Search Results (504)

Grid-connected photovoltaic (PV) systems paired with battery storage are becoming a core element of low-carbon distribution networks. This paper develops a complete closed-form formulation together with an independent, simulation-based verification of a single-phase grid-connected PV-battery microgrid sized for high-irradiance residential conditions in Saudi Arabia, using measured solar-resource and tariff data for Riyadh. A 6.25 kW monocrystalline array feeds a 400 V DC link through a perturb-and-observe boost stage; a bidirectional converter couples a 13.5 kWh LiFePO₄ battery; and an IEEE 1547 smart inverter interfaces a 230 V grid through an LCL filter. Governing equations for every subsystem are derived and evaluated numerically, and a Python re-implementation of the phasor power-flow model verifies the analysis over a 24 h cycle run to periodic steady state, reproducing the reference design values with a mean absolute error of 0.5%. Using measured monthly solar-resource and temperature data for Riyadh, a full twelve-month analysis gives an annual self-sufficiency of 51.8% and a PV self-consumption of 72.9% for the optimised energy-management scheme. A dedicated time-domain switching simulation with FFT analysis shows that the LCL filter limits grid-current total harmonic distortion to 0.8%, far below the L-filter value of 6.2% and below the 5% current-distortion reference of IEEE 519 (full compliance additionally requires the PCC short-circuit ratio). Twelve-month, battery-size and load-sensitivity studies confirm robustness, and a techno-economic assessment based on the Saudi Electricity Company residential tariff quantifies levelized cost, payback and battery degradation, showing that economic viability hinges on tariff reform. Full article

We formulate and analyze a 26-dimensional nonlinear dynamical system governing a doubly-fed induction generator (DFIG) wind energy conversion system coupled to an infinite bus through a dynamic transmission line. Seven interacting subsystems—aerodynamics, a two-mass drivetrain, a fourth-order machine, rotor- and grid-side converter controllers, a phase-locked loop, and a pitch regulator—are assembled into a single vector field $\dot{\mathbf{x}}=\mathbf{f}(\mathbf{x},\mathbf{u})$ on ${\mathbb{R}}^{26}$, derived in dimensionless coordinates. Strict positivity of the determinant $\mathrm{\Delta }=L_s{L}_r-L_m^2=\sigma L_s{L}_r$ for every physically admissible machine renders the flux–current map invertible, so the right-hand side is well defined; the nodal Kirchhoff constraint forms a semi-explicit differential-algebraic relation that we eliminate to obtain an explicit ordinary differential equation. The central contribution is a constructive scheme for the equilibria: the 26 stationarity conditions $\mathbf{f}({\mathbf{x}}^{\star },\mathbf{u})=\mathbf{0}$ are solved by an iterative voltage-matching procedure converging to a residual below ${10}^{-11}$ per unit—essentially machine precision—which removes the spurious start-up transients common in reported simulations. Analytically chosen feedback gains induce a hierarchy of well-separated time scales, placing the closed loop in the multiple-time-scale class; the separation is made quantitative through explicit small parameters ${\epsilon }_i$ formed from the ratios of subsystem time constants. Numerical integration of a GE $3.6$ MW configuration confirms the construction: under stationary forcing, the rotor speed stays within $1.32\times {10}^{-5}$ pu of the equilibrium, and under a large-amplitude wind program ($11\to 14\to 9$ m/s) spanning the full operating envelope, it is regulated to within $0.065\%$, while the DC-link voltage deviation remains below $2.4\times {10}^{-5}$ pu and the power balance closes with residual below ${10}^{-3}$ pu, the ≈2% mechanical–electrical gap being the modeled losses. Linearization about the computed equilibrium yields a Jacobian whose spectrum lies entirely in the open left half-plane, establishing local asymptotic stability and exposing the individual electromagnetic, torsional, and control modes. The model furnishes a rigorously initialized, analytically transparent basis for linearization, spectral stability analysis, and bifurcation study. Its practical value is that a consistent equilibrium and a certified spectrum remove the start-up transients and undocumented tuning that otherwise let initialization artifacts masquerade as genuine dynamics, so that the model can serve as a trustworthy building block for weak-grid and wind-farm stability studies. Full article

