Showing papers on "Base load power plant published in 2015"

Thermal Loading and Lifetime Estimation for Power Device Considering Mission Profiles in Wind Power Converter

Abstract: As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial for the reliability improvement and also for cost reduction of wind power technology. Unfortunately, the existing lifetime estimation methods for the power electronic converter are not yet suitable in the wind power application, because the comprehensive mission profiles are not well specified and included. Consequently, a relative more advanced approach is proposed in this paper, which is based on the loading and strength analysis of devices and takes into account different time constants of the thermal behaviors in power converter. With the established methods for loading and lifetime estimation for power devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles.

Optimizing Storage Siting, Sizing, and Technology Portfolios in Transmission-Constrained Networks

Abstract: In this paper, we propose a DC optimal power flow (OPF) framework for storage portfolio optimization in transmission-constrained power networks In particular, this model is designed to investigate two problems: 1) optimizing storage operation and allocation over a network given a fixed technology portfolio and 2) optimizing the storage portfolio (ie, the size, technology, and network allocation of these resources) We demonstrate this framework using case studies based on the IEEE 14-bus test system with four different storage technologies Our results show that although certain technologies are generally classified as being suitable for either power or energy services, many technologies can add value to the system by performing both fast-time scale regulation (power) and load-shifting (energy) services These results suggest that limiting the type of service that a certain technology is compensated for may result in inefficiencies at the system level and under-valuation of storage

Optimal ESS Allocation for Load Management Application

Abstract: The recent deployment of distributed generation has led to a revolution in the use of distribution systems and the emergence of “smart grid” concepts. Smart grids are intended primarily as a means of facilitating the integration of renewable energy sources and of achieving greater system reliability and efficiency. Energy storage systems (ESSs) offer a number of benefits that can help utilities move toward those goals. One of those benefits is the capacity to improve the utilization of network infrastructure by means of proper load management. This paper proposes a methodology for allocating ESSs in distribution systems in order to defer system upgrades, minimize system losses, and take advantage of the arbitrage benefit. The cost and arbitrage benefit of energy storage installation are optimized with respect to system upgrade and energy losses costs. The primary goal of this research is to determine the optimal size and location of storage units to be installed, in addition to their optimal operation, so that total system costs are minimized, while system benefits are maximized. In this paper, a probabilistic load model is adopted instead of utilizing time-series based models, which provide an optimal solution that is valid only for the time-series pattern that is applied.

A Novel Demand Response Model with an Application for a Virtual Power Plant

Abstract: In modern power systems and electricity markets, demand response (DR) programs play an important role enabling the mitigation of critical load periods or price-peaking scenarios, thereby improving system reliability. Price fluctuations, in forward or real-time markets, can be an effective price-based DR mechanism for curtailing or shifting load. However, using dynamic pricing to achieve a desired load profile requires both an accurate demand forecast and knowledge of the price elasticity of demand, which is notoriously difficult to estimate. The limited accuracy of these parameter estimates is the main source of uncertainty limiting appropriate DR implementation. In this paper, we present a novel DR scheme that avoids the need to predict the price elasticity of demand or demand forecast, yet still delivers a significant DR. This is done based on the consumers' submissions of candidate load profiles ranked in the preference order. The load aggregator then performs the final selection of individual load profiles subject to the total system cost minimization. Additionally, the proposed DR model incorporates a fair billing mechanism that is enhanced with an ex post consumer performance tracking scheme implemented in a context of a virtual power plant aggregating load and generation units.

Pushing the Limits: Europe's New Grid: Innovative Tools to Combat Transmission Bottlenecks and Reduced Inertia

Abstract: In the future a growing amount of power electronics will lead to a transition of the power system to a structure with very low synchronous generation. Due to large transit power flows and uncertainties, transmission systems are being operated under increasingly stressed conditions and are close to their stability limits. Together with the integration of large amounts of renewable generation with power electronic interfaces and the addition of high-voltage direct current (HVdc) links into the power system, these challenges will necessitate a review of the operation and control of transmission networks. This article will demonstrate the need for R&D performed by network operators and explain a set of challenges, focusing on three main areas: transmission grid operation in a new power system environment, the need to increase overhead line (OHL) utilization, and the impact of reduced inertia on power system frequency.

Evaluating CO2 sources for power-to-gas applications – A case study for Austria

Abstract: The intermittent nature of wind and solar power requires long-term energy storage options such as power-to-gas. This technology utilizes (surplus) electricity from renewable power sources to produce hydrogen in an electrolyzer. The produced hydrogen can be either directly utilized as an energy carrier or combined with CO2 and further converted to methane. This article evaluates different CO2 sources concerning their potential utilization within the power-to-gas energy storage technology with regard to capture costs, specific energy requirement and CO2 penalties. The results of a case study for Austria indicate that there is enough CO2 available from point sources to store all of the electricity produced from fluctuating renewable power sources (wind power plants and photovoltaics) via power-to-gas. Due to low capture costs, low CO2 penalties, biogenic origins, and short distances to wind power plants, biogas upgrading facilities and a bioethanol plant were determined to be the CO2 sources best suited for utilization in novel power-to-gas plants. However, as the total amount of CO2 produced from these facilities is relatively low in Austria, other CO2 sources would also be required. With moderate capture costs and CO2 penalties, power plants and an existing refinery could also provide CO2 for power-to-gas. Although large amounts of CO2 are available from iron, steel, and cement production facilities, these sources are not recommended for CO2 utilization in power-to-gas, as the CO2 penalty is relatively high and the facilities are rarely located near wind power plants in Austria.

