Sharif Digital Repository

Over the past decade, the power industry in many countries around the world has been undergoing massive changes to introduce competition. In power systems under transmission open access, an optimal schedule of generation of units to satisfy the demand at the minimum production and transmission costs with consideration of system operation constraints is an important issue. In this paper, a method for centralized economic dispatch in deregulated power systems is presented. The considered constraints are minimum and maximum power generation of units, capacity of transmission lines and ramp rate limits. Genetic algorithm is used to solve a nonlinear objective function. Simulations are performed... 

In this paper, the operation of a future distribution network is discussed under the assumption of a multi-carrier microgrid (MCMG) concept. The new model considers a modern energy management technique in electricity and natural gas networks based on a novel demand side management (DSM) which the energy tariff for responsive loads are correlated to the energy input of the network and changes instantly. The economic operation of MCMG is formulated as an optimization problem. In conventional studies, energy consumption is optimized from the perspective of each infrastructure user without considering the interactions. Here, the interaction of energy system infrastructures is considered in the... 

Non-Convex Economic Dispatch (NED) has been addressed as an open and demanding optimization problem in power systems. Due to the fact that realistic ED problems have non-convex cost functions with equality and inequality constraints, conventional search methods are unable to effectively find the global solution. In recent years, because of their great potential to achieve optimal or close-to-optimal solution, meta-heuristic optimization techniques have attracted significant attention to tackle the complexity of NED problems. In this paper, an efficient approach is proposed based on Imperialist Competitive Algorithm (ICA). The proposed algorithm named multi-operator ICA (MuICA) merges the... 

Dynamic economic dispatch (DED) determines system generation schedule in a specified time interval to meet load demand at each hour while satisfying generation system constraints. DED considering valve-point effects is a non-convex optimization problem and therefore conventional mathematical methods fail to solve this problem. This paper presents a hybrid gradient search - near optimal search method to solve the DED problem considering valve-point effects of generating units. Local minima obtained by Gradient Search Method (GSM) are utilized by a novel Near Optimal Search (NOS) method to find the global optimum of the DED problem. The efficiency and feasibility of the proposed method and its... 

Generation scheduling is a crucial challenge in power systems especially under new environment of liberalization of electricity industry. This paper is focused on the economical aspect of UC problem, while the next load demand as a very important issue and prohibited operation zones and spinning reserve uncertainty as practical constraints have been taken in to account. The impacts of hot/cold start-up cost have been considered in this paper. Numerical results show a significant improvement in the solutions of a cost-based unit commitment in comparison with the other studies. © 2009 Praise Worthy Prize S.r.l  

The aim of this study is to show the effectiveness of prohibited operating zone. Generation scheduling is a crucial challenge in power systems especially under new environment of liberalization of electricity industry. This study is focused on the economical aspect of unit commitment problem. Since, the generating units may have certain ranges where operation is restricted based upon physical limitations of machine components or instability. Therefore, Prohibited Operating Zones (POZ) as a redundant constraint is considered, while the next load demand as a very important issue is deliberated. In this study generation scheduling of each hour is conducted by considering the next load demands... 

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and λ iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield neural network is more efficient and the time required for convergence is considerably smaller compared to classical methods. © 2006 IEEE  

This paper presents a new approach to economic dispatch (ED) problem with non-continuous and non-smooth cost functions using a hybrid evolutionary programming (EP) algorithm. In the proposed method the concept of multi-agent (MA) systems and EP are integrated together to form a new multi-agent evolutionary programming (MAEP) approach. In MAEP, an agent represents a candidate solution to the optimization problem in hand, and all agents live together in a global environment. Each agent senses its local environment, competes with its neighbors, and also learns by using its own knowledge. MAEP uses these agent-agent interactions and the evolutionary mechanism of EP to obtain the optimal... 

In this paper, a new approach based on hybrid Particle Swarm-Based- Simulated Annealing Optimization (PSO-B-SA) for solving thermal unit commitment (UC) problems is proposed. The PSO-B-SA presented in this paper solves the two sub-problems simultaneously and independently; unit-scheduled problem that determines on/off status of units and the economic dispatch problem for production amount of generating units. Problem formulation of UC is defined as minimization of total objective function while satisfying all the associated constraints such as minimum up and down time, production limits and the required demand and spinning reserve. Simulation results show that the proposed approach can... 

