Frequency Stability Research Articles

Frequency stabilization in microgrid with PV system based on maximum power extraction: A sliding mode approach

The article addresses the critical issue of frequency regulation in microgrids (MG) integrated with solar photovoltaic (PV) systems, which rely on maximum power point tracking (MPPT) using sliding mode control (SMC). The frequency stability of MGs is a significant concern due to the inherent variability of renewable energy sources, making frequency regulation challenging. This research proposes a dual-objective control strategy. Firstly, it ensures the solar PV system maximizes power extraction via a buck-boost converter controlled by SMC. Simultaneously, it maintains frequency regulation in the MG under load disturbances using SMC. The SMC technique guarantees precise convergence to the maximum power operating point and minimizes frequency deviations in the MG. The proposed solution demonstrates effective maximum power extraction under varying irradiance levels and reliable frequency regulation despite system parameter uncertainties and nonlinearities such as generation rate constraints (GRC) and governor deadband (GDB). Additionally, the SMC-based design achieves faster convergence compared to traditional proportional-integral (PI) controllers optimized using intelligent techniques. Stability analysis, performed using Bode and Nyquist plots, further confirms the robustness of the proposed system. The model was developed and tested in the MATLAB Simulink environment, showcasing its efficacy and reliability.

A SSA-based CFFOPID drop deloaded tidal turbine controller using HVDC-link

In contemporary scenario, electric power companies have observed upsurge in penetration level of tidal power plants (TPPs) in the traditional electric power system framework. However, the tidal turbines offer less frequency assistance due to their lesser rotor mass. Hence, TPPs may be collaborated with conventional units like diesel engine generator (DEG) to confirm system frequency stability in multi-area micro-grid system. The DEG comprises of primary and proportional integral derivative (PID) secondary frequency controls. However, in TPPs, to advance the system frequency regulation, deloading control approach is suggested and a cascade fuzzy fractional order PID-ID with derivative filter (CFFOPID-IDF) droop controller is suggested in place of the conventional non-cascade controller droop in the deloaded region. The suggested controller gains are fetched exploiting Salps swarm algorithm. For further enhancement of the dynamic responses, a precise high voltage direct current (AHVDC) link with the inertia emulation-based control (INEC) scheme is adopted, which allows the utilization of the gathered energy from the capacitance of the HVDC interface for frequency regulation. It provides better results compared to conventional AC tie line interface having less undershoot (34 %/20.63 %/43.75 %) and settling time (20.45 %/59.09 %/16.83 %) for variation in area-1 frequency/area-2 frequency/tie line power, respectively. The recommended control scheme is evidenced superior over numerous existing control techniques and provides least cost function in contrast to other control techniques. Additionally, it offers a highly stable performance under variable load conditions.

Superimposed Positive Sequence Impedance for Detecting Unintentional Islanding in Microgrid

Incorporation of environmentally friendly energy sources (RESs) into the electricity grid has many benefits, including economic, technological, and environmental. However, excessive renewable energy sources (RES) in the power grid provide technical problems, including equipment protection, DG operation, and islanding detection. One of the most serious challenges is the islanding phenomenon. Islanding can cause several problems, such as frequency instability and voltage fluctuations resulting in damage to electrical equipment or threatening utility workers who may be working/accessing the equipment. This research proposes an efficient islanding detection algorithm to lessen the impact of such threats. This novel passive islanding detection scheme is based on superimposed positive sequence impedance (SPSI). For calculating the superimposed positive sequence impedance (SPSI), the voltage and current signals are obtained from targeted DG points. The scheme’s performance is tested on multiple bus systems across islanding and non-islanding conditions using a MATLAB/Simulink environment. It is shown that even in the presence of noise, the algorithm can determine an islanding decision with high accuracy and a short detection time of 84 ms. In comparison to other algorithms, it operates at zero power mismatch (ZPM) and does not affect power quality.

