A. C. Zambroni de Souza

Quasi-Dynamic Model and Strategy for Control Actions

This article discusses some aspects related to long term stability analysis of power systems. A quasi-dynamic model is employed, which enables us to consider the effects of discrete control actions. In this article, these actions are: capacitor switching, load tap changers and AVR set point adjustment. If these actions are not enough, load shedding is executed. This article focuses on preserving the system stability, while enhancing the post fault equilibrium point. For this sake, an approach to detect the instant of tap blocking and a methodology for load shedding calculation are proposed. The results are carried out with the help of the modified IEEE-14 and 57 bus systems.

Proposição de uma metodologia de avaliação dos limites de intercâmbio em sistemas de grande porte: desafios para automação

Power transfer limits calculation has to be performed taking into account static and dynamic aspects. Therefore, a huge amount of data needs to be manipulated. The transfer limits values are important in power system planning analysis, as they might represent an energetic constraint between two or more systems. In this way, besides the different load conditions, the limits calculation must consider different energetic scenarios, which increases even more the task of operational points adjustment. The related process is addressed through different ways around the world. In Brazil, a low level of automation is observed. In order to help on this task development, the paper presents a methodology to calculate power transfer limits between different areas, using an optimal power flow program. The proposed method is adequate for applications in the Brazilian power system.

The influence of renewable generation in voltage collapse indexes

As the penetration of renewable energy sources occurs, the power system configuration becomes more complex due to the intermittence of these generation sources. Thus, this paper studies the influence of renewable sources generation in the behavior of voltage collapse indexes. The system load margin is also addressed and the different operating scenarios allow one to analyze how the critical buses may change. The idea is tested by employing a modified IEEE-118 bus system. The modifications consist in considering local renewable sources.

A secondary control based on fuzzy logic to frequency and voltage adjustments in islanded microgrids scenarios

This paper aims to propose a secondary control algorithm based on Fuzzy Logic to adjust frequency and voltage in islanded microgrids. It is well-known, that, when a microgrid changes its operation from grid-connected to islanded mode, the time domain variability of the loads will change the frequency and voltage profiles of the system. In this sense, the operation of the system might become unsafe and out of the acceptable ranges of quality. It is essential that the MGCC be able to restore the frequency and voltage through the secondary control. In this context, a Fuzzy approach is proposed to change the frequency and the voltage reference values in the droop equation of the Voltage Sources Inverters to correct them. The main idea of this paper is to consider these variables uncoupled and then correct each one separately, taking into account that the frequency is global and the voltage is local variables of the system. As results of this work, this paper brings the frequency and voltage profiles of a modified IEEE Feeder Test during a random day, showing the behavior of theses variables with and without the proposed algorithm.

Particle Swarm Optimization applied to reactive power compensation

This paper employs a particle swarm optimization program (PSO) to address the problem of reactive power compensation with the aim of voltage security. For this sake, a particle swarm optimization program (PSO) is employed to identify the buses to experiment reactive power compensation. The reason why this method is chosen lies on the wide range of applications described in the literature. The adaptability of the method is explored here. Reactive power compensation is a particular area of application and is better achieved by selecting a group of buses to be considered by the PSO. Such a group consists on the critical buses under the voltage collapse point of view, buses most sensitive to loss reduction and the ones subject to reactive power monopoly, assessed by the Herfindahl-Hirschman Index (HHI). The proposed methodology is assessed by employed an IEEE sample test system (IEEE 30-bus system), so the results may be replicated.

Impact of non-linear loads and renewable generation on a university research building

As modern society electrical energy consumption requirements increase, a growing need for more efficient and lower costs power electronics processing devices is featured. Even though this kind of devices have high efficiency, it creates a problem by injecting harmonic currents. This paper aims to address the harmonic distortion impact caused by non-linear loads and renewable generation on a typical university research building connected at the distribution system level. For this sake, actual data from the Centre of Excellence in Smart Grids (CERIn) featuring Uninterruptible power supply (UPS), Relays, Real Time Digital Power System Simulator (RTDS) and distributed generation (DG) were considered and three occupancy rates were held, low, average and high scenario. The results indicate desktop computers as major contributors to the harmonic losses. For special loads, the UPS 5th harmonic presents itself as the second greatest influence, while Relays and RTDS have an average participation. These results allow a better understanding and definition of measures to reduce the harmonic impact, cancellation techniques and filtering.

Demand profile processing methodology for information acquisition

The demand profile knowledge is vital for a wide variety of power systems studies. Furthermore, meaningful information may be obtained regarding optimization and maximization decision-making strategies that may help a wide variety of consumers optimize their facilities usage, redefine low priorities equipment operating hours, as well as promote actions seeking production increase. With the spread of Smart Grids, this data is becoming easily available through the complete system range. Therefore, this study proposes a processing methodology that aims to make the information hidden at the load profile readily accessible at any level. For this sake, two processing stages are employed, first the profile is filtered by a Windowed Sinc filter and then a linearization process is performed. To validate the methodology high, average and low demand profiles from the Centre of Excellence in Smart Grids (CERIn) were considered. The results exhibit an efficient methodology capable of clearly provide meaningful information regarding the demand profiles.

Critical Lines Identification on Voltage Collapse Analysis

This paper deals with critical lines identification on voltage collapse analysis. It is known, from the literature, that voltage collapse is a local phenomenon that spreads around an initial neighborhood. Therefore, identifying the system critical bus plays an important role on voltage collapse prevention. For this purpose, the system critical transmission lines should also be identified. In this paper, these issues are addressed, yielding reliable results in a short computational time. Tests are done with the help of the IEEE-118 bus and the Southeastern Brazilian systems.