Frequency Control System Research Articles

Compensation Method Based on Phase Shift Between Pins of Crystal Resonator

This paper presents a new method to improve the long-term frequency stability of an oven-controlled crystal oscillator (OCXO) without an external reference source. The frequency drift of the crystal oscillator can be obtained in real time by measuring the phase shift between the pins of the crystal resonator. In this paper, according to an equivalent circuit of a crystal oscillator, a linear equivalent mathematical model based on the phase shift of the crystal resonator and the output frequency is established. The experiments were conducted to observe the relation between the phase shift and frequency drift of the OCXO. At the same time, a crystal oscillator self-calibration frequency control system is established to improve the frequency drift of the OCXO. The results show that this method can effectively improve the drift of OCXOs. The OCXO drift rate was significantly improved from 1.53 10−10/day to 9.8 10−12/day, and after three days, it settled at 5.24 10−11. The long-term frequency stability also underwent remarkable improvement, from 1.16 10−11/1000 and 3.24 10−11/10,000 to 3.47 10−12/1000 and 1.05 10−11/10,000.

Power system frequency control: instantaneous discrete testing for numerical relay using wavelet transform

Power system frequency control: instantaneous discrete testing for numerical relay using wavelet transform

Optimized PID controller and model order reduction of reheated turbine for load frequency control using teaching learning-based optimization

Load frequency control (LFC) systems in power grids face challenges in maintaining stability while managing computational complexity. This research presents an optimized approach combining model order reduction techniques with Teaching Learning-Based Optimization (TLBO) for PID controller tuning in single-area LFC systems. Three reduction methods—Routh Approximation, Balanced Truncation, and Hankel Norm Approximation—were implemented to reduce system order from 4th to 2nd order, achieving a 47.3% reduction in computational time. The TLBO-optimized PID controller was compared with conventional tuning methods (Ziegler-Nichols, AMIGO, S-IMC, and CHR), demonstrating superior performance with a 38.2% decrease in settling time and 42.7% reduction in peak overshoot. The Routh Approximation method exhibited optimal performance with minimum settling time (2.8s) and peak overshoot (8.4%). Sensitivity analysis revealed stable system behavior with phase margin maintained at 84.25 degrees across parameter variations. The proposed approach achieved a 56.8% reduction in Integral Square Error compared to conventional methods, establishing its effectiveness for modern power grid applications. This research provides a robust framework for implementing efficient load frequency control in power systems while maintaining system stability and performance.

Optimal sizing model of battery energy storage in a droop-controlled islanded multi-carrier microgrid based on an advanced frequency droop model

This paper introduces an optimal sizing approach for battery energy storage systems (BESS) that integrates frequency regulation via an advanced frequency droop model (AFDM). In addition, based on the AFDM, a new formulation for charging/discharging of the battery with the purpose of system frequency control is presented. The studied MG system that consists of PV units, a diesel generator (DG), a combined heat and power (CHP) unit, a gas boiler, and a BESS is designed to meet the consumers’ thermal and electrical load requirements as well as system frequency regulation. In the proposed optimization model, the net present value of expansion planning costs (EPC) over the project lifetime should be minimized according to the capacity of installed BESS. The EPC consist of four components including, (i) MG operation cost pertaining to the DG, CHP units and gas boilers, (ii) value of lost load, (iii) BESS investment cost, and (iv) replacement cost of BESS, recognizing its shorter lifetime relative to the project’s lifespan. The effectiveness of the proposed method and its advantages compared other methods are demonstrated via a case study simulation. Compared to the conventional frequency droop characteristic, the utilized AFDM can reduce the total EPC while a broader range of power/frequency control capabilities of the BESS is achieved to regulate the frequency in a desired band. Furthermore, the paper examines the impact of the AFDM on the selection of battery technology.

Developing an advanced safety device for bridge-type cranes

Introduction. Experimentally revealed disadvantages of domestic complex safety devices in the part of load capacity limitation and parameters registration are described. The reasons why it is inadmissible to re-equip cranes under the control of foreign safety systems to the existing domestic devices are explained. It is suggested to achieve the safety of such cranes through the development of safety devices that take into account the dynamic characteristics of a particular crane and control algorithms of its drives.Materials and methods. The study was done using the developed safety device realizing the functions of load capacity limitation, automatic determination of the parameters of the load capacity limiter algorithm, determination of the crane operation intensity. The description of these algorithms in relation to cranes equipped with frequency control system is given. Experimental determination of operational parameters of the device is carried out on an overhead crane equipped with the ControlPro safety system (KoneCranes).Results. The use of the device allowed to decrease the dynamic coefficient in the whole range of lifted loads masses. A twofold reduction of the dynamic component was obtained when lifting near-nominal loads. The accuracy of characteristic number determination was 1.3%.Discussion and conclusion. It is demonstrated that the developed algorithm of load capacity limitation allowed not only to increase crane security, but also to reduce the loading on the crane, in comparison with the standard safety system. The accuracy of operating parameters determination in conditions of real technological process satisfies the requirements of normative documentation. Thus, the possibility of duplicating or replacing some functions of the standard safety system by using the developed device is shown.

