Optimal Transient Response Research Articles

Sample Voltage Dead-Beat Control Based on Differentiative Voltage Prediction and Switching-Cycle Extension for DC-DC Converters

In this paper, a sample voltage dead-beat control based on differentiative voltage prediction (DVP) and switching-cycle extension (SCE) is presented to achieve optimal transient response for DC-DC converters under discontinuous conduction mode (DCM) operation. Firstly, to improve load transient response, a DVP method is proposed to estimate the load. With the estimated load, the controller realizes load current feedforward and thus improves the transient response with a wide load range. Secondly, an SCE strategy is proposed to enlarge the output current range and output voltage slew rate, both of which have limited value under conventional digital pulse width modulation (DPWM). When the output current reaches the limited value, the proposed strategy increases the switching cycle to enlarge the current range without losing DCM operation. Finally, combining DVP with SCE, the converter not only achieves optimal response in large signal transients, but also doubles the load range in DCM operation.

Electric vehicle participation for optimized load frequency control in a multi-area restructured power system

ABSTRACT Electric vehicles (EVs) can be employed intelligently in Vehicle-to-Grid (V2G) and Grid-to-Vehicle (G2V) modes for Load Frequency Control (LFC) in the power grid. Due to the rapid variation of charging or discharging power, EVs can perform frequency regulation tasks and serve as distributed energy storage devices. In this paper, a linearized model of an interconnected multi-area power system is formulated in the restructured environment to include Electric Vehicle Aggregators (EVA). The DISCO Participation Matrix (DPM) is used to model Poolco and bilateral contracts in restructured multi-area power systems along with the participation of EVs. The faster dynamic response of EVs can effectively control the deviations in area frequencies imposed by the DISCOs load demand. The gains of the integral controller employed in each area are tuned by Real Coded Genetic Algorithm (RGA) by minimizing the integral square error function for area frequency deviations. The efficacy of power support from the EVs for load frequency control is validated by simulating different Poolco and bilateral transactions. It is shown that the EVs have a significant impact on obtaining optimal transient response for area frequencies, tie-line powers and power generation of conventional thermal generating units for any type of transaction in a restructured environment.

Small-Signal Analysis and Design of Constant On-Time Controlled Buck Converters With Duty-Cycle-Independent Quality Factors

This paper presents a frequency-domain analysis that models the behavior of Constant-on-Time (COT)-controlled Buck converters in wide-input-output-range scenarios. Based on this analysis, a design strategy is proposed to enable robust control with a duty-cycle-independent quality factor, also known as a constant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> -value. A constant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> -value circuit based on the proposed strategy is then constructed and incorporated with a baseline ultra-fast transient constant on-time (UFTCOT) control scheme to experimentally verify the system stability and optimal load transient response under wide input-output range scenarios. In addition, the design strategy is extended to other COT Buck control schemes with simulation and calculation verifications.

A Modified Particle Swarm Optimization Algorithm for Power Sharing and Transient Response Improvement of a Grid-Tied Solar PV Based A.C. Microgrid

The increasing penetration of Distributed Generators (D.G.) into the existing power system has brought some real challenges regarding the transient response of electrical systems. The injection of D.G.s and abrupt load changes may cause massive power, current, and voltage overshoots/undershoots, which consequently affects the equilibrium of the existing power system and deteriorate the performance of the connected electrical appliances. A robust and intelligent control strategy is of utmost importance to cope with these issues and enhance the penetration level of D.G.s into the existing power system. This paper presents a Modified Particle Swarm Optimization (MPSO) algorithm-based intelligent controller for attaining a desired power-sharing ratio between the M.G. and the main grid with an optimal transient response in a grid-tied Microgrid (M.G.) system. The proposed MPSO algorithm includes an additional parameter named best neighbor particles (rbest) in the velocity updating equation to convey additional information to every individual particle about all its neighbor particles, consequently leading to the increased exploration capability of the algorithm. The MPSO algorithm optimizes P.I. parameters for transient and steady-state response improvement of the studied M.G. system. The main dynamic response evaluation parameters are the overshoot and settling time for active and reactive power during the D.G. connection and load change. Furthermore, the performance of the proposed controller is compared with the PI-PSO-based MG controller, which validates the effectiveness of the proposed M.G. control scheme in maintaining the required active and reactive power under different operating conditions with minimum possible overshoot and settling time.

