Dead Time Delay Research Articles

Deep Reinforcement Learning-Based Control for Asynchronous Motor-Actuated Triple Pendulum Crane Systems With Distributed Mass Payloads

For transporting large cargoes in practice, the triple pendulum hoisting pattern is widely utilized, where the distributed mass payload (DMP) is suspended under the hanger, the hanger is suspended on the hook, and the hook is connected with the hoisting mechanism. However, existing studies mainly focus on single pendulum and double pendulum hoisting patterns, and few of them pay attention to triple pendulum hoisting patterns. Compared with single pendulum and double pendulum cranes, triple pendulum cranes, which control 4 degrees of freedom (DoFs) with merely 1 control input, have a higher underactuation degree, with higher control difficulties. In addition, the nonlinear characteristics of alternating current (AC) asynchronous motors, such as unknown nonlinear dead zones and time delays, will degrade tracking accuracy and control performance. To solve the above problems, a model-free deep reinforcement learning-based trajectory planning method is proposed for triple pendulum DMP cranes. Furthermore, an identification model for AC asynchronous motors is established. On this basis, a trajectory tracking method including an adaptive dead zone compensation (ADC) and a modified Smith predictor (MSP) is proposed. Finally, experiments are carried out on a self-built 2-ton crane experimental platform, which is actuated by AC asynchronous motors. Hardware experiments demonstrate that triple pendulum cranes can accurately track the planned trajectory, and the DMP residual swing is effectively suppressed.

Optimal Tuning of PID Controllers for LFC in Renewable Energy Source Integrated Power Systems Using an Improved PSO

The constant rise in energy demand and concerns about climate change have led to increased penetration of renewable energy sources (RES). Maintaining active power balance between generation and demand in power systems with significant penetration of these highly variable and intermittent renewable sources requires an efficient load frequency control (LFC) strategy. One such strategy that has gained the attention of researchers is optimal tuning of PID controllers of LFC using metaheuristic method. This paper presents a PSO variant for optimal tuning of PID controllers for load frequency control of power system integrated with renewable energy resources. The proposed PID tuning technique is tested on a two-area power system commonly used in the literature. Seven scenarios have been used to validate the effectiveness of the proposed Load Frequency Control. For more realistic evaluation, governor dead band and communication time delays have been incorporated in the test system in one of the scenarios. Simulation results obtained when compared with those of three well-known PID-tuning metaheuristic algorithms produced shorter settling time and smaller frequency and tie line power deviations.

Optimum Setting Algorithm Based PI Controller Tuning for SRF-PLL Used Grid Synchronization System

Synchronous reference frame-phase lock loop (SRF-PLL) is most widely used for grid synchronization applications. PLL structure typically consists of a phase detector (PD), loop filter (LF) and voltage control oscillator (VCO). Design and tuning of proportional-integral (PI) controller based LF is a changeling task under distorted grid voltage conditions. Conventional tuning methods such as symmetrical optimum (SO) and Ziegler-Nichols techniques are used to tune the PI controller, resulting in increased phase margin (PM) of the system. However, high bandwidth develops harmonics in the extracted signals under non-ideal grid conditions and affects the stability. In this research article, a new optimum setting algorithm is proposed to tune the PI controller and effective synchronization is achieved. The plant is reduced as a first-order plus dead time delay (FOPDT) model and critical gain; critical frequency of the open loop system transfer function is used to model the LF of the SRF PLL system. The controller parameters are derived such that minimization of time-weighted integral performance criteria is achieved and phase angle, frequency of the grid voltage is accurately extracted. The performance of the proposed optimum setting algorithm for the SRF-PLL grid synchronization technique is discussed in detail and simulation results are presented.

An intelligent two‐level control of Ultrabattery for improved automatic generation control of a multi‐source deregulated power system

This article studies automatic generation control (AGC) problem of a realistic, multi-source deregulated power system with thyristor controlled phase shifter (TCPS) in the tie-line for damping the inter-area power oscillations. In this direction, an intelligent integration of a commercially available, relatively low rating efficient energy storage system in the form of Ultrabattery for AGC enhancement is proposed. Herein, a two-level supervisory cascade control scheme is designed. The supervisory controller comprises of a genetically tuned fuzzy logic controller which ensures the operation of Ultrabattery within its regime of operation while supervising a conventional main controller in the inner loop. The exchange of desired power between the power system and Ultrabattery is governed by the main controller whose parameters are tuned offline using optimization toolbox in MATLAB. To make the power system model realistic, effects of generation rate constraint, governor dead band, boiler dynamics, and communication time delay have been incorporated. Extensive simulation studies conducted on a well-known benchmark two-area power system under various market scenarios demonstrate the effectiveness of the proposed scheme. The results obtained illustrate a substantial mitigation of low magnitude oscillations with TCPS in the tie-line. Following the introduction of an Ultrabattery rated at just 1% of the area capacity in coordination with TCPS, an improvement of at least 87% in the system performance index is achieved. Finally, a sensitivity analysis validates the robustness of the proposed scheme under varying system parameters and market scenarios.

