EcoBlock: Grid Impacts, Scaling, and Resilience

Widespread deployment of EcoBlocks has the potential to transform today's electricity system into one that is more resilient, flexible, efficient and sustainable. In this vision, the system will consist of self- su cient, renewable-powered, block-scale entities that can deliberately adjust their net power exchange and can optimize performance, maintain stability, support each other, or disconnect entirely from the grid as needed. This report is intended as an independent analysis of the potential relationships, both constructive and adverse, between EcoBlocks and the grid

Analysis of Large Scale PV Systems with Energy Storage to a Utility Grid

With electric distribution network operators experiencing an exponential increase in distributed energy resource connections to the power grid, operational challenges arise attributable to the traditional methods of building distribution feeders. Photovoltaic (PV) solar systems are the major contributor due to recent technological advancements. Though this renewable energy resource is beneficial to human society, unfavorable electrical conditions can arise from the inherit variability of solar energy. Extreme variability of power injection can force excessive operations of voltage regulation equipment and potentially degrade customer voltage quality. If managed and controlled properly, battery energy storage systems installed on a distribution feeder have the ability to compliment solar generation and dampen the negative effects of solar generation. Now that customers are connecting their own generation, the traditional design assumption of load flowing from substation to customer is nullified. This research aims first to capture the maximum amount of generation that can be connected to a distribution feeder. Numerous deployments of generation scenarios are applied on six unique distribution feeders to conclude that hosting capacity is dependent on interconnect location. Then, existing controllers installed on voltage regulation equipment are modeled in detail. High resolution time series analysis driven from historical measurements is conducted on two contrasting feeders with specific PV generator deployments. With the proper modeling of on-load tap changer controls, excessive operations caused by extreme PV generation swings were captured. Several services that battery energy storage systems can provide when connected to an individual distribution feeder with significant PV generation include long term absorption of excessive PV generation, dynamic response to extreme PV generation ramping, and release of stored energy for system peak shaving. A centralized master energy coordinator is proposed with the ability to dispatch the battery system in such a fashion to implement each service throughout consecutive days of operation. This solution was built by integrating load and solar energy forecasting predictions in order to construct an optimum charging and discharging schedule that would maximize the asset’s lifespan. Multiple load and solar generation scenarios including a consecutive three day run is included to verify the robustness of this energy coordinator

Value Proposition of Battery Energy Storage Systems on Electric Distribution Systems in Regulated Environments

The electric power grid will be facing new challenges in the coming years. One recent trend has been more efficient electrical devices throughout the world, stagnating load growth. In addition, the historic model of generating electric power using slow, large, centralized power plants is beginning to disappear as distributed generation (DG) becomes cheaper and more accessible, both to power utility companies and customers. The combination of these two changes results in a changing load profile that is difficult for traditional generation sources to follow. Finally, the growth of electric vehicles (EVs) will continue to exacerbate this issue. On the distribution level, these shifts in load profiles result in accelerated equipment aging and equipment upgrade requirements. In order to reduce equipment costs, this thesis surveys 4 distribution feeders from a local southeast utility, forecasting changes possible in the next five years, and calculates the value proposition of using battery energy storage systems (BESS) to mitigate issues caused by the changing demand load profiles. Siemens PTI’s PSS SINCAL’s functionality to achieve this goal is reviewed. It was found that some distribution feeders have high capacity equipment that would not require any modifications to withstand significant future changes. For the one feeder that does, a BESS had a lower value proposition than upgrading overloaded distribution equipment when using approximate equipment costs

Distributed resource integration analysis and network design of electric power distribution systems