Stability Analysis of Load Frequency Control Systems With Electric Vehicle Considering Time-Varying Delay

Stability Analysis of Load Frequency Control Systems With Electric Vehicle Considering Time-Varying Delay

Optimizing Adaptive Particle Swarm for Combined Fire and Storage Control FM Energy Reserve

The combination of thermal power units’ stability and energy storage systems’ rapid response time enhances power system frequency control. However, high costs and battery life impacts from charging/discharging strategies limit energy storage adoption. This study proposes an adaptive weight-based particle swarm optimization algorithm (APSO) to optimize energy storage control for joint thermal-storage frequency modulation (FM). By analyzing the coupling between state of charge (SOC) and charging/discharging power, the study implements “shallow charging and discharging” with dynamic SOC constraints. The improved PSO algorithm integrates adaptive weighting to overcome local optimal convergence, enhancing global search capabilities and particle migration. Simulation results, based on real-world power plant data, show improved FM accuracy, faster regulation, and reduced energy storage system loss, significantly boosting economic efficiency.

Delay margin computation for single area load frequency control system with time delay

In this paper, the delay margin is computed for a load frequency control system with time delay of a single area using delay-independent stability analysis method. The delay-independent stability analysis method is used to consider some characteristics. The delay-independent stability of time-delayed systems may lose stability if their eigenvalue spectrum lies on the imaginary axis for delays. The stability is guaranteed for the delay margin, which must be known. A method for computing the delay margin for load frequency control system with delay is presented. In this method, the system's characteristic equation is converted into frequency-dependent equation. Then the spectral radius of the matrix pair is used to compute the crossing frequency at which eigenvalues cross the imaginary axis. The crossing frequencies and angles are computed using sweeping tests and binary recursive algorithm. At the end, the effectiveness of the proposed method is demonstrated using a case study of load frequency control system with delay of a single area.

A novel tuning formula for PID/PIDD2 controllers for higher-order process plants

The industrial process control systems are high-order sophisticated and complicated systems with characteristics such as inertia, uncertainty, and even oscillatory. The controller design issue has long been challenging for the industry process control systems. This study proposes a novel tuning formula for PID/PIDD2 controllers for high-order process plants. Specifically, for the underdamped second-order with time delays (SOPDT) process plant, a formula for the tuning of PID/PIDD2 controller is proposed based on the relative damping coefficient x; for the critical and over-damped SOPDT process plants, the idea of using zero-pole cancellation is skillfully applied. The tuning parameters are determined by considering both robustness and integrated time absolute error (ITAE). The proposed tuning formula applies to the automatic voltage regulator (AVR) system and extends to the load frequency control (LFC) system and a practical double-capacity water tank experiment. Simulation results demonstrate that the proposed tuning method shows better robustness and anti-interference.

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.

Optimization of Frequency Stability in Hydraulic Load Frequency Control Systems Using Controllers with Filters

This study meticulously investigates the design and analysis of a Load Frequency Control (LFC) system tailored explicitly for hydraulic power systems by employing diverse configurations of PID controllers, namely Proportional (P), Proportional-Integral (PI), Proportional-Derivative (PD), Proportional-Integral-Derivative (PID), Proportional-Derivative-Fractional (PDF), and Proportional-Integral-Derivative-Fractional (PIDF). The primary objective of this exploration is to improve frequency stability in response to various load fluctuations typical in hydraulic systems. A comprehensive evaluation of each controller's performance is conducted through extensive MATLAB simulations, focusing on critical performance metrics such as rise time, peak time, steady-state time, and maximum overshoot. The findings reveal that the PD and PDF controllers exhibit superior response characteristics, offering the fastest and most stable outcomes regardless of whether droop characteristics are utilized or filtering techniques are introduced. Although the implementation of filters significantly mitigates overshoot, it is evident that controllers incorporating droop characteristics tend to compromise optimal steady-state time stability. The overall analysis underscores the PD and PDF controllers as the preeminent solutions for ensuring frequency stability in hydraulic LFC systems, especially under abrupt and substantial load changes, thus positioning them as vital tools in enhancing hydraulic power system reliability and efficiency.

