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Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Ingegneria "Enzo Ferrari"

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2023 - Numerical Robustness Evaluation of Floating-Point Closed-Loop Control Based on Interval Analysis [Articolo su rivista]
Savi, F; Farjudian, A; Buticchi, G; Barater, D; Franceschini, G

Power-electronics-based systems have penetrated into several critical sectors, such as the industry, power generation, energy transmission and distribution, and transportation. In this context, the system's control, often implemented in real-time processing units, has to meet stringent requirements in terms of safety and repeatability. Given the growing complexity of the implemented algorithms, floating-point arithmetic is being increasingly adopted for high-performance systems. This paper proposes to assess the numerical stability of the control algorithms by means of an interval analysis. The case study of an electric drive is considered, given the wide adoption of such systems and the importance they hold for the safety of the applications. In particular, two different control strategies-the resonant control and the vector space decomposition-are examined, and a sensitivity analysis based on the proposed technique highlights the different characteristics of the two with respect to numerical stability. The proposed method shows how the resonant control is more robust to variations of the controller gain coefficients with respect to the numerical stability, which could make it the preferred choice for mission-critical electric drive control.

2022 - femtoCore: An Open Source Processor Architecture for Power Electronics Controls [Relazione in Atti di Convegno]
Savi, F.; Barater, D.; Franceschini, G.; Buticchi, G.

2022 - FemtoCore enabled quasi-distributed Control for Modular Multilevel Converters [Relazione in Atti di Convegno]
Savi, F.; Barater, D.; Franceschini, G.; Buticchi, G.

The development of the processing capability has enabled the implementation of advanced control systems for power electronics converters. In this framework, the modular multilevel converter has attracted the attention of industry and academia, thanks to the good performance in terms of power quality, wide voltage capability, and fault tolerance, which are key requirement for high power applications. This paper proposes a quasi distribute control architecture based on a FemtoCore platform, an optimized soft-core designed for modular power electronics applications. Latency estimates and simulation results shows the potential of this solution for the control of modular multilevel converters.

2022 - Output Voltage Overshoot Suppression Control for Multilevel Inverter Architectures [Relazione in Atti di Convegno]
Bernardi, Fabio; Lorenzani, Emilio; Savi, Filippo; Nuzzo, Stefano; Barater, Davide

2021 - Evaluation of Inverter Architectures for Output Voltage Overshoot Reduction in WBG Electric Drives [Relazione in Atti di Convegno]
Savi, F.; Barater, D.; Nuzzo, S.; Franceschini, G.

The electrification of Non Road Mobile Machinery (NRMM) has brought to light several challenges for electrical actuation systems currently in use, above all their low power density. To hit the required targets, a strong increase of the performance, for both machines and drives, will be required. On the power electronic side, wide bandgap devices promise to enable much higher operating frequencies and temperatures, that can drastically cut down on the size of heatsinks and all magnetic components. However, their fast transition times produce an increased electric stress on the stator insulation system, which can experience partial discharges in some cases, thus quickly degrading. This paper strives to thoroughly compare several drive architectures that can mitigate this challenge, guiding the topology choice by analyzing power efficiency, ability to limit or eliminate overvoltages, reliability of the inverter structure and costs.

2021 - Femtocore: An Application Specific Processor for Vertically Integrated High Performance Real-Time Controls [Articolo su rivista]
Savi, F.; Harikumaran, J.; Barater, D.; Buticchi, G.; Gerada, C.; Wheeler, P.

In applications that require a high availability and high performance (for example aerospace),modular power electronics and multi-phase machines represent an advantageous choice. In this framework, a control system able to handle a high number of PWM signals and communication interfaces as well as featuring a high computational power is required. This paper proposes a novel HDL plus soft-core approach to be implemented on System-on-Chip hardware which allows for the efficient and modular implementation of the modern control techniques with strong guarantees in terms of determinism. The proposal lies in the adoption of a very simplified and optimized floating-point soft-core, the femtocore (fCore) and its tool-chain, which allows C-like implementation of complex algorithms in a HDL-design power electronics control framework. Several fCore units can be arranged for parallel processing to handle the time requirements of a complex modular system even with low sampling time (100 kHz or more). The proposed architecture is experimentally validated in a proof-of-concept, six-phase electric machine including a comparison against a traditional method.

