Hydrothermal Coordination Problem Research Articles

Allocation of FACTS devices in hydrothermal systems

This work presents a methodology to represent and analyze the influence of FACTS (flexible AC transmission systems) devices on the multiperiod economic dispatch problem. Two FACTS devices are represented: the series compensator and the phase shifter. The aim is to find the best location of FACTS devices in order to minimize the expected thermal generation costs and the investments on these devices in a prespecified time interval. The methodology handles the operational interdependence between cascade hydro plants which characterize the hydrothermal coordination problem. Transmission losses and circuit capacity variation are also taken into consideration. The approach is tested in a small system and to the system of the southern region of Brazil in order to illustrate the application of the algorithm. Some wheeling transactions are also introduced to investigate their influence on the FACTS location. The results show the robustness of the approach while highlighting the main problems which need be investigated.

Short-term hydro-thermal coordination by Lagrangian relaxation: solution of the dual problem

This paper addresses the short-term hydrothermal coordination problem. This problem is large-scale, combinatorial and nonlinear. It is usually solved using a Lagrangian relaxation approach. In the framework of the Lagrangian relaxation, this paper provides a novel, nonoscillating and efficient multiplier updating procedure. This procedure advantageously compares with previously reported procedures such us subgradient and bundle methods. A realistic large-scale case study is used to illustrate the behavior of the proposed procedure.

A comparison of interior-point codes for medium-term hydro-thermal coordination

This paper studies the performance of newly developed and under development interior-point optimization codes as applied to the solution of medium-term hydro-thermal coordination (MTHTC) problems. We compare commercial and research codes, and their main advantages and drawbacks are pointed out. The codes that we study are: CPLEX 3.0-barrier (the latest version of OB1 by Lustig), HOPDM by Gondzio, LOQO by Vanderbei, PCx by Mehrotra's group, LIPSOL by Zhang, and LPA1 (a code being developed by the authors). All codes have been tested on the Spanish hydrothermal system.

Dual programming methods for large-scale thermal generation scheduling

The problem of thermal generation scheduling is considered in the framework of the short-term hydro-thermal coordination problem. Dual programming methods are applied to the large-scale problem deriving from a fine subdivision of the daily optimization horizon for networks with hundreds of thermal units. The starting point for the dual approach is obtained from the solution of a thermal scheduling problem with discarded generation ramp-rate constraints. The relaxed daily scheduling decouples into as many smaller dispatch problems as the number of subintervals. Two dual programming methods are implemented: the former is the dual active set algorithm by Goldfarb and Idnani; while the latter is based on the application of continuation method techniques. These approaches are extensively tested with reference to both a small sample system and to the daily thermal generation scheduling of the Italian (ENEL) system (over 100 thermal units and 96 quarter hour subintervals). Incorporating the dual programming approach within the ENEL hydro-thermal coordination procedure is also considered.

Hydrothermal generation coordination with direct load control

Abstract The paper applies the advanced multi‐pass dynamic programming (AMPDP) to solve the weekly hydrothermal generation coordination problem with direct load control (DLC) operation. The AMPDP technique can overcome the long calculation time and large data storage problems that the conventional dynamic programming (DP) method fails to resolve for large power systems and long scheduling period. The algorithm developed in this paper finds the optimal hydrothermal coordinated generation schedule of a power system that includes 48 thermal units and 8 hydro units with direct load control during a 192 hour study period. For the energy payback phenomenon of direct load control of air conditioner, the simulation of various energy payback patterns and various controllable capacities are presented in this paper.

A flexible approach to short-term hydro-thermal coordination. I. Problem formulation and general solution procedure

This paper presents a new flexible approach based on Lagrangian relaxation for solving the hydro-thermal coordination problem. Part I and Part II of this work make a complete theoretical and practical tool in order to solve this large scale, nonlinear, nonconvex and dynamic problem. The final result is an efficient and proven programming package within operation planning needs. Part I deals with the general problem formulation, with the application of the decomposition technique and with the primal problem solving. Methodological and modeling improvements are presented concerning costs of the excessive hydro production and advancements in the primal problem solving. The numerical simulations show flexibility of the proposed procedure which can be used to solve the short-term hydro-thermal coordination problem in completely different power systems.

Medium-term hydro-thermal coordination via hydro and thermal subsystem decomposition

This paper addresses the medium-term hydro-thermal coordination problem in an electric energy system. That is, the problem of finding the energy production of every power plant (hydro or thermal) in every subperiod of a given planning period, so that the customer load is supplied at minimum cost. The planning horizon is typically one to two months and the first week of this planning period is modeled in detail. The solution method proposed decomposes the problem in two subproblems corresponding to the hydro and thermal subsystems. These two subproblems are coordinated using a coordinating function for every subperiod. The coordinating function of a given subperiod expresses total production cost in that subperiod as a function of the total hydro production in that subperiod. The decomposition proposed makes it possible to use specialized algorithms to solve the hydro and thermal subproblems. This results in a very efficient computational procedure. From an experimental point of view the coordinating mechanism is robust. A case study is provided. It considers 61 thermal plants, a hydro system including 8 cascaded hydro plants and a 48 subperiods planning period.

