Strong Anti-interference Ability Research Articles

Norm and interpolation based absolute stress evaluation in steel members using the Lcr wave

The uniaxial absolute stress in steel members is a vital indicator for evaluating the performance of steel structures. Non-destructive ultrasonic detection is widely applied in the absolute stress measurement of steel members with the advantages of easy implementation, no limits on materials and high precision. The acquisition algorithm of time-of-flight (TOF), the sampling rate of ultrasonic signal and the processing of outliers determine the accuracy of the stress measurement. In this study, we proposed a norm and interpolation based algorithm for absolute stress measurement using the longitudinal critically refracted (Lcr) waves, which improves the accuracy and velocity of the absolute stress measurement. Firstly, the norm was designed to obtain the TOF of the ultrasonic signal. When only the Lcr wave arose in the ultrasonic signal, the two-norm similarity algorithm was found to be consistent with the cross-correlation-based algorithm and the corresponding theoretical expressions were derived. With the non-Lcr wave in the ultrasonic echo, the two-norm similarity algorithm has stronger anti-interference ability. Secondly, the pchipslopes, spline and linear interpolation algorithms were introduced via which the TOF of ultrasound with low sampling rate reaches the same accuracy as that of high sampling rate signal. Finally, a special class of outliers in TOF was explored, and a threshold based on the number of shift points and the stress feature was proposed to calibrate these outliers to normal values. Experiments demonstrate the proposed algorithm improves the accuracy and velocity of uniaxial absolute stress measurement in structural steel members.

A novel fluorescent molecule based on 1,2,3-triazole for determination of palladium (II) and hydrazine hydrate in aqueous system

In recent years, hydrazine hydrate has been widely used in various fields as fuel and chemical raw materials, etc. However, hydrazine hydrate is also a potential threat to living body and natural environment. The effective method is urgently needed to detect hydrazine hydrate in our living environment. Secondly, as a precious metal, palladium has attracted more and more attention because of its excellent properties in industrial manufacturing and chemical catalysis. However, its potential danger is also slowly approaching, so it is necessary to find an excellent way to detect palladium, too. Herein, a fluorescent molecule, 4,4′,4′',4′''-(1,4-phenylenebis(2H-1,2,3-triazole-2,4,5-triyl)) tetrabenzoic acid (NAT), was synthesized. Firstly, NAT has very high selectivity and sensitivity for determination of Pd2+, because Pd2+ can coordinate well with carboxyl oxygen of NAT. The detection performance of Pd2+ is that the linear range is from 0.06 to 4.50 μM and the detection limit is 16.4 nM. Furthermore, the chelate (NAT-Pd2+) can continue to be used for quantitative determination of hydrazine hydrate with a linear range of 0.05–6.00 μM and the detection limit is 19.1 nM. The interaction time of NAT-Pd2+ and hydrazine hydrate is about 10 min. Of course, it also has good selectivity and strong anti-interference ability for many common metal ions, anions and amine like compounds. At last, the ability of NAT to quantitatively detect Pd2+ and hydrazine hydrate in actual samples has also been verified and the results are very satisfactory.

A Novel D-π-A Type Fluorescent Probe for Cu2+ Based on Styryl-Pyridinium Salts Conjugating Di-(2-picolyl)amine (DPA) Units.

A novel D-π-A type fluorescent probe L(NO3) for Cu (II) sensing was designed and fully characterized. The probe consists of a styryl-pyridine cation fluorescent group and a di-(2-picolyl)amine (DPA) receptor unit, which are linked by a phenyl group to form an electron donor-π-acceptor (D-π-A) conjugate system, especially the introduction of a nitrate counter anion for significantly enhanced water solubility of the probe. Fluorescence titration studies of the probe L(NO3) showed a higher selectivity for Cu2+ than other metal ions, and the emission spectrum was strongly quenched upon binding. The competitive binding assay and the low detection limit (0.932 µM) showed that the probe L(NO3) had strong anti-interference ability and excellent Cu2+ detection performance. The binding ratio of probe L(NO3) and Cu2+ was determined from Job's plot to be 1:1, which is consistent with the results obtained from X-ray crystal structures. Meanwhile, the probe showed instantaneous chemical reversibility when titrated with EDTA solution, indicating potential recycling properties of the probe. In addition, the design of inexpensive fluorescent test strips can perform the on-site and real-time detection Cu2+ with a color recognition application.

