Search Results (1,211)

There is a growing need for high-efficiency power electronic converters that can effectively convert energy, regulate voltages, and enhance power quality in standalone power generators, as the use of renewable energy sources and battery energy storage devices increases. The quasi-impedance-source inverter (qZSI) has attracted significant interest due to its single-stage buck-boost operation, continuous input current, reduced reliance on passive elements, and increased reliability. In this paper, the control strategy and implementation of the qZSI with battery assistance for standalone photovoltaic energy generation are discussed. To analyze the operational characteristics and design the control strategy of the qZSI, the system equations are linearized around the nominal operating point to develop a small-signal model, from which the direct current (DC) side and alternative current (AC) side transfer functions are derived and used as the basis for controller design. Using the proposed model, hybrid controllers are designed to control the shoot-through duty cycle, maintain DC link voltage stability, and battery charging to achieve stable power generation. Furthermore, the SPWM technique is applied to produce AC power with minimal harmonic content and higher efficiency. Application results show stable dynamic behavior, effective battery energy management, improved voltage regulation, and reduced harmonic distortion in the output waveform. The main contribution is a low-complexity coordinated PI and PR control framework for standalone battery-assisted qZSI operation, experimentally validated under DC- and AC-side disturbances without requiring an additional battery-side power-conversion stage. Full article

With the rapid development of sustainable photovoltaic power generation, energy-storage-coordinated grid-connected photovoltaic systems have been widely adopted to stabilize power output and enhance grid adaptability. Aiming at the low fault tolerance of conventional photovoltaic grid-connected systems under grid voltage swell disturbances, this paper designs a single-stage power management system for grid-connected photovoltaic generation and studies its energy-storage-coordinated high-voltage ride-through (HVRT) technology. The single-stage topology boasts simple structure, low cost and high conversion efficiency, yet faces prominent stability risks under voltage swell faults. The system integrates photovoltaic units, energy storage modules and grid-connected interfaces to implement flexible bidirectional power dispatching. A three-phase AC/DC converter realizes photovoltaic maximum power point tracking (MPPT), and the energy storage module connects to the DC bus via a dual half-bridge (DHB) converter to restrain power fluctuations. Under HVRT faults, the energy storage coordination strategy elevates DC bus voltage to maintain stable grid-tied operation without disconnection. Different from schemes requiring extra hardware or complicated control optimization, the proposed method realizes stable bus voltage regulation and flexible energy scheduling with zero additional hardware cost. Simulations and experiments validate the rationality, feasibility and outstanding fault-ride-through performance of the designed system. Full article

Electric–hydrogen hybrid microgrids integrating distributed renewables with electrolysers can efficiently convert dispersed renewables into hydrogen, meeting local electricity demands. However, intermittent and uncertain renewables together with sudden load changes can cause severe bus voltage fluctuations and degrade power quality, especially in off-grid microgrids. Furthermore, the electrolyser’s auxiliary units require stable AC power supply even during fault events, which most likely occur at AC–DC converters. To ensure stability during renewable/load fluctuations and converter faults, this paper proposes a fault-resilient coordinated voltage control scheme by combining PI with piecewise active disturbance rejection control to mitigate DC bus voltage fluctuations during transient disturbances and regulates AC-side fuel cells via control switching to stabilise AC voltage after the complete disconnection converter fault. The scheme is tested using a simulated kW-scale electric–hydrogen hybrid microgrid in various operating scenarios and compared with conventional methods that combine PI with PI or linear active disturbance rejection control. The simulation results show that the proposed control scheme improves DC bus voltage stability by 14% during transient renewable/load fluctuations via the incorporation of PADRC and enhance system resilience against AC–DC converter faults through the synergy of batteries and fuel cells, which construct the voltage (and frequency) of DC and AC buses, respectively. Full article

