Control Strategy For Mitigation Research Articles

Control strategies for road risk mitigation in kinetic traffic modelling

In this paper we present a Boltzmann-type kinetic approach to the modelling of road traffic, which includes control strategies at the level of microscopic binary interactions aimed at the mitigation of speed-dependent road risk factors. Such a description is meant to mimic a system of driver-assist vehicles, which by responding locally to the actions of their drivers can impact on the large-scale traffic dynamics, including those related to the collective road risk and safety.

PHC, Id-Iq and p-q Control Strategies for Mitigation of Current Harmonics in Three-Phase Three-Wire Shunt Active Filter with PI Controller

Abstract In this research paper, the shunt active filter (SHAF) is used to improve the power quality of electrical network by mitigating the harmonics with the help of different control strategies (p-q control strategy, Id-Iq control strategy, PHC control strategy) for three phase three wire system. It is quite difficult to optimize the performance of power system networks using conventional methods, because of complex nature of the systems that are highly non-linear and non-stationary. Three phase reference current waveforms generated by the proposed schemes are tracked by three phase voltage source converter in a hysteresis band control scheme. The performance of proposed control strategies has been evaluated in terms of harmonic mitigation and DC link voltage regulation under various source voltage conditions. The proposed SHAF with different control strategies is able to eliminate uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/Simulink software are presented to support the feasibility of the proposed control strategy.

Control strategy for mitigation of pulsed heat load transferred to ITER cryoplant from magnets

Active mitigation of pulsed heat load is foreseen for the ITER superconducting magnets during cyclic plasma scenarios to ensure stable operation of the cryoplant. The paper addresses a promising feedback control to smooth heat pulses in the primary cryogenic circuits of the ITER magnets. A feedback control signal is proposed that can be derived from direct measurements of helium parameters in a low pressure return cryoline to the cryoplant. Configurations with two or more LHe baths were investigated at the Auxiliary Cold Box (ACB) level. Efficiency of the proposed control approach was evaluated in thermohydraulic simulations. A possibility to control several cryogenic loops using a common regulator is demonstrated.

Harmonics Mitigation in a Steel Industry Using 11-Level Cascaded Multilevel Inverter-Based DSTATCOM

Use of nonlinear loads in power distribution networks is expanding day by day, which results in the deterioration of the power quality of the system. An induction furnace (IF), which is an indispensable component of the steel industry, is one such typical example of a nonlinear load. It injects a considerable amount of harmonics into the supply network and consequently the performance of other loads in its vicinity gets affected. An 11-level cascaded multilevel inverter (CMLI)-based distribution static compensator (DSTATCOM) is implemented to mitigate the harmonic content of an IF in a steel plant. A Simulink model of an IF has been developed using experimental data obtained on-line from an industrial IF using a power quality analyzer. The solution methodology proposed using CMLI-based DSTATCOM reveals the effectiveness of the proposed control strategy for voltage sag mitigation and total harmonic distortion improvement of both load current and voltage as per the IEEE standards. The results obtained are also compared with that reported in the literature recently.

Industrial 100-MVA EAF Voltage Flicker Mitigation Using VSC-Based STATCOM With Improved Performance

As an industry consumer of electric power, an electric arc furnace (EAF) is a major voltage flicker source that causes significant power-quality (PQ) problems. The fast response of the static synchronous compensator (STATCOM) makes it an efficient solution for improving PQ in distribution systems facing this kind of very nonlinear load. In this study, for voltage flicker mitigation of a 100-MVA EAF installed in Europe, a voltage-source-converter (VSC)-based STATCOM with high bandwidth is designed. The STATCOM's current reference includes both active and reactive current components. The performance of the STATCOM in voltage flicker mitigation is highly improved by applying this control strategy which uses the dc voltage margin of the VSC to provide for an active compensating current without oversizing the STATCOM converters capacitor. In this paper, first, the proposed STATCOM is studied through a generalized steady-state analysis. Second, the STATCOM's control strategies for voltage flicker mitigation are introduced and simulation results are provided and compared. Finally the complete model is validated by field tests over a 60-MVAr industrial STATCOM. Static and dynamic performance of the STATCOM is evaluated and voltage fluctuation mitigation studies are performed and discussed. The voltage flicker mitigation is evaluated through onsite measurements respecting international standards.