Analysis of Hybrid Fuzzy Logic Control Based PID Through the Filter for Frequency Regulation of Electrical Power System with Real-Time Simulation

In the present study, a teaching learning based optimization (TLBO) method tuned hybrid fuzzy logic control based PID through the Filter (FPIDN) is proposed for frequency regulation of the electrical power system problem. The studied electrical power system contains the non-linearity parameters like governor dead band, time delay, and generation rate constraint. The performance of TLBO is analyzed by applying a genetic algorithm (GA) method. It is observed that TLBO outperforms compared with GA. Next, an investigation has been carried out by placing static synchronous series compensator in the tie-line. It is demonstrated that TLBO outperforms GA technique in controller design problem. To confirm the capability of the recommended method, experimental commendation with the hardware-in-the-loop real-time validation based on OPAL-RT has been implemented. Finally, the performance of TLBO tuned FPIDN controller is equated with some recently suggested frequency control problem in a standard two-area system. From the simulation outcome, it is established that the suggested plan offers better compared with existing methods.

Electric vehicles participation in load frequency control based on mixed H2/H∞

Besides being new loads that would call for further capacity from fossil-fuel based Conventional Sources (CS), managing Electric Vehicles (EVs) smartly i.e. using Vehicle-to-Grid (V2G), holds the opportunity to be used for Load Frequency Control (LFC). However, there exists uncertainty in available dispatch capacity and time delay linked to charging/discharging control of individual EVs. Assessing this uncertain capacity and related delay of its response for LFC is presented first in this paper. Next, for the EVs participating in multi-objective LFC (V2G) along with CSs, a robust mixed H2/H∞ controller based on static output feedback is adopted. The system stability, i.e. bounding frequency and tie-line power to their nominal values in the presence of internal and external disturbance, is ensured by providing better reference tracking to both EVs and CSs. Case studies of a single and three-area system with EVs are tested for LFC, where the efficacy of the mixed H2/H∞ is also endorsed by the comparison with only H∞ controller. The results showed that the EVs and the adopted controller can respond effectively to the scenarios i.e. load variation, parameters uncertainties, effects of dead bands and time delays of both controller and EVs aggregator responses. It caused a decrease in the capacity burden on CS while this study open ways for the future grid to be pollution-free.

Observer-based adaptive threshold diagnosis method for open-switch faults of voltage source inverters

In this paper, the problem of open-switch faults of a voltage source inverter system is investigated. A new fault diagnosis method based on an observer and an adaptive threshold is proposed. This method only needs to utilize the signals existing in a system without the need for extra hardware circuits. First, an observer is designed on a model of a three-phase voltage source inverter system to estimate currents. Then, an adaptive threshold is designed on fault residuals, dynamics of the currents and variations of the system operating state. Moreover, the dead time and switching delay time are also included in the threshold to consider practical applications. Furthermore, to achieve on-line real-time diagnosis and to improve the reliability of the proposed method, the averages of the current residuals in a current fundamental period are defined as diagnostic variables. Finally, the reliability and effectiveness of the proposed method are verified by simulation and experiment results.

A novel fractional order proportional integral derivative plus second-order derivative controller for load frequency control

ABSTRACT This paper proposes a novel fractional order proportional integral derivative plus second-order derivative (FOPID+DD) controller for the load frequency control (LFC) of a hybrid power system (hPS). The investigated hPS incorporates conventional and certain distributed generation sources. Parameters of the proposed controller are optimised using a newly developed and powerful water wave optimisation (WWO) algorithm. The effectiveness of the proposed control scheme is established by considering multiple disturbances and nonlinearities like generation rate constraint, governor dead band and time delay related with the hPS. The performance of the proposed controller is compared with other controllers that are well studied in the literature. Simulation results reveal that the frequency dynamics of the hPS are enhanced with the proposed controller in terms of reduced frequency deviations and improved transient specifications. The sensitivity of the proposed controller is validated subject to wide variations in the hPS parameters.

