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BackgroundThe appearance of cerebral venous sinus thrombosis (CVST) in childhood acute lymphocytic leukemia (ALL) is a rare life-threatening disease that can cause significant morbidity, neurological sequelae, and potentially poor outcomes.Case presentationWe present the case of a 13-year-old boy with ALL who developed CVST and intrinsic hemorrhage approximately 30 days after receiving chemotherapy with vincristine, dexamethasone, daunorubicin, and pegylated-asparaginase (PEG-Asp). He complained of a severe headache and then developed a generalized seizure at night. T1- and T2-weighted magnetic resonance imaging (MRI) and cerebral magnetic resonance venography sequences revealed superior sagittal sinus thrombosis and intrinsic hemorrhagic changes in the bilateral frontoparietal lobes. He received nadroparin calcium as the anticoagulant treatment and was switched to Erwinia asparaginase (Erwinia Asp) rather than PEG-Asp. Oxcarbazepine and clonazepam were started with good seizure control. Intrathecal treatment was delayed until 1 month later. Anticoagulation treatment was stopped for 24 h before and 6 h after lumbar puncture. Platelet transfusion was administered to ensure the platelet count remained at >50 × 109/L. Oral acetazolamide (500–1,000 mg, daily) was administered to relieve headache and reduce intracranial pressure. Three months later, brain MRI showed a complete resolution of or significant improvement in the filling defect. Nadroparin calcium was administered for 1 week after switching to Erwinia Asp to prevent clot recurrence. He completed the 6-month chemotherapy and is doing well with no neurological sequelae and no recurrence of bleeding or thrombosis.ConclusionsNadroparin calcium therapy appears to be safe and effective for pediatric CVST with ALL. The reintroduction of Erwinia Asp should be accompanied by anticoagulant therapy with nadroparin calcium.

Antibiotic pollution poses a serious environmental concern worldwide, posing risks to ecosystems and human well-being. Transforming waste activated sludge into adsorbents for antibiotic removal aligns with the concept of utilizing waste to treat waste. However, the adsorption efficiency of these adsorbents is currently limited. This study identified KOH modification as the most effective method for enhancing tetracycline (TC) adsorption by sludge biochar through a comparative analysis of acid, alkali, and oxidant modifications. The adsorption characteristics of TC upon unmodified sludge biochar (BC) as well as KOH-modified sludge biochar (BC-KOH) were investigated in terms of equilibrium, kinetics, and thermodynamics. BC-KOH exhibited higher porosity, greater specific surface area, and increased abundance of oxygen-based functional groups compared to BC. The TC adsorption on BC-KOH conformed the Elovich and Langmuir models, with a maximum adsorption capacity of 243.3 mg/g at 298 K. The adsorption mechanisms included ion exchange, hydrogen bonding, pore filling, and electrostatic adsorption, as well as π-π interactions. Interference with TC adsorption on BC-KOH was observed with HCO3−, PO43−, Ca2+, and Mg2+, whereas Cl−, NO3−, and SO42− ions exhibited minimal impact on the adsorption process. Following three cycles of utilization, there was a slight 5.94% reduction in the equilibrium adsorption capacity, yet the adsorption capacity remained 4.5 times greater than that of unmodified sludge BC, underscoring its significant potential for practical applications. This research provided new insights to the production and application of sludge biochar for treating antibiotic-contaminated wastewater.

With the increasing expansion of power systems, there is a growing trend towards active distribution networks for decentralized power generation and energy management. However, the instability of distributed renewable energy introduces complexity to power system operation. The active symmetry and balance of power systems are becoming increasingly important. This paper focuses on the characteristics of distributed resources and under-frequency load shedding, and a coordinated operation and control strategy based on the rapid adjustment of energy storage power is proposed. The characteristics of various controllable resources are analyzed to explore the rapid response capabilities of energy storage. The energy storage types are categorized based on the support time, and the final decision is achieved with power allocation and adjustment control of the energy storage system. Additionally, a comprehensive control strategy for under-frequency load shedding and hierarchical systems is provided for scenarios with insufficient active support. The feasibility of the proposed model and methods is verified via a multi-energy system case.

