Different Techniques for Simultaneously Increasing the Penetration Level of Rooftop PVs in Residential LV Networks and Improving Voltage Profile

Utilization of rooftop photovoltaic cells (PVs) in residential feeders without controlling their ratings and locations may deteriorate the overall grid performance including power flows, losses and voltage profiles. This paper investigates different methods for regulating the voltage profile and reducing the voltage unbalance at low voltage residential feeders. The algorithm considers reactive power exchange and active power curtailment of the single-phase rooftop PVs. In addition, it is assumed that the distribution transformers have on-load tap changers and can automatically control the voltage to prevent voltage rise in the feeder. The main objectives of the discussed methods are to regulate the voltage profiles and reduce the voltage unbalance. MATLAB-based simulation results demonstrate effectiveness of the discussed approaches

Time-Series Analysis of Photovoltaic Distributed Generation Impacts on a Local Distributed Network

Increasing penetration level of photovoltaic (PV) distributed generation (DG) into distribution networks will have many impacts on nominal circuit operating conditions including voltage quality and reverse power flow issues. In U.S. most studies on PVDG impacts on distribution networks are performed for west coast and central states. The objective of this paper is to study the impacts of PVDG integration on local distribution network based on real-world settings for network parameters and time-series analysis. PVDG penetration level is considered to find the hosting capacity of the network without having major issues in terms of voltage quality and reverse power flow. Time-series analyses show that distributed installation of PVDGs on commercial buses has the maximum network energy loss reduction and larger penetration ratios for them. Additionally, the penetration ratio thresholds for which there will be no power quality and reverse power flow issues and optimal allocation of PVDG and penetration levels are identified for different installation scenarios.Comment: To be published (Accepted) in: 12th IEEE PES PowerTech Conference, Manchester, UK, 201

Effects of large-scale PV self-consumption on the aggregated consumption

Self-consumption is modifying the classical structure of the electrical grids worldwide. This energy supply method allows a distributed energy generation and the possibility of involving citizens in the electrical grid. Many countries have defined or are defining rules regarding self-consumption because of the evidence of its unstoppable growth. From the technical point of view, there are numerous associated advantages to the self-consumption, nevertheless it represents a new challenge in the management and design of the electrical grids. In general, the main generation technology for self-consumption is the PV energy. The PV generators are installed in a facility and their generation can be considered as a reduction on the local consumption or even negative consumption. Therefore, high penetration of PV self-consumption will modify the aggregated consumption shape of the electrical grid. The electrical grid should be able to respond to this new shape by adapting generation, controlling consumption or using storage systems. In this paper, we analyze the effects of high penetration of PV self-consumption on the aggregated consumption of the Spanish electrical grid. For this analysis we use historical solar resource data from different cities of Spain and historical data of the aggregated consumption of the country. The results show that PV self-consumption can smooth the aggregated consumption shape, mainly during summer periods. On the other hand, the PV self-consumption can increase the variability of the aggregated consumption shape for high penetration levels

EFFECTS OF CONNECTING A SCATTERED SOLAR GENERATION UNIT TO THE GRID ON THE CLOUD PASSAGE USING OPTIMIZATION ALGORITHMS

Today, limitation of fossil fuel resources and other issues such as the possibility of the depletion of fossil energy reserves, global warming, environmental pollution, price instability, and the growing need for industrial and urban centers for energy have prompted the international community to seek appropriate alternatives. Such examples are nuclear energy, solar energy, geothermal energy, wind energy, and ocean waves. Renewable energy is generated owing to the simplicity of the applied technology compared to nuclear energy technologies. On the other hand, such energies play a key role in new energy systems in the world similar to nuclear waste. The increasing use of renewable energies has given rise to significant complications. One of the main operational issues in this regard is the uncertainty of electricity generation by solar power plants, which is caused by the passage of clouds. The present study aimed to investigate the effects of cloud passage on the production of solar power plants. Initially, a control system was designed to control a high-penetration solar power plant in the network, and the maximum allowable percentage of penetration was calculated for different loads. For this purpose, three algorithms (DE, PSO, and ICA) were used to determine the MPPT of the solar arrays in shady conditions, as well as the MPPT point of the solar arrays. According to the results, the colonial competition algorithm was faster compared to the other algorithms

Artificial intelligence-based protection for smart grids

Lately, adequate protection strategies need to be developed when Microgrids (MGs) are connected to smart grids to prevent undesirable tripping. Conventional relay settings need to be adapted to changes in Distributed Generator (DG) penetrations or grid reconfigurations, which is a complicated task that can be solved efficiently using Artificial Intelligence (AI)-based protection. This paper compares and validates the difference between conventional protection (overcurrent and differential) strategies and a new strategy based on Artificial Neural Networks (ANNs), which have been shown as adequate protection, especially with reconfigurable smart grids. In addition, the limitations of the conventional protections are discussed. The AI protection is employed through the communication between all Protective Devices (PDs) in the grid, and a backup strategy that employs the communication among the PDs in the same line. This paper goes a step further to validate the protection strategies based on simulations using the MATLABTM platform and experimental results using a scaled grid. The AI-based protection method gave the best solution as it can be adapted for different grids with high accuracy and faster response than conventional protection, and without the need to change the protection settings. The scaled grid was designed for the smart grid to advocate the behavior of the protection strategies experimentally for both conventional and AI-based protections.This work is supported by Li Dak Sum Innovation Fellowship Funding (E06211200006) from the University of Nottingham Ningbo China.Peer ReviewedPostprint (published version

A comparative study of smart THD-based fault protection techniques for distribution networks

The integration of Distributed Generators (DGs) into distribution systems (DSs) leads to more reliable and efficient power delivery for customers. However, the possibility of bi-directional power flow creates new technical problems for protection schemes. This poses a threat to conventional strategies because the relay settings have to be adjusted depending on the network topology and operational mode. As a solution, it is important to develop novel fault protection techniques to ensure reliable protection and avoid unnecessary tripping. In this regard, Total Harmonic Distortion (THD) can be used as a key parameter for evaluating the grid’s waveform quality during fault events. This paper presents a comparison between two DS protection strategies that employ THD levels, estimated amplitude voltages, and zero-sequence components as instantaneous indicators during the faults that function as a kind of fault sensor to detect, identify, and isolate faults. The first method uses a Multiple Second Order Generalized Integrator (MSOGI) to obtain the estimated variables, whereas the second method uses a single SOGI for the same purpose (SOGI-THD). Both methods rely on communication lines between protective devices (PDs) to facilitate coordinated protection. The effectiveness of these methods is assessed by using simulations in MATLAB/Simulink considering various factors such as different types of faults and DG penetrations, different fault resistances and fault locations in the proposed network. Moreover, the performance of these methods is compared with conventional overcurrent and differential protections. The results show that the SOGI-THD method is highly effective in detecting and isolating faults with a time interval of 6–8.5 ms using only three SOGIs while requiring only 447 processor cycles for execution. In comparison to other protection methods, the SOGI-THD method exhibits a faster response time and a lower computational burden. Furthermore, the SOGI-THD method is robust to harmonic distortion, as it considers pre-existing harmonic content before the fault and avoids interference with the fault detection process.Peer ReviewedPostprint (published version