Search Results (1,107)

This paper presents an optimized control strategy that enables a grid-connected photovoltaic (PV) system to operate as a static synchronous compensator (PV-STATCOM) to damp power oscillations in the transmission system, using an arithmetic optimization algorithm (AOA). The key contribution of this work is a synchronized, AOA-optimized multi-mode switching approach that includes standard PV operation, Full STATCOM, and Partial STATCOM with ramp-rate recovery, rather than relying solely on PI-gain adjustment. This is accomplished across the complete pre-fault, fault, and post-fault cycle. Under the proposed strategy, the PV system temporarily curtails its real power output when power oscillations arise following a system disturbance, thereby releasing the full inverter capacity for STATCOM operation and, hence, for oscillation damping. Once the oscillations are damped, the PV system ramps its real power back to the pre-disturbance level; at night, the inverter’s full capacity remains available for damping oscillations. The control scheme is implemented with a set of proportional–integral (PI) controllers whose parameters are tuned with the AOA, and its performance is benchmarked against tuning with the cuckoo search (CS) algorithm. Simulation results demonstrate that the AOA-tuned PV-STATCOM significantly improves damping, reduces oscillation amplitudes, maintains the point-of-common-coupling voltage within the low-voltage ride-through envelope, and keeps the system frequency within grid-code limits, thereby ensuring stable grid operation. Compared to a CS-tuned benchmark, the AOA-tuned design keeps the frequency continuously within the grid code band, settles at nominal 50 Hz, and reduces the maximum voltage overshoot from 20% to 15%. Full article

This study investigates the fixed-time quasi-consensus and quasi-containment control for multi-agent systems (MASs) under non-periodic unknown denial-of-service (DoS) attacks. Most available strategies fail to construct fixed-time observers and feasible corresponding parameter tuning rules to guarantee the precise fixed-time convergence of observer states to the convex hull trajectory spanned with multiple leaders under arbitrary non-periodic DoS interference. Moreover, most existing relevant fixed-time cooperative control methods for MASs commonly impose restrictive assumptions on system input matrices, requiring the matrix to be square and invertible, which severely limits their practical applicability. To overcome these limitations, the observers and corresponding parameter selection conditions are designed in this study, which can ensure that the observer states converge to the target trajectory formed by the leaders within a fixed time under non-periodic unknown DoS attacks. Then, based on the linear transformation of the state space and the theory of sliding mode control, a novel observer-based controller is proposed to solve the fixed-time quasi-consensus and quasi-containment control problems. The proposed approach remains effective even when, under mild conditions, the input matrix is non-square or non-invertible—a challenge that many existing methods cannot address. Finally, numerical simulations demonstrate that the proposed control strategy enables MASs with non-square input matrices suffering from unknown non-periodic DoS attacks to achieve fixed-time quasi-consensus and quasi-containment under mild conditions. Full article

Terrain-induced chassis motion can disturb the soil-entry attitude and soil engagement of seeding components on compact agricultural robots. This study develops an inverted 2RPU–RPS rallel mechanism for a maize seeding robot to regulate the end effector without levelling the entire chassis. The mechanism supports the disc opener and terminal seed tube and provides one vertical translation and two rotations. A nonlinear inverse-kinematic model, a unilateral penetration–downforce model, constrained electric-cylinder dynamics, and a coordinated feedforward–PI controller are established. The roll and pitch loops combine chassis-attitude feedforward compensation with end-effector error feedback, while the vertical loop regulates the opener downforce using a stiffness-based penetration reference and force feedback. MATLAB/Simulink simulations are conducted under isolated attitude disturbances, vertical terrain excitation, and multi-row operation. With maximum chassis roll and pitch disturbances of 4.49° and 3.35°, the end-effector RMSE values are 0.109° and 0.114°, respectively. At a prescribed downforce of 400 N, the downforce RMSE is 11.07 N and the mean disc-opener penetration is 34.99 mm. During the 300 s multi-row simulation, the mean penetration remains 34.96 mm and the downforce RMSE is 12.65 N. The results indicate that the strategy can attenuate chassis-induced disturbances and maintain stable soil engagement under the adopted modelling assumptions. Full article

To address junction-temperature fluctuations and thermal-fatigue degradation of IGBT modules in EV traction inverters under CLTC conditions, this study develops a hierarchical active thermal-management framework. A temperature-dependent loss model coupled with a fourth-order Foster thermal network is first established and evaluated against experimentally derived temperature references. The prediction errors are mainly within ±5 °C over approximately 30–145 °C, with a small number of larger deviations during rapid thermal transients. Speed-based feedforward scheduling, single-variable fuzzy feedback, and dual-variable fuzzy control coordinating switching frequency and cooling intensity are then evaluated in simulation. Rainflow counting and the Miner rule show cumulative-damage reductions of 57.09%, 66.70%, and 81.90%, respectively, while the dual-variable strategy increases the model-based equivalent lifetime from 5.32 to 31.99 years. The results demonstrate the benefit of coordinated heat-generation and heat-dissipation control for inverter thermal reliability. Full article