The integration of high percentages of distributed energy resources and controllable loads into the distribution system coupled with the strict power quality and service reliability requirements at the power distribution level are necessitating a significant change in the planning, operation and control of the traditional power distribution system. The future power distribution circuits should be able to accommodate the new technologies while simultaneously providing a desired level of power quality and service reliability to the customers. This thesis aims to address the current and future grid requirements of both existing as well as new distribution systems with regard to power quality and service reliability issues. Several methods are proposed to evaluate and mitigate power quality and service reliability concerns due to the integration of smart grid technologies into both existing and new distribution circuits. Notably, for the existing distribution circuits, integration studies are simulated to analyze and mitigate the impacts of electric vehicle loads and photovoltaic generation on the distribution voltages. Furthermore, the problem of siting, sizing and deployment of distributed energy storage systems in meeting distribution planning requirements with regard to integrating distributed generation and providing contingency requirements is also addressed. A new distribution system both grid-connected and operating in islanded mode, however, could be designed to the new requirements. The new distribution circuit could be designed to meet the power quality and service reliability standards directly, thus more efficiently mitigating the concerns. In the thesis, the new distribution circuit design is approached from the perspective of maximizing the service reliability. For the new distribution circuit, approaches to reliability based distribution circuit design are proposed.Electrical and Computer Engineerin

Impact assessment of high penetration of rooftop PV in municipal electrical networks

Thesis (MEng (Electrical Engineering))--Cape Peninsula University of Technology, 2019There is an increasing global trend of grid connected distributed generation, mainly based on renewable energy sources such as wind and photovoltaic (PV) systems. The proliferation of these intermittent energy sources into the existing networks may subject the network into technical challenges such as voltage rise, equipment over-load, power quality and protection scheme violations. With increased PVDG (mainly rooftop PV) uptake occurring mostly on Low Voltage (LV) feeders, characterised by lack of network visibility and controllability, these technical challenges may be exac-erbated. In the absence of government incentive, current uptake of rooftop PVDG is reliant on customer preference and financial means. Thus make PVDG integration on the network be randomly placed and sized, of which the network distribution operator (NDO) will have no control over. The lack of regulations and interconnection studies conducted on South African networks has resulted in a growing concern amongst util-ities on how the increasing customer-owned rooftop PV systems uptake will impact the existing networks. This study aims to investigate technical impact high penetration of rooftop PV sys-tem will have on the existing LV networks. The load flow (LF) computation is pivotal in determining power system state when subjected to high penetration of rooftop PV. Monte-Carlo based Probabilistic Load Flow (PLF) was proposed and input variables were modelled using Beta probabilistic distribution function (PDF). The proposed im-pact assessment framework was applied on real LV urban residential network situated in Cape Town, South Africa. Simulations were conducted on DIgSILENT PowerFac-tory and the PDF for input variables (Load demand and PV generation) were derived from historic data. Four scenarios were simulated and system performance parameters were recorded such as; voltage magnitude, voltage unbalance factor and equipment thermal loading. Simulation results in the test network indicated thermal loading violation as the main limiting factor in urban residential network. PV system topology (either three-phase or single phase) proved to have significant effect on network hosting capacity, were higher PV penetration can be achieved for a three-phase system. Penetration level as low as 12% were recorded, which is significantly lower than the prescribed guidelines in simplified criteria in NRS097-2-3 standard and therefore raises a concern on the relevance of this standard on all types of networks (in urban network in particu-lar). However, penetration level above NRS097-2-3 limits may be achieved depending on feeder characteristics

A deterministic method of distributed generation hosting capacity calculation: case study of underground distribution grid in Morocco

Global warming has become a significant concern over the past decades. As a result, governments have shifted their policies toward renewable energy sources and environmentally friendly industries. This approach requires a renewal of the electrical networks to accommodate this new intermittent generation (from solar and wind sources) while remaining stable and reliable. In this vision, the notion of hosting capacity has been introduced to define the amount of new distributed generation that an electrical network can host without affecting its stability and reliability. This study proposes a deterministic method based on the π model of cables to estimate the underground feeder's hosting capacity. This method considers reverse power flow, overvoltage, reconfiguration, overloading, and the physical characteristics of lines. It is applied to the Moroccan medium voltage underground radial feeder. Through DIgSILENT power factory software, the power flow analysis is carried out to validate its effectiveness in overcoming overvoltage and cable overload problems. The results validate the relevance of our method, its reliability, its fluidity of application, and its ability to maintain performance indices within the acceptable range

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15