Random Load Disturbances Research Articles

Optimal CC-2DOF(PI)-PDF controller for LFC of restructured multi-area power system with IES-based modified HVDC tie-line and electric vehicles

This article is introducing an optimal cascaded two-degree of freedom proportional-integral (2DOF(PI)) and proportional-derivative with filter (PDF) controller, i.e., CC-2DOF (PI)-PDF for load frequency control (LFC) mechanism. The designed controller increases the degree of freedom and rejects disturbances faster with fewer dynamics. Further, the application of an opposition-based volleyball premier league algorithm (OVPLA) has been explored to optimize the designed controller's parameters. The proposed LFC mechanism has been studied on a two-area thermal-hydro-gas restructured power system. The thermal system present in each area is equipped with generation rate constraints (GRC) for more realistic analysis. The performance of the suggested OVPLA optimized 2DOF(PI)-PDF controller has been verified over several classical controllers and algorithms separately for step and random load disturbances. Moreover, accurate modeling of the HVDC tie-line and inertia emulation strategy (IES) is discussed, and the power system’s inertia enhancement is verified. This article also highlights the ancillary services of electric vehicles (EVs) and distributed generations (DGs) to tackle any contract violation in the power system. Next, the proposed LFC mechanism's efficacy has been validated on extending a three-area power system. Finally, several case studies and comparative performance analysis with published literature demonstrate the effectiveness and efficiency of investigated LFC in handling any load disturbances.

A Novel Sooty Terns Algorithm for Deregulated MPC-LFC Installed in Multi-Interconnected System with Renewable Energy Plants

This paper introduces a novel metaheuristic approach of sooty terns optimization algorithm (STOA) to determine the optimum parameters of model predictive control (MPC)-based deregulated load frequency control (LFC). The system structure consists of three interconnected plants with nonlinear multisources comprising wind turbine, photovoltaic model with maximum power point tracker, and superconducting magnetic energy storage under deregulated environment. The proposed objective function is the integral time absolute error (ITAE) of the deviations in frequencies and powers in tie-lines. The analysis aims at determining the optimum parameters of MPC via STOA such that ITAE is minimized. Moreover, the proposed STOA-MPC is examined under variation of the system parameters and random load disturbance. The time responses and performance specifications of the proposed STOA-MPC are compared to those obtained with MPC optimized via differential evolution, intelligent water drops algorithm, stain bower braid algorithm, and firefly algorithm. Furthermore, a practical case study of interconnected system comprising the Kuraymat solar thermal power station is analyzed based on actual recorded solar radiation. The obtained results via the proposed STOA-MPC-based deregulated LFC confirmed the competence and robustness of the designed controller compared to the other algorithms.

Load Frequency Control of a Multi-Microgrid System Incorporating Electric Vehicles

Owing to high cost of conventional energy storage systems, battery of electric vehicles (EVs) is now being considered as their partial replacement to facilitate the demand side response. EVs can act as controllable bidirectional sources to restrain the frequency deviations in power system via vehicle-to-grid control. Consequently, this article proposes a load frequency control (LFC) scheme of a multi-microgrid (MMG) system incorporating EVs. A tilt integral derivative (TID) controller is enforced as the LFC controller in the proposed MMG system. To optimize the gains of the TID controller, a recently developed atom search optimization algorithm is implemented as a novel initiative. Diverse loading patterns that include random, sinusoidal, and pulse load disturbance patterns are considered in the MMG to establish the competence of the proposed control scheme. Simulation results reveal that the proposed LFC scheme enhances the dynamic responses of the MMG system in terms of attenuated oscillations, improved transient specifications and minimized objective function in the frequency and tie-line power deviations, and thus, satisfies the LFC requirements. The results are compared with some standard algorithms. Lastly, sensitivity of the proposed controller is validated subject to ±30% variation in various MMG parameters.

