Transient Response Research Articles

Slosh-free feedback stabilization of liquid-propellant satellites with robustness to fuel density.

Transient response of a hygrothermoelastic cylinder with internal heat and moisture sources using non-Fourier hyperbolic coupled model

Context: This work applies an experimental methodology to the design of a control system based on a non-conventional Mamdani fuzzy controller that regulates the speed of an encoder-based DC motor.Method: The proposed methodology consists of four steps: i) fuzzy controller input/output selection, ii) fuzzy controller design, iii) controller hardware implementation, and iv) membership function parameterization. This methodology generates seven pairs of unique error and control signalsthat are differentiated by experimentally adjusting the parameters of the triangular membership functions used for the fuzzy controller design, which was implemented in an Atmega328P micro-controller. For each of the seven approaches defined, an experiment was performed, performing a control action to obtain the transient response of the DC motor speed when the reference was a step-type signal.Results: The motor response and the reference signal were used to calculate the error, whose squared error integral was estimated to determine which experimental approach yielded the best fuzzy control results, i.e., with the lowest possible error.Conclusions: The proposed methodology ensures the minimization of the squared error integral between the signal to be controlled and the reference signal. For fitting 6, the performance index obtained was J = 0.0002, whichrepresents a decrease of ≈ 99.99 % with respect to the worst case (fitting 1), whose performance index was J = 4.10.

This works presents the design, simulation, and analysis of a Tow-Thomas architecture based biquad filter that can be used in the analog front-end circuit of a sweat test analyzer for the diagnosis of Cystic Fibrosis (CF)- a life-threatening genetic disease. The biquad filter has been chosen due to its least sensitivity to the variation of passive components, which is an essential feature for sensor interface circuits like sweat tester used in CF diagnosis. The Tow-Thomas operational transconductance amplifier (OTA) is the building block of this filter. This OTA has been designed using 45 nm process technology in the Cadence environment. o be used using 45 nm technology process in Cadence environment to achieve high gain, wide output swing, low noise, and good transient response. The OTA has been optimized for a number of specifications which gain-bandwidth product, slew rate, phase margin, and power dissipation by conducting detailed AC, transient, and noise analyses. The OTA design utilizes a combination of NMOSs and PMOSs, with special consideration for minimizing the circuit size to integrate into compact wearable devices, such as a smartwatch. Challenges encountered during the project include sourcing appropriate sensors and balancing cost-efficiency with performance accuracy. The proposed design demonstrates promising results, offering a potential solution for low-power, high-performance signal amplification in CF diagnosis.

This paper proposes a novel control strategy for a Unified Power Quality Conditioner (UPQC) to effectively mitigate voltage and current disturbances in three-phase four-wire (3P-4W) systems. Existing UPQC control approaches often struggle to address unbalanced load conditions, resulting in significant power quality degradation. This research addresses this gap by introducing a fast fuzzy logic (FFZ) controller, which, in comparison to traditional PI controllers, offers enhanced performance in managing DC voltage fluctuations and generating accurate reference currents for the shunt active filter. The proposed FFZ controller effectively minimizes the impact of unbalanced loads on DC voltage, reducing error and improving overall system performance. Simulation results using MATLAB validate the effectiveness of the FFZ controller in reducing total harmonic distortion (THD) and improving transient response, demonstrating its superiority over traditional PI control for unbalanced load scenarios.

Modified hard-constrained PINNs for physically consistent microgrid transient response modeling

Semianalytical Solution for the Transient Response of Multilayered Unsaturated Viscoelastic Porous Media

