Conventional Generation Units Research Articles

Evaluating Future Power Distribution System Reliability Including Distributed Generation

This paper assesses the impact of conventional and renewable distributed generation (DG) on the reliability of future distribution systems, even when the connection may not be simply radial. The variability of the power output of renewable DGs, such as wind and solar is included. The stochastic nature of the renewable resources and their influence on the reliability of the system are modeled and studied by computing the adequacy transition rate. An integrated Markov model that incorporates the DG adequacy transition rate, DG mechanical failure, and starting and switching probability is proposed and utilized to give accurate results for the DG reliability assessment. The main focus in this paper is conventional generation, solar, and wind DG units. The technique used appears to be applicable to any renewable energy source.

Energy Management in Smart Grids with Electric Vehicles based on Pricing

This paper presents an energy management system for smart grids with electric vehicles based on pricing. Units are modeled as price-elastic units, price-inelastic units and electric vehicles. Prices are negotiated by the price-elastic units and the electric vehicles such that the total cost of all units is minimized while meeting power, energy and mobility constraints. The negotiation is coordinated by a price coordinator which ensures power balance while regarding predictions for the price-inelastic units. Cornerstone of the method is a dual decomposition using the fast gradient method. The method uses distributed computation, ensures privacy of the units and is plug and play capable with respect to the units. Communication and computation can be reduced by constructing a primal feasible suboptimal solution. Simulations for a smart grid of a company with a conventional generation unit, a photovoltaic generation unit and electric vehicles illustrate the effectiveness of the energy management system.

Wind Speed and Wind Power Forecasting using Statistical Models: AutoRegressive Moving Average (ARMA) and Artificial Neural Networks (ANN)

Wind power, i.e., electrical energy produced making use of the wind resource, is being nowadays constantly connected to the electrical system. This has a non-negligible impact, raising issues like network stability and security of the supply. An accurate forecast of the available wind energy for the forthcoming hours is crucial, so that proper planning and scheduling of the conventional generation units can be performed. Also, with the liberalization of the electrical markets worldwide, the wind power forecasting reveals itself critical to assure that the bids are placed with a minimum possible risk. This work addresses the issue of forecasting wind power with two statistical models, the Autoregressive Moving Average and Artificial Neural Networks. The basic theory and the respective application of these models to perform wind power prediction are presented. Furthermore, their forecasting ability is compared in three different case studies. At the end, some conclusions are drawn about the performance of both models regarding its forecasting capabilities when compared with reference models.

Homeostatic Control of Sustainable Energy Grid Applied to Natural Disasters

According to seismologists Chile has yet to face another big earthquake in the very near future, yet the country remains largely unprepared against massive electric power systems brake-down. The problem lies in the centralized electric power systems and the lack of adequate technologies and back-up/emergency power systems for disas- ter recovery. The flaws that are built into the very fabric of the presently centralized power systems were on full display in the February 27th earthquake in Chile. Nowhere it becomes more evident that hugely centralized power generation and distribution systems are extremely vulnerable and ineffective to disruptions from natural disasters, human error or other calamities. The large power networks that once proved very efficient and secure, are now at the center of discussion fueling the need for decentral- ization and the rapid growth of distributed generation (DG). Highly decentralized, diversified and DG-oriented energy matrix is notoriously much better suited to with- stand these disasters. In centralized electric power grids, servicing large metropolitan areas, albeit with some but limited differentiation in service, can only be on or off, so either everyone gets power or no one does. This makes recovering power service in an emergency situation a much more difficult task. On the other hand, decentralized power systems (DPS) reduce the obstacles to disaster preparation and recovery by allowing the focus to shift first to critical infrastructure and then to flow outward to less integrated outlets. A DG-based model for a smart micro-grid based on hybrid electric power systems (HEPS) using both renewable energy technologies (RET) and conventional power generation units is presented. The hybrid energy system may be portable or fixed in one place, highly reliable, easy to assemble, modular, flexible and cost-effective solution, that is ready-to-run and go to where it is needed to supply power in natural disaster.