This paper addresses indirect sensing in resonant, oscillating, and periodically forced sensors, where the physical measurand is not directly available as a static output but is encoded in the dynamic response of the device. The sensor and its excitation are described as a single autonomous system, in which the excitation phase and the slowly varying measurand define a compact state representation after the decay of transients. Within this setting, delayed samples of the available output define an observation map that can be inverted, under suitable smoothness and observability conditions, to reconstruct the measurand in a deadbeat-like fashion. Compared with a preliminary conference study based on a simplified scalar-output RLC benchmark, the present work extends the formulation to vector-valued outputs, introduces a local conditioning indicator based on the Jacobian matrix, and focuses on a micromechanical sensing case with nonlinear electromechanical transduction. The inverse observation map is approximated by a feedforward neural network trained on synthetic data generated from the autonomous model. The methodology is applied to a vibratory MEMS gyroscope, where the signed angular rate is reconstructed from a delayed-output sequence combining the nonlinear capacitive current readout and the known AC drive reference. The augmented output is introduced to overcome the lack of observability affecting the raw current signal over signed angular-rate ranges. Numerical results show accurate reconstruction in ideal conditions and provide a preliminary robustness assessment under additive output noise. Full article

Conventional active disturbance rejection control (ADRC) schemes for grid-connected inverters (GCIs) suffer from performance degradation under grid frequency fluctuations and voltage distortions, primarily due to the limited bandwidth of conventional extended state observers (ESOs) and their reliance on fixed-frequency internal models. To address these issues, this paper proposes a second-order repetitive ADRC (SRC-ADRC) strategy for LCL-type single-phase GCIs. The proposed method integrates a second-order repetitive extended state observer (SRC-ESO) and a frequency-adaptive proportional-quasi resonant (FPQ) controller. By cascading an additional internal model into the repetitive control-based ESO, the SRC-ESO achieves higher internal model gain and wider resonant bandwidth, significantly improving periodic disturbance estimation accuracy under off-nominal grid frequencies. The FPQ controller ensures reference current tracking without phase error and amplitude attenuation, while the control law and observer are decoupled for independent parameter design. The robustness and frequency adaptability of the SRC-ADRC are verified through theoretical stability analysis and frequency-domain evaluation. Experiments on a 1.5 kW LCL-type single-phase GCI platform show that SRC-ADRC provides better frequency robustness, stronger harmonic mitigation, and improved current-tracking performance than the comparison methods. Full article

The increasing penetration of inverter-based resources has significantly reduced system inertia, motivating the emergence of Fast Frequency Response (FFR) as a dedicated ancillary service. Existing methods for enabling wind power systems to deliver FFR universally treat the wind farm as a single equivalent turbine under uniform wind conditions, an assumption that is invalid in real large-scale wind farms where heterogeneous turbine types, rated capacities, inertia constants, and spatially non-uniform wind speed distributions render uniform allocation strategies suboptimal or operationally unsafe. This paper proposes a centralized wind farm-level FFR control framework that coordinates heterogeneous wind turbine generators (WTGs) and supercapacitor energy storage systems (SCESSs) through a prioritized two-tier dispatch hierarchy, in which SCESSs are assigned the highest dispatch priority and WTGs are engaged only when aggregate storage capacity is insufficient. A constrained optimization problem is formulated to allocate the individual FFR contribution of each WTG by minimizing the total kinetic energy extracted from the wind farm, while enforcing torque, electrical power, and rotor speed constraints for every unit with respect to turbine type, inertia constant, and prevailing wind condition. A coordinated rotor speed recovery strategy further eliminates secondary frequency disturbances during the post-FFR transition. The proposed framework is validated on a 138 MW heterogeneous wind farm simulation model comprising both Doubly-Fed Induction Generator and Permanent Magnet Synchronous Generator units interconnected to a modified IEEE 14-bus test system. The proposed method achieves a 38.85% improvement in frequency nadir relative to a baseline with no FFR provision, outperforming all investigated state-of-the-art approaches, while reducing total kinetic energy extraction from the wind turbine generators and eliminating secondary frequency disturbances during the post-FFR recovery phase. Full article