Load Frequency Control for Multi-Area Power Plants with Integrated Wind Resources

To provide a more practical method of controlling the frequency and tie-line power flow of a multi-area interconnected power system (MAIPS), a state observer based on sliding mode control (SOboSMC) acting under a second-order time derivative is proposed. The proposed design is used to study load frequency control against load disturbance, matched and mismatched uncertainty and parameter measurement difficulties of power systems that exist in the modern power plant, such as multi-area systems integrated with wind plants. Firstly, the state observer is designed to optimally estimate system state variables. The estimated states are applied to construct the model of the MAIPS. Secondly, a SOboSMC is designed with an integral switching surface acting on the second-order time derivative to forcefully drive the dynamic errors to zero and eliminate chattering, which can occur in the first-order approach to sliding mode control. In addition, the stability of the total power system is demonstrated with the Lyapunov stability theory based on a new linear matrix inequality (LMI) technique. To extend the validation of the proposed design control for practical purposes, it was tested in a New England system with 39 bus power against random load disturbances. The simulation results confirm the superiority of the proposed SOboSMC over other recent controllers with respect to overshoot and settling time.

Non-Fragile Approach for Frequency Regulation in Power System With Event-Triggered Control and Communication Delays

This article proposes a non-fragile control model approach for the design of an event-triggered control (ETC) for frequency and tie-line power regulation in a networked power system with communication delays. The proposed non-fragile control approach can tolerate controller parameter variations without any degradation in the system performance. The event condition is designed based on the relationship between the ETC and the non-fragile system. The effectiveness of the proposed design is validated with three-area interconnected power systems under load disturbances. The superiority of the proposed work is shown by comparative analysis with recently reported works. Furthermore, system robustness is validated with random step load disturbance, matched uncertainty, power system nonlinearities, communication link noise, integration of renewable energy resources, and with the IEEE 39 bus system. The closed-loop system stability is theoretically proved using the Lyapunov candidate function and verified by simulations.

Design of Cascaded PI-Fractional Order PID Controller for Improving the Frequency Response of Hybrid Microgrid System Using Gorilla Troops Optimizer

This paper proposes a cascaded Proportional Integral-Fractional Order Proportional-Integral-Derivative (PI-FOPID) controller to improve the frequency response of a hybrid microgrid system. The optimum gains of the proposed controller are fine-tuned using Gorilla Troops Optimizer (GTO) which is a recent metaheuristic optimization algorithm. The case study is a two-area microgrid system that contains diesel generators, various renewable energy sources such as photovoltaic and wind generation systems, as well as different energy storage devices. Moreover, real wind speed and solar irradiance measurements have been collected for proper system modeling. The performance of the proposed cascaded PI-FOPID controller is compared to the single structure fractional order PID (FOPID) controller based on GTO and numerous other optimization techniques presented in the previous literature such as Genetic Algorithm and Particle Swarm Optimization. The robustness of the proposed cascaded PI-FOPID controller is investigated under different scenarios such as different step load perturbations, random load disturbances, and renewable energy sources variation. The simulation results are carried out using MATLAB/Simulink. The results show that the proposed controller provides an improvement in the maximum overshoot/undershoot and settling time of 99.8% and 75.9%, respectively, compared to other competing techniques.

Improved model predictive load frequency control of interconnected power system with synchronized automatic generation control loops

BackgroundAutomatic generation control (AGC) of multi-area interconnected power system (IPS) is often designed with negligible cross-coupling between the load frequency control (LFC) and automatic voltage regulation (AVR) loops. This is because the AVR loop is considerably faster than that of LFC. However, with the introduction of slow optimal control action on the AVR, positive damping effect can be achieved on the LFC loop thereby improving the frequency control. In this paper, LFC synchronized with AVR in three-area IPS is proposed. Model predictive controller (MPC) configured in a dense distributed pattern, due to its online set-point tacking is used as the supplementary controller. The dynamics of the IPS subjected to multi-area step and random load disturbances are studied. The efficacy of the developed scheme is ascertained by simulating the disturbed system in MATLAB/Simulink.ResultsBased on the comparative analysis on the system responses, it is established that by cross-coupling the LFC loop with AVR, reductions of 66.45% and 59.09% in the frequency and tie-line power maximum deviations respectively are observed, while the respective settling times are found to be reduced by 29.68% and 22.77% when compared with the uncoordinated control scheme. In addition, the standard deviation and variance of the integral time absolute error of the system’s responses have reduced by 23.21% and 20.83% respectively compared to those obtained in a similar study.ConclusionsThe reduction in the maximum deviations and settling times in the system states indicates that introducing the voltage control via AVR loop has improved the frequency control significantly. While the lower standard deviation and variance of the integral time absolute error signify improvement in the robustness of the developed algorithm. However, this improvement is at the detriment of the controller size and computational complexity. In the uncoordinated control scheme, the control vector is one-dimensional, while in the coordinated scheme, the control vector is two-dimensional for each CA.

