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Clock distribution systems are used in many applications requiring accurate time basis: integrated circuits, computer networks, satellite communications, and Global Position System (GPS). Trying to automatize the design of clock distribution systems, this work presents a general formulation considering the possible topologies and parameters, building a computational tool allowing to design and evaluate the performance of any case to be studied. The developed tool enables to simulate networks setting the number of nodes, internal node parameters, topology, perturbations, and signal propagation delays. The simulation results include response times, synchronization quality, and stability for all types of arrangements: mutually connected, chains, rings, stars, and mixed architectures. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes an adaptive acceleration lock compensation technology for phase-locked loops (PLLs) based on a novel dual-mode programmable ring voltage-controlled oscillator (ring-VCO). In addition, a time-to-digital converter (TDC) is designed to accurately quantify the phase difference from the phase frequency detector (PFD) in order to optimize the dead-zone effect while dynamically switching an auxiliary charge pump (CP) module to realize fast phase locking. Furthermore, a TDC-controlled three/five-stage dual-mode adaptively continuously switched VCO is proposed to optimize the phase noise (PN) and power efficiency, leading to an optimal performance tradeoff of the PLL. Based on the 180 nm/1.8 V standard CMOS technology, the complete PLL design and a corresponding simulation analysis are implemented. The results show that, with a 1 GHz reference signal as the input, the output frequency is 50–324 MHz, with a wide tuning range of 260 MHz and a low phase noise of −98.07 dBc/Hz@1 MHz. The key phase-locking time is reduced to 1.11 μs, and the power dissipation is lowered to 1.86 mW with a layout area of 66 μm × 128 μm. A significantly remarkable multiobjective performance tradeoff with topology optimization is realized, which is in contrast to several similar design cases of PLLs. [ABSTRACT FROM AUTHOR]

With the evolution of modern power systems, inverter-based resources have become increasingly prevalent. As critical energy conversion interfaces, grid-following converters exhibit dynamic performances, presenting challenges for system security and stability. This paper focuses on the transient synchronization stability of converters after disturbances, highlighting differences in mechanisms compared to synchronous generators. Although previous studies on the transient synchronization stability of converters have been conducted, they primarily concentrate on the dynamics of the phase-locked loop, with limited consideration of the effects of outer-loop control. This has created a cognitive bottleneck in understanding the transient synchronization mechanisms of converters. To address these challenges, this paper models a grid-following voltage source converter system, incorporating detailed converter control strategies and current-limiting control. The stability regions of the stable equilibrium point under various fault severities are first analyzed. Then, the impacts of outer-loop control, including PI control and current-limiting control, on transient synchronization are examined. The study systematically elucidates the influence of outer-loop control on the transient synchronization stability of converters. Finally, the validity of the proposed theory is confirmed through simulations conducted in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

New energy power sources can be categorized into grid-following and grid-forming types based on their synchronization characteristics with the grid. Due to the different basic control operation principles of these two types of new energy power sources, they can lead to the instability of the grid-connected system through different paths. A mathematical model is established to describe the dynamic characteristics of the grid-following and the grid-forming new energy power resources, and the control block diagram of the nonlinear dynamic characteristic equation is compared and analyzed. The similarity between grid-following and grid-forming new energy power supply is revealed, and we preliminarily discuss the influencing factors of the stability of new energy sources. Using a single-machine infinite system model, the influence of key control parameters on transient stability is separately investigated for grid-following and grid-forming types. The influence of the converter synchronous loop control parameters on the system is verified, and the factors affecting the stability are discussed in combination with current limiting and frequency limiting. The research will provide reference for the design of a new energy power grid connection system. [ABSTRACT FROM AUTHOR]

A digital phase-locked loop (DPLL) based on sliding window infinite Fourier transform (SWIFT) and αSWIFT is proposed to extract the vibration and velocity parameters from the phase-modulated carrier signal. The phase of a carrier signal gets modulated when it is reflected from a vibration object due to the Doppler effect. Therefore, the phase-modulated carrier signal contains the Doppler signal that has the vibration information. The SWIFT or αSWIFT structure is designed from sliding discrete-time Fourier transform (DTFT) where the exponential window provides higher weightage to recent samples. It acts as a phase detector in the proposed DPLL, and its bandwidth can be varied based on the values of the time-constant. A controller unit, along with a bi-quad oscillator, is introduced in the proposed DPLL structure to remove any leakages in the system and to synchronize the system units in the parameter estimation. The proposed scheme is implemented in MATLAB/SIMULINK environment and validation for real-time applications is done using dSPACE 1202 MicrolabBox. [ABSTRACT FROM AUTHOR]