Frequency stabilization of C-band semiconductor lasers through a SiN photonic integrated circuit

Integrated semiconductor lasers represent essential building blocks for integrated optical components and circuits and their stability in frequency is fundamental for the development of numerous frontier applications and engineering tasks. When dense optical circuits are considered, the stability of integrated laser sources can be impaired by the thermal cross-talk generated by the action of neighboring components, leading to a deterioration of the long-term system performance (on the scale of seconds). In this work we show the design and the experimental characterization of a silicon nitride photonic integrated circuit (PIC) that is able to frequency stabilize 16 semiconductor lasers, simultaneously. A stabilized 50 GHz-spaced two-channel system is demonstrated through the detection of the related beating note and the stability of the resulting waveform is characterized via the use of artificially induced thermal cross-talk stimuli.

A rheological model analog for assessing the resilience of socio-technical systems across sectors

A rheological model is proposed that captures the performance loss and properties of a potential subsequent recovery of socio-technical systems subject to arbitrary disruptions. The model facilitates the quantitative assessment of such systems’ resilience. While most models known from the literature describe systems that fully recover from aforementioned load events, the proposed model can capture also permanent performance loss or post disruption improvement. To demonstrate the versatility of the approach for a wide range of the socio-technical system spectrum, the model is applied to three systems: the frequency stability of the continental Europe power grid, flight operations of German airports, and the revenue of the German gastronomic sector. Fitting the proposed two-spring, one-damper, single-degree-of-freedom model to the recorded performance data determines relevant parameters which serve as a quantitative measure of the respective system’s resilience. The small set of model parameters can be associated with relevant resilience dimensions. Variation of these parameters allows to quantitively determine the change of the model’s response to the load events, and thus of the resilience predicted by the model. This allows to identify parameter ranges in which the model predicts, e.g., full recovery of a system, instead of permanent performance loss.

Cyber‐attack and defense method for load frequency control in smart grid systems with electric vehicles

AbstractThe latest advancements in Vehicle‐to‐Grid (V2G) technology enable Electric Vehicles (EVs) to contribute to Frequency Regulation (FR), mitigating the impact of uncertain power fluctuations in renewable resources. However, diverse cyber‐attacks pose threats to the Load Frequency Control (LFC) system and smart grid infrastructure, compromising their accuracy and reliability. This research paper focuses on the effects of cyber‐attacks on frequency regulation in a smart grid system that relies on a communication network. The study proposes a two‐area system and a modified IEEE‐39 bus three‐area system, incorporating intermittent solar photovoltaic and wind turbine sources, traditional conventional sources, and electric vehicles. To ensure frequency stabilization and tie‐line power, the researchers introduce a cascade FOPIDN‐(1+TD) controller. Its parameters are optimized using a novel Quasi Opposition Arithmetic Optimization Algorithm (QOAOA). The proposed approach's dynamic response is compared with other commonly used controllers, demonstrating its effectiveness in maintaining stability. The article focuses on the LFC system and presents a novel approach involving a cyber‐physical model. It introduces a method for detecting and defending against cyber‐attacks using deep learning, specifically utilizing the Long‐Short‐Term‐Memory (LSTM) network. The effectiveness of the proposed defense strategy is demonstrated through experiments conducted on both a two‐area interconnected power system and the IEEE‐39 bus system. The outcomes indicate that the suggested defense mechanism effectively maintains acceptable levels of power system frequency and tie‐line power during cyber‐attacks. Additionally, the validity of the controller's performance is verified through real‐time analysis using Hardware‐In‐The‐Loop (HIL) simulation with the OPAL‐RT platform.

