Portfolio

Documents: 25

Citations: 88

H-index: 6

Peer Reviews: 169

Journal Articles

Variable Switching Frequency PWM for Three-Phase Four-Wire Split-Capacitor Inverter Performance Enhancement

Riccardo Mandrioli, Aleksandr Viatkin, Manel Hammami, Mattia Ricco, and Gabriele Grandi.

IEEE Transactions on Power Electronics, vol. 36, no. 12, pp. 13674-13685, December 2021. 10.1109/TPEL.2021.3089610

Three-phase, four-wire, split-capacitor inverters, thanks to their capability to deal with unbalanced systems, are currently employed in photovoltaic installations, electric vehicles battery chargers, active power filters, and many other grid-tied applications. The minimization of ac output current ripple and switching losses positively impacts the inverter's efficiency, volume, weight, and cost optimization. For this reason, a novel variable switching frequency driving strategy independently tunable on each phase is proposed in this paper. Taking advantage of phase current ripple prediction, a proper variable switching frequency strategy is applied for obtaining a flat current ripple profile. Having tuned the driving strategy parameters, it is possible to optimize and compare individual metrics such as the maximum peak-to-peak value of the current ripple, current ripple rms, average switching frequency, and switching losses. By applying the proposed modulation method, a significant inverter performance enhancement has been obtained. Converter efficiency is improved without introducing detrimental effects on the current harmonic quality. Analytical derivations are expressed as a modulating index function and the power factor for balanced and unbalanced systems. All the theoretical developments are verified throughout numerical simulations and experimental tests.

The Role of Front-End AC-DC Converters in Hybrid AC/DC Smart Homes

Vítor Monteiro, Luís Fernando Corrêa Monteiro, Francesco Lo Franco, Riccardo Mandrioli, Mattia Ricco, Gabriele Grandi, and João Luiz Afonso.

MDPI Electronics, October 2021. Accepted

Electrical power grids are rapidly evolving into smart grids, with smart homes also making an important contribution to this. In fact, the well-known and emerging technologies of renewables, energy storage systems and electric mobility are each time more distributed throughout the power grid and included in smart homes. In such circumstances, since these technologies are natively operating in DC, it is predictable a revolution in the electrical grid craving a convergence to DC grids. Nevertheless, traditional loads natively operating in AC will continue to be used, highlighting the importance of hybrid AC/DC grids. Considering this new paradigm, this paper has as main innovation points the proposed control algorithms regarding the role of front-end AC DC converters in hybrid AC/DC smart homes, demonstrating their importance for providing unipolar or bipolar DC grids for interfacing native DC technologies, such as renewables and electric mobility, including concerns regarding the power quality from the smart grid point of view. Furthermore, the paper presents a clear description of the proposed control algorithms, aligned with distinct possibilities of complementary operation of front-end AC DC converters in the perspective of smart homes framed within smart grids, e.g., enabling to control smart homes in a coordinated way. The analysis and experimental results confirmed the suitability of the proposed innovative operation modes for hybrid AC/DC smart homes, based on two different AC DC converters in the experimental validation.

DC-link low-frequency current and voltage ripple analysis in multiphase VSIs with unbalanced load

Marija Vujacic, Obrad Dordevic, Riccardo Mandrioli, and Gabriele Grandi.

IET Electric Power Application, October 2021. Accepted | 10.1049/elp2.12153

Inverter’s performance and operating mode may be negatively affected by inverter input (dc-link) current and voltage ripple. It is a common experience that even theoretically balanced loads with perfectly balanced supply voltages, such as multiphase ac motors supplied by PWM inverters, in practice show a certain degree of current unbalance, in the range of a few percent, which introduces a low-frequency instantaneous power oscillation. This reflects in current and voltage low-frequency ripple on the dc-link inverter side (i.e., at the double-fundamental frequency). A possible method to analyze this matter is through the symmetric sequence components. In particular, based on the first negative current sequence component and by considering the equivalent dc-link impedance calculated at the dominant double-fundamental frequency, the amplitude of the corresponding dc-link voltage ripple component is calculated in this paper for a general multiphase load. Finally, the design of the dc-link capacitor in multiphase inverters is proposed considering requirements referred to the double-fundamental dc voltage ripple. The feasibility of proposed developments has been verified for three-, five- and seven-phase inverters by both numerical simulations and comprehensive experimental tests, always showing a good matching.

Electric Vehicles Charging Management System for Optimal Exploitation of Photovoltaic Energy Sources Considering Vehicle to Vehicle Mode

Francesco Lo Franco, Riccardo Mandrioli, Mattia Ricco, Vítor Monteiro, Luís Fernando Corrêa Monteiro, João Luiz Afonso, and Gabriele Grandi.

