Technical and Economic Integration of Voltage Source Converter Based High Voltage Direct Current Transmission in Power Systems

New challenges face the electrical system every day. These new challenges may need to be addressed with more than just conventional AC solutions. Voltage Source Converter based High Voltage DC (VSC-HVDC) systems, although unconventional, may provide promising solutions to these challenges, but integration of these advanced devices into normal power system planning and operation continues to be slow. This research seeks to improve integration of VSC-HVDC into power system planning and operations by addressing both the technical and economic hurdles to integration. First, a ranking algorithm of prioritizing the incorporation of a VSC-based HVDC transmission line for improved economic dispatch is presented. This algorithm, termed as Smart Targeted Planning (STP), proposes a line shadow price-based weighting approach to ranking the potential economic impact of incorporating a new VSC-based HVDC link along existing transmission lines. This work allows for improved integration of VSC-HVDC in the planning stages. Second, a singular value sensitivity (SVS) based supplementary control algorithm is proposed for enhancing the quasi-steady-state voltage stability in AC power systems. The algorithm computes the optimal control policy for VSC power so that the system voltage stability margin is maintained. Also introduced is the singular value capability space of the embedded VSC-HVDC system which builds intuition for system operators to visualize how much the embedded VSC-HVDC system can migrate the system away from voltage instability. Third, a novel control algorithm is proposed for power system small signal dynamic performance improvement by use of an embedded voltage source converter (VSC) based high voltage direct current (HVDC) system. Embedded HVDC refers to a meshed AC grid with all HVDC terminals connected within the same AC grid. The concept of steady-state and dynamic impedance of the HVDC system is introduced as a novel time-scale separation of the impact of HVDC on the AC grid. In this system, the impedance of the connecting transmission lines is the same in the dynamic model as that in the steady-state model. The proposed control will have the VSC-HVDC mimic impedance in the dynamic model while not affecting the steady-state model. This allows the VSC-HVDC system to target improvement for dynamic problems while maintaining independence to use a different control to improve steady-state problems. To obtain optimal parameters for the enhanced small signal impedance mimicry (ESSIM) control, a sensitivity based optimal control loop is also proposed. The efficacy of the proposed algorithm is shown via case studies on a classic two area system and on the IEEE 10 generator 39 bus system. Finally, a multi-time scale techno-economic benefit mapping framework is proposed to aid in better economic integration of advanced transmission devices like VSC-HVDC. The proposed approach is to clearly map technical benefits to their corresponding economic causes and economic effects. The end result will be a scalar metric by which all devices can be compared. The proposed approach will address multi-time scale technical benefits and the resulting economic causes and effects providing clarity, transparency, and granularity to allow for a better one-to-one comparison of conventional and unconventional power system devices

Cost-Optimal Operational Security in Transmission Grids with Embedded HVDC Systems and Energy Storage

The future transmission grid for electrical power will face challenges on an unprecedented scale as the transformation of the energy system progresses. The massive integration of renewable energy sources will require new methods and additional equipment to maintain the system secure and cost-efficient. This doctoral thesis presents an approach to securely operate a transmission grid based on optimal power flow. Optimal control of phase shifting transformers, overlaying HVDC grids and large-scale energy storage lead to reduced operating costs. Furthermore, this work discusses efficient approaches to optimally coordinate multiple inter-connected control areas, if one central controller is undesirable for political or technical reasons