Optimal model predictive control for LFC of multi-interconnected plants comprising renewable energy sources based on recent sooty terns approach

In this paper, an optimal model predictive control (MPC) is tuned using recent optimizer named sooty terns optimization algorithm (STOA). The proposed control is employed to design load frequency control (LFC) installed in interconnected system including different renewable energy sources (RESs). The proposed method is utilized to identify the MPC optimal parameters to minimize the integral time absolute error (ITAE) of the frequencies and tie-line power deviations. The analysis is performed on three multi-interconnected systems, the first one includes two units of thermal and PV with maximum power point tracking (MPPT). The others include linear/nonlinear three-interconnected system with/without superconducting magnetic energy storage (SMES). The nonlinear model is implemented by considering generation rate constraint (GRC) and governor dead-band (GDB). Moreover, the proposed MPC-LFC is investigated under system parameters’ uncertainties. Furthermore, random wind speed and load disturbance are analyzed for multi-interconnected system. The performance of the proposed MPC-LFC optimized via STOA is compared with the proportional-integral (PI) controller designed via firefly algorithm (FA), genetic algorithm (GA), MPC with FA, stain bower braid algorithm (SBO), multi-verse optimizer (MVO), and intelligent water drops algorithm (IWD). The obtained results confirmed the competence of the proposed STOA in designing the optimal MPC-LFC compared to the others.

Adaptive virtual-inertia control and chicken swarm optimizer for frequency stability in power-grids penetrated by renewable energy sources

In this article, a control scheme based on chicken swarm optimizer (CSO) in cooperation with adaptive virtual-inertia control (AVIC) is investigated. The proposed control scheme aims at improving the frequency stability of an interconnected power system which is penetrated by renewable energy sources. The CSO is applied to produce the best values of the gains of the adapted standard proportional-integral-derivative (PID) controllers and required parameters of AVICs. Various scenarios are addressed in this study such as applications of sudden step load disturbances and severe variations in the inertia of the system. In addition, realistic conditions such as uncertainties of tidal power source and random load disturbances are demonstrated. Compulsory assessments with subsequent discussions to evaluate the results of the CSO are made. The proposed CSO–AVIC based control method is verified by comparisons with well-matured interesting algorithms such as differential evolution and particle swarm optimizers. Various quality specifications of the dynamic responses and the demonstrated results indicate clearly the viability of the proposed CSO–AVIC based on control scheme. It can be emphasized that the utilization of AVIC along with PID controllers are significantly improved the system dynamic performances and their dynamic response specifications meet the terms of standard acceptable criteria’s.

Nonlinear disturbance observer based adaptive super twisting sliding mode load frequency control for nonlinear interconnected power network

AbstractThis article revisits the study of load frequency control (LFC) problem in an interconnected nonlinear power network under mismatched disturbance. Unlike previous works, a more realistic interconnected power network with nonlinear coupling between control areas and also including nonlinearities like generation rate constraint (GRC) and governor dead band (GDB) is under study. An adaptive super twisting sliding mode controller (ST‐SMC) is designed based on system states and estimated disturbance. The nonlinear disturbance observer (NDO) estimates the mismatch between the electrical and mechanical power and then the estimated value is employed in the controller design to compensate the disturbance. The proposed control scheme ensures faster frequency and tie‐line power stabilization compared with techniques existing in the literature. The robustness of the proposed design is validated under random varying step load disturbance and with two area four machine Kundur's test system. The closed loop system stability is theoretically proved using the Lyapunov function. Simulation results confirm the effectiveness of the proposed design in a two‐area interconnected power network.