Load frequency control in power systems with high renewable energy penetration: A strategy employing P[formula omitted](1+PDF) controller, hybrid energy storage, and IPFC-FACTS

The high penetration of Renewable Energy Sources (RESs) in the modern power system poses a challenge to power system stability. This stability is affected by the stochastic, fluctuating output of RESs, which is influenced by weather conditions, and a lack of inertia resulting from reduced rotating mass. To address this issue, a new controller, referred to as Proportional-Fractional Integrator Plus Proportional-Derivative with Filter, PIλ(1+PDF), is designed for Load Frequency Control (LFC) with the support of a Hybrid Energy Storage System (HESS) for power systems with high-RES penetration. The HESS comprises a Superconducting Magnetic Energy Storage System (SMES) and a Vanadium Redox Flow Battery (VRFB) coupled with an Interline Power Flow Controller Flexible AC Transmission Systems (IPFC-FACTs) controller. The HESS, working in conjunction with the proposed LFC, injects virtual inertia and maintains power flow to expedite the frequency stability process. These systems are also integrated with Alternating Current (AC) and High Voltage Direct Current (HVDC) transmission lines to collectively enhance both the system's stability and the capacity of its transmission lines. To optimize the PIλ(1+PDF) controller parameters, Zebra Optimization Algorithm (ZOA) is employed utilizing an Integral Time Absolute Error (ITAE) objective function. The proposed controller is tested on a four-area power system integrated with a wind turbine, photovoltaic (PV) panels, a biodiesel generator, and a hydrogen aqua electrolyzer fuel cell, representing a high penetration of RESs in modern power systems. The results are compared with those obtained using Proportional-Integral-Derivative (PID) and Fractional Order Proportional Integral Derivative (FOPID) controllers. Sensitivity analysis and robustness tests are also performed to verify the stability of the power network by changing system parameters and under randomly chosen loading conditions. The proposed PIλ(1+PDF) controller tuned with ZOA outperforms PID and FOPID controllers by minimizing settling time for frequency changes by 62 %, eliminating overshoot, and reducing undershoots for frequency and tie-line power changes by 73 % and 55 %, respectively. Simulation results demonstrate that the proposed controller outperforms PID and FOPID controllers by effectively damping frequency and tie-line deviations, resulting in reduced frequency overshoots, undershoots, and shorter settling times.

Disciplining a Rubidium Atomic Clock Based on Adaptive Kalman Filter.

Rubidium atomic clocks have been used extensively in various fields, with applications such as a core component of Global Navigation Satellite Systems (GNSS). However, they exhibit inherently poor long-term stability. This paper presents the development of a control system for rubidium atomic clocks. It introduces an adaptive Kalman filtering algorithm for the disciplining of a rubidium atomic clock, utilizing autocovariance least squares (ALS) to estimate the clock's noise parameters. The experimental results demonstrate that the proposed algorithm achieves a high estimation accuracy. The standard deviation of the clock error between the steered rubidium atomic clock 1 Pulse Per Second (1PPS) and Coordinated Universal Time (UTC) provided by the National Time Service Center (NTSC) is better than 2.568 nanoseconds(ns), with peak-to-peak values improving to within 11.358 ns. Notably, its frequency stability is reduced to 3.06 × 10-13 @100,000 s. The results for the rubidium atomic clock demonstrate that the adaptive Kalman filtering algorithm proposed herein constitutes an accurate and effective control strategy for the rubidium atomic clock discipline.

Frequency security-constrained unit commitment with fast frequency support of DFIG-based wind power plants

The integration of inverter-based renewable energy sources into power grids presents a unique challenge: a reduction in grid inertia, leading to potential frequency stability issues. This paper introduces an innovative approach to address this challenge, focusing on the dynamic role of wind power plants equipped with dual-fed induction generators (DFIG). Unlike traditional methods that rely on fixed inertia control strategies and wind power droop coefficients, our method offers a dynamic solution tailored to the fluctuating nature of grid frequency dynamics. We propose a novel variable inertia support mechanism, coupled with an optimized power point tracking control and strategic reserve, to maximize the effective use of wind power reserves without waste. Additionally, we account for the inherent uncertainties in wind power generation, enhancing the frequency support capabilities of wind turbines through a fast frequency response strategy. A key feature of our approach is the application of an advanced piecewise linearization fitting method to establish a robust frequency nadir constraint. This is integrated into a two-stage robust frequency security-constrained unit commitment model, enabling optimal real-time decision making for frequency stability in wind power plants. The efficacy and practicality of our proposed method are verified through a detailed case study on a modified IEEE 39-bus system and a hardware-in-the-loop experiment. Compared with the traditional fixed parameter control method, the cost is reduced by approximately 0.42%, while the linearization error at frequency nadirs remains within the range of -4% to 1.5%.