The effect of pumped storage and battery energy storage systems on hydrothermal generation coordination

A simulated battery energy storage (BES) system is considered for integration into Taiwan Power Company System to study the economic benefits of the BES. The system had a pumped storage power plant with four units. The authors applied multipass dynamic programming to the solution of the short term hydrothermal coordination problem considering pumped storage and battery energy storage systems. The algorithm can quickly converge to an optimal generation schedule while achieving the minimum production cost of power systems. Substantial savings of memory and CPU time were realized by using this efficient algorithm. The load, committed units, and available water usage data from 9:00 PM June 17, 1988 to 9:00 PM June 24 were used to test this algorithm. Results showed that within 20 minutes on a PC/386 this algorithm could find the optimal generation schedule of all the units and the switching time of the BES while satisfying all the constraints.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Short term hydrothermal coordination using multi-pass dynamic programming

A technique that combines multipass dynamic programming (MPDP) technique with successive approximations to solve the daily hydrothermal coordination problem is presented. The long computation time and the large storage memory requirement are reduced. Due to the characteristics of hydrothermal coordination, the resulting load-following capability is much better than that achieved by applying MPDP to area automatic generation control. The generation can follow any shape load curve instead of only constant loads and ramps as in previous applications. >

Continuous Solution Simulation in the Short-Term Hydrothermal Coordination Problem

Continuous Solution Simulation in the Short-Term Hydrothermal Coordination Problem

Power System Planning Under Electricity Spot Pricing

valuable. Inthispapera new approach basedon thecontinuation methodforthesolution oftheHTCPistherefore presented. Here, thecontinuation parameter isapplied tothesystem load versustimecurve;however, themethodisapplicable to otherparametric variations suchasreservoir inflows. Results froman existing package forthreedifferent hydrothermal coordination problems areincluded toillustrate thecapabili¬ ties ofthemethod.Theapproach appears tobeveryreliable andefficient, particularly ifan initial optimal solution fora loadcurve nearthedesired one isknown.Thismakesthis technique especially attractive forrecoordination ofthe hydrothermal generation following a revision oftheload forecast curve or ofthepredicted waterinflows. Further¬ more,theability totracktheoptimum coordination fora family ofloadcurvesisalsouseful intheevaluation ofload management strategies, inunitcommitment, andinoperator training, allowing theusertorapidly examinetheoptimum coordination strategies forfamilies ofloadcurves.

Optimization-based methods for operations scheduling

The operations scheduling problem in electric power systems is to determine which generating units should be on-line and available for generation at each hour and the associated nominal generation or dispatch. This paper describes the scope of the operations scheduling problem, presents mathematical formulations to the problem, and surveys recent advances in optimization-based solution methods. It is mainly concerned with the shorter term aspects of the problem where the time horizon is of the order of a week. The unit commitment, short-term hydro scheduling, and hydro-thermal coordination problems as well as solution methods are emphasized.

Continuous Solution Simulation in the Short-Term Hydrothermal Coordination Problem

This paper presents a new approach for the solution of the short-term hydrothermal coordination problem based on the continuation method, a parametric optimization technique which solves the given problem by creating and solving a family of problems related by a single continuation parameter. In this application the continuation parameter continuously modifies the system load curve and/or the water inflows to the different reservoirs. Among some of the advantages of this approach we find: (1) It is not necessary to start with a feasible solution to the original problem. (2) The parameter continuation process yields piece-wise linear analytic optimum trajectories rather than point-wise solutions. (3) The method is very reliable. (4) Infeasible problems can be systematically detected. (5) The approach yields some unique analytic insight, as well as having applications in unit commitment, in the evaluation of load management strategies, in fast recoordination following a revision of the load forecast or reservoir inflows, and in operator training. An algorithm to implement this continuous simulation approach is presented and illustrated by various hydrothermal coordination examples.

CHT: A Digital Computer Package for Solving Short Term Hydro-Thermal Coordination and Unit Commitment Problems

CHT: A Digital Computer Package for Solving Short Term Hydro-Thermal Coordination and Unit Commitment Problems

CHT: A Digital Computer Package for Solving Short Term Hydro-Thermal Coordination and Unit Commitment Problems

The main characteristics of a digital computer package for solving the complex problem of Short-Term hydro-thermal unit commitment in medium and large size power systems (over 150 units) are presented. The over-all system design criteria, including Man Machine Interface (MMI), the software tools that support the analysis of the large volume of information required for unit commitment planning, and the optimization algorithms are discussed in the text. The package has been tested on a medium-size power system model.