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With the rapid advancement of digital processors, filters have been commonly implemented using microcomputers. In this study, a low-cost and compact Arduino Uno development board was used to realize digital lead and lag compensators. Arduino boards are very affordable. Consequently, they were investigated to see if they were capable of preserving the frequency response of continuous-time compensators. The experiments required a set of equipment including a function generator, an Arduino Uno development board, a PC-based oscilloscope, and a laptop. The signal frequency was varied from 0 to 500 Hz. Two discretization methods were employed, namely bilinear transformation and matched pole-zero mapping. The results showed that an Arduino Uno board can be utilized to implement lead and lag compensators to some extent. The discrete-time compensator preserved the capability of filtering out certain frequencies. The change in DC gain was negligible, however, there was a significant difference in the cut-off frequency and transient slope. For both discretization methods, the frequency responses at high frequency experienced a rippling profile.

This note considers the problem of output feedback stabilization for a class of nonlinear planar systems with unknown structures and measurements which prevent the construction of conventional state observers. By taking advantage of the stability-increasing capability of a lead compensator, we propose a dynamic output feedback controller to globally stabilize the uncertain planar systems. For the special case of linear planar systems with unknown coefficients, a finite-time output feedback stabilizer based on a nonlinear compensator is constructed for a faster convergence rate.

This paper presents a post-fault current control strategy for dual three-phase Interior Permanent Magnet (IPM) synchronous machines. The current controllers are designed based on the Vector Space Decomposition (VSD) algorithm. This take into account the equivalent harmonic inductance variation, which is then used to introduce the post-fault compensation control. A double three-phase IPM machine is modelled and operated in three different operating conditions: nominal, one three-phase set in short-circuit (SC), and one three-phase set in open-circuit (OC). By keeping the current loop bandwidth constant, the proposed fault-tolerant current controllers guarantee the same dynamic performance of the remaining healthy module after the faults occurred. In OC fault, the proportional and integral (PI) controllers are redesigned while adapting the inductance variation. For the SC case, constant stability margins are provided by cascading a novel lag compensator to the nominal controller. The current dynamics responses are analysed in both healthy and faulty conditions by means of Matlab/Simulink simulations. Experimental results on a 30kW six-phase IPM machine prototype with isolated neutral points and supplied by two custom three-phase converters, are demonstrating the effectiveness of the proposed control strategies.

On the battlefield of today, it has become an important requirement to hit moving or fixed targets by using tank or artillery ammunition with high precision. However, while there are many articles on guiding tactical missiles, it cannot found sufficient scientific study for guiding tank ammunition in the related literature. In this study, the laser BR-guidance method is offered to the classic tank ammunition with a diameter of 155 mm in order to give the tank a precision strike capacity, as different from the literature. First of all, an ammunition model is created with coefficients of the mass, inertia, and surface area and friction. In addition, an autopilot dynamic is modeled for the pitch and roll axes of the ammunition. Also, the atmosphere model and environmental factors are added to the model. In order to control this nonlinear model, a lead-compensator and a PD-controller are designed. In order for the results to be transferred to a real application, the accelerations obtained must basically be produced by the electric motors that will drive the control surfaces to be designed. At the end of the study, it is seen that both controllers can produce lateral accelerations within limits without reaching high saturation.

This article deals with the study of mathematical models and the assessment of the stability of the motion of ships, investigating properties of the system such as kinetics and stability. This is essential for the selection of suitable control methods according to the requirements set out for the problem. Some control methods require the author to specify control parameters before the operation of the system can be started. Therefore, the survey of the article is useful for the above problem. Control methods through simulation results (PID controller, lag compensator, and lead compensator) give me results that reflect properties of the system (the stability of the operation cycle of the ship model). In addition, control methods for this model, which serve for research and education, are also presented below. Simulation is done by Matlab.

The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction, such as weather, location, and soil conditions. However, there are other factors that have not been explored, yet they can have significant impact on the accuracy of the project time estimate. Recently, TxDOT raised a concern regarding the importance of the proper estimating of the lead/lag times in project schedules. These lead/lag times are often determined based on the engineer’s experience. However, inaccurate estimates of the lead/lag time can result in unrealistic project durations. In order to investigate this claim, the study utilizes four time sensitivity measures (TSM), namely the Criticality Index (CI), Significance Index (SI), Cruciality Index (CRI), and the Schedule Sensitivity Index (SSI) to statistically analyze and draw conclusions regarding the impact of the lead/lag time estimates on the total duration in highway projects. An Excel-based scheduling software was developed with Monte Carlo simulation capabilities to calculate these TSM. The results from this paper show that the variability of some lead/lag times can significantly impact the accuracy of the estimated total project duration. It was concluded that the current practices used for estimating the lead/lag times are insufficient. As such, it is recommended to utilize more robust methods, such as the time sensitivity measures, to accurately estimate the lead/lad times in the projects scheduled.

