Line Load Research Articles

State and Parameter Estimation of Non-Uniform Transmission Line Using Kronecker Product Based Modeling

The distributed parameters of a non-uniform transmission line (NTL) are assumed to depend on a finite set of unknown parameters, for example, their spatial Fourier series coefficients. The line equations are set up taking random voltage and current line loading into account with the random loading being assumed to be white Gaussian noise in the time and spatial variables. Bypassing over to the spatial Fourier series domain, these line stochastic differential equations (SDEs) are expressed as a truncated sequence of coupled stochastic differential equations for the spatial Fourier series components of the line voltage and current. The coefficients that appear in these stochastic differential equations are the spatial Fourier series coefficients of the distributed line parameters and these coefficients in turn are linear functions of the unknown parameters. By separating these complex stochastic differential equations into their real and imaginary part, the line equations become a finite set of SDEs for the extended state defined to be the real and imaginary components of the line voltage and current as well as the parameters on which the distributed parameters depend. The measurement model is assumed to be white Gaussian noise corrupted versions of the line voltage and current sampled at a discrete set of spatial points on the line and this measurement model can be expressed as a linear transformation of the state variables, i.e, of the spatial Fourier series components of the line voltage and current plus a white measurement noise vector. This work uses sparse matrix factorization using Kronecker product to implement the Fourier unitary transform. This work implements perturbation theory for non-uniform transmission line. The extended Kalman filter (EKF) equations are derived for this state and measurement model and our real timeline voltage and current and distributed parameter estimates show excellent agreement with the true values based on MATLAB simulations. The use of sparse matrix factorization using Kronecker product ease the mathematical complexity and provides compact representation.

Limit Analysis Solution for Ultimate Bearing Capacity of Footing Resting on the Rock Mass with a Circular Void Subjected to Line Loading

Limit Analysis Solution for Ultimate Bearing Capacity of Footing Resting on the Rock Mass with a Circular Void Subjected to Line Loading

Synthesis Design of Bandpass Frequency Selective Surface With Multiple Transmission Zeros Using Slotline Structures

This article presents a synthesis method to design a new type of bandpass frequency selective surfaces (FSSs) with multiple transmission zeros (TZs). To briefly show the concept of our synthesis method, a generalized topology of the bandpass FSS based on cascaded slotline sections paralleled with bandpass resonators is first presented to map with an alternative <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> th-order bandpass filtering network with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$J$ </tex-math></inline-formula> -inverters and typical LC parallel resonators. Then, two kinds of composite LC parallel resonators, named as LC – LC and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}$ </tex-math></inline-formula> – LC parallel resonators, are introduced and discussed to replace the typical LC parallel resonators, which can produce TZs at skirts of the passband and increase the out-of-band selectivity. The derivations of equivalent relationships between the composite and typical LC resonators are given. Furthermore, for the exploration of bandpass FSS with multiple out-of-band TZs, the realization of these two discussed composite LC parallel resonators is exhibited by inductive and capacitive strip lines loading on slotline structures. The design curves and guidelines are given and discussed correspondingly. To validate our design concept, two FSS examples, a second-order bandpass FSS with four out-of-band TZs and a third-order one with five out-of-band TZs, are synthesized and designed. In final, these two designed bandpass FSS prototypes are fabricated and then measured by the free-space measurement method. The measured results show that the desired stable bandpass filtering performance and independently multiple out-of-band TZs are successfully realized.

Integrated generation-transmission expansion planning considering power system reliability and optimal maintenance activities

This paper evaluates lines repair and maintenance impacts on generation-transmission expansion planning (GTEP), considering the transmission and generation reliability. The objective is to form a balance between the transmission and generation expansion and operational costs and reliability, as well as lines repair and maintenance costs. For this purpose, the transmission system reliability is represented by the value of loss of load (LOL) and load shedding owing to line outages, and generation reliability is formulated by the LOL and load shedding indices because of transmission congestion and outage of generating units. The implementation results of the model on the IEEE RTS show that including line repair and maintenance as well as line loading in GTEP leads to optimal generation and transmission plans and significant savings in expansion and operational costs.

