Top PDF Real-Time Load-Side Control of Electric Power Systems

Real-Time Load-Side Control of Electric Power Systems

Real-Time Load-Side Control of Electric Power Systems

C h a p t e r 3 LOAD-SIDE FREQUENCY CONTROL IN MULTI-MACHINE NETWORKS Not all power systems are tightly electrically coupled, and therefore have coherent frequency and can be modeled as single-machine systems as in Chapter 2. In the current chapter, we study load-side frequency control in a multi-machine power network, where different nodes may have different frequencies. Under a linearized power network model, we develop decentralized load-side primary frequency control by exploiting power network dynamics as part of a primal-dual algorithm that solves an optimal load control (OLC) problem. Such a control scheme rebalances power and stabilizes frequency after a change in generation or load, in a manner that minimizes total disutility for load control. We then extend controller design and stability analysis to the case with a nonlinear power flow model and generator dynamics and control. We also design and analyze stability of distributed secondary frequency control which, using local frequency and power flow measurements and communication between neighboring nodes, can restore frequency and inter-area power flows to their nominal values. Moreover, we design a completely decentralized frequency integral control that restores frequency to its nominal value and ensures global convergence of the system, and a distributed averaging-based PI control that makes the system locally asymptotically stable at an OLC solution.
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EH2741 Communications & Control in Electric Power Systems

EH2741 Communications & Control in Electric Power Systems

Overview Control and operation of power systems is a very large and comprehensive topic including many different fields ranging from power system instrumentation to power system modelling and control systems theory. The information and control systems needed to operate the power sytem, are so tightly integrated with the physical power system, together they constitute a cyber-physical system.

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Scenario- and Optimization-Based Control of Marine Electric Power Systems

Scenario- and Optimization-Based Control of Marine Electric Power Systems

conditions, other problems occur, such as sooting, increased maintenance because of extra running hours, and inefficiency of some NO X reduction systems at low temperatures (Realfsen; 2009). The analysis proposed in this chapter can also be used as a decision- support tool for the optimal configuration of a vessel. Several configurations can be simulated to evaluate the safety and performance of each configura- tion. Today, an automatic start and stop table is typically used for commit- ment of generators on marine vessels (Ådnanes; 2003). Generator sets are started if the power demand is above a threshold for a certain duration of time, vice versa for disconnection. An optimized load-dependent start table was derived in Radan et al. (2005), where the table was optimized with re- spect to fuel consumption and constrained by a safety requirement, so that disconnection of a generator will not lead to blackout. Algorithms to opti- mize the load-dependent start and stop tables are also presented in Radan et al. (2006), based on the probability for each operational mode of the vessel. One of the problems with a start and stop table is its independence of operation. For diving and drilling vessels, the safety and redundancy requirements are much higher during operation than during transit. How- ever, when using a start and stop table both operations will typically have the same configuration when the power demand is similar, even though this is not optimal. Therefore, some vessels have different start/stop tables for each mode and also a minimum number of generator sets for some modes to handle changing requirements. It is also common to override the automatic system by committing generators manually. For onshore and island power grids, multiple studies have looked into unit commitment, e.g., Contaxis and Kabouris (1991); Dillon et al. (1978); Dokopoulos and Saramourtsis (1996); Juste et al. (1999); Lowery (1966); Senjyu and Shimabukuro (2003).
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A Bio-Inspired Multi-Agent System Framework for Real-Time Load Management in All-Electric Ship Power Systems

A Bio-Inspired Multi-Agent System Framework for Real-Time Load Management in All-Electric Ship Power Systems

