Short-term Hydrothermal Coordination Problem Research Articles

A modified incremental gravitational search algorithm for short-term hydrothermal scheduling with variable head

In this study, the solution of short-term hydrothermal coordination problem (STHCP) with variable head was performed. In the manuscript, incremental gravitational search algorithm (IGSA) which was developed as a new method has been applied to two different power problems. One of the systems used as an example is a variable head STHCP which has previously been solved in the literature by neglecting transmission line losses. The second is a lossy system designed as a variable head STHCP, with the purpose of contributing to the literature. In the lossy system, Newton–Raphson AC power flow method was used to calculate transmission line losses. Possible electrical and hydraulic constraints in the solution of the problem were satisfied using the penalty function method. The results obtained from the solutions of the sample systems were compared and discussed.

Gravitational search algorithm applied to fixed head hydrothermal power system with transmission line security constraints

Optimal operation and production planning are important problems for electric power generation systems. Optimal operation of an energy generation system conventionally refers to the minimization of total thermal fuel cost (TTFC). However, the presence of thermal and hydraulic generation units in a power system requires that hydraulic as well as thermal constraints be added to a problem, which is referred to as a short term hydrothermal coordination problem (STHCP). STHCPs assume that the amount of water in the reservoirs of a hydraulic generation unit has no effect on power generation when its net heads are fixed. This study applied a gravitational search algorithm (GSA) for the solution of a STHCP with fixed head. The probable electrical and hydraulic constraints of the problem have been provided by punishment function method. Line losses of the power system were calculated using the Newton-Raphson load flow method. Two different cases, where transfer capacities of transmission lines were neglected and included, were set up, and the problem was solved for both cases. Transfer capacities of transmission lines were included to make the problem more complex and realistic. Solutions for both cases were discussed.

Stabilization of the Generalized Benders Decomposition applied to Short-Term Hydrothermal Coordination Problem

Solving the Short Term Hydrothermal Coordination (STHTC) Problem considers the resolution of both the Unit Commitment (UC) and the Economic Dispatch (ED) for thermal and hydraulic units. In order to avoid post-dispatch corrections, the transmission network is modeled with a high level of detail considering an AC power flow. These facts lead to a very complex optimization problem which is solved by using a novel decomposition approach which combines Generalized Benders Decomposition (GBD) with Bundle methods presented in [LS97]. This proposed method resembles a stabilized version of the cutting planes method, which drastically reduces the well-known tailing-off effect that Benders methods have. The approach presented in this work allows the decomposition of the whole problem in a quadratic mixed integer master problem, and in a non-linear subproblem which should be separable. The former defines the state and the active power dispatched by each unit whereas the latter determines the reactive power to meet the electrical constraints through a modified AC optimal power flow (OPF). These approaches were applied to a 9-bus test case, and to the IEEE 24-bus test case. The problem is solved for a time horizon of a day with a one-hour step.

Optimization methods applied for solving the short-term hydrothermal coordination problem

Short-term hydrothermal coordination (STHTC) is a very complicated optimization problem. It is a dynamic large-scale non-linear problem and requires solving unit commitment and economic power load dispatch problems. From this perspective, many successful and powerful optimization methods and algorithms have been employed to solve this problem. These optimization methodologies and techniques are widely diverse and have been the subject of ongoing enhancements over the years. This paper presents a survey of literature on the various optimization methods applied to solve the STHTC problem. A review and a methodology-based classification of most of the publications on the topic are presented.

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.

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.

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.

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>

Continuous Solution Simulation in the Short-Term Hydrothermal Coordination Problem

Continuous Solution Simulation in the Short-Term Hydrothermal Coordination Problem

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.