Transient performance improvement of grid connected hydro system using distributed generation and capacitive energy storage unit

In this paper, distributed generation (DG) consisting of wind turbine generators, aqua electrolyzer, fuel cells, diesel engine generator, and energy storage devices like flywheel energy storage system and battery energy storage system are considered along with conventional hydro power generation with electric governor. The hydro generator is equipped with automatic voltage regulator, IEEE type dual input power system stabilizer like PSS3B and integral controlled automatic generation control (AGC) loop. The different tunable parameters of the power system model are optimized by a novel craziness-based particle swarm optimization with wavelet mutation (CRPSOWM), developed by the authors. While integrating the DG with the hydro power system, improved transient performance is observed. The usage of capacitive energy storage unit in the AGC loop of conventional power generation unit provides further improvement in the transient performance. The proposed CRPSOWM incorporates a wavelet-theory-based mutation operation and offers robust and promising results.

Control of Wind Power Plant for Cooperation with Conventional Power Generation Unit and HVDC Classic Link

This paper focuses on the control of wind power plant equipped with doubly-fed induction generators (DFIG) for its cooperation with conventional generation unit and HVDC classic link. DFIG wind turbine and wind power plant voltage control are presented in detail. Also their influences on power system voltage stability are analyzed. Besides DFIG wind power plant, synchronous generators and monopolar HVDC classic link are also considered. For synchronous generator, conventional controllers are employed: governor, exciter and power system stabilizer (PSS). For the HVDC classic converters, the V-I controllers are applied. In this paper, the capability of DFIG wind power plant to improve power system dynamic behavior is presented. Simulation results show that the DFIG wind power plant and wind turbine voltage control strategy will reinforce the power system voltage stability.

CO2 capture modelling for pulverised coal-fired power plants: A case study of an existing 1 GW ultra-supercritical power plant in Shandong, China

China is building more than 1GW of advanced coal-fired power plants every week. This interdisciplinary study investigates the technical and economic performance of retrofitting a 1000MW ultra supercritical pulverised coal-fired (USCPC) power plant locating at Shandong province in China. An ASPEN simulation model is designed to estimate the energy output penalty at different levels of capture. The retrofitted system consists of the conventional power generation unit, the additional post-combustion unit and other associated extra equipments. The ASPEN simulation results show that the efficiency penalty is approximately 8.6% for a 90% capture rate and 6% for a 50% capture rate in this retrofitting study. In addition, the simulation result of the process model is applied to analyse the value of retrofitting flexibility and the economic-viable chance of retrofitting the underlying project through a real option analysis model. The economic model reveals that the value of retrofitting option in the 1GW USCPC power plant reaches US$76 million and that a 40% economic viable possibility of retrofitting to capture CO2 in its remaining 26years lifetime under the hypothetical baseline scenario. The significant economic benefits of retrofitting an existing USCPC plant to CO2 capture implies the urgency to conduct a detail survey on the retrofitting prospect of Chinese coal-fired power plants and develop a guideline to maintain their retrofitting options open.

Dynamic model for market-based capacity investment decision considering stochastic characteristic of wind power

This paper proposes a decentralized market-based model for long-term capacity investment decisions in a liberalized electricity market with significant wind power generation. In such an environment, investment and construction decisions are based on price signal feedbacks and imperfect foresight of future conditions in electricity market. System dynamics concepts are used to model structural characteristics of power market such as, long-term firms’ behavior and relationships between variables, feedbacks and time delays. For conventional generation units, short-term price feedback for generation dispatching of forward market is implemented as well as long-term price expectation for profitability assessment in capacity investment. For wind power generation, a special framework is proposed in which generation firms are committed depending on the statistical nature of wind power. The method is based on the time series stochastic simulation process for prediction of wind speed using historical and probabilistic data. The auto-correlation nature of wind speed and the correlation with demand fluctuations are modeled appropriately. The Monte Carlo simulation technique is employed to assess the effect of demand growth rate and wind power uncertainties. Such a decision model enables the companies to find out the possible consequences of their different investment decisions. Different regulatory policies and market conditions can also be assessed by ISOs and regulators to check the performance of market rules. A case study is presented exhibiting the effectiveness of the proposed model for capacity expansion of electricity markets in which the market prices and the generation capacities are fluctuating due to uncertainty of wind power generation.

