Energy Control Center Research Articles

Cyber Inference System for Substation Anomalies Against Alter-and-Hide Attacks

Alarms reported to energy control centers are an indication of abnormal events caused by either weather interruptions, system errors, or possibly intentional anomalies. Although these initiating events are random, e.g., faults on transmission lines struck by lightning, the existence of electronically altered measurements may implicate the process to identify root causes of abnormal events. This paper is concerned with alter-and-hide (AaH) attacks by tampering the actual measurements to normal states with the background of disruptive switching actions that hide the true values of local events from operators at the control center. A cyber inference system framework is proposed to synthesize all sequential, missing, or altered alarms of related substations against AaH attacks. The stochastic nature of such attack events is modeled with probabilities as an integer programming problem with multiple scenarios. The proposed method is utilized to verify alarm scenarios for a conclusion of the potential AaH attacks on the substations.

Intelligent Energy Control Center for Distributed Generators Using Multi-Agent System

This paper presents the modeling of intelligent energy control center (ECC) controlling distributed generators (DGs) using multi-agent system. Multi-agent system has been proposed to provide intelligent energy control and management in grids because of their benefits of extensibility, autonomy, reduced maintenance, etc. The multi-agent system constituting the smart grid and agents such as user agent, control agent, database agent, distributed energy resources (DER) agent work in collaboration to perform assigned tasks. The wind power generator connected with local load, the solar power connected with local load and the ECC controlled by fuzzy logic controller (FLC) are simulated in MATLAB/SIMULINK. The DER model is created in client and ECC is created in server. Communication between the server and the client is established using transmission control protocol/internet protocol (TCP/IP). The results indicate that the controlling of DER agent can be achieved both from server and client.

Current State of Energy Consumption and Countermeasures of Energy Saving for Iron and Steel Industry in China

In this paper, we find that factors which affect energy consumption are steel ratio coefficient and process energy consumption by analyzing energy consumption of every process in integrated steel works. On this basis we point out the main reason for the high energy consumption of iron and steel industry in China is that integrated steel works examine the production process without system energy saving ideas. Therefore we propose the countermeasures of energy saving in iron and steel industry in China in aspects of energy management and control center, iron-making system, steel-making system, steel rolling system, as well as secondary energy recovery, which is aimed at providing a way for energy saving and emissions reduction of iron and steel industry in China.

Intergrid: A Future Electronic Energy Network?

Anticipated widespread usage of new power electronics technologies in electrical energy generation and consumption is expected to provide major efficiency improvements, while the deployment of smart grid technologies should improve the utilization and availability of electricity. This paper explores possible relationships between these two trends. Starting from an analysis of current and expected trends in the generation, transport, and consumption of electrical energy, this paper contemplates possible future ac and dc electronic power distribution system architectures, especially in the presence of renewable energy sources. The proposed nanogrid-microgrid-Ě-grid structure achieves hierarchical dynamic decoupling of generation, distribution, and consumption by using bidirectional electronic power converters as energy control centers. Several possible directions for modeling, analysis, and system-level design of such systems, including power flow control, protection, stability, and subsystem interactions, are briefly discussed.

Communications in Smart Grid: A Review with Performance, Reliability and Security Consideration

Moving from legacy power grid systems to Smart Grid (SG) is becoming a priority of many countries and energy service providers. One of the main enabler of a SG infrastructure is having the proper communication network to support its various functionalities and requirements. This paper introduces a communication framework which can be used to integrate the various data communication entities in a Smart Grid environment going from sensors at the consumer’s premises to the energy service provider command and control center. The paper provides a brief overview and discusses the various communication technologies and protocols which can be utilized for such purpose and shows potential scenarios which can be used. Network reliability, performance and overall security considerations are also discussed within the given context.

Robust, fast and optimal solution of practical economic dispatch by a new enhanced gradient‐based simplified swarm optimisation algorithm

Nowadays, the rising concern about the costs of fuel and operation of generating units in the energy control centre deserve progress of solution methodologies for the practical economic dispatch (ED) problems. ED aims to schedule the committed units’ output power while satisfying practical constraints and load demand. The generator ramp rate limits, non-convex and discontinuous nature of prohibited operating zones, non-smooth characteristic of valve-point effects, multi-fuel type of generation units, transmission line losses and the large number of units in practical power plants make this problem very hard to solve. In this study, a new solution method of integrating the classical gradient-based optimisation technique and a new enhanced simplified swarm optimisation algorithm is comprehensively presented and successfully applied to determine the feasible, robust, fast and globally or near-globally optimal solution within a rapid timeframe for the ED problems. The simulations are carried out on four-test systems, including 10-, 15-, 40- and 80-units using the proposed optimisation technique in the Fortran Power Station 4.0 software. The current proposal outperforms other methods showcased in the recent state-of-the art literature in the area.