Modified sine cosine algorithm-based fuzzy-aided PID controller for automatic generation control of multiarea power systems

The research paper presents implementation of a fuzzy rule and membership function-based fuzzy-aided PID controller for automatic generation control (AGC) in multiarea nonlinear power system. At the initial stage of this proposed work, a three-area nine-unit installed interconnected network is considered for developing different dynamic responses in response to AGC analysis. A modified approach named modified sine cosine algorithm (M-SCA) is proposed for tuning the gain parameters of the above-proposed fuzzy controller to produce close optimum gain values. The proposed modified algorithm is developed from its original sine cosine algorithm by improving and updating few equations which is capable of making the balance between exploration and exploitation levels of this algorithm and improving the updating quality of iteration. To impose supremacy of M-SCA technique, it is examined through convergence curves and its performance is compared with host sine cosine algorithm, genetic algorithm, and particle swarm optimization algorithm. For controller supremacy analysis, the performance of the proposed fuzzy-aided PID controller is compared with conventional I, PI, and PID controllers, and it has been revealed that proposed M-SCA-tuned fuzzy-aided PID controller exhibits better performances through different deviated responses for AGC analysis. To demonstrate most standard and supremacy of proposed approaches, finally these are tested through a five-area ten-unit system considering some physical nonlinear constraints like generation rate constraint, governor dead band, boiler dynamics and time delay. At the final observation level, the proposed fuzzy controller has gone through different sensitivity analyses with variation of different system parametric conditions and different load conditions.

Optimal design of CDM controller to frequency control of a realistic power system equipped with storage devices using grasshopper optimization algorithm

This paper presents a new robust load frequency control (LFC) technique based on an optimal design of the coefficient diagram method (CDM) in a three area thermal power system equipped with redox flow batteries (RFB). In order to emphasize on a realistic power system and obtain an accurate insight, important nonlinearities due to generation rate constraint (GRC), governor dead band (GDB) and time delay (TD) were considered. The innovation of the proposed controller in this paper is the use of a hybrid intelligent combination of a decentralized CDM technique and optimization throughout its algebraic equations. In addition, a new algorithm namely grasshopper optimization algorithm (GOA) was used to find the key parameters of the proposed controller in solving the LFC problem for the first time. Furthermore, this study applied a powerful modified objective function by considering the integral of time multiplied squared error (ITSE) criteria for both controller input signal (ACE), to minimize the area control error and output signal (Δu) to reduce the size of the actuator, settling time (Ts) to have a faster response and a function to increase the minimum damping ratio (MDR) among all eigen values. To demonstrate the effectiveness of the proposed scheme, the studied simulated power system was tested through different cases including a large step and sinusoidal load perturbations and wide uncertainty in dynamic parameters of a nonlinear power system. Comparative results have revealed the superiority of the optimal CDM technique, especially when it is equipped with RFB. In addition to graphical results, by taking into account the MDR of different control strategies, the preference of the proposed controller has become more validated. This newly developed strategy leads to a flexible and accurate controller with a powerful mathematical back up which can successfully cope with GRC, GDB and TD nonlinearities in perturbed uncertain power systems and provide fast, stable and robust dynamic responses. Thus, the proposed control strategy can be constructive and successfully applied to real world power system application.

Analysis of Dynamic Properties of VSCs Connected to Weak Grids Including the Effects of Dead Time and Time Delays

In recent years, the penetration of distributed generators (DGs) with power electronics interfaces has rapidly increased and this fact has created new challenges for the operation of power systems. In some cases, when DGs are connected via long distribution cables, an interaction between their control systems and the network may produce undesired resonant effects. This emphasizes the importance of more accurate dynamic modeling of the system to predict and prevent such events. This paper presents an integrated small-signal model of voltage source converters (VSCs) that includes the dead time and time delays implementation effects that are typically not considered in the literature. An approach based on eigenvalue and singular value decomposition is used to evaluate the impact of the network impedances on the robustness of the power system. The accuracy of the integrated small-signal model was validated by using a dedicated laboratory test network composed of 15-kVA VSCs connected to the grid via emulated distribution lines. The analysis of the implementation effects revealed their significant impact on the accuracy of the small-signal models as well as on the overall system stability. The two models that include and exclude the implementation effects are critically compared and the experimental results are provided.

Hybrid flower pollination and pattern search algorithm optimized sliding mode controller for deregulated AGC system

A new evolutionary optimisation technique, namely hybrid flower pollination and pattern search (hFPA-PS) technique is developed to tune output feedback sliding mode controller (OFSMC)for a multi-sources interconnected deregulated automatic generation control (AGC) system. The developed algorithm is justified considering popular benchmark functions. The developed algorithm is applied first time for the AGC system, to tune parameters of different classical controllers. The supremacy of recommended approach is established by competing the dynamic system performances with FPA, fruit fly optimization (FOA) and particle swarm optimization (PSO) technique for different power scenario for different classical controllers. Dynamic response of the system with hFPA-PS optimized OFSMC is established to be better than the classical controllers. The dynamic response of the system is analysed in the presence of generation rate constraint (GRC), governor dead band (GDB) and time delay. Additionally, the supremacy of recommended approach is analysed with sensitivity analysis, under uncertainty of system parameters.