Urban form profoundly influences the effectiveness of coordinated management of carbon emissions and air pollution, which is of great significance for sustainable urban development. This study took 336 Chinese cities as research samples and used carbon emissions, PM_2.5, and nighttime light datasets from 2000 to 2020 to investigate the contribution of urban form to the degree of coordination between urban carbon emissions and PM_2.5. We constructed a multi-dimensional indicator system for urban form and adopted the coupling coordination degree (CCD) model to quantify the coordinated development of these two variables. A novel analytical framework was established using the stacking ensemble learning model. Combined with the SHAP method, this framework provided nonlinear associations of various urban morphological factors with the CCD. The results are as follows: (1) The stacking ensemble model performs best in capturing high-dimensional nonlinear relationships, with test set R², RMSE, and RPD values of 0.75, 0.082, and 1.98, respectively. (2) Urban form exhibits nonlinear threshold effects on the carbon-pollution coordination degree. The top predictors contributing to the model output are the class area (CA), the landscape shape index (LSI), the percentage of like adjacencies (PLADJ), and the number of patches (NP). Among them, CA exhibits a monotonically increasing asymptotic saturation response, while the LSI presents an inverted U-shaped response. (3) The contribution of urban form to the CCD exhibits significant spatial heterogeneity. The developed regions of eastern China constitute the high-sensitivity zone of the CCD, and are mainly constrained by scale expansion, land fragmentation, and excessive agglomeration, while the central and western regions show the low-sensitivity zone of the CCD. These results offer a scientific reference for designing pollution control and carbon mitigation strategies. Full article

Parallel-inverter microgrids are prone to PCC voltage distortion during islanded operation with nonlinear and unbalanced loads. Virtual-impedance methods can reshape inverter output impedance, but they also add control complexity and may introduce extra voltage drops. This paper proposes a droop-based PI-QPR control strategy to improve PCC voltage quality in islanded parallel-inverter microgrids. The droop scheme generates the fundamental voltage and frequency references, and the PI-QPR voltage outer loop regulates the fundamental, negative-sequence, and dominant low-order harmonic voltage components in the dq synchronous reference frame. The PI regulator is used for the fundamental component, while QPR branches at 2ω₀ and 6ω₀ compensate the negative-sequence component and the dominant fifth- and seventh-order harmonics. No additional virtual-impedance loop is introduced. Two-inverter hardware-in-the-loop (HIL) tests were conducted under nonlinear and unbalanced load conditions. Compared with the traditional voltage controller, the proposed controller reduces the measured three-phase PCC-voltage THD from 5.79–6.02% to 2.41–2.79%, confirming improved PCC voltage quality in the tested islanded condition. Full article

Inverted perovskite solar cells (PSCs), or p-i-n PSCs, have become increasingly attractive for high-performance perovskite photovoltaics owing to their low-temperature processability, reduced hysteresis, flexible-substrate compatibility and suitability for perovskite/silicon tandem architectures. The buried interface is central to charge extraction, energy-level alignment, perovskite crystallization and operational stability, and is therefore a key determinant of device performance. Self-assembled monolayers (SAMs) are molecularly thin and offer negligible parasitic absorption, tunable interfacial energetics, low material loading and high structural designability, making them attractive alternatives to conventional organic Hole Transport Layers and effective hole-selective contacts in inverted PSCs. This review examines molecular design principles and interfacial engineering strategies for SAMs in inverted PSCs, focusing on the phosphonic acid carbazole (PACz) family, substituent and terminal-group engineering, and emerging conjugated backbones. We then summarize how SAMs regulate buried interfaces through energy-level alignment, defect passivation, crystallization control and stability enhancement. We further highlight emerging interface strategies, including co-assembled SAMs, amorphous SAMs, polymerized or crosslinked SAMs and molecular hybrid interfaces, and discuss how data-driven molecular screening may accelerate future SAM discovery. Finally, we discuss outstanding challenges in SAM formation, large-area uniformity, in situ and operando characterization, and data-driven molecular design, and provide perspectives on the use of SAMs in efficient, durable and scalable inverted PSCs. Full article

