Showing papers by "K. Shanti Swarup published in 2019"

A New Mixed Integer Linear Programming Formulation for Protection Relay Coordination Using Disjunctive Inequalities

Abstract: Numerical optimization-based solution to directional overcurrent relay (DOCR) coordination problem has been a widely addressed research problem in the recent past. Many linear (LP), nonlinear (NLP), mixed integer nonlinear (MINLP), mixed integer linear (MILP), and quadratically constrained quadratic programming (QCQP)-based formulations have been presented in the past literature. This paper proposes a new MILP-based formulation using disjunctive inequalities. The nonlinear DOCR protection coordination model is formulated as MILP by linearizing the bilinear terms existing in the original formulation. One of the variables in each bilinear term is discretized over its interval into a fixed number of steps. After assigning binary variables to each discrete interval, the resulting bilinear terms with binary variables are written in terms of disjunctive inequalities. The results have shown that the proposed MILP formulation fetch better optimal solutions compared with past MILP and MINLP formulations. The MILP problem is programmed in GAMS package with CPLEX solver and tested on standard 3 bus, 9 bus, 15 bus, and 30 bus systems and results are found to be satisfactory.

A Novel Convexified Linear Program for Coordination of Directional Overcurrent Relays

Abstract: A novel convexified linear program for optimal directional overcurrent relay (DOCR) coordination problem (CP) is proposed in this letter. The DOCR CP is a highly constrained nonlinear nonconvex problem which was solved using various traditional and heuristic optimization techniques in the past. In this letter, the CP is formulated as a linear programming problem without fixing the current pickup settings of DOCRs. The bilinear terms in the proposed formulation are written in the form of linear inequalities using McCormick envelopes. A sequential tightening algorithm is used to update the boundary limits of each parameter based on the solution obtained in each iteration, thus tightening the convex hulls and leading to solutions near to global optimum. The performance of the proposed method is applied to various test systems among which the results of three bus test system are presented.

Wide area oscillation damping controller for DFIG using WAMS with delay compensation

Abstract: Several studies have reported the improvement of system stability with a doubly-fed induction generator (DFIG) based wind turbines. Due to the remote location of DFIG, the local signals measured may not contain the complete oscillation information of the power system. This study describes an optimisation enabled wide area damping control (WADC) for DFIG to mitigate both local and inter area oscillations. Wide area measurement systems (WAMSs) which include phasor measurement units and synchrophasors are used for a centralised controller for damping inter-area and local oscillatory modes. The proposed damping controller parameters are optimised along with the local power system stabiliser settings for maximising the impact on system modal damping. The challenging shortcoming of WAMS based controller is the variable communication latency which can adversely affect the controller if not accounted in the controller design process. The proposed WADC algorithm addresses this issue and compensates for the delayed and time stamped error signals. The variable latencies are normalised in the optimisation algorithm in the design of controller parameters. The proposed algorithm is verified with transient simulation in PSCAD/EMTDC for the most severe three-phase faults. A set of comprehensive case studies are performed to analyse the effectiveness of the proposed algorithm for the noisy, delayed communication signals.

Coordinated reactive power and crow bar control for DFIG-based wind turbines for power oscillation damping:

Abstract: The fault ride through capability and fast controller action makes doubly fed induction generator based wind energy conversion system to actively participate in power oscillation damping. This arti...

Demand Response Based on Utility Function Maximization Considering Time-of-Use Price

Abstract: In smart grid, demand side management is the main component that adapts elastic demand to fluctuating generations. Classical demand theory is a branch of microeconomics and it is about the study of consumer demand in the context of a market economy. Important tools in this theory are utility functions and two constraints i.e., physical and budget constraint. In this paper, two models for demand response are analyzed based on the well known Cobb-Douglas utility function. Both models maximize their utility subjected to different constraints. The result shows the effectiveness of the models for different values of elasticity parameter.

An intelligent methodology to improve distribution system operational parameters utilising smart inverter functionalities of PV sources

Abstract: The addition of distributed PV sources to low voltage distribution networks instigate issues to various operational parameters of the network. With modern smart inverters having controllable settings for voltage and power injection these issues can be alleviated. An Intelligent method utilising smart inverter functionalities of a PV source in a distribution network is proposed in present work to minimise, the power import from the grid, reduce network losses and minimise the magnitude of voltage violation. The optimal settings depend on load and generation variables. In order to reduce computational complexity, a scenario-based method is used to handle these stochastic components in the system. A Non-Sorted Genetic Algorithm (NSGA) is used for optimising the smart inverters parameters. The proposed scheme is envisaged to be realised by a Distribution Management System (DMS) which measures and coordinates all the smart inverters within the distribution feeder.