needed time interval for the discharge of the magnetic energy of primary inductance Lm when the converter works in low-speed region or at standstill, extending the operating region of the converter. This solution allows to increase the efficiency of traditional CSIs for applications when the motor works most of the time in the high-speed region, thanks to the single-stage power conversion. Experimental and simulation results driving a permanent magnet synchronous machine are shown, confirming the validity of the proposed architecture.

2022 - A new Bernard–Praly-like observer for sensorless IPMSMs [Articolo su rivista]
Verrelli, C. M.; Carfagna, E.; Frigieri, M.; Crinto, A. S.; Lorenzani, E.
abstract

A slight extension of the global Bernard–Praly gradient adaptive observer – originally presented for nonsalient-pole surface Permanent Magnet Synchronous Motors (PMSMs) and recently proved to own local exponential convergence properties under well-known observability conditions – is here designed and proposed for Interior Permanent Magnet Synchronous Motors (IPMSMs) (with relatively small saliency) in the case in which the q-axis current is constant. It guarantees local exponential estimation – from stator current and voltage measurements – of both the stator fluxes and the sinusoidal/co-sinusoidal functions of the motor electrical angle, with no modification of the previous persistency of excitation condition requirements. Such an extension complements – at least locally – a previous analysis concerning IPMSMs under constant d-axis current. Applications to the sensorless control of IPMSMs (with realistic simulations) are included.

2022 - Optimized Parallel Hybrid Amplifier for Print-Head Piezoelectric Actuators with Trapezoidal Waveforms [Articolo su rivista]
Migliazza, G.; Carfagna, E.; Bernardi, F.; Lorenzani, E.
abstract

Most of the drivers used to control high-frequency print-head piezoelectric actuators are based on linear technology (e.g., Class AB amplifiers) which dissipate a large amount of power for this specific application. This choice is given by the necessary of very precise tracking and large bandwidth for the closed-loop voltage control of the piezoelectric load. This work highlights the critical issues of pure Class D amplifiers and hybrid (switching and linear) solutions. Then a new hybrid power amplifier topology is proposed analyzing its advantages and drawbacks for these kind of piezoelectric loads reducing energy consumption. First of all, the performance of the proposed solution is verified by simulations in LTspice environment. Experimental results showed the effectiveness of the proposed solution potentially paving the way to a larger adoption of this topology for high-frequency piezoelectric actuators. The proposed solution is patent pending.

2022 - Performance Analysis of Current Control Strategies for Hybrid Stepper Motors [Articolo su rivista]
Bernardi, F; Carfagna, E; Migliazza, G; Buticchi, G; Immovilli, F; Lorenzani, E
abstract

Hybrid stepper motors are widespread in industrial automation due to their robustness and high torque performance in low speed range, e.g. 3D printers, pick and place, and generally in many low power positioning applications. In order to increase the efficiency and dynamic performance, current/speed/position closed loop controls are implemented for high performance sensored stepper drives. The main challenge comes from the high number of magnetic poles which these motors feature, increasing the ratio between the fundamental and switching frequency. This paper critically evaluates four current control structures based field oriented control: classic PI regulators, sliding mode control, deadbeat predictive current control and model predictive current control. Simulations and experimental results aim to evaluate the dynamic performance, phase current amplitude and distortion in order to support the critical comparison.

2022 - Stator Flux Observer for the Sensorless Speed Control of Synchronous Machines with Uncertain Torque Constant [Relazione in Atti di Convegno]
Carfagna, E.; Migliazza, G.; Bernardi, F.; Verrelli, C. M.; Lorenzani, E.
abstract

In this paper, a recently designed adaptive stator flux observer (SFO), which provides estimates of rotor position and torque constant for surface mounted permanent magnet synchronous machines (PMSMs), is included in a speed sensorless control. Simulations and experimental results are carried out in order to evaluate the robustness of the whole control architecture with respect to uncertainties in the electrical parameters of the motor, as well as to the mismatch between the actual stator voltages imposed to the PMSM and the ones used for the observer, especially when low speeds are involved.

2021 - Assessment of master-slave and droop control strategies in multi-three-phase drives [Relazione in Atti di Convegno]
Benatti, D.; Alosa, C.; Carfagna, E.; Immovilli, F.; Lorenzani, E.
abstract

Multi-phase electric drives can be employed in a great variety of applications. Their advantage in terms of fault-tolerance capability is becoming the focus of the work of many research activities, especially in the field of transportation electrification. The main topic is to create redundant and modular multi-three-phase drives to increase the overall system reliability and fault-tolerance. To this aim, distributed control architectures have been assessed. In this paper, a centralized master-slave control is compared against a distributed droop control architecture, in order to identify advantages and drawbacks. Both of the control strategies are applied to a double three-phase drive. The aim of the work is to assess whether the droop control architecture can be a valid alternative to a centralized master-slave control in terms of performances, but with the additional benefit of having a proper full redundant fault-tolerant application.