Pathfinder algorithm optimized fractional order tilt-integral-derivative (FOTID) controller for automatic generation control of multi-source power system

This paper introduces a fractional order tilt-integral-derivative (FOTID) controller which is structurally analogous to fractional order proportional-integral-derivative controller in a power system for solving automatic generation control (AGC) problem. It is optimized by a recent metaheuristic optimizer called pathfinder algorithm (PFA). An interconnected two-area power system model comprising of multi-sources like thermal, hydro and gas generating units including physical constraints namely, governor dead band (GDB) and generation rate constraint (GRC) are taken into consideration for the study. The efficiency of the proposed controller for AGC is shown by comparing it with PFA optimized tilt-integral-derivative (TID) and proportional-integral-derivative (PID) controllers with integral of time multiplied absolute error (ITAE) taken as the objective function. Simulation study supports the claim that the proposed controller provides better dynamic responses as compared to the others. Sensitivity and robust analyses are done to demonstrate the effectiveness of the proposed PFA optimized FOTID controller to a wide variation in system parameters, at different step load and random load disturbances.

An Improved ACO Algorithm Optimized Fuzzy PID Controller for Load Frequency Control in Multi Area Interconnected Power Systems

In this paper, an Improved Ant Colony Optimization (IACO) algorithm optimized fuzzy PID (FPID) controller is proposed for Load Frequency Control of multi area systems. The nonlinear incremental evaporation rate and improvement of pheromone increment updating are proposed in the IACO algorithm to improve the quality of solution. And, a modified objective function using integral time multiply absolute error (ITAE), overshoot, undershoot and settling time with appropriate weight coefficients is proposed to improve the performance of the controller. Initially, a two-area non-reheat thermal system is applied and the FPID controller parameters are optimized by the IACO algorithm with five different objective functions. The modified objective function has better performances than four conventional objective functions. To demonstrate the robustness of the proposed control method, sensitivity analysis is implemented under wide variation of operating conditions and system parameters. Further, the proposed approach is also extended to two-area four-sources hydro thermal power system with/without High Voltage Direct Current (HVDC) link. The superiority of the proposed approach is shown by comparing the results with ZN, GA and hPSO-PS algorithms. The robustness of the proposed method is verified under random load disturbances. Finally, the proposed approach is extended to a two-area power system with governor dead band nonlinearity and results show that the proposed approach can cope with nonlinearity well. The results obtained from all simulations show that the proposed algorithm and modified objective function achieves better performances, such as minimum objective values (ITAE = 0.0255, ITSE = 9.30e-5, ISE = 1.91e-4 and IAE = 0.0273) obtained for the two-area non-reheat thermal system.

Firefly Algorithm Based PID Controllers for Automatic Load Frequency Control In Different Power Systems

The automatic load frequency control problem has been addressed in different power system areas such as single area, two area and three areas. Each area contain one thermal unit, one hydro unit and one gas unit. Initially, single-area three-unit system is addressed to analyze without and with PID controller for 10% of step load perturbation. After that, a two-area six-unit and three area-nine-unit systems are acknowledged and analyzed the effectiveness of PID controller. At last, capability of the proposed controller is assessed with a random step load disturbance. The total study was taken up in MATLAB/SIMULINK environment.