Frontiers in Energy Research, September 2021. Accepted | 10.3389/fenrg.2021.716389

The growing penetration of distributed renewable energy sources (RES) together with the increasing number of new electric vehicle (EV) model registrations are playing a significant role in zero-carbon energy communities' development. However, the ever-larger share of intermittent renewable power plants, combined with the high and non-modulable aggregate-EV charging demand requires an evolution towards new planning and management paradigms of energy districts. Thus, in this context, this paper proposes novel smart charging (SC) techniques that aim to integrate as much as possible RES generation and EV charging demand at the local level, synergically acting on power flows and avoiding detrimental effects on the electrical power system. To make this possible, a centralized charging management system (CMS) capable of individually modulating each charging power of plugged EVs is presented in this paper. The CMS aims to maximize the charging self-consumption from local RES, flattening the peak power required to the external grid. Moreover, the CMS guarantees an overall good state of charge (SOC) at departure time for all the vehicles without requiring additional energy from the grid even under low RES power availability conditions. Two methods that differ as a function of the EV power flow direction are proposed. The first SC only involves unidirectional power flow, while the second one also considers bi-directional power flow among vehicles, operating in vehicle-to-vehicle (V2V) mode. Finally, simulations are presented considering an actual case study validate the SC effects on a reference scenario consisting of an industrial area having a PV plant, non-modulable electrical loads, and EV charging stations. Results are collected and performance improvements by operating the different SC methods are compared and described in detail in this paper.

A Hybrid–Electric Driveline for Agricultural Tractors Based on an e-CVT Power-Split Transmission

Claudio Rossi, Davide Pontara, Carlo Falcomer, Marco Bertoldi, and Riccardo Mandrioli.

MDPI Energies, vol. 14, no. 21, p. 6912, October 2021. 10.3390/en14216912

The paper proposes a full hybrid driveline based on an electric Continuously Variable Trans-mission (e-CVT), inspired by the car industry’s most successful solution. The paper describes the operating principle, the system architecture and the control scheme of the proposed driveline. The analysis of four possible operating modes shows that the e-CVT driveline leads to performance similar to that of conventional tractors, as well as unusual features such as power boost, full-electric mode, optimized auxiliary drive and electric power delivery capability. The compact layout proposed for the e-CVT also makes it possible to simplify the overall layout of the tractor, in particular on the installation of both the thermal engine and the cooling system.

Procedure for Verifying Population Exposure Limits to the Magnetic Field from Double-Circuit Overhead Power Lines

Marco Landini, Giovanni Mazzanti, and Riccardo Mandrioli.

MDPI Electricity, vol. 2, no. 3, pp. 342-358, September 2021. 10.3390/electricity2030021

The verification of the limits of the population’s exposure to the magnetic field generated by double-circuit power lines from field measurements carried out on site is not trivial. It requires knowledge of the power line current instant values during the measurement period, the determination of the relationship between current and field at the measurement points (made more complex by the double-circuit overhead line configuration) and the use of that relationship to extrapolate the field values. Nevertheless, the verification of exposure limits for double-circuit power lines from on-site measurements is often conducted with rough, or not particularly stringent, procedures. A practical and straightforward procedure of general validity for non-optimized double-circuit lines is proposed here. No specific measurement position or conductors disposition knowledge is required as well as no complex three-dimensional finite element method code is necessary. The procedure, potentially also applicable to high- and extra-high-voltage lines, is validated on a medium-voltage (15 kV) double-circuit overhead power line study case. Exposure limits assessment suggests that if the line is operated at its rated capacity (230/285 A), the 3 μT quality target is missed. Results are provided with a 95% confidence interval ranging from ±100 nT to ±140 nT in all the cases.

Phase and Neutral Current Ripple Analysis in Three-Phase Four-Wire Split-Capacitor Grid Converter for EV Chargers

Riccardo Mandrioli, Manel Hammami, Aleksandr Viatkin, Riccardo Barbone, Davide Pontara, and Mattia Ricco.

MDPI Electronics, vol. 10, no. 9, 1016, April 2021. 10.3390/electronics10091016

The current switching ripple in a three-phase four-wire split-capacitor converter is analyzed in this paper for all the four ac output wires in relation to both balanced and unbalanced working conditions. Specifically, analytical formulations of the peak-to-peak and root mean square (RMS) current ripples are originally evaluated as a function of the modulation index, separately for the three phases and the neutral wire. Initially, the single-carrier sinusoidal pulse width modulation (PWM) technique is outlined, as it generally concerns a straightforward and effective modulation. With the aim of mitigating the current ripple in the neutral wire, the interleaved multiple-carrier PWM strategy is adopted, also avoiding any repercussion on the phase one. Numerical simulations and experimental tests were carried out to verify all the analytical developments.