Conventional quasi-steady-state models treat a self-adaptive STATCOM and line-commutated converter (SLCC) station as an LCC with an external reactive-power source, which cannot fully represent valve-side coupling. This paper develops a three-phase stationary-frame differential model for the SLCC and derives quasi-steady-state expressions for the average DC voltage and fundamental displacement angle. The non-commutation equivalent voltage is decomposed into fundamental and nonfundamental components. The fundamental component is retained in the power-flow model, while a control-informed harmonic extension evaluates the corresponding average DC-voltage correction over the tested operating domain. A positive-sequence fundamental-frequency formulation calculates the commutation overlap angle, and a first-zero diagnostic identifies control-sensitive conditions associated with the fast SVG voltage response. When the fast commutation-direction voltage reaches zero or reverses before current transfer is completed, a control-equivalent effective-area formulation provides an alternative low-order representation. The station equations are incorporated into a sequential AC/DC power-flow algorithm and validated against the engineering PSCAD/EMTDC main-circuit and control model of the Yangzhou–Zhenjiang HVDC Phase II project. Across the stable tested operating points, the phase-aware EMT-derived harmonic DC-voltage correction ranges from 0.585% to 1.245%, remaining below the adopted 2% screening threshold. The control-informed estimate follows the EMT-derived correction, whereas the phase-independent conservative bound reaches 2.128% at high controller gain. Across eight cases with available PSCAD reference values, the control-equivalent formulation reduces the mean and maximum overlap-angle errors from $0.90°$ and $1.37°$ to $0.78°$ and $1.09°$. For the benchmark power-flow cases, the maximum relative errors are 1.3% for the SLCC bridge reactive power and 1.0% for the SVG reactive-power output, and the calculation converges without sustained oscillation. A representative operating-point calculation is completed in approximately 3 s with the quasi-steady-state (QSS) formulation, compared with about 15 min for the engineering EMT benchmark. Full article

This paper presents the design, simulation, and experimental validation of an Active Compensation System (ACS) intended for bidirectional energy exchange between the utility grid and a battery energy storage system. The proposed architecture combines a bridgeless totem-pole power factor correction converter BLTP-PFC and a bidirectional CLLLC resonant DC/DC converter. A comparative evaluation of different converter topologies is performed considering efficiency, bidirectional operation capability, implementation complexity, and suitability for active compensation applications. Simulation and laboratory measurements verify operation in both charging and discharging modes. Experimental results demonstrate a maximum output power of 2.18 kW, power factor close to unity, current THD of 1.43%, and system efficiency exceeding 96%. The results confirm the suitability of the proposed topology for future smart-grid, renewable-energy, and battery-energy-storage applications. Full article

Power-electronic converter control is a key issue in the weak-grid integration of doubly fed induction generator (DFIG)-based offshore wind farms. In conventional fixed-reference DFIG control, the rotor-side power command is usually treated as a tracking target, although its suitability may change with the present point of common coupling (PCC) voltage and phase-angle condition. This paper proposes a weak-grid dynamic sensitivity-based model reference governor (WG-DSMRG) for DFIG offshore wind-farm converter control. The governor is inserted upstream of the RSC power-reference path, while the conventional RSC/GSC current controllers, phase-locked loop (PLL), coordinate transformations, and modulation structure are retained. The short-horizon relation between wind-farm power variation and PCC voltage-angle response is estimated from measured electrical signals. The RSC power command is then corrected through weak-grid scheduling and converter-capability projection. A 60-MW offshore DFIG wind farm connected to a weak AC grid is tested under an upstream voltage sag and a PCC single-line-to-ground fault. In the tested cases, the PCC reactive-power peak decreases from about 3.5 Mvar to 2.5 Mvar, and the DC-link voltage peak is reduced under both disturbances. The evaluated PCC voltage and current THD values are also lower with the proposed controller. These results show that reference-layer correction can improve weak-grid integration and power quality without replacing the established DFIG converter-control platform. Full article