Evaluation of Viscoelastic Adhesion Strength and Stability of Composite Waterproofing Sheet Using Non-Hardening Viscoelastic Synthetic Polymer-Based Rubber Gel

Recently, a non-hardening type synthetic polymerized rubber gel (hereinafter referred to as NHV-SPRG) composite waterproofing sheet has been used on construction site as a new waterproofing technology. In this study, a test method is proposed in which a composite waterproof sheet is attached to an area of 150 mm in length and 100 mm in width on the mortar-based substrate specimen, and subsequently peeled off at 180 ° vertically to measure the “peel load (N)” at 10 points of 10 mm intervals (P1~P10, from 30 mm point to 120 mm point). Value obtained by dividing the average value of the measured peeling load by a width of 100 mm was defined as “viscoelastic adhesion strength (N/mm)”. The viscoelastic adhesive strength evaluated for the NHV-SPRG composite waterproof sheet of 4 types (VG-1, VG-2, VG-3, VG-4) was an average of 1.99 N/mm. To examine the effectiveness of the viscoelastic adhesive strength, the adhesion stability was evaluated based on the peel load’s coefficient of variation, grade of the linear regression line of the peel load, and peel load percent relative range in peel load for each section of the composite waterproofing layer. As a result, the VG-2 type was measured to have the highest viscoelastic adhesive strength, but the VG-1 type was confirmed to have the highest adhesive stability. Considering these results, it is judged that even a product with high adhesion can have varying stability in terms of performance that can affect construction precision. The test method and performance standard value for the viscoelastic adhesion strength proposed as an evaluation index through this study are expected to be used as a quality control standard to secure the on-site adhesion stability of the NHV-SPRG composite waterproof sheet.

A wide-input-range, low quiescent current LDO with E/D reference for piezoelectric energy harvesting

A low dropout regulator (LDO) for piezoelectric energy harvesting with low quiescent current of 3 μA is designed and proposed in this paper. The proposed LDO has an output voltage of 3.3 V, and it can provide a maximum output current of 50 mA to the load over a wide input voltage range of 3.6 V to 15 V. An E/D reference is integrated in the circuit, which can provide a reference voltage of 300 mV and bias current for the LDO. The proposed LDO has been designed and implemented in 250 nm BCD process, which uses merged voltage follower (MVF) buffer, and the simulation results have verified the proposed LDO has good transient and stability performance. The line regulation and load regulation of the LDO are 0.237 mV/V and 0.052 mV/mA. When the load current is varied from 0.1 mA to 50 mA, the maximum undershoot and overshoot are 52 mV and 50 mV, respectively.

Decentralized Active Power Management in Multi-Agent Distribution Systems Considering Congestion Issue

Recently, due to the restructuring of power systems and the high penetration level of local renewables, distribution systems have encountered with the complexity of power management. Therefore, the modern systems would be operated in a multi-agent structure which facilitates the power management as well as privacy protections of independent entities. In this structure, the distribution system is assumed to compose of several agents who independently schedule their local resources in order to maximize their own profits. Consequently, this paper provides an efficient peer-to-peer (P2P) active power management framework in a multi-agent distribution system while considering network constraints (i.e., line loadings and losses). In this context, in the proposed P2P scheme, the distribution system operator (DSO) model the network constraints in the form of line-usage costs within the transactive signals. Respectively, the developed transactive control signals enable the DSO to model the power loss as well as alleviate the congestion in the grid. Therefore, the agents automatically consider the network constraints in their power transactions management procedure without any direct interferences of the DSO in their resource scheduling. Finally, the proposed model is implemented on the modified-IEEE-37-bus-test system in order to investigate its effectiveness in the energy management of multi-agent systems.

Optimal Power Flow Based DR in Active Distribution Network With Reactive Power Control

Demand response works as a bridge to enable activities between end customer and distribution network operators. Previously, most of the demand response work is concerned about maintaining supply–demand balance and reducing peak load demand without acknowledging distribution network behavior. This article presents a demand response scheme for an active distribution network via the operation of an unbalanced feeder line and consumer loads. The day-ahead dynamic price is coupled with active distribution network constraints to prevent the formation of new peaks. To tackle up the complexities of unbalanced network and distributed generation (DG) integration, the merits of symmetrical domain components are utilized. Power electronically interfaced DG reactive power component is also considered for constant power and voltage mode of operation. For optimizing the distribution network, optimal power flow is modified to achieve social welfare with distribution network constraints. The performance and computational efficiency of the proposed algorithm are verified through extensive case studies.