Prediction of DC-link Voltage Switching Ripple in Three-Phase Four-Leg PWM Inverters

Riccardo Mandrioli, Aleksandr Viatkin, Manel Hammami, Mattia Ricco, and Gabriele Grandi.

MDPI Energies, vol. 14, no. 5, 1434, March 2021. 10.3390/en14051434

This paper presents a thorough prediction of DC-link voltage switching ripples in the three-phase four-leg inverters operating in balanced and unbalanced working conditions. The unbalanced modes examined here employ the highest degree of AC current imbalance while still preserving three-phase operation. This behavior can be found in many grid-connected or standalone grid-forming three-phase converters that supply “heavy” single-phase loads, comprising a recent trend in smart-grid, smart electric vehicle (EV)-charging applications. In this sense, for instance, the smart EV chargers might be employed in conditions when different power is drawn/injected from/to the grid, providing power conditioning services to the latter. The analysis of three-phase four-leg inverters is then extended to single-phase operations typical of home-charging or vehicle-to-home (V2H) applications. Their performances in terms of DC-link voltage switching ripple are demonstrated. Two of the most common carrier-based PWM modulation techniques are employed to drive the three-phase inverter—namely, sinusoidal PWM and centered PWM (carrier-based analogy of the space vector modulation). The derived mathematical expressions of peak-to-peak and RMS values of DC-link voltage switching ripple for balanced and unbalanced conditions are handy for designing the associated DC-link capacitor and estimating the overall efficiency of the converter. Extensive numerical simulations and experimental tests have been performed to validate the presented analytical developments.

AC Current Ripple in Three-Phase Four-Leg PWM Converters with Neutral Line Inductor

Aleksandr Viatkin, Riccardo Mandrioli, Manel Hammami, Mattia Ricco, and Gabriele Grandi.

MDPI Energies, vol. 14, no. 5, 1430, March 2021. 10.3390/en14051430

This paper presents a comprehensive study of peak-to-peak and root-mean-square (RMS) values of AC current ripples with balanced and unbalanced fundamental currents in a generic case of three-phase four-leg converters with uncoupled AC interface inductors present in all three phases and in neutral. The AC current ripple characteristics were determined for both phase and neutral currents, considering the sinusoidal pulse-width modulation (SPWM) method. The derived expressions are simple, effective, and ready for accurate AC current ripple calculations in three- or four-leg converters. This is particularly handy in the converter design process, since there is no need for heavy numerical simulations to determine an optimal set of design parameters, such as switching frequency and line inductances, based on the grid code or load restrictions in terms of AC current ripple. Particular attention has been paid to the performance comparison between the conventional three-phase three-leg converter and its four-leg counterpart, with distinct line inductance values in the neutral wire. In addition to that, a design example was performed to demonstrate the power of the derived equations. Numerical simulations and extensive experimental tests were thoroughly verified the analytical developments.

AC Current Ripple Harmonic Pollution in Three-Phase Four-Leg Active Front-End AC/DC Converter for On-Board EV Chargers

Aleksandr Viatkin, Riccardo Mandrioli, Manel Hammami, Mattia Ricco, and Gabriele Grandi.

MDPI Electronics, vol. 10, no. 2, 116, January 2021. 10.3390/electronics10020116

Three-phase four-leg voltage-source converters have been considered for some recent projects in smart grids and in the automotive industry, projects such as on-board electric vehicles (EVs) chargers, thanks to their built-in ability to handle unbalanced AC currents through the 4th wire (neutral). Although conventional carrier-based modulations (CBMs) and space vector modulations (SVMs) have been commonly applied and extensively studied for three-phase four-leg voltage-source converters, very little has been reported concerning their pollution impact on AC grid in terms of switching ripple currents. This paper introduces a thorough analytical derivation of peak-to-peak and RMS values of the AC current ripple under balanced and unbalanced working conditions, in the case of three-phase four-leg converters with uncoupled AC-link inductors. The proposed mathematical approach covers both phase and neutral currents. All analytical findings have been applied to two industry recognized CBM methods, namely sinusoidal pulse-width modulation (PWM) and centered PWM (equivalent to SVM). The derived equations are effective, simple, and ready-to-use for accurate AC current ripple calculations. At the same time, the proposed equations and diagrams can be successfully adopted to design the conversion system basing on the grid codes in terms of current ripple (or total harmonic distortion (THD)/total demand distortion (TDD)) restrictions, enabling the sizing of AC-link inductors and the determination of the proper switching frequency for the given operating conditions. The analytical developments have been thoroughly verified by numerical simulations in MATLAB/Simulink and by extensive experimental tests.