The flexible DC transmission scheme based on modular multilevel converters (MMCs) is currently the mainstream solution for offshore wind power delivery. With the ongoing growth in both installed capacity and the offshore distance of wind power projects, the dimensions and weight of corresponding offshore converter stations have increased substantially. These developments present significant economic constraints and engineering challenges, thereby complicating the deployment of large-scale, long-distance offshore wind energy systems. Compared with MMCs, diode rectifier units (DRUs) offer advantages such as compact size, light weight, low cost, reduced operating losses, and high reliability. Nevertheless, DRUs lack active control capability, and conventional grid following wind turbines cannot independently support the voltage of the offshore AC network, which severely limits their application in offshore wind scenarios with stringent economic requirements. Grid forming control of wind turbines is an effective approach to address this issue. Given the widespread application of doubly-fed induction generators (DFIGs) in engineering practice and their relatively low capital costs, this study investigates the implementation of grid-forming control strategies in DFIGs to address the stability challenges of DRU-based HVDC transmission systems during fault conditions. First, the mathematical model of the DFIG is established. Then, a suitable control strategy is designed to endow the turbine with certain grid forming capabilities. Finally, the developed simulation model and control strategy are verified in PSCAD/EMTDC. The results demonstrate that the proposed grid forming DFIG control strategy can maintain stable offshore AC voltage and frequency under various fault conditions, ensure continuous and reliable operation of the DRU, and achieve fault ride through. On this basis, to account for engineering practicality and cost considerations, this study further proposes a hybrid transmission scheme combining grid-following and grid-forming DFIGs. Simulation results confirm that this hybrid scheme also achieves satisfactory operational performance, while reducing the potential cost increase associated with full-scale grid-forming retrofits, it effectively ensures fault ride-through capability and system operational stability. This method provides an effective solution for low cost, highly reliable offshore wind power DC transmission. Full article

This study establishes a field-measurement-based wideband modeling and station-level simulation framework for conducted high-frequency (HF) disturbance studies in modular multilevel converter-based high-voltage direct-current (MMC-HVDC) stations. Full-scale engineering-site frequency-response measurements are used to identify kHz-to-MHz terminal models of the arm reactor and the valve-side winding of the converter transformer. The arm reactor is fitted in the admittance domain by vector fitting and synthesized as a passive parallel network containing the main inductive path and multiple damped resistor–inductor–capacitor (RLC) branches. The transformer valve-side winding is represented by a Foster I/II hybrid $\pi$-type terminal network reconstructed from two single-phase port-impedance measurements. The validated equipment models are integrated into a representative Power Systems Computer-Aided Design (PSCAD) station model. A 2 ms valve-side source sequence, constructed from nearest-level-control switching instants and a parameterized switching-transient template, is applied in paired injection and zero-injection simulations. For the representative event, the source peak is 605.6 V. Over the first 4 $\mathsf{\mu }$s, the arm-reactor terminal reaches 972.6 V, while the direct-current (DC)-side, valve-side alternating-current (AC), and point-of-common-coupling (PCC) responses reach 534.2, 438.4, and 151.9 V, respectively. The corresponding peak changes relative to the source are $+4.11$, $-1.09$, $-2.81$, and $-12.01$ dB. The DC-side response contains a dominant damped oscillation near 0.61 MHz, and the AC/PCC transfer varies markedly across 0.2–2.0 MHz. In a separate control-identical comparison over the first 2.5 $\mathsf{\mu }$s, the field-identified and lumped models give DC-side peaks of 171.9 and 1.23 V and PCC peaks of 121.4 and 3.93 V under the same excitation. The framework connects field-identified equipment terminal behavior with station-level time-domain propagation analysis and provides a modeling basis for broadband resonance screening and conducted electromagnetic-interference (EMI) assessment. Full article