A Unified Design Approach of Optimal Transient Single-Phase-Shift Modulation for Nonresonant Dual-Active-Bridge Converter With Complete Transient DC-Offset Elimination

The dynamics of nonresonant dual-active-bridge converter (DABC) are simultaneously affected by the transient modulation strategy and controller design. In general, inappropriate transient modulation strategies can lead to nonzero transient dc offsets in the inductor current and transformer’s magnetizing current, thus introducing excessive trajectory tracking error and time delays between the pulsewidth modulation generator and controller. Consequently, truly optimal transient responses cannot be achieved solely through a high-performance controller, unless the modulation-induced transient dc offsets can be completely eliminated. This article presents a comprehensive review of the optimized transient phase-shift modulation (OTPSM) strategies for single-phase-shift modulated DABC, and derives a novel optimal modulation method referred to as symmetric single-sided OTPSM (SS-OTPSM), which is based on a unified theoretical framework of OTPSM and an additional condition enabling a full elimination of all undesired transient dc offsets. The proposed SS-OTPSM can be easily and cost-effectively implemented in a cycle-by-cycle manner, and inherently compatible with fast controllers. Additionally, in order to more accurately match DABC’s power transfer model under SS-OTPSM, an enhanced model predictive controller (EMPC) is proposed. By a combined use of SS-OTPSM and EMPC, ultrafast and completely dc-offset-free dynamics can be achieved without measuring the inductor current. The effectiveness of the proposed schemes is verified by closed-loop simulation and experimental results.

A multi‐strategy fuzzy control method based on the Takagi‐Sugeno model

AbstractIn this work, a new multi‐strategy fuzzy control (MSFC) based on fuzzy fusion techniques for the control of multivariable nonlinear systems is proposed. This new nonlinear control method is a mixture of different control techniques by fuzzy interpolation using the fuzzy Takagi‐Sugeno model. It combines various control strategies to achieve smooth transient responses and zero steady state error. The following techniques are merged within the proposed MSFC structure: an optimal state feedback control that yields an optimal transient response, optimal control through an incremental state model that returns a zero steady state error, and a constant input control to maintain the system behavior within predefined boundaries whenever the MSFC method is applied.

Decentralized Phase Shedding with Low Power Mode for Multiphase Converter

With a multiphase converter, the phase-shedding function dedicated to maximizing the power efficiency, in a manner that is dependent on the load current, is always provided by a centralized controller that induces a Single Point of Failure (SPOF). The objective of this study is to obtain a decentralized control approach to implement this function by removing any SPOF. The method consists of using identical local controllers, each associated with a converter phase, that communicate with each other in a daisy-chain structure. Instead of measuring the global output current to determine the optimal number of active phases required, each local controller measures its own leg current and takes a local decision based on threshold crossing management and inter-controller communications. Functional simulations are carried out on a 5-leg 12 V/1.2 V 60 W multiphase converter supplying a modern microcontroller. They demonstrate that the number of active phases is well adjusted, in a dynamic manner, depending on the load current level. Specific events such as load current inrush or the start-up sequence are analyzed to guarantee optimal transient responses. A maximum power efficiency tracking ability is also demonstrated. Finally, it is shown that this control strategy allows phase shedding to be implemented using as many phases as desired, in a modular manner, thereby avoiding any centralized processing.

