LFC System Research Articles

Asymmetric LKF approach for stability analysis of multi-area load frequency control systems with time-varying delays

ABSTRACT The widespread use of communication networks in power systems to send and receive control signals causes time delays in the feedback loop. Improper handling of these delays might degrade controller performance or cause system instability. This work presents new stability criteria that are less conservative in analysing the influence of delays on the stable operation of PI controller-based multi-area power systems with uncertainties and disturbances. An asymmetric Lyapunov-Krasovskii functional technique is used to reduce conservatism by relaxing the condition that all matrices associated with the LKF formulation need not be symmetric or have positive definiteness. In contrast, the symmetric LKF requires all matrices to be symmetric. Two tight-bound integral inequalities are implemented to compute the quadratic integral terms included in the derivative of asymmetric LKF. The less conservative stability conditions are derived for multi-area LFC systems subjected to delays, parameter uncertainties, and disturbances by utilising asymmetric LKF. The superiority of the proposed stability criterion is determined both theoretically and through simulation. According to the analysis, the proposed stability criterion provides higher delay margins than existing techniques.

Distributed optimal load frequency control for multi-area power systems with controllable loads

With the proliferation of distributed energy resources, power imbalance may fluctuate rapidly with a large amount, which may make the conventional frequency control scheme not respond fast to the fluctuation and operate in an economically inefficient manner. This paper proposes a distributed optimal load frequency control (DOLFC) scheme for multi-area power systems with controllable loads, which optimally dispatches generators and controllable loads to participate the frequency regulation with cost minimization. It can restore the nominal frequency and only needs local measurements and local communication for implementation. With the DOLFC, we prove that the closed-loop LFC system asymptotically converges to an equilibrium point which minimizes the control cost of generators and controllable loads, and the equilibrium point is unique if and only if the multi-area power network is a tree. Compared with the conventional LFC and economic LFC in literature, the proposed DOLFC has higher economic efficiency and better control performance. Finally, a four-area power system is employed to illustrate the effectiveness of the proposed scheme by numerical simulations.

Pilot testing of water utilization for integrated solar energy storage and power production using linear Fresnel collector and organic Rankine cycle

This work presents a new method of utilizing water as thermal energy storage to improve the capacity factor of integrated linear Fresnel collector – organic Rankine cycle (LFC-ORC). A new process flow diagram has been proposed to manage overnight operation of the ORC relying on thermal energy storage in water. Pilot testing of 10 kW capacity of LFC-ORC process under arid and desert conditions of Arabian Gulf operating conditions (Qatar) is also reported. A thermodynamic analysis has been performed based experimental evaluation and process simulation of the LFC-ORC production and efficiency. The LFC-ORC operations at storage temperatures of 170 °C showed peak electricity production of 6.76 kW (38 W/m2 aperture area of LFC) whereas 1st law, and 2nd law efficiencies were 6 % and 19 %, respectively. An operational strategy is proposed to generate 5 kW over a period of about 12 h using 10 m3 storage capacity. The developed process simulation program showed that two LFC systems, each 176 m2 aperture area, equipped with three storage tanks each 10 m3, must be installed to generate 5 kW electricity for 24 h. The proposed system can be upscaled to any size as per end-user needs. The new system design would be subjected to further optimization and feasibility to cope with the development of the ORC and LFC efficiency in the future.

False Data Injection Attacks on LFC Systems: An AI-Based Detection and Countermeasure Strategy

False Data Injection Attacks on LFC Systems: An AI-Based Detection and Countermeasure Strategy

An Improved Integral-Based Adaptive Event-Triggered Frequency Regulation on a Dual-Link LFC System Under Mixed Attacks

An Improved Integral-Based Adaptive Event-Triggered Frequency Regulation on a Dual-Link LFC System Under Mixed Attacks

Recommendations of Optimal Sampling Rates for Discrete Mode POF Based Wind Integrated LFC System

Recommendations of Optimal Sampling Rates for Discrete Mode POF Based Wind Integrated LFC System

Computation of stability boundary locus of robust PID controller for time delayed LFC system

Computation of stability boundary locus of robust PID controller for time delayed LFC system