Objective Recent therapeutic advances have greatly enhanced the survival rates of patients with neuroblastoma (NB). However, the outcomes of neuroblastoma patients in China, particularly those with high-risk (HR) NB, remain limited. Method We retrospectively analyzed the clinical data and outcomes of NB patients who were treated at a tertiary pediatric cancer facility in China between January 2013 and October 2021. Results A total of 117 NB patients were recruited. Patients with very low-risk (VLR), low-risk (LR), intermediate-risk (IR), and HR-NB patients made up 4%, 27%, 15%, and 54% of total patient population, respectively. Patients diagnosed between 2013 and 2018 were treated according to the protocol of Sun Yat-Sen University Cancer Center and those diagnosed between 2019 and 2021 were treated according to the COG ANBL0531 or ANBL0532 protocol with or without autologous stem cell transplantation (ASCT). The 5-year EFS and OS of all risk groups of patients were 67.29% and 77.90%, respectively. EFS and OS were significantly decreased in patients with higher risk classifications (EFS: VLR/LR vs IR vs HR: 97.22% vs 67.28% vs 51.83%; ***P = .001; OS: VLR/LR vs IR vs HR: 97.06% vs 94.12% vs 64.38%; *P = .046). In HR-NB patients treated according to the COG protocol between 2019 and 2021, the 3-year OS of patients who received tandem ASCT was significantly greater than those who did not receive ASCT (93.33% % vs 47.41%; *P = .046; log-rank test). EFS was not significantly different between patients with and without ASCT (72.16% vs 60.32%). Conclusion Our findings show that patients with lower risk classification have a positive prognosis for survival. The prognosis of patients with HR-NB remains in need of improvement. ASCT may enhance OS in HR-NB patients; however, protocol adjustment may be necessary to increase EFS in these patients.

With the grid connection of a large number of distributed photovoltaics (PVs), the structure and operation mode of the distribution network are changed. Detailed modeling of the distribution network can accurately analyze the impact of these changes on the power system but leads to high model complexity and large amounts of calculation. Equivalent of the distribution network effectively reduces the model scale, where the static equivalent is the basis for the other equivalents. Most of the existing static equivalent methods target a few typical operation modes. However, they are unsuitable for multiple variable scenarios caused by PV power fluctuation. This paper proposes a static equivalent method of the distribution network with distributed PVs to adapt to complex and changeable operation modes. Firstly, a scenario generation method of PV and load power based on kernel density estimation and a copula function is proposed considering fluctuation and correlation of PV and load. Secondly, a parameter optimization method based on particle swarm optimization (PSO) is proposed to optimize the parameters in the static equivalent model of the distribution network under a single operation mode. Thirdly, an equivalent parameter estimation model based on convolutional neural network (CNN) is proposed to improve the efficiency of model parameter calculation under multiple operation modes. The effectiveness of the proposed method is verified under an example of an actual distribution network in Shandong, China. This method has efficiency and is suitable for multiple operating modes.

Abstract Potassium‐ion batteries (KIBs) with many technical advantages have attracted much attention. However, it is difficult to find a host material with a large interlayer spacing and stable framework to accommodate K+ with a large radius, resulting in the slower development of inorganic electrode materials for KIBs. Organic electrode materials have the advantages of structural diversity and adjustability, and their electrochemical performance depends on the conversion reaction between K+ and active functional groups, which ignores the steric hindrance effect caused by the large radius of K+. The research progress of organic KIBs is summarized from four aspects: organic cathode materials, organic anode materials, electrolyte optimization, and full batteries. The compositions, structures, reaction mechanisms, electrochemical performances, and development strategies of organic materials with various functional groups are presented. This paper can provide inspiration for researchers to develop high‐performance organic KIBs and realize the application of organic KIBs.