Purpose To develop a simplified aluminum compensator system for total body irradiation (TBI) that is easy to assemble and modify in a short period of time for customized patient treatments. Methods The compensator is composed of a combination of 0.3 cm thick aluminum bars, two aluminum T‐tracks, spacers, and metal bolts. The system is mounted onto a plexiglass block tray. The design consists of 11 fixed sectors spanning from the patient's head to feet. The outermost sectors utilize 7.6 cm wide aluminum bars, while the remaining sectors use 2.5 cm wide aluminum bars. There is a magnification factor of 5 from the compensator to the patient treatment plane. Each bar of aluminum is interconnected at each adjacent sector with a tongue and groove arrangement and fastened to the T‐track using a metal washer, bolt, and nut. Inter‐bar leakage of the compensator was tested using a water tank and diode. End‐to‐end measurements were performed with an ion chamber in a solid water phantom and also with a RANDO phantom using internal and external optically stimulated luminescent detectors (OSLDs). In‐vivo patient measurements from the first 20 patients treated with this aluminum compensator were compared to those from 20 patients treated with our previously used lead compensator system. Results The compensator assembly time was reduced to 20–30 min compared to the 2–4 h it would take with the previous lead design. All end‐to‐end measurements were within 10% of that expected. The median absolute in‐vivo error for the aluminum compensator was 3.7%, with 93.8% of measurements being within 10% of that expected. The median error for the lead compensator system was 5.3%, with 85.1% being within 10% of that expected. Conclusion This design has become the standard compensator at our clinic. It allows for quick assembly and customization along with meeting the Task Group 29 recommendations for dose uniformity.

Proportional-Integral (PI) controllers are widely accepted industrial controllers. These controllers also find their applications in wind energy conversion systems (WECSs). Although such controllers are well researched and developed too, their linear nature and sensitivity of their gains towards variations in plant’s parameter are some noticeable disadvantages associated with them. Moreover, tuning of their gains involves certain approximations, which leads to demean their accuracy. On contrary, the designing of lag-compensators is procedural and discussed well in literature. Although such compensators could not have drawn the attention of wind turbine manufacturers but may a potential candidate for future developments. The focus of this paper is to design phase-lag compensators and use them to extract maximum available power in the wind, at every wind speed upto its rated value. Ability of the compensators is assessed through detailed simulation of a PMSG based WECS in MATLAB/Simulink environment. Observed responses are motivating and demonstrates the effectiveness of the designed compensators.

A new approach for modeling lead–lag relationships in high-frequency financial markets is proposed. The model accommodates non-synchronous trading and market microstructure noise as well as intraday variations of lead–lag relationships, which are essential for empirical applications. A simple statistical methodology for analyzing the proposed model is presented, as well. The methodology is illustrated by an empirical study to detect lead–lag relationships between the S&P 500 index and its two derivative products.

To improve the robustness and stability of the LCL inverter connected to weak grid, this paper proposes a novel active damping based on voltage of point common coupling ( $\text{v}_{pcc}$ ) feedback. A phase lead compensator is proposed in the $\text{v}_{pcc}$ feedback loop to compensate system phase margin (PM). Theoretical analysis of the effectiveness, detailed parameter setting, stability analysis for proposed active damping adopting lead compensator, named as LC AD, are all described. Simulation and experiment results show that comparing to conventional high pass filter (HPF) AD, the proposed LC AD provides more effective damping effect for the LCL inverter adopting quasi-proportional resonant (QPR) controller under weak grid.

This paper deals with a Twin Rotor Aerodynamic System (TRAS). It is a Multi-Input Multi-Output (MIMO) system with high crosscoupling between its two channels. It proposes a hybrid design procedure that combines frequency response and root locus approaches. The proposed controller is designated as PID-Lead Compensator (PIDLC); the PID controller was designed in previous work using frequency response design specifications, while the lead compensator is proposed in this paper and is designed using the root locus method. A general explicit formula for angle computations in any of the four quadrants is also given. The lead compensator is designed by shifting the dominant closed-loop poles slightly to the left in the s-plane. This has the effect of enhancing the relative stability of the closed-loop system by eliminating the oscillation in its transient part but at the expense of greater rise time. However, for some applications, long rise time may be an allowable price to get rid of undesired oscillation. To demonstrate the proposed hybrid controller's performance numerically, a new performance index, designated by Integral Reciprocal Time Absolute Error (IRTAE), is defined as a figure to measure the oscillation of the response in its transient part. The proposed controller enhances this performance index by 0.6771%. Although the relative enhancement of the performance index is small, it contributes to eliminating the oscillation of the response in its transient part. Simulation results are performed on the MATLAB/Simulink environment.

