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state Key Laboratory of power grid Safety and Energy Conservation,China electric power research institute,Beijing,China

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CSEE Journal of power and Energy Systems 2022年第3期8卷 710-720页

作者： Lin Yu Huadong Sun Shiyun Xu Bing Zhao Jian Zhang state Key Laboratory of power grid Safety and Energy Conservation China Electric Power Research InstituteBeijing100192China

The power system is experiencing a higher penetration of renewable energy generations(REGs).The short circuit ratio(SCR)and the grid impedance ratio(GIR)are two indices to quantify the system strength of the power system with REGs.In this paper,the critical short circuit ratio(CSCR)is defined as the corresponding SCR when the system voltage is in the critical stable state.Through static voltage stability analysis,the mathematical expression of the CSCR considering the impact of GIR is derived.The maximum value of CSCR is adopted as the critical value to distinguish the weak power system.Based on the static equivalent circuit analysis,it is proved that the CSCR is still effective to evaluate critical system strength considering the interactive impact among REGs.Finally,we find that the GIR can be neglected and the SCR can be used individually to evaluate the system strength when SCR>2 or GIR>5.The correctness and rationality of the CSCR and its critical value are validated on ADPSS.

关键词： Critical short circuit ratio critical value grid impedance ratio maximum power transfer theorem static equivalent circuit analysis

Decomposition analysis of CO_(2) emissions of electricity and carbon-reduction policy implication: a study of a province in China based on the logarithmic mean Divisia index method

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Clean Energy 2023年第2期7卷 340-349页

作者： Fuyuan Yang Xiaobin Yang Xueqin Tian Xinlei Wang Tong Xu state grid Economic and Technological research institute Co. LtdBeijing102209China state grid Jiangxi electric power research institute State Grid Jiangxi Electric Power Co.LtdNanchangChina

As the proportion of electricity in final energy consumption gradually increases,CO_(2) emissions reduction actions in the power system will become the key to achieving China’s carbon-peak and carbon-neutrality goals.It is essential to analyse and quantify the driving forces of CO_(2) emissions from electricity generation in the fossil-rich area in China.This paper aims to identify the characteristics of CO_(2) emissions generated by electricity and provide a basis for formulating CO_(2)-reduction policies in power systems.First,we analyse the current state of CO_(2) emissions from electricity generation in Anhui Province that was dominated by fossil energy during the period 2010-19.Then,we apply the logarithmic mean Divisia index method to find the nature of the factors influencing the changes in CO_(2) emissions.Finally,we analyse the CO_(2)-reduction measures of each side of the source-network-load-storage of the power system in Anhui through a power-system carbon-reduction path analysis model proposed in this study and provide policy suggestions.The results showed the following.(i)CO_(2) emissions in Anhui Province continued to increase from 2010 to 2019 and the trend in the growth rate of CO_(2) emissions presented approximately a u-shaped curve.(ii)Economic activity has always been the dominant factor driving the growth of electricity CO_(2) emis-sions.The increase in the proportion of renewable energy in power generation,the improvement in thermal power-conversion efficiency and the decrease in the intensity of power consumption are the three major driving factors for the reduction in CO_(2) emissions from power generation in Anhui.(iii)The CO_(2)-reduction measures of the power system are provided in each link of the source-network-load-storage,such as developing the photovoltaic industry and building energy storage,upgrading and transforming coal-fired power stations,redu-cing the loss rate of transmission lines on the grid side and improving the efficiency of the utilization of electricity on the user s

关键词： CO_(2)emissions LMDI electricity generation carbon-reduction measures

Impedance Analysis of grid Forming Control Based Modular Multilevel Converters

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Journal of Modern power Systems and Clean Energy 2023年第3期11卷 967-979页

