Automatic Frequency Control System Research Articles

Rapid Switching of a C-Series Linear Accelerator Between Conventional and Ultrahigh-Dose-Rate Research Mode With Beamline Modifications and Output Stabilization

PurposeIn this study, a decommissioned C-series linear accelerator (linac) was configured to enable rapid and reliable conversion between the production of conventional electron beams and an Ultrahigh-dose-rate (UHDR) electron beamline to the treatment room isocenter for FLASH radiation therapy. Efforts to tune the beam resulted in a consistent, stable UHDR beamline. Methods and MaterialsThe linac was configured to allow for efficient switching between conventional and modified electron output modes within two minutes. Additions to the air system allow for retraction of the X-ray target from the beamline when the 10MV photon mode is selected. With the carousel set to an empty port, this grants access to the higher current pristine electron beam normally used to produce clinical photon fields. Monitoring signals related to the automatic frequency control (AFC) system allows for tuning of the waveguide while the machine is in a hold state so a stable beam is produced from the initial pulse. A pulse counting system implemented on a FPGA-based controller platform controls the delivery to a desired number of pulses. Beam profiles were measured with Gafchromic film. Pulse-by-pulse dosimetry was measured using a custom electrometer designed around the EdgeTM diode. ResultsThis method reliably produces a stable UHDR electron beam. Open field measurements of the 16cm (FWHM) gaussian beam saw average dose rates of 432Gy/s at treatment isocenter. Pulse overshoots were limited and ramp up was eliminated. Over the last year, there have been no recorded incidents that resulted in machine downtime due to the UHDR conversions. ConclusionStable 10MeV UHDR beams were generated to produce an average dose rate of 432Gy/s at the treatment room isocenter. With a reliable pulse-counting beam control system, consistent doses can be delivered for FLASH experiments with the ability to accommodate a wide range of field sizes, source-to-surface distances, and other experimental apparatus that may be relevant for future clinical translation.

An Automatic Frequency Control System for Transmission Machinery Based on Back-Propagation Neural Network Algorithm in the Internet of Things Environment

Abstract In order to reduce the error of automatic frequency control of transmission machinery under different disturbances, an automatic frequency control system of transmission machinery based on back-propagation (BP) neural network algorithm is designed. The gradient descent method and Newton method are combined to optimize the BP neural network. Aiming at the periodicity and trend of the actual mechanical vibration frequency time series, the first order backward difference is processed by the difference method, and the autoregressive sequence is derived to obtain the control model. The experimental results show that the system can realize the automatic control of transmission mechanical frequency with small error under different types of interference, and the control effect is ideal.

Load Frequency Control and Optimization of Load Allocation for Multi-Area Power System with Electric Vehicle Charging Load

The integration of electric vehicles (EVs) into power systems has introduced new challenges for load frequency control due to the additional charging load they impose. This research article investigates the design and analysis of automatic load frequency control in a two-area power system, considering the presence of EV charging load. The study employs Artificial Neural Network (ANN) based PI control to manage both traditional load demand and the dynamic charging requirements of EVs. Maintaining a stable power system frequency and balancing generation with the EV charging load have become crucial tasks. Automatic Generation Control (AGC) or Load Frequency Control (LFC) systems need to adapt and account for the variability and uncertainty associated with EV charging patterns. The integration of ANN-based PI control provides an intelligent and adaptive approach to address these challenges. Using MATLAB, a power system model is simulated to evaluate the effectiveness of the proposed control scheme. This investigation conducts a comparative analysis of the system's frequency responses under various scenarios, including different EV charging load profiles. It highlights the benefits and challenges of utilizing ANN-based PI control to manage the combined load of traditional demand and EV charging. Moreover, the load distribution among the distribution stations varied from 0.08% to 12.50% when compared between particle swarm optimization and genetic algorithm, respectively. By considering the dynamic interaction between power system operation and EV charging, this research aims to enhance the reliability, efficiency and sustainability of power systems in the context of evolving transportation trends and the increasing electrification of vehicles.