Investigation on mechanical and microstructural evolution of lithium-ion battery electrode during the calendering process

To increase battery capacity and improve electronic conductivity and electrochemical performance, lithium-ion battery electrodes are produced using a calendering process. This work aims to reveal the evolution of mechanics and microstructure during the calendering process, while a predictive model was derived to determine the thickness and porosity. Here, the discrete element method simulations and calendering experiments were adopted to analyze the microscale and macroscale responses. A predictive model was supplemented using the Heckel equation. Furthermore, the electrodes were manufactured under incremental line load. According to the electrode morphology, the deformation mechanism was summarized: Particle pulverization, secondary particle fusion, binder network compression and the current collector's surface deformation. The increase of the electronic conductivity is related, on the one hand, to the conductive path inside the electrode being improved and, on the other hand, to the tightening of the contact between the coating and the current collector • The discrete element method is taken to analyze the microscale and macroscale response. • A predictive model is derived for the determination of the thickness and porosity. • The deformation mechanism is summarized according to the electrode morphology.

Enhancing static voltage stability of a power system in the presence of large-scale PV plants using a battery energy storage control scheme by the probabilistic technique

This paper aims to investigate the impact of large-scale photovoltaic plant (LS-PVP) controllers on the voltage stability (VS) of a power system. Besides, a new control strategy is proposed for the large-scale battery energy storage system (LS-BESS) to enhance a power system integrated with LS-PVPs, especially VS. To this end, a probabilistic technique, based on the stochastic nature of LS-PVPs and loads, is employed to accurately evaluate the impact of LS-PVPs on the system. Next, a new coupling between the optimization algorithm and the probabilistic technique is proposed to determine the optimal number, location, and capacity of the LS-BESSs by the probabilistic particle swarm optimization (PPSO) algorithm. The objective function is then used to simultaneously maximize the total VS and minimize the total power losses, line loading, as well as investment costs of LS-BESSs. Furthermore, technical performance indices (TPIs) are used for a more comprehensive investigation to compare the proposed solution to the synchronous generators. Finally, several disturbances occurring in the Nordic system are used to validate the effectiveness of the proposed approach, using the Monte Carlo simulation (MCS) method. According to the results, when a fault occurs, a system integrated with LS-PVPs in the stressed area does not operate better than synchronous generators. Therefore, an advanced control method is required to reduce undesirable effects of LS-PVPs. Using the proposed solution, voltage instability was prevented, LS-BESS investment costs were minimized, and negative effects of LS-PVPs on the system were reduced. Besides, costs required for expanding the transmission network as well as communication between controllers and reactive power compensation devices were reduced.

배전계획용 배전선로 부하예측 모델의 입력변수에 관한 고찰

The importance of the power distribution planning is increasing due to expansion of distributed generation in distribution system. The distribution planning is based on accurate load forecasting. Recently, machine learning-based load forecasting models have been developed and applied in distribution planning. However, since the performance of the machine learning-based load forecasting model depends on the combination of input variables, it is important to select input variables. This paper proposed the process of selecting input variables for an ensemble based load forecasting model. The input variable of the distribution line load forecasting model was selected through correlation analysis of predictable input variables, then the improvement of forecasting performance with selected input variable was analyzed by comparing the forecasting and the actual value. In addition, the importance of the selected input variables and the validity of the proposed process were analyzed through XAI analysis.