Improved Control Strategy for Subsynchronous Resonance Mitigation with Fractional-order PI Controller

Abstract This paper explores a robust Fractional-order PI (FOPI) controller to diminish Subsynchronous Resonance (SSR) using Static Synchronous series compensator (SSSC). The diminution of SSR is accomplished by increasing the network damping with the injection of voltage of subsynchronous component into the line at those frequencies which are proximate to the torsional mode frequency of the turbine-generator shaft. The voltage of subsynchronous frequency component is extracted from the transmission line and further the similar quantity of series voltage is injected by SSSC into the line to make the current of subsynchronous frequency component to zero which is the major source of oscillations in the turbine-generator shaft. The insertion and fine tuning of Fractional-order PI controller in the control scheme of SSSC the subsynchronous oscillations are reduced to 4 % as compared to conventional PI controller. The studied system is modelled and simulated using MATLAB-Simulink and the results are analysed to show the precision and robustness of the proposed control strategy.

Auto-Ignition Control in Spark-Ignition Engines Using Internal Model Control Structure

This paper analyzes the feasibility of applying model predictive control strategies for mitigation of the auto-ignition phenomenon, which affects the performance of spark-ignition internal combustion engines. The first part of this paper shows the implementation and experimental validation of a two-dimensional model, based on thermodynamic equations, to simulate operating conditions in engines fueled with natural gas. Over this validated model, several control strategies are studied in order to evaluate, through simulation analysis, which of these offer the best handling capacity of the auto-ignition phenomenon. In order to achieve this goal, multivariate control strategies are implemented for a simultaneous manipulation of the fuel/air ratio, the crank angle at ignition, and the inlet pressure. The controlled variable in this research is the temperature at the ignition point. This temperature is obtained through an estimation based on pressure in the combustion chamber at that point, which is located toward the end zone of the compression stroke. If the ignition temperature of the fuel–air mixture is reached during the compression process, then auto-ignition takes place. Proposed control strategies consist of maintaining the temperature in the ignition point below the fuel–air mixture auto-ignition temperature. The results show that auto-ignition is difficult to avoid using a single input–single output (SISO) strategy. However, a multiple input–single output (MISO) approach avoids the influence of the phenomenon without a significant impact over the engine's performance. Among the developed strategies, an approach based on model predictive control and feedforward control strategy shows the best performance, measured through the integral absolute error (IAE) index. These results open the possibility of new ways for improving the control capacity of auto-ignition phenomenon in engines compared to currently available feedback control systems.

Real-time experimental validation of a novel semi-active control scheme for vibration mitigation

Summary This study performs an experimental investigation of a novel, semi-active control strategy for effective vibration mitigation. The implemented approach comprises a combination of the linear quadratic regulator with a nonlinear observer, namely, the unscented Kalman filter, for the control of systems described by uncertainties. Indeed, numerical models of structural systems often result as inadequate because of inherent uncertainties, such as noise, modeling errors, unknown system properties, or influence of varying operational and environmental conditions. In tackling this issue, the unscented Kalman filter is herein employed for adaptive joint state and parameter estimation refining the accuracy of the model employed by the controller and resulting in enhanced vibration mitigation. A scaled five-story shear frame attached to a hydraulic cylinder comprises the tested structure, where actuation is provided by means of a rotational magnetorheological damper operating on the relative motion between the ground floor and the first floor plate. The experimentally obtained results demonstrate a good agreement with simulations and encourage further implementation of the proposed framework in field applications of structural control. Copyright © 2016 John Wiley & Sons, Ltd.