In this study, the hardware design, manufacturing, and control of a Two-Wheeled Inverted Pendulum Manipulator (TWIPM) are successfully achieved. The system comprises a two-degree-of-freedom independently driven chassis integrated with a three-degree-of-freedom robotic manipulator. To enable the robot to navigate and reach designated target coordinates on inclined terrain, an autonomous trajectory planning scheme is implemented using the A* algorithm, and the system’s mathematical model is comprehensively updated. To ensure balance stability and enhance robustness against external perturbations, a PI-based supplementary control architecture is proposed to support the core PID controllers governing wheel angular position and chassis tilt. The efficacy of the proposed control strategy is initially validated via numerical simulations under various reference trajectories and disturbance inputs on flat surfaces. Subsequently, experimental validations conducted on a physical testbed featuring an inclined ramp demonstrate the robot’s autonomous trajectory tracking and precise trajectory tracking positioning capabilities, confirming its real-world viability. Finally, future research directions are outlined, focusing on end-effector position optimization, the integration of a dynamic payload estimator under varying weights, and the fully onboard execution of navigation algorithms on the central microcontroller. Full article

The model predictive current control (MPCC) of an interior permanent magnet synchronous machine (IPMSM) requires an accurate motor parameter model to predict future currents and achieve high control performance. However, the inductance parameters of an IPMSM are easily affected by factors such as magnetic field saturation, leading to large current prediction errors, high current ripple, and poor stability. Therefore, an MPCC strategy for an IPMSM based on parameter adaptive feedback correction is proposed. First, based on the mathematical model of the IPMSM in the synchronous rotary coordinate, the cross-coupling relationship between the dq-axis inductance deviations and the current prediction error is derived to form an explicit prediction error model. Then, the influence of the d-axis and q-axis inductance parameter deviations of the IPMSM on the current prediction error is discussed in detail. Next, based on the established mathematical model of the prediction error, the recursive least squares scheme is adopted to identify the d-axis and q-axis deviations of the inductance parameters online. Finally, unlike conventional open-loop RLS correction, a PI-based closed-loop correction loop is designed that feeds the prediction error back to adjust the inductance deviations, thereby forcing the prediction error toward zero while inherently compensating for inverter dead-time effects. Simulations and experiments were conducted, and the results show that the proposed scheme greatly improves the accuracy of current prediction and inductance parameter estimation, and enhances robustness against parameter mismatch and dead-time disturbances. The key novelty lies in the PI-feedback-driven RLS closed-loop structure that simultaneously achieves error elimination and dead-time compensation. Full article

To alleviate the severe voltage security and operational efficiency challenges brought about by the increasing penetration of distributed energy resources in active distribution networks, Volt/Var control (VVC) has become a key mechanism to stabilize node voltage and minimize power loss by coordinating reactive power injection. While multi-agent reinforcement learning (MARL) offers a promising decentralized control approach, its static reward functions are prone to creating harsh trade-offs between voltage constraint enforcement and cost-efficiency. In this paper, a hierarchical autonomous control framework featuring large language model-driven dynamic reward shaping (LLM-Driven DRS) is introduced to balance security and efficiency. The dynamic priority shifting (DPS) mechanism lies at the center of the framework and dynamically varies the reward weights through the detection of real-time grid bottlenecks. Under the LLM-Driven DRS framework, this mechanism successfully achieves a fluid transition between a Constraint-Dominant Phase for voltage stabilization and an Objective-Refinement Phase for economic optimization. Validation on a modified IEEE 33-bus system demonstrates that the proposed framework achieves Pareto superiority over conventional static weight strategies. Crucially, compared with the 1.250% static baseline, the absolute voltage violation rate is suppressed to 0.014%, mitigating long-tail risks of hardware degradation and inverter tripping, while active power losses are reduced by up to 33.76%. A robust safety margin is further confirmed by spatiotemporal analysis, which reveals an average minimum voltage margin increase of over 0.011 p.u. under severe stress conditions. Full article

In distribution networks with a high resistance-to-reactance (R/X) ratio, grid-forming (GFM) inverters can adopt reverse droop control (P-V, Q-f) to achieve the decoupling of active and reactive power. When grid voltage sags trigger the overcurrent protection of the inverter, the interaction between the circular current limiter and the embedded virtual impedance leads to highly complex nonlinear large-signal dynamics. Reverse droop control drives the system power angle via reactive power, which renders the conventional transient stability analysis method based on the P-δ curve invalid, making it difficult to analyze the transient stability of converters based on reverse droop control. To address these issues, this paper first establishes an equivalent circuit model of a GFM inverter considering the circular current limiter and virtual impedance. Second, a transient stability analysis method based on the Q-δ curve is proposed, and the conditions for the existence of the system’s transient equilibrium point (TEP) and the influence of virtual impedance parameters on it are analytically derived. Subsequently, a parameter tuning strategy based on Bayesian optimization (BO) is proposed. Finally, simulation results verify the accuracy of the proposed theory. Full article