Roadmap of Developing Active and Reactive Power Dispatch and Control System of China Grid Considering Large-Scale Wind Integration

AbstractLarge-scale wind power is integrated into the backbone grid of China increasingly and the penetration of wind power grows higher and higher. In order to eliminate the impacts of wind power on conventional Active and Reactive Power Dispatch and Control (ARPDC) system, it is urgent to modify present system. Firstly, traditional ARPDC system is introduced briefly. Secondly, the basic characteristics of Chinese wind power are analyzed and summarized, including fluctuation, low-predictability, low-controllability, centralized development, long-distance transmission and integration into backbone grid. Thirdly, based on the characteristics of wind power, the framework of the new ARPDC system is proposed. In short, the ultimate goal of the new ARPDC system is that the wind power should play almost the same role as conventional power generation units. Finally, the status quo of the development of ARPDC system suitable for large-scale wind power integration in China is introduced, and the roadmap of developing new ARPDC system is discussed.

A Power System Stabilizer for Variable-Speed Wind Generators

AbstractThis paper focuses on the application of a special controller that can introduce damping to interarea oscillations of electric power systems by modulating the active power output of wind generators and can thus replace power system stabilizers of conventional synchronous generator units. The controller is tested for Doubly Fed Asynchronous Generators, as well as for Full Converter Wind Generators, on a simplified interconnected system and on an autonomous four-generator, two-area system traditionally used for interarea oscillation analysis and is shown to perform efficiently without significant adverse side effects.

Remote area power supply system technologies in Western Australia: New developments in 30 years of slow progress

The escalation of the renewable energy capacity growth rate in remote pastoral Western Australian (WA) off-grid stand-alone power supply (SPS) systems over the last decade was extraordinary. The expansion was encouraged by subsidised renewable energy technologies, enabling components and system installation costs. This research quantifies and explores the changes over time of rated outputs of renewable and conventional energy components, and energy demand in SPS systems in pastoral WA over the last 30 years. This research revealed parallel increases in conventional generation unit output ratings, renewable energy capacity, and energy demand over the past decade. Whilst recent developments are encouraging, there remain many technical, social, economic and regulatory barriers to overcome the small-scale renewable energy SPS system industry in WA. A lack of mandatory standards has resulted in a minority of poor SPS systems and some aggravated owners in regions where reliability and reputation are paramount. After investing many tens of thousands of Australian dollars (AUD) on new capital equipment, minor system integration issues are becoming a frustratingly common cause of system failure for remote SPS system owners.

Impacts of Wind Power on Thermal Generation Unit Commitment and Dispatch

This paper proposes a new simulation method that can fully assess the impacts of large-scale wind power on system operations from cost, reliability, and environmental perspectives. The method uses a time series of observed and predicted 15-min average wind speeds at foreseen onshore- and offshore-wind farm locations. A Unit Commitment and Economic Dispatch (UC-ED) tool is adapted to allow for frequent revisions of conventional generation unit schedules, using information on current wind energy output and forecasts for the next 36 h. This is deemed the most faithful way of simulating actual operations and short-term planning activities for a system with large wind power penetration. The problem formulation includes ramp-rate constraints for generation schedules and for reserve activation, and minimum up-time and down-time of conventional units. Results are shown for a realistic future scenario of the Dutch power system. It is shown that problems such as insufficient regulating and reserve power-which are typically associated with the variability and limited predictability of wind power-can only be assessed in conjunction with the specifics of the conventional generation system that wind power is integrated into. For the thermal system with a large share of combined heat and power (CHP) investigated here, wind power forecasting does not provide significant benefits for optimal unit commitment and dispatch. Minimum load problems do occur, which result in wasted wind in amounts increasing with the wind power installed

06/02182 Techno-economic feasibility of energy supply of remote villages in Palestine by PV-systems, diesel generators and electric grid: Mahmoud, M. M. and Ibrik, 1. H. Renewable and Sustainable Energy Reviews, 2006, 10, (2), 128–138.

