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The post COVID-19 pandemic era has emerged with more efficient vaccines, all based on genetic materials. However, to expand the use of nucleic components as vaccines, a new generation of nanosystems particularly constructed to increase RNA/DNA stability, half-life and facilitate administration are still required. This review highlights novel developments in mRNA and pDNA vaccines formulated into nanostructures exclusively composed by biopolymeric materials. Recent advances suggest that a new generation of vaccines may arise by adapting the structural features of biopolymers with the effectiveness of nucleic acids. The advantages offered by biopolymers, such as increased stability and targeting ability may cause a revolution in the immunization field for offering promptly adaptable and effective formulations for worldwide distribution. Graphical Abstract Article highlights Polymeric biomaterials for nucleic acid delivery in vaccines We review the potential of chitosan, PLL, PEI, PLA and PLGA as mRNA/DNA vaccine systems. Chitosan Chitosan has significant potential for new intranasal vaccine designs. Poly(L-lysine) Vaccines based on PLL still require long, difficult and costly biomaterial modifications for translation. Poly(ethyleneimine) PEI's cytotoxicity may be circumvented by reducing the molar mass and using shorter chains. Poly(lactic acid) & poly(lactide-co-glycolide) PLA or PLGA lack chemical functionalities for optimal nuclei acid anchoring. Conclusion & future perspectives The cationic character causes a balance between nuclei material deliver efficiency and cytotoxicity. [ABSTRACT FROM AUTHOR]

Hall sensors are commonly used to detect rotor position information in permanent magnet synchronous motors (PMSM). However, due to the low resolution of Hall sensors, the speed signal directly collected by the motor during rotation contains significant random errors and noise. Using this signal directly may increase the error and jitter in the rotor position estimation, thereby affecting the control performance of the system. This paper proposes a novel position estimation method that combines the Kalman filter and phase-locked loop (PLL) to precisely obtain the rotor position. In the proposed method, to suppress the noise and errors of the speed signal, the state and observation equations are established using the Kalman filter algorithm. Additionally, to enhance the precision of the rotor position estimation, the position obtained by integrating the speed from the Kalman filter is processed using the PLL algorithm, and the PLL algorithm parameters are dynamically corrected. To verify the feasibility and accuracy of the proposed speed and position estimation method, simulations and experiments are performed, respectively. By adopting the proposed method, the speed error is reduced by 30% to 50%, and the current harmonic component is reduced by about 48.7%, which effectively improves the accuracy of the rotor position estimation. [ABSTRACT FROM AUTHOR]

ABSTRACT This study delves into the advancements, challenges, and opportunities in the solar grid technology, emphasizing its integration into the existing power infrastructure. The proposed ML‐FOGI (multilayer fourth‐order generalized integrator) algorithm presents a promising solution for modern grid synchronization requirements, addressing challenges posed by the integration of renewable energy into the distributed generation. This technology enhances system robustness and dynamic response, particularly in weak distribution grids characterized by voltage distortions and imbalances. This innovative approach enhances system stability and performance, particularly in polluted grid conditions. Through MATLAB/Simulink modelling and experimental validation, the effectiveness of the proposed control strategy is investigated across diverse testing conditions. Emphasizing the significant role of the control strategy in enhancing power quality and grid stability in the solar photovoltaic systems, this research underscores the importance of robust and adaptive control mechanisms for optimizing performance and ensuring grid reliability in modern microgrid. This study delves into this complex issue of working of the grid connected photovoltaic (GCPV) system, emphasizing the importance of balanced unit templates and a stable DC link voltage with unpredictable grid harmonics. This research aims to enhance the resilience of solar PV systems against grid disturbances by drawing inspiration from the adaptable nature of ADALINE filters and adhering to the IEEE519 requirements. This study employs OPAL‐RT's resilient experimental configuration. [ABSTRACT FROM AUTHOR]

