Mircea Eremia

Interdependency of Natural Gas Network and Power System Security

This paper proposes an integrated model for assessing the impact of interdependency of electricity and natural gas networks on power system security. The integrated model incorporates the natural gas network constraints into the optimal solution of security-constrained unit commitment. The natural gas network is modeled by daily and hourly limits on pipelines, sub-areas, plants, and generating units. The application of fuel diversity (e.g., generating units with fuel switching capability) is presented as an effective peak shaving strategy for natural gas demand which could hedge price volatilities of natural gas and electric power. The proposed model can be used by a vertically integrated utility for the commitment and dispatch of generating units and the allocation of natural gas for the next day utilization. The proposed model can also be used for measuring the security of social services by modeling the interdependency of natural gas and electric power system infrastructures. If the proposed model is used by GENCOs, gas constraints will be submitted to electricity markets as energy constraints. Illustrative examples show the impact of natural gas supply infrastructure on the economic operation of a vertically integrated utility. The examples also discuss the impact of generating units with fuel switching capability on the power system security when the supply of natural gas is limited.

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.

Optimal Distributed Generation Location and Sizing Using Genetic Algorithms

The paper proposes a comparison between nonlinear optimization and genetic algorithms for optimal location and sizing of distributed generation in a distribution network. The objective function consists of both power losses and investment costs and the methods are tested on the IEEE 69-bus system. The study covers a comparison between the proposed approaches and shows the importance of installing the right amount of DG in the best suited location. Studies show that if the DG units are connected at non-optimal locations or have non- optimal sizes, the system losses may increase.

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.

Advanced Solutions in Power Systems: HVDC, FACTS, and Artificial Intelligence: HVDC, FACTS, and Artificial Intelligence

This book presents advanced solutions for power system controllability improvement, transmission capability enhancement and operation planning. The book is organized into three parts. The first part describes the CSC-HVDC and VSC-HVDC technologies, the second part presents the FACTS devices, and the third part refers to the artificial intelligence techniques. All technologies and tools approached in this book are essential for power system development to comply with the smart grid requirements.

Some aspects of hierarchical voltage-reactive power control

The paper presents some contributions regarding hierarchical voltage reactive power control. The studies for classification of the zones for the hierarchical voltage-reactive power control, led the authors to the conclusion that the use of mutual node voltage influence indices should be preferred to the use of nodal impedance matrix elements. For the Romanian power system, the zones determined for voltage control are not very much different than the existing zones for operation and control by hierarchical dispatching centers. The mathematical model of secondary control function for the Romanian power system was studied taking into consideration the case of constant reactive power circulation between zones and the case of modified reactive power circulation on the inter-zone links. For the optimisation function, specific to the tertiary level of voltage control, the authors propose a method that combines the robustness of the genetic algorithms and the fuzzy logic possibility to combine easy and intuitive different optimisation criteria into a single evaluation function. The model has been applied to the Romanian power system. The results have confirmed the efficiency of hierarchical voltage control for the Romanian power grid from the perspective of the UCTE interconnection.

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.

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.

Quantifying the risk of a blackout using PSA/Eurostag platform software

This paper is treating the problem of quantifying the risk of a blackout in a power system when realizing off-line simulations for dedicated power system analysis. The issue consists in the computation of the stability limit for a power system, the concept of steady-state stability reserve being reviewed. Even in off-line simulation the stability reserve of a power system is not a straight forward analysis. The difficulties appear when trying to solve the stability reserve aspect for a large power system. For this kind of electrical network the common well known analysis techniques are not available mainly due to computational burdens. Present paper is proposing an original methodology to find out the stability reserve of a power system. The main theme of this paper is particularly relevant in the light of the blackouts that affected utilities all around the world recently. For preventing blackouts first step consists in analyzing and studying the reasons and the mechanism of the registered blackouts. The second step is to understand how to prevent the blackouts. Present paper is focusing of the second step in preventing blackouts by finding out a methodology to assess the stability reserve for a power system or a specific area from a power system beyond that a blackout might appear.