State estimation in power systems using linear model infinity norm‐based trust region approach

State estimation is one of the most important functions in an energy control centre. An computationally efficient state estimator which is free from numerical instability/ill-conditioning is essential for security assessment of electric power grid. Whereas approaches to successfully overcome the numerical ill-conditioning issues have been proposed, an efficient algorithm for addressing the convergence issues in the presence of topological errors is yet to be evolved. Trust region (TR) methods have been successfully employed to overcome the divergence problem to certain extent. In this study, case studies are presented where the conventional algorithms including the existing TR methods would fail to converge. A linearised model-based TR method for successfully overcoming the convergence issues is proposed. On the computational front, unlike the existing TR methods for state estimation which employ quadratic models, the proposed linear model-based estimator is computationally efficient because the model minimiser can be computed in a single step. The model minimiser at each step is computed by minimising the linearised model in the presence of TR and measurement mismatch constraints. The infinity norm is used to define the geometry of the TR. Measurement mismatch constraints are employed to improve the accuracy. The proposed algorithm is compared with the quadratic model-based TR algorithm with case studies on the IEEE 30-bus system, 205-bus and 514-bus equivalent systems of part of Indian grid.

Grid-Interface Bidirectional Converter for Residential DC Distribution Systems—Part One: High-Density Two-Stage Topology

With the emerging installations of multitype renewable energy sources and energy storage elements, the dc electronic distribution systems in residential buildings (dc nanogrid) are becoming an alternative future system solution, achieving a zero net-energy consumption and optimized power management. The concept of the energy control center (ECC), which interconnects the dc system to the traditional ac utility grid, is introduced, and the operation function of ECC converter suitable for dc nanogrid application is defined. This paper investigates a two-stage topology using a full bridge in series with a bidirectional synchronous rectifier dc–dc converter as a single-phase ECC for dc nanogrid, with a significant reduction of the dc-link capacitor value. The operation analysis and the design of passive components are provided. A bidirectional control system and the design process are also presented in terms of the system requirement and the small dc-link capacitor.

Grid-Interface Bidirectional Converter for Residential DC Distribution Systems—Part 2: AC and DC Interface Design With Passive Components Minimization

With the emerging installations of multitype renewable energy sources and energy storage elements, the dc electronic distribution systems in residential houses/buildings (dc nanogrid) are becoming an alternative future system solution, achieving a zero net-energy consumption and optimized power management. One of the critical components in such a dc system is the grid-interface bidirectional ac–dc power converter, namely the energy control center. Besides, the basic power conversion function, the system interface solution in grid-interface converter is important to successfully interconnect the ac and dc systems as well as fulfill the power quality and EMI regulation codes on both dc and ac sides. This paper presents a complete discussion of several aspects of system interface design for the grid-interface converter under both single-phase and three-phase system conditions. A passive plus active filter solution is proposed to accomplish the common-mode-related noises minimization as well as a dramatic reduction of the converter system volume.

An improved bacterial foraging algorithm for combined static/dynamic environmental economic dispatch

Economic dispatch is carried out at the energy control center to find out the optimal output of thermal generating units such that power balance criterion is met, unit operating limits are satisfied and the fuel cost is minimized. With growing environmental awareness and strict government regulations throughout the world, it has become essential to optimize not only the total fuel cost but also the harmful emissions, both, under static as well as dynamic conditions. The static environment economic dispatch finds the optimal output of generating units for a fixed load demand at a given time, while the dynamic environmental economic dispatch schedules the output of online generators with changing power demands over a certain time period (normally one day) so as to minimize these two conflicting objectives, simultaneously. In this paper, the price penalty factor approach is employed for simultaneous minimization of cost and emission. The generator ramp rate constraints, non-convex and discontinuous nature of cost function and the large number of generators in practical power plants, make this problem very difficult to solve. Here, a fuzzy ranking approach is employed to identify the solution which offers the best compromise between cost and emission objectives.This paper proposes an improved bacterial foraging algorithm (IBFA) in which a parameter automation strategy and crossover operation is used in micro BFA to improve computational efficiency. The performance of IBFA is compared with classical BFA and with previously published literature on four standard test systems and is found to be better.