Pseudo-Derivative Feedback Controller for Automatic Generation Control in a Deregulated Power System with Hydrogen Energy Storage

This paper is focused on design and application of Pseudo-Derivative Feedback (PDF) controller for Automatic Generation Control (AGC) of a two-area thermal reheat interconnected power system treated in deregulated condition. The proposed controller gains are tuned simultaneously using Flower Pollination Algorithm (FPA) in order to achieve the optimal transient response of the test system. The control performance of the PDF controller is compared with Proportional Integral (PI) and Proportional Integral Derivative (PID) controllers. Further to improve the AGC performance, Hydrogen Energy Storage (HES) are included in its control area. The execution of HES unit captures the underlying fall in frequency as well as the tie line control power deviations after a sudden load unsettling influence. The simulation results demonstrate that the proposed PDF controller enhance the dynamic response of the deregulated power system as compared with PI and PID contrtoller. The frequency oscillation and tie-line power deviations in the control zones are reduced and the settling time is additionally enhanced when HES unit takes an interest in the frequency regulation along with the traditional generators. Additionally, the Power System Restoration Indices (PSRI) is figured in view of system dynamic performances and the remedial measures to be taken can be decreed. These PSRI shows that the ancillary service requirement to enhances the effectiveness of physical task of the power system with the expanded transmission limit in the system. The presence of an Hydrogen Energy Storage (HES) water electrolyser coupled to a fuel cell improves significantly the control and operation of an energy system and provides good margin of stability of the grid system compared to that a system without HES unit.

Design and Analysis of Vector Proportional–Integral Current Controller forLC-Coupling Hybrid Active Power Filter With Minimum DC-Link Voltage

In this article, a vector proportional-integral (VPI) current controller for the LC-coupling hybrid active power (LC-HAPF) with ideally zero steady-state error, optimal transient response, and good robustness is proposed. First, the transfer function of the proposed VPI current controller is introduced, and its parameter design for obtaining optimal transient response is discussed. Second, a detailed robustness analysis of the VPI current controller, including the system parameter variation, distorted grid voltage, and grid frequency variation conditions, is proposed. Third, the digital implementation method of the VPI controller and an overall control block diagram for the LC-HAPF with the proposed VPI current controller are presented. Moreover, a comparative study and analysis between the VPI current controller and the other representative current controllers under the minimum dc-link voltage is discussed in which the VPI current controller obtains the best performances under the minimum dc-link voltage operation. The simulation and experimental results are provided to verify the advantages and effectiveness of the proposed VPI current controller for a three-phase four-wire LC-HAPF in comparison with the other representative current controllers under different dc-link voltage conditions. Finally, the robustness under different grid conditions and unbalanced compensation capability of the proposed VPI-controlled LC-HAPF are also verified by the experimental results.

The Effects of Honeycomb Parameters on Transient Response of an Aircraft Sandwich Panel Structure

In this paper, an experimental and numerical investigation were conducted to develop an understanding of the importance and role played by honeycomb design parameters in transient response of aircraft sandwich with honeycomb core under the transient load. Forced vibration under transient load test was implemented on sandwich panel with honeycomb core specimens. Vibration rig with specific equipment was manufactured. Finite element simulation for the sandwich panel with honeycomb core were developed and analyzed by Ansys software package. Modal analysis and transient response analysis have been carry out to obtain the numerical transient response. The obtained results show a good agreement between above approaches with conformity by 85% percentage. The core high, cell size and cell wall thickness were selected to explore the effect of honeycomb parameters on the transient response of sandwich structure. In order to obtain the optimum condition, Response Surface Methodology (RSM) was used. Results showed that minimum transient response were found at 20 mm core height, 25 mm size cell and 1.5 mm cell wall thickness. Where, the optimal value minimum transient response equal to 0.0019 mm.