A novel hardware implementation approach to enhanced stable island operation of hybrid distributed generation using superconducting fault current limiters

In this research study, we have explored the transformative potential of integrating Superconducting Fault Current Limiters (SFCLs) and Superconducting Magnetic Energy Storage (SMEC) systems in hybrid distributed generation setups. Through a meticulous series of experiments, simulations, and detailed analyses, we have delved into the dynamic responses of these advanced technologies amidst various grid disturbances and fault scenarios. Our investigations encompassed a spectrum of grid disturbance scenarios, including voltage sags, frequency variations, and short circuits, revealing the crucial role that SFCLs and SMEC play in maintaining stable islanded operation. The numerical results showcased in this study demonstrate the pivotal role of SFCLs and SMEC in swiftly responding to grid disturbances, effectively limiting fault impacts and ensuring a continuous and uninterrupted power supply to critical loads. For instance, SFCLs reduced fault currents by up to 60 % within 15 ms during short circuit events at Node A, while voltage sags of 20 % were mitigated within 75 ms, showcasing a fault clearing time of 45 ms. Additionally, the SMES system's energy capacity of 10 kWh played a significant role in voltage and frequency stabilization, reducing fault impacts by over 50 % during various fault scenarios. Furthermore, our detailed analyses provide valuable insights into the SFCL performance, including activation times and fault current reduction capabilities. The transient responses of the system exemplify the remarkable ability of SFCLs to expedite fault recovery and stabilize microgrids. This study presents a novel hardware implementation approach aimed at enhancing the stable island operation of hybrid distributed generation systems through the integration of SFCLs and SMEC. The research addresses the pressing need for innovative solutions to ensure grid stability and reliability amidst the increasing penetration of renewable energy sources. Through hardware simulations, the effectiveness of SFCLs in limiting fault currents and improving system stability is demonstrated. Moreover, a quantitative comparison with existing solutions highlights the superiority of the integrated SFCL-SMES system in enhancing stable island operation, with fault tolerance improvements of up to 56 % compared to traditional methods. Overall, this research contributes to advancing the field of hybrid distributed generation and fault management, offering valuable insights into the practical implementation of SFCLs and SMES for grid resilience and reliable renewable energy integration.

Arthroscopy-assisted procedure provides less residual horizontal instability and optimal coracoid tunnel creation with less radiation exposure compared to percutaneous procedure after endo-button fixation of type III AC joint dislocations.