Post-synthesis introduction of dual functional groups in metal–organic framework for enhanced adsorption of moxifloxacin antibiotic

Highly effective removal of antibiotics from aqueous solution is of importance while still faces challenge. Herein, we report a novel metal–organic framework (MOF) adsorbent, MOF-808-SIPA (SIPA, 5-sulfoisophthalic acid), constructed via post-synthesis exchange strategy. On the basis, dual active groups including sulfonic acid and carboxyl groups are successfully introduced. The novel MOF-808-SIPA exhibits a high adsorption capacity of 287.1 mg g−1 for moxifloxacin hydrochloride (MOX·HCl), superior to that (174.6 mg g−1) of the pristine MOF-808-AA (AA, acetic acid). Besides, MOF-808-SIPA shows rapid adsorption equilibrium of ∼ 30 min, strong anti-interference ability from pH and inorganic ions, and feasible regeneration. The superiority renders MOF-808-SIPA a potential adsorbent for MOX removal. Density function theory (DFT) calculation and experiment confirm that H-bond interaction contributes largely to the excellent adsorption in MOF-808-SIPA. Our work provides a guideline for designing high-efficiency MOF-based adsorbent.

Efficient activation of peroxymonosulfate by MoS2 intercalated MgCuFe layered double hydroxide for phenol pollutant control

The application of MoS2 as an emerging cocatalyst in wastewater treatment is of great significance, but the efficiency of cocatalyst is often limited due to its easy agglomeration and insufficient interaction with the catalyst. Here, we used layered double hydroxide (LDH) as the catalyst and the growth template of MoS2 to achieve an efficient combination of catalyst and cocatalyst in the removal of organic pollutants by peroxymonosulfate (PMS) activation. The outcomes showed that the MoS2 intercalated LDH composite samples (MLDH) owned excellent phenol degradation performance, reaching nearly 100% removal within 10 min, and the calculated apparent rate constants were 2.3, 5.6, 17.7 and 19.8 times higher than that of the samples of directly growing MoS2 on the LDH (M@LDH), physically blended MoS2 and LDH samples, LDH and MoS2, respectively. Based on the results of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), SO4•- had a major impact on the elimination of phenol, Mo(Ⅳ) in MoS2 also participated in and encouraged the Fe(Ⅲ)/Fe(Ⅱ) redox cycle, providing the driving force for the further activation of PMS. Moreover, the effects of pH value, anions, cations and water environment of MLDH during the activation of PMS were also determined, and it was found that under various catalytic environments, MLDH always maintained a high removal rate of phenol and showed strong anti-interference ability. Collectively, the results of this research would offer more possibilities and suggestions for creating highly effective catalysts for wastewater cleanup.

Long-distance multifunctional wireless sensing platform for identifying and ranging

With the rapid development of the Internet of Things, wireless sensors have become critical and are widely preferred in many application scenarios. An emerging wireless sensing solution based on the breakdown discharge effect has been proposed to tackle the challenges of wireless sensing and long-distance transmission. However, previous studies have mostly focused on amplitude modulation, which faces the challenges of clutter interference and easy distortion. Herein, we proposed a long-distance multifunctional wireless sensing platform based on breakdown discharge-induced displacement current. Frequency modulation (FM), with strong anti-interference ability and high precision, is utilized to modulate wireless signals. Furthermore, the functions of identifying and ranging are demonstrated, validating the universality, scalability and versatility of the wireless sensing platform, which promises great potential in the Internet of Things.

Constructing dimensionally stable TiO2 nanotube arrays/SnO2/RuO2 anode via successive electrodeposition for efficient electrocatalytic oxidation of As(III)

