Authors

Control loops design in a grid supporting mode inverter connected to a microgrid

Giovanni M. Foglia, Luisa Frosio, Matteo F. Iacchetti, Roberto Perini

2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe) // 8-10 September 2015

This paper deals with some design aspects of the control loops in a droop-controlled VSI connected to other inverters of greater ratings or to a strong grid, which sets the frequency. The design of a damping resistor in series with the AC filter capacitor is discussed and the impact of strong feedback between the output current and the capacitor voltage is investigated. Moreover, an analysis of the derivative droop coefficients is carried out through a simplified equivalent circuit.

Technical Strategies for Voltage Power Regulation in LV Distribution Networks

M. Delfanti, L. Frosio, G. Monfredini, M. Merlo, C. Rosati, D. Rosati, G. Marchegiani

Distributed Generation and Alternative Energy Journal, vol. 30, no.4, pp. 7-14 // 1 January 2015

We report the integration of a novel voltage regulation strategy in the inverter control algorithm for Dispersed Generation (DG) applications. The adoption of a decentralized voltage control based on local curves allows the voltage profile to be controlled at the Point of Common Coupling (PCC) of the generators and, therefore, the capacity of existing distribution networks to host more generation from renewables. The work is focused on a low voltage distribution network and both the reactive power modulation and the real power curtailment are considered in the proposed local strategy. Both numerical and experimental analysis are necessary in order to test and validate the proposed voltage control strategy. Firstly, the performances of the proposed control are tested by a numeral analysis and the impact on both the electrical system and the inverter apparatus is evaluated. Secondly, the benefit of the control strategy is analysed by experimental analysis in a test facility to verify the feasibility of voltage regulation in a real feeder.

Harmonic Analysis of Output Filters for Grid Connected Converters in Battery Energy Storage Systems

Alberto Dolara, Giulia Magistrati, Riccardo Zich, Luisa Frosio and Gabriele Marchegiani

16th International Conference on Harmonics and Quality of Power (ICHQP) // 25-28 May 2014

Battery Energy Storage Systems, as well as many distributed generation systems, use voltage source inverter as interface with the grid. These converters require a filtering section to reduce current harmonics injected to the grid. Usually, harmonic filter is a series inductance connected between grid and inverter. Higher order filters can provide better harmonic attenuation at lower switching frequency and reduce filter size, with potential benefits for high power applications. This paper deals with the sizing and the frequency response of three different harmonic filters suitable to reduce the ripple in the grid current waveform. Dynamic simulations of a 100 kW Battery Energy Storage System highlight the better performance of high order filters.

Dispersed generation to provide ancillary services: AlpStore project

M. Delfanti, L. Frosio, M. Merlo, G. Monfredini, L. Pandolfi, C. Rosati, D. Rosati,

International Conference on Clean Electrical Power (ICCEP), pp. 133-138 // 29 August 2013

In the future, electrical systems should be able to integrate all users at the same time and guarantee power quality, stability and safety over time. The integration of renewable energy sources leads to new issues involving the intermittence of this generation typology. A high penetration of intermittent power plants will reduce the capability of the system to overcome critical events (e.g. frequency oscillations and voltage profile perturbation). This work presents new regulation schemes/functions developed in the AlpStore project framework, devoted to managing dispersed generation in order to provide ancillary services to the main grid. The work developed can be split into two main items: reactive injection regulation and frequency control regulation. The first regulation is devoted to increasing the Hosting Capacity of the distribution grid (i.e. it results to be a local control), whereas the latter aims to guarantee the energy balance of the national electric grid (i.e. it could be classified as a grid control).

Parallel-connected photovoltaic inverters: Zero frequency sequence harmonic analysis and solution

M. S. Carmeli, M. Mauri, L. Frosio, A. Bezzolato, G. Marchegiani

International Journal of Emerging Electric Power Systems, vol. 14, no. 2, pp. 199-2016 // 30 May 2013

High-power photovoltaic (PV) plants are usually constituted of the connection of different PV subfields, each of them with its interface transformer. Different solutions have been studied to improve the efficiency of the whole generation system. In particular, transformerless configurations are the more attractive one from efficiency and costs point of view. This paper focuses on transformerless PV configurations characterised by the parallel connection of interface inverters. The problem of zero sequence current due to both the parallel connection and the presence of undesirable parasitic earth capacitances is considered and a solution, which consists of the synchronisation of pulse-width modulation triangular carrier, is proposed and theoretically analysed. The theoretical analysis has been validated through simulation and experimental results.

Centrali ibride, tecniche di controllo per la gestione di micro reti intelligenti

L. Frosio, C. Rosati, G. Marchegiani, I. Mazzucco

Automazione e Strumentazione, 84-88.pdf // April 2013

Le centrali ibride, elemento chiave per poter realizzare e controllare le microreti ad alta penetrazione di Fonti Energetiche Rinnovabili, richiedono tecniche di controllo specifiche. In questo articolo si presenta una panoramica sulle varie modalitĂ  di controllo degli inverter di interfaccia delle centrali ibride e sulle diverse architetture di microrete che si possono realizzare. Si presentano inoltre alcuni risultati sperimentali ottenuti su una microrete a potenza ridotta sulla quale sono state implementate diverse strategie di controllo.

Reduction of high frequency zero sequence harmonics in parallel connected PV-inverters

A. Bezzolato, M. S. Carmeli, L. Frosio, G. Marchegiani, M. Mauri

Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011) // 15 September 2011

High power photovoltaic plants are usually constituted of the connection of different photovoltaic subfields, each of them with its interface transformer. Different solutions have been studied to improve the efficiency of the whole generation system. In particular, transformerless configurations are the more attractive one from efficiency and costs point of view. This paper focuses on transformerless photovoltaic configurations characaterised by the parallel connection of interface inverters. The problem of zero sequence current due to both the parallel connection and to the presence of undesirable parasitic earth capacitances is considered and a solution, which consists on the synchronisation of PWM triangular carrier is proposed and theoretically analysed. The theoretical analysis has been validated through simulation and experimental results.

Reduction of motor overvoltage fed by PWM AC drives using a universal model

A. Bezzolato, M. S. Carmeli, L. Frosio, G. Marchegiani, M. Mauri

Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011) // 15 September 2011

High power photovoltaic plants are usually constituted of the connection of different photovoltaic subfields, each of them with its interface transformer. Different solutions have been studied to improve the efficiency of the whole generation system. In particular, transformerless configurations are the more attractive one from efficiency and costs point of view. This paper focuses on transformerless photovoltaic configurations characaterised by the parallel connection of interface inverters. The problem of zero sequence current due to both the parallel connection and to the presence of undesirable parasitic earth capacitances is considered and a solution, which consists on the synchronisation of PWM triangular carrier is proposed and theoretically analysed. The theoretical analysis has been validated through simulation and experimental results.