Rajesh Karki

A simplified wind power generation model for reliability evaluation

Renewable energy sources, especially wind turbine generators, are considered as important generation alternatives in electric power systems due to their nonexhausted nature and benign environmental effects. The fact that wind power penetration continues to increase has motivated a need to develop more widely applicable methodologies for evaluating the actual benefits of adding wind turbines to conventional generating systems. Reliability evaluation of generating systems with wind energy sources is a complex process. It requires an accurate wind speed forecasting technique for the wind farm site. The method requires historical wind speed data collected over many years for the wind farm location to determine the necessary parameters of the wind speed models for the particular site. The evaluation process should also accurately model the intermittent nature of power output from the wind farm. A sequential Monte Carlo simulation or a multistate wind farm representation approach is often used. This paper presents a simplified method for reliability evaluation of power systems with wind power. The development of a common wind speed model applicable to multiple wind farm locations is presented and illustrated with an example. The method is further simplified by determining the minimum multistate representation for a wind farm generation model in reliability evaluation. The paper presents a six-step common wind speed model applicable to multiple geographic locations and adequate for reliability evaluation of power systems containing significant wind penetration. Case studies on a test system are presented using wind data from Canadian geographic locations.

Cost-effective wind energy utilization for reliable power supply

Environmental concerns and fuel cost uncertainties associated with the use of conventional energy sources have resulted in rapid growth of wind energy applications in power generating systems. It is important to assess the actual cost and benefit of utilizing wind energy in a power system. Such assessments require realistic cost/reliability evaluation methods and quantitative indices. This paper presents a simulation technique that generates probabilistic indices that can help determine appropriate wind power penetration in an existing power system from both the reliability and economic aspects.

Reliability/Cost Implications of PV and Wind Energy Utilization in Small Isolated Power Systems

The application of renewable energy in electric power systems is growing rapidly due to enhanced public concerns for adverse environmental impacts and escalation in energy costs associated with the use of conventional energy sources. Photovoltaics and wind energy sources are being increasingly recognized as cost-effective generation sources in small isolated power systems primarily supplied by costly diesel fuel. The utilization of these energy sources can significantly reduce the system fuel costs but can also have considerable impact on the system reliability. A realistic cost/reliability analysis requires evaluation models that can recognize the highly erratic nature of these energy sources while maintaining the chronology and interdependence of the random variables inherent in them. This paper presents a simulation method that provides objective indicators to help system planners decide on appropriate installation sites, operating policies, and selection of energy types, sizes, and mixes in capacity expansion when utilizing PV and wind energy in small isolated systems.

Application of Monte Carlo simulation to generating system well-being analysis

System well-being analysis is a new approach to power system generation adequacy evaluation which incorporates deterministic criteria in a probabilistic framework and provides system operating information in addition to risk assessment. This approach not only provides a new perspective to generation adequacy studies but can also be useful in those situations in which conventional probabilistic techniques are not normally accepted, such as, in system operating capacity reserve assessment and in small isolated system planning. The probabilities of system health, margin and risk are the basic well-being indices and can be evaluated using analytical techniques. Monte Carlo simulation can also be used to estimate the indices by simulating the actual process and random behavior of the system and can include system effects which may not be possible without excessive approximation in a direct analytical approach. This paper illustrates the utilization of Monte Carlo simulation to evaluate additional well-being indices and their distributions and the significance of this additional information on capacity reserve evaluation.

Capacity Expansion of Small Isolated Power Systems Using PV and Wind Energy

Renewable energy is being increasingly utilized in electric power systems due to environmental concems and energy cost escalation associated with the use of conventional energy sources. Photovoltaics and wind energy sources can significantly offset costly fuel in small isolated systems and can also have considerable impact on the system reliability. The utilization of renewable energy in capacity planning requires realistic cost/reliability evaluation models that can recognize the highly erratic nature of these energy sources while maintaining the chronology and interdependence of the random variables inherent in them. This paper presents an evaluation model and applies it to analyze optimum generation expansion of small isolated systems using PV and wind energy sources.