This study presents a detailed numerical investigation of a floating offshore wind turbine (FOWT) subjected to focused wave excitation, utilizing a high-fidelity, fully coupled aero-hydro-mooring computational fluid dynamics model implemented in OpenFOAM. The analysis focuses on the National Renewable Energy Laboratory 5-MW reference turbine mounted on a semi-submersible platform. The influence of wave focus positions, located upstream (FP-US), at the mid-position (FP-M), and downstream (FP-DS), is systematically evaluated in terms of platform motions, mooring line tensions, aerodynamic loading, and wake recovery behavior. Time–frequency spectrograms are employed to characterize the non-stationary and transient responses induced by the focused wave conditions. The results indicate that pitch motions are significantly amplified in the FP-US and FP-M cases compared to FP-DS, with strong pitch and surge coupling observed. Surge motions are also more pronounced in FP-US and FP-M, where low-frequency components corresponding to the natural surge frequency contribute to prolonged dynamic responses. Mooring line tensions follow a similar trend, with substantially higher loads in FP-US and FP-M due to intensified wave-induced excitation. Additionally, FP-US and FP-M demonstrate improved aerodynamic performance and wake recovery, although accompanied by increased aerodynamic fluctuations resulting from platform motions. These findings indicate the importance of accounting for wave focus positions to improve the FOWT design and performance, especially for long-term stability and efficiency.

Abstract With the large-scale grid connection of doubly-fed wind turbines, the influence of their low-voltage ride-through (LVRT) characteristics on the power grid stability is increasingly prominent. In view of the distortion of external characteristics caused by the black box characteristics of the converter, this study proposes a parameter identification method for the double-fed wind turbine. Firstly, a high-precision dynamic model is established considering the timing control strategy during low wear, and the transient response mechanism of the unit is clarified. On this basis, the trajectory sensitivity technology is adopted to select characteristic parameters. A hierarchical identification framework is constructed in multi-operation scenarios, and the global optimization of control parameters is realized by integrating multi-source measured data. In order to verify the effectiveness of the method, the output characteristic comparison experiment of different voltage drop depths is carried out. The simulation results prove that the proposed method can accurately reproduce the external characteristic response of the actual double-fed unit.

Abstract With the large-scale integration of photovoltaic (PV) power into new power systems, traditional relay protection mechanisms face numerous challenges such as difficulty in fault identification and issues with protection device malfunctions or failures. This paper addresses these challenges by studying a longitudinal differential protection method based on model recognition for grid-connected lines. Through theoretical analysis and simulation validation, the proposed method can accurately identify faults under transient response control post-fault, meeting the requirements for speed and adapting to actual PV operation conditions, thereby enhancing the reliability and stability of new power systems.

Nonlinear time-domain finite element analysis to transient impact responses of Cattaneo-type thermoelastic diffusion with nonlinear Soret and Dufour effects for 2D metallic structure

Abstract A unique Moore–Gibson–Thompson (MGT) thermal conductivity model with memory-dependent derivatives is introduced in this work, which offers a fresh exploration of the thermo-electro-elastic transient response of a transversely isotropic piezoelectric hollow sphere. By addressing intricate interactions that are frequently missed in earlier research, the study offers a new look at the combined thermo-electro-mechanical behavior of the sphere under laser pulse heating applied to its traction-free inner surface. Detailed quantitative insights are obtained by solving the governing equations using a robust Laplace transform-based approach. Critical parameters, relaxation time, thermal conductivity rate, the kernel function, and pulse parameter time are all thoroughly examined in relation to the dynamic physical response. A variety of techniques, including both graphical and analytical ones, are used to analyze the system’s behavior. The results show significant advancements in our knowledge of the dynamic behavior of piezoelectric materials under complex mechanical and thermal loading scenarios. This study provides a major breakthrough in the field by combining the piezoelectric analysis with the memory-dependent MGT model. Its results represent a significant advancement in thermoelastic piezoelectric analysis and could be used to design next-generation materials, optimize thermal management systems, and create smart material technologies.

Abstract Numerous industrial, biological and geophysical fluids display the time-dependent rheological property known as thixotropy, in which the viscosity evolves over time and in response to changes in stress or strain rate. A wide range of phenomenological behaviour is associated with this property, and numerous models have been proposed and used to capture this. The aim of this paper is to classify systematically how modelling choices correspond to predicted behaviour, and, conversely, how observed behaviour can inform modelling choices. To this end, ‘ideal’ thixotropic models (without elasticity) are considered from a theoretical standpoint and the range of behaviour that different models can predict are explored. The approach is illustrated by considering the steady and transient responses to simple shear, with particular emphasis given to the role of the steady-state flow curve for a given model construction. The requirements for models to capture complex rheological phenomena like yield-stress ageing and “viscosity bifurcations” are outlined, and the implications of different modelling choices are discussed. The importance of carefully analysing the type of behaviour that a given thixotropic model can exhibit is highlighted.