The increasing integration of power electronic converters in hybrid AC/DC microgrids introduces significant challenges in maintaining DC-link voltage stability during mode transitions, where uncoordinated actions cause large voltage deviations. This paper proposes a coordinated hierarchical control strategy incorporating a supervisory finite state machine (FSM) and a slew-rate-limited reference shaping mechanism to ensure smooth transitions in a microgrid interfaced through a bidirectional DC–DC converter and a three-level T-type inverter. The supervisory layer coordinates the sequencing of subsystem activation and routes all mode changes through a dedicated transition state in which the power reference is gradually shaped to suppress DC-link disturbances, while a dedicated resynchronization state manages reconnection to the grid after a sustained outage. The strategy is validated through detailed switching-level simulations across five operating scenarios, including islanded load energization, grid blackout, discharging-to-charging transitions, state-of-charge limit management, and grid restoration through reclosing and resynchronization, and is further compared against a droop-based coordination scheme. Simulation results demonstrate that the proposed approach reduces the transient DC-link voltage deviation from approximately 18–20% to below 7%, and to as low as 2.6%, without introducing steady-state error, confirming its effectiveness in enhancing the dynamic stability of the system during mode transitions. Full article

Grid-connected photovoltaic (PV) systems require low-voltage ride-through (LVRT) to function reliably, particularly in the presence of symmetrical and asymmetric disturbances. Conventional PI-based control systems occasionally show limited resilience, particularly in the presence of distorted or imbalanced grid voltage. This paper proposes an enhanced LVRT control strategy for three-phase grid-connected PV systems by integrating a new rapid indirect Global Peak-Oriented Adaptive P&O MPPT method, referred to as (GPOA-P&O), with LADRC and DSOGI-FLL synchronization. The GPOA-P&O algorithm improves maximum power tracking by identifying the global peak and avoiding local maximum points, thereby reducing power fluctuations. Meanwhile, the cascaded LADRC controllers provide accurate voltage and current regulation, effectively suppressing DC-link overvoltage during grid disturbances. DSOGI-FLL ensures accurate positive-sequence phase-locking, enabling compliant reactive current injection even under severe voltage asymmetry, in accordance with grid-code requirements. The proposed method also eliminates second-order power oscillations and maintains constant inverter current regardless of fault severity. Case studies in 2024a MATLAB/Simulink and hardware-in-the-loop experimental platform demonstrate superior stability, fault ride-through capability, and grid-support performance compared to conventional approaches such as PI control and optimized SCSO-tuned PI. Full article

The cost and output voltage quality of multilevel inverters are among the most critical design considerations. Consequently, reducing the number of power switches and DC sources while improving output voltage quality plays a crucial role in achieving cost-effective designs. This paper proposes a new multilevel inverter topology capable of generating 17 voltage levels using a single DC source and only 12 power switches. A comprehensive comparison demonstrates the superior cost effectiveness of the proposed topology compared to existing counterparts. Moreover, modulation of reduced-switch multilevel inverters remains a challenge when conventional PWM techniques are employed, as they typically require complex logic circuits to generate appropriate switching patterns. To address this issue, this paper investigates the application of one-dimensional space vector modulation (OD-SVM) to control the proposed multilevel inverter without the need for any additional logic circuits. Simulation and experimental results validate the effectiveness of the proposed inverter topology and the OD-SVM control strategy. Full article

The escalating penetration of distributed photovoltaic (PV) systems has intensified grid-connected voltage violations, posing severe challenges to the stability of distribution networks. This paper first investigates the mechanisms of voltage violations at 35 kV substations and 380 V consumer-side terminals under high-penetration scenarios. It is demonstrated that PV integration elevates line voltage, with the voltage profile at any given node being governed by the equivalent net load—defined as the offset between total demand and PV generation—downstream of that node. Subsequently, the impacts of critical operating conditions, including PV penetration levels, line impedance, and dynamic meteorological variations, are quantitatively analyzed. Simulation results characterize voltage fluctuation patterns under diverse variables, such as varying PV outputs, line parameters, and interconnection points, thereby validating the theoretical derivation. Finally, an integrated management strategy, coupling coordinated reactor compensation with voltage-source inverter (VSI) control, is proposed. Simulation results across multi-dimensional complex scenarios verify the effectiveness of the proposed strategy in suppressing voltage violations and enhancing grid resilience. Full article