Search

We initiate the study of locally differentially private (LDP) learning with public features. We define semi-feature LDP, where some features are publicly available while the remaining ones, along with the label, require protection under local differential privacy. Under semi-feature LDP, we demonstrate that the mini-max convergence rate for non-parametric regression is significantly reduced compared to that of classical LDP. Then we propose HistOfTree, an estimator that fully leverages the information contained in both public and private features. Theoretically, HistOfTree reaches the mini-max optimal convergence rate. Empirically, HistOfTree achieves superior performance on both synthetic and real data. We also explore scenarios where users have the flexibility to select features for protection manually. In such cases, we propose an estimator and a data-driven parameter tuning strategy, leading to analogous theoretical and empirical results.

Ji Cheng Zhang, Jin Hua Wang, Jia Lin, Guo Ming Su, Yi Lin Shen, Qi Wei Guo, Jia Jing Cai, Jun Yi Liu, Ke Xin Jia, Ding Zhi Fang Department of Biochemistry and Molecular Biology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, People’s Republic of ChinaCorrespondence: Ding Zhi Fang, Department of Biochemistry and Molecular Biology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, 610041, People’s Republic of China, Email dzfang@scu.edu.cnAim: To explore anthropometric, metabolic and dietary factors associated with and their interplays with the Val66Met polymorphism at brain-derived neurotrophic factor (BDNF) gene (Bdnf) on serum BDNF levels in adolescents.Methods: Serum BDNF levels were quantified using an enzyme-linked immunosorbent assay in 644 high school students (278 males/366 females). A polymerase chain reaction and restriction fragment length polymorphism assay were utilized for Bdnf Val66Met genotyping followed by verification using DNA sequencing. Serum levels of metabolic characteristics were assayed by routine methods. The intake of macro and micronutrients was collected by a three-day food record.Results: Serum BDNF levels were found to be significantly different in the subjects with different genotypes of Bdnf Val66Met (Val/Val homozygotes, 60.05 ± 28.07 ng/mL vs Val/Met heterozygotes, 56.37 ± 29.34 ng/mL vs Met/Met homozygotes, 51.32 ± 24.54 ng/mL, p = 0.022). Among the 36 tested variables, waist–hip ratio (WHR) (β = − 0.163, p < 0.001), iodine intake (β = 0.132, p = 0.001), heart rate (β = 0.108, p = 0.005), high-density lipoprotein cholesterol (HDL-C) (β = 0.098, p = 0.011) and dietary fiber intake (β = 0.082, p = 0.084) were the predictor of serum BDNF levels, while SBP (β = 0.097, p = 0.013) and WHR (β = 0.091, p = 0.021) were related with Bdnf Val66Met. Moreover, WHR was observed to play a partial mediating role in the relations

Robust road segmentation is a key challenge in self-driving research. Though many image-based methods have been studied and high performances in dataset evaluations have been reported, developing robust and reliable road segmentation is still a major challenge. Data fusion across different sensors to improve the performance of road segmentation is widely considered an important and irreplaceable solution. In this paper, we propose a novel structure to fuse image and LiDAR point cloud in an end-to-end semantic segmentation network, in which the fusion is performed at decoder stage instead of at, more commonly, encoder stage. During fusion, we improve the multi-scale LiDAR map generation to increase the precision of the multi-scale LiDAR map by introducing pyramid projection method. Additionally, we adapted the multi-path refinement network with our fusion strategy and improve the road prediction compared with transpose convolution with skip layers. Our approach has been tested on KITTI ROAD dataset and has competitive performance., Comment: Accepted by Multimedia Tools and Applications

Support Vector Regression (SVR) has been a long standing problem in machine learning, and gains its popularity on various computer vision tasks. In this paper, we propose a structured support vector regression framework by extending the max-margin principle to incorporate spatial correlations among neighboring pixels. The objective function in our framework considers both label information and pairwise features, helping to achieve better cross-smoothing over neighboring nodes. With the bundle method, we effectively reduce the number of constraints and alleviate the adverse effect of outliers, leading to an efficient and robust learning algorithm. Moreover, we conduct a thorough analysis for the loss function used in structured regression, and provide a principled approach for defining proper loss functions and deriving the corresponding solvers to find the most violated constraint. We demonstrate that our method outperforms the state-of-the-art regression approaches on various testbeds of synthetic images and real-world scenes.