The rapid electrification of transportation has accelerated the demand for high-power electric vehicle (EV)-charging systems with high efficiency, compact size, galvanic isolation, and flexible scalability. Conventional isolated EV chargers typically adopt cascaded AC–DC and DC–DC conversion stages, which require additional semiconductor devices, passive components, and bulky dc-link capacitors, thereby increasing system complexity and limiting power density. This paper proposes a scalable three-phase modular parallel quasi-single-stage isolated single-ended primary-inductor converter (SEPIC) for high-power EV fast-charging applications. The proposed converter integrates power factor correction, voltage regulation, and high-frequency isolation within a unified SEPIC-based conversion cell, eliminating the intermediate dc-link capacitor while reducing the number of magnetic components and power conversion stages. By employing a Δ-connected three-phase input and input/output-parallel modular configuration, the proposed architecture provides a flexible power expansion approach based on a 9 kW basic module, with the potential to extend to higher power levels, such as 54 kW, through paralleling multiple identical modules. The operating principle, steady-state characteristics, continuous conduction mode (CCM)/discontinuous conduction mode (DCM) transition mechanism, current-sharing behavior, and control strategy are systematically investigated. An 18 kW prototype consisting of two parallel modules is experimentally validated under 380 V three-phase AC input and 400 V DC output conditions. The experimental results demonstrate a peak efficiency of 97.5%, a rated efficiency of 97.3%, a power factor (PF) of 0.999, and an input current total harmonic distortion (THD) of 2.55%, confirming the effectiveness and scalability of the proposed converter for high-power EV fast-charging applications. Full article

This paper proposes a coordinated low-voltage ride-through (LVRT) control framework for three-phase converter-interfaced distributed generation (DG) systems that integrates autocorrection droop control (AcDC) and Adaptive Current-Limited Reactive Priority Control (ACL-RPC). Key limitations of current LVRT control methods are addressed, such as weak and transient performance and adaptability problems due to the presence of post-saturation clipping, indirect current reference shaping, or discrete switching in LVRT current limiting techniques. The AcDC method alters the voltage reference in line with the severity of the voltage dip, while the ACL-RPC method imposes a rigid current limit and constructs the active and reactive current components in a flexible manner. The coordinated method of both approaches even enables the support of voltage with the network, the suppression of current transients, and the seamless control of current with no need for the estimation of network impedance or fault type resolution. The simulations and tests carried out show that the current limit, transient overshoot, and post-fault performance with respect to LVRT methods showed a marked improvement. The results also support the hypothesis that the three-phase converter-interfaced DG systems with the proposed methods offer improved LVRT performance, protection of the converter systems, and enhanced dynamic stability with respect to disturbances from the grid. Full article

Active-power ceilings create a control challenge in droop-controlled grid-forming converter networks because the electrical response is faster than the measurements and outer control. Projected and projection-free power limiting use filtered active power in the outer power–frequency channel and therefore cannot act directly on the first electrical power peak. This paper proposes constraint-activated projection-free control, which coordinates a shaped projection-free multiplier with a bounded resistance term in the capacitor-voltage reference driven by instantaneous terminal power. A general full-order dynamic model describes the converters, controllers, and network without tying the formulation to a particular benchmark. Local well-posedness is established, and the proposed controller is shown to preserve the constrained projection-free equilibrium and active-branch Jacobian, allowing the same full-order stability assessment. Across ten tested scenarios with unchanged controller parameters, the proposed controller reduces peak power exceedance by 38.7–55.4% and accumulated excess energy by 34.1–62.2%. The corresponding DC-buffer requirement decreases without activating the independent current limiter, which isolates the source-side power constraint from AC overcurrent. A network-level study demonstrates sequential transitions between one and two constrained sources while the remaining converter supplies the feasible power imbalance. Full-order stability verification, component studies, and parameter sweeps establish the role and useful range of each controller path. Full article

This article presents a review and comparative analysis of converter architectures for electrolyzer systems, covering alternating current (AC) -grid-connected, direct-current (DC) -grid-connected, and renewable-energy-connected systems, as well as isolated and non-isolated configurations. The study classifies and compares key converter topologies based on engineering criteria, including voltage gain, efficiency, device count, control complexity, and implementation feasibility. Furthermore, the relationships among converter structures, power-source characteristics, and electrolyzer-system requirements are analyzed to reveal system-level engineering trade-offs. The analysis demonstrates that converter suitability depends on the combined requirements of the power source, galvanic isolation, electrolyzer characteristics, operating conditions, and application-specific engineering priorities. In addition, wide-bandgap semiconductor devices and electrolyzer operating characteristics are discussed as important factors in converter selection, particularly for improving converter efficiency, reducing current ripple, increasing power density, and supporting dynamic operation. This article therefore provides a systematic framework for converter classification and selection according to power-source characteristics, electrolyzer requirements, and application power levels. Full article