Pulse width detection is an important issue, especially in PWM systems. Usually, in data receivers, PLLs are used to recover clock/data frequency or phase, and another circuit is used to reconstruct the pulse width. In this paper, a new locking loop is introduced which can lock to the duty cycle of the input signal, as well as to its phase and frequency. The main advantage is that the three characteristics are detected. The frequency range of the input signal is 700 MHz to 1.4 GHz with the duty cycle range of 30–70%, where the output signal of the suggested loop can be tracked in this range according to various simulation results in different situations. The circuit is designed and simulated using 0.18 um standard CMOS process parameters. The whole loop consumes about 10 mW using a 1.8 v power supply and the output signal RMS-jitter for 2000 cycles after loop locking is 3ps at 1 GHz frequency. [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]

Electromagnetic micro mirrors are in great demand for light detection and ranging (LiDAR) applications due to their light weight and low power consumption. The driven frequency of electromagnetic micro mirrors is very important to their performance and consumption. An electromagnetic micro mirror system is proposed in this paper. The model of the system was composed of a micro mirror, an integrated piezoresistive (PR) sensor, and a driving circuit was developed. The twisting angle of the mirror edge was monitored by an integrated PR sensor, which provides frequency feedback signals, and the PR sensor has good sensitivity and linearity in testing, with a maximum of 24.45 mV/deg. Stable sinusoidal voltage excitation and frequency tracking was realized via a phase-locked loop (PLL) in the driving circuit, with a frequency error within 10 Hz. Compared with other high-cost solutions using PLL circuits, it has greater advantages in power consumption, cost, and occupied area. The mechanical and piezoresistive properties of micro mirrors were performed in ANSYS 19.2 software. The behavior-level models of devices, circuits, and systems were validated by MATLAB R2023a Simulink, which contributes to the research on the large-angle deflection and low-power-consumption drive of the electromagnetic micro mirror. The maximum optical scan angle reached 37.6° at 4 kHz in the behavior-level model of the micro mirror. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic 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.)

In this study, a sliding mode observer (SMO) based on high-frequency (HF) voltage signal injection and a phase-locked loop (PLL) is proposed for estimating the extended electromotive force (EEMF), rotor position, and rotor velocity of an interior permanent magnet synchronous machine (IPMSM). This approach addresses real-time estimation challenges associated with standard SMO and PLL at very low speeds and standstill. A reliable and accurate sensorless speed control system for IPMSM is then developed and implemented in real time using the proposed SMO and PLL, covering a wide range of speeds, including low-speed and standstill conditions. The SMO effectively estimates the EEMF, while the PLL extracts the rotor velocity and position based on these estimates. Compared to conventional SMO and PLL methods, real-time results from an 8-pole, 0.4 kW IPMSM demonstrate the superior efficiency of the proposed system.

The generation of high-quality wideband frequency sweeps presents a significant challenge, particularly in modern telecommunication, radar, and measurement systems where miniaturization is paramount. While phase-locked loops (PLLs) have become the dominant technique for signal generation, their application in broadband sweeps necessitates fractional-N operation. This, in turn, degrades phase noise and introduces unwanted spurs. This paper proposes a novel approach for broadband signal generation. By cascading two PLLs and utilizing a coaxial resonator, we achieve a high-performance oscillator that operates without the excessive fractional spurs, maintaining their level below −80 dBc across the entire frequency band. The prototype demonstrates non-degraded phase noise performance, reaching −102 dBc/Hz at 100 kHz offset and −121 dBc/Hz at 1 MHz offset for signals at 10 GHz. Despite significant frequency jumps, our design achieves lock times below 41 µs. These results, supported by theoretical analysis, validate the proposed method's effectiveness in generating low-noise broadband frequency sweeps, ideal for local oscillator applications. [ABSTRACT FROM AUTHOR]