Conditional random field methods (CRFs) have gained popularity for image labeling tasks in recent years. In this paper, we describe an alternative discriminative approach, by extending the large margin principle to incorporate spatial correlations among neighboring pixels. In particular, by explicitly enforcing the submodular condition, graph-cuts is conveniently integrated as the inference engine to attain the optimal label assignment efficiently. Our approach allows learning a model with thousands of parameters, and is shown to be capable of readily incorporating higher-order scene context. Empirical studies on a variety of image datasets suggest that our approach performs competitively compared to the state-of-the-art scene labeling methods.

Polymer nanowires were found to respond to external perturbations and to undergo transfiguration upon exposure to the irradiation of high-flux electron beams. The phenomenon is general, observable in the nanowires of conjugated and nonconjugated polymers with linear and hyperbranched structures. The transfiguration ceased to occur after the nanowires had been annealed at temperatures higher than the glass transition temperatures of the polymers. The phenomenon is rationalized to be associated with the residual internal stress in the nanowires that is relieved through the electron-beam irradiation and/or thermal annealing. This work thus offers cautionary advice that a proper annealing treatment should be exercised, if one wishes to fabricate polymer nanostructures and miniature devices with reliable stability and durable performance.

Poly(N-isopropylacrylamide) was labelled using a fluorogen with an aggregation-induced emission feature by direct polymerization; the label served as a fluorogenic probe that reveals. ne details in the thermal transitions in the aqueous solution of the polymer; the working mode was readily tuned between non-monotonic and monotonic by changing the labelling degree of the polymer.

A new fluorescence technique for monitoring layer-by-layer self-assembling processes of polycations and polyanions is developed in this work. The fluorescent probe is a fluorogenic dye named 1,1-bis[p-(diettlylaminomethyl)phenyl]-2,3,4,5-tetraphenylsilole (A(2)HPS). Whereas fluorescence of a "normal" fluorophore is often quenched by aggregate formation, the protonated salt of A(2)HPS, i.e., [H(2)A(2)HPS](2+), emits strong light in the Suspensions of its nanoaggregates and in the solid films of its blends with poly(diallyldimethylammonium chloride) (PDDAC), thanks to its novel aggregation-induced emission (AIE) characteristics. When ([H(2)A(2)HPS](2+)+PDDAC) cations and poly(styrenesulfonate) (PSS) anions were used to fabricate thin films via layer-by-layer deposition processes on quartz and glass substrates, the emission intensity of [H(2)A(2)HPS](2+) showed linear relationship with the number of ([H(2)A(2)HPS](2+)+ PDDAC)/PSS bilayers, due to the uniform co-deposition of [H(2)A(2)HPS](2+) cations into the PDDAC/PSS bilayers. This proves that the AIE fluorophore is an excellent probe for monitoring the layer-by-layer self-assembling processes of the polyelectrolytes on various substrates. (C) 2008 Elsevier B.V. All rights reserved.

Acetylenic monomers containing highly polar functional groups, especially those with active hydrogen atoms, have been difficult to polymerize because their toxic interactions with transition metal complexes deactivate catalyst systems. In this work. we Succeeded in direct polymerizations of a series of highly polar phenylacetylene derivatives. The polymerizations of 4-ethynylbenzoic acid (1), 4-hydroxybutyl 4-ethynylbenzoate (2), 6-(4-ethynylphenoxy)hexanoic acid (3), 4-ethynylaniline (4), and 1-ethynyl-4-nitrobenzene (5) catalyzed by organorhodium complexes afforded corresponding polymers (P1-P5) of high molecular weight (M-w as high as 489 500) and low polydispersity index (M-w/M-n as low as 1.03). The structures of the polymers were characterized spectroscopically. Treatments by base and acid readily transformed neutral polymers P1 and P4 to polyelectrolytes P1(-) and P4(+), respectively. Simple mixing of the conjugated polyelectrolytes with multiwalled carbon nanotubes (MWNTs) afforded polyacetylene/MWNT nanohybrids with water solubility Of LIP to 316 mg/L. The hybrids were facilely decorated by metal (oxide) nanoparticles, furnishing multicomponent composites of P1(-)/MWNT/Ag, P4(+)/MWNT/Ag, and P4(+)/MWNT/ZnO.

