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Dynamic VAR planning methodology to enhance transient voltage stability for failure recovery

Journal of Modern Power Systems and Clean Energy 2018年第4期6卷 712-721页

作者： Di YANG Haozhong CHENG Zeliang MA Liangzhong YAO Zhonglie ZHU State grid Pudong Power Supply company SMEPC Department of Electronic Information and Electrical Engineering Shanghai Jiao Tong University east china grid company limited china Electric Power Research Institute

In recent years, failure recovery after faults is concerned and discussed worldwide as an important and hot topic. Facing the challenge of heavy loads and ultrahigh voltage transmission, it's urgent to propose some solutions to enhance transient voltage stability for failure recovery. Therefore, a novel dynamic volt ampere reactive(VAR) planning methodology is proposed in this paper to help failure recovery and improve transient voltage stability after contingencies. First, a transient voltage fluctuation(TVF) index is proposed to evaluate transient voltage condition after faults. Then dynamic compensationsensitivity is presented for searching the best candidate locations. Following that, the dynamic VAR planning methodology based on an improved Tent chaos multi-objective algorithm is discussed in detail. There are two optimization objects in the optimization. One is to minimize TVF to enhance transient voltage stability for failure recovery. And the other optimization is to minimize dynamic VAR investment cost and operation cost. Finally,IEEE 39 power system and a practical power system are analyzed and discussed. The proposed dynamic VAR planning methodology can support enough reactive power for failure recovery. With the least SVC planning amount and the power loss cost, it can greatly decrease the system TVF index and enhance the transient voltage stability. It's proved that the proposed dynamic VAR planning optimization is effective and helpful for safety operation of power system.

关键词： Dynamic VAR planning Failure recovery Improved Tent mapping chaos optimization Transient stability

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Non-intrusive Load Monitoring Based on Graph Total Variation for Residential Appliances

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Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 947-957页

作者： Xiaoyang Ma Diwen Zheng Xiaoyong Deng Ying Wang Dawei Deng Wei Li the College of Electrical Engineering Sichuan UniversityChengdu 610065China State grid Chongqing Electric Power company Chongqing 400014China State grid Sichuan Electric Power company Chengdu 610095China State grid Hubei Electric Power company limited Research Institute Wuhan 430077China

Non-intrusive load monitoring is a technique for monitoring the operating conditions of electrical appliances by collecting the aggregated electrical information at the household power *** several studies on the mining of unique load characteristics,few studies have extensively considered the high computational burden and sample *** on lowfrequency sampling data,a non-intrusive load monitoring algorithm utilizing the graph total variation(GTV)is proposed in this *** algorithm can effectively depict the load state without the need for prior ***,the combined Kmeans clustering algorithm and graph signals are used to build concise and accurate graph structures as load *** GTV representing the internal structure of the graph signal is introduced as the optimization model and solved using the augmented Lagrangian iterative *** introduction of the difference operator reduces the computing cost and addresses the inaccurate reconstruction of the graph *** low-frequency sampling data,the algorithm only requires a little prior data and no training,thereby reducing the computing *** conducted using the reference energy disaggregation dataset and almanac of minutely power dataset demonstrated the stable superiority of the algorithm and its low computational burden.

关键词： Non-intrusive load monitoring graph total variation augmented Lagrangian function smart grid

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A Missing Power Data Filling Method Based on Improved Random Forest Algorithm

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Chinese Journal of Electrical Engineering 2019年第4期5卷 33-39页

作者： Wei Deng Yixiu Guo Jie Liu Yong Li Dingguo Liu Liang Zhu State grid Hunan Power company limited Research Institute Changsha 410007China College of Electrical and Information Engineering Hunan UniversityChangsha 410082China State grid Hunan Electric Power company limited Changsha 410004China

Missing data filling is a key step in power big data preprocessing,which helps to improve the quality and the utilization of electric power *** to the limitations of the traditional methods of filling missing data,an improved random forest filling algorithm is *** a result of the horizontal and vertical directions of the electric power data are based on the characteristics of time ***,the method of improved random forest filling missing data combines the methods of linear interpolation,matrix combination and matrix transposition to solve the problem of filling large amount of electric power missing *** filling results show that the improved random forest filling algorithm is applicable to filling electric power data in various missing ***’s more,the accuracy of the filling results is high and the stability of the model is strong,which is beneficial in improving the quality of electric power data.