作者： Rongcai Pan Guangfu Tang Shan Liu Zhiyuan He China electric power research institute Beijing 100192China state grid Smart grid research institute Beijing 102209China

grid-forming control(GFC)is promising for power electronics based power systems with high renewable energy penetration.Naturally,the impedance modeling for GFC is necessary and has gained significant attention recently.However,most of the impedance analyses for GFC are based on a twolevel converter(TLC)rather than a modular multilevel converter(MMC).MMC differs from TLC with respect to its dominant multi-frequency response.It is necessary to analyze the impedance of GFC-based MMC owing to its superiority in highvoltage direct current(HVDC)transmission to interlink two weak AC systems with high renewable energy penetration.As the main contribution,this paper presents the AC-and DC-side impedance analyses for the GFC-based MMC with both power and DC voltage control using the harmonic transfer function(HTF),and compares the impedances of GFC-based MMC and TLC.It is inferred that although the impedance is mainly influenced within 200 Hz,the instability still could occur owing to negative resistance triggered by relatively larger parameters.The difference in AC-side impedance with power and DC voltage control is not apparent with proper parameters,while the DC-side impedance differs significantly.The generalized Nyquist criterion is necessary for AC-side stability owing to the relatively large coupling terms under GFC.Moreover,the coupling between AC-and DC-side impedances is noneligible,especially considering the DC-side resonance around the system resonant peak.The effects of parameters,system strength,and virtual impedance on the impedance shaping are analyzed and verified through simulations.

关键词： Sequence impedance modular multilevel converter(MMC) grid-forming control(GFC) harmonic transfer function generalized Nyquist criterion

An improved strategy for out-of-step oscillation separation devices based on apparent impedance angle applied to a series compensated line

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Protection and Control of Modern power Systems 2022年第1期7卷 316-323页

作者： Haibo Xu Yupeng Cai Xiaolei Qu Zhiwei Dong NARI Group Corporation/State Grid Electric Power Research Institute Nanjing 210003China electric power research institute of state grid Liaoning electric power Co. LtdShenyang 110006China

Out-of-step oscillation separation devices based on apparent impedance angle trajectory are widely used in the power grid in China,and their reliability is of great importance.In this paper,the influence mechanism of series compensation on apparent impedance angle trajectory is analyzed.It reveals that series compensation capacitors reduce the equivalent impedance angle and consequently the apparent impedance angle cannot pass through all four zones,resulting in the risk of failure for the separation devices.A revised method of apparent impedance angle based on compensation principle is discussed,and then an improved out-of-step oscillation detection criterion is proposed.In view of the fact that the apparent impedance angle at the moment of maximum current is equal to the equivalent impedance angle during an oscillation process,a practical algorithm based on the compensated apparent impedance angle is proposed.RTDS tests are conducted to verify the effectiveness of the new criterion,considering transmission lines with a high series compensation level.

关键词： Out-of-step oscillation separation Series compensated line Apparent impedance angle Compensated impedance angle

Operating system network security enhancement scheme based on trusted storage

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Intelligent and Converged Networks 2023年第2期4卷 127-141页

作者： Longyun Qi Xiaoliang Lv Lianwen Sun Tianle Yao Jianye Yu Lei Wang State Grid Electric Power Research Institute Nanjing 210003China state grid Beijing electric power Company Beijing 100031China

Data storage security has become the core of many network security issues.In order to achieve trusted storage and trusted measurement of network community data,this paper proposes a secure storage model based on trust extension for existing trusted storage technologies.In the process of document encryption,the key information is encrypted as well as decentralized stored by optimizing the ciphertext inverted index structure and update policy to ensure the security of index information.In the process of user access control mechanism,SAML and XACML are used in combination with role-based access control in order to achieve flexible and efficient authorization and access control.In the process of result query,ontology technology is introduced to better express the user’s query intention and improve the query accuracy.A large number of experiments demonstrate the effectiveness and feasibility of the scheme.

关键词： trusted storage trust extension trusted platform model(TPM) access control

Hygrothermal ageing performance of high temperature vulcanised silicone rubber and its degradation mechanism

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High Voltage 2023年第6期8卷 1196-1205页

作者： Yu Deng Bo Peng Zheyuan Liu Yujun Du Songsong Zhou Jinghua Liu Xinzhe Yu Jun Zhou state Key Laboratory of power grid Environmental Protection(China electric power research institute) BeijingChina state grid Corporation of China BeijingChina

High temperature vulcanised silicone rubber(SR)has excellent hydrophobicity and thus is widely applied both in indoor and outdoor insulation.According to the analysis of different experimental ageing tests and field investigation of SR,temperature and humidity are considered to be the fundamental factors during degradation.Hygrothermal ageing was proposed in this study to simulate the chalking state of the SR,finally leading to the irreversible degradation far below the thermal decomposition temperature.The variation of morphology,hardness and polydimethylsiloxane(PDMS)content was quantified during the yearlong hygrothermal ageing test.It is implied that the gradual process of whitening and hardening are accompanied by the decline of the PDMS content.Finally,ageing delamination in SR and its degradation mechanism were proposed.