Dispatching and Frequency Control Strategies for Marine Current Turbines Based on Doubly Fed Induction Generator

This paper presents the modeling and development of a dispatchable large-scale marine current turbine (MCT)farm equipped with power fluctuation compensation and primary frequency control schemes. The proposed control strategies rely on the regular and highly predictable power extraction from the marine currents, which are essentially governed by astronomical forces. Therefore, a mathematical model for prediction of marine current speed is developed and validated with the recorded measurements. Subsequently, the effect of velocity disturbances caused by the swell effect is studied and a battery energy storage station (BESS)control strategy for power fluctuation mitigation is proposed with reduced BESS capacity. Additionally, the provision of frequency control for MCT based on BESS has been discussed. The performance of the BESS-based frequency control strategy has been analyzed and compared with that of frequency control based on the combination of inertial response and deloaded operation. The simulation results depict that both these strategies can effectively enable MCTs to participate in primary frequency control, however, provision of frequency control based on BESS is more feasible in terms of profitability and reduction in fossil fuel consumption.

Output‐feedback control of combined sewer networks through receding horizon control with moving horizon estimation

AbstractAn output‐feedback control strategy for pollution mitigation in combined sewer networks is presented. The proposed strategy provides means to apply model‐based predictive control to large‐scale sewer networks, in‐spite of the lack of measurements at most of the network sewers. In previous works, the authors presented a hybrid linear control‐oriented model for sewer networks together with the formulation of Optimal Control Problems (OCP) and State Estimation Problems (SEP). By iteratively solving these problems, preliminary Receding Horizon Control with Moving Horizon Estimation (RHC/MHE) results, based on flow measurements, were also obtained. In this work, the RHC/MHE algorithm has been extended to take into account both flow and water level measurements and the resulting control loop has been extensively simulated to assess the system performance according different measurement availability scenarios and rain events. All simulations have been carried out using a detailed physically based model of a real case‐study network as virtual reality.

Embracing Risk Mitigation Strategies in Pineapple Supply Chain and Its Impact on Supply Chains Performance

Aims: This paper empirically investigated the impact of major risk mitigation strategies employed in the pineapple supply chain on the chains’ performance. Study design: A survey method involving the random sampling technique was used in selecting respondents for the study. Place and Duration of Study: The survey was conducted in Ghana between 13 April 2014–18 August 2014. Methodology: The ordinary least squareregression model was employed to analyze the primary data were collected through a survey with a sample of 303 top executives and participants operating in the pineapple supply chain. Results: The analytical results revealed that, not all the five (5) major mitigation strategies, mostly employed in pineapple supply chain significantly improved the performance of the chain. Risk Original Research Article Nyamah et al.; AJAEES, 4(4): 302-316, 2015; Article no.AJAEES.2015.031 303 acceptance, as a strategy to mitigate any of the risks studied undermined the performance of the chain. With the exception of acceptance as mitigation strategy, all studied strategies employed to mitigate demand related risk, significantly improved the chains’ performance. The adoption of control and coordination as strategies to mitigate supply and logistics related risk, significantly enhanced the chain’s performance respectively. Even though, none of the strategies embraced to mitigate political and weather related risks, significantly improved the chain’s performance, the used of coordination as a strategy to mitigate policy and regulatory risks, yielded significant improvement of the chain’s performance. With the exemption of avoidance and control mitigation strategies, none of the studied strategies employed to mitigate biological and environmental related risks significantly improved the performance of the chain. Also, the adoption of strategies such as avoidance, control and coordination to mitigate management and operation related risks significantly improved the performance of the chain. By mitigating finance related risk, with strategies such as control and coordination, the performance of the chain significantly improved. Conclusion: Therefore, to improve the pineapple supply chain performance, this study advocates the use of mitigating strategies such as avoidance, control and coordination to mitigate all the risk studied with the exception of political and weather related risk.

