Search Results (169)

Permanent-magnet synchronous motors enable precise motion control in compact robots, but their leakage fields can corrupt onboard magnetometer measurements. Physics-based compensation is effective under fixed geometric conditions, whereas quadruped locomotion continuously changes the motor–sensor relationship. We propose MagGAT, a structure-aware spatiotemporal graph attention network that estimates compensated magnetic field signals from motor states and near-field measurements. A boom-mounted far-field magnetometer provides a pseudo-reference for supervised training and field-level evaluation. MagGAT combines a global–local dual-branch graph attention module for multi-motor spatial coupling with a gated recurrent unit for temporal disturbance modeling. Experiments on a Unitree Go2 quadruped used synchronized near-field and far-field measurements, joint angles, angular velocities, and commanded torques collected in indoor and outdoor environments. Across three runs with different random seeds, MagGAT achieved mean residual three-axis magnetic field RMSE values of 87.72–89.41 nT across the three test sequences and outperformed a physics-based fixed-parameter model, a static neural network method, and a temporal convolutional baseline. Ablation studies confirmed that both spatial graph modeling and temporal modeling contributed to compensation accuracy. These results support structure-aware spatiotemporal learning for suppressing motor-induced magnetometer interference on compact legged robots. Full article

To improve voltage support at the point of common coupling of renewable energy collection stations connected to weak grids, this paper proposes a synchronous machine-like outer reference generator for a conventional fixed-PQ voltage-source converter (VSC). The proposed versatile static synchronous machine (VSSM) emulates the excitation and reactive power-voltage regulation of a synchronous generator, maps the resulting transient internal electromotive force to an exact reactive power reference, and applies converter capability and ramp rate limits with an equivalent Q-tracking response. A two-stage strategy further uses fast dynamic compensation to clamp voltage and slower static compensation to release bidirectional dynamic reserve. In the WSCC nine-bus benchmark, all controllers use the same 100 MVA VSC, +/−80 Mvar limit, 0.04 s reactive power inner loop, and 10 pu/s ramp limit. After a three-phase fault and line tripping, the minimum post-fault bus 8 voltage is 0.9452 pu with the VSSM, compared with 0.8755 pu for the calibrated PI-SVG and 0.7660 pu for fixed Q; Q-U droop gives 0.9492 pu but requires 0.33 s for sustained recovery above 0.95 pu, compared with 0.23 s for the VSSM. A positive-, negative-, and zero-sequence extension also evaluates a single-line-to-ground fault. Finally, an anonymized actual receiving-end grid model shows an approximately 40 ms improvement in voltage recovery and reduced steady-state loading of dynamic reactive sources. All results are obtained from offline simulations. Full article

A two-level closed-loop calibration framework is proposed to reduce odometry scale errors during motion and pose drift during stationary periods in Mecanum-wheeled mobile robots. At the upper calibration level, the planar displacement between the initial and final poses is calculated using the L2-norm, which reduces the influence of lateral deviation on distance measurements based on a single coordinate axis. Rotational displacement is obtained by accumulating normalized angular increments, thereby avoiding discontinuities when the yaw angle crosses the ±π boundary. A relay controller with a tolerance deadband is also introduced to reduce static-friction-induced stalling and oscillation near the target during low-speed calibration. At the lower odometry interface, the covariance assigned to wheel odometry measurements is adjusted according to the commanded zero-velocity state. During stationary periods, this adjustment increases the contribution of near-zero velocity measurements and limits the effect of residual velocity estimates and sensor noise on the fused pose. The identified longitudinal and rotational compensation factors are then updated online in the dead-reckoning node through an ROS 2 service. Unlike conventional ZUPT implementations, the proposed method does not require an additional zero-velocity pseudo-measurement node. Experiments were conducted on three near-horizontal surfaces: ceramic tile, epoxy resin, and asphalt. Across 720 bidirectional in-place rotation trials, the angular Error Reduction Rate ranged from (59.13%) to (96.58%). In 540 straight-line trials covering nine combinations of surface type and target distance, the overall mean absolute error decreased from 53.22 mm before calibration to 9.69 mm after calibration. Intermittent stop-and-go experiments were further performed using the EKF, UKF, RCKF, and a graph-based SLAM optimization framework implemented by slam_toolbox. For each estimation back-end, the estimated trajectory was evaluated by calculating its deviation from the corresponding synchronized /odom trajectory under the fixed-covariance and proposed ZUPT-based adaptive-covariance configurations; /odom was used as a common comparison baseline rather than as an absolute localization ground truth. The adaptive covariance strategy reduced the positional RMSE by (19.38%–67.44%) across the evaluated filtering back-ends. These results show that the proposed framework can reduce both motion-dependent odometry scale errors and stationary pose drift under the tested surface conditions. Full article

