Adelino J. C. Pereira

Generation Expansion Planning in Competitive Electricity Markets

This paper describes a formulation to solve the long-term power generation expansion planning assuming a competitive electricity market. In a competitive environment each company aims at maximizing its profit through its individual expansion plan. In this formulation there is an inter connection between the expansion plans proposed by each company in the sense that the decisions taken by each company are influenced by decisions of the other players. In this formulation we assume there a centralized entity in charge of evaluating each plan both technically and economically taking into account a set of pre established constraints. As a result of that assessment, this centralized entity sends new information to the players. Using this scheme it is possible to assess the influence that the decisions of each company have in the decisions of its competitors, leading to the referred interconnection. The adopted solution approach is based in the decomposition of the global problem in a main problem to be solved by the independent system operator (ISO), and in several sub problems one per generating company. Finally, the paper includes a Case Study Designed to illustrate this approach as well as its interest for several agents acting in the electricity market.

Reactive Power Support in the Dynamic Voltage Stability Assessment of a Restructured Electric Power System

In recent years, the electricity sector undergoes a restructuring process, operationally and commercially, moving from a vertical integrated model to a market oriented model. With past and current difficulties in building new transmission lines and the significant increase in power transactions associated with competitive electricity markets, maintaining system security, with special regard to voltage instability/collapse issues, is more than ever one of the main concerns for market and system operators. Voltage is most readily controlled by adjustments to reactive power injections in power system. Reactive power can be produced and absorbed by both generation and transmission equipment. System operators, transmission owners, generators, customers, power marketers and government regulators need to pay close attention to voltage control. This paper is devoted to the study of the reactive power support for dynamic voltage stability of a restructured electric power system. A severe contingency situation was simulated. The automatic voltage regulators of the generating units and the mechanically switched shunt capacitors were modelled. The simulation results were obtained using the commercial transient software package EUROSTAG. Finally, some conclusions that provide a better understanding of the voltage collapse phenomena are pointed out.

Long term impacts of RES-E promotion in the Brazilian power system

This paper analyzes the impact on market prices of the policies that have been adopted in Brazil to foster electricity from renewable energy sources (RES-E), namely wind power. In recent years the Brazilian Government implemented a series of policies that enabled a strong growth of RES-E. Recently more than 14 GW of wind and solar power were contracted. However, as most of the assets are concentrated in specific regions, these policies will induce price differences among areas of the country. In this scope, this paper describes a System Dynamics based model of the Brazilian generation system to evaluate the impact on prices from the deployment of these new sources. The paper describes simulations using realistic data for the Brazilian power system and the results suggest that the difference of prices in the country tend to increase since the Northeast region of the country concentrates most of the wind parks.

Long term expansion planning of the Brazilian generation system using dynamic systems

This work has been conducted in order to develop a Generation Expansion Planning model based on Dynamic Systems to come up with a new approach to be applied to the Brazilian generation system regarding the one currently used. Moreover the new model intends to become a flexible tool to evaluate scenarios regarding the power sector evolution. Dynamic Systems have a wide range of applications. The use of these tools has been gaining success in the power sector by their ability to observe and model interdependences and feedbacks between the different system variables. This kind of approach was then implemented in many power systems. The work is introducing new features to this approach based on specific characteristics of the Brazilian Power System, namely: the large penetration of hydropower and the possibility of energy storage; seasonality of power generation; existence of electricity submarkets with transmissions constraints between them. The results obtained so far show that the Dynamic System developed can represent in good conditions the main features of the Brazilian system, whereas it identifies and correctly shows patterns of water management and energy prices that comply with the reality. These results show that the approach under development can become a valuable asset for both public entities that perform long-term plans and for power system agents.

Economic evaluation of wind generation projects in electricity markets

Investments in new generation, specially in renewables, grew up in several countries contributing to change the generation mix. Among these new technologies, wind power became an important source in the sense that the share in installed capacity is large in countries as Germany, Denmark, Spain and Portugal namely considering the prices paid to the generated power. These subsidizing schemes are in several cases responsible for a large amount of the final end user costs meaning that in the future new ways of integrating this power in the grid have to be adopted. This means that for investors it is important to evaluate from a economic point of view the interest of new wind power projects admitting changes in current tariff schemes. For regulatory agencies it is also important to investigate the impact of changes in current schemes. This paper details an approach to characterize this type of investments in terms of the Net Present Value, NPV, and the Internal Return Rate, IRR, so that more sounded investment and policy decisions are adopted.

