Gio Battista Denegri

An integrated active and reactive power control scheme for grid-connected photovoltaic production systems

The paper presents an advanced control scheme for a photovoltaic unit (PV) to suitably drive the injection of both active and reactive power into a MV radial distribution grid. Such algorithm allows a decoupled control of active and reactive power by properly adjusting the modulating signals of the PWM interface converter with the grid. A closed loop regulation scheme has been derived and guidelines for the design of the regulators are provided. The control algorithm has been applied to a real MV grid-connected PV power plant and several simulations have been performed in order to analyze the behavior of the system and to verify the effectiveness of the adopted regulation. The positive effect of reactive power support has been highlighted showing benefits on grid current and voltage profiles with respect to the typical case of the sole active power production.

A control algorithm for the maximum power point tracking and the reactive power injection from grid-connected PV systems

This paper deals with the use of large-size Photovoltaic (PV) units as providers of the reactive power compensation ancillary service. To do this, a suitable control scheme has been developed, which is based on an advanced control theory, called FeedBack Linearization (FBL), widely employed in the robotics field but still not so popular in power systems engineering. This allows to regulate both the injection of reactive power and the PV voltage, which is fixed to the value corresponding to the maximum power extraction from the PV unit, thanks to the implementation of an efficient MPPT algorithm, whose main features are described in detail. Several simulations are performed in the PSCAD-EMTDC electromagnetic environment to validate the proposed approach.

A methodology to quantify the impact of a renewed T&D infrastructure on EU 2020 goals

This paper addresses the issue of the evaluation of how modern and restructured Transmission and Distribution (T&D) infrastructures help accomplish the so-called EU 2020 targets, in terms of efficiency increase, CO2 reduction and a wider employ of renewable energy resources. A methodology is proposed in order to quantify the possible environmental benefits as well as the power quality improvement provided by the application of modern T&D products and systems on the power grids. Such methodology is based both on the identification of suitable “performance (technical) indices” to be used to rank the benefits brought by the different grid upgrading measures and on the definition of suitable “test networks”, which can be employed as benchmarks to perform the numerical evaluation of the introduced indices. Then, a procedure is presented in order to determine and compare the quantitative effect of each single corrective action on T&D power grids. Finally, some considerations on possible side effects and advices on strategies for the implementation of the corrective measures are discussed.

Improving power grids transient stability via Model Predictive Control

This paper proposes the application of Model Predictive Control (MPC) to ensure the stability of an electric grid following fault conditions. The technique is firstly described as a general tool; subsequently, the chosen model of the power system is detailed together with the specific requirements to be met by the control algorithm. Finally, the application of MPC strategy to a WECC (Western Electricity Coordinating Council) test case network shows that the effects of a contingency, that would bring the system to instability without any external action, are mitigated by the control action, leading the network to a new working point, as close as possible to the previous one and, most of all, without exceeding the stability limits.

The smart microgrid pilot project of the University of Genoa: Power and communication architectures

The aim of this paper is to describe the Smart Polygeneration Microgrid (SPM) test-bed facility at the Savona Campus of the Genoa University. The SPM constitutes a pilot plant for research, development and testing of management strategies, devices and components for smart grid applications. The main features of this infrastructure will be outlined, focusing on its power and communication architecture, based on the use of the IEC 61850 protocol and on a close integration between electric and heating networks. Furthermore, the activities which will be carried out thanks to the SPM and the challenges in its operation and optimal management will be reported, in the context of the current research on microgrid and smart grid technologies.

Performance and control of PhotoVoltaic systems supplying both primary and ancillary services

The paper presents a comprehensive study on grid-connected photovoltaic (PV) systems, dealing both with control strategy aspects and performance evaluation techniques. In particular, an advanced control scheme to suitably drive the injection of both active and reactive power into a MV radial distribution grid is here discussed, highlighting its main features by means of the numerical simulation of a real PV unit into the PSCAD-EMTDC electromagnetic environment. The developed circuit model is then used to derive the capability curve of the PV unit under study, thus enabling to characterize the whole system at its AC side.

The Use of a Static Series Compensator (SSC) for the Mitigation of Voltage Sags in a Radial Distribution Network

This paper investigates on power quality improvements provided by static series compensation in MV distribution networks. First of all, a simplified relationship between a fault in any position of a grid and a voltage sag experienced in another point of the grid itself is derived and its validity is verified by means of a detailed simulation performed in the PSCAD-EMTDC environment. Afterwards, the insertion of a static series compensator at a MV busbar of a typical Italian network is simulated and the benefits due to its voltage sag compensation capability are outlined, considering faults both at MV and HV levels.

Providing competitive ancillary services through efficient market structures

Most electric companies are facing structural changes due to increasing economic pressure towards deregulation and creation of power markets. One of the most critical issues still remaining open in this context is providing ancillary services competitively. The main focus of the paper is the implementation of a framework for the valuation of ancillary services that market participants are selling or buying, so that the optimal prices at which each service is exchanged will be more easily agreed by the parties. The quantifying method proposed in the paper is based on the relationship between the availability (the use) of the generic ancillary service and the state (the transition) the system is presently experimenting. The efficacy of the method is tested with reference to different active power services, given by spinning reserve and frequency regulation.

Classification, evaluation and acquisition criteria of recovery resources to provide ancillary services in power system restoration

The paper presents a theoretical framework to evaluate recovery resources to provide ancillary services in a liberalized power system. The available facilities are first identified and classified, then a general procedure is proposed to face both technical and economic issues involved in recovery services procurement. Restoration strategies are indeed investigated to determine the unsupplied energy while taking into account the uncertainty associated to the resource availability. The economic issue is finally tackled, within a multiple blackout scenario, in order to derive an optimal recovery resource set.

Dynamic Performances of AC Drives Fed from Power Transistor-Thyristor Inverters

A simulation procedure has been pointed out for investigating problems concerning road traction drives based on three-phase induction machines supplied by modulated inverters. The inverter employed is not conventional because it utilizes both thyristors and power transistors. The solution proposed allows weight and size to be minimized with respect to a conventional thyristor drive. As a consequence, the design presented meets, in a satisfactory way, the requirements of a drive that is to be used in an electric vehicle, In the simulation, the inverter is represented as an independent voltage generator which produces various voltage waveforms at the ac terminals. The induction machine is described according to a dynamic model based on Parks two-axis theory. A computer program has been used for simulation of the drive dynamics, and some quantitative results have been obtained with reference to an actual traction drive.