Abstract Background To strengthen the understanding of Hereditary Spherocytosis (HS) and determine the disease-causing mutation present with neonatal jaundice. HS is a hemolytic condition resulting from various erythrocyte membrane defects. Many different mutations result in HS, including mutations in ANK1. Case presentation A term neonate presented at ten hours with severe jaundice requiring exchange transfusion. At two months he was hospitalized due to repeated pallor and anemia requiring blood transfusions. Using next-generation sequencing, we discovered the responsible mutation in the proband but not in his parents; a heterozygous nucleotide variation of c.1000delA (p.1334Sfs*6) in ANK1. Thus hereditary spherocytosis was diagnosed. Conclusions Genetic detection is an important means of discovering the cause of hemolytic anemia in neonates and infants where routine diagnostic tests are unrevealing. We found a novel de novo mutation, c.1000delA (p.1334Sfs*6) in ANK1 that might account for other cases of HS in the Chinese population.

Large frequency deviation degrades the operation performance of the boiler and its auxiliaries. It affects the output of thermal power units. A significant change in power generation leads to a great frequency deviation. An extended frequency response model for long-term frequency stability assessment is constructed to consider the effects of frequency deviations on boiler auxiliaries. The static power-frequency characteristic of the thermal power unit within an extensive frequency variation range is analyzed. It reveals that the active power output of the generating unit is not monotonically increasing with frequency dropping. An inflection point is observed on the static power-frequency characteristic curve when considering boiler auxiliary frequency characteristics. In the range of greater frequency deviation, the output power decreases rapidly with frequency declination, and an unstable equilibrium point (UEP) of frequency stability is identified. A quantitative index is proposed for frequency stability assessment based on UEP. The stability characteristic and the frequency stability quantitative index based on UEP are analyzed. The frequency dynamic behaviors of the extended model are demonstrated to analyze frequency stability characteristics within an extensive frequency variation range by a single machine system and the IEEE 39-bus system with considering boilers and its auxiliaries.

Large-scale wind power connected to the grid efficiently reduces fossil fuel consumption, but extremely decreases grid inertial and increases frequency regulation pressure on the grid. Therefore, various wind farm-based frequency regulation technologies have been investigated in recent decades. Adaptive inertial droop control of wind turbines was considered as one of the most effective methods to enhance the inertia of the grid, because it can solve the decoupling problem between the power of wind farms and power system frequency. However, the present approaches mainly pay attention to the first frequency drop (FFD) or ignore the influence of control parameters. Hence, this paper proposes a black widow optimization algorithm (BWOA)-based step start-up adaptive inertial droop controller to smooth frequency fluctuation as well as alleviate FFD, the secondary frequency drop (SFD), and the third frequency drop (TFD). Besides, BWOA is employed to extract the best parameters of the designed controller under a 150-MW load increase. Then, the extracted parameters are used in three other load variation events to evaluate the performance of the proposed method in MATLAB/Simulink. Simulation results indicate that BWOA acquires satisfactory performances on various designed load variations. Compared with the trial-and-error method, FFD and TFD with BWOA under load increase are decreased by 10.9% and 12.8% at most, respectively.

With the continuous development of society and under the background of sustainable development and resource conservation, the proportion of renewable energy in the global energy structure is increasing. At the same time, wind power has been widely used in many regions of the world because wind power technology is more advanced and mature than other renewable energy sources. In addition, with a large number of wind turbines connected to the grid, it not only helps automatic generation control (AGC) of power systems but also brings new challenges and difficulties. In this study, a multi-source cooperative control model of wind power participating in AGC frequency regulation is established to solve the dynamic problem of power distribution from real-time total power command to different AGC units. This study presents an optimal AGC-coordinated control method based on the multi-objective mayfly optimization (MMO) algorithm, which makes the fitting degree of power command output and actual output curve high and the adjustment mileage payment minimum, so as to achieve the best AGC performance. Finally, the simulation results show that this method can effectively decrease the total power deviation and adjustment mileage payment in the multi-source-coordinated control of AGC.

