A Simple Capacitor Voltage Balancing Method with a Fundamental Sorting Frequency for Modular Multilevel Converters

Peng, Hao,Wang, Ying,Wang, Kun,Deng, Yan,He, Xiangning,Zhao, Rongxiang The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

A Fundamental Frequency Sorting Algorithm (FFSA) is proposed in this paper to balance the voltages of floating dc capacitors for Modular Multilevel Converters (MMCs). The main idea is to change the sequences of the CPS-PWM carriers according to the capacitor voltage increments during the previous fundamental period. Excessive frequent sorting is avoided and many calculating resources are saved for the controller. As a result, more sub-modules can be dealt with. Furthermore, it does not need to measure the arm currents. Therefore, the communication between the controllers can be simplified and the number of current sensors can be reduced. Moreover, the proposed balancing method guarantees that all of the switching frequencies of the sub-modules are equal to each other. This is quite beneficial for the thermal design of the sub-modules and the lifetime of the power switches. Simulation and experimental results acquired from a 9-level prototype verify the viability of the proposed balancing method.

Optimization of preventive maintenance of nuclear safety-class DCS based on reliability modeling

Peng Hao,Wang Yuanbing,Zhang Xu,Hu Qingren,Xu Biao 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10

Nuclear safety-class DCS is used for nuclear reactor protection function, which is one of the key facilities to ensure nuclear power plant safety, the maintenance for DCS to keep system in a high reliability is significant. In this paper, Nuclear safety-class DCS system developed by the Nuclear Power Institute of China is investigated, the model of reliability estimation considering nuclear power plant emergency trip control process is carried out using Markov transfer process. According to the System-Subgroup-Module hierarchical iteration calculation, the evolution curve of failure probability is established, and the preventive maintenance optimization strategy is constructed combining reliability numerical calculation and periodic overhaul interval of nuclear power plant, which could provide a quantitative basis for the maintenance decision of DCS system

RETCAM: An Efficient TCAM Compression Model for Flow Table of OpenFlow

Chaoqin Zhang,Penghao Sun,Guangwu Hu,Liang Zhu 한국통신학회 2020 Journal of communications and networks Vol.22 No.6

OpenFlow is a widely adopted dataplane protocol insoftware-defined networking (SDN). However, the expansion ofsupported match fields in OpenFlow brings additional pressure tothe storage space of ternary content addressable memory (TCAM)in physical device, since the arbitrary wildcard support in thematch field of OpenFlow relies heavily on TCAM for looking-upspeed. In this paper, a mathematical model aiming at the storagespace reduction of the flow table in TCAM is presented, which isnamed as RETCAM. RETCAM analyzes the relationships amongall the match fields and then categorize the redundancy amongdifferent fields into three types. Based on the three redundancytypes, three compression algorithms named as inter-field merge,field mapping and intra-field compression are presented. The outcomes of each compression algorithm are flow entries with smallerbit-width which is sent to TCAM for flow matching. In this way, theflexibility of OpenFlow is not harmed, thus maintaining the function integrity of the original flow table. Simulation at the end showsthat RETCAM saves almost about 60% of TCAM space for a givenflow table with no damage to the function integrity of OpenFlow,and the compression performance stands stable with the increaseof flow table size.

An Optimized Deployment Mechanism for Virtual Middleboxes in NFV- and SDN-Enabling Network

( Gang Xiong ),( Penghao Sun ),( Yuxiang Hu ),( Julong Lan ),( Kan Li ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.8

Network Function Virtualization (NFV) and Software Defined Networking (SDN) are recently considered as very promising drivers of the evolution of existing middlebox services, which play intrinsic and fundamental roles in today`s networks. To address the virtual service deployment issues that caused by introducing NFV or SDN to networks, this paper proposes an optimal solution by combining quantum genetic algorithm with cooperative game theory. Specifically, we first state the concrete content of the service deployment problem and describe the system framework based on the architecture of SDN. Second, for the service location placement sub-problem, an integer linear programming model is built, which aims at minimizing the network transport delay by selecting suitable service locations, and then a heuristic solution is designed based on the improved quantum genetic algorithm. Third, for the service amount placement sub-problem, we apply the rigorous cooperative game-theoretic approach to build the mathematical model, and implement a distributed algorithm corresponding to Nash bargaining solution. Finally, experimental results show that our proposed method can calculate automatically the optimized placement locations, which reduces 30% of the average traffic delay compared to that of the random placement scheme. Meanwhile, the service amount placement approach can achieve the performance that the average metric values of satisfaction degree and fairness index reach above 90%. And evaluation results demonstrate that our proposed mechanism has a comprehensive advantage for network application.