Adaptive memory-based event-triggering resilient LFC for power system under DoS attack

Considering denial-of-service (DoS) attacks in the communication network, this work develops the adaptive memory-based event triggering resilient LFC approach for multi-area power systems with wind power. First of all, the impact of each DoS attack is evaluated by the amount of continual information loss it causes. Meanwhile, an adaptive memory event triggering mechanism (AMETM) is proposed, where the dynamic event triggering parameter and the triggering mechanism are all related to the historical transmitted states. Then, based on the proposed AMETM and DoS attacks, a sampling-data LFC model is established. In order to construct the LFC scheme with the desired faster state response, the exponential decay index is introduced as a performance index. Next the exponential stability problem of LFC sampling model is transformed into the asymptotic stability problem of polynomial uncertain system. Secondly, the exponential stability criterion and the memory controllers design method are obtained by bilateral closed-loop Lyapunov–Krasovskii functional (LKF) and LMI technology, which ensure the proposed memory control scheme can quickly stabilize the LFC system under a longer DoS attack. Lastly, a one-area typical LFC system is presented to verify the superiority and effectiveness of the proposed AMETM. The resilient control with fast state response and DoS attack is studied by two-areas LFC systems with wind power.

Leader Harris Hawks algorithm based optimal controller for automatic generation control in PV-hydro-wind integrated power network

• A novel attempt has been put together to design a Model Predictive Control based on the leader Harris Hawks Optimization approach for a PV integrated LFC system. Further, a combined AVR-LFC loop has been designed for a PV, wind and hydro integrated hybrid power system. • The validation of the controller's better performance has been obtained through a thorough comparative analysis where the transient response attributes from the proposed controller have been compared with the exiting controllers available in the literature. Also, the convergence mobility of the proposed LHHO optimizer has been compared with HHO, WOA, and PSO algorithms. • To further strengthen the frequency stability of the network, the authors have proposed and implemented the virtual inertia and capacitive energy storage devices in association with the LHHO-MPC controller. • The robust nature of the proposed controller algorithm has been assessed under different test case scenarios where the step load perturbation (SLP) values have been varied randomly, and the stochastic load model has been considered. Also, various nonlinearities and reduced inertia cases have been presented to show the efficiency of the proposed LHHO-MPC controller working in coordination with CES and VI units. The work in this manuscript aims at designing a novel control strategy based on the Model Predictive Controller aided with Leader Harris Hawks Optimization (MPC-LHHO) algorithm for the regulation of frequency and voltage in renewable penetrated power systems. Herein, two cases have been considered where the first case discusses the frequency stabilization in a thermal power system linked with the solar photovoltaic (PV) plant. Subsequently, the second case features the simultaneous voltage and frequency regulation in a hybrid interconnected power system including thermal, wind, diesel, photovoltaic, and hydro generation units. Additionally, for both cases, the proposed MPC-LHHO algorithm has been evaluated in coordination with the capacitive energy storage and virtual inertia units. Furthermore, the stability analysis of the controlled PV-thermal system has been conducted using eigenvalues and pole-zero plots. In both cases, the effectiveness of the proposed algorithm has been tested after considering diverse scenarios including random loading, nonlinearities, time delays, reduced inertia and stochastic variations in load. For all these cases the presented algorithm has given a stable response and has ensured proper regulation of voltage and frequency in the renewable integrated power system network.

LSTM Recurrent Neural Network-Based Frequency Control Enhancement of the Power System with Electric Vehicles and Demand Management