When a permanent magnet synchronous motor is dynamically controlled by a finite set model prediction, although the dynamic performance is excellent, there are problems of poor steady state performance and high computational effort. This paper develops a two vector based model predictive current control strategy depend on the Luenberger observer to solve the above mentioned problem. Firstly, a new voltage vector selection table is constructed by using the conventional duty cycle model to predict the variation law of the sector where the sub-optimal voltage vector for current control is located, and reduces the number of calculations of sub-optimal voltage vectors from six to two. In addition, Luenberger observer is designed to estimate the motor's counter-electromotive force, the phase-locked loop is used to precisely estimate the position and speed information of the rotor of the permanent magnet synchronous motor, effectively solving some of the drawbacks brought about by mechanical sensors. Finally, the experimental platform is set up and compared with the conventional limited set model predictive control. The experimental results show that the control strategy proposed has better steady state performance and control accuracy. [ABSTRACT FROM AUTHOR]

The growing focus on clean energy is driving the extensive usage of grid-connected inverters (GCIs) and nonlinear loads. The adoption of these nonlinear components causes disturbances, such as harmonic injection, frequency variation, and DC offset, which reduce the power quality of the grid. This reduced power quality induces unstable operation and deterioration of sensitive equipment. The organizations of electrical engineers have defined some standards such as IEEE 519 and P1547 to maintain the power quality of GCIs by setting the limits for harmonics, phases, and frequency variations. Harmonic elimination with grid synchronization methods is used for GCIs to meet the standards. However, the performance of these methods degrades for distorted grid conditions such as DC offset and harmonics. To rectify the mentioned issues, this study proposes a harmonic compensation method using a frequency-adaptive digital lock-in amplifier-based phase-locked loop (DLIA–PLL). The aim is to provide accurate harmonic detection and elimination by performing frequency and phase tracking for grid synchronization. Simulation and experimental results for a 5 kW inverter in an environment with high-total harmonic distortion (THD) conditions are presented to validate the performance of the proposed harmonic compensation with DLIA–PLL. Yokogawa WT1600, a power analyzer, is used to provide reference THD. [ABSTRACT FROM AUTHOR]

In commercial electrical equipment, the popular sensorless drive scheme for the interior permanent magnet synchronous motor, based on the quasi-sliding mode observer (QSMO) and phase-locked loop (PLL), still faces challenges such as position errors and limited applicability across a wide speed range. To address these problems, this paper analyzes the frequency domain model of the QSMO. A QSMO-based parameter adaptation method is proposed to adjust the boundary layer and widen the speed operating range, considering the QSMO bandwidth. A QSMO-based phase lag compensation method is proposed to mitigate steady-state position errors, considering the QSMO phase lag. Then, the PLL model is analyzed to select the estimated speed difference for transient position error compensation. Specifically, a transient position error compensator based on a feedback time delay neural network (FB-TDNN) is proposed. Based on the back propagation learning algorithm, the specific structure and optimal parameters of the FB-TDNN are determined during the offline training process. The proposed parameter adaptation method and two position error compensation methods were validated through simulations in simulated wide-speed operation scenarios, including sudden speed changes. Overall, the proposed scheme fully mitigates steady-state position errors, substantially mitigates transient position errors, and exhibits good stability across a wide speed range. [ABSTRACT FROM AUTHOR]

Existing transient stability analysis of grid-following (GFL) converters mainly focuses on the dynamics of the phase-locked loop (PLL), while current loop dynamics are usually neglected due to their faster response than PLL. However, this article reveals that active current may not be able to track its reference quickly during severe grid faults even with high current loop bandwidth, which leads to a non-negligible impact on the transient stability of GFL converters. Furthermore, this article discusses the intrinsic mechanism of why active current cannot track its reference quickly during severe grid faults and establishes a refined third-order transient synchronization model that offers a more accurate assessment of transient stability during severe grid faults than the conventional second-order model. [ABSTRACT FROM AUTHOR]