3. LITERATURE REVIEW AND PROBLEM FORMULATION 3.1 Introduction This chapter discusses the operations of isolated power systems, which include three levels – primary control, secondary control, and tertiary control. The real-time load management is defined as a secondary control problem. The load management methods for large power systems are reviewed. Most of existing methods aims to balance the generation and load while achieving certain objectives. The decision time step for these methods is on the order of minutes to hours, and the detail load and system dynamics are not included in the load management problem. However, all-electric ship power systems have faster dynamics and include large portions of nonlinear loads and dynamics loads, which require a smaller decision time step. Moreover, pulse loads in all-electric ship power systems draw a large amount of power in an intermittent way. Thus, the loads in the system need to be dynamically regulated to achieve the generation and load balancing in real time while satisfying various operational constraints of the system.
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Smart-Grid Based Real-Time Load Management Methodology for Power Deficient Systems

Smart-Grid Based Real-Time Load Management Methodology for Power Deficient Systems

Abstract—We are proposing a load shedding system for future smart cities which can shed load on priority basis. The proposed methodology has the potential to conserve the available energy in an efficient manner and making system immune to intense blackouts and brownouts. The objective is to keep end-user with more reliable and increased power availability and hence keeping higher priority load connected. Load is categorized in flexible manner to provide freedom of priority demarcation. The proposed system consists of two basic controllers: Central Load Manager (CLM) and Local Load Manager (LLM). CLM through sensor receives the real time load demand data, check for its value against threshold power and takes decision accordingly. Control signals are then transmitted to local load manager using TCP/IP technology which acts to shed the load and keeps condition of load (data) in the memory. An extensive simulation environment is developed in SIMULINK-MATLAB and tested under diverse conditions to analyze system’s performance and practicality.
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Reliable and Robust Cyber-Physical Systems for Real-Time Control of Electric Grids

Reliable and Robust Cyber-Physical Systems for Real-Time Control of Electric Grids

To investigate the effects of cyber-contingency on power system operations, a co-simulation model, based on information flow, is proposed in [164]. The authors model the network contingencies at a low level, e.g., delayed, disordered, dropped, and distorted information flows. The authors claim that these low-level parameters are easier to model than high-level network parameters such as denial-of-service and man-in-the-middle attacks. In contrast to this work, where they simulate the communi- cation network with these low-level parameters, T-RECS emulates the communication network by using Mininet, which enables us to study the effects of different network bandwidths, losses, and delays corresponding to multiple real-world scenarios. As mes- sage exchanges are emulated in T-RECS, it accurately captures the real-time properties of the control protocol. Another important distinction of this work with T-RECS is that, in [164], the decision-making layer, i.e., software agents, is also simulated, whereas T-RECS can run the real software agents without requiring the development of models of software agents.
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[T.J.E.miller] Reactive Power Control in Electric Systems

[T.J.E.miller] Reactive Power Control in Electric Systems

In developing the concept of the ideal compensator as used for factor correction or for voltage regulation, we have modeled the either as a controllable source of reactive power or as a reactive device with a constant-voltage control characteristic. Although the models are ultimately equivalent, the one may be more convenient or more illuminating in a given application than the other. In considering unbalanced loads it is helpful to begin by modeling both the load and the compensator in terms of their admittances and impedances. In taking this point of view, as indeed throughout this section, we shall follow the excellent paper 'by Gyugyi, Otto and to which the reader should refer for greater detail. The analysis will be made sufficiently gen- eral to include power-factor correction at the same time, because this helps to preserve continuity with the earlier analysis. More importantly, the simultaneous treatment of phase balancing and power-factor correc- tion in terms of and compensator admittances leads to a fundamental view of load compensation which is different from the aspects developed so far and which gives further insight into the nature of the problem.
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Real Time Control Strategy for Hybrid Electric Vehicles