The aim of this study was to evaluate the postoperative radiological and functional results of patients treated with arthroscopy-assisted (AA) and percutaneous (P) procedures using endo-button for type III acromioclavicular joint dislocations with a minimum 1-year follow-up. The study hypothesis was that the AA technique would provide more favourable coracoid tunnels. This retrospective study included patients who underwent surgery between 2017 and 2022. Computed tomography images taken immediately postoperatively of all the patients were analysed to group coracoid tunnels as optimal or suboptimal based on orientation and placement within the coracoid base. Residual horizontal instability was assessed using the bilateral Alexander view at the final follow-up. Shoulder functions were evaluated at the final follow-up examination. Of the 63 patients, 39 underwent surgery using the percutaneous procedure and 24 with the AA procedure. Surgical duration was significantly longer in the AA group (AA: 61.1 ± 5.9 min; P: 34.7 ± 5.6 min) (p = 0.001; 95% confidence interval [CI]: 23.3-29.3), whereas fluoroscopy time was longer in the percutaneous group (AA: 2.0 ± 0.8 s; P: 15.7 ± 3.9 s) (p = 0.001; 95% CI: -14.9 to 12.3). Optimal coracoid tunnels were more frequently observed in the AA group (p = 0.001; 95% CI: 7.4-137.8). There was no significant difference in functional scores between the groups (n.s.). Postoperative horizontal instability was more common in the percutaneous procedure (p = 0.013; 95% CI: 8.3-39.2). Although no difference was detected between the methods in terms of complications and functional results, the higher frequency of residual horizontal instability, the high risk of suboptimal tunnel creation and greater radiation exposure were seen to be the most important disadvantages of the percutaneous technique. During surgery, such technical problems related to the percutaneous method should be kept in mind and care should be taken about the orientation of the coracoid tunnel. Level III.

Passive harmonic mode-locking in Tm–Ho doped fiber laser with MoS2–ZnO saturable absorber deposited on the arc-shaped fiber

This work reports a harmonic mode-locked Tm–Ho doped fiber laser (THDFL) using newly fabricated MoS2–ZnO as a saturable absorber (SA). It generates harmonic mode-locking (HML) operation with a center wavelength of 1911.4 nm and a 3-dB bandwidth of 3.02 nm. The fundamental repetition rate and pulse width were 14.1 MHz and 2.05 ps, respectively. Based on the radio frequency (RF) spectrum, the observed signal-to-noise (SNR) of the fundamental HML pulse was 67.22 dB. Increasing the pump power with fine-tuning of the polarisation controller (PC), higher order HML pulses were also observed using the MoS2–ZnO SA. The highest stable HML frequency was 300 MHz, observed at the 21st HML. The central wavelength and 3-dB bandwidth of the HML pulse were 1915.2 nm and 2.29 nm, respectively. The 21st HML pulses demonstrated a SNR of 40.09 dB. No supermode noise was observed in the RF spectrum, indicating that the 21st HML pulses were relatively stable. With industry demand, this high repetition rate HML with MoS2–ZnO SA opens new avenues for comprehension and manipulation of electronic phenomena, paving the way for future innovations in ultrafast lasers.

Dependence of frequency-temperature stability on support tethers in dual-beam piezoresistive sensing MEMS resonators

This paper investigates the dependence of frequency stability over temperature on support tethers in dual-beam piezoresistive length-extensional (LE) mode microelectromechanical systems (MEMS) resonators. The designed dual-beam resonator consists of two identical single-crystal silicon beams, which are mechanically coupled and excited into vibrating in opposite phase to eliminate the inherent capacitive feedthrough signals. Both straight and folded beams are adopted as the support tethers for the reported dual-beam piezoresistive resonators. Quality factor (Q) and temperature distribution across the resonators with various support tethers are investigated by finite element method (FEM) analysis. It is found that folded beam tethers can reduce the support loss and hence improve the Q for the designed dual-beam resonator, while it comes with a tradeoff of high temperature rise on resonator body. The reported dual-beam resonator with straight beam tethers has low temperature rise on the resonator body, which is less sensitive to environmental temperature fluctuations, compared to its counterpart with folded beam tethers. Experimental results show that the fabricated dual-beam piezoresistive resonator with four straight beam tethers achieves a 0.5 ppm frequency shifts in the temperature-control chamber, which is nearly four times better than those with folded beam tethers.