Effects of Conditional Changes on High-Voltage Direct Current Transmission Line Characteristic

The high-voltage direct current (HVDC) transmission system, which links the Gurun Substation of the National Electric Authority of Malaysia (Tenaga Nasional Berhad, TNB) with the Khlong Ngae Station of the Electricity Generating Authority of Thailand (EGAT), has been extensively researched to achieve the highest quality because it is the largest of its kind in Thailand, and there is a plant to expand its transmission power. However, the impact on the whole system is under-researched. To study and develop this system, the HVDC transmission line is modelled with the MATLAB/Simulink program and a laboratory setup to investigate the effect of transmission line distance, load power, and voltage on power loss, voltage drop, and waveform. The HVDC transmission line parameters are calculated from the actual transmission line parameters and converted to the simulation model parameters using the per-unit method. The model is verified and tested by the simulation program before creating the experimental setup. The simulation and experimental results demonstrate the effects of changing system conditions via the three aspects. All the three conditions directly affect the HVDC transmission line; nevertheless, they affect each aspect differently.

Multi-objective optimal siting and sizing of BESS considering transient frequency deviation and post-disturbance line overload

With the development of renewable energy sources, more frequent and severe active power disturbances emerge in power systems, and jeopardize the frequency stability and line loading security. The battery energy storage system (BESS) is able to adjust output power flexibly, and an attractive solution to improve frequency dynamics and power flow distribution. This paper proposes a multi-objective optimal siting and sizing scheme for the BESS to arrest frequency excursion and mitigate line overload under major disturbances. First, an extended average system frequency model is developed to estimate the required transient frequency regulation capability (TFRC) for frequency stability, and the post-disturbance power flows. Then, taking the required TFRC and line capacity as constraints, a multi-objective optimization model is established to minimize the life cycle cost of the BESS and generation cost. Furthermore, based on the linear weighted method, big-M method, and multi-cut generalized Benders decomposition, the intractable optimization model is transformed into a master problem for investment decision making, and a set of subproblems accounting for normal operation, frequency stability and line loading security. Additionally, the master problem and subproblems are solved iteratively to determine the location and capacity of the BESS. Case studies are conducted to validate the proposed scheme, showing superior performance in improving frequency nadir and alleviating post-disturbance line overload.

Stability predictions for excavations of mountain tunnels based on [BQ] method and its field verification

In response to the engineering problems often encountered during the construction of mountain tunnels, the aim of this study is to overcome the inability of numerical simulation methods to rapidly predict tunnel construction based on the [BQ] method of classifying surrounding rock grades. Numerical simulations were carried out using FLAC3D6.0 software based on previous empirical formulas for each parameter of the GSI scores and Hoek-Brown criterion. Relying on the Luanlu Highway Tunnel Project, the engineering problems of the Nianpan and Dahongyan tunnels were firstly identified, followed by numerical simulations to quickly obtain construction predictions for the proposed changes, and finally, engineering monitoring was carried out to verify the feasibility of the method. The results indicate that [BQ] = 311 for the water gushing section of the Nianpan Tunnel, which should be changed from Class III to IV surrounding rock and constructed according to the support scheme for Class IV surrounding rock, corresponding to GSI[BQ] = 43. The maximum load-bearing ratios of the secondary lining for ordinary Class III, seepage Class III and Class IV surrounding rocks are 24.2 %, 25.4 % and 34.7 % respectively. For the Dahongyan Tunnel, the change in the length of the anchors should be adjusted to from 3.0 m to 3.5 m and the distance of the secondary lining from the excavation face changes from 40 m to 46 m. Moreover, the secondary lining load sharing ratio at the monitoring point of the maximum load of the section secondary lining generally doesn’t exceed 35 %. The method can be used as a reference for other tunneling problems.

Implementation of the Elrod Algorithm in Practical Design of an Axial Lubricant Supply Groove in Journal Bearings

Abstract The Elrod algorithm was implemented to study the effects of axial lubricant supply groove parameters, i.e., groove length, width, and location, on the performance of a one-axial groove journal bearing, taking into consideration thermal effects. The results and presented recommendations will assist bearing designers in determining the groove’s preferred angular location and main dimensions to achieve a solution in terms of low total power loss and high minimum film thickness. It is suggested that with regard to low total power loss and high minimum film thickness, for a lighter loaded bearing, the axial groove should be located in the angular range of 100–140 deg to the load line with a groove length ratio Lg/L over 0.6 or the angular range of 300–350 deg with an Lg/L over 0.75. For a heavier loaded bearing, it is suggested that the groove be placed at the angular range of 80–115 deg with an Lg/L over 0.6.