Arsenic-containing water needs to be purified to reduce the global hazards of arsenic to human health and ecosystems. Herein, successive electrodeposition of SnO2 and RuO2 nanoparticles on the TiO2 nanotube arrays (TNTAs) was performed to synthesize dimensionally stable TNTAs/SnO2/RuO2 anodes for highly efficient electrocatalytic oxidation of As(III) in aqueous solution. Such a TNTAs/SnO2/RuO2 anode possessed fast charge transfer, higher oxygen evolution potential (OEP), larger electrocatalytic active area, and excellent stability, and delivered effectively electrocatalytic oxidation As(III), of which 10 mg/L of As(III) was completely oxidized into As(Ⅴ) with lower toxicity within 20 min owing to the synergistic effect of RuO2 and SnO2. Impressively, the optimized TNTAs/SnO2/RuO2-10 anode presented an excellent electrochemical stability and longer service lifetime, and its oxidation conversion efficiency of As(III) still could be maintained to be 98% as well as its kinetic reaction constant decreased by only 0.03 even after 11 recycled usage, which was ascribed to the intensified interaction between RuO2 and TNTAs/SnO2. The excellence of the innovative anode was also evidenced through its strong anti-interference ability to coexisting ions and the elucidation of the associated oxidation reaction mechanism of As(III) on the surface of the anode by electron spin resonance and radical scavenger tests. This novel electrode integrates high electrocatalytic activity, high electron transport and high stability, ensures the long-term stable use of the electrode, while realizes efficient and rapid electrocatalytic oxidation of As(III) in aquatic environments. This work provides new ideas for further improving the catalytic performance and stability of dimensionally-stable anode materials.

Mind evolutionary algorithm optimization in the prediction of satellite clock bias using the back propagation neural network

Satellite clock bias is the key factor affecting the accuracy of the single point positioning of a global navigation satellite system. The traditional model back propagation (BP) neural network is prone to local optimum problems. This paper presents a prediction model and algorithm for the clock bias of the BP neural network based on the optimization of the mind evolutionary algorithm (MEA), which is used to optimize the initial weights and thresholds of the BP neural network. The accuracy of the comparison between clock bias data is verified with and without one-time difference processing. Compared with grey model (GM (1,1)) and BP neural network, this paper discusses the advantages and general applicability of this method from different constellation satellites, different atomic clock type satellites, and the amount of modeling data. The accuracy of the grey model (GM(1,1)), BP, and MEA-BP models for satellite clock bias prediction is analyzed and the root mean square error, range difference error, and the mean of the clock bias data compared. The results demonstrate that the prediction accuracy of the three satellites significantly increased after one-time difference processing and that they have good stability. The prediction accuracy of four sessions of 2 h, 3 h, 6 h, and 12 h obtained using the MEA-BP model was better than 0.74, 0.80, 1.12, and 0.87 ns, respectively. The MEA-BP model has a specific degree of improvement in the prediction accuracy of the different sessions. Additionally, the prediction accuracy of different models has a specific relationship with the length of the original modeling sequence, of which BP model is the most affected, and MEABP is relatively less affected by the length of the modeling sequence, indicating that the MEA-BP model has strong anti-interference ability.

Simultaneous morphology control and defect regulation in g-C3N4 for peroxymonosulfate activation and bisphenol S degradation

Nonmetallic catalysts that can effectively activate peroxymonosulfate (PMS) under visible light are of great interest for removing endocrine disruptors in water. In this study, a simple one-step strategy was developed to synthesize two-dimensional (2D) nitrogen-deficient graphitic carbon nitride (CNX) for visible-light activation of PMS (CNX/PMS/Vis). The CNX-3/PMS/Vis system could degrade bisphenol S (BPS) more efficiently (90.37 %, 90 min) than graphitic carbon nitride (g-C3N4)/PMS/Vis (58.36 %, 90 min). Experiments and density functional theory calculations showed that the improved catalytic performance was due to the 2D nitrogen defect structure in the modified g-C3N4. Such structure reduced the work function, inhibited the recombination of photogenerated carriers, enhanced the adsorption energy between g-C3N4 and PMS, and strengthened the synergy between photocatalysis and PMS activation. Radical quenching and electron paramagnetic resonance experiments demonstrated that the main mechanism of BPS degradation involved free radicals and nonradicals, wherein 1O2, O2•-, and h+ were the main reactive oxygen species, and •OH and SO4•- were the secondary species. In addition, CNX-3/PMS/Vis system had strong anti-interference ability to the environmental background and a wide range of operating pH. To summarize, herein we developed a low-cost and green nonmetallic catalyst to cooperate with PMS-based advanced oxidation technology via photocatalysis, providing new ideas to remove organic pollutants in water.

