Optimal Adjustments on the Market Dispatch Solution to Supply System Losses

This paper proposes an Optimal Power Flow (OPF) problem to obtain a balanced power system operating condition from the solution of a market dispatch. The goal of this OPF problem is to correct the system power imbalance due to transmission losses. The solution provided by the proposed OPF problem corresponds to the generation power adjustments required to achieve the system power balance in an economically optimal manner. The performance of the proposed model is tested on the IEEE One Area RTS-96 benchmark system. The obtained base-case operating condition is compared with others obtained by two variations of the proposed model

SDE-based wind speed models with Weibull distribution and exponential autocorrelation

This paper discusses three approaches to construct wind speed models based on Stochastic Differential Equations (SDEs). The methods are applied to construct models able to simulate wind speed trajectories that are statistically described by means of the Weibull distribution and the exponential autocorrelation. The ability of the three models to reproduce stochastic processes with the above indicated statistical properties is duly studied and compared. With this aim, wind speed measurements recorded in a weather station located in Ireland are analyzed. The parameters obtained in this analysis are used to set up the developed models. Finally, the statistical properties of the trajectories generated by the three models are compared with the statistical properties of the considered wind speed data set

Modelling Load Stochastic Jumps for Power Systems Dynamic Analysis

This letter proposes an approach to model power system loads as stochastic processes that incorporate both continuous and event-driven dynamics. The letter provides a brief theoretical background on the stochastic differential equations defining Ornstein-Uhlenbeck processes with jumps used for the stochastic modeling of power system voltage-dependent loads. The all-island 1479-bus Irish transmission system serves to illustrate and test the proposed jump-diffusion model

Design of Tools for PEV-integration Studies

This paper presents and analyzes four different optimal power flow formulations designed to find the maximum number of plug-in electric vehicles that can be charging simultaneously for a given power system operating condition. The modeling approach to represent the coincident charge of PEVs is based on the modeling philosophy of homotopy methods. The analyzed models,are intended to help in tasks related to both planning and operation of power systems. The developed formulations are tested in the IEEE RTS-96 benchmark system. The obtained results are discussed and suggestions on the applicability of the models are provided

Combining Quasi-static Models and Homotopy Techniques for Loading Margin Computation

This paper analyzes a tool devoted to the computation of the loading margin of power systems in the context of long-term voltage stability assessment. This tool is based on the application of homotopy techniques to solve a power system model constructed in the basis of quasi-steady-state approximations. The analyzed tool is compared to the well-known continuation power flow method in terms of accuracy and computing time. The ability of the tool to identify small-signal stability issues is also tested. This last point is verified by means of time-domain and quasi-steady-state simulations. All stability assessment methods and simulations are performed on a real-world power system

Impact of Variability, Uncertainty and Frequency Regulation on Power System Frequency Distribution

This work originates from the observation of the frequency distribution of the Irish system as obtained from a Frequency Disturbance Recorder lent to the last author by the University of Tennessee. The probability density function of such a distribution appears to be bimodal. The paper first investigates how stochastic sources, in particular, load and wind power estimation errors, impact on the distribution of the frequency of a high-voltage transmission system. Then, possible routes to obtain a bimodal distribution of the frequency are explored and the most likely cause that leads to the observed behaviour of the Irish system is identified. Finally, the paper presents a comparison of different frequency regulation strategies and their impact on the distribution of the frequency. A sensitivity analysis of wind speed and load parameters is presented and discussed based on the IEEE-14 bus system

Influence of the controllability of electric vehicles on generation and storage capacity expansion decisions

This paper proposes a capacity investment model to analyze the influence of the controllability of the charge of plug-in electric vehicles (PEVs) in generation and storage expansion decisions. The proposed model provides the financial incentives that should be offered to PEV users in order to implement the optimal expansion decisions. Considering that the decision-making process faced by the power system planner must simultaneously consider long- and short-term uncertainties, a three-stage stochastic programming problem is formulated. In this model, capacity investments and financial incentives for PEV users are decided in the first stage, whereas operating decisions regarding the day-ahead and real-time markets are made in the second and third stages, respectively. Numerical results are provided from a realistic case study based on the isolated power system comprising Lanzarote and Fuerteventura islands in Spain

Scheduling isolated power systems considering electric vehicles and primary frequency response

The incorporation of renewable energy sources in isolated power systems is being significantly slower than in well-connected power systems. The intermittency and uncertainty of the power output of most renewable power technologies prevent a greater usage of these technologies in isolated power systems, in which the supply security is the major concern. In this paper we formulate a stochastic unit commitment problem that allows the participation of electric vehicles in energy, reserve capacity and primary frequency response markets in order to increase the flexibility of the power system operation. We explicitly consider the uncertainty in the power demand and renewable power availability, as well as accounting for the possibilities of contingencies of generating units using a N-1 security criterion. The proposed formulation is tested on an actual isolated power system comprising 38 generating units and 8 buses

Construction of SDE-based wind speed models with exponentially decaying autocorrelation

This paper provides a systematic method to build wind speed models based on stochastic differential equations (SDEs). The resulting models produce stochastic processes with a given probability distribution and exponentially decaying autocorrelation function. The only information needed to build the models is the probability density function of the wind speed and its autocorrelation coefficient. Unlike other methods previously proposed in the literature, the proposed method leads to models able to reproduce an exact exponential autocorrelation even if the probability distribution is not Gaussian. A sufficient condition for the property above is provided. The paper includes the explicit formulation of SDE-based wind speed models obtained from several probability distributions used in the literature to describe different wind speed behaviors. All models are validated through numerical simulations. Finally, the proposed procedure is applied to model the wind speed observed at a meteorological station in New Zealand. A comparison of the statistical properties of the wind speed measurements and of the stochastic process generated by the SDE model is also provided

On the Stochastic Nature of Deterministic Power System Models for Dynamic Analysis

The paper presents a study on the impact of uncertainty on the dynamic response of electric power systems. Three sources of uncertainty are considered, namely, (i) uncertainty in the values of the parameters of physical devices; (ii) uncertainty in the models of dynamic devices; and (iii) variations of the parameters and the numerical scheme to integrate the differential algebraic equations that describe the system. A Monte Carlo analysis is used to define the impact of each source of uncertainty as well as all sources together on the dynamic response of the well-known IEEE 14-bus system