2020 - High-Speed Electric Drives: A Step Towards System Design [Articolo su rivista]
Savi, Filippo; Barater, Davide; Nardo, Mauro Di; Degano, Michele; Gerada, Chris; Wheeler, Pat; Buticchi, Giampaolo

2020 - Minimization of network induced jitter impact on FPGA-based control systems for power electronics through forward error correction [Articolo su rivista]
Bianchi, V.; Savi, F.; De Munari, I.; Barater, D.; Buticchi, G.; Franceschini, G.

In modular distributed architectures, the adoption of a communication method that is at the same time robust and has a low and predictable latency is of utmost importance in order to support the required system dynamics. The aim of this paper is to evaluate the consequences of the random jitter on machine drives distributed control, caused by the messages’ re-transmission in case of an error in the received data. To achieve this goal, two different Forward Error Correction (FEC) techniques are introduced in the chosen protocol, so that the recipient of the message can correct random errors without the need of any additional round trip delays needed to request and obtain a re-transmission. Experimentally validated simulations are used to evaluate the impact of random network derived jitter on a real world closed loop control system for distributed power electronic converters.

2020 - Multiphase fault tolerant distributed control techniques for integrated drives based on resonant regulators [Relazione in Atti di Convegno]
Savi, F.; Barater, D.; Buticchi, G.; Wheeler, P.; Gerada, C.

One of the challenges brought forward by the gradual electrification undertaken by the aviation sector is the requirement of fault tolerance for machine drive systems to be used for critical on-board tasks such as propulsion or primary flight surface actuation. Their inherent advantages in both volumetric and gravimetric power density makes integrated drives the prime candidates for these applications. Despite the large advances in this field, few key area still need work. Key among which is fault tolerant current control strategies. This paper studies the application of resonant control techniques to achieve a scalable and fault tolerant current control strategy for multiphase machine.

2019 - Information technologies for distributed machine drives: An overview [Relazione in Atti di Convegno]
Savi, F.; Buticchi, G.; Gerada, C.; Wheeler, P.; Barater, D.

The exponential growth experienced by the semiconductor manufacturing field has led to a large proliferation of devices with large amounts computational power, enabling countless technologies and revolutionizing many fields. Control systems and machine drives are certainly among them. Much research is being carried out to develop multi-phase and fully segmented machines, with their inherent fault tolerance. To take full advantage of the redundancy and load sharing capabilities of the machine structure, with multiple winding sets, a suitable distributed control method must be used. A high performance network between the drives is thus required. This paper will present an overview of the available communication protocols that are used in the field and evaluate how suitable are they to this new class of very demanding real time tasks.

2017 - A system level comparison of drive topologies for high speed electrical machines [Relazione in Atti di Convegno]
Savi, Filippo; Barater, Davide; DI Nardo, Mauro; Degano, Michele; Gerada, Chris

This paper presents a comprehensive comparative study among five different converter topologies all designed to drive a 8.5kW-120krpm surface permanent magnet synchronous machine. The study aims at comparing the considered systems in terms of converter complexity, control complexity and overall efficiency. The assessment of the subsystems' efficiencies is based on a set of decoupled converter-electrical machine simulations. First the designed converters are simulated in Matlab-Simulink environment in order to estimate the converter losses and the current waveforms. Then the latter are used to supply the Finite Elements(FE) model of the electrical machine so to estimate all the loss components present in the real scenario. The results of the carried out study gives a wide understanding of the interaction between the two subsystems and some general design considerations needed to select the converter topology.