An Optimal Load Frequency Control in a Two-Area Power System Using a Fractional Order Proportional- Integral-Derivative-Based Zebra Optimization Algorithm

Load frequency control systems are crucial for maintaining the stability and reliability of power grids. They help ensure that the power supply matches the demand, preventing fluctuations in grid frequency. However, Load frequency control systems have inherent limitations, such as the potential for instability and oscillation if not properly controlled. In this work, A fractional order proportional integral derivative controller is proposed to address this issue, which exhibits strong capabilities in managing parameter uncertainties, rejecting disturbances, and handling non-linear systems controllers. The novel approach in this search is the application of the zebra optimization algorithm to fine-tune controller parameters, a technique not previously used in load frequency control systems. In this Study the two-area power system with a reheat turbine is used a test case for fractional order proportional integral derivative controller, and the system is simulated using MATLAB/SIMULINK. The objective function integral time of square error is used that acts as a bridge of communication between the system's behavior and the control strategy. The performance of this controller is evaluated under disturbance 0.04. The results of the analysis demonstrated that the fractional order proportional integral derivative based zebra optimization algorithm controller outperformed the traditional fractional order proportional integral derivative controller in terms of three essential criteria: overshoot, settling time, and steady-state error. This research contributes to the advancement of load frequency control systems, ensuring reliable and stable power system operation.

Impact of Advanced Thyristor Controlled Series Capacitor on Load Frequency Control and Automatic Voltage Regulator Dual Area System with Interval Type-2 Fuzzy Sets-PID Usage

A major priority for practicing engineers in an electric power system is preserving the stability of frequency and voltage levels. Any change in these two factors will impact the efficiency and lifespan of the machines connected to the power supply. Therefore, this paper provides a control approach utilizing the Interval Type-2 Fuzzy Sets- Proportional Integral Derivative (IT2FSs-PID) controller and Advanced Thyristor Controlled Series Capacitor (ATCSC) with a combined Load Frequency Control-Automatic Voltage Regulator (LFC-AVR). Several inspections were implemented to demonstrate the controller’s strength, including various disturbances in the power system. The LFC-AVR was studied using two different dynamic models, referred to as open and closed loops on the Generation Rate Constraint (GRC) forms. A comparison was made using different techniques from the literature using the same model. Before using the approach, the frequency deviation of area-1 had a very large settling time value, which was caused by system instability. However, after implementing the approach, this value decreased to 4.9236 s. Finally, an additional ATCSC was added to the proposed model to observe its effect on the power system. The simulation was implemented using MATLAB/SIMULINK tools.

Load frequency and virtual inertia control for power system using fuzzy self-tuned PID controller with high penetration of renewable energy

Reliance on renewable energy is increasing, and generating units are being added to the network. Since renewable power fluctuates greatly, the frequency deviation of the grid becomes a crucial problem with access to renewable power generation. The fluctuation of the renewable power output of the system puts forward a higher demand for load frequency control of the power grid to increase the penetration of renewable power in the system. PID controller has proven its effectiveness for the LFC due to its simple structure and clear concept. In this article, the virtual synchronous generator is introduced and a fuzzy self-tuned PID controller is proposed for inertia control. The proposed controller is implemented in light of the significant integration of renewable energy and virtual inertia. The efficacy of the suggested controller is evaluated against the traditional PID controller for the Egyptian Power System as a case study under various load disturbance scenarios. The control technique is employed for variable loads with photovoltaic and wind turbine generation systems. Three instances of load changes are studied and the controller design is performed based on grey wolf optimizer in each case. The overshot and integral time absolute error are considered as comparison measures. The new contribution is applied to the proposed controller for the grid and virtual inertia. In the case of many load variations imposed, the disturbances of residential and industrial loads varied from 0.05, 0.01, 0.15, and 0.02 pu. The maximum overshoot is 0.005 for the proposed controller and 0.0078 for the classic PID controller. The integral time absolute error is 0.06429 for the proposed controller and 0.11481 for the classic PID controller. The results demonstrate the efficacy of the proposed controller for inertia control with high penetration of renewable energy. The results show that the proposed fuzzy self-tuned PID controller has an overshot less than the classical PID controller by 25% and integral time absolute error by 45%. These results show that the use of the proposed fuzzy self-tune controller for the grid and inertia gave a better performance in terms of the overshot value and the integral time absolute error.

Delay-dependent stability criteria for LFC systems with electric vehicles: A delay-interval-based piecewise Lyapunov functional approach

This paper studies the delay-dependent stability problem of single-area load frequency control (LFC) systems with electric vehicles. A novel Lyapunov–Krasovskii functional (LKF), called the delay-interval-based piecewise Lyapunov functional, is introduced. This innovative LKF approach allows for the construction of distinct LKFs within specific delay intervals, relaxing the requirement that a single LKF must exist for the entire delay interval. By incorporating the zero equation method, less conservatism delay-dependent stability criteria for LFC systems are obtained. Simulations are performed to illustrate the effectiveness and superiority of the presented methods.