This article proposes two different structures of fractional‐order modified synchronous reference frame phase‐locked loop (MSRF PLL) and discusses their performance under different grid abnormalities. Phase‐locked loop (PLL) is a type of closed‐loop feedback control system that ensures phase and frequency coherence between its input and output signals. The basic synchronous reference frame phase‐locked loop (SRF‐PLL) is a conventional synchronization technique that is frequently employed in grid‐connected systems for power electronic converters. The SRF‐PLL offers rapid and precise phase/frequency detection under ideal grid environments. However, its performance is severely hampered under unbalanced and distorted grid environments. This paper discusses two new configurations of fractional‐order (FO) modified SRF (MSRF), one with fractional order only in additional low‐pass filter of first order (FO‐LP) and another fractional order in both first‐order low‐pass filter and PI (FO‐LPFO‐PI) of MSRF. These controllers are assembled using FOs “a” and “b” with limits as 0 < a < 2 and 0 < b < 2. The performance analysis of proposed FO MSRFs is done under grid abnormalities like voltage sag and swell, polluted grid supply, frequency change, phase change, and variables for dc offset. The outcomes of simulation are acquired using FO modeling and control (FOMCON) toolbox for MATLAB/SIMULINK, and the experimental results are validated with simulation results. A fair comparison among the MSRF‐PLL, FO‐LP MSRF‐PLL, and FO‐LPFO‐PI MSRF‐PLL is also depicted during grid abnormalities. [ABSTRACT FROM AUTHOR]

Summary: In this study, an improved anti‐windup proportional‐integral predictive direct power control strategy with a phase‐locked loop (PLL) is proposed and applied to a three‐level shunt active power filter (SAPF) neutral point clamped (NPC) inverter using space vector modulation (SVM) technique. The SAPF has to ensure sinusoidal waveforms and unity power factor in the grid side, by eliminating harmonic currents and compensating reactive power of the nonlinear loads. Active and reactive powers as well as the DC bus voltage controls are performed using anti‐windup proportional and integral actions with a predictive algorithm, without a need for an exhaustive mathematical model. The control law is modulated using the SVM technique allowing fixed switching frequency and low power ripples. The performances of the suggested control have been verified through an electronic STM32F407 card under diverse and severe conditions. The obtained results confirmed the expected objectives in terms of current and voltage quality, robustness, and dynamic response. [ABSTRACT FROM AUTHOR]

The article describes in detail the equipment and method for measuring the Doppler frequency shift (DFS) on an inclined radio path, based on the principle of the phase-locked loop using an SDR receiver for the investigation of seismogenic and man-made disturbances in the ionosphere. During the two M7.8 earthquakes in Nepal (25 April 2015) and Turkey (6 February 2023), a Doppler ionosonde detected co-seismic and pre-seismic effects in the ionosphere, the appearances of which are connected with the various propagation mechanisms of seismogenic disturbance from the lithosphere up to the ionosphere. One day before the earthquake in Nepal and 90 min prior to the main shock, an increase in the intensity of Doppler bursts was detected, which reflected the disturbance of the ionosphere. A channel of geophysical interaction in the system of lithosphere–atmosphere–ionosphere coupling was traced based on the comprehensive monitoring of the DFS of the ionospheric signal, as well as of the flux of gamma rays in subsoil layers of rocks and in the ground-level atmosphere. The concept of lithosphere–atmosphere–ionosphere coupling, where the key role is assigned to ionization of the atmospheric boundary layer, was confirmed by a retrospective analysis of the DFS records of an ionospheric signal made during underground nuclear explosions at the Semipalatinsk test site. A simple formula for reconstructing the velocity profile of the acoustic pulse from a Dopplerogram was obtained, which depends on only two parameters, one of which is the dimension of length and the other the dimension of time. The reconstructed profiles of the acoustic pulses from the two underground nuclear explosions, which reached the height of the reflection point of the sounding radio wave, are presented. [ABSTRACT FROM AUTHOR]