Enhancing of the power system resilience through the application of micro power systems (microgrid) with renewable distributed generation

The power sector plays a critical role in the functioning of the economy and the security of a country, being closely interconnected with other vital infrastructures, such as gas supply, water supply, transportation, and telecommunications. Ensuring a stable power supply is crucial for the uninterrupted operation of these systems. One way to enhance the resilience of the power system is by integrating local networks with distributed renewable generation into the overall energy infrastructure. The flexibility, stability, controllability, and self-healing capabilities of microgrids make them an effective solution for improving the resilience of the power system. The power grid is susceptible to disturbances and disruptions that can cause large-scale power outages for consumers. Statistical data indicates that approximately 90% of outages occur due to issues in the distribution system, thus research focuses on local microgrids with distributed renewable generation. This study analyzed the role of microgrids with renewable generation in enhancing the resilience of power systems. Additionally, functions of microgrids that contribute to enhancing power system resilience, such as service restoration, network formation strategies, control and stability, as well as preventive measures, were summarized. It was found that local microgrids have significant potential to enhance power system resilience through the implementation of various strategies, from emergency response planning to providing reliable energy supply for quick responses to military, environmental, and human-induced crises. The concept of local distributed energy generation, storage, and control can reduce reliance on long-distance power transmission lines, reduce network vulnerabilities, and simultaneously improve its resilience and reduce recovery time. It has been determined that the most necessary and promising approaches to enhance the resilience of the power system include developing appropriate regulatory frameworks, implementing automatic frequency and power control systems, ensuring resource adequacy (including the reservation of technical components), promoting distributed generation, integrating energy storage systems into the energy grid, and strengthening cyber security. Keywords: resilience, local power systems, MicroGrid, distributed generation, renewable energy sources.

Parameter measurement and optimization for a 3/6 dual-energy electron linear accelerator with industrial and inspection applications

Electron linear accelerator (LINAC) is a high-energy X-ray generator with extensive industrial, inspection, and medical applications. The studied LINAC uses a 2.6 MW magnetron as its RF generator derived with a Marx modulator. An electron gun of filament voltage 6 V and current 2.2 A connected to the accelerator tube is applied to establish electron current inside the drift tube. For this purpose, 9 kV and 25 kV voltages are applied to the cathode and anode of the electron gun pulse by pulse, generating dual-energy x-ray beams as outputs. An Automatic Frequency Control (AFC) system is designed for studied LINAC so that variation of output dose rate is lower than 2% and the required time to achieve the maximum output dose rate is lower than 1 s. Optimizing the Marx modulator's switching algorithm, the ripple in the output beam has been lower than 5%. The half-value layer (HVL) of steel has been measured for high and low energies equal to 6 MeV and 3 MeV, respectively. The output pulse of the electron beam and dose rate have been measured using a linear detector array (LDA) and dosimeter, respectively, with a pulse frequency of 35–400 Hz and pulse width of 2–4 μs.

Maiden Application of Fuzzy-2DOFTID Controller in Unified Voltage-Frequency Control of Power System

This article presents an amalgamated pattern of automatic load frequency control (ALFC) and automatic voltage regulator (AVR) system in a three-area interconnected power system using the Fuzzy two-degree-of-freedom tilt-integral-derivative controller (F2DOFTID). The multi-area system includes single-stage reheat thermal plants and Solar Thermal Power Plant (STPP) in Area-1 and Heavy-Duty Gas Turbines (HDGT) in Area-2 and Area-3. An incipient attempt is made to incorporate the HDGT plant in amalgamated control of the power system. Relevant generation rate constraints (GRC) and Governor Dead Band (GDB) are rendered for thermal plants. In both ALFC and AVR systems of all areas, a first attempt is made to implement an F2DOFTID controller to alleviate the frequency and voltage deviations. In this investigation, an algorithm named Harris Hawks Optimization (HHO) is efficaciously used to accomplish optimal controller parameters. Concerning all time-domain behaviors, F2DOFTID controller performance is superior relative to the TID and 2DOFTID controller. The AVR effect proclaims a substantial improvement in system dynamics. In this amalgamated scenario, the aftermath of the high voltage direct current (HVDC) tie-line and the usage of energy storage devices such as ultra-capacitors (UC) are found superlative in the amelioration of system performance. Similarly, by modifying the generator parameters and synchronizing coefficients, the robustness of the proposed controller is measured, which signifies that obtained controller parameters during nominal conditions are resilient enough and not to be altered. Eventually, the system is also studied in OPAL-RT OP 4510 RT Lab hardware set-up for real-time analysis.