2021 - DC Current Control for a Single-Stage Current Source Inverter in Motor Drive Application [Articolo su rivista]
Migliazza, G.; Buticchi, G.; Carfagna, E.; Lorenzani, E.; Madonna, V.; Giangrande, P.; Galea, M.
abstract

The current source inverter (CSI) is a power electronics topology that allows for the realization of variable speed drives (VSD). Compared to the most common voltage source inverter (VSI), which can be directly connected to a voltage source, the CSI needs a prestage to generate a constant current bus. This article therefore seeks to challenge this 'accepted' consideration that a CSI always needs this precircuit and seeks to remove this circuit by proposing an innovative $i_{dc}$ current control scheme. The proposed scheme is applied to a single stage motor drive driven by a CSI converter. It is shown how implementing this control scheme removes the need for the front-end stage, thus removing an unnecessary converter and optimizing the efficiency at the same time. The CSI state-space equations are presented and the developed models are verified using simulations. Stability analysis of small-signal model is considered through Nyquist criterion with the robustness in presence of variations of the most important system parameters. Experimental results driving a permanent magnet synchronous machine (PMSM) are shown confirming the validity of the proposed control, potentially paving the way to a larger adoption of the CSI topologies for motor drive applications.

2021 - Effect of semiconductor parasitic capacitances on ground leakage current in three-phase current source inverters [Articolo su rivista]
Migliazza, G.; Carfagna, E.; Buticchi, G.; Immovilli, F.; Lorenzani, E.
abstract

This paper investigates the influence of power semiconductor parasitic components on the ground leakage current in the three-phase Current Source Inverter topology, in the literature called H7 or CSI7. This topology allows reducing converter conduction losses with respect to the classic CSI, but at the same time makes the topology more susceptible to the parasitic capacitances of the semiconductors devices. In the present work, a grid-connected converter for photovoltaic power systems is considered as a case study, to investigate the equivalent circuit for ground leakage current. The same analysis can be extended to applications regarding electric drives, since the HF model of electric machines is characterized by stray capacitance between windings and the stator slots/motor frame. Simulation results proved the correctness of the proposed simplified common-mode circuit and highlighted the need of an additional common-mode inductor filter in case of resonance frequencies of the common-mode circuit close to harmonics of the power converter switching frequency. Experimental results are in agreement with the theoretical analysis.

2021 - Extended Speed Range Control for a Current Source Inverter Variable Speed Drive [Relazione in Atti di Convegno]
Migliazza, G.; Carfagna, E.; Buticchi, G.; Immovilli, F.; Lorenzani, E.
abstract

Voltage Source Inverters (VSIs) are usually adopted for high-speed motor drive applications due to the topology simplicity and the wide availability of control strategies for this topology. An alternative is the Current Source Inverter (CSI) which allows to achieve high speed range with limited DC voltage due to its intrinsic boost capability, and this is of interest in aerospace applications or electrical vehicles (EV), but a pre-stage is necessary to control the DC input current. In this work an hybrid solution is proposed to extend the speed range of a single stage CSI (i.e. CSI without pre-stage) driving a Permanent Magnet Synchronous Machine (PMSM). In fact using a single stage CSI with DC current control, the machine cannot work properly in low speed region, so the control is composed by two different strategies: one is proposed in this work for low speed operations and the other one is already known for high speed.

2021 - Iron Losses Impact on High-Speed Drives [Relazione in Atti di Convegno]
Carfagna, E.; Lorenzani, E.; Debbadi, K.; Pugliese, S.; Liserre, M.
abstract

Higher magnitudes of the stator currents, low efficiency, and degradation of the output torque in high speed machine are caused by iron losses, which are not sufficiently small to be neglected. A Finite Control Set Model Predictive Control (FCS-MPC) which takes iron losses into account in the prediction model on a high speed motor is proposed in this paper and compared to classical FCS-MPC that neglects iron losses influence. Performances of both models are analysed and compared under steady-state and transient conditions including acceleration condition using a 3-Level Hybrid Active Neutral Point Clamped (HANPC) inverter topology. Accurate simulations of a 3-Level HANPC inverter driving a high speed PMSM are presented comparing the proposed control respect to classical FCS-MPC and the classical Field Oriented Control (FOC) together with neutral point (NP) balance and loss minimization control (LMC).