This paper analyses Disturbance Observer- (DOb-) based robust force control systems in the discrete-time domain. The robust force controller is implemented using velocity and acceleration measurements. A DOb is employed in an inner-loop to achieve robustness, and another DOb, viz. Reaction Force Observer (RFOb), is employed in an outer-loop to estimate interaction forces and improve the performance of force control. First, the inner-loop is analysed. It is shown that the DOb works as a phase-lead/lag compensator tuned by the nominal design parameters in the inner-loop. The phase margin of the inner-loop controller and the bandwidth of the velocity-based (i.e., conventional) DOb are constrained not only by noise-sensitivity but also by the waterbed effect. This explains why we observe unstable responses as the bandwidth of the conventional DOb increases in practice. To eliminate the design constraint due to the waterbed effect, this paper proposes an acceleration-based DOb. Then, the robust force controller is analysed. It is shown that the design parameters of the RFOb have a notable effect on the stability of the robust force control system. For example, the robust force controller has a non-minimum phase zero (zeros) when the RFOb is not properly tuned. This may cause severe stability and performance problems when conducting force control applications. By using the stability and robustness analyses, this paper proposes new design tools which enable one to synthesize a high-performance robust force control system. Simulations and experiments are presented to validate the proposed analysis and synthesis methods.

The control delay weakens the active damping (AD) performance of digitally controlled LCL/LLCL -type grid-connected inverters (GCIs). The equivalent virtual impedance paralleled with the filter branch explains the effect of the capacitor-current-feedback AD. However, the virtual impedance appears capacitive or even negative due to the delay, which significantly weakens the effectiveness of AD. This paper proposes a single-cycle-lag compensator (SCLC) to eliminate the adverse effects caused by the control delay. The method retains effectiveness in applications with high resonant frequency or large control delay. It keeps system a positive equivalent resistance with a high equivalent inductance. The positive equivalent resistance leads to positive damping effect, while the high equivalent inductance causing little resonant frequency deviation can be neglected. Moreover, the effect of the impedance variation that causes the resonant frequency deviation is analyzed and the restrictions of the proposed method are discussed. By optimizing the LCL/LLCL filter parameters, the adaptability of the SCLC to the grid impedance variation can be further improved. With the SCLC, the LCL/LLCL -type GCIs achieve better steady-state and dynamic performances. Finally, experimental results are presented to verify the proposed method.

To eliminate harmonic components in estimated speed and position information generated by inverter non-linearities for the interior permanent-magnet synchronous motor (IPMSM) sensorless control, a second-order lead compensator-based quadrature phase-locked loop (SOLC-Q-PLL) is proposed for the sliding mode observer. An adaptive super-twisting sliding mode observer is taken to estimate back electromotive forces (EMFs) for IPMSM. Harmonic components in estimated position information generated by inverter non-linearities are analysed. Being dependent on the corresponding analysis, the SOLC-Q-PLL is proposed to eliminate sixth position estimation errors only by introducing a second-order lead compensator without causing phase delay for the phase-locked loop system. The introduction of the second-order lead compensator does not influence the bandwidth of the phase-locked loop system so that a fast transient response can be achieved, and this algorithm is easy to implement digitally due to its simple structure. Eventually, a series of experiments are conducted to validate the capability of the proposed algorithm.

This study presents an inverter current sampled double-loop proportional multi-resonant (PMR)-based control technique for three-level (3L) three-phase four-leg (3P4L) advanced T-type neutral point clamped (AT-NPC) stand-alone mode inverter. Apart from the conventional linear controller the PMR controller has the ability to track a sinusoidal reference and does not require any axis transformation. Therefore, the main advantage of the proposed control technique for a 3P4L inverter is to independently control the output phase voltages when feeding a single phase and/or three phase loads. This is achieved by the inverter current sampled double-loop controller with a lead compensator in order to increase the control system phase margin unlike the capacitor current sampled controller. Thus, the harmonic compensation capability of the controller is increased which strengthens the controller against highly non-linear load types. The design procedures of the controller for the system are analytically explained. Then, the steady-state and dynamic performance of the controller is tested in a 3L 3P4L AT-NPC inverter system through many simulations and experimental studies. The results verify the fast-dynamic performance and the achievement of the low total harmonic distortion with a maximum of 2.89% for the 3L 3P4L AT-NPC inverter system even under serious non-linear load type. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [215E357] This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Project 215E357. WOS:000520421100025 2-s2.0-85082387573

This paper investigates the lead–lag relationships in high-frequency data. We propose multinomial dynamic time warping (MDTW) that deals with non-synchronous observation, vast data, and time-varying lead–lag. MDTW directly estimates the lead–lags without lag candidates. Its computational complexity is linear with respect to the number of observation and it does not depend on the number of lag candidates. The experiments adopting artificial data and market data illustrate the effectiveness of our method compared to the existing methods.

