S. Hemamalini

Artificial Bee Colony Algorithm for Economic Load Dispatch Problem with Non-smooth Cost Functions

Abstract With the depletion of coal and increasing fuel prices, a proper schedule of available generating units may save millions of dollars per year in production cost. In this article, the artificial bee colony algorithm and optimization technique based on the foraging behavior of honeybees is proposed for solving economic load dispatch problems with non-smooth cost functions exhibiting valve-point effect, prohibited operating zones, multiple fuel options, and ramp rate limits. The effectiveness of the proposed algorithm is demonstrated on test cases consisting of 10, 13, 15, and 40 generating units with non-linearities incorporated in their cost functions. The results of the proposed technique are compared with that of other techniques reported in the literature. The results substantiate that the proposed algorithm is capable of yielding quality solution.

Emission constrained economic dispatch with valve-point effect using particle swarm optimization

This paper presents particle swarm optimization (PSO) technique to solve economic dispatch of valve-point loaded generating units considering emission constraint. This problem has gained recent attention due to the deregulation of power industry and environmental regulations. Minimizing operating cost can no longer be the only criterion for dispatching electric power due to increasing concern over the environmental consideration. In this paper, fuel cost and NOx emission functions are considered and formulated as a single objective optimization problem. Based on the literature survey, it could be found that cost function is taken as a quadratic function and solved for emission economic dispatch. Here, in cost function a sine term is added to model the valve-point effect and then solved using PSO algorithm. The objective function is highly non-linear and the proposed method is validated with IEEE 30-bus system. The results obtained demonstrate the effectiveness of the proposed method for solving the environmental constrained economic dispatch problem.

Dynamic Economic Dispatch with Valve-Point Effect Using Maclaurin Series Based Lagrangian Method

Dynamic Economic Dispatch (DED) plays a vital role in power generation, operation and control. It is a complicated, non-linear constrained problem. In this paper, Maclaurin series based Lagrangian method (MSL) is used to solve the DED problem for generating units with valve-point effect, considering the ramp rate limits. Using Maclaurin series, the sine term used to model the valve-point effect is expanded and solved with Lagrangian method. The feasibility of the proposed method is validated for static economic dispatch problem for forty unit system and DED problem for five unit test system for 24 hour time interval. Results obtained with the proposed approach are compared with other techniques in the literature. The results obtained substantiate the applicability of the proposed method for solving static and dynamic economic dispatch problems with non-smooth cost functions.

Prims-Aided Dijkstra Algorithm for Adaptive Protection in Microgrids

Decentralization of electric power is possible with the penetration of distributed generators (DGs) in the microgrid (MG) network. Reconfiguration of MG poses a key challenge in identifying suitable protection schemes for varying the topology of the network. In this paper, a central protection center (CPC) is incorporated whose function is to monitor the MG continuously, identify fault occurrence, and locate the exact faulted branch. The proposed Prim-aided Dijkstra algorithm executed continuously in the CPC is responsible for identifying the current topology of the network and aids in identifying the shortest route from the faulted point to the nearest operating source. The CPC is also responsible for adaptively varying the settings of the relays existing in the shortest path identified based on their selectivity levels. This heuristic algorithm is validated on IEEE 21-bus and 40-bus MG test systems for all possible topologies and faults. The proposed algorithm is capable of clearing the fault by disconnecting minimum portion of the network and ensuring continuity of supply to a majority of loads.

Emission constrained economic dispatch with valve-point effect using Maclaurin series-based Lagrangian method

This paper presents Lagrangian-based technique to solve economic emission load dispatch (EELD) of valve-point loaded generating units considering emission constraint. The EELD problem has gained recent attention due to the deregulation of power industry and environmental regulations. In this paper, two conflicting functions (fuel cost and emission) are considered and formulated as a single objective optimisation problem by the weighted sum method. Based on the literature survey, it is found that cost function is taken as a quadratic function and solved for emission economic dispatch. Here, in cost function, a sine term is added to model the valve-point effect and an exponential term is used to model the emission function. Using Maclaurin series, the sine and exponential terms are expanded and solved with Lagrangian multiplier method. The objective function is highly non-linear and the feasibility of the proposed method is validated with IEEE 30-bus system and ten-unit system. Results obtained with the proposed approach are compared with genetic algorithm.

