M. A. G. de Oliveira

Bio: M. A. G. de Oliveira is an academic researcher from University of Brasília. The author has contributed to research in topics: AC power & Renewable energy. The author has an hindex of 3, co-authored 3 publications receiving 228 citations.

Photovoltaic Generation Penetration Limits in Radial Distribution Systems

Abstract: Photovoltaic generating units connected to distribution systems represent a type of distributed generation (DG) that has been experiencing increased growth in recent years. Higher DG penetration levels may be interesting from many different points of view, but raise important issues about distribution system operation. Therefore, new techniques are needed to determine the maximum amount of DG that may be installed without requiring major changes in the existing electric power system. According to the literature, voltage rises at load bus bars are a serious limiting factor when installing DG. This paper presents and discusses studies proving that conductor ampacity and voltage rises are limiting factors that manifest themselves under different conditions. The present study highlights situations in which line overloads are more restrictive than voltage rises. Variation in substation voltage, load, and its power factor were simulated in a simplified radial distribution system model, and the amount of distributed generation that may be installed was obtained. Mathematic formulae were developed to determine the amount of distributed generation for existing utility systems.

A New Index for Absolute Comparison of Standalone Photovoltaic Systems Installed at Different Locations

Abstract: Photovoltaic (PV) system performance assessment is an important issue in determining how much energy is effectively used by PV-load systems. International Electrotechnical Commission (IEC) 61724 establishes the reference yield as the global irradiation in the plane of the PV array. Therefore, the performance ratio obtained is only valid where the PV system is located and does not allow the comparison between the performance of PV systems installed at different locations. Adopting a reference yield that is common to any location on Earth, a new absolute performance ratio (APR) is introduced. It uses the average annual irradiation in an extraterrestrial surface equipped with a Sun-Tracking System. The interest of the new index is demonstrated through a simple example were two identical standalone photovoltaic (SAPV) systems are compared. While the IEC method shows both systems to have similar performance, the APR points out that the cost of the energy produced by one system is half that produced by the other.

The Brazilian Renewable Energy Incentive Program - The Second Phase of the PROINFA: Assessing Policy Efficiency And Barriers in Long-term Scenarios

Abstract: The PROINFA is a Brazilian government policy which is divided into two phases and whose objective is to promote the expansion of power generation through renewable sources. This paper aims to assess the efficiency of the second phase with regard to long-term scenarios (2009-2030), identifying gaps and barriers, and proposing policy options to address them. In the first phase, the Program calls for the generation of 3,300 MW of renewable energy with a national business participation rate of 60%, aiming to maximize the countrys regional potentials, create jobs, reduce CO2 emissions through thermal (fossil) displacement, and promote energy contracts with differentiated conditions for conventional sources, as well as specific tariff/MWh for each source. The second phase fixes a 90% nationalization rate and a 15% Brazilian electrical energy annual consumption rate to be supplied by these sources. The goals of this phase are expected to be reached within twenty years, and the price will be a weighted average between competitive hydroelectric and thermoelectric (natural gas) prices.

Distributed Volt/VAr Control by PV Inverters

Abstract: A major technical obstacle for rooftop photovoltaics (PV) integration into existing distribution systems is the voltage rise due to the reverse power flow from the distributed PV sources. This paper describes the implementation of a voltage control loop within PV inverters that maintains the voltage within acceptable bounds by absorbing or supplying reactive power. In principle, this can be considered to be a form of distributed Volt/VAr control, which is conventionally performed by coordinated control of capacitor banks and transformer tap changers. Comprehensive simulation studies on detailed feeder models are used to demonstrate that the proposed control scheme will mitigate voltage rises.

Distributed Control of Battery Energy Storage Systems for Voltage Regulation in Distribution Networks With High PV Penetration

Abstract: The voltage rise problem in low voltage distribution networks with high penetration of photovoltaic (PV) resources is one of the most important challenges in the development of these renewable resources since it may prevent the maximum PV penetration considering the reliability and security issues of distribution networks. In this paper, the battery energy storage (BES) systems are used in order to solve the voltage rise during the peak PV generation as well as the voltage drop while meeting the peak load. A coordinated control strategy is proposed to regulate the charge/discharge of BESs using a combination of the local droop-based control method and a distributed control scheme which ensures the voltages of feeder remain within allowed limits. Therefore, two different consensus algorithms are used: the first algorithm determines the BESs participation in voltage regulation in terms of their installed capacity whereas the second one modifies the BESs performance in terms of their state of charge to prevent the excessive saturation or depletion of batteries. The proposed controller enables the effective use of storage capacity in different conditions. Finally, the simulation results based upon real data of a radial distribution feeder validate the effectiveness of this approach.

A review of high PV penetrations in LV distribution networks: Present status, impacts and mitigation measures

Abstract: The installed capacity of photovoltaic (PV) systems globally reached 177 GW at the end of 2014 The annual rate of installations, 387 GW in 2014, continues to increase A large part of this is installed as residential systems connected to low voltage (LV) networks The majority of the LV distribution networks are radial, unbalanced with respect to loads and feeder structures and have high R/X ratios The large scale deployment of PV within the LV distribution networks is limited by voltage quality problems, particularly over voltages and unbalance Development of proper mitigation techniques is essential to effectively and efficiently manage high penetration of PV within the LV distribution networks A number of techniques have already been developed and implemented in LV distribution networks to alleviate those problems This paper provides an extensive review of the present status, impacts and technical challenges of PV penetration in LV distribution networks In addition, the review comprehensively examines the commercially available and emerging mitigation methods and provides a framework that systematically explores the full range of technical methods and limitations for PV impact mitigation These will provide a useful framework and strong point of reference for the researchers working further in this field