Genetic algorithm based reactive power dispatch for voltage stability improvement

Voltage stability assessment and control form the core function in a modern energy control centre. This paper presents an improved Genetic algorithm (GA) approach for voltage stability enhancement. The proposed technique is based on the minimization of the maximum of L-indices of load buses. Generator voltages, switchable VAR sources and transformer tap changers are used as optimization variables of this problem. The proposed approach permits the optimization variables to be represented in their natural form in the genetic population. For effective genetic processing, the crossover and mutation operators which can directly deal with the floating point numbers and integers are used. The proposed algorithm has been tested on IEEE 30-bus and IEEE 57-bus test systems and successful results have been obtained.

On-line security monitoring and analysis using Levenberg-Marquardt algorithm-based Neural Network

Due to open access in the restructured power system, the events of bus voltage limit violation and transmission line overloading are occurring frequently. These events are mainly responsible for several incidents of major network collapses leading to partial or even complete blackouts and due to this, security monitoring and analysis has become a challenging task to be performed at energy control centre. A fast and accurate method of Power Flow (PF) study may be able to investigate the system security by determining the power system static states, i.e. voltage magnitude and voltage angle at each bus. In this paper, a Levenberg-Marquardt algorithm-based Neural Network (LMNN) has been proposed which provides a fast learning to the multi-layer neural network. The effectiveness of the proposed LMNN-based approach for security monitoring and analysis has been demonstrated by computation of bus voltage magnitudes and voltage angles for line-outage contingencies at different loading conditions in IEEE 14-bus system.

Fuzzy Expert Approach with Curtailed Controllers for Improved Reactive Power Dispatch

This paper addresses the problem of curtailing the number of control actions using fuzzy expert approach for voltage/reactive power dispatch. It presents an approach using fuzzy set theory for reactive power control with the purpose of improving the voltage profile of a power system. To minimize the voltage deviations from pre-desired values of all the load buses, using the sensitivities with respect to reactive power control variables form the basis of the proposed Fuzzy Logic Control (FLC). Control variables considered are switchable VAR compensators, On Load Tap Changing (OLTC) transformers and generator excitations. Voltage deviations and controlling variables are translated into fuzzy set notations to formulate the relation between voltage deviations and controlling ability of controlling devices. The developed fuzzy system is tested on a few simulated practical Indian power systems and modified IEEE-30 bus system. The performance of the fuzzy system is compared with conventional optimization technique and results obtained are encouraging. Results obtained for a modified IEEE-30 bus test system and a 205-node equivalent EHV system a part of Indian southern grid are presented for illustration purposes. The proposed fuzzy-expert technique is found suitable for on-line applications in energy control centre as the solution is obtained fast with significant speedups with few number of controllers.

Real time loss sensitivity calculation in power systems operation

Network losses are being considered in the standard market design. The calculation of loss sensitivity that is based on the distributed generator slack is commonly used for economic dispatch in energy control center. In order to obtain the accurate location-based marginal prices, an efficient and robust method to calculate loss sensitivity for an arbitrary slack bus within the real-time period (1–10 min) is needed in the real-time energy markets. This paper presents a fast and useful approach to calculate loss sensitivity for any slack bus. This method is based on the results taken from the distributed slack buses without repeating a traditional power flow analysis. The proposed approach is tested and verified.

Integrated Software Platform to Teach Different Electricity Spot Market Architectures

Electricity spot market architectures have rapidly evolved; their understanding, behavior, and redesign can be guided with the help of integrated simulation platforms. This paper presents a software platform for the integrated short-term simulation of different energy spot market architectures. The simulator considers three different architectures: i) decentralized spot markets (the separated market and system operator approach), ii) centralized spot markets (whose basis is a unit commitment model for competition in the generation side), and iii) hybrid spot market architectures (that operate under a single operator and avoid unit-commitment complexities including demand response and bilateral contracts). The software platform integrates tools for data management and display as well as available solvers for mathematical programming problems. The platform is intended and has successfully been used to teach electricity market courses at undergraduate and graduate levels at Morelia Institute of Technology in Mexico, and also in several special diploma programs on electricity markets to more than a hundred engineers from the national energy control center and the energy regulatory commission in Mexico as well as five different system/market operators of the central American countries.