With the increasing penetration of inverter-based resources (IBRs), maintaining converter-driven stability has become a critical challenge. Static synchronous compensators (STATCOMs) are widely deployed for voltage regulation through rapid injection or absorption of reactive power, making their capability crucial in IBR-dominated systems. However, harmonic resonance between STATCOMs and the grid is a critical concern, since interactions between converter control dynamics and grid impedance can span from sub-synchronous to harmonic frequencies. Most existing impedance-based studies focus on grid-following inverters and seldom capture the combined influence of communication delay, current-controller gain, and grid impedance; they do not address passive-filter-based mitigation. This paper examines the converter-driven stability of a grid-connected STATCOM using impedance-based small-signal analysis, considering inner and outer control loops, communication delay, and grid impedance. Using a modified IEEE nine-bus system, we investigate resonance migration and stability sensitivity to control delay and the current-controller proportional gain, and evaluate a C-type passive filter that improves delay robustness by damping the dominant current-control-loop resonance. The framework is validated through nonlinear electromagnetic-transient (EMT) simulations in MATLAB/Simulink, corroborating the small-signal delay-stability margin within 19.7%. Full article

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

We propose an optimal and robust siting and ranking framework for energy storage systems (ESSs) and static synchronous compensators (STATCOMs) under 765 kV double-circuit N-2 contingencies in the Republic of Korea transmission lines. Each N-2 contingency is constructed by pairing two parallel circuits that share the same 765 kV sending and receiving substations, so the contingency set is enumerated directly from the network topology. The framework screens 765 kV candidate buses at a fixed reference capacity, and it sizes ESS and STATCOM supports through independent active- and reactive-power capacity sweeps of repeated static post-contingency AC power flows. Then, it ranks candidates by a rank-aggregated robust score that combines scenario-averaged severity, scenario-averaged improvement, and evaluation reliability. Each sweep exercises only the non-negative support direction of its resource, namely ESS discharge and capacitive STATCOM operation, which is stated as an explicit modeling assumption. Here, robust means averaged over the multi-scenario set of the study year, load level, planning condition, and HVDC state rather than the worst-case in the min–max sense. The framework shows that the bus, which performs best on individual contingency pairs, does not coincide with the bus that is robust across scenarios, and it separately identifies the most frequent worst pair and the most difficult pair without relying on substation names. It therefore recommends the scenario-robust bus rather than the single-pair winner, orders candidates by the rank-aggregated robust score, and gives a STATCOM-leaning ESS–STATCOM mix at the top of the ranking under a transparent cost proxy, weight, cost-ratio, and coverage assumption. Therefore, the recommendation stays reproducible under alternative planning inputs. Full article

The doubly fed induction generator (DFIG) dominates the wind energy market, yet its direct stator-to-grid connection makes it vulnerable to grid faults, creating a tension between hardware self-protection and grid-code fault ride-through (FRT) compliance. This paper presents the modelling and FRT analysis of a 9 MW DFIG wind farm combining a 20 MVA Static Synchronous Compensator (STATCOM) with a ten-tier algorithmic protection scheme. A detailed phasor-domain MATLAB/Simulink R2024b model is complemented by physics-based reduced-order models integrated in Python, separating calibration targets, calibration-dependent derived quantities and quantities independent of the DC-link calibration. The aerodynamic model reproduces the power coefficient maximum of 0.48 at a tip–speed ratio of 8.1. The energy-balance model uses two parameters identified per scenario from the detailed DC-link trajectory; its peak-voltage agreement within 0.4% is therefore a calibrated consistency check, while the derived arming times, slopes, chopper sizing and latency budget remain conditional on that calibration. A first-order Thevenin analysis shows that the STATCOM supports a weak 25 kV point of common coupling of order 53 MVA short-circuit level, not the 2500 MVA source. The approximate 0.50-to-0.78 p.u. recovery requires about 29.7 M_var and 1.90 p.u. of STATCOM rated current for 150 ms, conditional on an assumed short-time envelope and adequate converter-voltage headroom; it is not attributable to continuous rated operation. FRT support for the selected recoverable dip is separated from converter survival during a zero-impedance fault, for which a 1700 V chopper pickup with a 1 ms gate delay, not the 10 ms isolation command, is the clamping mechanism. The assessment is explicitly conditional and requires electromagnetic-transient and hardware-in-the-loop confirmation. Full article