关键词： thermal mechanism rubber

Control Method for Additional Damper in Hydro-turbine Speed Governor of Hydro-dominant power Systems

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CSEE Journal of power and Energy Systems 2023年第2期9卷 589-598页

作者： Guanhong Wang Yong Tang Ying Li Dongping Ai Gang Chen Wei Wei Department of power System China Electric Power Research InstituteBeijing 100192China Department of power System Technology State Grid Sichuan Electric Power Research InstituteChengdu 610072China

With the rapid development of the national interconnected power grid,fast automatic excitation regulators and fast turbine governors are being widely used.In the current systems,some power plants adjust their responses for turbine governor systems to a very sensitive level to meet the primary frequency regulation assessment index,which actively brings about negative damping.Under these circumstances,the ultralow frequency oscillation(ULFO)phenomenon emerged in hydrodominant power systems.In order to solve the problem of ULFO,the hydro-turbine governor additional damper(GAD)based on phase compensation,which adapts to ULFO,is developed.The design of the control system is relatively simple.As a phase compensation based on the field testing and modeling of the turbine governor,GAD can provide the power system with positive damping,which contributes to the stability and security of the system.According to the impact of the mechanism of the turbine governor on the dynamic stability of the power system and the research of modeling and parametric testing,the proposed method not only supports positive damping,but also eliminates the negative damping of the speed governing system,which can significantly suppress the ultralow frequency oscillation and make it feasible to configure the GAD parameters according to field testing.

关键词： Governor additional damper phase compensation power system ULFO

Parameter optimization of complex network based on the change-point identification

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The Journal of China Universities of Posts and Telecommunications 2023年第6期30卷 22-29页

作者： Xu Xingtao Tao Jiagui electric power research institute State Grid Jiangsu Electric Power Co.Ltd.Nanjing 210013China

This paper proposes a novel method for the parameter optimization of complex networks established through coarsening and phase space reconstruction.Firstly,we identify the change-points of the time series based on the cumulative sum(CUSUM)control chart method.Then,we optimize the coarse-graining parameters and phase space embedding dimension based on the evolution analysis of the global topology index(betweenness)at the mutation point.Finally,we conduct a simulation analysis based on real-time data of Chinese copper spot prices.The results show that the delay of the copper spot prices in Chinese spot market is 1 day,and the optimal embedding dimension of the phase space reconstruction is 3.The acceptance level of the investors towards the small fluctuations in copper spot prices is 0.2 times than the average level of price fluctuations,which means that an average price fluctuation of 0.2 times is the optimal coarse-graining parameter.

关键词： complex network change-point coarse-graining embedding dimension

Stabilizing and boosting I/O performance for file systems with journaling on NVMe SSD

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Science China(Information Sciences) 2022年第3期65卷 95-109页

作者： Lin QIAN Bin TANG Baoliu YE Jianyu WU Xiaoliang WANG Sanglu LU National Key Laboratory for Novel Software Technology State Grid Electric Power Research Institute

Many journaling file systems currently use non-volatile memory-express(NVMe) solid-state drives(SSDs) as external journal devices to improve the input and output(I/O) performance. However,when facing microwrite workloads, which are typical of many applications, they suffer from severe I/O fluctuations and the NVMe SSD utilization is extremely low. The experimental results indicate that this phenomenon arises mainly because writing back data to backend file systems on hard disk drives is much slower than journal writing, causing journal writing to frequently freeze because of the two-phase mechanism.We, therefore, propose a merging-in-memory(MIM) acceleration architecture to stabilize and boost the I/O performance for such journaling file systems. MIM employs an efficient data structure of hash-table-based multiple linked lists in memory, which not only merges random microwrites into sequential large blocks to speed up writebacks but also provides additional gains in terms of reducing the frequency of write addressing and object opening and closing. Using a prototype implementation in Ceph File Store, we experimentally show that MIM not only eliminates severe fluctuations but also improves the I/O operations per second by roughly 1×–12× and reduces the write latency by 75%–98%.

关键词： journaling file systems NVMe SSD microwrite merging hash table Ceph