Analysis of Input Voltage Switching Ripple in Three-Phase Four-Wire Split Capacitor PWM Inverters

Manel Hammami, Riccardo Mandrioli, Aleksandr Viatkin, Mattia Ricco, and Gabriele Grandi.

MDPI Energies, vol. 13, no. 19, 5076, September 2020. 10.3390/en13195076

Three-phase, four-wire split capacitor inverters are currently employed in many applications, such as photovoltaic systems, battery chargers for electric vehicles, active power filters, and, in general, in all grid-tied applications that deal with possible grid voltage and/or current unbalances. This paper provides a comprehensive evaluation of the capacitor-switching voltage ripple and dc-link switching voltage ripple for the three-phase, four-wire, split capacitor inverters. Specifically, analytical formulations of the peak-to-peak and rms values of the voltage ripples are originally pointed out in this paper and determined in the case of balanced three-phase and unbalanced (two-phase and single-phase) output (ac) currents. The obtained results can help in designing the considered inverter and sizing of the dc-link capacitors. Reference is made to the sinusoidal PWM modulation and sinusoidal three-phase output currents with an almost unity power factor, representing a grid-connected application. Extensive numerical simulations have been carried out to thoroughly verify all the analytical developments presented in this paper. Furthermore, some experimental tests, having balanced output currents on the ac side, have been accomplished, validating numerical simulations and analytical developments.

Electric Vehicle Aggregate Power Flow Prediction and Smart Charging System for Distributed Renewable Energy Self-Consumption Optimization

Francesco Lo Franco, Mattia Ricco, Riccardo Mandrioli, and Gabriele Grandi.

MDPI Energies, vol. 13, no. 19, 5003, September 2020. 10.3390/en13195003

In the context of electric vehicle (EV) development and positive energy districts with the growing penetration of non-programmable sources, this paper provides a method to predict and manage the aggregate power flows of charging stations to optimize the self-consumption and load profiles. The prediction method analyzes each charging event belonging to the EV population, and it considers the main factors that influence a charging process, namely the EV’s characteristics, charging ratings, and driver behavior. EV’s characteristics and charging ratings are obtained from the EV model’s and charging stations’ specifications, respectively. The statistical analysis of driver behavior is performed to calculate the daily consumptions and the charging energy request. Then, a model to estimate the parking time of each vehicle is extrapolated from the real collected data of the arrival and departure times in parking lots. A case study was carried out to evaluate the proposed method. This consisted of an industrial area with renewable sources and electrical loads. The obtained results show how EV charging can negatively impact system power flows, causing load peaks and high energy demand. Therefore, a charging management system (CMS) able to operate in the smart charging mode was introduced. Finally, it was demonstrated that the proposed method provides better EV integration and improved performance.

A Comprehensive AC Current Ripple Analysis and Performance Enhancement via Discontinuous PWM in Three-Phase Four-Leg Grid-Connected Inverters

Riccardo Mandrioli, Aleksandr Viatkin, Manel Hammami, Mattia Ricco, and Gabriele Grandi.

MDPI Energies, vol. 13, no. 17, 4352, August 2020. 10.3390/en13174352

A complete analysis of the ac output current ripple in four-leg voltage source inverters considering multiple modulation schemes is provided. In detail, current ripple envelopes and peak-to-peak profiles have been determined in the whole fundamental period and a comprehensive method providing the current ripple rms has been achieved, all of them as a function of the modulation index. These characteristics have been determined for both phase and neutral currents, considering the most popular common-mode injection schemes. Particular attention has been paid to the performance of discontinuous pulse width modulation (DPWM) methods, including DPWMMAX and DPWMMIN, and their four most popular combinations DPWM0, DPWM1, DPWM2, and DPWM3. Furthermore, a comparison with a few continuous techniques (sinusoidal, centered pulse width modulations, and third harmonic injection) has been provided as well. Moreover, the average switching frequency and switching losses are analyzed, determining which PWM technique ensures minimum output current ripple within the linear modulation range at different assumptions. Numerical simulations and laboratory tests have been conducted to extensively verify all the analytical claims for all the considered PWM injections.

Selected as the cover article for MDPI Energies Issue 17, Volume 13, 2020 - link

Multileg Interleaved Buck Converter for EV Charging: Discrete-Time Model and Direct Control Design.

Stefania Cuoghi, Riccardo Mandrioli, Lorenzo Ntogramatzidis, and Gabriele Grandi.