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and X iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield neural network is more efficient and the time required for convergence is considerably smaller compared to classical methods. © 2006 IEEE  

The usage of conventional fossil fuels has aided fast economic growth while also having negative consequences, such as increased global warming and the destruction of the ecosystem. This paper proposes a novel swarm-based metaheuristic method called Chimp Optimization Algorithm (ChOA) to tackle the environmental, economic dispatch issue and reducing the waste nonrenewable materials. In this regard, two objective functions named fuel cost function and emission cost function are proposed. Unique constrained handling also solves the challenge of multi-objective optimization. Standard IEEE 30 bus with six generators and a 10-unit system are used to demonstrate the usefulness of ChOA. The result... 

This paper presents a novel heuristic algorithm for solving economic dispatch (ED) problems, by employing iteration particle swarm optimization with time varying acceleration coefficients (IPSO-TVAC) method. Due to the effect of valve-points and prohibited operation zones (POZs) in the generating units' cost functions, ED problem is a non-linear and non-convex optimization problem. The problem even may be more complicated if transmission losses are taken into account. The effectiveness of the proposed method is examined and validated by carrying out extensive tests on three different test systems. Valve-point effects, POZs, ramp-rate constraints and transmission losses are modeled. Numerical... 

The objective of economic dispatch (ED) problem is minimizing the operating cost and finding the point where the total output of the generations equals the total power that must be delivered. In that point the incremental cost of power generation is also equal for all generators. Considering the presence of uncertainty and inaccuracy in the data, fuzzy set theory is an appropriate method to solve the economic dispatch problems. In this paper, a modified fuzzy economic dispatch is formulated to solve the problem under the competitive electricity market uncertainties. Also, available spinning reserve is optimally allocated to market participants. The formulated optimization problem it then... 

In order to generate adequate electricity energy, conventional power plants utilize dramatic volume of water resources. Different methods such as replacing cutting-edge technologies of facilities have been proposed to diminish water consumption in this industry. Most of the approaches are considered as medium or long-term solution which requires substantial investment costs. Meanwhile, because of the process and technology, natural gas-fired power plants need less water among conventional power plants. Therefore, shifting unit commitment planning toward these power plants would aid to save water consumption. Nevertheless, overlooking combined cycle power plants can perform negative impact on... 

Multiple energy carriers (MECs) have been broadly engrossing power system planners and operators toward a modern standpoint in power system studies. Energy hub, though playing an undeniable role as the intermediate in implementing the MECs, still needs to be put under examination in both modeling and operating concerns. Since wind power continues to be one of the fastest-growing energy resources worldwide, its intrinsic challenges should be also treated as an element of crucial role in the vision of future energy networks. In response, this paper aims to concentrate on the online economic dispatch (ED) of MECs for which it provides a probabilistic ED optimization model. The presented model... 

Dynamic economic dispatch (DED) aims to schedule the committed generating units' output active power economically over a certain period of time, satisfying operating constraints and load demand in each interval. Valve-point effect, the ramp rate limits, prohibited operation zones (POZs), and transmission losses make the DED a complicated, non-linear constrained problem. Hence, in this paper, imperialist competitive algorithm (ICA) is proposed to solve such complicated problem. The feasibility of the proposed method is validated on five and ten units test system for a 24 h time interval. The results obtained by the ICA are compared with other techniques of the literature. These results... 

Energy storage systems are expected as a near-term solution for renewable energy application in the residential energy hubs. Within this context, this study investigates the feasibility of using storage systems in improving the technical and financial performance of the residential renewable-based energy hub. A new approach has been proposed in this study in which economic dispatch problem has been formulated for an energy hub including both electrical and heat storage system. The proposed approach determines the optimal supply of energy demand and storage system operation to minimise the total energy cost of the hub. The economic benefit of storage system due to energy cost saving and...