Optimal Planning and Operation of AC-DC Hybrid Distribution Systems

Recent years have been marked by a significant increase in interest in green technologies, which have led to radical changes in the way electric power is generated and utilized. These changes have been accompanied by greater utilization of DC-based distributed generators (DGs), such as photovoltaic (PV) panels and fuel cells, as well as DC-based load demands, such as electric vehicles (EVs) and modern electronic loads. In addition to accommodating these technologies, future distribution systems (DSs) will also need to support the integration of additional battery storage systems with renewable DGs. A further factor is the number of policies that have been implemented in Ontario, Canada, with the goal of encouraging the use of clean energy. The first, the feed-in-tariff (FIT) program, was introduced to promote the application of renewable DGs, including PV panels and wind DGs, and a second, new program that offers incentives for switching to EVs has been announced recently. The result is that future DSs must include additional DC loads and DC-based DGs along with their present AC loads and energy resources. Future DSs should thus become AC-DC hybrids if they are to provide optimal accommodation of all types of AC and DC loads and DGs. These considerations accentuate the need for reliable techniques appropriate for the planning and operation of future hybrid DSs. This thesis presents new directions for the planning and operation of AC-DC hybrid DSs. The main target of the research presented in this thesis is to optimally accommodate the expected high penetration of DC loads and DC-based DGs in future DSs. Achieving this target entailed the completion of four consecutive parts: 1) developing a unified load flow (LF) model for AC-DC hybrid DSs, 2) introducing an energy management scheme (EMS) for the optimal operation of AC-DC hybrid DSs, 3) introducing a planning model to determine the optimal AC-DC network configuration that minimizes the costs of the hybrid DS, and 4) developing a reliability-based planning technique for the simultaneous optimization of the DS costs and reliability. The first part of this research introduces a novel unified LF model for AC-DC hybrid DSs. The LF model can be applied in hybrid DSs with a variety of configurations for AC/DC buses and AC/DC lines. A new classification of DS buses is introduced for LF analysis. Three binary matrices, which are used as a means of describing the configuration of the AC and DC buses and lines, have been employed in the construction of the unified power equations. The LF model is generic and can be used for both grid-connected and isolated hybrid DSs. The new model has been tested using several case studies of hybrid DSs that include different operational modes for the AC and DC DGs. The effectiveness and accuracy of the developed LF model has been verified against the steady-state solution produced by PSCAD/EMTDC software. The second part presents a two-stage EMS that can achieve optimal and reliable operation for AC-DC hybrid DSs. The first stage introduces a network reconfiguration algorithm to determine the optimal day-ahead reconfiguration schedule for a hybrid DS, while considering the forecasted data for load demands and renewable DGs. The objective of the reconfiguration algorithm is the minimization of DS energy losses. The second stage introduces a real-time optimal power flow (OPF) algorithm that minimizes the DS operation costs. In addition, a load-curtailment-management (LCM) technique is integrated with the OPF algorithm in order to guarantee optimal and reliable DS operation in the case of abnormal operating conditions. The third part presents a novel stochastic planning model for AC-DC hybrid DSs. Taking into account the possibility of each line/bus being AC or DC, the model finds the optimal AC-DC hybrid configuration of buses and lines in the DS. It incorporates consideration of the stochastic behavior of load demands and renewable DGs. The stochastic variations are addressed using a Monte-Carlo simulation (MCS). The objective of the planning model is the minimization of DS investment and operation costs. The developed planning model has been employed for finding the optimal configuration for a suggested case study that included PV panels, wind DGs, and EV charging stations. The same case study was also solved using a traditional AC planning technique in order to evaluate the effectiveness of the hybrid planning model and the associated cost-savings. The last part of this research introduces a stochastic multi-objective optimization model for the planning of AC-DC hybrid DSs. The introduced model determines the optimal AC-DC network configuration that achieves two objectives: 1) minimizing system costs, and 2) maximizing system reliability. Network buses and lines can become either AC or DC in order to achieve the planning objectives. The model features an MCS technique for addressing stochastic variations related to load demands and renewable DGs. The developed model has been tested using a case study involving a hybrid DS that included a variety of types of loads and DGs. Solving the same case study using a traditional AC planning technique provided verification of the benefits offered by the developed model, whose efficacy was confirmed through a comparison of the AC and hybrid Pareto fronts. The developed planning framework represents an effective technique that can be used by DS operators to identify the optimal AC-DC network configuration of future hybrid DSs