MDPI Energies, vol. 13, no. 2, 466, January 2020. 10.3390/en13020466

This paper presents the modeling and the implementation of the digital control of a multileg interleaved DC-DC buck converter for electrical vehicle (EV) charging. Firstly, we derive a discrete averaged model of an n-leg interleaved buck converter (IBC). Secondly, we present a direct tuning procedure for one primary discrete PIDF (PID + filter) and multiple secondary PI controller. The objective of the control system is to regulate the current flow in each leg of the converter. This task is accomplished by introducing a novel control paradigm that simultaneously addresses two aims: on the one hand, the control scheme must guarantee an acceptable level of robustness under load variations; while on the other, an even distribution of power on each leg must be ensured at any operational condition. The proposed strategy hinges on a technique that combines simplicity and precision in the fulfillment of design frequency specifications. We use simulations and a digital signal processor (DSP) based experimental implementation of the design technique to validate the proposed methodology.

An Output Ripple-Free Fast Charger for Electric Vehicles Based on Grid-Tied Modular Three-Phase Interleaved Converters.

Klemen Drobnic, Gabriele Grandi, Manel Hammami, Riccardo Mandrioli, Mattia Ricco, Aleksandr Viatkin, and Marija Vujacic.

IEEE Transactions on Industry Applications, vol. 55, no. 6, pp. 6102-6114, November-December 2019. 10.1109/TIA.2019.2934082

An off-board dc fast battery charger for electric vehicles (EVs) with an original control strategy aimed to provide ripple-free output current in the typical EV batteries voltage range is presented in this article. The proposed configuration is based on modular three-phase interleaved converters and supplied by the low-voltage ac grid. The ac/dc interleaved three-phase active rectifier is composed of three standard two-level three-phase converter modules with a possibility to slightly adjust the dc-link voltage level in order to null the output current ripple. A modular interleaved dc/dc converter, formed by the same three-phase converter modules connected in parallel, is used as an interface between the dc link and the battery. The use of low-cost, standard and industry-recognized three-phase power modules for high-power fast EV charging stations enables the reduction of capital and maintenance costs of the charging facilities. The effect of coupling on the individual input/output inductors and total input/output current ripples has been investigated as well, considering both possible coupling implementations, i.e., inverse and direct coupling. Numerical simulations are reported to confirm the feasibility and the effectiveness of the whole EV fast charging configuration, including the proposed control strategy aimed to null the ripple of the output current. Experimental results are provided by a reduced scale prototype of the output stage to verify the ripple-free output current operation capability.

Capacitors Voltage Switching Ripple in Three-Phase Three-Level Neutral Point Clamped Inverters with Self-Balancing Carrier-Based Modulation.

Manel Hammami, Gabriele Rizzoli, Riccardo Mandrioli, and Gabriele Grandi.

MDPI Energies, vol. 11, no. 12, 3244, November 2018. 10.3390/en11123244

This paper provides a comprehensive analysis of the capacitors voltage switching ripple for three-phase three-level neutral point clamped (NPC) inverter topologies. The voltage ripple amplitudes of the two dc-link capacitors are theoretically estimated as a function of both amplitude and phase angle of output current and the inverter modulation index. In particular, peak-to-peak distribution and maximum amplitudes of the capacitor voltage switching ripple over the fundamental period are obtained. A comparison is made considering different carrier-based pulse-width modulations in the case of almost all sinusoidal load currents, representing either grid connection or passive load with a negligible current ripple. Based on the voltage switching ripple requirements of capacitors, a simple and effective original equation for a preliminary sizing of the capacitors has been proposed. Numerical simulations and experimental tests have been carried out in order to verify the analytical developments.

Conference Papers

State of Charge Optimization-based Smart Charging of Aggregate Electric Vehicles from Distributed Renewable Energy Sources.

Francesco Lo Franco, Mattia Ricco, Riccardo Mandrioli, and Gabriele Grandi.

IEEE International Conference on Compatibility, Power Electronics and Power Engineering, IEEE CPE-POWERENG 2021, Florence (IT), 14-16 July 2021. 10.1109/CPE-POWERENG50821.2021.9501214

In the context of electric vehicles integration in energy districts with the growing penetration of renewable energy sources (RES), this paper provides a method to manage the aggregate charging power flows optimizing self-consumption for flattening the load curve, and optimally exploit the intermittent RES. Under low internal RES availability, the proposed smart charging algorithm aims to guarantee an overall good state of charge of vehicles at the departure instant. This is achieved through a charging management system that differently allocates the power among the electric vehicles based on their battery charging level without involving absorption from the external grid. A reference scenario based on a real case study is performed to evaluate the proposal. This consists of an industrial area with photovoltaic plants and electrical loads. Finally, improvement in smart charging performance, especially under medium-low irradiance availability, is shown.