Determining the operation scenarios of renewable energies is important for power system dispatching. This paper proposes a renewable scenario generation method based on the hybrid genetic algorithm with variable chromosome length (HGAVCL). The discrete wavelet transform (DWT) is used to divide the original data into linear and fluctuant parts according to the length of time scales. The HGAVCL is designed to optimally divide the linear part into different time sections. Additionally, each time section is described by the autoregressive integrated moving average (ARIMA) model. With the consideration of temporal correlation, the Copula joint probability density function is established to model the fluctuant part. Based on the attained ARIMA model and joint probability density function, a number of data are generated by the Monte Carlo method, and the time autocorrelation, average offset rate, and climbing similarity indexes are established to assess the data quality of generated scenarios. A case study is conducted to verify the effectiveness of the proposed approach. The calculated time autocorrelation, average offset rate, and climbing similarity are 0.0515, 0.0396, and 0.9035, respectively, which shows the superior performance of the proposed approach.

As large-scale wind turbines are connected to the grid, modeling studies of wind farms are essential to the power system dynamic research. Due to the large number of wind turbines in the wind farm, detailed modeling of each wind turbine leads to high model complexity and low simulation efficiency. An equivalent modeling method for the wind farm is needed to reduce the complexity. For wind farms with widely used doubly-fed induction generators (DFIGs), the existing equivalent studies mainly focus on such continuous control parts as electrical control. These methods are unsuitable for the low voltage ride through (LVRT) part which is discontinuous due to switching control. Based on particle swarm optimization (PSO) and density-based spatial clustering of applications (DBSCAN), this paper proposes an equivalent method for LVRT characteristics of wind farms. Firstly, the multi-turbine equivalent model of the wind farm is established. Each wind turbine in the model represents a cluster of wind turbines with similar voltage variation characteristics. A single equivalent transmission line connects all wind turbines to the power grid. By changing the terminal voltage threshold to enter LVRT, each equivalent turbine can be in different LVRT states. Secondly, an LVRT parameter optimization method based on PSO is used to obtain the dynamic parameters of the equivalent wind turbines. This method of parameter optimization is applicable to the equivalent of LVRT parameters. Thirdly, a clustering method based on DBSCAN is used to obtain suitable clusters of wind turbines. This clustering method can classify wind turbines with similar electrical distances into the same cluster. Finally, two examples are set up to verify the proposed method.

Introduction Haemophilia A is a rare inherited bleeding disease caused by the deficiency of coagulation factor VIII (FVIII). The main treatment protocol is to administer regular exogenous FVIII concentrate infusions. With the discovery of variability in individualised pharmacokinetics (PK) and bleeding phenotype, the previous weight-based approach needs to be replaced by more advanced PK-tailored prophylaxis with an accurate evaluation system. In this study, we combine individualised PK profiles and a complementary evaluation system to guide prophylaxis in paediatric patients with haemophilia A.Methods and analysis This is a single-centre, prospective single-arm study. The aim of this study is to assess the effectiveness of a new strategy combining PK and a complementary evaluation system to treat haemophilia A in Chinese paediatric patients. Sixty paediatric patients with haemophilia will be recruited. After PK testing, they will receive a PK-guided stepup prophylaxis in the next 2 years. The dosing regimen will be determined according to individualised PK profiles and complementary evaluation findings. Related indicators at the end of the study will be compared with the values at treatment initiation to examine the effectiveness of this new strategy. The demographic data of the investigated patients will be summarised by descriptive statistics. Quantitative data will be described by summary statistics, including arithmetic median, range, mean and arithmetic SD. Analyses will use t-test to compare indicators such as bleeding rate and imaging score at both ends of the study as well as during follow-up.Ethics and dissemination The study has been approved by the Ethics Committee of Beijing Children’s Hospital (Number 2020-Z-095). The findings will be presented at international meetings such as World Federation of Hemophilia World Congress. Related manuscripts will be submitted to peer-review journals such as Blood and Hemophilia.Trial registration number ChiCTR2000037821; Pre-results.