Real Time Control Strategy for Hybrid Electric Vehicles

Based on the complex structure of electric hybrid car and uncertainty in driving force structure of electric hybrid car, different strategies have been presented for optimal management of energy based on smart methods. In this study by the decision making nature of fuzz logic, a movement map for Parallel Hybrid Electric Vehicle (PHEV) is made based on the required path. In a parallel hybrid car, recharging control of battery and auxiliary torque of electric engine are used as the key points of movement. Based on the disadvantages of pure electric car, to increase the life of battery and its easy use, we need a movement strategy balancing the battery charge for a movement path. If the battery is charged at no load by the combustion engine, NOx emission is increased and the battery charge is not good and adequate for HEV performance under no-load condition by the energy retrieval power and combustion engine.
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Electric Space Heating Scheduling for Real-time Explicit Power Control in Active Distribution Networks

Electric Space Heating Scheduling for Real-time Explicit Power Control in Active Distribution Networks

‡ Distributed Energy Systems Laboratory (DESL), Ecole Polytechnique Federale de Lausanne, Route Cantonale, 1015 Lausanne, Switzerland. email: {lorenzo.reyes, mario.paolone}@epfl.ch. Abstract—This paper presents a systematic approach for abstracting the flexibility of a building space heating system and using it within a composable framework for real-time explicit power control of microgrids and, more in general, active distribu- tion networks. In particular, the proposed approach is developed within the context of a previously defined microgrid control framework, called COMMELEC, conceived for the explicit and real-time control of these specific networks. The designed control algorithm is totally independent from the need of a building model and allows exploiting the intrinsic thermal inertia for real-time control. The paper first discusses the general approach, then it proves its validity via dedicated simulations performed on specific case study composed by the CIGRE LV microgrid benchmark proposed by the Cigr´e TF C6.04.02.
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Real time control and monitoring of grid power systems using  cloud computing

Real time control and monitoring of grid power systems using cloud computing

In this paper, our main objective is to design real-time monitoring and control of substation power data remotely in the efficient, secure and effective manner using the real-time cloud computing framework from any place and any time. As per the report of Indian Grid failure [7], [8], the leading cause of cascade tripping was the over-drawing of power between eastern and northern grid. Also in the report, there has been stated the requirement for the grid security against such over-drawl conditions. This research shows the method which has been utilized to observe the status of grid parameters like load, VA, voltages, and current.
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Prognostic Control and Load Survivability in Shipboard Power Systems

Prognostic Control and Load Survivability in Shipboard Power Systems

In shipboard power systems (SPS), it is important to provide continuous power to vital loads so that their desired missions can be completed successfully. Several components exist between the primary source and the vital load such as transformers, cables, or switching devices. These components can fail due to mechanical stresses, electrical stresses, and overloading which could lead to a system failure. If the normal path to a vital load cannot supply power to it, then it should be powered through its alternate path. The process of restoring, balancing, and minimizing power losses to loads is called network reconfiguration. Prognostics is the ability to predict precisely and accurately the remaining useful life of a failing component. In this work, the prognostic information of the power system components is used to determine if reconfiguration should be performed if the system is unable to accomplish its mission. Each component will be analyzed using the Weibull Distribution to compute the conditional reliability from present time to the end of the mission. To determine if reconfiguration is needed, all components to a given load will be utilized in structure functions to determine if a load will be able to survive during a time period. Structure functions are used to show how components are interconnected, and also provide a mathematical means for computing the total probability of a system. This work will provide a method to compute the conditional survivability to a given load, and the results indicate the top five loads that have the lowest conditional survivability during a mission in known configuration. The results show the computed conditional survivability of loads on an all electric navy ship.
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Load Frequency Control of Multiple-Area Power Systems

Load Frequency Control of Multiple-Area Power Systems

9 power system consists of three areas with non-reheat, reheat and hydraulic units in different areas. This system is used to check the feasibility and performance of ADRC solution for different generating units. The second power system has the same structure as the system presented in [23]. It is rebuilt in order to compare the performances between ADRC and the PI type controllers tuned via GALMI, an existing effective LFC solution. ADRC was simulated on the two types of power systems. The simulation verified the effectiveness of the controller. In addition, the robustness and stability of ADRC have been successfully proved through time-domain simulation results and frequency-domain analyses. The notable robustness of ADRC provides the controlled power systems with sufficient tolerances to the model and parameter uncertainties. The thesis provides strong theoretical support for the implementation of ADRC in the real-world LFC problem. Besides the contributions to the control of the power systems, the thesis also originally modified ADRC to control systems with zeros in the transfer functions.
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LOAD FREQUENCY CONTROL OF MULTIPLE-AREA POWER SYSTEMS