Modular Multilevel Converters Based on Interleaved Half-Bridge Submodules.

Aleksandr Viatkin, Mattia Ricco, Riccardo Mandrioli, Tamás Kerekes, Remus Teodorescu, and Gabriele Grandi.

IEEE International Conference on Industrial Technology, IEEE ICIT, Valencia (ES), pp. 440-445, 10-12 March 2021. 10.1109/ICIT46573.2021.9453643

This paper reports a novel modular multilevel converter with interleaved sub-modules (ISM-MMC). The ISMMMC exhibit a higher scalability in current rating then conventional MMC structures with parallel devices. It can employ low-cost, low-current power switches rather than their bulky and expensive counterparts normally designed in classical MMCs. Another remarkable feature is that the number of the output voltage levels is synthetically multiplied by the number of interleaved SMs. The ISM-MMC is capable of bringing the known advantages of MMC to low voltage – high power applications making it a good candidate for the sector of ultrafast chargers for electrical vehicles where typical power rating in excess of 1 MW is required for the low voltage supply. A proper modulation scheme is implemented and explained in this paper. A comparison with a classical MMC topology is also provided in terms of number of voltage levels, output voltage harmonic content, and number of components by fixing the number of SMs. Simulation results are given to demonstrate the feasibility of the proposed topology and the implemented modulation scheme. Despite this paper is dealing with a singlephase configuration, the extension to a three-phase scheme can be obtained in a straightforward manner.

A Ripple-Free Output Current Interleaved DC/DC Converter Design Algorithm for EV Charging.

Riccardo Mandrioli, Mattia Ricco, Manel Hammami, Aleksandr Viatkin, and Gabriele Grandi.

IEEE International Conference on Industrial Technology, IEEE ICIT, Valencia (ES), pp. 292-297, 10-12 March 2021. 10.1109/ICIT46573.2021.9453554

In this paper, a ripple-free output current interleaved DC/DC converter has been analyzed for Electric vehicle charging stations. Firstly, a ripple-free control strategy able to ensure a theoretically flat output current profile and input voltage ripple minimization at any working conditions is discussed. This strategy drives the active front-end to regulate the DC-link voltage and, at the same time, the interleaved back-end converter to operate in zero ripple working points. Secondarily, a generalized designing algorithm able to consider constraints like AC grid voltage and battery voltage is proposed. Finally, simulations support ripple mitigation capabilities in steady-state and transient conditions for a 12-leg scheme.

Ripple Correlation Control MPPT scheme applied to a Three-phase Flying Capacitor PV System.

Mattia Ricco, Manel Hammami, Riccardo Mandrioli, and Gabriele Grandi.

Zamboni W., Petrone G. (eds) ELECTRIMACS 2019. Lecture Notes in Electrical Engineering, vol 697. Springer, Cham, 2020. 10.1007/978-3-030-56970-9_2

This chapter introduces a ripple correlation control (RCC) algorithm for tracking the maximum power point (MPP) for a flying capacitor three-level three-phase photovoltaic (PV) system. Although RCC maximum power point tracking (MPPT) method has been widely used on single-phase plants, a three-phase implementation based on sinusoidal carrier PWM has not been presented yet. The inherent oscillations of the PV current and voltage are employed as a perturbation for the RCC MPPT system. The proposed algorithm adopts the PV current and voltage 3rd harmonic component for estimating the power (or current) derivative, dPpv/dVpv (or dIpv/dVpv). Firstly, referring to the carrier-based sinusoidal pulse width modulation (SPWM), the flying capacitor inverter modulation scheme is presented. Secondly, the proposed RCC MPPT method is introduced. Finally, multiple MATLAB-/Simulink-based simulations of the RCC MPPT algorithm acting on a grid-connected PV system are provided. Both steady-state and dynamic (irradiance increase and decrease) conditions present good performances.

Evaluation of AC Current Ripple in case of Split-Capacitor Three-Phase Four Wires Inverters.

Manel Hammami, Mattia Ricco, Aleksandr Viatkin, Riccardo Mandrioli, and Gabriele Grandi.

IEEE International Energy Conference, IEEE ENERGYCON, Gammarth (TN), pp. 128-132, 28 September-1 October 2020. 10.1109/ENERGYCon48941.2020.9236477

This paper deals with a split capacitor three phase four-wire inverter, able to deal with unbalanced ac currents and/or voltages. The considered topology can be used in many applications such as photovoltaic systems, chargers for electrical vehicles, active filters, and in general all the grid-connected applications. One parameter that must be considered in the converter design is the ac (output) current ripple, which should be determined and minimized in order to improve the system efficiency. In this paper, the evaluation of the ac current ripple for the three-phase split-capacitor inverter is developed with reference to both balanced and unbalanced output conditions. In particular, the peak-to-peak and the rms current ripple are analytically determined as a function of the modulation index, for each phase. Initially, reference is made to single carrier sinusoidal PWM, being, in general, a simple and effective solution. The interleaved multiple-carrier PWM strategy is then considered in order to mitigate the current ripple in the neutral wire, while not affecting its phase counterpart. Numerical simulations have been carried out in order to verify the analytical developments.