PLLs with small areas, low power consumption, and low jitter are crucial for mobile applications. Hence, achieving a balance between the area, power consumption, and noise of a PLL is a significant issue. In this work, a compact, low-power, and low-jitter fractional-N PLL using Ring-VCO is introduced. In order to reduce area and power consumption, a single-ended Ring-VCO is implemented. Additionally, novel resistance matrixes are proposed to decrease phase noise. The resistor matrix creates 13 frequency tuning curves with close VCO gain and different initial frequencies, reducing the VCO gain and thus the overall noise while maintaining high tuning linearity. The proposed PLL is fabricated based on 12 nm FinFET technology with a 0.078 mm2 area. It achieves a 2.702 ps RMS jitter at 5.76 GHz while consuming 6.4 mW. Moreover, it maintains a low power consumption and a low RMS jitter across the entire frequency range. [ABSTRACT FROM AUTHOR]

To build the new power system with the main body of new energy, the offshore wind farm (OWF) is an important part and has been rapidly developed in coastal cities. However, the large-scale OWFs also reduce the inertia of power systems, which significantly decreases the anti-disturbance capability of system frequency Therefore, a synthetic inertia control strategy for OWF based on dual phase-locked loops (PLL) was proposed. First, the influence mechanism of PLL on virtual inertia of wind turbine was theoretically analyzed for variable parameter PLL. And the variation rule of wind turbine inertia support capacity and system frequency response characteristics with parameter changing PLL was explored. Then, the double PLL based OWF frequency regulation strategy was proposed through analyzing the negative effect of primary frequency regulation characteristics caused by the variable parameter of PLL. Finally, the effectiveness of the proposed frequency regulation strategy was verified though simulations. The results show that the proposed method has significant advantages in frequency response speed and frequency measurement noise suppression.

A low-power clock and data recovery circuit with a quarter rate operating at 10 GHz is presented. This circuit consists of a phase lock loop and an input data retiming circuit. The phase-locked loop includes an LC oscillator, a quarter-rate detector, a charge pump, and a low-pass filter. The output of the oscillator is applied to a two-bit counter, so the clock frequency is reduced to 2.5 GHz with eight different phases which applied to the phase detector to sample the input data in different phases. Each sampling is done in 12.5 picoseconds. The innovative application of this two-bit counter eliminates the requirement of the multiphase oscillator, thus helps to reduce overall power dissipation. The power consumption of the voltage control oscillator is about 5.83 mW. In addition, reducing the clock frequency improves the performance of the phase detector circuit. The total power dissipation of the proposed CDR is evaluated to be 10.9 mW from a 1.8 V supply. [ABSTRACT FROM AUTHOR]

The key to realizing a high-performance frequency-modulated continuous wave (FMCW) laser frequency-sweeping light source is how to extend the frequency-swept bandwidth and eliminate the effect of nonlinearity. To solve these issues, this paper designs a broadband high-linear FMCW frequency-sweeping light source system based on the combination of fixed temperature control and digital optoelectronic phase-locked loop (PLL), which controls the temperatures of the two lasers separately and attempts to achieve the coarse spectral stitching based on a time-division multiplexing scheme. Furthermore, we uses the PLL to correct the frequency error more specifically after the coarse stitching, which achieves the spectrum fine stitching and, meanwhile, realizes the nonlinearity correction. The experimental results show that our scheme can successfully achieve bandwidth expansion and nonlinearity correction, and the sweeping bandwidth is twice as much as that of the original single laser. The full-width half-maximum (FWHM) of the FMCW output is reduced from 150 kHz to 6.1 kHz, which exhibits excellent nonlinear correction performance. The relative error of the FMCW ranging system based on this frequency-swept light source is also reduced from 1.628% to 0.673%. Therefore, our frequency-swept light source with excellent performance has a promising application in the FMCW laser ranging system. [ABSTRACT FROM AUTHOR]