LOAD FREQUENCY CONTROL OF MULTIPLE-AREA POWER SYSTEMS

9 power system consists of three areas with non-reheat, reheat and hydraulic units in different areas. This system is used to check the feasibility and performance of ADRC solution for different generating units. The second power system has the same structure as the system presented in [23]. It is rebuilt in order to compare the performances between ADRC and the PI type controllers tuned via GALMI, an existing effective LFC solution. ADRC was simulated on the two types of power systems. The simulation verified the effectiveness of the controller. In addition, the robustness and stability of ADRC have been successfully proved through time-domain simulation results and frequency-domain analyses. The notable robustness of ADRC provides the controlled power systems with sufficient tolerances to the model and parameter uncertainties. The thesis provides strong theoretical support for the implementation of ADRC in the real-world LFC problem. Besides the contributions to the control of the power systems, the thesis also originally modified ADRC to control systems with zeros in the transfer functions.
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Controller HIL testing of real-time distributed frequency control for future power systems

Controller HIL testing of real-time distributed frequency control for future power systems

This mismatch of data formats and endianness requires extra lines of code for adapting the data that is sent and received. For this matter on the controller side when the data is read from the server first of all it needs to be split in groups of 4-bytes as each 4-bytes composes a different signal, then each of the 4-bytes groups is currently a 4 separated uint8 signals that need to be converted into a single uint32 before its bits are swapped for going from big endian to little endian. For the process of sending data from the controllers to the server, calculations on the controller code are usually carried out with single or double precision numeric data types, therefore before data is sent it need to be converted to uint8 without changing underlying data. On the server side the same process but opposite is performed, the received data at the server from the RTDS is converted from a single precision number to a uint8 and the received uint8 is converted to single and also swapped.
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Dependable, Open and Real-time Architecture for Power Systems

Dependable, Open and Real-time Architecture for Power Systems

Dependable, Open and Real-time Architecture for Power Systems — DORA-Power — OVERVIEW: To improve operating efficiency for deregulation and for other changes in the operating environment, electric power utilities in Japan are integrating information and control systems to support a stable supply of power and strengthening their connections. For that reason, the demand for the reliability in information and control systems, is even greater than before. Furthermore, from the viewpoint of the interconnectability and expandability of systems, there is a need to implement open systems that are based on industrial standard specifications. Under those requirements, Hitachi, Ltd. developed DORA-Power (Dependable, Open and Real-time Architecture for power systems), which conforms to the open platform that is rapidly being standardized and builds in the technology for achieving high reliability and high responsiveness that has been developed for information and control systems. DORA-Power makes it possible to incorporate the state-of-the-art technology to achieve superior functionality and operability in information and control systems for power systems, where reliability and real-time operation are required.
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Wide-Area Monitoring and Control of Power Systems using Real-Time Hardware-in-the-Loop Simulations.

Wide-Area Monitoring and Control of Power Systems using Real-Time Hardware-in-the-Loop Simulations.

