Ion Tristiu

Multi-criteria Reconfiguration of Distribution Electrical Networks for Minimization of Power Losses and Damage Cost due to Power Supply Interruption

The paper presents a reconfiguration method for electrical distribution networks under normal operating conditions. The method uses a multi-criteria objective function that considers economic related aspects: the cost of power losses and the cost of damages due to power supply interruption following some faults occurring into the distribution network. The restrictions of the optimization problem are related to arborescence, connectivity and the security of the electrical network subject to the thermal limit of the network branches and voltage level at the consumers. A heuristic method is applied to solve the mathematical model, which consists in searching into the solutions space based on a branch exchange strategy.

Coordination of distributed generators through the virtual power plant concept

In this paper the authors propose a market strategy of a microgrid incorporating a virtual power plant. For exemplification, a configuration consisting of different types of distributed generators and a lumped load are considered. The aim of the virtual power plant is to maximize the profit by minimization of the total cost involved for electrical energy generation by the distributed generators that are part of the virtual power plant.

Power transfer capacity enhancement using SVC

This paper presents the results of a feasibility study for installing FACTS devices in the South-Eastern part of Romanian power grid (Dobrogea - a peninsular area), to increase the transfer capacity to the rest of the grid. This study assumed, on one hand, the scheduled increase in generated power in the area, mainly due to two new units in the Cernavod ă nuclear power plant (1400 MW installed power) and wind generation with an estimated installed power of over 1600 MW. On the other hand, the scenarios considered the present topology and future developments of the transmission network. The increase in generated power in the S-E part of the power grid may lead to changes in the power market schedules, causing generation decrease or even shut down of other generators, leading to power flow changes and power system stability problems.

Market strategy of distributed generation through the virtual power plant concept

In this paper the authors propose a market strategy of a microgrid incorporating a virtual power plant. For exemplification, a configuration consisting of different types of distributed generators are considered. The aim of the virtual power plant is to maximize the profit by appropriate bidding strategy on the electricity market and optimal use of the sources.

On-line power systems voltage stability monitoring using artificial neural networks

A method for on-line voltage stability monitoring of a power system based on Multilayer Perceptron (MLP) neural network is proposed in this paper. Considering that the power system is operating under quasistatic conditions, by using power flow model and singular value decomposition of the reduced Jacobian matrix, a suitable index to quantify the proximity of power system voltage instability is defined. Then, a neuronal network is trained to learn the correlation between the key factors of the voltage stability phenomena and this index. Once trained, the neural network provides the above mentioned voltage stability index as output for a predefined set of input variables that are known as directly influencing the stability conditions of the power system. Since the input variables for the neural network may be obtained from the steady state estimator, the proposed method can be implemented as a function of the Energy Management System (EMS) for on-line voltage stability monitoring. Tests are carried out using the IEEE 30-bus system, where different operating scenarios are considered.

Quality cost of power supply and pay-back capital of this

This paper reviews the importance of improving the power supply quality. It presents the main stages for a study of amelioration or improvement of the power quality. A basic description of accounting of the damages caused by poor quality of the electric power is given together with different examples. Then, solutions for pay-back possibility of the quality costs for electric power suppliers and power consumers are identified.

Optimal generation scheduling strategy in a microgrid

This paper presents a strategy for optimal generation scheduling in a microgrid. Several small generation units of different type are considered, that is a wind system, a photovoltaic system and a gas engine unit. In order to maximize the use of renewable energy sources (RES) a storage battery is also integrated. Two generation scheduling algorithms are elaborated, either aiming at minimizing the use of fuel based unit or at maximizing the lifetime of the battery. The simulations have been performed in Matlab.

A new mathematical model for assessing optimization decisions of the loading factor flowing through substation transformers

The paper proposes a new mathematical model used to determine the optimum loading for power system substations equipped with only one transformer. Because of the cyclic way of the planning process, the capacity and density of electrical substations are influenced by the technological progress and previous adopted measures. Operations knowledge comes in handy in day by day activities but only strategic knowledge confers electric companies an edge. In comparison with the methods used until now, the proposed model takes into consideration aspects related to operation, monitoring and maintenance costs throughout the lifetime of transformers. The proposed model is applied to a 110 kV/MV transformer with different rated powers of 2.5, 16, 80, and 400 MVA considered for an electrical distribution grid. The goal is following tendencies instead of on-point.

Optimizing the costs of reactive power for the coordinated voltage control service

This paper presents a procedure for minimizing the costs involved with the reactive power - voltage control using the synchronous generators/compensators as ancillary service. The procedure combines an optimal power flow algorithm and the secondary voltage control algorithm, the first aiming to minimize the reactive power costs injected/absorbed by the synchronous generators/ compensators, while the second one assuming proportional loading of the generators with respect to their maximum capability limit. The reactive power of a generator can be controlled by the system operator by specifying a certain voltage at the generator terminals.

A perspective on current unbalance in low voltage distribution networks

This paper presents a mathematical model used to calculate the symmetrical components of the load current in electrical distribution networks of low voltage. Based on the mathematical model proposed power lines were calculated tasks under sinusoidal. Case studies dealt with non-symmetric mode due to load imbalance on the distribution network of low voltage. Analysis of case studies was done by modifying the actual values of the phase currents and differences related. Important assumption is that the distribution network is symmetrical phase voltages.