Search Results (206)

A torque-preserving flux-weakening control strategy combining q-axis current compensation with a bandwidth-based speed-adaptive voltage regulator is proposed for interior permanent magnet synchronous motor (IPMSM) drives. The conventional negative d-axis current compensation method is first analyzed, showing that the associated current-vector variation can cause transient torque deviation during flux-weakening operation. A q-axis current compensation law is therefore derived based on the torque-preservation condition. In addition, a speed-dependent tuning law for the voltage closed-loop regulator is developed through frequency-domain analysis, with the voltage-loop bandwidth as the principal design parameter. Experimental results show that, compared with the conventional method, the proposed strategy reduces the torque-fluctuation amplitude from 2.35 N·m to 1.83 N·m, corresponding to a reduction of approximately 22.1%, and suppresses the approximately 9% q-axis current overshoot observed with the conventional method. Under a sudden-load condition, the maximum speed dip is reduced from 66 r/min to 61 r/min (7.6%), while the recovery time is shortened from 0.28 s to 0.25 s (10.7%). These results demonstrate improved transient torque stability and disturbance-rejection performance in the flux-weakening region. Full article

On-board three-phase two-level uninterruptible power supply systems serve as vital energy interfaces, ensuring high-fidelity power distribution for critical payloads in heavy-duty unmanned aerial vehicles. Therefore, this paper introduces a robust current-sensorless discrete-time sliding-mode control (DSMC) strategy in the stationary $\alpha \beta$ frame to simplify the system structure while maintaining high-quality dynamic voltage performance. A discrete-time extended-state observer (DESO) is implemented to precisely estimate the filter capacitor current, effectively addressing the voltage regulation issues stemming from load fluctuations and the absence of sensors. Furthermore, the DESO-based current estimate is incorporated as feedforward compensation into the DSMC architecture to significantly bolster the disturbance rejection and fault-tolerance capabilities of system. The simulation results verify that the proposed method outperforms typical cascaded proportional–resonant control, delivering superior voltage tracking accuracy and robust performance. Specifically, compared to the typical cascaded strategy, the proposed method reduces the steady-state RMS voltage tracking error by approximately 1.5 V across all load types, and decreases the THD by 0.08% under balanced loads and 0.15% under nonlinear loads. Full article

The rapid electrification of marine transportation has increased the number of hybrid marine microgrids with the addition of renewables and energy storage. The continuously varying propulsion loads, fluctuating sea states, and renewable intermittency introduce significant challenges in bidirectional power transfer and power quality enhancement in marine vessels. This work presents a power-oriented operational strategy for a hybrid Roll-on/Roll-off (Ro-Ro) ferry-based marine microgrid (FMG) integrating diesel generators (DGs), Solar Photovoltaic (PV) arrays, and battery energy storage systems as the primary power sources. The proposed FMG adopts a hybrid AC/DC bus configuration linked through a bidirectional voltage source interlinking converter (ILC). The ILC facilitates multiple functionalities, including effective load compensation, mitigation of Total Harmonic Distortion (THD), continuous power support through bidirectional energy exchange, maintenance of balanced sinusoidal currents, and unity power factor (UPF) operation, thereby providing an integrated solution for improved power quality and reliable microgrid performance. A supervisory control (SC) is devised to operate the FMG seamlessly under islanded modes depending on the availability of power sources. To achieve the above-mentioned objectives, a power-optimized Dual Power-based Instantaneous Power Theory (DP_IPT) is employed and it involves a Sequential Delay Signal Cancelation (SDSC)-based Phase-Locked Loop (PLL) for the effective extraction of sequence components, so as to address the unbalance and nonlinearities in an effective manner with reduced oscillations. The proposed control strategy reduces diesel generator utilization through the effective integration of Solar PV and battery support during anchoring operation. The integration of renewable energy sources substantially enhances clean energy utilization, resulting in the reduction of overall carbon emissions, accounting for a near-40% decrease in emissions compared with the conventional diesel generator (DG)-based operating mode. The proposed FMG and control framework are validated through the Hardware-in-the-Loop (HiL) approach employing an OPAL-RT (OP4512) real-time controller. The HiL investigations demonstrate the efficacious working of the proposed control in achieving less carbonized and enhanced power quality operation for next-generation electrified hybrid maritime microgrids. Full article

To mitigate oscillatory instability caused by pulsed-load impact currents in diesel-generator-based medium-voltage direct current (MVDC) integrated power systems, an adaptive virtual synchronous generator (AVSG)-based model predictive control (MPC) strategy is proposed. A mathematical model of the pulsed load and its power-supply circuit is established based on the MVDC system architecture, and the overall transfer function from the load side to the source side is derived. On this basis, the relationship between the pulsed-load impact currents and diesel-generator speed fluctuation is clarified, and the coupling between the disturbance frequency and the generator’s inherent frequency is revealed. In addition, the active compensation mechanism of a supercapacitor–lithium-battery hybrid energy storage system is analyzed. An AVSG control strategy suitable for MVDC systems is then developed, and adaptive tuning laws for the virtual inertia and damping coefficients are designed. MPC is incorporated into the current inner loop of the hybrid energy storage system to improve the dynamic response. Hardware-in-the-loop results obtained on the RT Box 3 platform verify the effectiveness of the proposed 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