On–Off–On fluorescent sensing platform based on nitrogen-doped carbon dots for biothiols detection

Abnormal levels of biothiols in the human body are closely related to a variety of diseases, thus it is crucial for the selective detection of biothiols in the biological system. In this work, a Fe3+-triggered multifunctional nitrogen-doped carbon quantum dots (N-CQDs) on–off-on fluorescent sensing platform for the ultrasensitive detection of biothiols (GSH, Cys and Hcy) was successfully established. In detail, Fe3+ could adsorb on the surface of N-CQDs through coordination with the phenolic hydroxyl group of N-CQDs, resulting in the quenching of the fluorescence of N-CQDsdue to the photoinduced electron transfer (PET) effect from N-CQDs to Fe3+. After the addition of biothiols, there was stronger coordination between Fe3+ and biothiols than N-CQDs-Fe3+, resulting in fluorescence recovery of N-CQDs. On basis of the on–off-on principle, the N-CQDs-Fe3+ fluorescent probe was applied to determine biothiols. Under optimal parameters, the N-CQDs-Fe3+ fluorescent probe exhibited a relatively lower limit of detection (LOD) of 20.39 nM (GSH), 9.31 nM (Hcy) and 1.93 nM (Cys), respectively, which was better or comparable compared with previous reports. Further, the constructed N-CQDs-Fe3+ fluorescent sensing platform was validated with strong anti-interference ability, good reproducibility and repeatability, and also performed well in serum samples, demonstrating a promising potential in clinical diagnosis for biothiols analysis.

High-precision Positioning Method for BD3 System Based on Adaptive Optimization

It is of great significance to locate faults quickly and accurately in power distribution system to improve system reliability and recover quickly. With high positioning accuracy, strong anti-interference ability in mountainous areas and cities, and the ability to provide all-weather and all-round services, the BeiDou-3 (BD3) navigation satellite system has broad application prospects in power systems. Using the filtering principle of normalized least mean square (NLMS) filter, a high-precision positioning method for BD3 system based on adaptive optimization is propose to eliminate the pseudo-range error caused by electromagnetic interference. Simulation results show that NLMS-based adaptive pseudo-range filtering method can availably decrease the pseudo-range error caused by high proportional electromagnetic interference in the power system, achieve adaptive optimization of power system device positioning, and improve positioning accuracy.

Enhanced degradation of sulfamethoxazole by activation of peroxodisulfate with red mud modified biochar: Synergistic effect between adsorption and nonradical activation

Since the discovery of the potential environmental risk associated with large quantities of red mud, there has been an urgent need to find a rational disposal technology for this waste. In this study, low-cost iron-based biochar catalysts (RM@BC-x) were synthesized by co-pyrolysis of waste red mud and spent coffee grounds after ball milling. RM@BC-800 exhibited remarkable adsorption capacity, reaching 4.70 mg/g in 120 min. The adsorbed SMX was degraded simultaneously after adding peroxodisulfate (PDS), and sulfamethoxazole (SMX) was completely removed from the solution in only 30 min. Correlation analysis and pre-sorption experiment proved that the adsorption of SMX significantly enhanced the oxidation effect. Moreover, the Fe0, defects and CO groups of RM@BC-800 were the main active sites. Singlet oxygen (1O2) played a dominant role in the degradation of SMX rather than the traditional radicals (•OH or SO4•−). In particular, O2•− was shown to be used mainly as a precursor for the production of 1O2 without directly oxidizing SMX. The steady state concentration of 1O2 has been calculated to be hundreds or thousands of times higher than that of other radicals. Five degradation pathways of SMX were proposed (including NS bond cleavage, hydroxylation, and –NH2 oxidation). RM@BC-800 has the advantages of strong anti-interference ability, low iron leaching based on energy calculations and environmental impact assessments. This work provides a new option for the resource utilization of red mud and designs a green material with fast adsorption and efficient catalysis for the practical treatment of antibiotic wastewater.

Adsorptive removal of anionic azo dye by Al3+-modified magnetic biochar obtained from low pyrolysis temperatures of chitosan.

Magnetic γ-Fe2O3/Al3+@chitosan-derived biochar (m-Fe2O3/Al3+@CB) was prepared by introducing magnetic maghemite (γ-Fe2O3) nanoparticles and aluminum sulfate [Al2(SO4)3] into chitosan-derived biochar (CB) obtained at low pyrolysis temperatures. m-Fe2O3/Al3+@CB was used to remove typical anionic azo dye (Congo red, CR). Effects of initial CR concentration, contact time, initial pH value, background electrolytes, and temperature on CR adsorption by m-Fe2O3/Al3+@CB were studied. Compared with magnetic chitosan-derived biochar (m-Fe2O3@CB), m-Fe2O3/Al3+@CB exhibited excellent performance for a wider range of pH values (pH 1-7) and in the presence of background electrolyte. The introduction of Al3+ is an effective method for improving the properties of magnetic chitosan-derived biochar. High CR adsorption capacity (636.94mgg-1) of m-Fe2O3/Al3+@CB could result from collaborative effect of flocculation/coagulation and electrostatic attraction. These results demonstrated that m-Fe2O3/Al3+@CB is a potential adsorbent for effective removal of organic dyes from aqueous solution due to its high adsorption capacity and convenient magnetic recovery and stronger anti-interference ability against coexisting anions in wastewater.