Implementation of an Automatic Frequency and Power Control System at Pregol’skaya TPP

Implementation of an Automatic Frequency and Power Control System at Pregol’skaya TPP

Evaluation of the Impact of Doppler Effect on Quality of HSR Radiocommunications

The article proposes a methodology for evaluating radio signal distortions caused by Doppler effect (DE; also, Doppler shift) under the conditions of highspeed train traffic (HSR, high-speed rail). The objective of the work is to develop criteria for assessing quality of radiocommunications with moving objects in HSR environment. For this, a technique is proposed for calculating the probability of an error arising from Doppler effect. A rationale for relevance of the topic is that radiocommunications are used on railways for controlling train traffic and ensuring safety and achieving required quality of radio signals is a major challenge. Quality assessment is especially important for organization of broadband communication channels with locomotive drivers using mobile networks. To solve this problem, a model for assessing quality of radiocommunication influenced by DE is considered. Distortions of signals in a radio channel due to DE are proposed to be estimated using the reduced dispersion of the total error, which consists of two components: dynamic and interference. Calculations of the total reduced signal error and the error probability for speeds above 100 km/h are described. Estimates of the effect of DE on a coherent receiver, in which errors may occur due to changes in duration of radio pulses, are suggested. Effectiveness of the receiver’s automatic frequency control (AFC) system is analysed as a means of challenging DE. For this, the concept of an instantaneous spectrum of parasitic frequency modulation due to DE was introduced and quality of radio communication was calculated using the reduced dispersion of the total error. The efficiency of using AFC has been proven after comparing the evaluations of reception quality with and without AFC in the form of the ratio of error probabilities. The features of the use of mobile communications on railways under the conditions of DE are formulated.

Clock tuning technique for a disciplined high medium–long-stability GNSS oscillator with precise clock drifts for LEO users

A crucial issue of low earth orbit (LEO) navigation augmentation satellite constellation is to obtain a satellite clock of high medium–long stability (i.e., averaging time of 10–10,000 s) using a disciplined oscillator to reduce satellite size, weight, power consumption and cost, instead of using a large, heavy and expensive space atomic clock. To resolve this difficulty, we propose a new global navigation satellite system (GNSS) clock discipline technique via a stand-alone GNSS receiver. Consequently, high medium–long stability can be attained with the disciplined receiver oscillator. Based on the Doppler measurements calculated from carrier phases, precise clock drifts of the receiver oscillator are derived. According to the motion state of the LEO GNSS receiver, a precise clock drift estimation model is chosen to have good adaptability to the receiver's high dynamic movement. Then, the receiver oscillator is properly tuned to its nominal frequency at each epoch without loss of lock. An automatic closed-loop frequency control system using a third-order frequency-locked loop filter is proposed to periodically compensate the instantaneous frequency offsets of the user clock with respect to its nominal frequency. A nonlinear frequency steering method is proposed to overcome the receiver lost lock problem during the oscillator discipline process. The correctness and effectiveness of the proposed clock tuning technique were numerically verified with MATLAB first. Then, the oscillator discipline performances were tested with a VCH-1008 passive hydrogen maser, a LEO GNSS receiver and a PicoTime clock stability analyzer. With static real GPS data of a static receiver as well as with hardware simulated data of a LEO receiver, both the medium-term and long-term frequency stabilities of the disciplined oscillator were confirmed. Finally, the proposed oscillator discipline technique was implemented in a self-developed LEO GNSS receiver. A high-quality voltage-controlled crystal oscillator mounted on an onboard LEO receiver was used for our test both in a static situation and in a LEO dynamic environment. The experiment results show that the overlapping Allan deviation of the disciplined GNSS oscillator could be less than 7E-12 over periods of 1 to 4,000 s in both the static situation and the LEO moving situation for a 1070 km orbit with 1 Hz epoch sampling rate at the testing stage.

Експериментальне дослідження частотного дискримінатора з компенсації зміни рівня вхідного сигналу

Subject and Purpose. Answering the need for powerful high-frequency signal generation and desired radar range provision, pulsed magnetrons hold the current lead as part of radar transmitters. Yet there are some disadvantages, such as significant noise level and technological difficulties concerning the frequency tuning implementation. In this connection, a direct control of the pulsed magnetron frequency with the use of the Automatic Frequency Control (AFC) causes problems. And in the receiver, the AFC of the heterodyne rather than of the magnetron is more frequently used. The heterodyne frequency is maintained at such a level that the receiver is always tuned to the frequency of signal to receive. For various signal generation arrangements, the existing methods of frequency tuning with a frequency discriminator will be analyzed towards the following development of a principal electrical schematic diagram with gaining the operating characteristics of the frequency discriminator prototype on that diagram basis. Methods and methodology. The electrical schematic diagram is developed in terms of intuitive approach and analyzed by the mathematical modeling method. Results. The functional scheme of a frequency discriminator combining advantages of both single-cycle circuit (design simplicity and ease of tuning) and two-cycle circuit (null output voltage at a given frequency of the input signal and compensation possibilities as to the input voltage amplitude varying and interference) has been developed. The principal electrical schematic diagram of this new frequency discriminator has been reported together with the measured amplitude and frequency characteristics, dynamical figures, etc. Conclusions. The novelty of the proposed concept of a heterodyne AFC system built around a frequency discriminator has been confirmed. Its advantages over the known solutions have been shown.