Copyright of Power Generation Technology is the property of Power Generation Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this paper is to propose a novel technique for extracting the position signal from an inductive displacement transducer named a linear variable differential transformer (LVDT). In general, the movement of the LVDT core causes its primary inductance change in linear form. The primary winding of the LVDT is used as a time-dependent element for the triangular and square wave generator, which can be called self-oscillation, to generate frequency. The advantage of the proposed technique is that it can measure the displacement using the LVDT without an external oscillator. The change in primary inductance causes the frequency deviation generated by the oscillator. The deviated frequency is captured and converted into a voltage signal using the principle of the phase-locked loop. All the components used in this study are commercially available. The merits of this proposed technique are simple configuration, small size, and low cost. Moreover, the operating range of the LVDT can be extended without the limitation of the nonlinear transfer characteristic. The performance of the proposed technique is discussed in detail and confirmed by experimental implementation. Experimental results show that the maximum error from the proposed technique is about 0.42% and the operating range of the LVDT can be extended to more than 200%. It can be seen that the proposed technique is suitable for embedded measurement in small or micro robots. [ABSTRACT FROM AUTHOR]

This paper presents a wideband approach for L5 and S-band integer-N phase-locked loop (PLL) targeting Indian Regional Navigation Satellite System (IRNSS) applications. A reference spur reduction technique using a G m − C filter is proposed. The reference spur is improved by 7 dB when compared with one without any G m − C filter. The wideband integer-N PLL is designed and fabricated in UMC 65-nm CMOS process. The G m − C filter block consumes 200 μ A current. The wideband voltage-controlled oscillator (VCO) oscillates from 1.6 GHz to 3.2 GHz having a tuning range (TR) of 40 % , achieving a best and worst phase noise of ≈−122 dBc/Hz and ≈ − 116 dBc/Hz at a 1 MHz offset, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Electric Drive for Locomotives is the property of Electric Drive for Locomotives Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a single-step automatic tuning procedure and an estimator of key parameters of the drill-string system used in deep drilling applications. It is aimed at precise tuning of an external vibration suppression system based on speed control loop of the drilling electrical drive tuned for "stiff" motor-side speed control (the so-called speed source behavior), and the external drill-string torque feedback used for torsional vibration active damping. The automatic tuning procedure is carried out for the case when the drill-string and drill-bit are hoisted from the bottom of the well and the drilling electrical drive briefly enters the limit cycle oscillatory behavior under stiff speed control. The proposed auto-tuning system features a suitable control-oriented process model of the torsional oscillator and a modified-mixer phase detector phase locked-loop equipped with adaptive second-order generalized integrator (band-pass filter) for the extraction of key features of the drive resonance mode. The overall control system design relies on the so-called damping optimum criterion which guarantees a desired level of closed-loop system damping. The functionality of the proposed adaptive control system with automatic tuning of the control strategy has been systematically verified by means of comprehensive simulations, and the effectiveness of the drill-string parameter estimator has also been confirmed using the previously recorded field data to illustrate its robustness in the presence of realistic measurement noise. [ABSTRACT FROM AUTHOR]

Existing transient stability analysis of grid-following (GFL) converters mainly focuses on the dynamics of the phase-locked loop (PLL), while current loop dynamics are usually neglected due to their faster response than PLL. However, this article reveals that active current may not be able to track its reference quickly during severe grid faults even with high current loop bandwidth, which leads to a non-negligible impact on the transient stability of GFL converters. Furthermore, this article discusses the intrinsic mechanism of why active current cannot track its reference quickly during severe grid faults and establishes a refined third-order transient synchronization model that offers a more accurate assessment of transient stability during severe grid faults than the conventional second-order model.

The rapid increase of wind power penetration has threatened the frequency stability of regional power grids, and the loss of system inertia is viewed as the key issue to be solved. Catering to this problem, this paper proposes a rotational reference frame (RRF) control method for the doubly-fed induction generator based wind turbines (DFIG-WTs) to improve the inertia frequency response. An anti-frequency-deviation phase delay is introduced into the phase angle measured by the phase-locked loop (PLL). The dq-RRF of the control system of a DFIG-WT is rotated such that the voltage vectors of the stator and the grid-side converter (GSC) moved like the internal voltage vector of a synchronous generator. Frequency domain analysis is carried out to evaluate the stability of the system and the robustness to the variations of control parameters of the DFIG-WT. Both simulation studies and hardware-in-the-loop experiment are carried out for frequency and active power response. Results show that the RRF controller not only inherits stronger robustness and simpler structure, but also is able to provide stronger inertial support against the drop of system frequency than the widely used synthetic inertia control (SIC) method.