Weak current induced by coal deformation and fracture and its response to mine seismicity in a deep underground coal mine

Weak currents can be stimulated from coal and rock materials under a load. To investigate the response characteristics of weak current to coal failure and mine seismicity, both laboratory experiments and field tests on weak current measurement of stressed coals were conducted. The response characteristics of weak current was analyzed, the quantitative relationship between weak current and mechanical behaviors was studied and the precursors of coal failure and mine seismicity based on weak current response were investigated. The results of laboratory experiments show that the weak current increases linearly with stress and strain in the elastic deformation stage and shows an accelerated increasing trend after entering the elastic deformation stage, reaching its peak value when the final failure occurs. A fracture is accompanied by a suddenly increased current (SIC), of which the intensity is proportional to the stress drop. The accelerated increase of weak current accompanied by fluctuations can be used as a precursor of coal failure. The weak current measured in an underground coal mine responds well to mine seismicity that occurs in the increasing process of a SIC. The continuously accelerated increase of weak current can be used as a precursor of mine seismicity, to which the weak current could respond few minutes in advance. It is feasible to use the weak current technique for rockburst prediction in mines and tunnels because of its strong anti-interference ability and early response to mine seismicity and coal/rock failure.

Flexible electrochemical sensor constructed using an active copper center instead of unstable molybdenum carbide for simultaneous detection of toxic catechol and hydroquinone

A new electrochemical sensor based on a Cu-CuO@MoOx-modified polyethylene terephthalate electrode spin coated with PEDOT (Cu-CuO@MoOx-PEDOT/PET) was developed for simultaneous determination of catechol (CT) and hydroquinone (HQ). A zerovalent copper and copper(II) oxide intercalated molybdenum oxide MoOx (x = 2 or 3) hybrid nanomaterial (Cu-CuO@MoOx) by introducing active copper catalytic centers into the Mo2C@MoOx system based on unstable Mo2C, and replaced Mo2C using a simple hydrothermal method. At room temperature, the Cu-CuO@MoOx-PEDOT/PET electrode demonstrated the lowest detection limits of 0.216 and 0.221 μM for CT and HQ (S/N = 3), respectively. In addition, the applicability of this method was proven by the recovery of CT and HQ in spiked tap water samples. The Cu-CuO@MoOx-PEDOT/PET flexible electrode had strong anti-interference ability, good repeatability and long-term stability. It was used in the detection of CT and HQ in Nanjing tap water, the recoveries of CT and HQ calculated from the i–t curve were 99.36 % and 97.56 %, respectively. Most importantly, the flexible electrode could still maintain relatively stable electrochemical responses under different bending and folding conditions, and the obtained relative standard deviations (RSDs) were 2.78 % and 1.53 %, respectively. This flexible property holds promise for the construction of wearable electrochemical sensors.

Magnetic Field Testing Technique of System-Generated Electromagnetic Pulse Based on Magnetoresistance Effects

To address the technical challenges of system-generated electromagnetic pulse (SGEMP) measurement, the generation environment of SGEMP is introduced, and the characteristics of the magnetic field waveform to be measured are analyzed first in this paper. Then a magnetoresistance-based SGEMP measurement method is proposed for the first time. Aiming at the problem that the high frequency response of the existing commercial magnetoresistance chips cannot meet the test requirements, a pulsed magnetic field detector with strong anti-interference ability is developed in this work based on the tunneling magnetoresistance (TMR) sensor chip developed by Lanzhou University and a high-gain amplifier circuit with common mode rejection and a good shielding structure. It can be shown from the calibration results that the detector sensitivity factor is 4.0 nT/mV and the measurable pulse front is greater than or equal to 28 ns, which meet the requirements of SGEMP magnetic field waveform measurement. Based on the developed detector, the ideal test waveform is obtained under the “Flash II” hard X-ray pulse source through a reasonable experimental design. The related work has laid a foundation for validating the numerical calculation model and further mastering the propagation law and effect mechanism of SGEMP.