This paper presents a novel discriminative approach for pave-ment scene understanding and obstacle detection in real-world images. It overcomes the heavy constraints in previous systems such as a simple background, a specic obstacle, etc. The approach we exploited extends the bundle method to incorporate pairwise correlations among neighboring pixels, and adopts graph-cuts as the inference engine to attain the approximation efficiently. A set of robust features on both local and multi-scale level is also introduced that captures the general statistical properties of pavements and obstacles. The proposed approach is validated on real-world image database, and outperforms the current state-of-the-art visioned-based methods

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Includes bibliographical references (p. 127-129)., Oil flows through ring/groove interface play a critical role in oil transport among different regions the piston ring pack of internal combustion engines. This thesis work is intended to improve the understanding and modeling capability on this important oil transport mechanism for better analysis in engine oil consumption. A model incorporating ring dynamics, gas flow, and oil flow was developed to study oil transport in the piston ring-pack system. The major new element of this new model is adaptation of a mass conserved two phase oil/gas flow sub-model. Doing so, the present model can describe the oil flows through the ring/groove interface in a consistent manner. The model was applied to a heavy duty diesel engine at maximum power condition and to a SI engine at engine-braking and moderate load conditions. In the diesel application, the model demonstrates that oil can be released through the second ring/groove interface during second ring flutter and ring/groove interface plays positive role in reducing oil consumption and oil residence time. On the other hand, oil can be pumped up into the top ring groove and combustion chamber through the top ring/groove interface at engine braking conditions in the SI engine. Both applications show that oil flow rate through ring/groove interface is most prominent during the period of the engine cycle when the ring motion and gas pressure exhibit dynamic behaviors, and thus show that the coupling of the ring dynamics and gas/oil flows in the present model is essential to predict the oil pumping through ring/groove interface., by Ke Jia., S.M.

A group of triphenylamine-functionalized polyacetylenes (TPA-PAs) were synthesized using [Rh(nbd)Cl](2) as catalyst in high yields (up to 93\%). The polymers were characterized by NMR, IR, UV, PL, and CV analyses. The TPA pendants endowed the polymers with desirable redox activity and high photoconductivity. When an electron-withdrawing formyl group was attached to the TPA unit, the resultant polymer (P3) displayed solvatochromism. Simply mixing the polymers with multiwalled carbon nanotubes (MWNTs) in appropriate solvents resulted in the formation of TPA-PA/MWNT hybrids. With the aid of the polymer bearing styryl-TPA pendant (P2), similar to 21\% of MWNTs were loaded into the hybrid and a solubility of MWNTs in dichloromethane as high as 720 mg/L was achieved, which is among the highest solubilities of MWNTs in organic solvents. The great solvating power of the TPA-PAs for the MWNTs is attributed to the polymer wrapping processes aided by the additive effects of pi-pi electronic interaction and donor-acceptor (D-A) complexation. This is the first report demonstrating the involvement of D-A interaction in the solubilization of MWNTs by a conjugated polymer. A single-layer photoreceptor with P3/MWNT hybrid as charge-generation material displayed a photosensitivity as high as similar to 9091 mm(2)/mW . s, which is the highest value recorded for a polyacetylene-based device. The excellent photoconductivity is ascribed to the efficient charge separation in the D-A system and the fast transport of the photogenerated holes and electrons in the polymer and MWNT, respectively.

A group of ferrocene-containing poly(phenylacetylene)s (PPAs) with different alkyl spacers were synthesized by using organorhodium complexes [Rh(diene)Cl](2) and Rh+(nbd)[C6H5B-(C6H5)(3)] as catalysts. With the aid of pi-pi interactions between the walls of carbon nanotubes (CNTs) and the PPA skeleton together with the ferrocene pendants, the polymer (P1, P2(5) and P2(10)) chains effectively wrapped round the shells of both single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs). The "additive effect" of the PPA skeleton and the ferrocene pendants in dispersing the SWNTs and MWNTs resulted in the generation of highly soluble hybrids. The solubilities of P1-functionalized SWNTs and MWNTs in tetrahydrofuran (THF) are up to 633 mg/L and 967 mg/L, respectively. They are much higher than the solubilities of M1-modified SWNTs and MWNTs, which are only 167 mg/L and 133 mg/L in THF. The results indicate the existence of a powerful polymer effect on dispersing CNTs. The high solubilities of the hybrids in organic solvents allowed us to fabricate high-quality and large-area films. Meanwhile, the desirable loading of ferrocene-containing PPAs onto the CNTs offered polymer/CNTs hybrids with multiple redox centers and ferrocene-featured electrochemical properties. The P1/MWNT hybrid exhibits evident optical-limiting properties. At high incident laser fluence, the optical-limiting power of P1/MWNT is higher than that of C-60, a well-known optical limiter. Thermal analyses indicate that the decomposition temperatures (T-d, the temperature at which a sample loses its 5\% weight) for P1 and P1/MWNT are 342 and 346 degrees C, respectively, much higher than that for PPA (225 degrees C). Thus the attachment of a ferrocene pendant to a PPA backbone, followed by hybridization with CNTs, improved the thermal stability. Upon pyrolysis, both the polymer and the polymer/CNTs hybrid gave rise to superparamagnetic ceramics; the saturation magnetizations (M-s) of the cer

