Sharif Digital Repository

This paper introduces a day-ahead clearing model for the simultaneous energy and ancillary services market in high penetration of renewable energy sources (RESs) considering fast-start generators’ behaviors as non-spinning reserve providers. For managing the uncertainties of RESs, the system operator takes the advantages of the stochastic model of security-constrained unit commitment (SCUC) problem considering plausible scenarios. The non-convexities due to the startup costs, minimum power outputs, and commitment variables make the stochastic SCUC problem and market-clearing non-convex. Meanwhile, with traditional market-clearing methods for energy and ancillary services based on marginal... 

With the proliferation of intermittent renewable energy sources, power systems need to withstand an increasing number of disturbances that may affect system frequency. In this paper, we focus on the effects of high penetration level of wind turbine-generators (WTG) on the power system operational planning from the frequency point of view. Specifically, an exact formulation for the minimum frequency calculation is presented to increase accuracy and speed of analyses. Then, the effect of WTG's frequency response on the power system frequency stability is investigated to compute the maximum acceptable generation outage as a function of penetration level. Finally, as an application to power... 

The interdependencies of power systems and natural gas networks have increased due to the additional installations of more environmental-friendly and fast-ramping natural gas power plants. The natural gas transmission network constraints and the use of natural gas for other types of loads can affect the delivery of natural gas to generation units. These interdependencies will affect the power system security and economics in day-ahead and real-time operations. Hence, it is imperative to analyze the impact of natural gas network constraints on the security-constrained unit commitment (SCUC) problem. In particular, it is important to include natural gas and electricity network transients in... 

The forecast errors for distributed energy resources (DERs) and hourly demands have contributed to power system uncertainties and additional risks in the day-ahead scheduling of electricity markets. In this paper, a risk-based approach is introduced to determine the stochastic solution of network-constrained unit commitment (NCUC) when additional uncertainties are embedded in the power system scheduling. The historical power market transaction data are used to model nodal injection uncertainties and reserve capacity requirements are considered to assess the solution of the risk-based NCUC. The proposed NCUC problem is formulated as a single-stage second order cone program which is a convex... 

This paper addresses a novel formulation and solution for the security constrained reserve management (SCRM) problem in both normal and N − 1 contingency conditions. Indeed, the SCRM problem is a modified version of the security constraint unit commitment problem which is updated with the operational reserve management and frequency stability constraints in both normal and N − 1 contingency conditions. The objective of this problem is to determine the optimal amounts of generation associated with different units and frequency regulation reserve (FRR) and allocate the FRR among the generation units. Therefore, the SCRM problem is a mixed integer nonlinear problem which is solved using the... 

This article addresses a centralized generation expansion planning problem, accounting for both long- and short-term uncertainties. The long-term uncertainty (demand growth) is modeled via a set of scenarios, while the short-term uncertainty (wind power generation) is described by a family of probability distributions with the same first- and second-order moments obtained from historical data. The resulting model is a distributionally robust chance-constrained optimization problem, which selects the conventional generating units to be built among predefined discrete options. This model includes a detailed representation of unit commitment constraints. To achieve computational tractability,... 

Power generation consumes a substantial amount of water in the power industry. In order to address the impact of water consumption restriction on the power generation, this paper proposes a security-constrained unit commitment (SCUC) formulation considering water consumption impact as an additional constraint. To this end, the water consumption in power plants is formulated. Consequently, the SCUC is extended to consider the consumed water volume as a restricting factor. A procedure is introduced to investigate the most appropriate point of power generation operation to save a vital amount of water by raising reasonable generation costs. The objective of the proposed model is to minimize the... 

Photovoltaic energy is one of the clean and efficient energies which has been developing quickly in the last years. As the penetration of solar plants is increasing in the electricity network, new problems have arisen in network operation. This paper models a high penetration factor of solar energy in the electricity network and investigates the impact of solar energy growth on both the generation schedule of different power plants and in the natural gas transmission network. Fuel management of gas power plants is modeled through simulation of the natural gas transmission network. To this end, an increase in the penetration of solar energy in the electricity network inevitably leads to a... 

Secure and reliable operation is one of the main challenges in restructured power systems. Wind energy has been gaining increasing global attention as a clean and economic energy source, despite the operational challenges its intermittency brings. In this study, we present a formulation for electricity and reserve market clearance in the presence of wind farms. Uncertainties associated with generation and line outages are modeled as different system scenarios. The formulation incorporates the cost of different scenarios in a two-stage short-term (24-hours) clearing process, also considering different types of reserve. The model is then linearized in order to be compatible with standard... 

Developments of the smart grid infrastructure can facilitate the upsurge of Demand Response (DR) share in power system resources. This paper models the effects of Demand Response Programs (DRPs) on the behavior of the electricity market in the Day-Ahead (DA) session. Decision makers look for the best DR tariff to employ it as a tool to obtain a flexible and sustainable energy market. Employing the most effective DRP is of crucial importance. An optimized DR model and the optimum rates for each DRP are found to meet the decision makers' requirements. optimizing the nodal tariff and incentive values of different DRPs are proposed in the electricity market. In such environment, market... 