2021 - PLL-Based Sensorless Control for Single-Stage Current Source Inverter in Motor Drive Application [Relazione in Atti di Convegno]
Carfagna, E.; Migliazza, G.; Buticchi, G.; Lorenzani, E.; Xu, Z.; Zou, Z.; Zhang, H.
abstract

The Current Source Inverters (CSIs) are an alternative to Voltage Source Inverters (VSIs) for electric motor applications. Despite the advantageous characteristics of intrinsic voltage boost capability, absence of electrolytic capacitors and reduced machine voltage stress, the increased component count and the need of a pre-stage for the inductor current control have limited the adoption. For some applications which have to operate always above a base speed (e.g. pumps, actuators, fans), single-stage CSI converter with improved efficiencies have been proposed. Owing to the advantage of the direct measurement of the terminal voltage, a simple and robust sensorless control is proposed for a single-stage CSI converter. Simulations on a SiC-based CSI7 converter driving a Permanent Magnet Synchronous Machine (PMSM) confirm the validity of the proposed control, potentially paving the way to a larger adoption of the CSI7 topology for motor drive application.

2020 - Ground Leakage Current in Three-Phase Current Source Inverters Depending on Power Semiconductors Parasitic Capacitances [Relazione in Atti di Convegno]
Migliazza, G.; Carfagna, E.; Bernardi, F.; Lorenzani, E.
abstract

This paper analyzes the relation between the ground leakage current and the power semiconductor parasitic components of a three-phase Current Source Inverter (CSI) topology named in literature H7 or CSI7. This topology is characterized by the presence of an additional switch which allows to reduce conduction power losses and decouple the DC side from the AC side during the application of the Zero current Vector to reduce ground leakage current. This work deals with the significant variation of this current depending on power converter parasitic capacitors. In this work the analysis is applied to grid-connected converters for a string photovoltaic applications, even if the behavior is the same also in case of electrical drives. The analysis is assessed by numerical simulations and experimental results with different parasitic capacitances that confirm also the validity of the proposed equivalent common-mode circuit.

2020 - PMSM-Model-Based Sensorless Control of Hybrid Stepper Motors: Performance and Robustness to Parameters Dispersion [Relazione in Atti di Convegno]
Carfagna, E.; Migliazza, G.; Immovilli, F.; Verrelli, C. M.; Lorenzani, E.
abstract

Extended Kalman Filters (EKFs), Phase Locked Loops (PLLs), and Stator Flux Observers (SFOs) are widely used for sensorless control of Permanent Magnet Synchronous Motors (PMSMs) drives. Their use (in their most advanced version) is here extended, on the basis of model analogies and suitably-guaranteed closed loop stability properties, to the sensorless speed regulation control of Hybrid Stepper Motors (HSMs), in which position and speed sensors are not employed to reduce costs and increase robustness with respect to high temperature and high-vibration environments. Both realistic simulations and experimental results demonstrate the feasibility of the proposed methods in terms of closed-loop performance and robustness to parameters mismatch.

2019 - Critical Aspects and Strategies for Sensorless Control of IPMSM based on Low-Frequency Voltage Injection [Relazione in Atti di Convegno]
Brugioni, R.; Carfagna, E.; Lorenzani, E.; Immovilli, F.
abstract

High-Frequency signal injection is widely adopted for zero and low-speed operating conditions in sensorless control of Interior Permanent Magnet Synchronous Motors (IPMSM) drives. However, the audible noise emissions caused by induced HF current has restricted in some cases its practical application. Low-frequency signal injection solve the noise problem, but it introduces new issues. In particular, the filtering for signal separation is not trivial and affects negatively the current control loop and the dynamic performance of the angle tracking estimator. To overcome these limitations, some new strategies and modifications respect to the traditonal sensorless control are proposed in this paper, using the esteem of specific signal components estimated from known information of the drive. The simulations were carried out considering a discrete-time controller and quantiziers on measured currents and pulsed voltages. The results demonstrated the feasibility of the proposed method.

2019 - Speed Sensor Fault Tolerant PMSM Machines: From Position-Sensorless to Sensorless Control [Articolo su rivista]
Verrelli, C. M.; Bifaretti, S.; Carfagna, E.; Lidozzi, A.; Solero, L.; Crescimbini, F.; Di Benedetto, M.
abstract

New sensorless observers (i.e., from stator currents/voltages measurements only), to be included into a simple observer-based sensorless control for the tracking of non-definitely zero speed references in nonsalient-pole surface permanent magnet synchronous machines (PMSMs), are proposed. They are obtained through a “minimum distance” modification from recently presented position-sensorless observers (i.e., from rotor speed and stator currents/voltages measurements only). The rotor speed estimate is here directly provided by the phase locked loop (PLL)-based third-order steady-state linear kalman filter (SSLKF) that has been previously used to mitigate the distortions on the estimated position. Experimental results illustrate the effectiveness of the proposed approach in a speed sensor fault-tolerant scenario.