4-[3-(1-Pyrenyl)propylcarbonyloxy]-1-butyne (PyB) and 4-ferrocenylcarbonyloxy-1-butyne (FcB) were effectively polymerized by zwitterionic rhodium complex Rh+(nbd)[C6H5B-(C6H5)(3)], giving corresponding polymers PPyB and PFcB with high molecular weights (M-w up to 33300) in high yields (up to 83\%). The polymers are excellent solvating agents in making carbon nanotubes (CNTs) soluble in common organic solvents. The salvation is aided by the wrapping or coating of CNTs by the polymers through strong electronic interactions between the aromatic pendants and the CNT shells. A pronounced "polymer effect" was observed in the solvating process: the polymers showed much higher solvating power than their monomers. The polymers endowed the CNTs with functional properties: the PPyB/CNT and PFcB/CNT hybrids were light-emitting and redox-active, respectively.

It has been a challenge to synthesize thiol-functionalized polyacetylenes because of the poisoning effect of mercapto group on the early transition-metal catalysts. Rhodium complexes such as [Rh(cod)Cl](2) can catalyze the polymerizations but the products are insoluble and intractable. In this work, we tackled this challenge. Sulfur-containing polyacetylenes with macroscopic processability were successfully synthesized by separating thiol pendant from polyene backbone with a flexible spacer (in PI), capping free mercapto group with acetyl or alkyl group (in P2 or P3), and using a zwitterionic complex Rh+[eta(6)-C6H5(nbd)B-(C6H5)(3)] as catalyst. The soluble polymers were characterized by NMR, IR, UV, PL, and TGA analyses. Due to the specific interactions between thiol group and zinc cation, ZnO nanoparticles were chemisorbed onto the surfaces of polymer films, as verified by AFM analysis. Polymer P2 and ZnO nanoparticles could be readily hybridized by simply mixing the two components in an organic solvent such as chloroform, THF, or DMF. SEM images revealed that the morphology of the film cast from the solution of the P2/ZnO hybrid was dominated by well-dispersed nanoparticles and smooth surface.

In a micro-grid, due to potential reverse output profiles of the Renewable Energy Source (RES) and the load, energy storage devices are employed to achieve high self-consumption of RES and to minimize power surplus flowing back into the main grid. This paper proposes a variable charging/discharging threshold method to manage energy storage system. And an Adaptive Intelligence Technique (AIT) is put forward to raise the power management efficiency. A battery-ultra-capacitor hybrid energy storage system (HESS) with merits of high energy and power density is used to evaluate the proposed method with onsite measured RES output data. Compared with the PSO algorithm based on the precise predicted data of the load and the RES, the results show that the proposed method can achieve better load smoothing and maximum self-consumption of the RES without the requirement of precise load and RES forecasting.

Active islanding detection methods are generally employed for grid-connected inverter-based Distributed Generation (DG). However, there might be mutual influences and power quality issues caused by the disturbance signal when multiple inverters are involved. To address those problems, this paper analyzes the potential failure mechanism of the f-Q (frequency-reactive power) drifting active method in multiple-DG situations. Then, a novel high frequency transient injection based islanding detection method that is suitable for both single and multiple-DGs is proposed. Compared with the conventional injection methods, a high frequency impedance model for DG is provided for better theoretical analysis. By means of the intermittent Time Domain Low Voltage Condition (TDLVC) injection control, this method can achieve good accuracy and reduce disturbances to power system. 

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals. 

Distributed generations (DGs) in the distribution systems are connected into the buses using power electronic converters. During fault, it is challenging to provide a constant impedance model for DGs in the system frequency due to the variable converter control strategies. System frequency impedance measurement based fault locations can be influenced by the converters’ fault behaviour. This study addresses this problem by proposing a wide-area high-frequency impedance comparison based fault location technique. The high-frequency impedance model of DG is provided. Based on the constant DG impedance model in high-frequency range, the faulted line sections can be distinguished by comparing the measured impedance differences without requiring the exact distribution system parameters. Simulation results show that the proposed wide-area transient measurements based fault location method can provide accurate faulted sections in the distribution systems with DGs regardless of the load and DG output variations, measurement noise, unbalanced loads and islanding operations.