Impact of Flexible AC Transmission System Devices on Automatic Generation Control with a Metaheuristic Based Fuzzy PID Controller

The present work proposes a teaching–learning-based optimization (TLBO)-tuned fuzzy proportional-integral-derivative (PID) controller of two-area hydro-thermal generating units for automatic generation control (AGC). The proposed system takes into account the physical constraints such as transport delay (TD), generation rate constraint (GRC), and governor dead band (GDB) nonlinearities. Firstly, fuzzy PID controllers were designed for both the areas and their gains were optimized using various minimization objective function criteria. Furthermore, applications of flexible alternating current transmission system (FACTS) devices such as static synchronous series compensator (SSSC), thyristor-controlled series capacitor (TCSC), thyristor-controlled phase shifter (TCPS), and unified power flow controller (UPFC) were investigated by integrating FACTS devices in appropriate locations of the system. The simulation results revealed that the minimum objective values were attained when the UPFC was placed in the system. Lastly, robustness analysis was done to observe the capability of the proposed controller with UPFC by changing system parameters and considering random load disturbances.

Robust Higher Order Observer Based Non-linear Super Twisting Load Frequency Control for Multi Area Power Systems via Sliding Mode

The article focuses on the design of higher order sliding mode observer (HOSMO) based super twisting sliding mode control (ST-SMC) for load frequency problems in an interconnected multi area power systems. A sudden load disturbance in any area can cause deviations in frequency and tie line power from their desired values. The proposed design functions for the improved overall performance of the system. High frequency oscillations (chattering) which is the main operational problem with SMC is investigated through ST-SMC. Firstly, with inherent advantages of robustness, insensitivity to uncertainties and disturbances, the HOSMO estimates the system states from the output and control signal. Secondly, the ST-SMC acts only on the first time derivative of sliding surface to ensure finite time convergence of frequency and tie line power deviations. The supremacy of the proposed design compared to modern state of the art lies in improved transient and steady state behavior, robustness and chattering free control without any loss in control accuracy. Furthermore, performance indices like integral square error (ISE), integral absolute error (IAE) and integral time absolute error (ITAE) for the said controller are found to be lesser compared to that of linear and nonlinear SMC. The said controller also results in acceptable frequency deviation when validated under random step load disturbances, parameter uncertainties, with an integration of renewable energy resource and nonlinearities in power systems like generation rate constraints (GRC) and governor dead band (GDB).

Effect of energy storage systems on automatic generation control of interconnected traditional and restructured energy systems

During major disturbances in electric power system (PS) penetrated with renewable energy sources, primary and supplementary automatic generation control (AGC) strategies usually show inefficiency in mitigating the frequency and power oscillations because of sluggish control action. The frequency and power deviations should be controlled to retain the generation-demand balance, which reinforce the quality and stability of overall PS. The fast-acting energy storage systems (ESSs) having very small time constants like capacitive energy storage (CES) and redox flow battery (RFB) are utilised in this study to improve these dynamic responses. To conduct the analysis, initially, a two-area nonreheat thermal PS with extra generations from wind turbine system (WTS) and dish-stirling solar thermal system (DSTS) is explored extensively, and then to validate the efficacy of the method, the approach is tested on two-area nonreheat thermal system having governor deadband (GDB) nonlinearity, reheat thermal, and restructured multisource thermal gas systems. An imperialist competition algorithm (ICA) optimised fuzzy PID-filter-(1 + PI) controller named as FPIDF-(1 + PI) is utilised as supplementary controller, and its performance with CES/CES-RFB is compared with ICA-optimised FPIDF with/without CES and existing optimal PI/PID/PIDF/FPID controller without CES. Investigation of dynamic responses for sudden variation in power demand unveils the superiority of the control approach compared with others regarding settling time, peak undershoot, and performance index. Analysing the impact of ESSs on the responses divulges that the amalgamation of CES-RFB in PS imparts better system dynamics. The robustness analysis suggests that ICA-optimised controller with ESSs performs excellently and robustly for ±25% variation in PS parameters, random load disturbances, and nonlinearities.