Joint Energy and Spinning Reserve Market Clearing Incorporating Wind Power and Load Forecast Uncertainties

Abstract: This paper proposes an energy and spinning reserve market clearing (ESRMC) mechanism for wind–thermal power system, considering uncertainties in wind power and load forecasts. Two different market models for the ESRMC are proposed. One model includes reserve offers from the conventional thermal generators, and the other includes reserve offers from both thermal generators and demand/consumers. The stochastic behavior of wind speed and wind power is represented by the Weibull probability density function (pdf), and that of the load is represented by a normal pdf. This paper considers two objectives: total cost minimization and the system-risk-level minimization. The first objective includes the cost of energy provided by thermal and wind generators, and the cost of reserves provided by thermal generators and loads. It also includes costs due to overestimation and underestimation of available wind power and load demand. The system risk level is considered as another objective as wind power is highly uncertain. Multiobjective Strength Pareto Evolutionary Algorithm 2+ (SPEA 2+) has been used to solve the ESRMC problem. The results of the IEEE 30 bus system demonstrate the utility of the proposed approach.

Dynamic Reactive Power Compensation of Large-Scale Wind Integrated Power System

Abstract: Due to progressive displacement of conventional power plants by wind turbines, dynamic security of large-scale wind integrated power systems is significantly compromised. In this paper we first highlight the importance of dynamic reactive power support/voltage security in large-scale wind integrated power systems with least presence of conventional power plants. Then we propose a mixed integer dynamic optimization based method for optimal dynamic reactive power allocation in large-scale wind integrated power systems. One of the important aspect of the proposed methodology is that unlike static optimal power flow based approaches, the proposed method considers detailed system dynamics and wind turbine grid code compliance while optimizing the allocation of dynamic reactive power sources. We also advocate that in large-scale wind integrated power systems, 1) better utilization of existing wind turbines especially wind farms with additional grid support functionalities like dynamic support (e.g., dynamic reactive power support, etc.) and 2) refurbishment of existing conventional central power plants to synchronous condensers could be one of the efficient, reliable and cost-effective option to address not only the issue of dynamic voltage security but also to strengthen other dynamic capabilities of the system including system inertia, etc. that are also significant challenges in large-scale wind penetrated power system. The proposed methodology is applied to the detailed model of the western Danish power system which is characterized by large-scale wind integration and least presence of central power plants.

Wind Power Curtailment and Energy Storage in Transmission Congestion Management Considering Power Plants Ramp Rates

Abstract: The integration of intermittent generation in power grids, such as wind energy, imposes new challenges for transmission congestion management In order to solve this problem, energy storage systems (ESS) have been proposed in the literature, as they provide an efficient mechanism for balancing variability while reducing operational costs This paper presents a comprehensive analysis of the dynamic interactions between wind energy curtailment and an energy storage system (ESS) when the ramping rates of power plants are considered An analytical framework is developed to study different mitigation measures in terms of total energy curtailed, total congestion costs, line load factor and congestion probability This framework is tested in a real case study and a sensitivity analysis is performed to identify the influence of the main ESS design parameters in congestion mitigation performance

Chance-Constrained Transmission Switching With Guaranteed Wind Power Utilization

Abstract: Due to the significant variability and uncertainty of wind power over short time scales, high penetration of wind power can be problematic in an electric grid. One of the critical issues is how to keep increasing wind penetration without jeopardizing grid security and reliability. This paper explores the possibility of changing transmission network topology, by transmission switching, to accommodate higher utilization of wind power and reduce the generation costs of thermal units. Considering the uncertainty in wind power output, we use chance constraints to ensure that the wind energy utilized exceeds a minimal usage level at a certain probability. We develop a deterministic approximation approach using sample average approximation and provide a strong extended formulation. Numerical results show the potential benefit the proposed model can achieve.

Reducing Generation Uncertainty by Integrating CSP With Wind Power: An Adaptive Robust Optimization-Based Analysis

Abstract: The uncertainty of wind power generation brings problems in power system operation, such as requiring more reserves and possible frequency issues. In this paper, we propose an idea of combining concentrating solar power (CSP) plants with wind farms to reduce the overall uncertainty in the joint power output. Taking advantage of the dispatchability of CSP, the uncertainty of joint power generation is expected to decrease. Based on the operational model of CSP plants with thermal storage system, we search for the narrowest but robust bounds of the joint power output with a given uncertainty of the wind power output and solar power availability, and within operational constraints of CSP plants. The problem is formulated as an adaptive robust optimization (RO) problem, containing mixed-integer variables at the second stage. We introduce an algorithm that combines a nested column-and-constraint generation (C-CG) method and an outer approximation (OA) method to solve the problem. The case studies show that robust intervals for the joint power output can be obtained, and the obtained intervals can be significantly narrower than the original intervals of wind power.