Granger causality tests are being supplanted by new methods such as the Lead‐Lag Ratio, particularly in finance where data arrives at random times and systematic sampling often produces spurious results. Existing approaches are insufficient; outside of block‐sampling using a bootstrap, the lead‐lag ratio has generally been assessed against a benchmark of 1 without regard for statistical significance. We use simulations to generate a response surface for the Lead‐Lag Ratio. Our modelled critical values are applied to reassess the findings of three previous studies of lead/lag relations between financial return series with high frequency data. Our response surface method proves to be a convenient and efficient alternative to using a bootstrap.

The present work focuses on comparing a robust and a parameter-varying control design approach for automatically regulating blood pressure in critical hypotensive patients using vasopressor drug infusion. Mean arterial pressure (MAP) response of a patient subject to vasoactive drugs is modeled by a first-order dynamical system with time-varying parameters and a time-varying delay in the control input which limits the implementation of conventional control techniques. Two methods are examined to address the variability and the time-varying delay of the physiological response to the drug. First, a Pade approximation is used to transform the infinite-dimensional delay problem into a finite-dimensional model represented in the form of a non-minimum phase (NMP) system. A systematic parameter-varying loop-shaping control is proposed to provide the closed-loop system with stability and tracking performance in the presence of measurement noise and disturbances. Second, an internal model control (IMC) strategy is examined to design a fixed proportional-integral-derivative (PID) controller cascaded with a lag compensator by considering the time-varying model to be a perturbed uncertain system. To account for system uncertainty, the small-gain theorem is employed by which robust stability conditions are investigated. The proposed control methods are applied to critical hypotensive patient resuscitation to regulate MAP while considering the limitations posed by the time-varying parameters of the physiological response model and the large time-varying delay. Simulation results are provided and compared to evaluate the performance of the proposed control actions under various hypotensive scenarios.

This study was supported by the Institute of Management Research, Seoul National University.

This paper investigates the enactment of battery energy storage system (BESS) and static compensator (STATCOM) in enhancing large-scale power system transient voltage and frequency stability, and improving power export capacity within two interconnected power systems. A PI-lead and lead-lag controlled BESS is proposed for multimachine power system to provide simultaneous voltage and frequency regulation within the defined battery state-of-charge ranges and an equivalent Finnish transmission grid is used to evaluate the system performance. According to Australian National Electricity Market grid requirements, the performances of the proposed control schemes are compared with conventional PI controlled BESS and STATCOM under multiple temporary and permanent fault conditions. In addition, two adjacent disturbance events are also applied to evaluate system performance with BESS and STATCOM. Through simulation results, it is shown that when there is a ${\text{44}\%}$ increase in power export and the STATCOM fails, incorporating BESS improves the performance and justifies the novelty of this study. Moreover, the proposed lead-lag controlled BESS manifests better transient performance than BESS with PI-lead and traditional PI controller, in the event of divergent temporary and permanent faults.

This paper discusses the use of a stochastic metaheuristic population-based optimization algorithm known as the sine cosine algorithm (SCA) to design the parameters of a power system stabilizer (PSS) for damping electromechanical oscillations in a single machine connected to a large power system. The design of the PSS parameters was formulated as an optimization problem to minimize the objective function value. The SCA was used to obtain the best values of the PSS parameters under the objective function. Simulation was carried out by a linearized power system model. The lead lag controller was used as the PSS structure and the results from that were compared with those obtained by moth flame optimization and evolutionary programming. The results showed that the SCA is more effective than are the other techniques in exploration and exploitation to tune the PSS parameters and enhance the power system stability by damping oscillations in a range of loading conditions.

Low frequency oscillation (LFO) is one of the major concerns for reliable operation of the power system. This LFO occurs due to the failure of the rotor to supply sufficient damping torque to compensate the imbalance between mechanical input and electrical output. Hence, in this paper, we adopt a third generation flexible AC transmission system (FACTS) device named generalized unified power flow controller (GUPFC) based damping controller in order to investigate its effect for mitigating LFO for an single machine infinite bus (SMIB) system. To find an effective damping controller-optimizer pair, we integrate proportional–integral (PI) or lead–lag as a controller and grey wolf optimizer (GWO), differential evolution (DE), particle swarm optimization (PSO), whale optimization algorithm (WOA), and chaotic whale optimization algorithm (CWOA) as an optimizer. Later, we investigate the performances for the above mentioned controller-optimizer pairs through time domain simulation, eigenvalue analysis, nyquist stability test, and quantitative analysis. Moreover, we carry out two non-parametric statistical tests named as one sample Kolmogorov–Smirnov (KS) test and paired sample t − t e s t to identify statistical distribution as well as uniqueness of our optimization algorithms. Our analyses reveal that the GWO tuned lead–lag controller surpasses all other controller-optimizer combinations.