Research on Inter-Satellite Laser Ranging Scale Factor Estimation Methods for Next-Generation Gravity Satellites

The scale factor serves as a ruler for converting raw phase measurements into physical displacements and significantly impacts the preprocessing of data from the Laser Ranging Interferometer (LRI) in laser ranging systems. In the current GRACE Follow-On (GRACE-FO) mission for low–low tracking gravity satellites, most of the existing LRI scale factor estimation algorithms heavily rely on cross-calibration between instantaneous/biased ranges from the Ka-Band Ranging Interferometer (KBR) and the LRI. However, due to the nonlinearity of the objective function (which includes terms involving the product of scale and time shifts), the scale factor estimation may absorb errors from timing noise. Moreover, future gravity missions or gravity detection tasks may no longer incorporate KBR ranging instruments. To address these challenges, this paper proposes an energy-based method for scale factor estimation using inter-satellite baseline solutions. Comparative analysis indicates that the proposed method effectively disentangles two parameters in the objective function and can be applied in scenarios where KBR data are unavailable, demonstrating promising prospects for practical application. The experimental results show that when the KBR validation residuals are lower than 0.8 mm, the SYSU LRI1B V01 products exhibit residuals below the payload design accuracy thresholds in the frequency band of 2 mHz to 0.1 Hz. Additionally, the stability of the scale factors obtained from the baseline can reach 10−7. Although this is still below the required precision of better than 10−8 for the laser frequency stability in next-generation gravity satellites, advancements in orbit determination technology and the enhanced stability of GPS receivers offer potential for future precision improvements. Currently, this method appears suitable for roughly extracting the scale factor as a stochastic mean over several months or serving as a backup validation strategy for future missions, but it is not well suited to measure day-to-day variations.

Review of Biphoton Sources Based on the Double‐Λ$\Lambda$ Spontaneous Four‐Wave Mixing Process

AbstractThis review article focuses on biphoton sources based on the double‐ spontaneous four‐wave mixing (SFWM) process in laser‐cooled as well as room‐temperature or hot atomic ensembles. These biphoton sources have the advantage of providing stable frequencies, ultranarrow linewidths, and a tunability of the temporal biphoton width of more than one order of magnitude for high‐bandwidth applications. Therefore, the generated photons can be efficiently interfaced to, e.g., atomic quantum memories. In contrast, solid‐state biphoton sources typically require assistance by an optical cavity to operate at narrow linewidth that limits the tunability of the temporal width of the biphotons. Present state‐of‐the‐art double‐ SFWM biphoton sources can achieve one of the following results: a spectral linewidth of 50 kHz (290 kHz) or a temporal width of 13 (580 ns) with cold (hot) atoms, a detection rate of about 7 cps, and a generation rate of cps at a duty cycle of 0.4% or of cps in the steady state. The theoretical background of these biphoton sources, experimental implementations with cold and hot atoms, and progress over the years, will be illustrated.

Highly stable energy-storage performance of donor-acceptor co-doped TiO2 films

Energy-storage films that remain stable at high temperatures and frequencies are crucial for various applications. In this study, we demonstrated that donor-acceptor co-doped simple oxide TiO2 films, viz. V5+-Cr3+ co-doped TiO2 [(V0.5Cr0.5)xTi1-xO2] films, can exhibit highly stable energy-storage performance. The co-doped TiO2 films exhibited high breakdown strength and polarization owing to the local polarization induced by the V5+-Cr3+ ionic pairs. The energy-storage density of the (V0.5Cr0.5)0.02Ti0.98O2 film was approximately 48.93 J/cm3 at room temperature, which is approximately 195 times higher than that of the pure TiO2 film (0.25 J/cm3). In addition, the (V0.5Cr0.5)0.02Ti0.98O2 film exhibited excellent temperature stability from 303 K to 403 K, frequency stability from 0.5 kHz to 7.5 kHz, and fatigue durability over 107 charge-discharge cycles. The proposed strategy can effectively improve the stable energy-storage performance of lead-free donor-acceptor co-doped TiO2 films, which are in high demand in various applications.