Jaya optimization algorithm for transient response and stability enhancement of a fractional-order PID based automatic voltage regulator system

Considering the higher flexibility in tuning process and finer control action of the fractional-order proportional integral derivative (FOPID) controller over the conventional proportional integral derivative (PID) controller, this paper explores its application in the automatic voltage regulator system. FOPID contains five tuning parameters as compared to three in the conventional PID controller. The additional tuning knobs in FOPID provide increased control flexibility and precise control action, however, their inclusion makes the tuning process more complex and tedious. Thus, the intelligence of an artificial intelligence (AI) technique called jaya optimization algorithm (JOA) is utilized in order to obtain an optimal combination of FOPID gains which further led to the optimal transient response and improved stability of the considered AVR system. To validate the performance superiority of the proposed approach its corresponding system’s dynamic response is compared with that of the other well-known AI-based approaches explored in recent literature. Furthermore, the stability study of the proposed AVR system is carried out by evaluating its pole/zero and bode maps. Finally, the robustness of the proposed optimized AVR system against the system’s parameter variation is evaluated by varying the time constants of all the four components of AVR (generator, exciter, amplifier and sensor) from −50% to +50% independently. The proposed algorithm based FOPID tuning technique provides 59.82%, 56.09%, 14.94%, 34.24%, 35.70%, 21.64%, 12.0%, 41.33%, 14.84% and 15.17% reduced overshoot than that of differential evolution (DE), particle swarm optimization (PSO), Artificial Bee Colony (ABC), Bibliography Based Optimization (BBO), Grasshopper Optimization Algorithm (GOA), Pattern Search Algorithm (PSA), Improved Kidney Inspired Algorithm (IKA), Whale Optimization Algorithm (WOA), Salp Swarm Algorithm (SSA) and Local Unimodal Sampling (LUS) algorithm respectively, thus validates its competence and effectiveness.

Transient Control and Soft Start-Up for 1-MHz LLC Converter With Wide Input Voltage Range Using Simplified Optimal Trajectory Control

The 48-V bus converters are widely used in telecommunications and network power architectures. A single-stage regulated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> bus converter can achieve high efficiency and high power density. This article addresses the control challenges of a regulated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> converter for 48-V bus converter applications. Simplified optimal trajectory control (SOTC) is used to control a 1-MHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> converter with an input voltage range of 40–60 V and a frequency range of 0.8–1.8 MHz. A digital implementation of two-step SOTC is proposed for the high-frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> using a low-speed microcontroller (MCU). The proposed implementation can achieve the optimum transient performance and minimize settling time. SOTC can achieve the optimum transient response for an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> operating at resonant frequency but has a limited impact at a wide gain range. As a result, a feedforward compensation is proposed, in conjunction with SOTC, to achieve optimum transient response at a wide input voltage range or wide gain range. Moreover, a soft start-up with adaptive switching frequency is proposed to achieve start-up under limited current stress over the whole input voltage range. The experimental results are demonstrated on a 1-MHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> 48-V bus converter using a 90-MHz TMS320F28069 Piccolo MCU.

Salp Swarm Optimization Algorithm-Based Controller for Dynamic Response and Power Quality Enhancement of an Islanded Microgrid

The islanded mode of the microgrid (MG) operation faces more power quality challenges as compared to grid-tied mode. Unlike the grid-tied MG operation, where the voltage magnitude and frequency of the power system are regulated by the utility grid, islanded mode does not share any connection with the utility grid. Hence, a proper control architecture of islanded MG is essential to control the voltage and frequency, including the power quality and optimal transient response during different operating conditions. Therefore, this study proposes an intelligent and robust controller for islanded MG, which can accomplish the above-mentioned tasks with the optimal transient response and power quality. The proposed controller utilizes the droop control in addition to the back to back proportional plus integral (PI) regulator-based voltage and current controllers in order to accomplish the mentioned control objectives efficiently. Furthermore, the intelligence of the one of the most modern soft computational optimization algorithms called salp swarm optimization algorithm (SSA) is utilized to select the best combination of the PI gains (kp and ki) and dc side capacitance (C), which in turn ensures optimal transient response during the distributed generator (DG) insertion and load change conditions. Finally, to evaluate the effectiveness of the proposed control approach, its outcomes are compared with that of the previous approaches used in recent literature on basis of transient response measures, quality of solution and power quality. The results prove the superiority of the proposed control scheme over that of the particle swarm optimization (PSO) and grasshopper optimization algorithm (GOA) based MG controllers for the same operating conditions and system configuration.