关键词： Big data cleaning missing data filling data preprocessing random forest data quality

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Inhibition roles of molybdate and borate on Q235 steel corrosion in resistance reducing agent

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Journal of Iron and Steel Research International 2023年第8期30卷 1477-1489页

作者： Yang Yang Hui Su Lan-lan Liu Song Xu Zhen Zhong Xiao-bao Zhou Tang-qing Wu School of Materials Science and Engineering Xiangtan UniversityXiangtan 411105HunanChina State grid Hunan Electric Power company limited Transmission Maintenance Changsha 410100HunanChina State grid Hunan Electric Power company limited Research Institute Changsha 410007HunanChina

The effects of Na_(2)MoO_(4) and Na_(2)B_(4)O_(7) on corrosion behavior of Q235 steel in resistance reducing agent(RRA)containing sodium bentonite were studied by mass loss,scanning electron microscopy and electrochemical *** results showed that both the independent and mixed additions of Na_(2)MoO_(4) and/or Na_(2)B_(4)O_(7),can reduce the corrosion rate of Q235 steel in RRA containing sodium *** the inhibition effect of Na_(2)MoO_(4) and/or Na_(2)B_(4)O_(7)increased with their dosage *** the same dosage,the inhibition efficiency of the mixed addition of Na_(2)MoO_(4) and Na_(2)B_(4)O_(7),was higher than that of their independent *** passivation effect of Q235 steel was easy to obtain in the RRA with the mixed addition of Na_(2)MoO_(4) and Na_(2)B_(4)O_(7).The optimized inhibitor for the RRA containing sodium bentonite was the mixture of Na_(2)B_(4)O_(7) and Na_(2)MoO_(4) with a total concentration of 1.5 wt.%.Furthermore,the increase in corrosion potential E_(corr) and the decrease in corrosion current density i_(cor) in carbon steel were one of the important criteria for the formation of passivation film.

关键词： Q235 steel Resistance reducing agent Corrosion inhibitor Sodium bentonite Electrochemical impedance spectrum

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Analysis and suppression of operational overvoltage and inrush current for high-speed trains by automatic phase-switching technique

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High Voltage 2024年第3期9卷 733-748页

作者： Ye Cao Song Xiao Zhizong Ye Guangning Wu Yujun Guo Guoqiang Gao Chuanming Sun Jiancheng Liu Zheng Chen Hao Hou Zijing Wang Puyang Liu Yuhui Zhang Jie Yu School of Electrical Engineering Southwest Jiaotong UniversityChengduChina Guangdong Power grid limited Liability company China Southern Power GridGuangzhouChina CRRC Qingdao Sifang Co. Ltd.QingdaoChina State grid Chongqing Electric Power company ChongqingChina

When a high-speed train approaches the insulated phase-splitting section embedded between neighbouring power supply arms,the vacuum circuit breaker(VCB)installed on trains must be disconnected to maintain the traction power supply system as a no-load condition for completing phase-switching action,as the train passes through the phase-splitting section depending on its ***,when operating VCBs,the arc is easily triggered between the mobile contacts inside,accompanied by an overvoltage ***,to explore the generating mechanism of inrush current and operational overvoltage,a model describing the‘substation-catenary-train’traction power supply system is launched based on an equivalent circuit modelling *** the analysis of the transient VCB operational process,the phase of catenary voltage is directly related to the characteristics of the VCB switching-on overvoltage,as the traction cur-rent's phase angle is relevant to the amplitude-frequency characteristics of the VCB switching-off *** current as a noteworthy element is related to the traction transformer's *** automatic phase-switching technique is utilised to suppress both operational overvoltage and inrush current,as the optimal combination of VCB switching-on and switching-off phases considering the balance between overvoltage and inrush current is achieved based on the particle swarm algorithm.