This paper presents a fast diagnosis and localization method for switch short-circuit faults (shoot-through faults) in three-phase current-source inverters (CSIs) based on the polarity and variation trends of normalized phase currents. Under short-circuit fault conditions, the variation trends of the two same-polarity phase currents change from opposite (normal) to identical. To capture this feature, an adaptive magnitude-normalization method is proposed, which adaptively distinguishes normal load variations from fault conditions and selects the corresponding normalization strategy, yielding constant-amplitude three-phase currents while retaining polarities and trends. The theoretical operating sector is determined from the current polarities, and the faulty switch is localized using the signs of the variation trends of the two same-polarity currents. The method applies to both single- and multiple-switch faults. Experiments on a 3 A, 50 Hz CSI prototype show an average localization time of 15 ms (0.75$T_{\mathrm{base}}$), accurate diagnosis under load (10–30 $\Omega$) and frequency (25–50 Hz) variations, and no need for additional hardware, confirming its effectiveness. Full article

To address the bottlenecks of conventional valve-controlled marine steering systems—characterized by high throttling losses, low efficiency, and high leakage risk—as well as the insufficient power density and impact resistance of electro-mechanical actuators (EMAs) for high-load steering of large vessels, this paper proposes and validates a high-performance integrated solution for an electro-hydrostatic actuator (EHA) for ship steering. First, a fifth-order electro–hydraulic–mechanical coupled dynamic model comprising a permanent magnet synchronous motor, hydraulic pump, hydraulic cylinder, and load is established. The validity and applicability boundaries of three simplifying assumptions—neglecting leakage, pipeline pressure losses, and steady-state fluid compressibility effects—are quantitatively analysed, with a total introduced error ≤3%. These assumptions are justified under medium-pressure, short-pipeline, and well-sealed conditions typical of marine EHA systems. Second, a composite control architecture combining outer-loop sliding mode control with inner-loop motor PID dual-loop control is proposed. Parameter tuning is performed using pole placement for the sliding surface and the Ziegler–Nichols critical ratio method for the inner loops, effectively suppressing hydraulic system parameter perturbations and random wave-induced load disturbances. Quantitative comparisons show that the proposed method reduces overshoot by 11.63% and improves sinusoidal tracking accuracy by 90.13% compared to conventional single-loop PID control. An integrated drive-control structure is designed, and a three-phase full-bridge inverter main circuit with wide-voltage input capability—including EMI filtering, soft-start, and LC filtering—is developed to accommodate the ±20% voltage fluctuations typical of ship power grids, thereby enhancing system integration and grid adaptability. Phased bench tests demonstrate that the settling time from no-load start-up to 200 r/min is only 0.01 s. When a sudden 20 N·m load is applied, the speed drop is less than 3%, and the recovery time is less than 0.025 s. The steady-state steering angle error does not exceed 0.12°, the maximum average steering rate reaches 3.33°/s, and the steering response time is within 0.3 s. All core performance indicators exceed the general technical standards for marine steering systems, with a 65.7% improvement in steady-state accuracy and a 62.5% improvement in response speed over conventional PID control. The research findings provide an effective general technical solution and experimental data support for the performance optimization and engineering application of marine EHA systems. Full article