Abstract: We studied 1110 patients with β-thalassemia major aged ≤25 years who received transplants with grafts from HLA-matched related (n = 677; 61%), HLA-mismatched related (n = 78; 7%), HLA-matched unrelated (n = 252; 23%), and HLA-mismatched unrelated (n = 103; 9%) donors between 2000 and 2016. Ninety percent of transplants were performed in the last decade. Eight-five percent of patients received ≥20 transfusions and 88% were inadequately chelated. All patients received myeloablative-conditioning regimen. Overall and event-free survival were highest for patients aged ≤6 years and after HLA-matched related and HLA-matched unrelated donor transplantation. The 5-year probabilities of overall survival for patients aged ≤6 years, 7 to 15 years, and 16 to 25 years, adjusted for donor type and conditioning regimen were 90%, 84%, and 63%, respectively (P < .001). The corresponding probabilities for event-free survival were 86%, 80%, and 63% (P < .001). Overall and event-free survival did not differ between HLA-matched related and HLA-matched unrelated donor transplantation (89% vs 87% and 86% vs 82%, respectively). Corresponding probabilities after mismatched related and mismatched unrelated donor transplantation were 73% vs 83% and 70% vs 78%. In conclusion, if transplantation is considered as a treatment option it should be offered early (age ≤6 years). An HLA-matched unrelated donor is a suitable alternative if an HLA-matched relative is not available.

Allogeneic stem cell transplantation is a cure for patients suffering from thalassemia major (TM). Historically, patients were limited by the selection of donors, while the advancement of haploidentical stem cell transplantation (haplo-SCT) has greatly expanded the donor pool. However, the outcomes of haplo-SCT in TM recipients vary between different programs. In this study, we retrospectively studied 73 pediatric TM patients (median age, 7 years; range, 3 to 14 years) who underwent haplo-cord transplantation. Both the estimated overall survival and transfusion-free survival were 95.26% (CI 95.77% to 96.23%). Neither primary nor secondary graft failures were observed. The median follow-up period was 811 days (range, 370 to 1433 days). Median neutrophil and platelet engraftment times were 22 days (range, 8 to 48 days) and 20 days (range, 8 to 99 days), respectively. Acute graft-versus-host disease (aGVHD) was observed in 52% of patients and of these, 25% developed grade III to IV aGVHD. Cord blood engraftment was associated with delayed immune recovery and increased aGVHD severity. Viral DNAemia occurred in a relatively high proportion of patients but only 7% of patients developed CMV disease, while another 7% of patients had post-transplantation lymphoproliferative disorder. Long-term complication outcomes were good. Only one patient developed extensive chronic GVHD. No surviving patients were reliant on blood transfusion by the time this manuscript was submitted. This is one of the largest studies on the outcomes of pediatric TM patients who received stem cell transplantations from alternative donors. The haplo-cord program is safe and practical for TM patients that do not have matched donors.

Accurate T cell receptor repertoire profiling has provided novel biological and clinical insights in widespread immunological settings; however, there is a lack of reference materials in the community that can be used to calibrate and optimize the various experimental systems in different laboratories. In this study, we designed and synthesized 611 T cell receptor (TCR) beta chain (TRB) templates and used them as reference materials to optimize the multiplex PCR experimental system to enrich the TRB repertoire. We assessed the stability of the optimized system by repeating the experiments in different batches and by remixing the TRB templates in different ratios. These TRB reference materials could be used as independent positive controls to assess the accuracy of the experimental system, and they can also be used as spike-in materials to calibrate the residual biases of the experimental system. We then used the optimized system to detect the minimal residual disease of T cell acute lymphoblastic leukemia and showed a higher sensitivity compared with flow cytometry. We also interrogated how chemotherapy affected the TCR repertoire of patients with B-cell acute lymphoblastic leukemia. Our result shows that high-avidity T cells, such as those targeting known pathogens, are largely selected during chemotherapy, despite the global immunosuppression. These T cells were stimulated and emerged at the time of induction treatment and further expanded during consolidation treatment, possibly to fight against infections. These data demonstrate that accurate immune repertoire information can improve our understanding of the adaptive immunity in leukemia and lead to better treatment management of the patients.