Simulation comparison of wake mitigation control strategies for a two-turbine case

Wind turbines arranged in a wind plant impact each other through their wakes. Wind plant control is an active research field that attempts to improve wind plant performance by coordinating control of individual turbines to take into account these turbine–wake interactions. In this paper, high-fidelity simulations of a two-turbine fully waked scenario are used to investigate several wake mitigation strategies, including modification of yaw and tilt angles of an upstream turbine to induce wake skew, as well as repositioning of the downstream turbine. The simulation results are compared through change relative to a baseline operation in terms of overall power capture and loading on the upstream and downstream turbine. Results demonstrated improved power production for all methods. Analysis of control options, including individual pitch control, shows potential to minimize the increase of, or even reduce, turbine loads.Copyright © 2014 John Wiley & Sons, Ltd.

FLC based shunt active filter (p–q and Id–Iq) control strategies for mitigation of harmonics with different fuzzy MFs using MATLAB and real-time digital simulator

Problems caused by power quality have great adverse economical impact on the utilities and customers. Current harmonics are one of the most common power quality problems and are usually resolved by the use of shunt active filters (SHAFs). Control strategies (p–q and Id–Iq) for extracting the three-phase reference currents for shunt active power filters are compared, evaluating their performance under different source conditions. Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme.The performance of the control strategies has been evaluated in terms of harmonic mitigation and DC link voltage regulation. The proposed SHAF with different fuzzy MFs (Trapezoidal, Triangular and Gaussian) is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategies. To validate the proposed approach, the system is also implemented on a real-time digital simulator (OPAL-RT) Hardware and adequate results are reported for its verifications.

An ant colony optimization algorithm-based emergency control strategy for voltage collapse mitigation

Abstract This paper presents optimal preventive control actions using ant colony optimization (ACO) algorithm to mitigate the occurrence of voltage collapse in stressed power systems. The proposed objective functions are: minimizing the transmission line losses as optimal reactive power dispatch (ORPD) problem, maximizing the preventive control actions by minimizing the voltage deviation of load buses with respect to the specified bus voltages and minimizing the reactive power generation at generation buses based on control variables under voltage collapse, control and dependent variable constraints using proposed sensitivity parameters of reactive power that dependent on a modification of Fast Decoupled Power Flow (FDPF) model. The proposed preventive actions are checked for different emergency conditions while all system constraints are kept within their permissible limits. The ACO algorithm has been applied to IEEE standard 30-bus test system. The results show the capability of the proposed ACO algorithm for preparing the maximal preventive control actions to remove different emergency effects.

Simulation and real-time implementation of shunt active filter id–iq control strategy for mitigation of harmonics with different fuzzy membership functions

In this research study, the shunt active filter (SHAF) is used to improve the power quality of the electrical network by mitigating the harmonics with the help of different fuzzy membership functions (M.Fs) (trapezoidal, triangular and Gaussian). It is quite difficult to optimise the performance of power system networks using conventional methods, because of the complex nature of the systems that are highly non-linear and non-stationary. Three-phase reference current waveforms generated by the proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the proposed control strategy has been evaluated in terms of harmonic mitigation and dc-link voltage regulation under various source conditions. The proposed SHAF with different fuzzy M.Fs is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using Matlab/Simulink software are presented to support the feasibility of the proposed control strategy. To validate the proposed approach, the system is also implemented on a real-time digital simulator hardware and adequate results are reported for its verification.

Real-Time Implementation of Shunt Active Filter P-Q Control Strategy for Mitigation of Harmonics with Different Fuzzy M.F.s

This research article presents a novel approach based on an instantaneous active and reactive power component (p-q) theory for generating reference currents for shunt active filter (SHAF). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the SHAF using the p-q control strategy has been evaluated under various source conditions. The performance of the proposed control strategy has been evaluated in terms of harmonic mitigation and DC link voltage regulation. In order to maintain DC link voltage constant and to generate the compensating reference currents, we have developed Fuzzy logic controller with different (Trapezoidal, Triangular and Gaussian) fuzzy M.F.s. The proposed SHAF with different fuzzy M.F.s is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy. To validate the proposed approach, the system is also implemented on a real time digital simulator and adequate results are reported for its verifications.