The automatic frequency control based on artificial intelligence for compact particle accelerator.

In this work, an advantage actor critic (A2C) based intelligent automatic frequency control (AFC) system was developed for X-band linear accelerator (LINAC). A2C is one type of reinforcement learning, which indicates how software agents should perform actions in an environment. In this paper, the A2C based AFC algorithm and its environment design, simulation result, and controller hardware and software processes are described. The objective of our design is to match LINAC and magnetron frequency, and it is implemented via reward shaping using comparison with the reflected power in the adjacent time. The simulation with the A2C algorithm was implemented in two modes, namely, periodic and White Gaussian Noise (WGN) waves, for analysis with temperature and random disturbance, respectively. In order to create artificial disturbance in the experiment, the magnetron shaft was shifted randomly every 0.5 s by using WGN with 18° angle of the step motor. The standard deviation of the reflected power was 5.63 kW, and the average power was 130.9 kW. To obtain maximum reward at the beginning of the A2C training, the adjacent frequency is needed. The measured average reflected power and standard deviation were 122.8 kW and 1.75 kW, respectively, after 2000 iterations. The results show that the reflected power and standard deviation of the AFC with A2C were lower compared to open-loop with artificial disturbance. The RF station of a medical X-band LINAC was used as the test bench, and the performance was confirmed by the results of an experiment conducted at Sungkyunkwan University in Korea.

Система автоматической подстройки частоты импульсного магнетрона

Система автоматической подстройки частоты импульсного магнетрона

Анализ цифровых линейных систем автоподстройки частоты высокостабильного генератора по радиосигналу глобальной навигационной системы

Анализ цифровых линейных систем автоподстройки частоты высокостабильного генератора по радиосигналу глобальной навигационной системы

Coordinated performance of interline power flow controller and superconducting magnetic energy storage in combined ALFC and AVR system under deregulated environment

This study presents a two area combined Automatic Load Frequency Control (ALFC) and Automatic Voltage Regulator (AVR) system having reheat thermal and wind as Generating Companies (GENCOs) of area1 while reheat thermal and diesel as GENCOs of area2 in a deregulated environment. The thermal plant is considered with system nonlinearities. A proportional-integral and fractional order derivative having a filter controller is introduced for the combined ALFC-AVR system. A lightning search algorithm is employed for finding the best values of controller parameters. The comparative performance of the proposed controllers with some classical controllers proves the superiority of the proposed controller to others. The significance of the Interline Power Flow Controller (IPFC) and IPFC in combination with Superconducting Magnetic Energy Storage (SMES) in the considered system is investigated under bilateral transaction. The analysis reflects that addition of IPFC improves the dynamic responses. The combination of both IPFC and SMES enhances the system dynamics further. The sensitivity analysis against different Distribution Companies Participation Matrix and variation of the contact violation amount gives the robust performance of the introduced controller parameters.

Comparative Analysis of the Dynamic Properties of Variants of Automatic Frequency and Power Control Systems for Steam Power Plants Equipped with Once-Through Boilers

Considerably complicated power-system problems that have to be solved by the Russian power-generating units and, consequently, the need to ensure the fully automated operation of the power-generating units under working loads necessitated improving the structure of the automatic frequency and power control systems (AFPCSs). Not all solutions adopted in the 1980s, in particular, the use of the classical variants of the automatic power control systems (APCS-1 and APCS-2), ensure the required quality of suppressing power-system disturbances. In this work, the authors performed comparative analysis of six AFPCS variants that correspond to both the classical APCS-1 and APCS-2 and their combinations. The research was carried out using a mathematical model under disturbances of characteristic types, viz., those caused by network frequencies, unit power settings, and boiler loads. The model was developed by approximating experimental step response curves of the 300-MW power-generating unit 3 equipped with a once-through boiler at Kashirskaya State District Power Station. The quality of control was analyzed by comparing the amplitude-frequency characteristics and the curves of the transient processes of the compared AFPCS variants and the integral quadratic criterion values and the maximum deviations of the controlled variables and control actions in the course of the above processes. The combined AFPCS and advanced APCS-2 proved to be the most preferable. The combined AFPCS variants offer advantages in terms of maintaining the steam pressure, while the advanced APCS-2 has an advantage as a means for controlling the unit power with the gain in the first case being somewhat greater than that in the second case. Both variants have been successfully used for a long time at numerous power-generating units of the country.