To ensure precise phase estimation within the q-axis of the phase-locked loop (PLL), integrating a filter into the q-axis loop is essential to mitigate grid-voltage harmonics. Nevertheless, the intrinsic delay characteristics of this filter impede PLL synchronization during significant grid disturbances. This study begins by developing mathematical models for three types of filters—moving-average filter (MAF) for eliminating odd harmonic components, dq-frame cascaded delayed signal cancellation (dqCDSC) filter, and notch filter (NF). Following the reduction in filter orders, a third-order nonlinear large-signal model of the PLL, incorporating an additional q-axis internal filter, is formulated. Using phase plane analysis, this study investigates the transient synchronism of the grid-following converter (GFL) and explores the influence of delay time constants from the three PLL filters on its behavior while delineating the boundaries of their basins of attraction. Theoretical findings indicate that, relative to the traditional SRF-PLL, incorporating an internal filter into the PLL compromises the transient synchronous stability of GFL. Specifically, greater filter delay time constants exacerbate the GFL's vulnerability to transient instability amid substantial grid disturbances. Hence, careful consideration is essential when using MAF-PLL and NF-PLL in situations demanding high synchronization stability. The theoretical analyses are validated using Matlab/Simulink to verify their accuracy. [ABSTRACT FROM AUTHOR]

This study proposes a phase-locked loop using a two-point modulation technique for fast chirp generation. The frequency synthesizer consists of high- and low-pass regions. In the high-pass region, continuous frequency modulation was achieved using a charge digital-to-analog converter, while a self-calibration block compensates for the nonlinearity of the voltage-controlled oscillator. In the low-pass region, the synthesizer is locked to the desired frequency with a low spurious level using a divider, delta-sigma modulator, and digital phase interpolator. The design used a 28 nm CMOS process and consumed 32 mW power. The chirp bandwidth is 960 MHz with a chirp duration of 41.6 μs. The slope of the chirp is 21.3 MHz/us, with a root mean square error of 3.7 MHz. [ABSTRACT FROM AUTHOR]

Obesity and its associated comorbidities place a substantial burden on public health. Given the considerable potential of brown adipose tissue in addressing metabolic disorders that contribute to dysregulation of the body's energy balance, this area is an intriguing avenue for research. This study aimed to assess the impact of various polymers, including collagen type I, fibronectin, laminin, gelatin, gellan gum, and poly-l-lysine (PLL), on the in vitro brown adipogenic differentiation of dedifferentiated fat cells within a fibrin gel matrix. The findings, obtained through RT-qPCR, immunofluorescent imaging, ELISA assay, and mitochondria assessment, revealed that PLL exhibited a significant browning-inducing effect. Compared to fibrin-only brown-like drops after two weeks of incubation in brown adipogenic medium, PLL showed 6 (±3) times higher UCP1 gene expression, 5 (±2) times higher UCP1 concentration by ELISA assay, and 2 (±1) times higher mitochondrial content. This effect can be attributed to PLL's electrostatic properties, which potentially facilitate the cellular uptake of crucial brown adipogenic inducers such as the thyroid hormone, triiodothyronine (T3), and insulin from the induction medium.

This paper presents formulations for time-based first-order and second-order high-pass, shelf, and notch filters. These formulations are an extension to the existing literature where low-pass filters are already developed using a multiphase controlled oscillator in conjunction with a phase detector and charge pump. The presented high-pass filter expands the circuit by introducing a current-controlled delay line (CCDL) that provides a direct path from input to output. By combining the high-pass filter with the low-pass filter, we show that shelf and notch filters can be obtained without an increase in circuit complexity compared to the high-pass filter. The results show good matching between the ideal small signal and the simulated time-based large signal frequency response. The simulated of total harmonic distortion for the filters shows an increase in distortion due to the nonlinearities introduced by the CCDL for the high-pass, notch, and shelf filter compared to the existing low-pass filter. The derivation of the new filter types allows the creation of complex high-order time-based filters by combining multiple first- or second-order filters.

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]

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.