This paper deals with the phase noise affecting communication systems, where local oscillators are employed to obtain reference signals for carrier and timing synchronizations. The most common discrete-time phase noise channel model is analyzed, with the aim to fill the gap between measurements and analytical models. In particular, the power loss and the intersymbol interference due to the presence of phase noise is evaluated with reference to the measurements parameters and to the system bandwidth. Moreover, the impact on the communication systems’ performance of the phase noise originating from the oscillator non-idealities is considered, in case of free-running and phase-locked oscillators. The proposed analysis allows to extrapolate useful information about the performance of practical systems by investigating the power spectral density of the oscillator phase noise. An expression for the variance of the residual phase error after tracking, which depends on the main parameters of practical oscillators, is derived, and used to study the dependence of the performance on the symbol rate.

The single-phase three-leg unified power quality conditioner (UPQC) can achieve the functions of voltage compensation, reactive power compensation, and harmonic compensation. However, traditional control algorithms require a phase-locked loop to obtain the real-time phase angle of the grid voltage, which undoubtedly increases algorithm complexity. To simplify the phase-locked calculation, this paper proposes a control method without the phase-locked loop for the single-phase three-leg UPQC. In the proposed scheme, the instantaneous value of the grid voltage is employed to realize the grid integration control. Then, the load voltage reference is calculated in real time using a second-order generalized integrator. Moreover, a simple algorithm for reactive power and harmonic compensation is discussed, further simplifying the control algorithm. Finally, a small-scale experimental platform is built, and the effectiveness of the proposed method is verified by the experimental results. [ABSTRACT FROM AUTHOR]

In order to realize the generality of wind turbines hardware in the loop platform, a universal wind turbines hardware in the loop experiment platform is built to realize the optimal control of wind turbines. In view of the problem that direct drive wind turbines can affect the normal operation of direct drive wind turbines when the power grid voltage is unbalanced or asymmetrical, this study adopts the algorithm based on the decoupling of positive sequence current and negative sequence current to eliminate the negative sequence current and keep the constant output power. By inhibiting the double frequency fluctuation of the reactive power of the wind turbines when the fault occurs, the reference value of the active power and reactive power is 0, the amplitude of the double frequency fluctuation component of the grid reactive power is 0, and the purpose of eliminating the negative sequence current and making the output of the wind turbines stable is achieved. The simulation verification is carried out on the experimental platform. The experimental results show that the active power output of wind turbines remains unchanged and the grid-connection adaptability of wind turbines is significantly improved, which verifies the rationality and effectiveness of the method. [ABSTRACT FROM AUTHOR]

In recent years, several research works have addressed and developed the phase-locked loop (PLL) in single-phase grid-connected converters with different structures and properties. Each has merits and demerits, such as a complex structure, high computational burden, and slow transient response. This paper aims to comprehensively review advanced single-phase PLLs based on transport delay operators to realize signal orthogonality. A deep insight into the PLLs' small-signal modeling, main characteristics, stability analysis, and loop filter design are provided in this paper. The main advantages and drawbacks are explained for each type of PLL in terms of different performance indexes, such as settling time, estimation error, and ripples in the estimated grid information. This paper also aims to provide optimal tuning and design of the loop filter gains from the large-signal model point of view, including all the nonlinearities, adopting the stochastic optimization method. All simulations are implemented using the MATLAB/Simulink 2018b environment to validate all theoretical analyses of this paper. The sampling and nominal frequencies are set to be 100 kHz and 50 Hz throughout all the simulation studies. [ABSTRACT FROM AUTHOR]

In this study, a method for controlling the repetition frequency of a mid-infrared ultrashort pulse laser with a central wavelength of 2.8 µm is developed. A ring cavity that is insensitive to the polarization state of the laser light emitted from the fiber end was constructed to stabilize the oscillation of the mid-infrared ultrashort pulse laser. More oscillation conditions for the ultrashort pulse laser based on nonlinear polarization rotation are found than the conventional method. To confirm that the pulse oscillation is mode-locked, ultrashort pulse oscillation was confirmed by an autocorrelator. The pulse repetition frequency of this robust ultrashort pulse laser was controlled. The control method was based on the phase-locked loop (PLL) control. A wedge window was inserted into the cavity and mounted on a linear stage driven by a piezoelectric transducer. By driving the piezoelectric transducer, the position of the wedge window changed, and the resulting optical path length also changed. The repetition frequency was controlled based on this principle. Optical path length control by the wedge window and temperature control provides an Allan deviation of approximately 1 mHz. [ABSTRACT FROM AUTHOR]