The permanent magnet synchronous linear motor (PMSLM) is a key technology for the ultra-high-speed acceleration in maglev transport systems over short distances. It has attracted significant research interest owing to its high power density, high efficiency, and excellent control performance. Nevertheless, the design of such motors faces several challenges. These include the accurate calculation of inductance parameters and the achievement of high thrust force density. To overcome these issues, this study first derives analytical expressions for per-unit-length inductance and thrust force. Based on these, key electromagnetic parameters and structural parameters of the motor are designed. A segmented design scheme is also proposed. A finite element model of a bilateral long-stator PMSLM is then established using Ansys Maxwell. Simulations are performed to analyze the motor’s back electromotive force (EMF), electromagnetic thrust force, inductance distribution, and induced voltage. The results show a good agreement between the simulation and theory. The error in inductance calculations ranges from −5.5% to +6.65%. The absolute error between the calculated and simulated thrust force values is below 0.8 kN. Furthermore, the non-uniformity in inductance distribution and the causes of thrust force fluctuation are investigated. Odd-order harmonics, such as the third and fifth, are identified in the induced voltage. This research offers a design methodology and simulation verification for ultra-high-speed PMSLMs. It lays a foundation for the future development of end-effect compensation and harmonic suppression strategies. Full article

Stator winding reconfiguration technology has attracted increasing attention because it can modify the torque–speed output characteristics of motors online and extend the high-efficiency operating region. However, conventional winding switching methods suffer from several limitations, including long transient duration, typically at the millisecond level; difficulty in precise control; current interruption or asymmetric operation during the transient process; and the resulting torque loss and torque fluctuation. To address these issues, this paper first proposes a seamless winding switching method. The core idea is to complete the switching within the zero-vector interval of a single SVPWM period, thereby eliminating potential surge voltage without requiring a snubber circuit. The proposed method reduces the transient duration to only 5 μs, eliminates current interruption and current asymmetry, and suppresses the associated torque ripple. Furthermore, a deadbeat predictive control strategy is employed. By directly controlling the voltage vector, the proposed strategy enables fast and accurate current tracking within one sampling period after reconfiguration, thereby avoiding current overshoot, oscillation, and the corresponding torque and speed fluctuations. In addition, a voltage feedforward compensation method is proposed to pre-compensate the voltage applied during the PWM period in which the winding reconfiguration is performed, thereby preventing the application of voltage vectors that are inconsistent with the actual motor winding connection. With these three innovative measures, fast, smooth, and robust winding reconfiguration is achieved. The mechanisms and implementation procedures of the proposed strategies are described in detail, and their feasibility and effectiveness are verified through experiments. Full article

Rural distribution networks increasingly face voltage quality challenges due to high penetration of distributed renewable energy, heterogeneous rural load behavior, and long radial feeder structures with limited voltage regulation capability. Photovoltaic generation variability and agricultural load fluctuations can lead to voltage rise, reverse power flow, and branch congestion, particularly in weak rural grids. Conventional deterministic voltage control approaches relying on tap changers and capacitor banks often struggle to maintain stable voltage profiles under stochastic operating conditions. This paper proposes a risk-aware coordinated operation framework for rural multi-energy microgrids that integrates stochastic scenario modeling, voltage state perception, and adaptive optimization-based control. Renewable generation uncertainty and rural load variability are represented through correlated scenario generation and Wasserstein-distance-based scenario reduction, where 100 raw joint photovoltaic-load trajectories are reduced to 20 representative scenarios after convergence and distributional-fidelity tests. A stochastic optimization model is developed to coordinate photovoltaic inverters, battery energy storage systems, demand-side flexibility, and reactive compensation devices while satisfying network power-flow, voltage-security, storage, and communication-delay-aware implementation constraints. To mitigate extreme voltage deviation events, the framework incorporates a Conditional Value-at-Risk formulation that penalizes tail-risk voltage violations and maintains voltages within a preferred operating band of $0.97$–$1.03$ p.u. Case studies on a modified IEEE 33-bus rural distribution system with $2.00$ MW of photovoltaic capacity and $2.50$ MWh of battery storage demonstrate consistent performance improvements across deterministic, risk-neutral stochastic, chance-constrained, and robust baselines. The proposed strategy reduces peak branch loading from $0.95$ in the deterministic benchmark to $0.72$, while the 95th percentile voltage deviation risk decreases from 0.0071 p.u.² to 0.0020 p.u.². Sensitivity, scenario-convergence, scalability, and seasonal representative-day analyses further confirm that the CVaR layer suppresses rare but severe voltage excursions without imposing excessive curtailment or computational burden. Full article