Electromagnetic micro mirrors are in great demand for light detection and ranging (LiDAR) applications due to their light weight and low power consumption. The driven frequency of electromagnetic micro mirrors is very important to their performance and consumption. An electromagnetic micro mirror system is proposed in this paper. The model of the system was composed of a micro mirror, an integrated piezoresistive (PR) sensor, and a driving circuit was developed. The twisting angle of the mirror edge was monitored by an integrated PR sensor, which provides frequency feedback signals, and the PR sensor has good sensitivity and linearity in testing, with a maximum of 24.45 mV/deg. Stable sinusoidal voltage excitation and frequency tracking was realized via a phase-locked loop (PLL) in the driving circuit, with a frequency error within 10 Hz. Compared with other high-cost solutions using PLL circuits, it has greater advantages in power consumption, cost, and occupied area. The mechanical and piezoresistive properties of micro mirrors were performed in ANSYS 19.2 software. The behavior-level models of devices, circuits, and systems were validated by MATLAB R2023a Simulink, which contributes to the research on the large-angle deflection and low-power-consumption drive of the electromagnetic micro mirror. The maximum optical scan angle reached 37.6° at 4 kHz in the behavior-level model of the micro mirror.

This paper presents formulations for time-based first-order and second-order high-pass, shelf, and notch filters. These formulations are an extension to the existing literature where low-pass filters are already developed using a multiphase controlled oscillator in conjunction with a phase detector and charge pump. The presented high-pass filter expands the circuit by introducing a current-controlled delay line (CCDL) that provides a direct path from input to output. By combining the high-pass filter with the low-pass filter, we show that shelf and notch filters can be obtained without an increase in circuit complexity compared to the high-pass filter. The results show good matching between the ideal small signal and the simulated time-based large signal frequency response. The simulated of total harmonic distortion for the filters shows an increase in distortion due to the nonlinearities introduced by the CCDL for the high-pass, notch, and shelf filter compared to the existing low-pass filter. The derivation of the new filter types allows the creation of complex high-order time-based filters by combining multiple first- or second-order filters. [ABSTRACT FROM AUTHOR]

Aiming at the problem of insufficient label data in the pipeline leak detection field, this paper proposes a pseudolabel (PL) adaptive learning method based on multiscale convolutional neural network (MSCNN) with the idea of transfer learning for pipeline leak aperture identification. First, the convolutional and pooling layers for transfer learning feature extraction are improved by using a dual-channel MSCNN. Second, the KL divergence function after dimensionality reduction is used to calculate the distribution distance between the source domain and the target domain to improve the robustness of distribution alignment in high-noise environments. In addition, considering the interference of PL noise, this paper develops a pseudolabel (PL) dynamic threshold to achieve the purpose of PL adaptive updating. Compared with the fixed threshold, the improved PL learning (PLL) can effectively improve the prediction accuracy of the model. The effectiveness of the method proposed in this paper is verified by predicting pipeline leakage conditions at different distances and under different pressures. The comparative analysis results show that the method in this paper is superior to other transfer learning methods in terms of prediction accuracy, stability, and convergence speed. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny 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.)

High-voltage flexible power systems, with their intrinsic characteristics, play an increasingly important role in electronic power systems. Synchronization between the inverter and the grid needs to be achieved by a phase-locked loop (PLL), the performance of which determines the quality of power transmission. This paper proposes a PLL adapted to extremely harsh grid conditions. Firstly, the traditional synchronous reference frame PLL and the dual second-order generalized integrator (DSOGI-PLL) are analyzed, and the errors in phase-locking and the shortcomings of these two methods in the presence of DC components in the grid are pointed out. Secondly, based on the harmonic grid voltage, a repetitive control internal model is introduced by DSOGI to realize the real-time tracking and regulation of the harmonic signals in order to suppress the harmonic voltage disturbance. In addition, a DC bias elimination and frequency adaptive method is proposed to solve the problems of DC bias and grid voltage frequency fluctuation in order to achieve adaptive tracking of the grid phase. Finally, the superiority of the proposed strategy is verified through simulations and experiments. [ABSTRACT FROM AUTHOR]