Providing support for quality indicators when adjusting rotational speed of the diesel generator shaft

The subject of the study in the article is an analysis of ways and means to improve the accuracy of the rotation frequency, ensuring the stability and speed of the processes of speed control, increasing the reliability of the regulators that are used in automatic frequency control systems. The purpose is to describe the technical solutions proposed by the authors, the using of which will avoid the negative impact of changes in the physical properties of the working mixture used in regulators of indirect action . The task is justification of technical solutions, the introduction of which, in the practice of adjusting the rotational speed of the shaft of the diesel generator, will: increase the accuracy of the required values of the speed of rotation; ensure the necessary stability of the automatic frequency control system; to increase the speed of the regulatory processes; increase reliability of regulators; to eliminate the negative effect on the process of regulating the frequency of changes in the physical properties of working mixtures, are used in regulators of indirect action . Conclusion: the proposed technical solutions should be used both in the modernization of existing automatic speed control systems and in the construction of frequency control systems for new sources of electric energy.

Utilization of Nonthermal Plasma in Pulse Detonation Engine Ignition

Nonthermal plasma ignition using alternating-current-driven dielectric barrier discharge is applied to a pulse detonation engine. Five different geometrical in-house design plasma generators are tested to obtain more effective discharge performance. The selected plasma igniter, with 4.0 mm discharge gap between two electrodes with a dielectric barrier, can be powered by an alternating-current supply with output voltage and sinusoidal wave frequency. The required discharging waveforms, and hence ignition energy, can be obtained by the automatic frequency-control system, via which the operating frequency can be adjusted up to 500.0 Hz holding with almost unchanged breakdown voltages and currents in practical application. The respective mixture of hydrogen, acetylene, and ethylene was allocated with an excess air coefficient ranged from 0.6 to 1.4. The initial pressure of the mixture changed from 0.04 to 0.1 MPa and was tested in the single-trial experiments. The shortened deflagration-to-detonation transition and detonation waves show the effectiveness of nonthermal plasma-assisted ignition for wider excess air coefficients. The multicycle mode is also conducted to show the performance of 15.0 Hz collaborative operation using the plasma igniter in an airbreathing pulse detonation engine. The feasibility of the present alternating-current-driven dielectric barrier discharge technology to generate nonthermal plasma is thus verified for single-trial detonation tube and multicycle pulse detonation engine ignition in laboratory.

Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

KAERI is developing a 6MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25MHz, it gives 5MHz (∵±25MHz/10 turns → 50MHz/10 turns =5MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10kHz/step (=5MHz per turn/500 steps per turn). The developed system is a more compact new resonance frequency control system. In addition, a frequency measuring part is included and it can measure the real-time resonance frequency from the magnetron. We have succeeded in the stable provisioning of RF power by recording the results of a 0.01% frequency deviation in the AFC during an RF test. Accordingly, in this paper, the detailed design, fabrication, and a high power test of the AFC system for the X-band linac are presented.

Effect of Rabi splitting on the low-temperature electron paramagnetic resonance signal of anthracite

Specific distortions of the EPR signal of bulk anthracite are observed at low temperatures. They are accompanied by variations in the microwave oscillator frequency and are explained by the manifestation of the Rabi splitting due to the strong coupling between electron spins and the cavity, combined with the use of an automatic frequency-control (AFC) system. EPR signals are recorded at negligible saturation in the temperature range of 4–300K with use of the AFC system to keep the oscillator frequency locked to the resonant frequency of the TM110 cylinder cavity loaded with the sample. For the sample with a mass of 3.6mg the line distortions are observed below 50K and increase with temperature lowering. The oscillator frequency variations are used to estimate the coupling strength as well as the number of spins in the sample. It is shown that the spin-cavity coupling strength is inversely proportional to temperature and can be used for the absolute determination of the number of spins in a sample. Our results indicate that at low temperatures even 1016 spins of the anthracite sample, with a mass of about 0.5mg, can distort the EPR line.

Техніко-економічні аспекти використання споживачів-регуляторів у системах автоматичного регулювання частотою і потужністю

Техніко-економічні аспекти використання споживачів-регуляторів у системах автоматичного регулювання частотою і потужністю