A new Active Impedance Estimation (AIE) based protection strategy which is suitable for utilization in a DC zonal marine power distribution system is presented. This method uses two triangular current "spikes" injections for system impedance estimation and protection when faults are detected. By comparing the estimated impedance with the pre-calibrated value, the fault location can be predicted and fault can be isolated without requiring communication between two injection units. Using co¬operated double injections and line current measurement (directional fault detection), faults in the system with same impedance and different fault positions can be distinguished, located and isolated. The proposed method is validated using experimental test results derived from a 30kW, 400V, twin bus DC marine power system demonstrator. The experimental tests were applied to both faults during normal operation and faults that occur during system restoration.

A portable injection unit for Active Impedance Estimation (AIE) is built and tested in a DC zonal marine power distribution system to provide useful information for system protection and restoration. The portable unit generates current “spikes” and injects them into the system once short circuit faults are detected (by measuring the system voltage drop). The faulted system impedance can be estimated by AIE and comparing the estimated impedance with the pre-calibrated value, the fault location can be determined. The proposed method does not rely on system fault transient information or communication from the remote-end measurement and offers fast and accurate fault location in DC marine distribution systems. The proposed method has been tested and validated on a 750V, 2 MW twin bus DC Commercial Test Facility with the system both de-energised and energised.

Active islanding detection methods are generally employed for grid-connected inverter-based Distributed Generation (DG). However, there might be mutual influences and power quality issues caused by the disturbance signal when multiple inverters are involved. To address those problems, this paper analyzes the potential failure mechanism of the f-Q (frequency-reactive power) drifting active method in multiple-DG situations. Then, a novel high frequency transient injection based islanding detection method that is suitable for both single and multiple-DGs is proposed. Compared with the conventional injection methods, a high frequency impedance model for DG is provided for better theoretical analysis. By means of the intermittent Time Domain Low Voltage Condition (TDLVC) injection control, this method can achieve good accuracy and reduce disturbances to power system. 

In a micro-grid, due to potential reverse output profiles of the Renewable Energy Source (RES) and the load, energy storage devices are employed to achieve high self-consumption of RES and to minimize power surplus flowing back into the main grid. This paper proposes a variable charging/discharging threshold method to manage energy storage system. And an Adaptive Intelligence Technique (AIT) is put forward to raise the power management efficiency. A battery-ultra-capacitor hybrid energy storage system (HESS) with merits of high energy and power density is used to evaluate the proposed method with onsite measured RES output data. Compared with the PSO algorithm based on the precise predicted data of the load and the RES, the results show that the proposed method can achieve better load smoothing and maximum self-consumption of the RES without the requirement of precise load and RES forecasting.

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals. 

Distributed generations (DGs) in the distribution systems are connected into the buses using power electronic converters. During fault, it is challenging to provide a constant impedance model for DGs in the system frequency due to the variable converter control strategies. System frequency impedance measurement based fault locations can be influenced by the converters’ fault behaviour. This study addresses this problem by proposing a wide-area high-frequency impedance comparison based fault location technique. The high-frequency impedance model of DG is provided. Based on the constant DG impedance model in high-frequency range, the faulted line sections can be distinguished by comparing the measured impedance differences without requiring the exact distribution system parameters. Simulation results show that the proposed wide-area transient measurements based fault location method can provide accurate faulted sections in the distribution systems with DGs regardless of the load and DG output variations, measurement noise, unbalanced loads and islanding operations.

A new Active Impedance Estimation (AIE) based protection strategy which is suitable for utilization in a DC zonal marine power distribution system is presented. This method uses two triangular current "spikes" injections for system impedance estimation and protection when faults are detected. By comparing the estimated impedance with the pre-calibrated value, the fault location can be predicted and fault can be isolated without requiring communication between two injection units. Using co¬operated double injections and line current measurement (directional fault detection), faults in the system with same impedance and different fault positions can be distinguished, located and isolated. The proposed method is validated using experimental test results derived from a 30kW, 400V, twin bus DC marine power system demonstrator. The experimental tests were applied to both faults during normal operation and faults that occur during system restoration.