Awarded as the Best Paper in the 6th edition of IEEE ENERGYCON - link

Current Pulse Generation Methods for Li-ion Battery Chargers.

Francesco Lo Franco, Mattia Ricco, Riccardo Mandrioli, Aleksandr Viatkin, and Gabriele Grandi.

IEEE International Conference on Industrial Electronics for Sustainable Energy Systems, IEEE IESES 2020, Cagliari (IT), pp. 339-344, 1-3 September 2020. 10.1109/IESES45645.2020.9210664

Lithium-Ion batteries are playing an essential role in electric vehicles and renewable sources development. In order to reduce the charging time, high power chargers are necessary. However, lithium-ion chemistry limits the maximum current and charging speed. The diffusion rate of lithium ions into the electrodes determines the rate of charging. The slow lithium diffusion, especially experienced after high current rates, inevitably results in concentration polarization. The increase of the concentration polarization, in addition to the growth of the charging time, may lead to a faster battery deterioration. To deal with this obstacle, the Pulse Charging (PC) protocol has been proposed. There is no common opinion about the benefits given by the PC to the battery charging process in comparison with the conventional constant-current, constant-voltage (CCCV) protocol. Nevertheless, the purpose of this work is to provide an overview of possible methods that can be used to generate current pulses, without focusing on its advantages. Different techniques with the corresponding control algorithms have been implemented and analyzed through simulations in MATLAB/Simulink environment.

Theoretical Analysis of the AC Current Ripple in Three-Phase Four-Leg Sinusoidal PWM Inverters.

Aleksandr Viatkin, Riccardo Mandrioli, Manel Hammami, Mattia Ricco, and Gabriele Grandi.

IEEE International Symposium on Industrial Electronics, IEEE ISIE, Delft (NL), pp. 758-763, 17-19 June 2020.

Three-phase four-leg voltage-source inverters (VSIs) are currently considered for several renewable-energy and automotive applications, due to their inherent ability to deal with unbalanced ac currents through the 4th wire (neutral). Although conventional carrier-based and space vector modulations have been commonly applied and extensively studied for various power electronic configurations, very little has been reported concerning the impact of these modulation strategies on ac current switching ripple for three-phase four-leg VSIs. This paper presents a comprehensive analytical derivation of peak-to-peak profile and rms value of the ac current ripple for this converter topology in case of sinusoidal pulse-width modulation, also including the neutral wire. The analytical developments for all examined subcases have been verified by numerical simulations, carried out in the MATLAB/Simulink environment. 10.1109/ISIE45063.2020.9152511

Capacitor Voltage Switching Ripple in Three-Phase Three-Level Neutral Point Clamped Inverters with Sinusoidal Carrier-Based PWM.

Manel Hammami, Riccardo Mandrioli, and Gabriele Grandi.

IEEE International Symposium on Industrial Electronics, IEEE INDEL, Banja Luka (BH), pp. 1-6, 1-3 November 2018. 10.1109/INDEL.2018.8637643

This paper provides an extensive theoretical analysis of the capacitors voltage ripple for three-phase three-level neutral point clamped inverter topologies. The capacitor voltage ripple amplitudes are theoretically estimated as a function of both amplitude and phase angle of output current, and the modulation index. Each capacitor voltage basically consists of switching frequency and the third harmonic components, thereby both components are considered in the analysis. In particular, peak-to-peak distribution and maximum amplitudes of the capacitor voltage switching ripple over the fundamental period are obtained. As a first simplified approach, reference is made to sinusoidal carrier-based PWM with sinusoidal load currents, representing either grid connection or passive load with a negligible current ripple. Based on the ripple requirements of capacitors voltage, a simple and effective original equation for designing capacitors has been proposed. Numerical simulations have been carried out by Mat-lab/Simulink in order to verify the analytical developments.

A Ripple-Free DC Output Current Fast Charger for Electric Vehicles Based on Grid-Tied Modular Three-Phase Interleaved Converters.

Klemen Drobnic, Gabriele Grandi, Manel Hammami, Riccardo Mandrioli, Aleksandr Viatkin, and Marija Vujacic.