Shipboard DC microgrids face critical stability challenges including low-inertia-induced voltage fluctuations and impedance mismatch caused by constant power loads (CPLs), which severely threaten system stability. Existing virtual DC machine (VDCM) control methods typically treat inertia support and impedance optimization as separate design objectives, lacking a unified frequency-domain design framework. To address this issue, this paper first establishes an accurate virtual impedance model for the standard VDCM controller, quantitatively revealing how its control parameters (J and D) shape the frequency-domain impedance characteristics and identifying potential stability conflicts. Building upon this model, a feedforward-compensated VDCM (FFC-VDCM) strategy is proposed, introducing a differential feedforward loop to actively reshape the converter output impedance in the critical mid-frequency range without interfering with the inertia support function. The impedance reshaping effect is quantified via impedance-based stability analysis; the proposed method improves the gain margin from $4.1$ dB (with conventional VDCM) to $8.6$ dB, along with a significant enhancement in the phase margin, confirming improved system robustness. Hardware-in-the-loop (HIL) experiments conducted under realistic shipboard conditions further confirm the theoretical analysis, demonstrating superior transient voltage regulation and validating the practical effectiveness of the proposed strategy. The FFC-VDCM provides a synergistic solution for concurrently improving inertia and stability in low-inertia DC microgrids. Full article

Wireless power transfer (WPT) systems are easily affected by input voltage variation, coupling variation, and load changes, resulting in output voltage fluctuation and long settling time. To improve the transient performance, this article proposes a discrete sliding mode control method with lumped disturbance estimation (LDE-DSMC) for an LCC–S compensated WPT system. Input voltage variation, mutual inductance variation, load step, and unmodeled dynamics are uniformly treated as a lumped disturbance in the output voltage channel. The estimated disturbance is introduced into the control law for feedforward compensation, and one-step prediction is used to reduce the influence of duty cycle update delay. A hardware prototype is built for verification. Compared with PI control and adaptive feedforward control, the proposed method achieves smaller output voltage deviation and shorter settling time under different disturbances. In the single disturbance tests, the maximum output voltage deviation is reduced by at least 50%, and the settling time is shortened by at least 33%. Under the compound disturbance, the maximum output voltage deviation is reduced by 62.50% and 36.36% compared with PI control and adaptive feedforward control, respectively, while the settling time is shortened by 64.49% and 39.68%. Full article

Continouous unmanned aerial vehicle (UAV) missions are fundamentally limited by Lithium-Polymer (LiPo) battery endurance under intermittent and power-constrained renewable energy conditions. This paper proposes an integrated energy management and charging framework for a photovoltaic (PV)-powered mobile station equipped with a hybrid energy storage system (HESS) and an automated battery replacement (ABR) mechanism. A lexicographic priority-based allocator sequentially serves ABR actuation, multi-slot LiPo charging, and Brushless DC (BLDC) propulsion, while the HESS compensates for PV intermittency. At the charging level, a constraint-aware constant current–constant voltage (CC–CV) strategy is enhanced by an adaptive neuro-fuzzy inference system (ANFIS) trained on optimization-derived labels using battery temperature and its rate of change, thus enabling anticipatory thermal current derating with smooth, discontinuity-free control action. Anti-windup proportional–integral (PI) regulation and bumpless mode transfer ensure stable CC-to-CV transitions. An event-triggered emergency mode accelerates battery readiness via a max-first selection policy. Comparative simulations against a PSO/DE-optimized PID benchmark over a full diurnal PV cycle demonstrate that the ANFIS controller reduces the CC-mode current tracking root-mean-square error (RMSE) by up to 96.9%, delivers higher charge throughput, and lowers battery degradation proxies, including SOC-weighted thermal dose and equivalent full cycles (EFC). The proposed framework reliably sustains continuous charge–swap–recharge logistics under fluctuating renewable generation. Full article