Dynamic voltage stability assessment of an electric power network using composite load models

Electric power network stability analysis requires that all system components are represented by their models. Usually, detailed data about system components such as generators, transformers and transmission lines are available. In this case accurate models can be derived from the network devices. However, corresponding data for individual loads are not always available, which makes the modelling of loads an important area of research studies. In this paper it is studied and analysed the effect of the composite load models in the dynamic voltage stability of an electric power network. The composite load models comprise residential, commercial and industrial loads. A severe contingency situation was simulated. The automatic voltage regulators of the generating units, the turbine speed governors, and the under load tap changers models were taken into account. The simulation results were obtained using the EUROSTAG software package. Finally, some conclusions that provide a better understanding of the dynamic voltage stability are pointed out.

Analyzing the influence of climate change in Brazilian electricity markets

The Brazilian Power System is mostly supplied by hydro-generation. In this context there is a strong connection between rain-fall regimes and the Electricity Prices in the short term market. This work describes the main features, developments and functioning of a System Dynamics model that simulates the four Brazilian short term electricity submarkets. Based on studies reporting the change in rainfall regimes in Brazil due to Climate Change, we analyze the impacts of these changes in each specific region and in the electricity markets as a whole. The results provide good insights on the impacts of Global Warming in the Brazilian Power System, indicating for instance that the Southeast/Center-West Electricity Submarket is the one that will be most affected by the global issue in terms of rise in the electricity prices.

STATCOM to improve the voltage stability of an electric power system using trajectory sensitivity analysis

The voltage stability security is a very important and relevant issue in the modern power networks. The voltage instability can drive the system to a blackout. One of the methodologies to deal with this problem is analysing the trajectory sensitivity of the system. The STATCOM is an important hardware that is used to improve the voltage stability of an electric power network. The main objective of this paper is to analyse the results of different studies that were realized in a power system with wind farms. The wind farms were modelled considering that the wind turbines were equipped with pitch control coupled with a Permanent Magnet Synchronous Generator. The EUROSTAG program was used to obtain the simulation results. The Matlab software package was used for the post-processing module developed.

STATCOM to improve the voltage stability of an electric power system with high penetration of wind generation

In the last years, the high penetration of renewable energy sources, especially wind power generation poses new challenges for the dynamic voltage stability analysis of an electric power system. The wind power plants are required to be able to satisfy the voltage control strategy and reactive power demands. The wind power plants should provide the reactive power exchange with the grid, due to the present of high penetration level of wind power in the system. The exchange rate and level are specified by the transmission system operator. Wind farm model based on Permanent Magnet Synchronous Generator equipped with STATCOM was developed using the EUROSTAG software package. The automatic voltage regulators of the generating units and the turbine speed governors were modeled in detail. Different load models were used and the load tap changers were taken into account too. In order to assess the power network voltage stability several contingency were simulated. An increase of the wind speed was also took in account during the simulations. Finally, some conclusions that provide a better understanding of the dynamic voltage stability of a system using various capacities of STATCOM are pointed out.

Impact of variable renewable energy in the Iberian Electricity Market

Market and system operators face new challenges as more renewable energy sources are added. The driving factors in this trend are mainly associated with environmental benefits of the renewable generation and climate change mitigation, as well as the reduction of the dependency of conventional and external energy source. If integrated in large scale, the nondispatchable nature of intermittent resources imposes some technical and economic challenges on the operation of power systems. Particularly, market dynamics and prices could be influenced by such integrations. Over the last years, the generation mix of Spain and Portugal has undergone a dramatic change, driven by new environmental policies and financial incentives. In this regard, wind has become one of the most popular alternative sources of energy, bringing new challenges from the operational and structural point of view. This trend has gone hand in hand with integration of both markets into the Iberian Electricity Market in 2007. This paper presents a simple methodology based on linear regression and variance decomposition in order to quantify the impact of wind generation on specific segments of the Iberian Electricity Market (MIBEL).