Table 3.3: Bus Voltages 3.3 Voltage Tuning Though the phase angles were of primary interest for matching, matching the voltages to a reasonable level was important as well. The voltages were matched during the load-flow calculations computed in RSCAD. Internal voltages on the buses inside the five machines were tuned so that load-flow compilation yielded a close match on bus voltage value. The voltages were matched to the last point of data immediately prior to the fault time in the set of PMU data received. Values were matched by repeated changing of voltage set points and recompilation of the draft. The voltages, however, did not match quite as well during run-time when the model was actually running. Table 3.3 lists the voltages viewed in run-time versus the voltages seen in the PMU data. The values are close, lying within two percent of the actual PMU data values, which was deemed to be close enough for the model’s purpose. Further retuning of the internal bus voltages to match run-time values rather than load-flow values is also possible, but was not pursued for the sake of simplicity.
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Algebraic and parametric solvers for the power flow problem: towards real-time and accuracy-guaranteed simulation of electric systems

Algebraic and parametric solvers for the power flow problem: towards real-time and accuracy-guaranteed simulation of electric systems

This method have been developed in different ar- eas, some of them are: image processing, data compres- sion, signal analysis, modeling and control of chemical reaction systems, turbulence models, control of fluids, electrical power grids, pattern recognition, wind engi- neering, etc. Despise POD methods are useful in many cases, when non-linear systems are involved, difficulties might appear since the cost of evaluating the smaller system resulting after apply the method still depends on the number of variables of the full model. For this reason, other methods have been developed in recent decades, for instance Discrete Empirical Interpolation Method, meant to be an improvement of the POD ap- proximation because (based on a projection combined with interpolation) it achieves a reduction of the nonlin- ear term with a complexity proportional to the number of reduced variables [19].
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Real-time comprehensive simulation of electric power systems for the task of overvoltages value determination

Real-time comprehensive simulation of electric power systems for the task of overvoltages value determination

Switching overvoltages occur after any commutation (planned or emergency) and due to the overcharge of capacities and network parameters changing in the transition process of the system from one state to another. Duration of switching overvoltages can range from a few milliseconds to a few seconds. Switching overvoltages, as well as lightning surges, in most cases higher than acceptable levels of surges for all insulation kinds and therefore should be limited, especially in extra-high voltage electrical installations, which include the 500 kV network. However, the danger of switching overvoltages is determined not only by their large amplitude but also by duration, which is an average of two orders longer than the duration of lightning impulse. Therefore, the switching overvoltage energy is much higher than the energy of lightning surge. As a result the conditions of the equipment operation during the switching overvoltages primarily non-linear resistances of overvoltage limiters is significantly harder because much more power is dissipated in them. The basis for the solution of issues related to the switching overvoltages is initial information about them. It is obvious that the best way of such information obtaining is using of switching overvoltages oscillograms. A set of oscillograms for various power system nodes is a complete map of overvoltages for the region. As a
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Cybersecurity for Electric Power Control and Automation Systems

Cybersecurity for Electric Power Control and Automation Systems

gmani@iastate.edu). C.-C. Liu is with the Electrical and Computer Engineering Department, Iowa State University, IA 50010, USA (e-mail: liu@iastate.edu). capabilities for operation, control, business, and analysis, it also increases the security risks including power system cybersecurity (PSC) threats and vulnerability. A cyber attack on the control center computer systems could lead to undesirable switching operations, resulting in widespread power outages. Another cyber attack scenario is to penetrate the substations and alter protective relay settings, which could result in undesirable switching actions. Currently the system may not have strong measures against cyber attacks and, therefore, vulnerabilities exist. Consequently, there is a growing demand to address these cybersecurity issues in a comprehensive and systematic manner.
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Parameter Estimation for Inventory of Load Models in Electric Power Systems

Parameter Estimation for Inventory of Load Models in Electric Power Systems

Parameter Estimation for Inventory of Load Models in Electric Power Systems Amit Patel, Kevin Wedeward, and Michael Smith Abstract—This paper presents an approach to characterize power system loads through estimation of contributions from in- dividual load types. In contrast to methods that fit one aggregate model to observed load behavior, this approach estimates the inventory of separate components that compose the total power consumption. Common static and dynamic models are used to represent components of the load, and parameter estimation is used to determine the amount each load contributes to the cumulative consumption. Trajectory sensitivities form the basis of the parameter estimation algorithm and give insight into which parameters are well-conditioned for estimation.
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