Direct grid-connected wireless charging based on direct AC–AC conversion is attractive for electric vehicles (EVs) because it can reduce power conversion stages and improve charger compactness. In matrix-converter-based wireless power transfer (WPT) systems, the grid-frequency AC voltage can be directly converted into high-frequency AC voltage without using bulky DC-link electrolytic capacitors. However, the removal of the intermediate energy-storage stage also makes the EV wireless charger more sensitive to grid-voltage fluctuation. For an LCC-S compensated WPT system, the voltage-source output characteristic makes the charging-side voltage sensitive to grid-voltage disturbance, resulting in severe MC output-current and battery charging-current overshoot. This transient overcurrent may threaten both the power converter and the EV battery charging process. In this paper, a dual-frequency state-space model is developed for the matrix-converter-based electrolytic-capacitor-less LCC-S WPT system to analyze the disturbance propagation from the grid side to the high-frequency resonant stage and the EV battery side. Based on the model, the current-overshoot suppression capability and bandwidth limitation of the conventional dual closed-loop control strategy are investigated. To further enhance transient current protection, a grid-voltage feedforward strategy is proposed to compensate for the disturbance before severe current overshoot is formed. Finally, experimental results verify that the proposed method effectively suppresses the MC output-current and battery charging-current overshoot under grid-voltage fluctuation, thereby improving the grid-disturbance resilience and dynamic safety of direct grid-connected EV wireless charging systems. Full article

Portable industrial X-ray flaw detectors operating in outdoor environments predominantly rely on small diesel generators for power supply. However, the inherent grid frequency drift of such weak grids induces critical phase-shift mismatches in conventional fixed-delay controllers, leading to voltage loss-of-control. This study aims to develop a robust, frequency-adaptive power drive system to overcome these operational challenges. A dynamic zero-crossing capture mechanism is proposed to extract real-time grid frequency variations, enabling instantaneous phase-shift feedforward compensation. This mechanism is integrated with an adaptive incremental proportional–integral–derivative (PID) controller that utilizes grid-condition recognition to dynamically schedule gains and neutralize frequency disturbances. Furthermore, a linear voltage soft-start strategy is incorporated to coordinate downstream constant-current regulation, preventing inrush currents. Concurrently, an offline downtime perception mechanism executes autonomous stepped-voltage conditioning to prevent cold high-voltage breakdowns. Simulation and hardware experimental results demonstrate that under continuous generator frequency drift, the adaptive control maintains a steady-state voltage error below 1%, suppresses the voltage ripple factor to 1.11%, and limits tube current fluctuations to 4.2%. The proposed system effectively mitigates weak-grid instability, ensuring reliable high-voltage generation and extending component lifespan for demanding non-destructive testing (NDT) applications. Full article

The inherent variability of wind power generation poses major challenges for maintaining voltage stability and power quality in modern distribution networks. Conventional rule-based and optimisation-driven control strategies often fail to respond effectively to these rapid fluctuations. To address this limitation, this paper introduces an adaptive reinforcement learning (RL) framework that autonomously optimises reactive power compensation and on-load tap changer (OLTC) operations in real time. The proposed deep Q-network (DQN) agent learns optimal control policies through continuous interaction with the grid environment, minimising voltage deviations and network losses under dynamic wind conditions. Using the IEEE 33-bus distribution test system, the trained DQN achieved a substantial improvement in voltage regulation, reducing the average deviation from 0.041 p.u. (rule-based) to 0.014 p.u. and lowered power losses by 24.6/5 compared to traditional optimisation techniques such as Particle Swarm Optimisation (PSO) and static rule-based control. Furthermore, the DQN controller demonstrated the fastest learning convergence within 120 episodes, validating its potential for real-time adaptive voltage control. Overall, the study highlights RL as a promising, scalable solution for autonomous voltage regulation in smart grids integrated with renewables. Full article

To address DC-link voltage fluctuation, active-power imbalance between the machine side and the grid side, and double-frequency distortion in the grid current of a flywheel energy storage system (FESS) under symmetrical and asymmetrical voltage sag faults, this paper proposes a coordinated control strategy for the machine-side and grid-side converters to enhance low-voltage ride-through (LVRT) capability. Taking the DC-side energy imbalance as the coordination criterion, the machine-side converter adopts an online active-current-command reconstruction method based on cascaded limiting of DC-link voltage deviation. Under reactive-power-priority support and constrained active-power output on the grid side, the FESS can actively adjust its active-current command according to the DC-side energy state, thereby suppressing DC-link overvoltage/undervoltage and restoring the power balance between the machine side and the grid side. On the grid side, an improved linear active disturbance rejection control (LADRC) is introduced into the current inner loop. By optimizing the structure of the extended state observer, the observation and compensation capability for double-frequency disturbances is enhanced, thus improving grid-current quality under asymmetrical faults. In this way, power rebalancing between the machine side and the grid side, DC-link voltage stabilization, and grid-current disturbance suppression are incorporated into a unified coordinated control framework. Hardware-in-the-loop experimental results show that the proposed strategy can maintain DC-link voltage stability during both symmetrical and asymmetrical voltage sags, while keeping the maximum grid-current total harmonic distortion (THD) below 0.13%. Under asymmetrical voltage sag, the improved LADRC reduces the maximum interphase peak-current deviation from approximately 52 A under conventional PI control to 4.57 A, corresponding to a reduction of about 91.2%. These results indicate that the proposed strategy can effectively enhance DC-link voltage stabilization and improve grid-current quality during faults. Full article