Summary: The time delay unit‐based PLLs (TD‐PLLs) are widely used in grid synchronization in single‐phase power systems. However, the TD‐PLL is vulnerable to frequency variations and harmonic disturbances, leading to grid synchronization failures. Analysis shows that the performance degradation is due to the inability to obtain the variation of the input signal frequency. This paper proposes a new time delay‐based phase‐locked loop called immune to double frequency component TD‐PLL (IDFC‐TD‐PLL) based on a feedback structure to accurately capture the variation of input signal frequency, which can improve the dynamic performance and the performance against harmonic interference. Simulations and experiments have evaluated the performance of the proposed phase‐locked loop, demonstrating its superior accuracy and dynamic performance compared to the phase‐locked loops referred in the paper. [ABSTRACT FROM AUTHOR]

A low-power and low-jitter 1.2 GHz Integer-N PLL (INPLL) is designed in a 65 nm standard CMOS process. A novel high-gain sampling phase detector (PD), which takes advantage of a transconductance (Gm) cell to boost the gain, is developed to increase the phase detection gain by ~100× compared to the Phase-Frequency Detectors (PFDs) used in conventional PLLs. Using this high detection gain, the noise contribution of the PFD and Charge Pump (CP), reference clock, and dividers on the PLL output is minimized, enabling low output jitter at low power, even when using low-frequency reference clocks. To provide a sufficient frequency locking range, an auxiliary frequency-locked loop (AFLL) is embedded within the INPLL. An integrated Lock Detector (LD) helps detect the INPLL locked state and disables the AFLL to save on power consumption and minimize its impact on the INPLL jitter. The proposed INPLL layout measures 700 µm × 350 µm, consumes 350 µW, and exhibits an integrated phase noise (IPN) of −37 dBc (from 10 kHz to 10 MHz), equivalent to 2.9 ps rms jitter, while keeping the spur level 64 dBc lower, resulting in jitter figure of Merit ( F o M j i t t e r ) ~−236 dB. [ABSTRACT FROM AUTHOR]

A single-phase binary/quadrature phase-shift keying (BPSK/QPSK) demodulator basing on a phase-locked loop (PLL) is described. The demodulator relies on a linear characteristic a rising-edge RESET/SET flipflop (RSFF) employed as a phase detector. The phase controller takes the average output from the RSFF and performs a sub-ranging/re-scaling operation to provide an input signal to a voltage-controlled oscillator (VCO). The demodulator is truly modular which theoretically can be extended for a multiple-PSK (m-PSK) signal. Symbol-error rate analysis has also been extensively carried out. The proposed BPSK and QPSK demodulators have been fabricated in a 0.18 μm digital complementary metal–oxide– semiconductor (CMOS) process where they operate from a single supply of 1.8 V. At a carrier frequency of 60 MHz, the BPSK and QPSK demodulators achieved maximum symbol rates of 25 and 12.5 Msymb/s while consuming 0.68 and 0.79 mW, respectively. At these maximum symbol rates, the BPSK and QPSK demodulators deliver symbol-error rates less than 7.9×10-10 and 9.8×10-10, respectively where their corresponding energy per bit figures were at 27.2 and 31.7 pJ. [ABSTRACT FROM AUTHOR]

A single-phase/single-loop multiple-phase-shift-keying (m-PSK) demodulator is described. The demodulator relies on a linear range of an exclusive-OR (XOR) gate employed as a phase detector. The phase controller takes the average output from the XOR gate and performs a sub-ranging/re-scaling operation to provide an input signal to a voltage-controlled oscillator (VCO). The demodulator is truly modular which theoretically can be extended for an m-PSK signal. The proposed single-phase binary-/quadrature-PSK (BPSK/QPSK) demodulators have been implemented with low-cost discrete components. The core of the phase controller simply relies on number of stages of a full-wave rectifier and a linear amplifier built from well-known op-amp-based negative feedback circuits. The demodulator prototypes operate from a single supply of 5 V. At a carrier frequency of 100 kHz, both the BPSK and QPSK demodulators achieved the maximum symbol rate of 20 ksymbol/s respectively. At these symbol rates, the BPSK and QPSK demodulators deliver symbol-error rates less than 2×10-10 and 7×10-10. [ABSTRACT FROM AUTHOR]