Discrete-Time Optimal Control of Electromagnetic Coil Systems for Generation of Dynamic Magnetic Fields With High Accuracy

Electromagnetic coil systems (ECSs) have been widely used for actuation and motion control of magnetic micro/nanorobots. In this paper, two typical ECSs with different system configurations are developed: One is computer-based and uses servoamplifiers for driving the coils and the other adopts an embedded control system with home-designed circuit boards for driving the coils. For dynamic control of the two types of ECSs, a unified control scheme is proposed with two objectives: 1) to make the output magnetic field converge to the reference without steady-state error; 2) to achieve optimal transient response under tunable requirement of control effort. In the scheme, dynamic models of the two systems are described by a unified state-space form with different dimensions, which are obtained by system identification. Then, a discrete-time optimal controller is designed based on the linear quadratic with integral action method to realize the control objectives. Finally, in order to make the controller applicable to the real ECSs, the time-delayed system states are estimated by utilizing a Kalman filter, and a Smith predictor inspired compensator is designed to compensate for time delay and modeling error. Simulations and experiments using the proposed control scheme are conducted for the two ECSs with three-axis Helmholtz coils, which show the easy adaption of the control approach to different coils. Experimental results validate the significantly improved dynamic performances of the two ECSs, and tracking a three-dimensional dynamic magnetic field with high accuracy is also demonstrated.

Steady-state and transient control strategies for a two-stage turbocharged diesel engine

Two-stage turbocharging technology is widely used to achieve higher engine power density and lower exhaust emissions. To solve a series of contradictions in matching, a regulated two-stage (RTS) turbocharging system is applied to reasonably control boost pressure. This paper investigated steady-state and transient control strategies for an RTS turbocharging system to achieve optimum fuel economy in steady-state conditions and better performance in transient conditions. The economic control strategies for steady-state operational conditions were based on an economic regulation law, which was established by a steady-state test of an engine with an RTS turbocharging system under all operating conditions. To optimize the transient performance, open-loop and closed-loop control systems (the latter with dynamic judgement) for the RTS system were designed and validated with experiments on a heavy-duty diesel engine. The experimental results demonstrated that the open-loop control strategy and the closed-loop strategy with dynamic judgement could improve the transient response performance. The optimum transient response performance was achieved by the closed-loop control system with dynamic judgement. Additionally, the combination of steady-state and transient control strategies could achieve the best fuel economy in steady-state conditions and good transient response performances.

Simulation based study on improving the transient response quality of turbocharged diesel engines

PurposeUse of fossil fuels in automotive sector is one of the primary causes of greenhouse emissions. The automotive engines need to perform at their best efficiency point to limit these emissions. Most of the quality indicators in this regard are based on near steady state global operational characteristics for engines without considering local performance. In the present study, extensive numerical simulations have been carried out covering a wide range of steady state and transient operating conditions to quantify interaction of turbocharger with engines through turbo lag phenomena which may cause increased emissions during the load change conditions. Furthermore possible innovations have been explored to minimize turbo lag phenomena. The paper aims to discuss these issues.Design/methodology/approachIn this paper quality indicators have been developed to quantify the performance of turbocharged diesel engine under the transient event of rapid change in fueling rate which has been rarely investigated. The rate of fueling is changed from 40 mm3/injection to 52 mm3/injection at 1,000 rpm engine speed which corresponds to normal operating condition. To improve quality of transient response, torque assistance method and reduction of inertia of compressor wheel have been used. Parametric study has been undertaken to analyze the quality indicators such as outlet pressure of the compressor and the compressor speed. The turbo lag is quantified to obtain the close to optimal transient response of turbocharged diesel engine.FindingsIt has been shown that, with torque assist the transient response of the internal combustion engine is significantly improved. On the other hand, marginal improvement in transient response is observed by the reduction in inertia of the compressor wheel.Research limitations/implicationsThe findings indicate that turbo lag can be minimized by providing torque assistance by active and passive means.Practical implicationsThe developed methods can be used in practice for efficient operation of vehicles.Social implicationsThe work carried out in the paper provides a way to minimize harmful emissions.Originality/valueThe quality indicators developed provide a quantitative measure of turbo lag phenomena and address the above mentioned problems.