关键词： traction phase inrush

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Winding Capacitance Dividing Method for Powerformer

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高电压技术 2008年第5期34卷 966-972页

作者： TIAN Qing LIN Xiang-ning LI Jian-jian TAO Yong-hong Southeast Shanxi Ultra High Voltage Administrative Bureau State Grid Operation Company Limited Changzhi 047100 China Department of Electrical Engineering China Three Gorges University Yichang 443002 China State grid Operation of company limited Beijing 100005 China Department of Electrical Information Xihua University Chengdu 610039 China

It presents a method which can equivalently arrange the capacitance distribution along with the winding of the generator on the terminal and neutral respectively in a reasonable partition,particularly for a type of high-voltage graded insulated cable wound generator,*** winding of the Powerformer adopts graded insulation,which leads to the various cable thicknesses in different portion of the winding,and thus,the uneven capacitance *** large capacitive currents and large transient outrush currents resulting from the cable consisting of the stator winding of Powerformer may cause problems to the generator differential *** of literatures available in the field of compensated differential protection focus on the charging current compensation for long transmission line,instead of for *** authors give a method which can be used to compensate the capacitive current wholly to improve the reliability of the differential protection of *** is proved that the distributed capacitance can be equivalent as the lump circuit with a capacitance partition coefficient ρ,and ρ is proved as a constant no matter whether the generator experiences the normal operation,external phase(s) fault or internal phase(s) *** formula of the partition coefficient is provided and the corresponding equivalent circuit of the Powerformer cable to calculate capacitance currents is *** analysis programming resolving the minimum value of the coefficient ρ is written in MATLAB 7.0/m according to this formula,using the function fmincon() which can work in any type of constraint *** program always gets the same global minimum points under the different initial values condition which proves our point by mathematical *** this new approach to winding capacitance dividing method,the protection scheme used for Powerformer can be validated and improved accordingly.

关键词：电力系统电容分配模式动力设备

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Parameter Estimation of Sub-/Super-synchronous Oscillation Based on Interpolated All-phase Fast Fourier Transform with Optimized Window Function

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Journal of Modern Power Systems and Clean Energy 2024年第4期12卷 1031-1041页

作者： Bo Sun Xi Wu Xi Chen Zixiao Zou Qiang Li Bixing Ren School of Electrical Engineering Southeast UniversityNanjingChina State grid Jiangsu Electric Power company limited Research Institute NanjingChina

In recent years,with increasing amounts of renewable energy sources connecting to power grids,sub-/super-synchronous oscillations(SSOs)occurred more *** to the time-variant nature of SsO magnitudes and frequencies,as well as the mutual interferences among SsO modes with close frequencies,the accurate parameter estimation of SsO has become a particularly challenging *** solve this issue,this paper proposes an improved spectrum analysis method by improving the window function and a spectrum correction method to achieve higher ***,by aiming at the sidelobe characteristics of the window function as evaluation criteria,a combined cosine function is optimized using a genetic algorithm(GA).Furthermore,the obtained window function is self-convolved to extend its excellent characteristics,which have better performance in reducing mutual interference from other SSO ***,a new form of interpolated all-phase fast Fourier transform(IpApFFT)using the optimized window function is proposed to estimate the parameters of *** method allows for phase-unbiased estimation while maintaining algorithmic simplicity and *** performance of the pro-posed method is demonstrated under various conditions,com-pared with other estimation *** results validate the effectiveness and superiority of the proposed method.

