Future of Dams

This paper presents an approach for a geometrical solution of an optimal power flow (OPF) problem for a two-bus power system (slack and PV buses). The algebraic equations for the calculation of the Lagrange multipliers and for the minimum losses value are obtained. These equations are used to validate the results obtained using an OPF program.     

PES Meetings

This letter presents a hybrid genetic algorithm (GA) method to solve optimal power flow (OPF) in a power system incorporating flexible AC transmission systems (FACTS). In the solution process GA is integrated with conventional OPF to select the best control parameters to minimize the total generation fuel cost and keep the power flows within the security limits. A case study using an IEEE test system is presented to demonstrate its applicability.     

A hybrid GA approach for OPF with consideration of FACTS devices

This letter presents a hybrid genetic algorithm (GA) method to solve optimal power flow (OPF) in power systems incorporating flexible AC transmission systems (FACTS). In the solution process, GA is integrated with conventional OPF to select the best control parameters to minimize the total generation fuel cost and keep the power flows within the security limits. A case study using an IEEE test system is presented to demonstrate its applicability     

Optimal location of Hybrid Flow Controller considering modified steady-state model

This paper introduces a modified power flow model for Hybrid Flow Controller (HFC) as an energy flow controller. The existing power flow models for Hybrid Flow Controller are suitable only for conventional power flow analysis, and are not applicable for OPF and optimal location analysis of FACTS devices. In this paper, some modifications were applied to the existing models to promote the accuracy and improve their conformability on any power system and hence leading to a precise steady-state analysis. The modified model and the existing model are investigated using different IEEE test systems and the results are compared together. The optimization method is numerically solved using Matlab and General Algebraic Modelling System (GAMS) software environments. The solution procedure uses Mixed Integer Non-Linear Programming (MINLP) and Relaxed Mixed Integer Non-Linear Programming (RMINLP) to solve the optimal location and setting of HFC incorporated in OPF problem considering the total fuel cost, power losses, and the system loadability as objective functions for single objective optimization problem and improve the power system operation.     

A modified shuffle frog leaping algorithm for multi-objective optimal power flow

This paper presents an efficient and reliable evolutionary-based approach to solve the Optimal Power Flow (OPF) problem by considering the emission issue. The OPF problem has been widely used in power system operation and planning for determining electricity prices. Therefore, the conventional optimal power flow cannot meet the environmental protection requirements, because it only considers generation cost minimization. The multi-objective optimal power flow considers economical and emission issues. By adding the emission objective in the optimal power flow problem, this problem become more complicated than before and it needs to be solved with an accurate algorithm. This paper proposes an algorithm based on the Shuffle Frog Leaping Algorithm (SLFA) to solve the multi-objective OPF problem. Furthermore, this paper presents a modified SLFA called MSLFA algorithm which profits from a mutation in order to reduce the processing time and improve the quality of solutions, particularly to avoid being trapped in local optima. The IEEE 30-bus test system is presented to illustrate the application of the proposed problem.     

Economic operation of wind farm integrated system considering voltage stability

Wind farms interconnected to power system bring new challenges to power system economic operation. It is imperative to study how to solve optimal power flow (OPF) formulation with wind farms. In this paper, a multi-period optimal power flow (DOPF) is studied based on traditional OPF algorithm. According to the characteristic equations of asynchronous generator, the paper deduces a new algorithm that fits the DOPF formulation with wind farms. Based on the primal–dual interior point algorithm (PDIPM), a new modified algorithm is proposed. Besides, the voltage stability indicator, L-indicator, is also introduced into DOPF to demonstrate voltage stability of power system after wind farms incorporation. By taking SVC reactive power compensation into account, the paper analyzes its influences on system voltage stability. In addition, four different static load models are researched to reveal their effects on system-operating characteristics. An example shows the algorithm's effectiveness and computation performance of the proposed method and several conclusions are obtained as well.     

Hydrogen storage and demand to increase wind power onto electricity distribution networks

An optimal power flow (OPF) methodology is developed to investigate the provision of a demand hydrogen as a means to maximise wind power generation in relation to a constrained electricity network. The use of excess wind energy to generate hydrogen for use as a transport fuel is investigated. Hydrogen demand is included in the objective function of the OPF, and a techno-economic analysis is presented. We conclude that using this method to generate hydrogen increases the utilisation of wind energy and allows for a hydrogen demand to be met at or near to the point of use. The OPF algorithm that has been developed optimises the amount of wind energy utilised, as well as minimising the amount of hydrogen demand not met. The cost at which the hydrogen is produced was found to be dependent on the operating methodology, component capital investment costs, level of hydrogen demand, and storage constraint.     