IEEE International Symposium on Industrial Electronics, IEEE INDEL, Banja Luka (BH), pp. 1-7, 1-3 November 2018. 10.1109/INDEL.2018.8637627

This paper presents an off-board DC fast battery charger for electric vehicles (EVs) based on modular three-phase interleaved converters supplied by the low-voltage AC grid. The charger rectifies the grid voltage to a common DC-bus voltage having a slightly adjustable level by means of AC/DC interleaved three-phase active rectifier, composed of three standard commercial two-level three-phase converter modules. Three identical three-phase modules connected in parallel form a modular interleaved DC/DC converter to supply the battery. This structure offers a use of low-cost, unified and industry-recognized three-phase power modules for high- power fast EV charging stations that will reduce capital and maintenance costs of the charging facilities, enhancing further expansion of the eco-friendly transport. An original control strategy has been proposed to provide ripple-free output current in the typical EV batteries voltage range. The effect of coupling on the individual input/output inductors and total input/output current ripples has been investigated, considering both possible coupling implementations, i.e. inverse and direct coupling. Simulation results, carried out in MATLAB/Simulink environment, are reported in to confirm the feasibility and the effectiveness of the proposed EV fast charging configuration.

Preprint Paper

Current Balancing Control for Interleaved Half-Bridge Submodules in Modular Multilevel Converters.

Aleksandr Viatkin, Mattia Ricco, Riccardo Mandrioli, Tamás Kerekes, Remus Teodorescu, and Gabriele Grandi.

TechRxiv Preprint. September 2021. 10.36227/techrxiv.16645861

This paper presents a closed-loop current balancing control for Modular Multilevel Converters with Interleaved half-bridge Sub-Modules (ISM-MMC). The new control loop solves the well-known problem of proper current balancing among interleaved half-bridge legs in each ISM-MMC submodule while preserving a simple and reliable structure. In addition to that, a novel capacitor voltage balancing strategy for MMCs is developed. The new algorithm contains main advantages of the classical capacitor voltage balancing methods while provides an opportunity to decouple two balancing tasks of ISM-MMC, namely capacitor voltage and interleaved legs current balancing. The proposed control methods feature good dynamic performance and are compliant with a digital processor's operational constraints. The effectiveness of the new balancing methods was verified during extensive numerical simulations and experimental tests on a laboratory prototype by the corresponding system response under the input/output characteristics variation and interleaved current control perturbation.

A Novel Modular Multilevel Converter Based on Interleaved Half-Bridge Submodules.

Aleksandr Viatkin, Mattia Ricco, Riccardo Mandrioli, Tamás Kerekes, Remus Teodorescu, and Gabriele Grandi.

TechRxiv Preprint. July 2021. 10.36227/techrxiv.15022920

A new Modular Multilevel Converter with Interleaved half-bridge Sub-Modules (ISM-MMC) is proposed in this paper. The ISM-MMC exhibits a higher modularity and scalability in terms of current ratings with respect to a conventional MMC, while preserves the typical voltage level adaptiveness. The ISM-MMC brings the known advantages of classical MMC to low-voltage, high-current applications making it a novel candidate for the sector of ultra-fast chargers for all types of electrical vehicles (EV). This advanced topology makes it possible to easily reach charging power of the EV charging system up to 4.5 MW and beyond with low-voltage supply. To operate the new converter, a hybrid modulation scheme that helps to exploit advantages of the interleaving scheme, is implemented, and explained in this paper. It has been verified that the typical MMC control methods are still applicable for ISM-MMC. A comparative study between classical MMC and ISM-MMC configurations in terms of output characteristics and efficiency is also given. Furthermore, it has been demonstrated that the number of ac voltage levels is synthetically multiplied by the number of interleaved half-bridge legs in submodules. Numerical simulations and Hardware-in-the-Loop tests are carried out to demonstrate the feasibility of the proposed topology and implemented modulation scheme.

Award

IEEE ENERGYCON 2020 - Best Paper Award

Journal Cover

Energies, Volume 13, Issue 17 (September-1 2020)

Dissertations

Master Dissertation

A Modular Interleaved Converter for Output Current Ripple Minimization in DC Fast Chargers for Electric Vehicles

Supervisor: prof. Gabriele Grandi. Co-supervisors: Dr. Mattia Ricco, Dr. Manel Hammami, and Dr. Stefania Cuoghi.

University of Bologna, October 2019.

Bachelor Dissertation

Studio e realizzazione di un dispositivo per la determinazione dinamica delle caratteristiche I-V e P-V di moduli fotovoltaici.

Relatore: prof. Gabriele Grandi. Correlatori: Dr. Manel Hammami e Ing. Marco Landini.

Università di Bologna, Luglio 2017.

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