Adaptive fuzzy control of MIMO nonstrict-feedback nonlinear systems with fuzzy dead zones and time delays

This paper addresses an adaptive fuzzy control for a class of multi-input and multi-output nonlinear nonstrict-feedback systems with fuzzy dead zones, time delays and immeasurable states. Combining backstepping technique with dynamic surface control, only one adaptive law is required for each subsystem, and the whole design procedure is simplified. Compared with the existing researches on multi-input and multi-output nonlinear systems, the main contributions of this paper lie in that the dead zone models of the developed nonlinear system are fuzzy and uncertain, and the systems under consideration are more general. The designed controller not only guarantees that the given target signals can be tracked within small errors, but also guarantees the boundedness of all the signals in the closed-loop system. Finally, simulation results are depicted to demonstrate the effectiveness of our proposed control algorithm.

Daylight fluctuations effect on the functioning of different daylight-linked control systems

One of the problems preventing daylight-linked controls spread is users' reluctance in accepting them. Continuous electric light oscillations, determined by control systems, can annoy users. This problem is particularly relevant for switching systems and it is strictly dependent on sky conditions: the more variable the weather is, the more frequent the oscillations are. To deepen these issues, irradiance and daylight illuminance measurements were performed in a mock-up office. Percentage daylight fluctuations (PDFs) were calculated. Then, starting from measured data, the functioning of different switching systems (differential switching, switching with switching linked time delay, switching with daylight linked time delay and solar reset switching) was simulated, in order to investigate daylight fluctuations effect on controls performances. Simulations were repeated on varying dead band and time delay, to verify the effectiveness of techniques in reducing daily switching actions. Results demonstrates that when sky is clear, PDFs are generally comprised in the ranges [-5%; 0% [ and [0%; 5% [ both outdoor and indoor; whereas, when weather changes from a sky condition to another, fluctuations can be higher than 50%. Despite the choice of the switching technique is not univocal and its effectiveness strictly depend on specific indoor daylight availability, differential switching associated with a switching linked time delay turns out to be the strategy more adaptable to different cases. Moreover, not always the increment of the dead band extent or time delay corresponds to a reduction of the daily amount of switching actions.

Study on Comprehensive Analysis and Compensation for the Line Current Distortion in Single-Phase Three-Level NPC Converters

Providing a sinusoidal line current with few low-order harmonics is important for power converters. First, the influence mechanisms of multifactors for the line current distortion in single-phase three-level neutral point clamped converters are analyzed in theory. Second, the corresponding compensation methods for various factors are discussed, respectively. Particularly, the phenomenon that deadtime effects on harmonics is revealed by the theoretical derivation of Fourier series, and a corresponding quantitative calculation method is proposed and used to solve the compensation component of the deadtime delay. The detailed and strict mathematical deduction provides an alternative theoretical system for the quantitative analysis and compensation of deadtime and forward voltage drops effects. As for the component to compensate the unsteady forward voltage drops, it is online computation with current variations. Then, a comprehensive distortion compensation method by injecting offset voltage in the modulated signal is proposed to improve the line current waveform quality. Finally, simulation results verify the correctness of the quantitative calculation of deadtime effect on harmonics, and experimental tests verify that the proposed method can effectively reduce total harmonic distortion and improve waveform quality of the line current.

Differential evolution algorithm based tilt integral derivative control for LFC problem of an interconnected hydro-thermal power system

Conventional control techniques such as proportional integral (PI) control and proportional integral derivative (PID) control are widely used as the load frequency controller in power system control applications; however, the increase in complexity of the power system is degrading the performance of classical control. Therefore, in this paper a new control approach using fractional calculus has been proposed for the load frequency control problem of two-area hydro-thermal power system. The paper presents an interconnected hydro-thermal power system working under different operating conditions introduced in the form of various nonlinearities. Four case studies have been presented in this paper considering transient analysis with (i) different loading conditions, (ii) parameter variations, (iii) different nonlinearities (governor dead band nonlinearity, time delay and generation rate constraints), and (iv) superconducting magnetic energy storage (SMES) device. A tilt integral derivative (TID) control has been presented as a secondary controller to stabilize the frequency deviations occurring in the two-area power system with the above-mentioned different operating conditions. The parameters of TID controller have been optimized using a differential evolution algorithm which solves an optimization problem formulated using the integral of time-weighted absolute error (ITAE) performance index. In addition, a comparison of dynamic system response obtained using TID control and PID control has been presented, which focusses on the better performance of TID control over PID control in an interconnected power system.

