Voltage control and stability analysis in a multi-machine power system with increasing penetration of intermittent renewable energy generation.

Masters Degree. University of KwaZulu-Natal, Durban.Among multiple distributed generation (DG) supply means, photovoltaic (PV) and wind technologies are the most important and widely used renewable energy sources (RES) throughout the world. However, solar intermittency and the stochastic nature of radiation on one hand and grid integration-related issues on the other are fundamental concerns in the development and smooth deployment of solar energy contribution to conventional power systems networks. In addition, given that they modify both the structure and the operation of the distribution networks, RES increase uncertainty in power system operations, thus affecting power systems variables such as the voltage profiles and direction of network power flows. It is also largely established that a high penetration of DGs at the distribution end is associated amongst others, with voltage rises at PV buses that may lead to the violation of grid codes, if not adequately mitigated. There is a need to investigate both the effect and the impact of increasing penetration of these intermittent RES on, particularly, voltage and frequency stability power systems and the utilization thereof of such sources to improve voltage stability margins and predict voltage stability conditions. This research work investigated voltage control and stability conditions at Solar PV buses through various case studies and scenarios simulated using the Power Factory® tool, both in static and dynamic analysis modes. A modified standard IEEE 9-Bus Sub-transmission system was used to assess the voltage profile, system loadability and system stability. The comparison and discussion of the results obtained from the integration of the Solar PV and FACTS devices under various scenarios revealed that their respective impacts and abilities to improve voltage stability differ. The results confirmed that under any operating conditions, reactive power control remains the most effective method to control voltage stability and power transfer capability, especially in the context where an increasing penetration of renewable and inertia-less generating sources is planned. The results further revealed that there is a specific location and a specific siting architecture for a given size of PV that produces the best results for voltage stability, as well as improved system stability and loadability conditions for a given load distribution profile in a particular network. Lastly, the results demonstrated the effectiveness of the use of a Battery Energy Storage System (BESS) in achieving voltage control and regulation in distribution networks highly penetrated by PV generation, subsequently enabling greater RE penetration

Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks

In the last decade, distribution systems are experiencing a drastic transformation with the advent of new technologies. In fact, distribution networks are no longer passive systems, considering the current integration rates of new agents such as distributed generation, electrical vehicles and energy storage, which are greatly influencing the way these systems are operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system through power electronics converters, is unlocking the possibility for new distribution topologies based on AC/DC networks. This paper analyzes the evolution of AC distribution systems, the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de Economía y Competitividad ENE2017-84813-RUnión Europea (Programa Horizonte 2020) 76409

Reducing Voltage Volatility with Step Voltage Regulators: A Life-Cycle Cost Analysis of Korean Solar Photovoltaic Distributed Generation

To meet the United Nation’s sustainable development energy goal, the Korean Ministry of Commerce announced they would increase renewable energy generation to 5.3% by 2029. These energy sources are often produced in small-scale power plants located close to the end users, known as distributed generation (DG). The use of DG is an excellent way to reduce greenhouse gases but has also been found to reduce power quality and safety reliability through an increase in voltage volatility. This paper performs a life-cycle cost analysis on the use of step voltage regulators (SVR) to reduce said volatility, simulating the impact they have on existing Korean solar photovoltaic (PV) DG. From the data collected on a Korean Electrical Power Corporation 30 km/8.2 megawatts (MW) feeder system, SVRs were found to increase earnings by one million USD. SVR volatile voltage mitigation increased expected earnings by increasing the estimated allowable PV power generation by 2.7 MW. While this study is based on Korean PV power generation, its findings are applicable to any DG sources worldwide.11Nsciescopu

Distribution System Voltage Management and Optimization for Integration of Renewables and Electric Vehicles: Research Gap Analysis

California is striving to achieve 33% renewable penetration by 2020 in accordance with the state’s Renewable Portfolio Standard (RPS). The behavior of renewable resources and electric vehicles in distribution systems is creating constraints on the penetration of these resources into the distribution system. One such constraint is the ability of present-­‐‑day voltage management methodologies to maintain proper distribution system voltage profiles in the face of higher penetrations of PV and electric vehicle technologies. This white paper describes the research gaps that have been identified in current Volt/VAR Optimization and Control (VVOC) technologies, the emerging technologies which are becoming available for use in VVOC, and the research gaps which exist and must be overcome in order to realize the full promise of these emerging technologies

Voltage Rise Problem in Distribution Networks with Distributed Generation: A Review of Technologies, Impact and Mitigation Approaches

Energy demand has constantly been on the rise due to aggressive industrialization and civilization. This rise in energy demand results in the massive penetration of distributed generation (DG) in the distribution network (DN) which has been a holistic approach to enhance the capacity of distribution networks. However, this has led to a number of issues in the low voltage network, one of which is the voltage rise problem. This happens when generation exceeds demand thereby causing reverse power flow and consequently leading to overvoltage. A number of methods have been discussed in the literature to overcome this challenge ranging from network augmentation to active management of the distribution networks. This paper discusses the issue of voltage rise problem and its impact on distribution networks with high amounts of distributed energy resources (DERs). It presents different DG technologies such as those based on conventional and unconventional resources and other DERs such as battery storage systems and fuel cells. The study provides a comprehensive overview of approaches employed to curtail the issue of voltage increase at the point of common coupling (PCC), which includes strategies based on the network reinforcement methodology and the active distribution network management. A techno-economic comparison is then introduced in the paper to ascertain the similarities and dissimilarities of different mitigation approaches based on the technology involved, ease of deployment, cost implication, and their pros and cons. The paper provides insights into directions for future research in mitigating the impact of voltage rise presented by grid-connected DGs without limiting their increased penetration in the existing power grid