Based on the problems of sliding mode observer (SMO), such as strong parameter dependency, large overshoot, and severe inherent sliding mode chattering, this paper studies fuzzy control in depth using a sigmoid (s) function with smooth and continuous characteristics instead of a discontinuous symbolic function to design a new type of fuzzy sliding mode observer. Firstly, the boundary layer thickness was introduced to enable the system to achieve adaptive sliding mode gain adjustment based on the system state. Then, based on PLL technology, PI adjustment was used to obtain rotor position information. Finally, in order to verify the effectiveness of the new method, a model was built for experimental verification, and the simulation waveforms of the traditional sliding mode observer and the new fuzzy sliding mode observer were compared. The results show that the new fuzzy sliding mode observer can more accurately estimate rotor position and speed information. Under the same operating conditions, the rotational speed estimation error is only 3 r/min, the rotor position error is reduced by 0.1 rad, the overshoot is smaller, and the chattering is significantly reduced. [ABSTRACT FROM AUTHOR]

Megawatt solar plants are the reality now with nations looking for GW installed capacity. This high power is possible because of increased power levels in photovoltaic (PV) energy conversion systems. The multilevel converter (MLC) is the emerging technology for interfacing medium and higher voltage grids. This paper gives the design and analysis of transformerless grid interfaced single-stage 43-level Cascaded H-bridge (CHB)-based MLC for integrating large-scale solar PV plants with improved Total Harmonic Distortion (THD). Transformerless integration and reduced filter size, due to improved THD, contribute appreciable savings in the Capital Expenditure and Operation and Maintenance cost of the big solar PV plant. This paper also showcases the design-based strategy for deciding the levels used in the MLC, making it both efficient and economical. The control scheme comprises voltage-oriented control (VOC) with synchronous reference frame (SRF) and phase-locked loop (PLL). The low-frequency phase-shifted pulse width modulation (PWM) suitable for the cascaded MLC is used for modulation. The separate incremental conductance (InC) algorithm is used for the extraction of maximum power from each solar PV array. This algorithm takes care of the unforeseen insolation level changes, shading effect, ambient temperature, and other related factors of the multi-string SPV system. The simulation is performed in MATLAB/Simulink and validated on an OPAL RT simulator. Both steady-state and dynamic behaviors at different insolation levels of the considered system are studied. The performance is validated as per the IEEE-519 standard requirement. Decent decrease in THD of grid current is observed with low switching losses. [ABSTRACT FROM AUTHOR]

The global navigation satellite system (GNSS) spoofing technology is an important method to control the targets that pose threats and protect sensitive areas. Traction spoofing can gradually take over the tracking loop by spoofing signals. To achieve more covert spoofing of a receiver configured with phase lock loop (PLL) assisted delay lock loop (DLL) loop, the following research work has been carried out: First, the response of the combined loop to GNSS spoofing is analyzed; Second, a new asynchronous traction signal spoofing algorithm is proposed; in the design of the code rate and carrier frequency of spoofing signal, the dynamic performance of the loop is fully considered, while maintaining a good consistency with the carrier frequency. In the design of the power of the spoofing signal, the success rate of spoofing is improved as much as possible while avoiding absolute power monitoring. Finally, the calculation method of the parameters of the spoofing signal is given. Third, by building the GNSS signal generation software and software receiver platform to carry out experimental verification and through experimental comparison and analysis with many existing representative spoofing schemes, it is proved that the new algorithm can successfully achieve spoofing. The spoofing takes 107.8 s, which makes the local code rate increase 0.03 Hz, the carrier frequency increase 50 Hz, the average value of consistency spoofing detection is 9.40 × 10−3, and finally stabilized at the convergence value − 2.95 × 10−8, that is, during the spoofing process, spoofing signal maintains the consistency of the authentic signal, which can well avoid the consistency spoofing detection of the receiver, the effectiveness and superiority of the proposed algorithm compared with other spoofing methods are fully verified. [ABSTRACT FROM AUTHOR]