Dynamic inverse- (DI-) based control technique has been utilized in many applications and proven to be effective. Recently, the inverse dynamic control (IDC), an expansion to the classical DI technique, has been trending with implementation in many areas. It has been proved that IDC is capable of overcoming some limitations in DI-based techniques, particularly in cancellation of useful nonlinearities. This paper extends the implementation of IDC on the positional and speed control of the linear servo cart system. Simulation results further proves that IDC is an effective and robust controller evidently when comparing it with the proportional velocity and lead compensator controller.

Power System Stabilizer (PSS) is an important measure to increase damping and suppress low frequency oscillations of power system. During PSS test, the time constant of lead-lag compensator need to be configured, considering the inefficiency and optimization problem when configuring parameters empirically, this paper proposes automatic configuration method of PSS parameters based on Matlab, by setting the expected phase value at each frequency and constructing the objective function with the sum of phase differences square, the automatic calculation of PSS parameters under specific phase requirements at each frequency can be realized, the detailed steps of this method are given, and the method is verified during the PSS test of an 300Mw thermal-power generating unit finally.

Background:Theintegrationof mobileroboticplatformsin humangaitanalysisoffers thepotentialtodevelop multiple medical applications and achieve new discoveries. The aim of this paper is to presenta first design and validation of a ROS-based mobile robotic platform for human gait analysis.Methods:During the design stage, the model identification and the configuration of the control lawwere performed. The design of the control law required the integration of a lead compensator and aFiltered Smith Predictor (FSP). During the validation procedure, the accuracy of the system to retrievekinematic gait data and the main descriptors of gait disorders was calculated with respect to theground truth of a Vicon system. For this purpose, one hundred gait recordings were processed thanksto the collaboration of twenty participants. The participants walked in a one-way straight line gait.Results:Results showed high correlation and low error rates mainly in joint excursions from sagittaland transverse planes.Conclusion:This gait analysis system demonstrated several advantages compared with the currentapproaches. The use of a mobile robotic platform allowed gait analysis in long tracking ranges andwithout space limitations. Furthermore, the design of a suitable control law allowed a smooth trackingof the person. This led to optimal results when assessing joint excursions.Significance:This system represents a cost-effective and non-invasive alternative that could be usedfor human gait analysis applications., The research leading to these results has received funding from RoboCity2030-DIH-CM, Madrid Robotics Digital Innovation Hub, S2018/NMT-4331, funded by “Programas de Actividades I+D en la Comunidad de Madrid, Spain” and co-financed by Structural Funds of the EU . The authors would like to thank Faculty of Physical Activity and Sports Sciences - INEF, UPM, for the use of Sports Biomechanics Laboratory. The authors also acknowledge Enrique Navarro Cabello and Javier Rueda for their contribution during the experimental stage.

Motivated by the empirical evidence of high-frequency lead-lag effects and cross-asset linkages, we introduce a multi-asset price formation model which generalizes standard univariate microstructure models of lagged price adjustment. Econometric inference on such model provides: (i) a unified statistical test for the presence of lead-lag correlations in the latent price process and for the existence of a multi-asset price formation mechanism; (ii) separate estimation of contemporaneous and lagged dependencies; (iii) an unbiased estimator of the integrated covariance of the efficient martingale price process that is robust to microstructure noise, asynchronous trading, and lead-lag dependencies. Through an extensive simulation study, we compare the proposed estimator to alternative approaches and show its advantages in recovering the true lead-lag structure of the latent price process. Our application to a set of NYSE stocks provides empirical evidence for the existence of a multi-asset price formation mechanism and sheds light on its market microstructure determinants. Supplementary materials for this article are available online.

For high-fidelity quantum operations in ion traps, it is important to maintain the secular frequency of the trapped ions at a constant value. The radial secular frequency is proportional to the amplitude of the radio frequency (RF) signal applied to ion traps. Owing to the changes in the ambient temperature of a helical resonator and the minute vibration of the optical table, the amplitude can vary. Recently, a method for reducing the fluctuation in the RF signal amplitude, using a commercial universal proportional-plus-integral (PI) controller, has been introduced, which, in turn, reduces the secular frequency drift of the trapped ions. The method improves the capability to maintain the secular frequency at a constant value. However, the structure of the controller is fixed, thus, the control method cannot be changed to suit different experimental conditions, and the different feedback configuration cannot be implemented to increase the resolution. In this paper, we develop a field-programmable gate array (FPGA)-based feedback controller that allows the implementation of various automatic control methods and feedback configurations. In our experiments, the fluctuation in the amplitude of the RF signal was 1.806% using a commercial universal PI controller. The fluctuation was reduced to 0.099% using the developed FPGA-based PI controller, and to 0.102% using the developed FPGA-based lag compensator. By employing the developed FPGA control method, many other automating control methods can be applied to achieve a stable and high-performance control of the secular frequency.