MFACTS System Studies

The unified power flow controller (UPFC) combines the advantageous features of both shunt and series compensations; therefore, it is an effective device that can adjust power system parameters in order to increase power transfer capability, stabilize the system and improve the economics of a power system. This paper presents the exact pi-model of the UPFC-inserted transmission lines from which the injection-model using two-port networks is derived. The equations derived in this paper are applied to a small test system, where the impact of UPFC on OPF results is shown.     

矢量化技术在电力系统高性能计算中的应用

将矢量化技术应用到电力系统计算中可以极大的提高程序运行速度并降低建模和算法开发的复杂程度。介绍了矢量化技术的基本原理及其在高性能科学数值计算领域的应用情况．推导了直角坐标和极坐标下潮流计算的相关矢量化计算式,说明了矢量化在电力系统建模和算法实现中的应用可行性。设计和开发了电力系统矢量化运算库,并基于该库开发了最优潮流程序,通过算例数据说明了矢量化技术能够提高计算速度。提出了矢量化电力系统程序开发的解决方案,该方案缩短了高性能计算程序的开发周期,加速了算法的实用化进程。     

A new modeling and solution method for optimal energy flow in electricity‐gas integrated energy system

With the increasing interdependency of electricity and gas, it is necessary to simultaneously investigate electric power system and natural gas system from the perspective of an electricity‐gas integrated energy system (EGIES). As an extension and integration of both optimal power flow (OPF) and optimal gas flow (OGF), optimal energy flow (OEF) is regarded as the cornerstone of the EGIES and lays an essential foundation for further research on the EGIES's operation and analysis considering stochastic conditions and contingency states. The objective of this paper is to develop a generalized mathematical model and a universally applicable simulation tool for the OEF problem. First, natural gas system is modeled in a way similar to electric power system according to electricity‐gas analogy analysis, where gas admittance, gas nodal admittance matrix, and the nodal equation of gas flow conservation are derived. Then, a generalized accurate OEF model is formulated by simultaneously integrating the OPF model and the OGF model as well as their coupling constraints in a unified modeling framework. Furthermore, an available hybrid optimization approach consisting of whale optimization algorithm, MATPOWER, hydraulic calculation iterative program, and nonstationary penalty function method is put forward to solve the OEF problem. The accuracy, feasibility, and applicability of the proposed modeling and solution method is finally demonstrated by analyzing Belgian 20‐node gas system combined with IEEE 30‐bus test system.     

Nonlinear optimal power flow with intertemporal constraints

This letter describes an interior point dynamic optimal power flow (OPF) algorithm and illustrates its application to a model network that includes large energy-intensive consumers such as metal smelters that are able to reschedule demand to reduce electricity cost subject to meeting the day's production quota. Although the behavior predicted by the algorithm is no surprise (those consumers whose demand is price sensitive reschedule their power purchases to periods of lower energy cost), its efficiency demonstrates the power of the approach. Relaxation of intertemporal and operational constraints leads to an algorithm in which an inner loop rapidly solves a series of relatively small quadratic programming problems via an interior point method while an outer loop is performing computations analogous to an iterative load flow calculation     

The established mega watt linear programming-based optimal power flow model applied to the real power 56-bus system in eastern province of Saudi Arabia

A current trend in electric power industries is the deregulation around the world. One of the questions arise during any deregulation process is: where will be the future generation expansion? In the present paper, the study is concentrated on the wheeling computational method as a part of mega watt (MW) linear programming-based optimal power flow (LP-based OPF) method. To observe the effects of power wheeling on the power system operations, the paper uses linear interactive & discrete optimizer (LINDO) optimizer software as a powerful tool for solving linear programming problems to evaluate the influence of the power wheeling. As well, the paper uses the optimization tool to solve the economic generation dispatch and transmission management problems. The transmission line flow was taken in consideration with some constraints discussed in this paper. The complete linear model of the MW LP-based OPF, which is used to know the future generation potential areas in any utility is proposed. The paper also explains the available economic load dispatch (ELD) as the basic optimization tool to dispatch the power system. It can be concluded in the present study that accuracy is expensive in terms of money and time and in the competitive market enough accuracy is needed without paying much.     

Contents

Optimal power flow (OPF) is one of the main functions of power system operation and control. Solving such problems requires efficient optimization algorithms. This letter describes the development of an efficient tabu search (TS) algorithm for solving the optimal power flow problem. The developed algorithm was tested against a modified IEEE-RTS-24-bus test system. The results were compared with ones obtained from sequential quadratic programming (SQP) and evolutionary programming (EP) techniques. All approaches give more or less the same optimal solutions. Tabu search is the most efficient technique among these, since it consumes minimum computing time and provides accurate solutions.     