A portable injection unit for Active Impedance Estimation (AIE) is built and tested in a DC zonal marine power distribution system to provide useful information for system protection and restoration. The portable unit generates current “spikes” and injects them into the system once short circuit faults are detected (by measuring the system voltage drop). The faulted system impedance can be estimated by AIE and comparing the estimated impedance with the pre-calibrated value, the fault location can be determined. The proposed method does not rely on system fault transient information or communication from the remote-end measurement and offers fast and accurate fault location in DC marine distribution systems. The proposed method has been tested and validated on a 750V, 2 MW twin bus DC Commercial Test Facility with the system both de-energised and energised.

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals. 

This thesis presents an investigation into impedance based fault location methods which directly use the fault transient as an excitation source to provide fast and accurate fault locations in small distribution systems such as the modem marine and aircraft power systems which have Integrated Power System (IPS) configuration. Fast and accurate fault location on un-exposed power distribution lines is of vital importance to expedite service restoration and improving the reliability of the power system. Two fault location algorithms are developed: the single-ended method and the double-ended method. The singled-ended algorithm which captures current and voltage waveforms from one end of the distribution cable estimates the fault locations using an iteration calculation. The double-ended method has a simple algorithm and is robust to different fault situations but requires additional data measured from the remote end of the cable. Both simulation and experimental tests have been done and the results are good enough to validate that the developed methods can locate fault positions using a 12ms window and otter an accuracy of within 1m in the proposed distribution system. The advantages and disadvantages of the proposed fault location methods are investigated under different fault situations. The possibility of employing the two methods in protection of faults in a marine power system is demonstrated. Due to the special characteristics of the marine power system, an active method which simply involves adding an IGBT switch is proposed for the earth fault protection.

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals. 

In a micro-grid, due to potential reverse output profiles of the Renewable Energy Source (RES) and the load, energy storage devices are employed to achieve high self-consumption of RES and to minimize power surplus flowing back into the main grid. This paper proposes a variable charging/discharging threshold method to manage energy storage system. And an Adaptive Intelligence Technique (AIT) is put forward to raise the power management efficiency. A battery-ultra-capacitor hybrid energy storage system (HESS) with merits of high energy and power density is used to evaluate the proposed method with onsite measured RES output data. Compared with the PSO algorithm based on the precise predicted data of the load and the RES, the results show that the proposed method can achieve better load smoothing and maximum self-consumption of the RES without the requirement of precise load and RES forecasting.

Active islanding detection methods are generally employed for grid-connected inverter-based Distributed Generation (DG). However, there might be mutual influences and power quality issues caused by the disturbance signal when multiple inverters are involved. To address those problems, this paper analyzes the potential failure mechanism of the f-Q (frequency-reactive power) drifting active method in multiple-DG situations. Then, a novel high frequency transient injection based islanding detection method that is suitable for both single and multiple-DGs is proposed. Compared with the conventional injection methods, a high frequency impedance model for DG is provided for better theoretical analysis. By means of the intermittent Time Domain Low Voltage Condition (TDLVC) injection control, this method can achieve good accuracy and reduce disturbances to power system. 

Distributed generations (DGs) in the distribution systems are connected into the buses using power electronic converters. During fault, it is challenging to provide a constant impedance model for DGs in the system frequency due to the variable converter control strategies. System frequency impedance measurement based fault locations can be influenced by the converters’ fault behaviour. This study addresses this problem by proposing a wide-area high-frequency impedance comparison based fault location technique. The high-frequency impedance model of DG is provided. Based on the constant DG impedance model in high-frequency range, the faulted line sections can be distinguished by comparing the measured impedance differences without requiring the exact distribution system parameters. Simulation results show that the proposed wide-area transient measurements based fault location method can provide accurate faulted sections in the distribution systems with DGs regardless of the load and DG output variations, measurement noise, unbalanced loads and islanding operations.

A new Active Impedance Estimation (AIE) based protection strategy which is suitable for utilization in a DC zonal marine power distribution system is presented. This method uses two triangular current "spikes" injections for system impedance estimation and protection when faults are detected. By comparing the estimated impedance with the pre-calibrated value, the fault location can be predicted and fault can be isolated without requiring communication between two injection units. Using co¬operated double injections and line current measurement (directional fault detection), faults in the system with same impedance and different fault positions can be distinguished, located and isolated. The proposed method is validated using experimental test results derived from a 30kW, 400V, twin bus DC marine power system demonstrator. The experimental tests were applied to both faults during normal operation and faults that occur during system restoration.