Multi-Parameter Optimization Analysis of Hydrodynamic Performance for Rim-Driven Thruster

The efficiency of rim-driven thrusters (RDT) has always been the focus of attention in the context of energy conservation and environmental protection. A multi-parameter collaborative optimization framework is proposed to improve the efficiency of RDT based on the response surface method (RSM). The common structural parameters of RDT, including pitch ratio, disk ratio and rake angle, are selected as design variables to carry out the Box–Behnken experimental design combined with the simulation data obtained through CFD calculations. The response surface second-order model is employed to evaluate the extent to which different parameters can affect the target variable and obtain the optimal hydraulic efficiency. The results show that the established model has high precision, good reproducibility and strong anti-interference ability. The influence of the pitch ratio, rake angle and disk ratio on open water efficiency decreases in sequence. Compared with the prototype RDT, the maximum efficiency of the optimized RDT is increased by 13.8%, and the surface pressure distribution and flow field characteristics are also significantly modified.

Construction of electrochemiluminescence aptasensor for acetamiprid detection using flower-liked SnO2 nanocrystals encapsulated Ag3PO4 composite as luminophore

Acetamiprid is a kind of broad-spectrum pesticides that has been largely applied in agriculture and household pest control. In this paper, a simple, novel and highly sensitive electrochemiluminescence aptamer sensor (ECL aptasensor) based on Ag3PO4-NH2-SnO2 was proposed. The ECL signal was greatly amplified with the synergistic effect of Ag3PO4 and NH2-SnO2 (Ag3PO4-NH2-SnO2) which was dropped on a glass carbon electrode (GCE) and used as working electrode. We designed an “on–off” ECL sensing strategy for the sensitive and specific detection of acetamiprid. Under the optimal conditions, the linear range of the sensor for acetamiprid detection was 1.0 × 10−11 ∼ 1.0 × 10−5 M, with a detection limit of 2.5 × 10−12 M (S/N = 3). The method showed simple and fast operation, high sensitivity and selectivity, strong anti-interference ability and good stability. More importantly, the developed aptasensor exhibited excellent recognition ability towards residual acetamiprid in actual water samples, which might open promising avenues to develop new ECL systems for biological analysis and environmental water monitoring.

An Improved Super-Twisting Sliding Mode for Flexible Upper-Limb Exoskeleton

Aiming at the decrease of tracking accuracy caused by nonlinear friction and strong coupling of the flexible upper-limb exoskeleton, an improved super-twisting sliding mode controller (ISTSMC) is proposed. Compared with the conventional super twisted sliding mode controller (STSMC), this method can replace the switching function under the integral term with a nonsmooth term, resulting in a faster response, less vibration when performing trajectory tracking, and reduced steady-state error. The introduction of the nonsmooth term causes the controller to have a stronger anti-interference ability. At the same time, the parameters of the ISTSMC can be adjusted in order to achieve the expected control performance. The effectiveness and feasibility of the proposed control algorithm are verified through experiments.

A Double-Ended Protection Principle for an LCC-VSC-MTDC System with Strong Anti-Interference Ability

The DC grid technology of multi-power supply and multi-drop-point power reception is an effective solution for large-scale renewable energy integration into the power grid. Line-commutated converter-Voltage source converter (LCC-VSC) power grids are one of the more important developmental directions of the future power grid that have occured in recent years. But the multi-terminal high voltage direct current system has the problems of inconsistent boundary characteristics, inconsistent control, and fault response characteristics, which puts higher requirements on the protection scheme. Thus, a completely new protection principle is proposed in this paper. Firstly, the fault characteristics of distributed capacitance current are analyzed. The reactive power calculated by the distribution parameters of different frequencies is different. Subsequently, the fault characteristics of DC reactive power are analyzed, and a DC reactive power extraction algorithm is proposed. The polarity of the multi-band DC reactive power is used to construct the protection scheme. Finally, the LCC-VSC power grid model verifies the correctness and superiority of the proposed protection scheme. The proposed scheme uses DC reactive power instead of fault current to solve the long delay problem caused by distributed capacitance. Compared with the prior art, the proposed solution is not affected by distributed capacitance and has a stronger anti-interference ability (600 + 10 dB + 1 ms).