George Cristian Lazaroiu

High power quality and DG integrated low voltage dc distribution system

The liberalization of the energy market determined the growth of customers concerns supplied by various utilities regarding the quality of services provided. The ensuring of a proper supply continuity level and the achieved stage of development by the distributed generators (DG), have determined the consideration of realizing a low voltage dc distribution system. In this paper, a low voltage dc distribution system with distributed generators and storage energy system is studied. The components of this dc power system are modeled and the control logic, taking into consideration the islanding operation constraints, is described

A Matlab-Simulink flickermeter model for power quality studies

The paper deals with the representation of the flickermeter operation in the Simulink software program. This can be useful in case of simulation studies related to power plants where flicker phenomenon can rise up due to the presence of heavy disturbing loads (i.e. arc furnaces). The standard block diagram of the flickermeter is analyzed and reproduced in software blocks dedicated to the modeling of its different components. A validation procedure on a real case is adopted for testing the proposed model.

Bidirectional Front End Converter for DG With Disturbance Insensitivity and Islanding-Detection Capability

This paper introduces and develops a new control strategy for the bidirectional front end converter for grid-connected distributed generation units. In the method, the switching technique directly controls the current of the voltage-source converter. The switching method is based on the evaluation of the inductor-flux error trajectory which allows to predict the next commutation instant. The control is fast and the line-current waveform is insensitive to the grid voltage perturbations or harmonics, and dc bus disturbances. A new frequency detection algorithm, robust against disturbances and with fast response in case of islanding occurrence, is introduced and applied. The proposed control method has been examined under various scenarios, including mains supply faults, distorted and unbalanced grid, and IEEE 1547 anti-islanding test. The results show the feasibility and applicability of the proposed control for the considered electronically-interfaced distributed generation units.

DC power delivery in distributed generation systems

The ensuring of a proper supply continuity level and the achieved stage of development by the distributed generators (DG), have determined the consideration of realizing a low voltage DC distribution system. In the paper the authors propose a DC distribution system with interconnect distributed generators and storage devices, with the purpose to guarantee high voltage quality levels in case of AC mains disturbances. The case studies conducted bring to promising and interesting results.

Probabilistic method for harmonic analysis in railway system

The paper deals with the applications of probabilistic methods to the harmonic analysis in currents and voltages present in railroad power supply systems. The theoretical study is applied to a real case of a dc traction railway in operation in Italy. The results show the possibility to represent the system with a normal distribution and highlight the main parameters that have to be evaluated. At the end, some examples are reported as application of the used probabilistic model.

Snail Trails and Cell Microcrack Impact on PV Module Maximum Power and Energy Production

This paper analyzes the impact of the snail trail phenomena on photovoltaic (PV) module performances and energy production. Several tests (visual inspection, maximum power determination, dielectric withstand, wet leakage current, and electroluminescence test) were carried out on 31 PV modules located in a PV plant in Italy. The electroluminescence test highlighted the strong correlation between the appearance of snail trails and presence of damaged cells in PV modules. The daily energy produced by four PV modules affected by snail trails ranged between 68% and 88% of the energy produced by a damage free commercial PV module over the same period.

Impact of embedded generation on the voltage quality of distribution networks

The increasing concerns related to the global warming process determined the shifting towards the use of distributed generation (DG) designed to meet the environmental restrictions. The increasing penetration rate for the DG in the energy systems is raising technical and non technical problems that must be quickly solved in order to deeply exploit the opportunities and benefits offered by the DG technologies. In this paper, the analysis of the impact of distributed generation units on the voltage quality in a 6 kV medium voltage network is conducted. The distributed generation units may require an inverter before their interconnection to the mains. Thus, these converters can produce harmonics that propagate in the distribution network. The case studies are conducted using the software package ATP- EMTP on an existing 6 kV network.

Virtual power plant with energy storage optimized in an electricity market approach

This paper deals with the mathematical formulation and implementation of the optimization model for virtual power plants (VPPs). The daily optimized operation of the VPP is focusing on maximizing its benefit, considering VPP comprising renewable energy sources and energy storage systems, thermal engines and demand-response loads. The optimization model is tested considering two case studies of average electricity prices on the day-ahead market, each of them in four scenarios of the mix renewable energy sources. The model, analyzed on a 24 hours time horizon, is implemented and tested in GAMS. The obtained results show that the best benefit obtained by the virtual power plant owner is obtained when the energy production of analyzed available renewable energy sources is high, and the day-ahead market prices are elevated. In the present paper, the case when the power system operator constraints the exchanges with the virtual power was not considered.

Smart campus-an energy integrated approach

This paper analyzes the optimized operation of smart campus on the electricity market for maximizing his overall profit. The smart campus has the character of a virtual power plant with distributed energy resources with stochastic power and dispatchable classical generating units. The load is represented by the campus consumptions which can be shifted daily to accomplish the desired goals. This smart campus optimizes the use of electrical energy through exchanged electricity with the market and thermal energy through internal production such that to maximize his yearly profit.

Analysis of sustainable and competitive energy system

The climate change is increasingly apparent and the need to be independent for the sourcing of energy sources has led to the establishment of the European Community financing schemes to support research and development of systems in place to decrease pollution and independence from fossil fuels. One way to catch up with greater conviction this scope is the production of energy at a large scale, using renewable sources. Now, the incentives are even a fundamental element for the development and competitiveness of these systems, but it is clear that if the policy guidelines will converge in the direction of Horizon 2020, the possibility of implementing such systems will become a model easily replicable and suitable. In this context, this work aims to show how a production system that exploits solar energy, through a plant collector, can be comparable in terms of cost with other energy sources. In particular, an estimate is made of an economic system with solar collectors for the production of electrical energy, starting with the year of production and on the basis of 25 years of life of the plant.