Abstract Here, the stability region of grid‐connected VSC with phase locked loop (PLL) is estimated. First, the conservative stability region is derived via the classical Lyapunov method. Then an energy function is constructed as the general stable condition for the VSC system. Based on the constructed energy function, two estimation methods of the system stability region by approximation of phase trajectory are proposed. The stability regions by the proposed methods are less conservative than that by the classical Lyapunov method. A stability evaluation function for the initial states of the VSC system is further proposed based on the estimated stability region. Time‐domain simulations verify the correctness of the proposed methods and the effectiveness of the stability evaluation function.

As wind and solar power penetration increases, more and more conventional power plants are being replaced; as a result, the nature of transient stability of the system evolves where the converter’s behaviour play dominating role during network events. This has necessitated a re-assessment of the nonlinear stability of the system. So far, the energy function-based transient stability method applied to synchronous machines has been applied to the converter-based system. However, there is ambiguity in terms of the damping quantification capturing the non-autonomous behaviour of the wind turbine systems, such as post-fault active current ramp rate control. This work aims to clarify the similarity between the synchronous machine model and a reduced large signal model of a wind turbine, and the difference in terms of the damping characteristics and how this impacts the system’s stability from a nonlinear perspective. A non-autonomous energy function is discussed that analytically proves that a wind turbine system with post-fault active ramp rate control is more stable compared to no ramp rate control. Finally, the stability boundary (region of attraction) is constructed and validated using time-domain simulation studies in PSCAD.

There is a rapid increase in the installed capacity of offshore wind power plants (WPPs) worldwide, and this trend will continue in the context of the recent EU energy crisis and the Ukraine war. As the share of the capacity of wind power plants increases in power systems, it is essential that WPPs can stay connected to the grid during different operational events and provide ancillary services. Recent research has identified the Phase Locked Loop (PLL) converter control as a contributing factor to instabilities driven by large-signal disturbances (i.e. severe grid faults). This type of instability is referred to as grid-synchronisation stability (GSS). In light of this, grid codes are being revised to secure the connection of WPPs and specify the services that need to be provided. To study GSS, it is essential to accurately model the wind turbine (WT) system and grid conditions. However, the actual WT models are often unavailable, black-boxed, or computationally too heavy to model in detail. Thus, simplified reduced-order models (ROM) resembling the actual system behaviour are the need of the hour. This paper presents an improved reduced-order model that considers a systematic approach to modelling the misalignment of the PLL angle in the converter states. Moreover, it considers the time-varying parameters and the step changes of initial states after fault triggering, which otherwise are neglected in the present literature. Our focus in this paper is to propose a novel WT ROM and demonstrate its effectiveness for offline studies. Based on transient stability studies, the improved reduced-order model accurately tracks the grid-angle post-grid disturbances, and its trajectory is a good match compared to a detailed simulation model in the time domain.

This paper presents a novel direct power control (DPC) based both on proportional–derivative and proportional–integral regulators (PD (1+PI)) with a simplified space vector modulation (SSVM) strategy for variable-speed multi-rotor wind turbine (VSMRWT) driven doubly-fed asynchronous generator (DFAG) without phase-locked loop (PLL). The proposed control, called DPC-PD(1+PI), is designed to reduces the active and reactive powers ripples and improve the current quality. The combination of PD and PI controllers is the principle of the designed DPC technique. The main advantage of this method is that the ripples of the active and reactive powers and the current harmonic distortion, which represents the major disadvantages of the conventional direct power control scheme, are more minimized. Furthermore, this technique achieves a high current quality, reduce the steady-state error of the active and reactive powers, and improve the response dynamic of the generator. The behavior of the designed strategy compared to the conventional direct power control in several different tests such as the random wind speed behavior, change of generator parameters, and variable demand for active power are the mainly aims of this study. A numerical simulation by Matlab software is achieved to confirm the validity of the proposed direct power control approach for a 1.5 MW DFAG-based VSMRWT. The simulation results showed that the designed direct power control scheme is better than the conventional direct power control scheme in terms of improving response dynamic, minimization of harmonic distortion of current (50.24%) and significant minimization of ripples of reactive power (47.50%) and active power (46.68%). Also, the designed direct power control scheme is very robust for random variations in the reference order and parametric changes of the generator.