A critical review of voltage and reactive power management of wind farms

Abstract: Wind generation is currently the major form of new renewable, generation in the world. The wind power is totally dependent on wind flow, due to randomness and uncertainty of wind flow, the wind power generation is quite fluctuating in nature and large scale wind farms may cause significant impact to the power system safety, quality and stability. The active power mainly depends upon the potential of the wind power produced and wind turbine generator design. The reactive power demand on the other hand depends upon conversion devices and recovered power quality fed to the grid. The wind farms which accesses to power grid cause fluctuations and reactive power redistribution and sometimes lead to voltage collapse. Similarly, the dynamic voltage stability is a major challenge faced by distribution network operators. The easy solution comes into picture is to install reactive power source devices with optimization of the existing assets to deliver enhanced reactive power to the grid. With solution to reliability, voltage regulation, reactive power requirements, grid integration problems, weak grid interconnection, off grid wind power generation and its integration to power grid, wind power penetration in distribution grid, wind power uncertainty, flicker and harmonics etc. The categorization of issue considered the goal of our work is the reactive power management of wind farm in most technical and economical way without compromising quality power system voltage, and considering the wind turbine technology for already commissioned wind farm, and change in WT technology in present scenario. More than 100 research publications on voltage and reactive power control of wind farms, extending from year 2003 to 2013 have been critically examined, classified and listed for quick reference.

An Underfrequency Load Shedding Scheme for Hybrid and Multiarea Power Systems

Abstract: The purpose of underfrequency load shedding (UFLS) is to maintain the frequency of an interconnected or island power system within permissible limits in case of severe power deficits. Thus, the proper performance of UFLS scheme is of great importance. In hybrid power systems, disconnecting and connecting the power generation sources and loads result in variations in the system parameters. Moreover, the output power of some distributed energy resources, such as photovoltaic (PV) or wind turbine generator (WTG), might change during the load shedding process. These factors may affect the performance of the load shedding scheme and decrease the reliability of power system. Hence, in this paper, a UFLS scheme is proposed that has two advantages: 1) it is independent of power system parameters; and 2) it considers power generation variations during the load shedding process. To verify the effectiveness of the proposed load shedding method, simulation studies are carried out on a hybrid power system including PV, WTG, fuel cell, diesel generator, and battery energy storage system. Finally, the performance of the proposed method on a multiarea power system is evaluated.

Smart Metering of Variable Power Loads

Abstract: Nonintrusive load monitoring (NILM) seeks to determine the operation of individual loads in a building strictly from measurements made on an aggregate current signal serving a collection of loads. Great strides have been made in performing NILM for loads whose operating state can be represented by a finite-state machine, i.e., loads that consume discrete or distinct power levels for periods of time. It is much more difficult to track the operation of continuously variable loads that demand ever-changing power. These loads are becoming more prevalent as variable speed drives, daylight-responsive lighting, and other power electronic controlled loads emerge on the grid. This paper demonstrates a method for tracking the power consumption of variable demand loads nonintrusively. The method applies to any site where NILM might be of interest, including commercial and industrial buildings, residences, and transportation systems.

Stochastic reactive power management in microgrids with renewables

Abstract: Distribution microgrids are being challenged by reverse power flows and voltage fluctuations due to renewable generation, demand response, and electric vehicles Advances in photovoltaic (PV) inverters offer new opportunities for reactive power management provided PV owners have the right investment incentives In this context, reactive power compensation is considered here as an ancillary service Accounting for the increasing time-variability of distributed generation and demand, a stochastic reactive power compensation scheme is developed Given uncertain active power injections, an online reactive control scheme is devised This scheme is distribution-free and relies solely on power injection data Reactive injections are updated using the Lagrange multipliers of a second-order cone program Numerical tests on an industrial 47-bus microgrid and the residential IEEE 123-bus feeder corroborate the reactive power management efficiency of the novel stochastic scheme over its deterministic alternative, as well as its capability to track variations in solar generation and household demand

Impact of the Combined Integration of Wind Generation and Small Hydropower Plants on the System Reliability

Abstract: The purpose of this paper is to assess the impact of the integration of wind generation, together with small hydropower plants (SHPs), in the reliability of the power system. In order to preserve the characteristics of the time series of the variable energy sources (wind and river inflows) and the variable load, the analyses are based on the sequential Monte Carlo simulation. By calculating the reliability indices, we intend to evaluate how the uncertainty of wind energy production impacts on system planning, especially with the reduction of capacity of reservoirs associated with SHPs. We also intend to evaluate the existence of complementarity between wind and hydro-generation, or even between different wind generation and/or the load. Finally, we intend to analyze how the correlation between these energy sources can benefit the supply of the future foreseen demand.