Control strategies for harmonic mitigation and power factor correction using shunt active filter under various source voltage conditions

This paper gives a new insight into the concept of load compensation using shunt active filter (SAF) under ideal and non-ideal source voltage conditions. A novel approach based on an improved instantaneous active and reactive current component method is proposed. The performance of the proposed control strategy has been compared with instantaneous reactive power theory, symmetrical component theory and dq theory. SAF has been realized by three-phase voltage source converter. Reference currents generated by control strategies has been tracked by a SAF in a hysteresis band control scheme. The performance of the proposed scheme is evaluated in terms of reactive power compensation, reduction in magnitude of source currents, compensator currents, and harmonic compensation as per IEEE-519 standard. To ascertain the viability of the proposed control algorithm, the performance is evaluated under different source voltage conditions with the IEEE Standard-1459 power definitions. Variation in magnitude as well as harmonic content of source voltage has been considered. Under balanced sinusoidal source voltage condition, all control strategies congregate to similar results. Under unbalanced sinusoidal source voltage condition, dq theory and proposed theory have shown similar performance. However, under distorted source voltage conditions, an improved instantaneous active and reactive current component theory presents superior performance. A three-phase, three-wire distribution system supplying non-linear load is considered for simulation study. Simulation results from a complete model of SAF are presented to validate and compare the control strategies.

Sensing-based risk mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation

This paper presents the real-time sensing-based risk-mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation. In the partially open space we previously considered (Matsuura et al., Int J Hydrogen Energy, 35(10), p. 4776–4786 (2010)), a hydrogen buoyant plume is subjected to cross flows during forced ventilation, and hydrogen travels over a long distance in the lower part of the space, which enhances the hydrogen concentration there. On the basis of those results, we alternatively propose in this paper a new partially open space that permits the almost vertical rising of hydrogen from a leak source, and exhausts, by forced ventilation, hydrogen temporarily accumulated near the roof. We first describe computational geometries and scenarios, mathematical models and numerical procedures.Related to this model, an acceptability diagram of exhaust flow rates for various leak flow rates and leak positions, an estimation method of the instantaneous hydrogen amount accumulating near the roof, and a hunting-preventive control scheme of the exhaust flow rate based on the least-squares method are constructed. A sensing-based risk mitigation control strategy to change the exhaust volume flow rate is then proposed. The effects of the number of sensors on the proposed control system are also investigated. The proposed system is validated for various leak positions and leak modes.

A Novel Control Strategy for Subsynchronous Resonance Mitigation Using SSSC

In this paper, a novel control strategy for subsynchronous resonance (SSR) mitigation using a static synchronous series compensator will be presented. SSR mitigation is obtained by increasing the network damping only at those frequencies that are critical for the turbine-generator shaft. This is achieved by controlling the subsynchronous component of the grid current to zero. Using the IEEE first benchmark model, the effectiveness of the proposed control algorithm when mitigating SSR due to torsional interaction and torque amplification effect will be shown.

Evaluation of Cascade-Multilevel-Converter-Based STATCOM for Arc Furnace Flicker Mitigation

As an industry customer of electric power, an electrical arc furnace (EAF) is a major flicker source that causes major power quality problems. For a 40-MVA EAF in Tennessee, USA, a cascade-multilevel converter (CMC)-based STATic synchronous COMpensator (STATCOM) with high bandwidth is proposed for EAF flicker mitigation. In this paper, flicker mitigation techniques by using a CMC-based STATCOM are presented and verified through a transient network analyzer (TNA) system. The required STATCOM capacity is first studied through a generalized steady-state analysis. Second, the STATCOM control strategy for flicker mitigation is introduced, and simulation results are given. Finally, a TNA system of the STATCOM and an EAF system are designed and implemented. Experimental results from the TNA test show that the proposed CMC-based STATCOM and its controller can efficiently and rapidly mitigate the EAF flicker