This paper presents a bidirectional power flow control strategy for a grid-connected solar photovoltaic (PV)-based water pumping system employing a brushless DC (BLDC) motor drive. The proposed system enables continuous water pumping operation under varying solar irradiance conditions without the use of phase-current sensors while maintaining the motor at its rated operating speed. A single-phase voltage source converter (VSC) employs a unit vector template (UVT)-based control scheme that regulates bidirectional power flow between the utility grid and the dc-link, thereby supporting both grid-to-load and PV-to-grid power transfer. Excess photovoltaic energy can be exported to the utility grid during periods of reduced pumping demand, improving overall utilization of the available solar power. The voltage source inverter (VSI) driving the BLDC motor employs a PWM_ON_PWM switching scheme to reduce torque ripple while operating at fundamental frequency to minimize switching losses. The proposed system also incorporates maximum power point tracking (MPPT), power factor correction, and harmonic mitigation to improve power quality and ensure compliance with IEEE-519 requirements. The effectiveness of the proposed control strategy is evaluated through detailed MATLAB/Simulink R2023a simulations under various operating conditions. The simulation results demonstrate stable dc-link voltage regulation, bidirectional power flow capability, continuous pumping operation, and reduced torque ripple, highlighting the suitability of the proposed system for grid-interactive solar water pumping applications. Full article

This paper presents a robust fault-tolerant control (FTC) strategy for a multiphase PMSM-based propulsion system. The proposed approach combines an innovative super-twisting sliding mode controller (IST SMC) with a fault-tolerant model of the machine when an open-circuit fault occurs. The electrical propulsion system mainly has a two-line structure with a single DC source, a five-leg inverter and a Five-Phase Permanent Magnet Synchronous Motors (5-Φ PMSM), suitable for marine propulsion applications. Two main scenarios are investigated in this work. Firstly, if an open-phase fault occurs in one of the two 5-Φ PMSMs, a reconfiguration step of the machine control is applied in order to improve the performance of the propulsion system and to ensure the continuity of operation. Then, if the fault occurs in one of the two inverters, the faulty one is removed and the electrical series connection is made between the two machines, where they are powered by a single five-arm inverter, thus ensuring the continuity of operation of the system. Considering these two scenarios, a comparative analysis is made between the IST SMC and the classical PI controllers in terms of robustness to uncertainties, external disturbances and tracking accuracy for healthy and faulty operation modes, and during transient states. Full article

Transformerless inverters are increasingly becoming essential in renewable energy generation, particularly for grid-connected photovoltaic (PV) and other sustainable and alternative energy resources. The transformerless designs offer higher efficiency, compact size, and reduced cost compared to traditional inverters with bulky transformers. These inverters minimize energy losses and enable direct connection to the grid by removing the low-frequency transformer. This paper investigates a highly reliable single-phase common-ground inverter for solar panels and other alternative energy generation. The proposed PV inverter has the benefits of existing non-isolated common-ground PV inverters, including direct connection of an input source’s negative terminal to the AC neutral terminal, eliminating leakage ground currents. The inverter is an enhancement of the dual-buck inverter, incorporating one additional diode and a flying capacitor. The dual-buck structure with the inductor inserted between the inverter phase leg prevents short-circuiting. This increases the reliability of the entire power electronics system. Moreover, using external diodes to freewheel the current, the configuration has no reverse recovery issues, allowing power MOSFETs to be employed with safe commutation at higher DC-link voltage and achieve higher efficiency. Summarily, this design prevents short-circuit issues, enhancing reliability and efficiency, and relaxing pulse-width-modulation dead times. The derivation of the PV inverter is carefully analyzed. A 700 W prototype of power converter hardware has been built. The comparative study validates the operational performance, and the grid-connected experiment confirms its theoretical analysis. Experimental results of the hardware prototype are discussed to prove the feasibility and effectiveness of the proposed PV inverter. Full article

Accurate harmonic measurement is required for power quality (PQ) compliance in South Africa’s inverter-based renewable grids. The frequency response of the current transformer (CT) has been characterised through structured testing, while voltage transformers (VTs) remain untested under harmonic excitation in local conditions. This paper proposes a method for evaluating single-phase VT frequency response by adapting CT test strategies to voltage excitation. MATLAB R2025b Simulink models support interpreting measured data. The framework measures ratio and phase errors up to the 60th harmonic (3 kHz) and detects resonances important for PQ assessment. The study addresses a methodological gap in South African PQ measurement and supports the development of standardised procedures for evaluating VT frequency response in renewable power systems. Full article