Traditional power systems based on synchronous generators often feature low frequency electromechanical oscillations. However, the integration of renewable energy sources through power converters can help tackling this issue. In fact, thanks to the concept of Virtual Synchronous Machine (VSM), it is possible to make the inverters behave as real synchronous machines (SMs). This way, the inverters can be integrated into the grid as traditional SMs and can even outperform them when it comes to damping low frequency oscillations in the power system. In order to do that, proper damping algorithms must be adopted in the VSM model. Therefore, this paper presents a simple and straighforward damping method for VSMs based on a single lead-lag filter acting on the VSM active power feedback. The proposed method and its integration in the VSM model are described. Then, the proposed solution has been experimentally compared to conventional methods, along with comparison metrics, to highlight its benefits.

Background: A recent study in Nature Climate Change shows that due to reduced human activities during the Coronavirus disease 2019 (COVID-19) pandemics, daily global emissions of carbon dioxide decreased by 17% from the average level in 2019. With the gradual recovery of economic activity and human energy consumption, the emissions of greenhouse gas and pollution would rise again. Green bonds are considered a crucial tool to release climate finance. The green bond market can act as an essential bridge between capital providers (i.e. institutional investors) and sustainable assets (i.e. renewable energy).This study is the first attempt to examine co-movement and the lead–lag relationship between green bonds and global and sector renewable energy stock markets in the time and frequency horizons. We apply continuous wavelet, wavelet coherence, and line and non-line causality approaches on data during the period 2010–2020, coincidentally including the COVID-19 pandemic.Results: (1) Green bonds and renewable energy markets show evidence of a similar pattern based on the wavelet power spectrum, which shows high price volatility at small and medium scales, especially during periods of turbulence and crisis. (2) The dynamic connection between green bonds and renewable energy returns is weak (strong) on the short (long) time-scale. However, on medium-term time scales, the dependence between them is significant only during turbulent periods, such as the European Sovereign Debt Crisis 2012 (ESDC) and the COVID-19 pandemic. (3) With regard to causality, our results show unidirectional and bidirectional linear (non-linear) causality at low and high frequencies. Moreover, our finding reveals the fact regarding the lead–lag relationship that, most of the time and frequencies, no one market necessarily dominates the other.Conclusion: Our findings provide several remarkable policies and practical implications for market regulators and investors. Institutional investors can benefit by including green bonds in their portfolios to decrease their climate change risk and improve their environmental, social, and corporate governance rating in the portfolio. Considering that the dependence between green bonds and renewable energy stock prices varies over various time scales, investors with different investment horizons should make diverse investment portfolio and hedging choices. The finding is also relevant for formulating green finance policies and supporting renewable energy investments. Policy decisions on the transition of energy to a decarbonized economy should consider the consequences for green bonds, which are also critical for the transition to a climate-resilient economy.

A Harris Hawks Optimization (HHO)tuned dual interval type-2 fuzzy lead–lag (Dual-IT2FLL) based unified power flow controller (UPFC) is proposed to minimize oscillations in single and multimachine power systems. The proposed damping controller coordinates between the modulation index (MI) and phase angle of series and shunt converters of UPFC simultaneously and is designed using speed deviation, a remote input signal for stability improvement. The performance of the proposed controller is verified through nonlinear time and frequency domain simulations under different operating conditions. The graphical simulations and validations using OPAL-RT OP5600 are presented to access the stability performance. Comparison based on different performance indices (PIs), like mean, standard deviation, overshoots and settling time are also considered to prove the better performance of the proposed HHO tuned dual-IT2FLL based UPFC over others under different operating conditions.

The design objective behind lead and lag compensator is to meet the relative stability as well as to meet desired performance. Both in time domain or frequency domain, the compensator design can be carried out. Absolute stability of a system can be predicted from root locus approach. Simulation tool like tinkercad and wolfram alpha can provide easy access of different control engineering design performance, so that it helps all under graduate, post graduate and researchers can able to apply their knowledge to engineering application from any computing environment. And they can perform it at any time. By this passive learning is also possible with active engagement in the learning related to practical and theory. To judgment and easily understand on simulation, student can modify their design specification and get deeper knowledge on control system design engineering. one can also use opamp circuit to understand the compensator design performance.