Artificial Immune based Economic Load Dispatch with valve-point effect

Economic load dispatch (ELD) is one of the optimization problems in power systems. Economic Load Dispatch determines the electrical power to be generated by the committed generating units in a power system so that the total generation cost of the system is minimized, while satisfying the load demand simultaneously. In this paper Artificial Immune System (AIS) optimization approach has been applied to solve the constrained Economic Load Dispatch with valve-point effect. The developed AIS based optimization technique used total cost of generation as the objective function and represented it as the affinity measure. For illustrative purposes, the proposed AIS based technique has been applied to various test cases (consisting of 3, 13 and 40 generating units) to validate its effectiveness. The developed AIS based optimization technique (both binary coded and decimal coded) has been thoroughly investigated by varying the population size. The results of the proposed AIS based optimization technique are compared with that of genetic algorithm (GA) based approach. The simulation results reveal that the developed technique is easy to implement and capable of finding feasible near global optimal solution. The results substantiate the robustness, fast convergence and efficiency of the proposed methodology.

Adaptive and Intelligent Controller for Protection in Radial Distribution System

In this paper, a Field Programmable Gate Array (FPGA) based intelligent controller for overcurrent (OC) protection of a radial distribution system is realized. This controller monitors the radial distribution network continuously and when a fault is detected in the network, the FPGA based adaptive and intelligent controller performs the OC relay coordination and trips the appropriate circuit breakers of the system. The FPGA based digital prototype relay for overcurrent protection is realized with Atlys Digilent Spartan-6 FPGA kit. The performance of the FPGA based overcurrent protection technique for a 4-bus radial distribution system is compared with that of the conventional dual simplex algorithm. The proposed FPGA based overcurrent protection algorithm is also tested for an IEEE 33-bus radial distribution network.

Prims Aided Floyd Warshall Algorithm for Shortest Path Identification in Microgrid

Reconfiguration of microgrid results in dynamic variation in topology of the network. Due to this, the conventional protection scheme is no longer applicable in microgrid. Hence the microgrid network demands an adaptive protection scheme, which is a key challenge to protection engineers. It is critical for the protection engineers to know the current topology of the microgrid before a suitable relay coordination technique is deployed on it. This paper proposes a Prims aided Floyd Warshall algorithm, where the Prims algorithm identifies the current topology of the network at any instant of time. In the event of fault occurrence, the output of Prims algorithm is a list of active nodes: utility grid, loads, Distributed Generators (DG) and critical circuit breakers in the network. This list aids the Floyd Warshall algorithm in identifying the shortest path from the node closer to the fault to the utility grid (in grid connected mode) or point of common coupling (in islanded mode). The algorithm ensures minimum portion of network disconnection for fault isolation. The proposed algorithm is tested and validated on an IEEE 21-bus microgrid network in islanded mode and an IEEE 69-bus distribution network with DG included at certain nodes in grid connected mode.

Communication Assisted Overcurrent Protection of Microgrid

An intelligent micro grid controller system with over current protection capability in both the grid-connected and the islanded modes of operation is proposed. To achieve the above strategy a model of small portion of distribution network as if it were a micro grid will be developed and considered. The processor based relays that provide over current protection functions in addition to performing control, measurement, and communication functions will be suitably employed.

Multiple DG Synchronization and De-synchronization in a Microgrid Using PLC

Microgrid is an aggregate of generating units and loads at the distribution level. It operates in two modes: Grid connected mode and Islanded mode. Power continuity is very essential for critical loads in microgrid and maybe achieved vide 100 % standby diesel generator sets in a microgrid network. This paper considers a real time 24/7 Information Technology (IT) campus where even a very short power break will lead to huge commercial loss. Hence it is very important to bring the standby power during the utility power failure. This is achieved through multiple diesel generator sets synchronized in a single panel through a proper sequential logic vide programmable logic controller (PLC). In the event of fault occurrence, based on the receipt of signals from the respective relays, the PLC identifies the fault and issues appropriate tripping commands to the microgrid to safely isolate the fault. The significance of neutral isolating contactor (NIC) and neutral grounding resistor (NGR) in microgrid protection is also analyzed.