Optimal and Robust Load Frequency Control for Hybrid Power System Integrated with Energy Storage Device by Sine Cosine Algorithm

Optimal and Robust Load Frequency Control for Hybrid Power System Integrated with Energy Storage Device by Sine Cosine Algorithm

Robust fractional-order load frequency control for hybrid power system concerning high wind penetration

Hybrid power systems concerning wind farms have witnessed significant dynamic characteristic changes due to unpredicted generation output and integration mode conversion between frequency-sensitive wind plants and non-scheduled ones. This work presents a robust fractional-order load frequency control (LFC) method for a multi-area hybrid power system in the presence of wind penetration uncertainties. To characterize the injection effect of wind farms, the power system is described by a model with an uncertain wind penetration factor in a pre-estimated range. Then, an enhancement of Levy’s identification method is developed to convert this model into a fractional-order reduced structure to design the load frequency controller, which is in a form of fractional-order PID with a filter for ease of engineering implementation. The closed-loop stability is analyzed by the stability boundary locus (SBL) method under different wind penetration levels. It is shown that superior frequency response performance and system robustness can be obtained if the controller is designed in terms of the model with the worse-case wind penetration. Illustrative examples including a three-area hybrid power system under a variety of wind penetration variations are given to show the effectiveness of the proposed method.

Developmental Trajectories of Electric Vehicle Research in a Circular Economy: Main Path Analysis

This study explored the development history and future trends of academic research on electric vehicles (EVs) in a circular economy. We collected 4127 articles on circular economy and EVs from the Web of Science database, and main path analysis indicated that academic research in the field of EVs in a circular economy has covered the following topics in chronological order: EVs as a power resource; vehicle-to-grid (V2G) technology; renewable energy and energy storage grids; smart grid and charging station optimization; and sustainable development of energy, water, and environmental systems. Through cluster analysis and data mining, we identified the following main research topics in the aforementioned field: recycling and reuse of EV batteries, charging stations and energy management, V2G systems and renewable energy, power frequency control systems, dynamic economic emissions, and energy management. Finally, data mining and statistical analysis revealed the following emerging research topics in this field from 2020 to 2023: microgrids, deep learning, loop supply chain, blockchain, and automatic generation control. Various achievements have been attained in research on EVs in a circular economy; however, challenges related to aspects such as sustainable battery recycling charging infrastructure and renewable energy integration remain.

Aggregator control of battery energy storage in wind power stations to maximize availability of regulation service

Battery energy storage systems can produce very fast bi-directional power flows, which makes them suitable for providing wind power regulation and frequency control services. Though battery systems can provide fast regulation services, their energy storage capacities are quite low in comparison to other generation sources, so regulation responses from them should be optimized to maximize availability of service. This paper proposes an aggregator that optimizes frequency control responses from battery energy storage systems to maximize service availability. The frequency control response from the aggregated system is defined by a single frequency-droop characteristic. This provides the predictability of response required to comply with grid codes and allows the aggregated system to participate in frequency control markets as a single entity. The method of implementation is fail-safe as failure to receive an optimized order from the aggregator does not prevent the battery energy storage systems from responding to frequency events. This mitigates stability concerns relating to communication delays between the aggregator and battery energy storage systems. Battery systems that provide multiple functions, such as frequency control system services and wind power regulation, can participate in the aggregator scheme by assigning a proportion of the battery’s capacity to the aggregator scheme. Simulations performed in DIgSILENT PowerFactory show that the aggregator successfully extends the duration of full regulation service from the battery systems during frequency excursion events.

Перемодуляция в трехфазных электронно-ключевых мостах системы преобразователь–электродвигатель

To ensure the operability of a circuit with three-phase pulse width modulation, it is necessary to meet the conditions of operability. One of the most important conditions is to exclude the phenomenon of overmodulation. To obtain the boundary values of the variables that determine the quality of modulation, it is necessary to study the phenomenon of overmodulation in various modes of operation of a three-phase converter. New modulating functions with constraints have been introduced to analyze the phenomena associated with overmodulation. Methods of analysis of electrical circuits have been used. The processes of three-phase pulse width modulation in the overmodulation mode have been studied. An assessment of the effect of overmodulation on the variables that determine the quality of the modulation process has been made. The boundary amplitude coefficient of a three-phase bridge has been determined, at which a three-phase overmodulation mode occurs. The results can be used to develop algorithms for controlling frequency converters in frequency control systems of electric drives.