This paper analyzes the impact of arbitrage opportunity changes on the price discovery process between the DAX30 index and the DAX30 index future within a short time scale. To this end, we use 5-min data, regime-switching models and the regime-dependent impulse response function. The results unveil the presence of nonlinearities in the cointegrating vector and the shortcomings of relying on linear assumptions. We also find that the presence of arbitrage opportunities alters the nature of the lead-lag dynamics: the more arbitrage opportunities, the greater the leading role of the futures market and the more pronounced the impact of unexpected shocks on prices.

The full-scale fatigue test of rotor blades is an important and complex part of the development of new wind turbines. It is often done for certification according to the current IEC (2014) and DNV GL AS (2015) standards. Typically, a new blade design is tested by separate uniaxial fatigue tests in both main directions of the blade, i.e. flapwise and lead lag. These tests are time-consuming and rather expensive due to the high number of load cycles required, up to 5 million. Therefore, it is important to run the test as efficiently as possible. During fatigue testing, the rotor blade is excited at or near its resonant frequency. The trend for new rotor blade designs is toward longer blades, leading to a significant drop in their natural frequencies and a corresponding increase in test time. To reduce the total test time, a novel test method aims to combine the two consecutive uniaxial fatigue tests into one biaxial test. The biaxial test excites the blade in both directions at the same time and at the same frequency, resulting in an elliptical deflection path of the blade axis. Using elliptical loading, the counting of damage equivalent load cycles is simplified in comparison to biaxial tests with multiple frequencies. In addition, the maximum loads in both main directions remain separated, while off-axis loading is introduced. To achieve such a test, specific load elements need to be arranged so as to equalize the natural frequencies of the test setup for both test directions. This is accomplished by adding stiffness or inertial effects in a specific direction. This work describes a new method to design suitable test setups. A parameterized finite element (FE) model of the test with beam elements for the blade represents the test setup. A harmonic analysis on the FE model can identify the load distribution and the test conditions of a specific test setup within seconds. An optimization algorithm that varies parameters of the model and searches for the optimal setup is then applied to the analysis. This approach allows the efficient determination of a test setup, suited to the predefined requirements. The method is validated by applying it to three different test scenarios for a modern rotor blade: (a) state-of-the-art uniaxial setups, (b) uniaxial setups including springs and (c) a biaxial setup. In conclusion, the resulting setups are evaluated in terms of test quality and efficiency.

Several active damping strategies have been proposed in the literature for grid-connected converters with LCL filter but there are not specific strategies for DFIG wind turbines. In this system, there is an interaction between the two converters of the back-to-back conversion structure, which must be properly modeled in order to design effective damping strategies for the LCL filter resonant poles. This paper proposes a robust active damping strategy for DFIG wind turbines with LCL filter that considers the special features of this system. In this technique the filter capacitor current is fed back through a lag compensator that adjusts the delay of the feedback loop to emulate a virtual impedance that has dominant resistive behavior in the range of possible resonance frequencies. It is shown that a similar damping of the LCL filter resonance is achieved when the strategy isimplemented in either of the two converters. This work was supported by the Spanish State Research Agency (AEI) under grants PID2019-110956RB-I00 /AEI/10.13039 and DPI-2016-80641-R.

Air conditioners (ACs) are widely considered as good candidates to provide operating reserve. Demand response rebound, i.e., the rebound peak of aggregate power, may exist when ACs are controlled by changing the set point temperature. The rebound peak during the recovery period, named lag rebound, may cause significantly higher demand than that prior to the reserve deployment event. The rebound peak during the reserve deployment period, named lead rebound, is rarely considered in previous researches but will constrain the duration time to a short period (e.g., 10 min), which greatly limits the utilization of ACs. This paper proposes an optimal sequential dispatch strategy of ACs to mitigate the lead–lag rebound, and thus realize flexible control of the duration time from minutes to several hours. To quantify the effects of lead–lag rebound, a capacity-time evaluation framework of the operating reserve is developed. On this basis, ACs are grouped to be dispatched in sequence to mitigate the lead–lag rebound. The co-optimization of sequential dispatch on the capacity dimension and time dimension forms a mixed-integer nonlinear bilevel programming problem, in which the consumers’ thermal comfort is also guaranteed. Case studies are conducted to validate the proposed strategy.