Improper setting of phase-locked loop (PLL) control parameters is one of the key factors for the adverse dynamic interaction between wind turbine generators, resulting in the oscillation instability of wind power systems. In this study, considering the spatial distribution characteristics and dynamic heterogeneity of multiple PMSGs, the PLL-induced instability mechanism of the grid-connected PMSG wind farm is studied and a stability criterion is proposed to guide the parameter coordination of the PLL for multiple PMSGs. First, based on the dynamic equivalent modeling method of the homogeneous multi-agent system, a reduced-order model of the homogeneous wind farm dominated by PLL is proposed. The parameter region of PLL control to ensure stability was analytically examined based on the proposed stability criterion. Then, the stability of heterogeneous wind farm is analyzed by constructing an equivalent homogeneous wind farm that has the same dominant oscillation mode as the heterogeneous wind farm; that is, the stability is equivalent. Furthermore, the stability criterion of the heterogeneous wind farm is deduced, and the parameter coordination method of PLL control for multiple PMSGs is proposed. Modal analysis and nonlinear simulation were conducted to confirm the accuracy of the theoretical analysis.

Modern Global Navigation Satellite System (GNSS) signals are usually made of two components: a pilot and a data channel. The former is adopted to extend the integration time and improve receiver sensitivity, whereas the latter is used for data dissemination. Combining the two channels allows one to fully exploit the transmitted power and further improve receiver performance. The presence of data symbols in the data channel, however, limits the integration time in the combining process. When a pure data channel is considered, the integration time can be extended using a squaring operation, which removes the data symbols without affecting phase information. In this paper, Maximum Likelihood (ML) estimation is used to derive the optimal data-pilot combining strategy and extend the integration time beyond the data symbol duration. In this way, a generalized correlator is obtained as the linear combination of the pilot and data components. The data component is multiplied by a non-linear term, which compensates for the presence of data bits. Under weak signal conditions, this multiplication leads to a form of squaring, which generalizes the squaring correlator used in data-only processing. The weights of the combination depend on the signal amplitude and noise variance that need to be estimated. The ML solution is integrated into a Phase Lock Loop (PLL) and used to process GNSS signals with data and pilot components. The proposed algorithm and its performance are characterized from a theoretical point of view, using semi-analytic simulations and through the processing of GNSS signals generated using a hardware simulator. The derived method is compared with other data/pilot combining strategies with extended integrations showing the advantages and drawbacks of the different approaches. [ABSTRACT FROM AUTHOR]

The employment of microgrids and distributed power generation have exponentially increased over recent decades, due in part to the increased inclusion of renewable energies as these technologies become cheaper to install. However, microgrids are highly sensitive to power variation, leading to distortion of the grid voltage (amplitude and frequency changes) which could destabilize the entire microgrid under variation of loads and/or other power sources. In this context, a new control strategy is proposed for a photovoltaic grid connected system, operating under voltage variations typical of a low inertial electric power network. The main problem related to voltage fluctuation is that the variables may take the power converter out of the operating region, and therefore, all controllers, including the maximum power point tracking, will not work as designed. The analysis, based on the mathematical operating region, demonstrates that the control strategy can include overmodulation compensation—to overcome problems related to weak microgrids and systems variations—through the addition of smart power factor imposition and DC-link voltage variation in transient time when the variables are far from the nominal values. The proposal is validated through simulation in PSim®/Matlab® and implementation on a laboratory prototype, showing the feasibility of the designed algorithm. [ABSTRACT FROM AUTHOR]