Abstract Dynamic behaviour of frequency is crucial for power system operation and control. Several frequency response models have been proposed to reveal frequency dynamics from different aspects. A comprehensive software package incorporating major frequency response models is needed for analysis and control of power system frequency dynamics. In this paper, an approach for developing a programmable and open software package for frequency response studies is proposed. The framework of the package is extendable with reduced frequency response models. Essential models for frequency response study are included, e.g., generator, load, and under-frequency load shedding (UFLS). The provided application program interfaces (APIs) enable simulation with high-level languages by calling dynamic link library and makes the package programmable. An advanced application module is developed for quantitative assessment of transient frequency deviation. APIs can also be used for model extension and secondary development. To demonstrate the usage of the package, several examples are illustrated to explain how to perform simulations with the package, and to perform advanced applications using scripting with the provided APIs.

Accompanying the continuous increase in wind power penetration, the power system inertia is reduced, and the system frequency regulation performance deteriorates. Wind turbine generators are required to participate in primary frequency regulation (PFR) to support system frequency. Here, the PFR capability of the widely-used doubly-fed induction generator (DFIG) is evaluated to estimate the participation of the DFIG in system frequency control. The frequency regulation model of the DFIG is established and briefly discussed. The equivalent PFR droop coefficient is then deduced from the model using a small signal increment method to evaluate the DFIG’s PFR capability. Key factors affecting the equivalent droop coefficient are studied, and the droop control is optimized to keep the equivalent droop coefficient in the desired range. The proposed method is verified utilizing a provincial power grid model of China.

BACKGROUND:γ-Glutamyl hydrolase (GGH) regulates intracellular folates and antifolates such as methotrexate (MTX) for proper nucleotide biosynthesis and antifolate-induced cytotoxicity, respectively. In addition to genetic polymorphism and karyotypic abnormalities, methylation of CpG island 1 (CpG1) in the promoter region is found to modulate GGH activity by reducing GGH mRNA expression in acute lymphoblastic leukemia (ALL) cells. We aim to investigate methylation status of two CpG islands (CpG1 and CpG2) in the GGH promoter region in pediatric patients with ALL and acute myelogenous leukemia (AML). METHODS:70B-ALL, 29 AML, 10 ITP (idiopathic thrombocytopenic purpura) and 40 healthy children are recruited in the present study. MS-HRM (methylation-sensitive high-resolution melting) and bisulfite sequencing PCR (BSP) are used to detect methylation change and its level in CpG1 and CpG2 in the GGH promoter region. GGH mRNA expression is quantified by real-time PCR. Correlation between CpG island methylation and GGH mRNA expression is assessed by statistical software. RESULTS:Methylations of CpG1 are detected in leukemia cells samples obtained from 30.9% (21/68) of patients with ALL and 20.7% (6/29) of patients with AML. These methylations are not detected in the controls. Methylations of CpG2 are detected in leukemia cell samples obtained from 44.1% (30/68) of the ALL patients and 37.9% (11/29) of the AML patients. These percentages are significantly higher than that observed in the control cell samples: 6.0% (3/50) (Fisher's exact test, P = 0.000). The abundance of CpG1 methylation in all leukemia cell samples is classified as Grade I (methylation level is less than 10%) and the abundance of CpG2 methylation in leukemia cell samples is classified in separate grades. Our results indicate that methylation of CpG1 or hypermethylation (the methylation level is greater than 10%) of CpG2 could significantly reduce GGH mRNA expression in leukemia cells from the ALL and AML patients (ALL-CpG1: t = 4.632, P = 0.000; ALL-CpG2: t = 3.250, P = 0.006; AML-CpG1: t = -2.254, P = 0.037; AML-CpG2: t = 1.328, P = 0.202). CONCLUSION:Either methylation of CpG1 or hypermethylation of CpG2 in GGH promoter region can significantly reduce GGH mRNA expression in pediatric patients with acute leukemia, which can improve the response to treatment.