For the purposes of lowering environmental emission cost and increasing economic profit, energy efficient combined heat and power (CHP) units can be integrated with conventional separate heat and power production units to meet heat and power demands. The goal of this study is to develop and examine a novel heuristic and deterministic optimization algorithm for solving the profit-based unit commitment (PBUC) problem for a generation company with integrated CHP-thermal-heat only system for (i) satisfying demands for heat and power, (ii) selling spinning reserve for power, (iii) reducing environmental CO2 emission cost, and (iv) accounting for valve-point effects for steam turbines. For... 

This paper presents a new framework for evaluating contribution of wind farms in operational reliability level of power systems. In this regard, at first, it provides a short-term analytical model well designed to represent intermittent and uncertain nature of wind power. Combining the attained multi-state model of wind farms with the other committed generating units, operational risk of the system is evaluated. The concept of Pennsylvania-New Jersey-Maryland (PJM), previously developed to assess the short-term/mid-term reliability of conventional generating units, is revisited in this paper to more practically incorporate wind farms in reliability studies of the power system. The proposed... 

Uncertainties associated with bus loading and components' availability lead to uncertainties in different system variables based on the system physical and economical relationships. Line flows, bus voltages, different prices, and other variables and indices, such as available transfer capacity (ATC), are stochastic and cannot be expressed as a determined quantity. Traditionally, in order to model the stochastic nature of power systems, a stochastic power flow algorithm is used. In this paper, stochastic-algebraic method is applied to find the probability density function (pdf) of ATC. The algorithm linearizes the optimal power flow formulation and uses Gram-Charlier expansion to find the pdf... 

This paper presents a formulation of fuzzy optimization for uncertainties in natural gas in fuel constraints for hourly individual unit and total unit fuel consumptions. Security Constrained Unit Commitment (SCUC) is usually a mixed integer programming and gas load flow has a non-linear equation a genetic algorithm is proposed to solve natural gas transmission network. A fuzzy mixed integer programming optimization is briefly discussed and adapted to deal with security constrained unit commitment schedule. Finally, two case studies are investigated (IEEE 6-bus system with 7-node natural gas transmission grid and the IEEE 118-bus power system linked with 14-node gas transmission test system)... 

Advancements in smart grid technologies have made it possible to apply various options and strategies for the optimization of demand response (DR) in electricity markets. DR aggregation would accumulate potential DR schedules and constraints offered by small- and medium-sized customers for the participation in wholesale electricity markets. Despite various advantages offered by the hourly DR in electricity markets, practical market tools that can optimize the economic options available to DR aggregators and market participants are not readily attainable. In this context, this paper presents an optimization framework for the DR aggregation in wholesale electricity markets. The proposed study... 

This paper proposes a short-term stochastic SCUC model that simultaneously schedules generating units' energy and spinning reserve in presence of wind energy. It should be noted that system uncertainties, wind farm output uncertainties and power generators and lines outages are also considered in optimization process. The proposed stochastic SCUC model is formulated as a two-stage stochastic mixed-integer programming model. Performance of the proposed formulation is proved through test systems and the results are also presented  

Different sources of uncertainty in power systems, i.e., the uncertainties associated with bus loading and component availability is reflected in uncertainties in different system variables through system physical and economical relationships. A stochastic power flow algorithm can be used to model the stochastic nature of power systems. The algorithm introduced in this paper calculates the probability density function (pdf) of marginal prices of different market services. These pdfs provide the market participant with some valuable information to reduce the risk of their decisions and actions. The algorithm linearizes the optimal power flow formulation and uses the Gram-Charlier method to... 

PV generation variability and uncertainty significantly influence operation of the power systems with high penetration of PV sources. The potential impact of distributed PV generation on ramp rate requirements in the IEEE 24-bus system is evaluated in this paper. PV generation and load are, here, probabilistically modeled using actual data and curve fitting approach. Probabilistic unit commitment (UC) based on unit de-commitment method combined with two point estimate method (2-PEM) is used to determine the ramp rate required to compensate for the PV power fluctuations. The proposed method considers stochastic factors and their effects on the dispatch results. Two scenarios are studied to... 

Recently in electricity markets, a massive focus has been made on setting up opportunities for participating demand side. Such opportunities, also known as demand response (DR) options, are triggered by either a grid reliability problem or high electricity prices. Two important challenges that market operators are facing are appropriate designing and reasonable pricing of DR options.In this paper, time-of-use program (TOU) as a prevalent time-varying program is modeled linearly based on own and cross elasticity definition. In order to decide on TOU rates, a stochastic model is proposed in which the optimum TOU rates are determined based on grid reliability index set by the operator. Expected... 

Unit Commitment is the optimization process for minimizing the total cost of real power generation meeting the generating units and the system constraints. With the restructuring in power systems, the matter of great concern is the fuel cost and consequently electricity price increase in some hours of the day. Accordingly, the optimum performance of Demand Side Management (DSM) has been gaining great attention recently. In this paper, the effect of the optimum performance of Emergency Demand Response Program (EDRP) on the cost of the unit commitment problem considering the line flow constrains is scrutinized. Due to the fact that the simultaneous adoption of the unit commitment and demand...