With the expansion of grid-connected photovoltaic power generation, the problem of small-disturbance stability caused by the dynamic characteristics of its converter control system becomes increasingly prominent. Due to the small capacity of a single photovoltaic power generation unit, the grid-connected photovoltaic power generation system often contains a large number of photovoltaic power generation units. As a result, the model of the system is high-order. And the large numbel of photovolatic power generation units greatly increases the complexity of stability analysis. Therefore, in order to propose a relatively simple and effective stability discrimination method, a reduced-order model of small-disturbance stability analysis of grid-connected photovoltaic power generation system under DC voltage control timescale through the timescale decomposition method is established in this paper. Then the small-disturbance stability criterion of the system is deduced by applying the Routh-Hurwitz criterion on the basis of this model. From the criterion, the key factors affecting the small-disturbance stability of the system under DC voltage control timescale are analyzed. The main unfavorable affecting factors are heavy loading condition, condition of weak grid connection, improper setting of parameters of converter control systems. The correctness and effectiveness of the proposed stability criterion are verified by simulation examples. The results show that the stability criterion can effectively evaluate the small-disturbance stability of the grid-connected photovoltaic power generation system under DC voltage timescale. The evaluation method does not need to establish a complex high-order model of the system, which greatly simplifies the calculation and analysis process.

Synchronization units are vital for the stable operation of grid-tied converters in generation and transmission. There are two main synchronization units, i.e., phase-locked loop (PLL) and power synchronization controller (PSC), with the corresponding drawbacks in weak and strong grid respectively. Recently, the hybrid synchronization controller (HSC) is proposed in order to make up the deficiencies of PLL and PSC in weak and strong grid respectively. This paper deduces the detailed impedance characteristics of PSC and HSC and compares their cons and pros to show the stability mechanism of HSC. Moreover, two types of HSCs are also presented and compared in this article with slight difference in structure. It is found that the impedance of Type II based HSC has smaller amplitude and better phase margin than PSC around fundamental frequency, while Type I based HSC has larger amplitude and less phase margin than PSC. Type II based HSC can improve the stability and Type I based HSC can worsen the stability compared with PSC. Realtime experiments are carried out to verify this.

The article describes in detail the equipment and method for measuring the Doppler frequency shift (DFS) on an inclined radio path, based on the principle of the phase-locked loop using an SDR receiver for the investigation of seismogenic and man-made disturbances in the ionosphere. During the two M7.8 earthquakes in Nepal (25 April 2015) and Turkey (6 February 2023), a Doppler ionosonde detected co-seismic and pre-seismic effects in the ionosphere, the appearances of which are connected with the various propagation mechanisms of seismogenic disturbance from the lithosphere up to the ionosphere. One day before the earthquake in Nepal and 90 min prior to the main shock, an increase in the intensity of Doppler bursts was detected, which reflected the disturbance of the ionosphere. A channel of geophysical interaction in the system of lithosphere–atmosphere–ionosphere coupling was traced based on the comprehensive monitoring of the DFS of the ionospheric signal, as well as of the flux of gamma rays in subsoil layers of rocks and in the ground-level atmosphere. The concept of lithosphere–atmosphere–ionosphere coupling, where the key role is assigned to ionization of the atmospheric boundary layer, was confirmed by a retrospective analysis of the DFS records of an ionospheric signal made during underground nuclear explosions at the Semipalatinsk test site. A simple formula for reconstructing the velocity profile of the acoustic pulse from a Dopplerogram was obtained, which depends on only two parameters, one of which is the dimension of length and the other the dimension of time. The reconstructed profiles of the acoustic pulses from the two underground nuclear explosions, which reached the height of the reflection point of the sounding radio wave, are presented.