Coordinated design of fuzzy‐based speed controller and auxiliary controllers in a variable speed wind turbine to enhance frequency control

This paper proposes novel controllers for doubly fed induction generator (DFIG)-based wind turbines. These controllers not only optimize the transient behaviour of DFIGs, but also realize their participation in the power system frequency control task. The proposed controllers include one main speed controller as well as two auxiliary controllers. The main speed controller is a fuzzy-based controller which their parameters are optimized using the genetic algorithm (GA) to achieve the optimal transient response. It applies the rotational speed signal and causes the DFIG to return to the maximum power point (MPP) quickly after any turbulent in the wind speed. Moreover, two smart auxiliary controllers, i.e., frequency deviation and wind speed oscillations controllers are suggested. The frequency deviation controller enables the DFIG frequency support and the wind speed oscillations controller alleviates the impacts of wind speed fluctuations on the wind turbine output power both with utilizing the wind turbine kinetic energy. To investigate the efficiency of main controller, two case studies are considered. Moreover, some time domain simulations are performed on IEEE 39-bus system to evaluate the influences of the auxiliary controllers on the load frequency control task. Results confirm the effectiveness and superiority of the proposed controllers.

Optimal Generation Dispatch With High Penetration of Photovoltaic Generation

Power system operation practices are changing with the addition of renewable energy resources such as photovoltaic (PV) sources. The diverse and intermittent nature of these resources demands new operation strategies to ensure system reliability. As more PV units are added to power systems, the power generated by conventional generation resources should be reduced to accommodate these new resources. The reduction in fossil-fired generation allows realization of benefits in the sustainability of the generation mix. While some of the conventional generating units are retired, some should be retained for system reliability. This paper investigates the impact of generation redispatch or generation displacement in systems with high PV penetration. Comparing various study scenarios, a method based on regression techniques and Chebyshevs inequality is introduced in this paper. This method is used to calculate the dispatch or displacement ratio of the conventional generators for optimal steady state and transient response of the system. Recommendations are formulated based on an actual large-scale power system in the western United States.

Coefficient ratios‐based robust sliding surface and integral sliding mode control designs with optimal transient responses

A coefficient ratio-based sliding surface algorithm and an integral sliding mode control approach are proposed for multivariable dynamical systems. The sliding surface design problem is reduced to the specification of the desired time constant of closed-loop systems. The proposed scheme is able to accomplish a non-overshoot transient response and a short settling time for multivariable systems. The resulting sliding surfaces are robust and optimal in the existence of parameter perturbations. An integral sliding mode control approach is also developed for robust tracking by using the coefficient ratio-based robust sliding surface designs. The developed methods are implemented on a flexible robotic manipulator and a strike aircraft system, and the numerical simulation results are provided in order to show the validity and feasibility of the methods.

Transient response optimisation for peak current mode buck converter in the application of dynamic voltage scaling

For optimising the peak current mode buck converter's transient response in the application of dynamic voltage scaling, an accurate small signal model of the converter under continuous conduction mode is built. The switch conduction loss, dead-time and other main parasitic parameters are considered in the presented model. Based on the model, a novel compensation network for the voltage loop is proposed, which eliminates the zero point of the voltage loop. The relationship between the gain of the proposed compensation network and the transient response of the output voltage relative to the reference voltage ( V ref ) at the input node of error amplifier is investigated. By this way, an optimal gain for the transient output voltage is obtained and the optimaltransient response without overshoot and oscillation relative to V ref is validated by the circuit simulations and tests.