Affordable, locally managed, decentralized treatment technologies are needed to protect health in resource-poor regions where communities consume groundwater containing elevated levels of fluoride (F). Bonechar is a promising low-cost sorbent for F that can be produced using local materials and simple pyrolysis technology. However, the sorption capacity of bonechar is low relative to the quantities of F that must be removed to meet health criteria (typically several mg/L), especially at pH typical of groundwaters containing high levels of geogenic F. This necessitates large bonechar contactors and/or frequent sorbent replacement, which could be prohibitively costly in materials and labor. One strategy for improving the feasibility of bonechar water treatment is to utilize lead-lag series or staged parallel configurations of two or more contactors. This study used column testing to quantify potential benefits to bonechar use rate, replacement frequency, and long-run average F concentration in treated water of lead-lag series and staged parallel operational modes compared with single contactor mode. Lead-lag series operation exhibited the largest reduction in bonechar use rate (46% reduction over single contactor mode compared with 29% reduction for staged parallel) and lowest long-run average F levels when treating central Mexican groundwater at pH 8.2 containing 8.5 mg/L F.

We analyze the time-frequency co-movement of and lead–lag relationship between price indices of oil and 21 agricultural commodities and attempt to identify the leader and follower among the considered price indices for the 1980M1–2017M5 period. The empirical analysis is conducted using four wavelet tools: wavelet coherency, phase-difference, multiple correlation and multiple cross-correlation. The first two tools are used to identify the time-frequency co-movement of and lead–lag relationship between price indices of oil and 21 agricultural commodities, and the third and fourth tools are used to identify the leader and follower among all series of price indices across different scales. Our results on wavelet coherency show a high degree of co-movement at a long-run horizon for the entire period between the price indices of oil and coal, cotton, fishmeal, maize, rice, rubber and wheat. Furthermore, the connection between these commodity markets and the oil market strengthened after 2000, indicating the importance of financial crisis phenomena and geopolitical turbulence. Additional findings show that short-run investors should invest in the beef and swine (pork) markets, as they have very little correlation with the oil markets. The results of multiple correlation and multiple cross-correlation analysis show that the coffee price was leader or follower across all time scales, except wavelet scale 16, where barely was a leader or a follower.

This work proposes a novel design method for generalized order lead/lag compensators. With respect to the traditional lead/lag compensator, it introduces a new parameter, β, which is a non-integer number. A new design method of the compensator is introduced in order to quantify its design parameters. Compared to its integer order counterpart, the generalized order lead compensator facilitates with the unique solution of desired design specifications with maximum phase at the desired gain cross-over frequency to achieve reshaping of the loop frequency domain characteristics. On the other hand, generalized order lag compensator is designed so as to allow minimum phase lag at the new gain crossover frequency. Examples with simulation and real-time results are presented to validate the efficacy of the proposed approach.

Power system stabilisers (PSSs) are supplementary controllers connected to the excitation system of synchronous generators to damp electromechanical oscillations. Multi-band PSSs are reported as advanced PSSs with the ability to damp out all oscillation modes present in the power systems. This study presents the design of a robust fractional-order multi-band power system stabiliser (Fo-MBPSS) using a meta-heuristic hybrid algorithm for dynamic stability improvement of multi-machine power systems. The large bandwidth, memory effect and flat phase contribution in the frequency response of fractional-order controllers are exploited to make the Fo-MBPSS perform well against a wide range of system uncertainties. The parameter tuning problem of Fo-MBPSS is transformed to an optimisation problem that is solved using a hybrid algorithm by combining a dynamic genetic algorithm (DGA) with a standard particle swarm optimisation (PSO) algorithm. The performance of the proposed DGA-PSO-Fo-MBPSS is evaluated through eigenvalue analysis, non-linear time-domain simulations and some performance indices, in two different multi-machine systems under different loading conditions and disturbances. The results are compared with PSO-based conventional MBPSS and PSO based Fo-MBPSS (PSO-Fo-MBPSS) to establish the fractional parameter effect on the improvement of the system dynamic response and the relevance of the proposed hybrid optimisation technique in achieving robustness.

An agricultural tractor finds extensive application in agriculture and is used with various types of implements. When it is driven with an implement attached to its rear, on-road or on uneven terrain, it experiences excessive vibrations in the pitch plane, which results in front wheel lift-off as an extreme scenario. The objective of this paper is to minimize these vibrations caused due to road disturbances by automatically controlling the lifting and lowering of the implement with the help of a hydraulic actuator. Using a Linear Time Invariant (LTI) approximation, a model relating the current input and the force variation output on the implement was developed based on the analysis of frequency response and time response. The data used in this process were acquired from an experimental setup consisting of control valves, hydraulic actuator and hitch system. Since the lifting and lowering of the implement is controlled by separate solenoid valves, individual models were obtained for each of them. These models were the used to design a lag compensator in order to reduce the gain of the system in the desired frequency range while maintaining the control variable (current) within its design limits. Results showed that the designed lag compensator exhibited a positive performance by reducing the variation of force on the hitch point by 95.8% during lifting and 87.2% during lowering.