关键词： Sub-/Super-synchronous oscillation(SSO) window function parameter estimation interpolated all-phase fast Fourier transform(ApFFT)

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Curing kinetics and plugging mechanism of high strength curable resin plugging material

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Petroleum Science 2024年第5期21卷 3446-3463页

作者： Jing-Bin Yang Ying-Rui Bai Jin-Sheng Sun Kai-He Lv School of Petroleum Engineering China University of Petroleum(East China) CNPC Engineering Technology R&D company limited

Lost circulation, a recurring peril during drilling operations, entails substantial loss of drilling fluid and dire consequences upon its infiltration into the formation. As drilling depth escalates, the formation temperature and pressure intensify, imposing exacting demands on plug materials. In this study, a kind of controllable curing resin with dense cross-network structure was prepared by the method of solution stepwise ring-opening polymerization. The resin plugging material investigated in this study is a continuous phase material that offers effortless injection, robust filling capabilities, exceptional retention, and underground curing or crosslinking with high strength. Its versatility is not constrained by fracture-cavity lose channels, making it suitable for fulfilling the essential needs of various fracture-cavity combinations when plugging fracture-cavity carbonate rocks. Notably, the curing duration can be fine-tuned within the span of 3-7 h, catering to the plugging of drilling fluid losing of diverse fracture dimensions. Experimental scrutiny encompassed the rheological properties and curing behavior of the resin plugging system, unraveling the intricacies of the curing process and establishing a cogent kinetic model. The experimental results show that the urea-formaldehyde resin plugging material has a tight chain or network structure. When the concentration of the urea-formaldehyde resin plugging system solution remains below 30%, the viscosity clocks in at a meager 10 mPa·s. Optimum curing transpires at 60℃, showcasing impressive resilience to saline conditions. Remarkably, when immersed in a composite saltwater environment containing 50000 mg/L NaCl and 100000 mg/L CaCl2, the urea-formaldehyde resin consolidates into an even more compact network structure, culminating in an outstanding compressive strength of 41.5 MPa. Through resolving the correlation between conversion and the apparent activation energy of the non-isothermal DSC curing reactio

关键词： Urea-formaldehyde resin Rheological property Curing property Curing kinetics Plugging mechanism

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Integrated Frequency-constrained Scheduling Considering Coordination of Frequency Regulation Capabilities from Multi-source Converters

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 261-274页

作者： Jiaming Li Ying Qiao Zongxiang Lu Wei Ma Xin Cao Rongfu Sun the Department of Electrical Engineering Tsinghua UniversityBeijing 100084China the china Suntien Green Energy limited company Shijiazhuang 050011China the State grid Jibei Electric Power company Beijing 100054China

As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system ***,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of *** to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling ***,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing *** this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source *** FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is ***,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling *** nonlinear constraints for frequency security are precisely linearized through an improved iteration-based *** effectiveness of the proposed model is verified in a modified IEEE 24-bus standard *** results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.

关键词： Battery energy storage(BES) wind turbine generation(WTG) frequency regulation(FR) frequency security power system scheduling

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Stability Analysis and Control of DC Distribution System with Electric Vehicles

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Energy Engineering 2023年第3期120卷 633-647页

作者： Zhijie Zheng Song Zhang Xiaolei Zhang Bo Yang Fang Yan Xiaoning Ge State grid Shandong Electric Power company Economic and Technological Research Institute JinanChina State grid Shandong Electric Power company limited JinanChina State Nuclear Electric Power Planning Design&Research Institute company limited BeijingChina

The DC distribution network system equipped with a large number of power electronic equipment exhibits weak damping characteristics and is prone to low-frequency and high-frequency unstable *** current interpretation of the oscillation mechanism has not been ***,this paper established the complete statespace model of the distribution system consisting of a large number of electric vehicles,characteristic equation of the distribution network system is derived by establishing a state-space model,and simplified reduced-order equations describing the low-frequency oscillation and the high-frequency oscillation are ***,based on eigenvalue analysis,the oscillation modes and the influence of the key system parameters on the oscillation mode are ***,impacts of key factors,such as distribution network connection topology and number of dynamic loads,have been discussed to suppress oscillatory instability caused by inappropriate design or dynamic ***,using the DC distribution example system,through model calculation and time-domain simulation analysis,the correctness of the aforementioned analysis is verified.

关键词： DC distribution network system oscillation instability reduced-order equivalent model damping control sensitivity analysis

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