Due to the unpredictable and stochastic nature of renewables, current power networks confront operational issues as renewable energy sources are more widely used. Frequency stability of modern power systems has been considerably harmed by fast and unpredictable power variations generated by intermittent power generation sources and flexible loads. The main objective of the power system frequency control is to ensure the generation demand balance at all times. In reality, obtaining precise estimates of the imbalance of power in both transmission and distribution systems is challenging, especially when renewable energy penetration is high. Electric vehicles have become a viable tool to reduce the occasional impact of renewable energy sources engaged in frequency regulation mainly because of vehicle-to-grid technologies and the quick output power management of EV batteries. The rapid response of EVs enhances the effectiveness of the LFC system significantly. This research work investigates a deep learning strategy based on a long short-term memory recurrent neural network to identify active power fluctuations in real-time. The new approach assesses power fluctuations from a real-time observed frequency signal precisely and quickly. The observed power fluctuations can be used as a control reference, allowing automatic generation control to maintain better system frequency and ensure optimum generation cost with the use of demand management techniques. To validate the suggested method and compare it with several classical methods, a realistic model of the Indian power system integrated with distributed generation technology is used. The simulation results clearly indicate the importance of power fluctuation identification as well as the benefits of the proposed strategy. The results clearly show a considerable improvement in response performance indices, as the maximum peak overshoot was decreased by 21.25% to 51.2%, and settling time was lowered by about 23.34% to 65.40% for the suggested control technique compared to other controllers.

Stability Analysis of Cyber Physical Microgrid with Dynamic Demand Control considering Time Delays

Time delays are enforced into the LFC system of microgrid (MG) while transmitting the control signals from the central controller and also aggregating the controllable loads of Demand Side Response (DSR). Due to these delays, the system dynamic performance gets affected leading to system instability. The time delays may be fixed or time varying. In this paper, a cyber physical microgrid is modeled with Dynamic Demand Control (DDC) loop including time delays, and the stability of the proposed model is analyzed both for fixed and time varying delays. The impact of fixed time delays on the stability of the proposed microgrid is theoretically evaluated using Frequency Sweeping Technique (FST). To examine the delay dependent stability of the proposed system with time varying delays, including external load perturbations, a matrix stability criterion is formulated and analyzed. The novelty of the method lies in the modelling of LFC with structured load perturbations and also investigating its impact on the stability of LFC using frequency domain approach. Since the effect of load perturbations is considered for the analysis, a more realistic operating condition can be portrayed in a microgrid system. The inclusion of DDC load in LFC of the microgrid provides better transient response even with larger time delays. The accuracy of the proposed method is verified through simulation results.

Robust Multi-Objective H2/H∞ Load Frequency Control of Multi-Area Interconnected Power Systems Using TS Fuzzy Modeling by Considering Delay and Uncertainty

The main objective of this paper is to design a robust multi-objective H2/H∞ delayed feedback controller for load frequency control of a multi-area interconnected power system by taking into account all theoretical and practical constraints. To achieve more precise modelling and analysis, the limitation of valve position, governor, and transmission delay are considered to guarantee of LFC system’s stability in practical applications. The nonlinear delayed system is approximated by the Takagi–Sugeno fuzzy model. Then, a parallel distributed compensation scheme is utilized for designing the control system of the overall system. The proposed multi-objective and robust H2/H∞ controller simultaneously minimizes the H2 and H∞ control performance indexes. Finally, simulation results verify the robustness and effectiveness of the proposed scheme in dealing with the impact of load disturbances, model uncertainties, transmission time delays, and nonlinearities in the model.

Load Frequency Robust Control Considering Intermittent Characteristics of Demand-Side Resources

Renewable energy has the characteristics of low carbon and environmental protection compared to traditional water and thermal power, but it also has the intermittency and uncertainty that traditional water and thermal power does not have. These characteristics make the inertia of the power system increase, which greatly affects the frequency stability of the grid. To solve such problems, the participation of demand-side resources (DSRs) in the dispatch of power systems has become a viable solution.However, unlike generation-side resources, DSRs have their own unique characteristics. In this paper, by taking into account a load frequency control system (LFC) with intermittent demand-side resources, the robust H∞ load frequency control problem are discussed in detail.A robust controller to coordinate the load side with the resource side is introduced. A critical stability criterion and robust performance evaluation of the new LFC system was carried out. Finally, simulation results based on the new LFC system are provided to demonstrate that the proposed control strategy can effectively improve the stability and robustness of the grid under large disturbances, thus allowing the grid frequency to return to the reference value.