Maintenance Management of Wind Turbines

“Maintenance Management of Wind Turbines” considers the main concepts and the state-of-the-art, as well as advances and case studies on this topic. Maintenance is a critical variable in industry in order to reach competitiveness. It is the most important variable, together with operations, in the wind energy industry. Therefore, the correct management of corrective, predictive and preventive politics in any wind turbine is required. The content also considers original research works that focus on content that is complementary to other sub-disciplines, such as economics, finance, marketing, decision and risk analysis, engineering, etc., in the maintenance management of wind turbines. This book focuses on real case studies. These case studies concern topics such as failure detection and diagnosis, fault trees and subdisciplines (e.g., FMECA, FMEA, etc.) Most of them link these topics with financial, schedule, resources, downtimes, etc., in order to increase productivity, profitability, maintainability, reliability, safety, availability, and reduce costs and downtime, etc., in a wind turbine. Advances in mathematics, models, computational techniques, dynamic analysis, etc., are employed in analytics in maintenance management in this book. Finally, the book considers computational techniques, dynamic analysis, probabilistic methods, and mathematical optimization techniques that are expertly blended to support the analysis of multi-criteria decision-making problems with defined constraints and requirements

Photovoltaic and Wind Energy Conversion Systems

In the first decades of the current millennium, the contribution of photovoltaic and wind energy systems to power generation capacity has grown extraordinarily all around the world; in some countries, these systems have become two of the most relevant sources to meet the needs of energy supply. This Special Issue deals with all aspects of the development, implementation, and exploitation of systems and installations that operate with both sources of energy

Power Electronics Applications in Renewable Energy Systems

The renewable generation system is currently experiencing rapid growth in various power grids. The stability and dynamic response issues of power grids are receiving attention due to the increase in power electronics-based renewable energy. The main focus of this Special Issue is to provide solutions for power system planning and operation. Power electronics-based devices can offer new ancillary services to several industrial sectors. In order to fully include the capability of power conversion systems in the network integration of renewable generators, several studies should be carried out, including detailed studies of switching circuits, and comprehensive operating strategies for numerous devices, consisting of large-scale renewable generation clusters

Renewable Energy

Renewable Energy is energy generated from natural resources - such as sunlight, wind, rain, tides and geothermal heat - which are naturally replenished. In 2008, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood burning. Hydroelectricity was the next largest renewable source, providing 3% (15% of global electricity generation), followed by solar hot water/heating, which contributed with 1.3%. Modern technologies, such as geothermal energy, wind power, solar power, and ocean energy together provided some 0.8% of final energy consumption. The book provides a forum for dissemination and exchange of up - to - date scientific information on theoretical, generic and applied areas of knowledge. The topics deal with new devices and circuits for energy systems, photovoltaic and solar thermal, wind energy systems, tidal and wave energy, fuel cell systems, bio energy and geo-energy, sustainable energy resources and systems, energy storage systems, energy market management and economics, off-grid isolated energy systems, energy in transportation systems, energy resources for portable electronics, intelligent energy power transmission, distribution and inter - connectors, energy efficient utilization, environmental issues, energy harvesting, nanotechnology in energy, policy issues on renewable energy, building design, power electronics in energy conversion, new materials for energy resources, and RF and magnetic field energy devices

Use, Operation and Maintenance of Renewable Energy Systems:Experiences and Future Approaches

The aim of this book is to put the reader in contact with real experiences, current and future trends in the context of the use, exploitation and maintenance of renewable energy systems around the world. Today the constant increase of production plants of renewable energy is guided by important social, economical, environmental and technical considerations. The substitution of traditional methods of energy production is a challenge in the current context. New strategies of exploitation, new uses of energy and new maintenance procedures are emerging naturally as isolated actions for solving the integration of these new aspects in the current systems of energy production. This book puts together different experiences in order to be a valuable instrument of reference to take into account when a system of renewable energy production is in operation