Pound–Drever–Hall feedforward: laser phase noise suppression beyond feedback

Pound–Drever–Hall (PDH) laser frequency stabilization is a powerful technique widely used for building narrow linewidth lasers. This technique is, however, ineffective in suppressing high-frequency (>100kHz) laser phase noise detrimental for many applications. Here, we introduce an effective method that can greatly enhance its high-frequency performance. The idea is to recycle the residual PDH signal of a laser locked to a cavity by feedforwarding it directly to the laser output field after a delay fiber. Using this straightforward method, we demonstrate a phase noise suppression capability about four orders of magnitude better than just using the usual PDH feedback for noise around a few MHz. We further find that this method exhibits noise suppression performance equivalent to cavity filtering. This method holds great promise for applications demanding highly stable lasers with diminished phase noise up to tens of MHz (e.g., precise and high-speed control of atomic and molecular quantum states).

Synchronization bandwidth enhancement induced by a parametrically excited oscillator

The synchronization phenomenon in nature has been utilized in sensing and timekeeping fields due to its numerous advantages, including amplitude and frequency stabilization, noise reduction, and sensitivity improvement. However, the limited synchronization bandwidth hinders its broader application, and few techniques have been explored to enhance this aspect. In this paper, we conducted theoretical and experimental studies on the unidirectional synchronization characteristics of a resonator with phase lock loop oscillation. A novel enhancement method for the synchronization bandwidth using a parametrically excited MEMS oscillator is proposed, which achieves a remarkably large synchronization bandwidth of 8.85 kHz, covering more than 94% of the hysteresis interval. Importantly, the proposed method exhibits significant potential for high-order synchronization and frequency stabilization compared to the conventional directly excited oscillator. These findings present an effective approach for expanding the synchronization bandwidth, which has promising applications in nonlinear sensing, fully mechanical frequency dividers, and high-precision time references.

Sub-kilohertz linewidth free-running monolithic cavity VECSEL with 10−12 stability

We report the development of a compact, highly stable, monolithic-cavity, GaInP/AlGaInP-based vertical-external-cavity surface-emitting laser (VECSEL) with electronically tunable emission wavelength centered at 689.4425 nm for neutral strontium (Sr)-based applications. The output power reaches 40 mW (pump-power-limited) with ultra-low frequency and intensity noise performance resulting in a free-running linewidth of 720 Hz, reduced to 390 Hz when frequency locked to a reference cavity and verified via a heterodyne beat note measurement with 2 s averaging time. For shorter averaging times (0.1 ms), the free-running linewidth is as low as 40 Hz. We estimate a Lorentzian, or intrinsic, linewidth of 64 mHz from the frequency noise power spectral density at high frequencies, thus providing further evidence of the ultra-narrow fundamental linewidth of VECSELs. High frequency stability was measured via Allan deviation resulting in 1.05 × 10−12 at 2 s and 2.11 × 10−13 at 7 s averaging times when the 689 nm monolithic cavity VECSEL is free-running and locked, respectively, suitable for neutral Sr-based quantum technologies, such as optical clocks and atom interferometry.

Frequency stability of new energy power systems based on VSG adaptive energy storage coordinated control strategy

A self-adaptive energy storage coordination control strategy based on virtual synchronous machine technology was studied and designed to address the oscillation problem caused by new energy units. By simulating the characteristics of synchronous generators, the inertia level of the new energy power system was enhanced, and frequency stability optimization was achieved. This strategy is integrated with the frequency response model of the new energy power system to improve the system's frequency regulation capability and achieve more stable and efficient operation. From the results, the damping of the system increased, the oscillation frequency decreased after a duration of about 15 s, and the system stability improved by 76.09%. The proposed strategy based on virtual synchronous generator adaptive energy storage coordination control strategy was improved by 83.25%. In addition, the proposed strategy has improved stability indicators and system completion efficiency by 40.57% and 22.21% respectively, both of which are better than the comparative strategies. As a result, this strategy significantly enhances the frequency regulation capability of the system, which has a positive effect on achieving efficient operation of the new energy power system and maintaining the stability of the power system.