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您的检索式：作者名="Xiuhui CHAI"
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| 1 | Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm显示文摘In three-phase four-wire systems, unbalanced loads can cause grid currents to be unbalanced, and this may cause the neutral point potential on the grid side to shift. The neutral point potential shift will worsen the control precision as well as the performance of the threephase four-wire unified power quality conditioner(UPQC),and it also leads to unbalanced three-phase output voltage,even causing damage to electric equipment. To deal with unbalanced loads, this paper proposes a matching-ratio compensation algorithm(MCA) for the fundamental active component of load currents, and by employing this MCA,balanced three-phase grid currents can be realized under 100% unbalanced loads. The steady-state fluctuation and the transient drop of the DC bus voltage can also be restrained. This paper establishes the mathematical model of the UPQC, analyzes the mechanism of the DC bus voltage fluctuations, and elaborates the interaction between unbalanced grid currents and DC bus voltage fluctuations;two control strategies of UPQC under three-phase stationary coordinate based on the MCA are given, and finally, the feasibility and effectiveness of the proposed control strategy are verified by experiment results. | Xiaojun ZHAO Chunjiang ZHANG Xiuhui CHAI Jinlong ZHANG Fanqi LIU Zhe ZHANG | 2018 | Journal of Modern Power Systems and Clean Energy2018，6，6： | 2 |
| 2 | TPE-H2MWD:an exact thumbnail preserving encryption scheme with hidden Markov model and weighted diffusion显示文摘With the substantial increase in image transmission,the demand for image security is increasing.Noise-like images can be obtained by conventional encryption schemes,and although the security of the images can be guaranteed,the noise-like images cannot be directly previewed and retrieved.Based on the rank-then-encipher method,some researchers have designed a three-pixel exact thumbnail preserving encryption(TPE2)scheme,which can be applied to balance the security and availability of images,but this scheme has low encryption efficiency.In this paper,we introduce an efficient exact thumbnail preserving encryption scheme.First,blocking and bit-plane decomposition operations are performed on the plaintext image.The zigzag scrambling model is used to change the bit positions in the lower four bit planes.Subsequently,an operation is devised to permute the higher four bit planes,which is an extended application of the hidden Markov model.Finally,according to the difference in bit weights in each bit plane,a bit-level weighted diffusion rule is established to generate an encrypted image and still maintain the same sum of pixels within the block.Simulation results show that the proposed scheme improves the encryption efficiency and can guarantee the availability of images while protecting their privacy. | Xiuli CHAI Xiuhui CHEN Yakun MA Fang ZUO Zhihua GAN Yushu ZHANG | 2023 | Frontiers of Information Technology & Electronic Engineering2023，24，8： | 0 |
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