Stability regions in time delayed two-area LFC system enhanced by EVs

Stability regions in time delayed two-area LFC system enhanced by EVs

Fuzzy logic-based integral controller for load frequency control in an isolated micro-grid with superconducting magnetic energy storage unit

In a Micro-Grid (MG), substantial-frequency fluctuations are caused by the sporadic nature of Renewable Energy Sources (RESs). Conventional Integral controllers are incapable of delivering adequate performance against the widely varied operating conditions. Hence, in this paper, the Fuzzy Logic-based Integral controller & Superconducting Magnetic Energy Storage (SMES) unit are incorporated in isolated MG to mitigate the frequency control issues. As a result of rapid changes in load and the discontinuous nature of RESs, frequency oscillations are produced, which are dampened by SMES units. The simulations are done in MATLAB / Simulink software. The results of the simulation reveal that the LFC system with a Fuzzy logic-based Integral controller and SMES unit has greater dynamic performance when compared to other LFC systems (with & without SMES unit using conventional Integral controller).

Detection of False Data Injection Attacks Based on Kalman Filter and Controller Design in Power System LFC

False data injection attacks pose a great threat to the safe and stable operation of power systems. Therefore, the detection and defense of false data injection attacks in LFC systems is becoming more and more important. First, based on the equivalent model of the LFC system and the Kalman filter algorithm, this paper proposes a false data injection attack detection method; secondly, a robust controller is used to reduce load disturbances according to the operating characteristics of the LFC system; then the idea of switching links is proposed to reduce the impact of cyberattack on the system; finally, MATLAB/Simulink software is used to carry out simulation tests. The test results verify the effectiveness of the false data injection attack detection method and switch link defense method proposed in this paper.

Stability Analysis of Load Frequency Control System with Constant Communication Delays

This paper deals with the stability analysis of network-controlled load frequency control system (LFC) in the presence of time-delays. Network-based control system requires transmitting measured data from the plant site to the controller and control signals from the controller to the plant site. Use of an open communication channel for transmitting data involves a delay in the control loop. Such a delay would affect the LFC system stability. Lyapunov-Krasovskii functional (LKF) analysis and linear matrix inequalities (LMIs) techniques are used to investigate the stability of LFC system with proportional-integral (PI) controller. A less conservative delay-dependent stability criterion is derived using a discrete delay N-decomposition approach to determine the delay margin for the LFC system. This investigation is done to find a relationship between the delay margin of the LFC system and gain of the PI controller. The effectiveness of the obtained results is verified using simulation studies.

Optical Design and Performance Analysis of Linear Focusing Solar Thermal Collectors

Linear Fresnel solar collector is a focusing concentrator suitable for direct steam generation, industrial process heat, and solar space cooling system and hot water generation for different uses. The optical design and performance simulations, experimental and numerical studies on linear Fresnel solar collector were reviewed. Studies on the optical designs and ray-tracing simulations results indicated non-uniform solar flux distributions on the receiver absorber surface. The optical quality of LFC is low due to its higher incidence angle and the cosine factor. Studies on optimizing the optical errors that affects the optical performance of the LFC are lacking in the literature. Ray tracing results at 0o incidence angle indicated three different optical losses-geometric configuration, material properties and focus errors losses. Studies on the lateral drift and uncertainty of the direction of the reflected rays, which adversely affect the concentration factor of the LFC are lacking in the literature. The optical performance of a LFC system can be improved through an optimized optical design - mirrors separation, shapes, width and their orientation.

Implementation of Fuzzy Logic Controller in Three Area Multi Source LFC System

The objective of this paper is to analyze power system with is interconnected with neighboring areas and having multisource power generation which is equipped with the fuzzy logic controller. Thermal, hydro and gas generating stations is used in each control area by considering real power environment. The proposed controller is tested with sudden step load disturbances. The dynamic response of LFC problem is studied by comparing with conventional controllers using MATLAB simulink software and found dynamic responses obtained satisfy the LFC requirement.

再生可能エネルギーを考慮した周波数解析用ダイナミック系統モデルの検討

This paper presents verification of capacity for generation control system of central load dispatching center. A dynamic power system model considering a central load dispatching center, load model, power system model and generator model for verification of generation control system is developed. The dynamic power system model is evaluation of validity and consider of optimal LFC system. The application scope of a dynamic power system model is verified.