The change rate of the dc reactor voltage with predefined protection thresholds is proposed to provide fast and accurate fault detection in a meshed multiterminal HVDC system. This equivalent measurement second derivative current but has better robustness terms electromagnetic-interference noise immunization. In addition detection, scheme can also accurately discriminate faulty branch from healthy ones network by considering polarities amplitudes two reactors connected same converter...

For a large multiterminal HVDC system, it is important for dc fault on single branch to not cause significant disturbance the operation of healthy parts network. Some circuit breakers (DCCBs), example, mechanical type, are low cost and have power loss, but been considered unsuitable protection isolation in system due their long opening times. This paper proposes use additional passive components novel converter control combined with DCCBs ensure that network can continue operate without...

Parallel operation is an effective way to improve the capacity of full power converter in permanent-magnet direct-drive wind generation system. But it causes zero-sequence circulating-current (ZSCC), which brings current discrepancy, waveform distortion, losses, and electromagnetic interference (EMI), etc. The paper proposes a new topology converters are composed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> converters. have same...

A new hybrid cascaded modular multilevel converter for the high-voltage dc transmission system is presented. The half-bridge cells are used on main power stage and cascade full-bridge (FB) connected to its ac terminals. generates fundamental voltages with quite low switching frequency, resulting in relatively losses. FB only attenuate harmonics generated by stage, without contribution transfer. Thus, energy-storage requirement of capacitance reduced significantly. Due fault reverse blocking...

Distributed phase-locked loop-based frequency control is proposed in this paper for offshore wind turbine converters connected with diode-rectifier-based high-voltage-direct-current systems. The enables a large number of turbines to work autonomously contribute the ac and voltage regulation. also provides automatic synchronization offline grid. Stability analyzed using root locus method. Moreover, active dc onshore modular multilevel converter (MMC) ride-through an fault, where MMC quickly...

A novel hybrid, modular multilevel converter is presented that utilizes a combination of half-bridge and three-level cells where the utilize clamp circuit which, under dc side faults, capable blocking fault current thereby avoiding overcurrents in freewheel diodes. This capability demonstrated through simulation shown to be as good which full-bridge but with added benefits of: lower conduction losses; fewer diode semiconductor switching devices, and; shoot-through modes. The count loss...

This paper proposes control strategies for megawatt-level direct-drive wind generation systems based on permanent magnet synchronous generators. In the paper, a circulating current model is derived and analyzed. The parallel-operation controllers are designed to restrain reactive power circulation beat-frequency currents caused by discontinuous space-vector modulation. schemes do not change configurations of system consisting parallel multiple converters. They easy implement modular designs...

Parallel operation of a diode rectifier-based high-voltage direct current (DR-HVDC) and modular multilevel converter (MMC)-based HVDC (MMC-HVDC) for transmitting offshore wind energy is investigated in this article. An enhanced active power control scheme the MMC station proposed to improve flow distribution between MMC-HVDC DR-HVDC links which are both connected farm (OWF) ac network. By regulating voltage, all powers transmitted via link low conditions while controlled around zero reduce...

With the aim to develop a lipid nanoparticle for biochanin A (BCA) by emulsion-evaporation and low temperature-solidification technique. The results revealed that BCA–PEG–NLC not only have small mean particle (148.5 ± 2.88 nm) with narrow polydispersity index (PI) (0.153 0.01), encapsulation capacity (99.62 0.06%), payload (9.06 0.01%), zeta potential (−19.83 1.19 mV), but also slower release rate compared BCA suspension over 48 h dialysis method (n=3). crystallinity of matrix within was...

Whilst third harmonic injection is extensively used in modular multilevel converter (MMC) control, its significant advantages over sinusoidal modulation have not been fully explored. This study evaluates the influence of on system power losses, submodule (SM) capacitance, circulating current, and fault current mathematical models are derived. Station conduction losses reduced by 11%, yielding higher efficiency lowering cooling capacity. The SM capacitance 24%, which significantly lowers...

Abstract The use of MVDC collector systems has been proposed as a way to reduce the levelised cost energy (LCOE) offshore wind farms. This study provides quantitative assessment conditions required for such all‐DC farms be cost‐effective. A comprehensive LCOE analysis two AC and farm designs is performed, with sensitivity studies on size, distance from shore, voltage, component costs. results show that MVDC‐based more cost‐effective than equivalent HVDC farms, DC/DC converter must less 90%...