The energy transition is leading to increased loading of high-voltage distribution grids (HVDGs), which in turn results in higher active power losses. In addition, the meshed network structure typical for German 110 kV grids enables transit power flows originating from the superimposed transmission grid (TG). These transit power flows may further increase grid loading and active power losses. This paper presents a sensitivity-based mixed-integer quadratic programming (MIQP) approach for active power loss minimization in meshed HVDGs. The proposed methodology achieves near-real-time computation times while maintaining high accuracy by means of a piecewise linearized alternating current (AC) formulation. In addition, losses of static synchronous compensators (STATCOMs) and transformer-reactance variations are explicitly modeled. Reactive power provision by distributed energy resources (DERs) and STATCOMs, as well as discrete tap positions of power transformers (PTs) and phase-shifting transformers (PSTs), are considered as control variables. The proposed approach is validated using hourly snapshots of a real German HVDG provided by a distribution system operator (DSO). The results demonstrate a significant reduction in active power losses together with computation times suitable for near-real-time applications. Full article

Following the integrated optical assembly and single printed circuit board co-layout design concept for electrical circuits, this paper develops a field-programmable gate array (FPGA) based, miniaturized, eight-channel microwave photonic transceiver stabilization system for the joint regulation of lasers and Mach–Zehnder modulators (MZMs). The integrated single-board hardware enables high-precision, high-reliability automatic temperature control (ATC), automatic power control (APC), and arbitrary closed-loop control of the MZMs bias point, overcoming the drawbacks of discrete single-channel, independent control schemes reported in previous works, which lack expandability for large radar arrays. The laser sub-module supports continuously adjustable drive current and multi-level protection, achieving wavelength stability of 0.01 nm and an output optical power fluctuation of less than 0.02%. The MZM control unit delivers wide-range, high-stability bias drift suppression with arbitrary bias point stability up to 0.05 dB. All static and dynamic performance indicators of the proposed module are characterized using a dedicated experimental setup comprising optical power meters, optical spectrum analyzers, temperature cycling chambers, and vector signal analyzers. Leveraging FPGA-based parallel hardware logic, the system features low latency, low jitter, cross-channel mismatch compensation, and excellent timing synchronization, with a compact overall footprint of 180 mm × 120 mm that matches the size of radar antenna panels and supports flexible array scaling. The proposed integrated module meets the low-noise, high-reliability, and high-integration requirements of radio-over-fiber links in microwave photonic radars. It effectively advances the practical engineering deployment of microwave photonic radar systems. Full article

An increase in penetration of photovoltaic (PV) systems in a distribution system causes voltage regulation issues that create serious problems for the On-Load Tap Changer (OLTC) of the power transformer, leading to higher tap-changing frequency and reduced transformer life. Traditional voltage control methods are ineffective when PV penetration exceeds load demand, and more sophisticated control methods are needed. This paper combines a systematic literature review conducted in accordance with the PRISMA 2020 guidelines with a case study on operational issues of OLTC transformers under both normal and non-normal operating conditions. It entails a detailed examination of the effect of PV integration on the operating characteristics of OLTC in a systematic approach and also dwells upon coordination processes between OLTC and Flexible AC Transmission Systems (FACTS) devices, such as Distribution Static Synchronous Compensator (D-STATCOM) or Static VAR Compensator (SVC), which are highly effective in reducing tap operations. The future directions covered in the review include the operation of hybrid systems, cost-effective implementations, weather effects, predictive analytics, adaptive control techniques, etc. The case study included online monitoring of OLTC performance in two scenarios at the cement factory. First, under supply changes and load changes. Second, including PV penetration. The results show that OLTC increases the average daily tapping frequency (90 taps/day) by about 60%, with full PV penetration. It is concluded that this can’t be applied without coordinated control among OLTC, D-STATCOM, and PV inverters to maintain transformer life, improve reliability, and provide stable voltage profiles even under highly variable PV generation conditions. These results aim to provide a comprehensive resource for academics and practitioners, facilitating the advancement of advanced voltage control methods to support the transition to sustainable energy systems. Full article

The conventional model predictive control (MPC) experiences a tremendous number of switching state evaluations per control cycle when applied to multilevel converters, which makes it computationally impractical. To address this issue, this article proposes a computationally efficient MPC (EMPC) for the cascaded H-bridge (CHB) static synchronous compensator (STATCOM), which is enabled by the sorting of the H-bridge submodules upon their dc capacitor voltages, such that the candidate switching states are restricted to the scope in which the lower-voltage submodules are charged and the higher-voltage submodules are discharged. And therefore, the exponentially increasing switching states in the CHB-STATCOM can be dramatically reduced while the computational efficiency is greatly improved. In addition, prior to control implementation, a generic discrete-time prediction model with the incorporation of a zero-sequence component is established to merge the balanced and unbalanced scenarios into one framework, so as to address the issues related to either grid and/or load unbalances in the CHB-STATCOM for distribution grids. Both simulation and hardware-in-loop experimental studies are provided to verify the effectiveness of the EMPC strategy. Full article