Acute B lymphoblastic leukemia (B-ALL) is one of most common types of childhood cancer worldwide and chemotherapy is the main treatment approach. Despite good response rates to chemotherapy regiments, many patients eventually relapse and minimal residual disease (MRD) is the leading risk factor for relapse. The evolution of leukemic clones during disease development and treatment may have clinical significance. In this study, we performed immunoglobulin heavy chain (IGH) repertoire high throughput sequencing (HTS) on the diagnostic and post-treatment samples of 51 pediatric B-ALL patients. We identified leukemic IGH clones in 92.2% of the diagnostic samples and nearly half of the patients were polyclonal. About 1/3 of the leukemic clones have correct open reading frame (ORF) in the complementarity determining region 3 (CDR3) of IGH, which demonstrates that the leukemic B cells were in the early developmental stage. We also demonstrated the higher sensitivity of HTS in MRD detection and investigated the clinical value of using peripheral blood in MRD detection and monitoring the clonal IGH evolution. In addition, we found leukemic clones were extensively undergoing continuous clonal IGH evolution by variable gene replacement. Dynamic frequency change and newly emerged evolved IGH clones were identified upon the pressure of chemotherapy. In summary, we confirmed the high sensitivity and universal applicability of HTS in MRD detection. We also reported the ubiquitous evolved IGH clones in B-ALL samples and their response to chemotherapy during treatment.

Harmonic adaptability (HA) capability is required for large-scale onshore and offshore wind turbines (WTs) connected to the grid. To ensure that the distortion of the harmonic voltage at the grid access point generated by grid simulator is in accordance with the required value, this paper proposes an on-site HA remote testing method for offshore WTs to eliminate submarine cable effects. The deviation compensation method detects the integer harmonic voltage distortion based on instantaneous reactive power theory, and the deviation from the required value is compensated by series active power filter. In order to further reduce the capacity of the designed device, integer harmonics close to the resonant frequency are suppressed by the selective harmonic damping (SHD) method initially. Owing to the attenuation of extreme amplification, the deviation determining the equipment capacity is decreased correspondingly. As a small synthesized impedance working for the selected frequency can suppress the amplification significantly, a low power ratings design for the SHD method can be achieved, and undesired resonance can be avoided. Simulation results indicate that the proposed method can make the harmonic distortion within the error tolerance.

With the increasing occurrence of extreme weather events, the short circuit and line-breaking faults in transmission lines caused by line galloping have been threatening the security operation of power systems. These faults are also hard to be simulated with current simulation tools. A numerical simulation approach of power systems is presented to simulate the clustered, cascading faults of long-timescale caused by line-galloping events. A simulation framework is constructed in which large numbers of fault scenarios are simulated to reflect the randomness of line galloping. The interaction mechanism between power system operation states and line galloping processes is revealed and simulated by the solution of differences of timescales and parameters. Based on Power System Simulator/Engineering (PSS/E), an extended software package for line galloping simulation is developed with Python, which extends the functionalities of the PSS/E in power system simulation. An example is given to demonstrate the feasibility of the proposed simulation method.

Since the dead-zone fault in substations often has a relatively long removal time, it may damage the insulation of power equipment and even threaten the stability of the power system. In this paper, the movement of the dead-zone fault electric arc in a 220-kV substation is investigated. The arc chain model for the dead-zone fault electric arc is developed; the influences of electromagnetic force, thermal buoyancy, and the air resistance stressed on the electric arc are comprehensively considered. The electric arc velocity and displacement are computed. Then, the spreading characteristics of the dead-zone electric arc under various conditions are studied. The spreading trend of the dead-zone fault electric arc is summarized. Finally, measures to inhibit the spreading of the electric arc are suggested. The study indicates that the movement of the electric arc in the dead zone during the early stage is primarily influenced by the electromagnetic force resulting from the overpass and conductor, and the arc is concave and has an irregular trajectory. The inclination angle of the conductor significantly affects the direction of the electromagnetic force. If the conductor is laid horizontally, the electric arc is subjected to a smaller force. The electromagnetic force stressed on the electric arc is mainly attributed to the fault phase conductor and the electric arc body itself, whereas those from the other phase conductors are minor. The initial position of the arc root has a certain impact on the movement of the electric arc. The use of the insulating materials restricts the arc root movement. [ABSTRACT FROM AUTHOR]