A portable injection unit for Active Impedance Estimation (AIE) is built and tested in a DC zonal marine power distribution system to provide useful information for system protection and restoration. The portable unit generates current “spikes” and injects them into the system once short circuit faults are detected (by measuring the system voltage drop). The faulted system impedance can be estimated by AIE and comparing the estimated impedance with the pre-calibrated value, the fault location can be determined. The proposed method does not rely on system fault transient information or communication from the remote-end measurement and offers fast and accurate fault location in DC marine distribution systems. The proposed method has been tested and validated on a 750V, 2 MW twin bus DC Commercial Test Facility with the system both de-energised and energised.

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals. 

This thesis presents an investigation into impedance based fault location methods which directly use the fault transient as an excitation source to provide fast and accurate fault locations in small distribution systems such as the modem marine and aircraft power systems which have Integrated Power System (IPS) configuration. Fast and accurate fault location on un-exposed power distribution lines is of vital importance to expedite service restoration and improving the reliability of the power system. Two fault location algorithms are developed: the single-ended method and the double-ended method. The singled-ended algorithm which captures current and voltage waveforms from one end of the distribution cable estimates the fault locations using an iteration calculation. The double-ended method has a simple algorithm and is robust to different fault situations but requires additional data measured from the remote end of the cable. Both simulation and experimental tests have been done and the results are good enough to validate that the developed methods can locate fault positions using a 12ms window and otter an accuracy of within 1m in the proposed distribution system. The advantages and disadvantages of the proposed fault location methods are investigated under different fault situations. The possibility of employing the two methods in protection of faults in a marine power system is demonstrated. Due to the special characteristics of the marine power system, an active method which simply involves adding an IGBT switch is proposed for the earth fault protection.

In a micro-grid, due to potential reverse output profiles of the Renewable Energy Source (RES) and the load, energy storage devices are employed to achieve high self-consumption of RES and to minimize power surplus flowing back into the main grid. This paper proposes a variable charging/discharging threshold method to manage energy storage system. And an Adaptive Intelligence Technique (AIT) is put forward to raise the power management efficiency. A battery-ultra-capacitor hybrid energy storage system (HESS) with merits of high energy and power density is used to evaluate the proposed method with onsite measured RES output data. Compared with the PSO algorithm based on the precise predicted data of the load and the RES, the results show that the proposed method can achieve better load smoothing and maximum self-consumption of the RES without the requirement of precise load and RES forecasting.

Active islanding detection methods are generally employed for grid-connected inverter-based Distributed Generation (DG). However, there might be mutual influences and power quality issues caused by the disturbance signal when multiple inverters are involved. To address those problems, this paper analyzes the potential failure mechanism of the f-Q (frequency-reactive power) drifting active method in multiple-DG situations. Then, a novel high frequency transient injection based islanding detection method that is suitable for both single and multiple-DGs is proposed. Compared with the conventional injection methods, a high frequency impedance model for DG is provided for better theoretical analysis. By means of the intermittent Time Domain Low Voltage Condition (TDLVC) injection control, this method can achieve good accuracy and reduce disturbances to power system. 

Distributed generations (DGs) in the distribution systems are connected into the buses using power electronic converters. During fault, it is challenging to provide a constant impedance model for DGs in the system frequency due to the variable converter control strategies. System frequency impedance measurement based fault locations can be influenced by the converters’ fault behaviour. This study addresses this problem by proposing a wide-area high-frequency impedance comparison based fault location technique. The high-frequency impedance model of DG is provided. Based on the constant DG impedance model in high-frequency range, the faulted line sections can be distinguished by comparing the measured impedance differences without requiring the exact distribution system parameters. Simulation results show that the proposed wide-area transient measurements based fault location method can provide accurate faulted sections in the distribution systems with DGs regardless of the load and DG output variations, measurement noise, unbalanced loads and islanding operations.

A new Active Impedance Estimation (AIE) based protection strategy which is suitable for utilization in a DC zonal marine power distribution system is presented. This method uses two triangular current "spikes" injections for system impedance estimation and protection when faults are detected. By comparing the estimated impedance with the pre-calibrated value, the fault location can be predicted and fault can be isolated without requiring communication between two injection units. Using co¬operated double injections and line current measurement (directional fault detection), faults in the system with same impedance and different fault positions can be distinguished, located and isolated. The proposed method is validated using experimental test results derived from a 30kW, 400V, twin bus DC marine power system demonstrator. The experimental tests were applied to both faults during normal operation and faults that occur during system restoration.

