Tatiana M. L. Assis

Automatic Reconnection From Intentional Islanding Based on Remote Sensing of Voltage and Frequency Signals

This paper presents a control strategy for automatic reconnection of a microgrid after an intentional islanding. Remote signals of voltage and frequency at both sides of the coupling circuit breaker are communicated to the generating site, and used as additional signals to the voltage and speed control loops, respectively. The proposed automation strategy is simulated on a real MW-scale microgrid located at a rural area in Rio de Janeiro, Brazil, and supplied by two small hydro synchronous generators. The results show that a smooth reconnection of the microgrid to the utility grid can be achieved when the proposed automation is utilized.

Dynamic Transmission Capability Calculation Using Integrated Analysis Tools and Intelligent Systems

Summary form only given. This paper presents a methodology to calculate the transmission capability between two areas in a power system, considering both static and dynamic security assessment. An optimal power flow (OPF) algorithm is used to compute the transmission capability from the static point of view. The dynamic security assessment of the operating point obtained from the OPF is then evaluated. Transient, voltage and small-signal stability assessment are considered. If any dynamic security criterion is violated, additional constraints are added to the original OPF formulation, and a new and secure transmission limit is calculated. These new constraints can be very simple, such as to limit the transmitted power, or more elaborated, based on some rules obtained from an intelligent system. The results for two test systems have shown the potential benefits of the proposed methodology and the importance of considering different dynamic aspects in transmission capability calculation.

Data Compression in Smart Distribution Systems via Singular Value Decomposition

Electrical distribution systems have been experiencing many changes in recent times. Advances in metering system infrastructure and the deployment of a large number of smart meters in the grid will produce a big volume of data that will be required for many different applications. Despite the significant investments taking place in the communications infrastructure, this remains a bottleneck for the implementation of some applications. This paper presents a methodology for lossy data compression in smart distribution systems using the singular value decomposition technique. The proposed method is capable of significantly reducing the volume of data to be transmitted through the communications network and accurately reconstructing the original data. These features are illustrated by results from tests carried out using real data collected from metering devices at many different substations.

Mid and Long-Term Voltage Stability Assessment using Neural Networks and Quasi-Steady-State Simulation

This paper presents a methodology to estimate voltage stability margin using artificial neural networks (ANN). During the training process, a quasi-steady-state (QSS) simulator is used, so the slow dynamic devices, which are important in the voltage stability assessment, are adequately modelled. The results obtained for a test system have shown the potential benefits of the proposed methodology and the importance of considering slow dynamic aspects when the voltage stability margin is to be calculated.

Long and short-term dynamic simulations in distribution networks with the presence of distributed generation

Distributed generation or distributed resources is the use of small-scale power generation technologies located close to the load. This paper analyzes long and short-term dynamics in a system with the presence of distributed generation. The studied system is a real distribution network located in Rio de Janeiro, Brazil. To study long-term dynamics, a fast simulation technique is used. On the other hand, to study short-term dynamics, full time-domain simulation is employed. All analyses were performed using a computational program that integrates these analyses tools in a unique platform. The main characteristics of the software are presented. The simulation results show that distributed resources can have a significant impact in the system for different types of distributed generators

Integrating solution engines under a distributed processing environment: An alternative approach for static and dynamic security assessment of large scale power systems

This panel paper describes the initiative underway led by the Brazilian Electric Energy Research Center (CEPEL) in collaboration with Brazilian Universities aiming to the development of a static and dynamic security assessment (SDSA) tool for both operational planning and real time applications. The SDSA tool under development is based on the solution engines of two software tools largely used in the Brazilian power industry for load flow (Anarede) and dynamic simulation (Anatem).

Transmission limits evaluation in hydro-dominated power systems

This paper addresses the evaluation of total transfer capability in hydro-dominated power systems focusing on the Brazilian interconnected power systems. The methodology currently adopted by the Brazilian national system operator to compute transfer limits is presented. A methodology that automatically integrates optimal power flow, transient, small-signal and voltage stability simulation is also discussed. Results obtained with the techniques described are presented.

Chapter 25 – Intentional Islanding of Distribution Network Operation with Mini Hydrogeneration

The abundant presence of large river basins made Brazil a worldwide powerhouse of hydroelectricity. To maintain its long-tradition of clean energy producer, Brazil also is investing in mini hydro plants, of few megawatts, able to supply small towns in rural areas. This chapter focuses on a real case study of a mini hydro power plant connected to a rural distribution feeder. The investigations presented in this chapter highlight important stages for a successful intentional islanding operation. Those are the detection of the islanding, the necessary change in the control modes of voltage and frequency regulation, the islanding formation with load/generation balancing, the islanding autonomous operation and the reconnection to the main grid. Although, not yet established as a common practice in Brazil, islanding operation of renewable DG can improve reliability indices and help the human effort in diminishing global warming, if technically sound solutions are applied.

Impact of Multi-terminal HVDC Grids on Enhancing Dynamic Power Transfer Capability

This paper proposes the exploitation of multiterminal HVDC grids to improve transfer capability in power systems. Multiterminal HVDC systems based on voltage source converters (VSC-MTDC) have been recognized as a promising alternative for the wind power integration. Under low wind scenarios, these grids originally dedicated for wind power transmission can be exploited as an additional interarea transmission path, providing extra dynamic security. The paper focuses on small-signal stability assessment, especially in poor damped oscillations associated with interarea modes. Simulations performed through a generic computational framework have shown that the high level of flexibility and controllability provided by voltage source converters can considerably improve the transfer capacity, while preserving adequate dynamic performance.

Highlighting the Importance of Chronology on Voltage Protection and Control in Active Distribution Networks

This paper highlights the importance of chronology on voltage protection and control apparatuses in studies of voltage security in active distribution networks with high generation capacity. This paper presents simulation results of a real-life example of a long rural distribution feeder having three voltage regulators in cascade, and a customer whose demand accounts for a large percentage of the total feeder load. The customer is also an independent power producer and its location at the far end of the feeder yields an intricate voltage protection coordination when the customer ramps up and down its own generation at the peak-demand period.