High-dimensional categorical data contains rich user-sensitive information, which poses huge privacy threats to users once leaked during data clustering and analysis. The existing K -mode method under local differenti...
High-dimensional categorical data contains rich user-sensitive information, which poses huge privacy threats to users once leaked during data clustering and analysis. The existing K -mode method under local differential privacy (LDP) always requires multiple user-server interactions, which not only has high communication overhead and computational cost but also makes user privacy vulnerable to malicious attacks during interactions. In this paper, we propose a non-interactive LDP K -mode clustering estimation method for high-dimensional categorical data. We first perform dimensionality reduction on each user data locally through the Fsketch algorithm. Then, we perturb the sketch data, ensuring the perturbation satisfies LDP. The perturbed data is then submitted to the server for K -mode clustering. Finally, on the server, we directly estimate the Hamming distance on the perturbed data to achieve K -mode clustering analysis. It is theoretically proven that our perturbation method satisfies LDP and is unbiased. Compared with state-of-the-art methods, our scheme more accurately estimates the Hamming distance between high-dimensional categorical data, reducing communication overhead due to only one interaction. Extensive experiments demonstrate the effectiveness of our method on four real high-dimensional category data sets, in which our scheme has a smaller normalized intra-cluster variance and larger purity index under the same privacy budget.
Fault characteristics in offshore wind power low-frequency transmission lines are significantly affected by the control strategies of power converters on both ends, making fault behavior and its impact on traditional ...
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Tampering,forgery and theft of the measurement and control messages in a smart grid could cause one breakdown in the power ***,no security measures are employed for communications in intelligent *** services in an int...
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Tampering,forgery and theft of the measurement and control messages in a smart grid could cause one breakdown in the power ***,no security measures are employed for communications in intelligent *** services in an intelligent substation have high demands for real-time performance,which must be considered when deploying security *** paper studies the security requirements of communication services in intelligent substations,analyzes the security capabilities and shortages of IEC 62351,and proposes a novel security scheme for intelligent substation *** security scheme covers internal and telecontrol communications,in which the real-time performance of each security measure is *** this scheme,certificateless public key cryptography(CLPKC)is used to avoid the latency of certificate exchange in certificate-based cryptosystem and the problem of key escrow in identity-based cryptosystem;the security measures of generic object-oriented substation event,sampled measure value and manufacturing message specification in IEC 62351 are improved to meet the real-time requirements of the messages as well as to provide new security features to resist repudiation and replay attacks;and the security at transport layer is modified to fit CLPKC,which implements mutual authentication by exchanging ***,a deployment of CLPKC in an intelligent substation is *** also evaluate the security properties of the scheme and analyze the end-to-end delays of secured services by combining theoretical calculation and simulation in this *** results indicate that the proposed scheme meets the requirements of security and real-time performance of communications in intelligent substations.
Low-frequency AC cable feeder is an important part of low-frequency transmission systems. Due to the influence of the double-side converter control strategy, its fault characteristics are obviously different from thos...
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Low-frequency AC cable feeder is an important part of low-frequency transmission systems. Due to the influence of the double-side converter control strategy, its fault characteristics are obviously different from those of the conventional powergrid, which makes it difficult for differential protection to meet the reliability requirements. To solve the above problems, according to the fault current difference between the two sides of the low-frequency transmission line, a low-frequency cable outgoing line protection method based on Kullback-Leibler divergence is proposed in this paper. Firstly, the fault currents at both ends of the cable line are extracted. Then the probability distribution of the extracted current on both sides are calculated. Thirdly the K-L divergence value is calculated and the protection criteria are given. According to the difference of K-L divergence value between internal and external fault occurrence, internal and external fault can be identified. Finally, the offshore wind power low-frequency transmission system model is built in PSCAD/EMTDC to output fault data, which is processed by Matlab to verify the protection method. The simulation results show that the method has good sensitivity and reliability in offshore wind power low-frequency cable feeder transmission lines, which is less affected by the transition resistance. It can not only withstand up to 300 Ω transition resistance, but also has strong resistance to noise interference and data anomalies and is capable of identifying all kinds of faults quickly and reliably.
Distributed generation (DG) injects new vigor into the power system, but it sometimes brings unfavorable factors influencing the power quality of distribution network. In this paper, the Dynamic Voltage Restorer (DVR)...
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Distributed generation (DG) injects new vigor into the power system, but it sometimes brings unfavorable factors influencing the power quality of distribution network. In this paper, the Dynamic Voltage Restorer (DVR) is introduced to the distribution network to improve the power quality. In view of that the detection of voltage compensation is the key factor that influences the effect of voltage compensation, a voltage direct detection method based on mathematical morphology is proposed. Firstly, the positive-sequence voltage with harmonics can be extracted by the instantaneous sequence-component decomposer. And then the harmonics is filtered by mathematical morphology filter. Lastly, the control variable of voltage compensation needed by DVR can be calculated from the voltage direct-detecting algorithm. The simulation results show that this method has the characteristics of favorable accuracy, real-time performance and simplicity, and assures the voltage quality of load side after compensation by DVR.
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