Shaking Table Test on Composite Isolation System of High-speed Railway Station with Integrated Station-Bridge Structure

Yingying Zhang,Penghao Yu,Baorui Sun,Yi Zhou,Peijian Chen,Junhao Xu,Yushuai Zhao 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2

This paper investigated the seismic performance of a typical “Integrated Station-Bridge high-speed railway station structure with a composite isolation system. The influential mechanism of the structure with isolation system was analyzed based on shaking table tests, mainly investigating on the failure mode, acceleration response and displacement response. Besides, a parameter optimization method of isolation layer for long-span structures was proposed based on genetic algorithm to better enhance the isolation performance of the large-span structure. The research revealed that there was no obvious damage to the composite isolation system under the PGA = 0.82 g. The nature frequency of the structure with isolation system is only 12.5% of that of non-isolation structure. The first three natural vibration frequency of the structure with isolation system only reduce 3.4%, 3.2%, 6.14% after the PGA = 1.27 g, that of the non-isolation structure reduce by more than 20%. The acceleration amplification factor of each layer of composite isolation system is less than 1, in particular, that of truss is about 0.3. The displacement response and acceleration response of the structure with isolation system have been reduced by about 90%. The proposed optimization method of isolation layer parameters provides an important reference for the isolation design for high-speed railway stations.

Further Electrochemical Degradation of Real Textile Effluent Using PbO₂ Electrode

Wang, Chao,Tian, Penghao The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.2

A commercial PbO₂ electrode was adopted as the anode for the electrochemical degradation of the real textile effluent with the initial COD of 56.0 mg L^-1 and the stainless steel plate as the cathode. The effect of the initial pH, the electrolyte flow rate and the cell voltage on the COD, the current efficiency and the energy consumption were investigated without the addition of NaCl or Na₂SO₄. The experimental results illustrated that the PbO₂ electrode can reduce the COD of the textile effluent from 56.0 mg L^-1 to 26.0 mg L^-1 with the current efficiency of 86.1% and the energy consumption of 17.5 kWh kg^-1 (per kilogram of degraded COD) under the optimal operating conditions. Therefore PbO₂ electrode as the anode was promising to further electrochemically degrade the real textile effluent.

Separating VNF and Network Control for Hardware-Acceleration of SDN/NFV Architecture

Tong Duan,Julong Lan,Yuxiang Hu,Penghao Sun 한국전자통신연구원 2017 ETRI Journal Vol.39 No.4

A hardware-acceleration architecture that separates virtual network functions (VNFs) and network control (called HSN) is proposed to solve the mismatch between the simple flow steering requirements and strong packet processing abilities of software-defined networking (SDN) forwarding elements (FEs) in SDN/network function virtualization (NFV) architecture, while improving the efficiency of NFV infrastructure and the performance of network-intensive functions. HSN makes full use of FEs and accelerates VNFs through two mechanisms: (1) separation of traffic steering and packet processing in the FEs; (2) separation of SDN and NFV control in the FEs. Our HSN prototype, built on NetFPGA-10G, demonstrates that the processing performance can be greatly improved with only a small modification of the traditional SDN/NFV architecture.

Superior Oxygen Electrocatalysis on RuSe<i>_x</i> Nanoparticles for Rechargeable Air Cathodes

Jang, Ji-Hoon,Lee, Eunjik,Xiao, Penghao,Park, Kyusung,Kim, In Young,Henkelman, Graeme,Hwang, Seong-Ju,Kwon, Young-Uk,Goodenough, John. B. Wiley (John WileySons) 2018 Advanced Energy Materials Vol.8 No.8