Abstract N‐type conjugated ladder polymers without side chains, such as BBL, have been shown to exhibit record‐high mixed ionic‐electronic transport properties, which have enabled diverse device applications. This study reports herein the design and synthesis of a series of dicyano‐functionalized n‐type conjugated ladder copolymers, BBL‐x2CN, as new organic mixed ionic‐electronic conductors (OMIECs). By combining the cyanation and random copolymerization design motifs, this study demonstrates that the electronic band structure (LUMO/HOMO energy levels) can be effectively tuned as a function of the copolymer composition of the dicyano functional group without compromising the unique planar polymer backbone intrinsic to BBL‐type ladder polymers. Optimal mixed ionic‐electronic transport properties probed via organic electrochemical transistors (OECTs) are found in BBL‐202CN (20 mol%) devices that feature a high transconductance (≈3 mS), a good µC* value (≈2.8 FV−1cm−1s−1), and a fast transient response (τon/τoff = 40 ms/12 ms), which are substantially enhanced compared to those of the parent BBL of comparable molecular weight. The better OECT device performance found in BBL‐202CN copolymer, compared to other copolymers, can be explained by a combination of improved crystallinity, delocalization length, and suppressed conformational disorder. These results provide new structure‐property relationships with implications for the molecular engineering of high‐performance n‐type OMIECs.

As accuracy of the reflector surface of a space parabolic deployable antenna is an important factor to determine its electrical characteristics (transmission gain and side lobes), mechanical characteristics of parabolic antennas under various internal pressures should be studied. The objective of this paper is to explore the force analysis of parabolic antennas by theoretical method and to estimate the effect of different air pressures on the surface precision of parabolic antennas via experiments in horizontal and vertical directions, and then a numerical analysis of the vibration characteristics of the parabolic antenna is proposed to explore the transient response of parabolic antennas. It is found that the ratio of tension reduces as depth of the parabolic membrane increases and can infinitely converge to 1/2. For precision analysis, it is concluded that precision of the parabolic membrane surface in a vertical state is higher than that in a horizontal state.

Hydro-thermo-poro-viscoelastic model with non-singular fractional derivatives and transient heat-shock response of cylindrical unlined tunnel

Abstract The growing integration of electric vehicles (EVs) into modern energy systems presents an urgent need for innovative charging solutions that enable bidirectional energy flow and enhance grid stability, energy management, and the role of vehicles as distributed energy resources. This paper presents the design and analysis of an onboard bidirectional charging (OBD) system for vehicle-to-grid (V2G) and Vehicle-to-Load (V2L) applications. The system, rated at 50 kW, facilitates dynamic energy exchange between the EVs, grid, and local loads. A series-connected 43-cell lithium-ion battery with a nominal voltage of 3.7 V and 120 Ah capacity, a 230 V, 50 Hz grid supply, power electronics such as buck-boost converters, an Inductor-Capacitor-Inductor (LCL) filter, and a mode selector controller, designed in MATLAB/Simulink using dual Stateflow, governs battery state-of-charge (SoC) based operations. The simulation results indicate robust V2G and V2L mode performance when the SoC exceeds 40%. The system maintained a stable 400 V DC bus (\pm5 V) and provided consistent 12 V and 24 V outputs. The grid interaction demonstrated high power quality with sinusoidal voltage and current peaks of 325 V and 20 A, respectively. The battery voltage stabilised at 158.6 V with minimal oscillations, and smooth transitions between the V2G, V2L, and Grid-to-Vehicle (G2V) modes were observed. The proposed design facilitates efficient bidirectional power transfer by utilising a four-quadrant full-bridge inverter to enable both V2L and V2V energy exchange, with the mode selection governed by an SoC threshold of 40%. Key findings include rapid transient responses in voltage stabilisation with the V2L mode supplying power linearly with increasing load current, reaching 2100 W at 10 A, and low ripple in DC voltages, ensuring reliable performance under variable load conditions. In this study, the designed onboard bidirectional converter in the V2G mode has a power transfer efficiency of 84%–93% and a stabilisation voltage within ±4.7% of the nominal grid voltage, whereas in the V2L mode, it has a wider voltage fluctuation range of ±9% and a slightly lower efficiency of 78%–88%. The findings of this study reveal the viability of the system in enabling the integration of EVs as distributed energy resources in smart grid applications for energy management and grid support services, and provide important insights into the design of bidirectional charging systems with potential implications for improving control strategies and power quality in future grid scenarios.