This study investigates the coordinated impact of a synchronous condenser (SC), battery energy storage system (BESS), and static synchronous compensator (STATCOM) on enhancing voltage and frequency stability in a modified IEEE 9-bus power system under severe disturbances. The aim is to quantify the individual and combined contributions of these technologies during both fault ride-through (FRT) and load-increment events. The methodology includes dynamic modelling of all three devices in DIgSILENT PowerFactory. The SC is represented as a synchronous machine with inertia and AVR-based voltage control; the BESS employs converter-based active power and frequency-droop control; and the STATCOM provides fast reactive power injection through a dual-loop voltage regulator. Key indicators include nadir (minimum frequency), Rate of Change of Frequency (RoCoF), steady-state deviation, voltage sag depth, and recovery characteristics. Results indicate distinct roles for each device. The SC increases inertia and improves damping, but it also introduces small, well-damped oscillations. The BESS significantly enhances frequency stability by mitigating nadir, reducing RoCoF, and accelerating recovery, with negligible effect on voltage regulation. The STATCOM substantially reduces voltage sag and speeds up voltage recovery, but it does not influence frequency behaviour. When combined, the hybrid SC–BESS–STATCOM system demonstrates strong complementarity: the SC supports inertia, the BESS stabilizes active-power imbalance, and the STATCOM ensures fast reactive-power compensation. Full article

High levels of photovoltaic penetration and synchronous generator decommissioning are weakening grid strength and increasing voltage support requirements, yet most studies still assess support technologies primarily based on technical performance rather than full lifecycle utility value. The key gap is the absence of a consistent framework that links technical performance to lifecycle cost, tariff impact and investment outcomes across competing technologies. This study addresses that gap by developing a transparent utility-oriented assessment framework to compare Static Var Compensator (SVC), Static Synchronous Compensator (STATCOM), Synchronous Condenser (SC) and grid-forming BESS (BESS-GFM) options in a weak high-PV penetration network. Quasi-dynamic simulations on an IEEE 9-bus system were used to quantify technical benefits, which were then converted into lifecycle financial metrics within a total expenditure (TOTEX)-based model and combined with practical decision criteria through multi-criteria decision analysis (MCDA). The results show that while all four technologies improve system performance, their overall value differs once cost, tariff impact, risk and flexibility are considered. Under the adopted assumptions, STATCOM provides the best overall balance and ranks highest. Full article

This paper presents an absolute distance measurement system based on three-wavelength synchronous phase-shifting interferometry. A synthetic wavelength chain is established using three semiconductor lasers in an all-fiber Fizeau interferometer. By integrating a piezoelectric transducer (PZT)-driven sinusoidal phase modulation with multi-channel synchronous sampling for phase demodulation, and further combining it with a fractional multiplication method, the proposed system achieves high-precision absolute distance measurement over an extended range. Experimental results demonstrate an unambiguous measurement range of 240 μm, a static measurement precision better than 0.6 nm, and a dynamic displacement measurement accuracy superior to 2 nm in comparison with the reference device. The main error sources of the system, including synthetic wavelength uncertainty, phase measurement uncertainty, and air refractive index uncertainty, are systematically modeled and analyzed. In addition, the influence of dynamic factors, such as PZT nonlinearity, is discussed and compensated. The proposed method provides a robust and high-precision solution for absolute ranging and shows strong potential for applications in industrial precision inspection and optical sensing. Full article

Commutation failures (CFs), which occur when current transfer between valves in line-commutated converter high-voltage direct current (LCC-HVDC) systems is disrupted, pose a challenge in weak alternating current (AC) networks. This paper introduces a coordinated control strategy that combines a fuzzy self-tuning proportional-integral (PI) controller (FSTPIC) and a static synchronous compensator (STATCOM) device to mitigate CFs and enhance system stability. The approach applies the FSTPIC to both converters of the HVDC link, while the STATCOM at the inverter side delivers dynamic reactive power and voltage support during AC faults. We test this strategy on the CIGRE HVDC benchmark system using MATLAB/SIMULINK simulations. The results demonstrate that the proposed method significantly reduces CFs, mitigates transient oscillations, and shortens recovery time compared to conventional control techniques. This coordinated control boosts voltage stability and the system’s ability to ride through faults, confirming its superiority under various fault scenarios in weak-grid conditions. Full article