Lucian Toma

Optimal SVC placement in electric power systems using a genetic algorithms based method

The problem of improving the voltage profile and reducing power losses in electrical networks is a task that must be solved in an optimal manner. At present time, this optimality can be achieved by efficient usage of existing facilities alongside with installing FACTS devices. The Static VAr Compensator (SVC) was chosen for study as its maturity and acceptable costs make it more usable in practical applications than other FACTS devices This paper proposes a genetic algorithm that tries to identify the optimal location and size of an SVC. A multi-criteria function is developed, comprising of both operational objectives and investment costs. The computer program is run on a 13 nodes test system, assessing improvements in voltage profile and reducing power losses. The purpose of this study is to validate the solution method in order for it to be adapted for systems of higher dimensionality.

Integrating the Electrical Vehicles in the Smart Grid through unbundled Smart Metering and multi-objective Virtual Power Plants

This paper presents a solution for integrating Electrical Vehicles in the Smart Grid through unbundled Smart Metering and Virtual Power Plant technology dealing with multiple objectives. Within this frame, EV can benefit of cost-effective energy during the charging period but can also provide multiple ancillary services to the network, by wisely using their storage capability and their flexibility in coupling to the grid. Simulation of an EV providing services under a multi-objective VPP is also presented, with analysis and conclusions about the technical feasibility of such applications.

Studies on a LV DC network

In this paper, one application targeting a small-scale DC network supplying signal processing laboratory (personal computers, universal motors and other low-voltage, low-power loads) is proposed, in order to analyze the technical interconnecting possibilities of isolated power systems. As a first step, simulations using the already implemented network elements models in DIgSilent were performed in order to choose an optimal location of the generation units, considering restrictions related to available space, safety and future development. The next step was to develop mathematical models of the loads characteristics when each module is supplied with direct voltage, in order to further test direct DC supply of the laboratory. The paper is a consequence of the new approach oriented to innovative technologies for integrating dispersed and intermittent sources (DG) into distribution networks.

The control of isolated power systems with wind generation

The present work investigates the dynamic behaviour of a mixed system consisting of a wind farm and a diesel group supplying a load, under different disturbances. In this regard, dynamic models and control systems that enable the generation part to support the grid are needed. The objective of this work has been also the implementation of the diesel group model and its afferent control system into Matlab-Simulink and to demonstrate their use by evaluating the response in time of the electric parameters.

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.

Trading Ancillary Services for Frequency Regulation in Competitive Electricity Markets

With the introduction of the electricity market the system operators as well as the market operators are facing more and more unpredictable challenges. As a completive for the Day Ahead Market, the Balancing Market is meant to perform a more market oriented frequency regulation by using a merit order for real-time dispatch of the generators, particularly for the secondary regulation as well as for the tertiary regulation. Due to the social implications of the electricity market, the market mechanism should be designed so that to avoid market speculations of some participants and to obtain the smallest price possible of energy and ancillary services while maintaining a necessary active power reserve to ensure a certain level of the network security. Based on the actual expected changes in the generation sector of the Romanian power systems as well as the implementation of a possible regional market, the authors will propose some suggestions for the balancing market mechanism to maximize the reserves available for frequency regulation and to minimize the cost of the regulation energy. A comparison between actual implemented mechanism and the proposed mechanism will be performed.

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.