Fatigue driving causes 20–30% of global traffic accidents. To address limitations in feature fusion and real-time performance, this study proposes an improved You Only Look Once version 8 (YOLOv8)-Long Short-Term Memory (LSTM) model with symmetry-aware spatiotemporal feature learning. In the spatial phase, Group Shuffle Convolution (GSConv) and Slim Neck structures are introduced to enhance facial feature detection while reducing parameters by 32.3%. In the temporal phase, an improved Inverted Transformer(iTransformer) with differential attention is integrated with an LSTM-Feed-Forward Network (FFN) architecture, achieving a 90.1% prediction accuracy and an 84.6% noise suppression rate. A standardized dataset of 13,200 images was constructed using a four-level classification system. By implementing TensorRT acceleration and multi-process parallel frameworks, the system optimizes single-frame latency to 38 ms—a 9.5× efficiency gain—while maintaining an overall detection accuracy of 92.4%. These results demonstrate that the proposed framework effectively balances model lightweighting with high precision, providing a robust and efficient solution for real-time driver monitoring in complex driving scenarios. Full article

To address the speed oscillation and stability degradation caused by load imbalance in a single−inverter dual−permanent magnet synchronous motor (PMSM) parallel system, this paper proposes an adaptive control strategy based on a sliding mode observer. The proposed method preserves the hardware simplicity of the single−inverter topology while improving control performance under load disturbances. First, a sliding mode observer is designed to estimate the load torque difference between the two motors in real time, thereby enabling dynamic perception of load variations. Then, an adaptive controller is introduced to switch the control mode according to the estimated load imbalance. When the load difference is small, master−slave vector control without fixed role distinction is adopted. When the load difference exceeds a predefined threshold, an improved finite−set model predictive torque control (FCS−MPTC) is activated. In the predictive control mode, unnecessary full−time predictive optimization is avoided and a d−axis current suppression term is incorporated into the cost function to improve current waveform quality. Simulation results show that the proposed strategy reduces speed overshoot during load transients and improves the three−phase current waveform compared with conventional predictive torque control. Therefore, the proposed method provides an effective control solution for single−inverter dual−motor drive systems under load disturbance. Full article

To improve the adaptability of single-phase inverters under different load conditions, this paper proposes a sensor-reduced control strategy based on unknown input observer (UIO). Under the assumption that the load current is bounded with known upper and lower bounds, the algebraic relationship between the capacitor voltage and load current is constructed by designing an interval observer. Furthermore, based on this relationship, a UIO is designed to realize the online estimation of inductor current and load current. Compared to existing control methods, the proposed scheme requires only the output voltage signal for sensing, effectively ensuring stable operation of the inverter under different load conditions while reducing system costs and improving reliability. Finally, simulation results verify the feasibility of the proposed approach. Full article

Grid-connected photovoltaic (PV) systems can serve not only as sources of active power but also as active power conditioners for improving power quality. This paper proposes an integrated control strategy for a single-phase grid-connected reduced-switch-count T-type inverter that simultaneously performs maximum power point tracking (MPPT) without a DC-DC conversion stage, compensates for nonlinear load harmonics, and minimises switching losses through a tailored multi-carrier pulse-width modulation (PWM) algorithm. A novel reference current derivation method based on a single-phase dq transformation framework unifies MPPT and active power filtering within a single control loop. The proposed system was validated through MATLAB/Simulink 2025b simulations for a 3500 W PV array supplying a nonlinear RL load with a full-bridge diode rectifier exhibiting a load current total harmonic distortion (THD) of approximately 46%. Simulation results demonstrate an MPPT efficiency of 99.8% at full irradiance (1000 W/m²), an overall system efficiency above 97%, and a grid current THD below 4% across the full irradiance operating range (0–1000 W/m²). Dynamic performance under step irradiance changes was also evaluated: the DC bus voltage deviation remains within 5 V for P&O step sizes between 0.00005 V and 0.0002 V, and the grid current THD recovers to below 5% within 2–6 grid cycles following each irradiance transition. Full article