Distributed Generations (DGs) with power electronic devices and their control loops will cause distortion to the fault currents and result in errors for power frequency measurement based fault locations. This might jeopardize the distribution system fault restoration and reduce the grid resilience. The proposed method uses high frequency (up to 3kHz) fault information and short window measurement to avoid the influence of DG control loops. Applying the DG high frequency impedance model, faults can be accurately located by measuring the system high frequency line reactance. Assisted with the DG side recorded unsynchronized data, this method can be employed to distribution systems with multiple branches and laterals. 

In a micro-grid, due to potential reverse output profiles of the Renewable Energy Source (RES) and the load, energy storage devices are employed to achieve high self-consumption of RES and to minimize power surplus flowing back into the main grid. This paper proposes a variable charging/discharging threshold method to manage energy storage system. And an Adaptive Intelligence Technique (AIT) is put forward to raise the power management efficiency. A battery-ultra-capacitor hybrid energy storage system (HESS) with merits of high energy and power density is used to evaluate the proposed method with onsite measured RES output data. Compared with the PSO algorithm based on the precise predicted data of the load and the RES, the results show that the proposed method can achieve better load smoothing and maximum self-consumption of the RES without the requirement of precise load and RES forecasting.

Active islanding detection methods are generally employed for grid-connected inverter-based Distributed Generation (DG). However, there might be mutual influences and power quality issues caused by the disturbance signal when multiple inverters are involved. To address those problems, this paper analyzes the potential failure mechanism of the f-Q (frequency-reactive power) drifting active method in multiple-DG situations. Then, a novel high frequency transient injection based islanding detection method that is suitable for both single and multiple-DGs is proposed. Compared with the conventional injection methods, a high frequency impedance model for DG is provided for better theoretical analysis. By means of the intermittent Time Domain Low Voltage Condition (TDLVC) injection control, this method can achieve good accuracy and reduce disturbances to power system. 

A portable injection unit for Active Impedance Estimation (AIE) is built and tested in a DC zonal marine power distribution system to provide useful information for system protection and restoration. The portable unit generates current “spikes” and injects them into the system once short circuit faults are detected (by measuring the system voltage drop). The faulted system impedance can be estimated by AIE and comparing the estimated impedance with the pre-calibrated value, the fault location can be determined. The proposed method does not rely on system fault transient information or communication from the remote-end measurement and offers fast and accurate fault location in DC marine distribution systems. The proposed method has been tested and validated on a 750V, 2 MW twin bus DC Commercial Test Facility with the system both de-energised and energised.

Distributed generations (DGs) in the distribution systems are connected into the buses using power electronic converters. During fault, it is challenging to provide a constant impedance model for DGs in the system frequency due to the variable converter control strategies. System frequency impedance measurement based fault locations can be influenced by the converters’ fault behaviour. This study addresses this problem by proposing a wide-area high-frequency impedance comparison based fault location technique. The high-frequency impedance model of DG is provided. Based on the constant DG impedance model in high-frequency range, the faulted line sections can be distinguished by comparing the measured impedance differences without requiring the exact distribution system parameters. Simulation results show that the proposed wide-area transient measurements based fault location method can provide accurate faulted sections in the distribution systems with DGs regardless of the load and DG output variations, measurement noise, unbalanced loads and islanding operations.

A new Active Impedance Estimation (AIE) based protection strategy which is suitable for utilization in a DC zonal marine power distribution system is presented. This method uses two triangular current "spikes" injections for system impedance estimation and protection when faults are detected. By comparing the estimated impedance with the pre-calibrated value, the fault location can be predicted and fault can be isolated without requiring communication between two injection units. Using co¬operated double injections and line current measurement (directional fault detection), faults in the system with same impedance and different fault positions can be distinguished, located and isolated. The proposed method is validated using experimental test results derived from a 30kW, 400V, twin bus DC marine power system demonstrator. The experimental tests were applied to both faults during normal operation and faults that occur during system restoration.

A portable injection unit for Active Impedance Estimation (AIE) is built and tested in a DC zonal marine power distribution system to provide useful information for system protection and restoration. The portable unit generates current “spikes” and injects them into the system once short circuit faults are detected (by measuring the system voltage drop). The faulted system impedance can be estimated by AIE and comparing the estimated impedance with the pre-calibrated value, the fault location can be determined. The proposed method does not rely on system fault transient information or communication from the remote-end measurement and offers fast and accurate fault location in DC marine distribution systems. The proposed method has been tested and validated on a 750V, 2 MW twin bus DC Commercial Test Facility with the system both de-energised and energised.