Offshore AC fault protection of wind turbines (WTs) connecting with diode rectifier unit based HVDC (DRU-HVDC) system is investigated in this paper.A voltage-error-dependent current injection proposed to regulate the WT during offshore transients and quickly provide for detection.Considering different locations, characteristics symmetrical asymmetrical faults are presented requirements detection addressed.A simple effective solution, combining both overcurrent differential protection, by...

When a pole-to-pole dc fault occurs in multi-terminal HVDC system, it is desirable that the stations and solid-state transformers on healthy cables continue contributing to power transfer, rather than blocking. To reduce current of modular multilevel-converter-based transformer, active control proposed, where ac components arm currents are regulated independently. By dynamically regulating offset voltage being set at half rated voltage, component reduced significantly. Additionally,...

The adoptions of medium voltage in ac collection networks large dc-connected wind farms significantly increase the current magnitudes during normal and fault conditions. Controlling currents at zero asymmetric faults is possible, but it has several drawbacks such as increased risk protection mal-operation due to absence currents, which also tends prevent recovery postfault. Therefore, this paper presents an enhanced control strategy that exploits induced negative sequence voltages facilitate...

To detect the dc faults for modular multilevel converter (MMC)-based grids using overhead line transmission, many protection methods in phase-domain have been proposed. These existing suffer from incomplete function, weak theoretical basis, and sensitivity to fault resistance noise disturbance. overcome these shortcomings, this article proposes an improved algorithm modal-domain approach MMC-based grids, which decouples interaction between positive negative poles mitigates strong frequency...

This article reviews dc transmission technologies for future power grids. The emphasises the attributes that each technology offers in terms of enhance controllability and stability, resiliency to ac faults, encourages increased exploitations renewable energy resources (RERs) electricity generation. Discussions ac/dc dc/dc converters reveal self-commutated are critical better utilisation large RERs which tend be dispersed over wide geographical areas, offer much needed operation centralised...

The increasing demand for DC power loads across various applications such as railway systems, data centers, electric vehicle charging stations, and hydrogen electrolyzers necessitates efficient rectifiers capable of converting medium-voltage AC (MVAC) to low-voltage (LVDC) while accommodating a wide voltage range. This paper presents novel high-power MVAC-LVDC rectifier that integrates submodule (SM) arms, thyristors, monolithic medium-frequency transformer (MMFT), diode bridge. SM arms...

We introduce the first version of GPU4PySCF, a module that provides GPU acceleration methods in PySCF. As core functionality, this implementation two-electron repulsion integrals (ERIs) for contracted basis sets comprising up to g functions using Rys quadrature. an illustration how can accelerate quantum chemistry workflow, we describe use ERIs efficiently integral-direct Hartree-Fock build and nuclear gradient construction. Benchmark calculations show significant speedup 2 orders magnitude...

Flat-topped modulation is a member of the family triplen-series injection techniques that has been extensively utilized in pulsewidth-modulated inverter systems to increase dc link and, hence, semiconductor utilization. We propose use an optimized flat-topped scheme for modular multilevel converter (MMC) control. The waveform minimizes magnitude triplen harmonics, particularly compared popular space-vector (SVM) technique, while fully utilizing voltage. This particular advantages if side...

This work describes the preparation of a PEGylated niosomes-mediated drug delivery systems for Paeonol, thereby improving bioavailability and chemical stability prolonging its cellular uptake enhancing synergistic anti-cancer effects with 5-Fu. niosomes, which are prepared from biocompatible nonionic surfactant Spans 60 cholesterol, modified PEG-SA. Pae-PEG-NISVs were evaluated in vitro vivo. The cytotoxicity was investigated against HepG2 cells. Fluorescence microscope used to detect...

To reduce the cost of bulk power transmission using voltage source converter high-voltage DC (HVDC) technology, a unidirectional hybrid is proposed, where diode rectifier (DR) and modular multilevel (MMC) based on full-bridge (FB) submodules are connected in series side. The FB-MMC controls its to regulate transmitted power. majority via DR considering efficiency superiority only low rating required. A thyristor valve equipped at side prevent potential overcharge FB during faults. Compared...

This paper investigates the stability of diode rectifier based HVDC (DR-HVDC) connected offshore wind farms. The impedance model DR-HVDC farms in dq frame is analytically developed and validated by comparing its impedances to those obtained from frequency scanning time domain EMT PSCAD/EMTDC. Based on model, impacts sizes DC smoothing reactors AC filters system are analyzed. It shows reduced reactance degrades d-axis margin can potentially lead instability. Higher bandwidth voltage control...