This paper reviews recent advances in integrated circuits for resonant wireless power transfer (WPT) systems in biomedical implants, with emphasis on resonant compensation networks and receiver-side power conversion. In these systems, a compact receiver coil must harvest attenuated alternating current (AC) power through biological tissue and convert it into a safe, efficient, and regulated direct current (DC) supply for implantable electronics. Limited coil size, weak coupling, load variation, and thermal safety constraints have driven the evolution from passive rectifiers to active and regulated rectifiers with delay-compensation techniques. This review first introduces the operating principles of resonant WPT links and compares series–series, series–parallel, parallel–series, and parallel–parallel compensation topologies in terms of output characteristics and implant suitability. It then summarizes passive, cross-coupled, active full-wave, delay-compensated, and regulated rectifiers. Finally, design guidelines are provided for selecting compensation and rectifier architectures according to power level, coupling condition, operating frequency, integration complexity, and regulation requirements. Full article

To address the low-inertia frequency-security risk and insufficient voltage support at converter buses in receiving-end AC/DC hybrid systems with high wind power delivered through voltage source converter-based multi-terminal direct current (VSC-MTDC) transmission, this paper proposes a risk-averse unit commitment method that simultaneously considers rate-of-change-of-frequency (RoCoF)-based inertia constraints and multi-infeed short-circuit ratio (MSCR) constraints. The proposed method converts the post-contingency initial RoCoF limit into a minimum system inertia requirement and incorporates an operating-state MSCR constraint to jointly characterize the requirements for frequency security and converter-bus system strength. Meanwhile, an improved information-gap decision theory (IGDT) method is used to describe the upper and lower boundary deviations of wind power, and a risk-averse dispatch model is established with the objective of maximizing the allowable wind-power deviation range. Case studies on modified IEEE 30-bus and PEGASE 89-bus systems show that considering either constraint alone is insufficient to simultaneously maintain the post-contingency initial RoCoF within its prescribed limit and ensure adequate converter-bus system strength. Coordinating the two types of constraints can improve operating security, but it reduces the allowable wind-power deviation range and increases operating cost. Full article

With increasing renewable and power-electronic penetration, emergency control must convert early post-fault measurements into feasible actions within a short latency budget. This paper proposes a response-driven online framework that uses the simplified branch transient transmission capacity (sBTTC) as a physically interpretable interface between causal stability forecasting, action-response prediction, and constrained control. A preceding masked Informer forecasts the no-control all-branch sBTTC trajectories from the first 1.00 s of measured response; a ConvLSTM then predicts generator-tripping recovery and the recovery associated with four load-shedding levels. These predictions are embedded in a weighted mixed-integer piecewise-linear model with stability-recovery, action-bound, and power-balance constraints. On the studied 100-bus renewable-rich AC/DC system, ConvLSTM achieved an RMSE of $7.193\times {10}^{-3}$ and an MAE of $5.674\times {10}^{-3}$ with 69.16 ms inference time. Its inference was 66.42% faster than Informer, while its RMSE was only 2.06% higher; relative to conventional LSTM, its RMSE and MAE were reduced by 28.21% and 21.53%, respectively. Across 62 grouped out-of-sample disturbances, the validation results give a 96.77% control success rate. In the representative disturbance, 900 MW of generation tripping and 740 MW of load shedding restored the nonlinear terminal sBTTC to 0.998, and the command was issued 1.36 s after fault inception. The framework provides an auditable forecast–response–decision chain; its additive approximation is restricted to the validated action range and uses an empirical 0.05 sBTTC recovery margin selected to exceed the observed 95th-percentile absolute error; this margin is not interpreted as a worst-case error bound. Full article