The escalation of the renewable energy capacity growth rate in remote pastoral Western Australian (WA) off-grid stand-alone power supply (SPS) systems over the last decade was extraordinary. The expansion was encouraged by subsidised renewable energy technologies, enabling components and system installation costs. This research quantifies and explores the changes over time of rated outputs of renewable and conventional energy components, and energy demand in SPS systems in pastoral WA over the last 30 years. This research revealed parallel increases in conventional generation unit output ratings, renewable energy capacity, and energy demand over the past decade. Whilst recent developments are encouraging, there remain many technical, social, economic and regulatory barriers to overcome the small-scale renewable energy SPS system industry in WA. A lack of mandatory standards has resulted in a minority of poor SPS systems and some aggravated owners in regions where reliability and reputation are paramount. After investing many tens of thousands of Australian dollars (AUD) on new capital equipment, minor system integration issues are becoming a frustratingly common cause of system failure for remote SPS system owners.

Generating Capacity Adequacy Associated With Wind Energy

The wind is a highly variable energy source and behaves far differently than conventional energy sources. This paper presents a methodology for capacity adequacy evaluation of power systems including wind energy. The results and discussions on two representative systems containing both conventional generation units and wind energy conversion systems (WECS) are presented. A Monte Carlo simulation approach is used to conduct the analysis. The hourly wind speeds are simulated using an autoregressive moving average time-series model. A wide range of studies were conducted on two different sized reliability test systems. The studies show that the contribution of a WECS to the reliability performance of a generation system can be quantified and is highly dependent on the wind site conditions. A WECS can make a significant reliability contribution given a reasonably high wind speed. Wind energy independence also has a significant positive impact on the reliability contribution of multiple WECS.

Fundamentals of tree-shaped networks of insulated pipes for hot water and exergy : Lorente, S. et al. Exergy, An International Journal, 2002, 2, (4), 227–236

Cycling of conventional generation units is an important source of operational flexibility in the electricity generation system. Cycling is changing the power output of conventional units by means of ramping and switching (starting up and shutting down). In the literature, a wide range of technical and cost-related cycling parameters can be found. Different studies allocate different cycling parameters to similar generation units. This paper assesses the impact of different cycling parameters allocated to a conventional generation portfolio. Both the technical limitations of power plants and all costs related to cycling are considered. The results presented in this paper follow from a unit commitment model, used for a case study based on the German 2013 system. The conventional generation portfolio has to deliver different residual load time series, corresponding to different levels of renewables penetration. The study shows, under the assumptions made, that although the dynamic limits of some units are reached, the limits of the conventional generation portfolio as a whole are not reached, even if stringent dynamic parameters are assigned to the generation portfolio and a highly variable residual load is imposed to the system. The study shows also the importance of including full cycling costs in the unit commitment scheduling. The cycling cost can be reduced by up to 40% when fully taken into account.

Potential Dynamic Impacts of Wind Turbines on Utility Systems

This paper presents the results of an initial assessment of potential wind power generation dynamic impacts on utility systems from a global utility perspective performed for the Electric Power Research Institute. Dynamic study of minute-to-minute ramping, frequency excursions, and short-term transient stability was performed using the isolated Hawaiian Electric Company (HECO) system as an illustrative example. Potential minute-to-minute ramping requirements imposed on conventional generation units of two interconnected utilities, Kansas Gas and Electric (KG&E) and Public Service Company of Colorado (PSCo) were investigated, using interconnected utility operating criteria.