Anticipatory load shedding scheme for loadability enhancement

The paper presents a new anticipatory load shedding protection scheme implemented centrally from the energy control centre for loadability enhancement. Most of the schemes available in literature for this purpose are based on information at the current operating condition which are blind to load increase scenarios and the associated switchings in voltage controlled buses. The proposed scheme anticipates the danger of voltage instability in a time frame of interest by incorporating these effects. If the normal controls are exhausted, the algorithm based on successive application of LP restricts/sheds the required amount of low priority loads in advance so that the power system survives the voltage instability threat even during the worst power system period. Results for IEEE 30 bus and an Indian 91 bus power systems have been obtained to demonstrate the effectiveness of the proposed algorithm.

A new and fast technique for voltage stability analysis of a grid network using system voltage space

The relative positions of the bus voltage phasors in the voltage space of a system depend on the characteristics of, and the power flow in, the transmission network. When the voltage space of the system is examined with respect to the “centroid” of the system voltage space, it is possible to identify the loadability of buses and rank them accordingly. (The term centroid is used owing to the lack of a better word.) A technique based on concepts applied to equilibrium analysis of rigid bodies is developed to determine the centroid voltage of the system voltage space and centroid voltage of the generator voltage space. The relative positions of the bus voltage phasors with respect to the centroid voltage of the system voltage space and centroid voltage of the generator voltage space are used to identify and compute a voltage stability index for the load buses in the system. This technique is compared with three other techniques proposed in the literature. The relative merits of all the techniques are discussed and sample results are provided. The results indicate that the proposed technique is simple, reliable and fast, requiring only the examination of the system voltage space with respect to the centroid voltages. The proposed technique is ideally suited for on-line EMS applications in an Energy Control Centre as it requires only the output of the state estimator.

98/00383 High power factor correction circuits with space vector and hysteresis control methods

This paper presents a prototype of an expert system for monitoring and improving steady state voltage stability in power systems. The monitoring methodology is based on the L-index of load buses (Kessel and Glavitsch, IEEE Transactions, 1986, PWRD-1(3), 346–354). This index uses information on a normal load flow and is in the range from 0 (no load on the system) to 1 (voltage collapse). The control against voltage collapse is based on reducing the magnitude of the L-indices of the critical nodes for a given system operating condition based on heuristic criteria. The control variables considered are switchable VAR compensators, OLTC transformers and generators excitation. The proposed expert system technique has been tested under simulated conditions on a few practical Indian power systems. The performance of the expert system is compared with conventional optimization technique and concurrent results have been obtained. The proposed expert system technique is found to be suitable for on-line application in an Energy Control Center for voltage stability improvement as the solution is obtained fast, with a minimum of numerical computations. Results obtained for a 24 node EHV Indian power network and a modified IEEE 30 bus system are included for illustration purposes.

An expert system for power system voltage stability improvement

This paper presents a prototype of an expert system for monitoring and improving steady state voltage stability in power systems. The monitoring methodology is based on the L-index of load buses ( Kessel and Glavitsch, IEEE Transactions, 1986, PWRD-1(3), 346–354). This index uses information on a normal load flow and is in the range from 0 (no load on the system) to 1 (voltage collapse). The control against voltage collapse is based on reducing the magnitude of the L-indices of the critical nodes for a given system operating condition based on heuristic criteria. The control variables considered are switchable VAR compensators, OLTC transformers and generators excitation. The proposed expert system technique has been tested under simulated conditions on a few practical Indian power systems. The performance of the expert system is compared with conventional optimization technique and concurrent results have been obtained. The proposed expert system technique is found to be suitable for on-line application in an Energy Control Center for voltage stability improvement as the solution is obtained fast, with a minimum of numerical computations. Results obtained for a 24 node EHV Indian power network and a modified IEEE 30 bus system are included for illustration purposes.

An expert system for alleviation of network overloads

This paper presents a prototype of an expert system for alleviation of network overloads in the day-to-day operation of a power system. The expert system provides a solution in real time for network overload alleviation using phase shifting transformers, and if overload still persists by rescheduling generation and/or load curtailment. The knowledge base of the expert system is obtained by carrying out extensive off-line analysis. An operational load flow (OLF) algorithm is used in the off-line analysis which incorporates a more realistic representation of the generator model and load characteristics. The off-line analyses are carried out using sensitivity factors (phase shifter distribution factors, generation shift sensitivity factors) and a linear programming (LP) optimization technique. The performance of the expert system is compared with the conventional LP optimization method of network overload alleviation and concurrent results have been obtained. The proposed expert system has been tested with the simulated conditions of a few practical Indian power systems. Results obtained for two Indian power networks of 24 nodes and 82 nodes are presented for illustration purpose. The expert system is found suitable for application in Energy Control Center as the solution is obtained very fast with a minimum of numerical computations.