Unit Commitment Risk Analysis of Wind Integrated Power Systems

The utilization of wind power generation is increasing throughout the world and it is therefore important that these facilities be integrated in the existing generating capacity planning and operating protocols and procedures. This paper presents an approach to evaluate the contribution that wind power can make to the load carrying capability of a power generating system in an operating scenario. The basic concepts of unit commitment risk analysis are extended to include the inherent variability associated with wind power by developing short-term probability distributions of the wind speed and wind power output using auto-regressive moving average (ARMA) time series models. The operating capacity contributions attributable to wind power are illustrated by application to a small test system and are expressed in terms of the increased load carrying capability due to the wind power generating facilities.

Composite System Adequacy Assessment Incorporating Large-Scale Wind Energy Conversion Systems Considering Wind Speed Correlation

This paper investigates the reliability effects on a composite generation and transmission system associated with the addition of large-scale wind energy conversion systems (WECS) using the state sampling Monte Carlo simulation technique. Three types of composite system were developed to represent the general conditions that exist in practical systems and used to conduct the studies presented in this paper. Load point and system indices for the three types of test systems are presented to illustrate the impact of adding wind farms in various system locations and the effect of varying the degree of wind speed correlation. The contributions of large-scale wind farms considering different degrees of wind speed correlation to the reliability performance of an electric power system are quantified in this paper.

Wind power simulation model for reliability evaluation

The rapidly increasing contribution of wind power to electric power generation around the world has motivated a need to develop more widely applicable methodologies for evaluating the actual benefits of adding wind turbines to traditional power generating systems. Reliability and cost evaluation of wind generation systems requires simulation of long-term chronological wind speed data for specified geographical wind farm sites. The main steps to construct the wind speed simulation model are presented in this paper. It is important that the developed models maintain the main statistical characteristics of the wind farm locations. Wind speed data from two wind sites are used to illustrate the model. The results of wind data simulation, power output profile, and power system risk evaluation are presented and compared using different types of wind models at different wind farm sites. The objective is to derive a general and appropriate model for reliability evaluation of power systems containing wind sources

Reliability Evaluation Considering Wind and Hydro Power Coordination

Wind energy application in electric power systems continues to increase globally. The contribution of wind farms to the overall system reliability is limited by the uncertainty in power output from these highly variable energy sources. The ability of a power system to absorb available wind energy and maintain the system reliability and stability is reduced as the wind penetration in the system is increased. It therefore becomes important to coordinate the operation of wind power with fast responding conventional generating units. Hydro facilities with energy storage capability can alleviate the impact of wind power fluctuations and also contribute to system adequacy. A methodology for an energy limited hydro plant and wind farm coordination is developed using a Monte Carlo simulation technique considering the chronological variation in the wind, water and the energy demand. The IEEE four-state model is incorporated in the developed technique to recognize the intermittent operation of hydro units. The proposed approach is applied to the IEEE-RTS, and quantitative assessment of reliability benefits from effective utilization of wind and water resources are conducted through a range of studies. The effects of major system parameters on the system adequacy are also investigated.

Adequacy Assessment Considerations in Wind Integrated Power Systems

There is a wide range of possible data representations, models and solution techniques available when conducting adequacy assessments of wind integrated generation or composite generation and transmission systems. This paper presents some of the basic factors and procedures that need to be considered when conducting wind integrated system adequacy assessment. Focus is placed on possible wind speed data models, wind energy conversion system models and their application in generation and bulk system adequacy evaluation. A series of studies is presented using two published test systems, the RBTS and the IEEE-RTS. These studies illustrate the effects of wind farm correlation on the determination of wind power capacity credit indices and on general adequacy assessment in generating and bulk electric systems. The impacts on the system well-being indices of adding wind power to a bulk electric system and the effects on the adequacy of a wind integrated system from energy storage obtained using hydro generation are examined by application to the IEEE-RTS.