Differential evolution algorithm tuned tilt integral derivative controller with filter controller for automatic generation control

A differential evolution (DE) tuned tilt integral derivative controller with filter (TIDF) has been implemented to a multi area reheat thermal power system for automatic generation control by taking the physical constraints like generation rate constraint and governor dead band nonlinearity. Initially, dissimilar integral controllers are considered in each area and the integral controller gains have been optimized by integral of time multiplied by absolute value of error (ITAE) criterion exploiting different strategies of DE algorithm. In next step, the control parameters such as step size and crossover probability of DE for the best strategy can be chosen with multiple iterations of the algorithm systematically for variation in each control parameter and DE proposes the control parameters. Further, PI/PID/TIDF type controller schemes have been modified and their gains have been optimized by optimal DE. Furthermore, to improve the transient system response, TIDF controller coordinated unified power flow controller (UPFC) has been investigated. The simulation results reveal that the minimum ITAE value is obtained when UPFC is placed in area-5 only. Finally, sensitivity analysis has been done by changing the operating load conditions along with the time constants of system parameters, from the simulation results it has been examined that there is no need to reset the controller parameters from their nominal setting for these variations. The proposed control scheme effectiveness is also observed by considering random step load disturbance and sinusoidal load disturbance.

Robust fixed-time sliding mode control for fractional-order nonlinear hydro-turbine governing system

This paper proposes a nonlinear sliding mode controller for effective fixed-time stabilization of a hydro-turbine governing system (HTGS). The HTGS is a highly nonlinear, multi-variable coupled and non-minimum phase system to maintain frequency stability by regulating the generation output in response to load variations. The state trajectories of HTGS under random load disturbances exhibit unstable behaviours on the rotor angle, rotor speed, and guide vane opening, which would affect the stable operation of hydroelectric stations. In the proposed approach, the fractional calculus technique is adopted to model the nonlinear dynamics of fractional-order hydro-turbine governing system (FOHTGS). In order to validate the system stabilization and convergence within a bounded time, a robust sliding mode controller is proposed to force the FOHTGS to reach the equilibrium point based on the fixed-time stability and Lyapunov stability theories. The proposed controller can guarantee the superior stabilization of FOHTGS with the bounded and quantifiable convergence time, and thus overcome the drawback of finite-time controllers whose convergence characteristics are heavily dependent on the initial conditions. Finally, numerical simulations have been implemented to confirm the effectiveness and superior performance of the fixed-time controller compared with the existing finite-time control methods.

Black hole optimised cascade proportional derivative-proportional integral derivative controller for frequency regulation in hybrid distributed power system

This manuscript presents a novel black hole optimised (BHO) proportional derivative-proportional integral derivative controller (PD-PID) is provided for the optimal solution of the frequency regulation of hybrid power system. At first, a two area power system is considered in which area-1 having thermal, distributed units and in area-2 includes thermal, hydel and nuclear units. Appropriate nonlinearities such boiler dynamics, governor dead band (GDB) and generation rate constraint (GRC) are considered. In the next step, PD-PID controller is considered as a secondary controller and its preeminence is shown by comparing with proportional integral derivate (PID) and proportional integral double derivate (PIDD) controllers for the same model having integral time multiplied absolute error (ITAE) as an error function. Finally, sensitivity of the proposed controller is investigated over a wide variation of system parameters and loading condition. For more examination of the proposed controller is also analysed under random step load and sinusoidal disturbances.

Black hole optimised cascade proportional derivative-proportional integral derivative controller for frequency regulation in hybrid distributed power system

This manuscript presents a novel black hole optimised (BHO) proportional derivative-proportional integral derivative controller (PD-PID) is provided for the optimal solution of the frequency regulation of hybrid power system. At first, a two area power system is considered in which area-1 having thermal, distributed units and in area-2 includes thermal, hydel and nuclear units. Appropriate nonlinearities such boiler dynamics, governor dead band (GDB) and generation rate constraint (GRC) are considered. In the next step, PD-PID controller is considered as a secondary controller and its preeminence is shown by comparing with proportional integral derivate (PID) and proportional integral double derivate (PIDD) controllers for the same model having integral time multiplied absolute error (ITAE) as an error function. Finally, sensitivity of the proposed controller is investigated over a wide variation of system parameters and loading condition. For more examination of the proposed controller is also analysed under random step load and sinusoidal disturbances.