A hybrid stochastic fractal search and local unimodal sampling based multistage PDF plus (1 + PI) controller for automatic generation control of power systems

This paper proposes to use a hybrid Stochastic Fractal Search (SFS) and Local Unimodal Sampling (LUS) based multistage Proportional Integral Derivative (PID) controller consisting of Proportional Derivative controller with derivative Filter (PDF) plus (1+Proportional Integral) for Automatic Generation Control (AGC) of power systems. Initially, a single area multi-source power system consisting of thermal hydro and gas power plants is considered and parameters of Integral (I) controller is optimized by Stochastic Fractal Search (SFS) algorithm. The superiority of SFS algorithm over some recently proposed approaches such as optimal control, Differential Evolution (DE) and Teaching Learning Based Optimization (TLBO) is demonstrated. To improve the system performance further, LUS is subsequently employed. The study is further extended for different controllers like PID, and proposed multistage PID controller and the superiority of multistage PID controller over conventional PID controller structure is demonstrated. The study is further extended to a two-area six unit multi-source interconnected power system and the superiority of proposed approach over, TLBO and optimal control is demonstrated. Finally the study is extended to a three unequal area system power system with appropriate nonlinearities such as Generation Rate Constraint (GRC), Governor Dead Band (GDB) and time delay. From the analysis, it is found that hybrid SFS–LUS algorithm is superior to the original SFS algorithm and substantial improvement in system performance are realized with proposed multistage PID controller over conventional PID controller structure.

Symbiotic organism search algorithm applied to load frequency control of multi-area power system

In this article, a novel powerful metaheuristic optimization technique called symbiotic organism search (SOS) is proposed for the first time to solve the load frequency control problem (LFC). SOS pretends the symbiotic interaction strategies accepted by an organism to sustain in the ecosystem. Initially, an interconnected two-area reheat thermal power plant equipped with proportional–integral–derivative (PID) controller is considered for design and analysis. PID controller gains are optimally selected using SOS algorithm employing integral time absolute error based fitness function. To confirm the superiority of SOS algorithm, an extensive comparative analysis is performed with some newly published optimization methods reported in the literature. Time domain simulation results show that the dynamic stability of the concerned power system is effectively enhanced with SOS. Furthermore, the performance of the proposed method is appraised by changing system loading settings and system constraints in the range of $$\pm 50\% $$ . To authenticate the tuning ability of proposed SOS algorithm, the study is extended to two more test systems, namely (1) an unequal nonlinear three-area power system and (2) two-area multi-unit thermal-hydro-wind-diesel power plant including generation rate constraint, governor dead band, boiler dynamics, and time delay nonlinearities. Comparison with existing LFC schemes validates the efficacy of SOS algorithm.

Grey Wolf Optimization to Solve Load Frequency Control of an Interconnected Power System

In this article, a novel optimization algorithm called grey wolf optimization (GWO) with the theory of quasi-oppositional based learning (Q-OBL) is proposed for the first time to solve load frequency control (LFC) problem. An equal two-area thermal power system equipped with classical PID-controller is considered for this study. The power system network is modeled with governor dead band and time delay nonlinearities to get better insight of LFC system. 1% load perturbation in area-1 is considered to appraise the dynamic behavior of concerned power system. Integral time absolute error and least average error based fitness functions are defined for fine tuning of PID-controller gains employing the proposed method. An extensive comparative analysis is performed to establish the superiority of proposed algorithm over other recently published algorithms. Finally, sensitivity analysis is performed to show the robustness of the designed controller with system uncertainties.

Steady-State Dead-Time Compensation in VSI

The performance of Voltage Source Inverter (VSI) is affected by power semiconductor nonlinearities, dead time, and control delay. The compensation of these nonlinear effects is necessary to meet requirements in terms of current quality and high efficiency, especially for grid-connected power conversion systems. In this paper, the effects of nonlinearities are widely analyzed and a new compensation technique for a steady-state current-controlled VSI is proposed. It is based on a step-by-step voltage compensation on the basis of the current error evaluated within each control interval. As a result, a complete compensation is achieved within a whole period of the fundamental. To cope with the zero-current clamping effect, the proposed compensation technique is implemented in a recursive way. For slow-dynamic applications, such as photovoltaic systems, this method allows achieving high performance with very low computational requirements.