Modeling of integrated renewable energy system for electrification of a remote area in India

Over the years, renewable energy based power generation has proven to be a cost-effective solution in stand-alone applications in the regions where grid extension is difficult. The present study focused on the development of models for optimal sizing of integrated renewable energy (IRE) system to satisfy the energy needs in different load sectors of four different zones considered in Chamarajanagar district of Karnataka state in India. The objective of the study is to minimize the total cost of generation and cost of energy using genetic algorithm (GA) based approach. Considering optimization power factor (OPF) and expected energy not supplied (EENS), optimum system feasibility has been investigated. Based on the study, it has been found that IRES is able to provide a feasible solution between 1.0 and 0.8 OPF values. However, power deficit occurs at OPF values less than 0.8 and the proposed model becomes infeasible under such conditions. Customer interruption cost (CIC) and deficit energy (DE) for all zones were also computed to quantify the reliability of the systems.     

Multiobjective clearing of reactive power market in deregulated power systems

This paper presents a day-ahead reactive power market which is cleared in the form of multiobjective context. Total payment function (TPF) of generators, representing the payment paid to the generators for their reactive power compensation, is considered as the main objective function of reactive power market. Besides that, voltage security margin, overload index, and also voltage drop index are the other objective functions of the optimal power flow (OPF) problem to clear the reactive power market. A Multiobjective Mathematical Programming (MMP) formulation is implemented to solve the problem of reactive power market clearing using a fuzzy approach to choose the best compromise solution according to the specific preference among various non-dominated (pareto optimal) solutions. The effectiveness of the proposed method is examined based on the IEEE 24-bus reliability test system (IEEE 24-bus RTS).     

Demand shifting bids in energy auction with non-convexities and transmission constraints

The major objective of this paper was to propose clearing and pricing models suitable for demand shifting bids in the efficient, but non-convex pool-based auction. Complex generators' offers bring non-convexities into the efficient auctions due to e.g. start-up costs and times. This paper focused on the responsive demands, introducing simple, yet adequate linear constraints into a multi-period bid/offer-based optimal power flow (OPF DC) model. As the standard locational marginal prices (LMPs) may not support the auction outcomes due to non-convexities, uplifts are needed to reduce generators' loss. Previous work has developed a minimum-uplift pricing model that directly optimizes prices, so that uplifts arising from generators' profit-suboptimality and simple, elastic demands' benefit-suboptimality are minimized. This work extended the mixed integer linear programming (MILP) formulation of the previous model to incorporate new linear constraints defining benefit-suboptimality of demand shifting bids. Furthermore, the transmission constrained market was attempted. As a result, the buyers were protected against over-curtailment; moreover, prices complemented with minimum uplifts were fair for both generators and demands. The models were validated on the literature-based cases, including IEEE RTS 24-node 24-hour system.     

基于单机无穷大等效的暂态稳定约束最优潮流算法

为解决传统的考虑暂态稳定约束的最优潮流(TSOPF)方法暂态约束条件数量庞大、计算复杂性高等问题,可通过修改Matpower工具包和PSS/E软件,进而实现了一种故障初始时刻考虑暂态约束的TSOPF算法,通过对等效系统初始稳态功角偏差的约束,一般TSOPF方法中数量庞大、复杂的暂态约束条件被简化为数量唯一的稳态约束条件,TSOPF方法的问题规模被降低到与传统最优潮流问题相同的程度。基于IEEE3机9节点系统和10机新英格兰系统的算例,验证了该算法的有效性。     

Advanced real-time congestion management through both poolbalancing market and bilateral market

A framework for real-time congestion management under a marker structure similar to the newly proposed UK trading arrangement is presented in this letter, in which not only resources in balancing market but also some bilateral contracts can be dispatched if necessary. The linearized model of a modified optimal power flow (OPF) is proposed to implement such a framework. A 5-bus test system is used to illustrate the effectiveness of the proposed method     

Derivatives of the nodal prices in market power screening

This paper proposes a novel method for market power screening. This method is developed for horizontally and vertically consolidated power markets, and is based on the optimal power flow (OPF) model properties. It undertakes the calculation and analysis of a matrix of derivatives of the nodal prices with respect to generating unit offer prices. The analysis takes into consideration the influence of particular partakers and energy groups on the nodal prices. This paper presents a theoretical analysis of the partakers' and groups' profits as well as a method for the market power screening. Moreover, the issue wherein the LMP model generates prices above the highest bidding price is discussed. Illustrative case studies and case studies based on the Polish wholesale balancing power market model are also presented.     

基于矢量距免疫算法的电力系统最优潮流计算

将基于矢量距理论的免疫算法应用于最优潮流计算,并在计算中引进自适应交叉和变异算子,根据抗体个体的适应度大小来动态调整交叉率和变异率,很大程度上保护了每代中的较优个体。根据最优潮流中控制变量的特点,运用浮点数编码方法,无需解码,计算简单;通过用IEEE 30节点标准测试系统计算多次,燃料耗费显著改善,表明了所用方法的可行性和有效性。