This paper presents the comprehensive design, simulation, and experimental validation of a grid-tied hybrid renewable energy system tailored for electric vehicle (EV) charging applications. The proposed system integrates photovoltaic (PV) panels, a proton-exchange membrane fuel cell, battery storage, and a supercapacitor to ensure reliable and efficient power delivery. An adaptive neuro-fuzzy inference system (ANFIS)-based maximum power point tracking (MPPT) algorithm is employed to enhance PV power extraction under dynamically varying environmental conditions. Simulation results demonstrate effective voltage boosting from 110V to 150V and a regulated output of approximately 1100V at 30A, with the PV-side current stabilized at 500A. The fuel cell maintains a steady output of 110V while its current decreases from 40A to 25A, and the battery retains a 60% state-of-charge (SOC) at 120V output. The hardware prototype, developed using a DSPIC30F4011 microcontroller, achieves an MPPT efficiency of 98.7%, voltage regulation within ± 1.5%, and output power deviation under 2%. Grid voltage and current waveforms exhibit low total harmonic distortion (THD), in compliance with IEEE 519 standards, with measured values of 500V and 13A, respectively. The proposed architecture offers enhanced transient response, high energy efficiency, and superior power quality, positioning it as a promising solution for next-generation smart EV charging stations.

A quantitative analysis of the fault transient is critical for system resilience assessment and protection coordination. Focusing on hybrid modular multilevel converter (MMC)-based HVDC architecture with enhanced fault ride-through (FRT) capability, this study develops a mathematical calculation framework to quantify how controller configurations influence fault current profiles. Unlike conventional static topologies (e.g., RLC or fixed-voltage RL circuits), the proposed model integrates an RL network with a time-variant controlled voltage source, which can emulate closed-loop control response during the FRT transient. Then, the quantitative relationship is established to map the parameters of DC controllers to the fault current across diverse FRT strategies, including scenarios where control saturation dominates the transient response. Simulation studies conducted on a two-terminal MMC-HVDC architecture substantiate the efficacy and precision of the developed methodology. The proposed method enables the evaluation of DC fault behavior for hybrid MMCs, concurrently appraising FRT control strategies.

Aiming at the transient synchronization instability problem of grid-forming energy storage under a fault in the grid-connected inverter, this paper proposes an adaptive transient synchronization support strategy for grid-forming energy storage facing inverter faults. First, the equal area rule is employed to analyze the transient response mechanism of the grid-forming energy storage grid-connected inverter under faults, revealing the negative coupling relationship between active power output and transient stability, as well as the positive coupling relationship between reactive power output and transient stability. Based on this, through the analysis of the dynamic characteristics of the fault overcurrent, the negative correlation between the fault inrush current and impedance and the positive correlations among the fault steady-state current, active power, and voltage at the point of common coupling are identified. Then, a variable proportional–integral controller is designed to adaptively correct the active power reference value command, and the active power during the fault is gradually restored via the frequency feedback mechanism. Meanwhile, the reactive power reference value is dynamically adjusted according to the voltage at the point of common coupling to effectively support the voltage. Finally, the effectiveness of the proposed strategy is verified in MATLAB/Simulink.