어선검사 방법 및 법규 개선에 관한 연구 - 소형어선 전복사고 사례를 중심으로 -

In the event of capsized accident of fishing boats, life accidents such as death, disappearance, and injury of sailors occur during the ship capsized process, and ship owners suffer enormous economic losses from the capsized accident. Therefore, in order to prevent the same capsized accident, it is necessary to expand to small fishing boats with a total tonnage of less than 20 tons in consideration of the type of fishing permitted and the type of fishing gear that are currently applied only to fishing boats with a length of 24 meters or more. In addition, practical and effective inspection regulations are needed, such as marking additional stability inspection and load lines depending on the installation of heavy fishing equipment used for fishing such as cranes, and strengthening temporary inspection regulations to prevent the same accident from occurring again. Therefore, based on the recent five-year decision by the Korea Maritime Safety Tribunal from 2017 to 2021, a study on the causes of small fishing boat capsized accidents with a length of less than 24 meters and problems with small fishing boat inspection regulations was sought

Enhanced stability and failure avoidance of hydropower plant in contingent island operation by model predictive frequency control

The challenges of contingent island operation of hydropower plants are addressed by proposing an enhanced frequency control with advanced control algorithms. The study is based on a real power plant and considers the relevant power system in its entirety along with the load and transmission lines. Integrated transfer functions between the guide vane opening of a hydro turbine and the frequency of the associated generator were determined by in-situ identification. A model predictive controller, a fractional order PID controller, and a PID controller utilizing integral absolute error and integral time absolute error criteria were designed and developed. The performance of the proposed algorithms with the identified plant model was tested on a NI-cRIO 9049 FPGA platform. Improved frequency control in terms of setpoint change was achieved with the MPC and FOPID controllers. The MPC controller also features betters disturbance rejection compared to conventional PID controllers, which are tuned according to integral error criteria. The considered algorithms have been simulated in different operating scenarios, such as variations of active power load and transmission length. The proposed approach enhances stability and consequently avoids operational failures of hydropower plants in contingent islanding mode.

Laser bending angle and deformation mechanism under different auxiliary loads

Auxiliary load laser forming is a new direction developed based on laser forming. This direction has the advantages of a large forming angle and high surface quality of the workpiece and achieves the effect of traditional mechanical forming. Currently, the auxiliary load is applied in a single way, which will not be conducive to the enrichment and development of this direction. Accordingly, four auxiliary methods are proposed, and these different approaches are modelled. The bending angles of these different methods are compared, and the deformation mechanism is discussed. Results showed that the four methods can effectively increase the bending angle. Amongst them, method 3 can effectively increase the bending angle by 4.51 times because the positive bending moment effect formed by the line load and the negative bending moment effect formed by the surface load are conducive to the increase in bending angle. The bending angles under the four methods linearly increase with the increase in load value. The larger the high-temperature distribution area is at the same temperature value, the larger the bending angle will be.

Bi-level planning and scheduling of electric vehicle charging stations for peak shaving and congestion management in low voltage distribution networks

Most existing algorithms for electric vehicle charging station (EVCS) planning and scheduling of electric vehicles (EVs) do not consider the uncertain behavior of EVs and distribution networks, including the EV arrival and departure times, user driving needs, and realistic residential load and generation profiles. This paper proposes a bi-level planning and operation framework that determines the optimal locations of EVCS and scheduling of EVs to reduce peak load and network congestion in low voltage distribution networks by considering uncertain EV and distribution network behavior. Planning of EVCS is performed to minimize voltage deviations and distribution network losses. The priority-based scheduling algorithm uses the vehicle-to-grid (V2G) and grid-to-vehicle (G2V) technology to charge the EVs during high priority periods to meet the user requirements and discharge during low or medium priority periods to reduce the peak load and thermal overloading in distribution feeders. Based on an Australian scenario, the proposed method has been tested on the IEEE low voltage test feeder. Uncoordinated scheduling of EVs is also implemented and compared with the proposed strategy. The results show that installing EVCS at the optimal locations can reduce the network losses and voltage deviations by 39.38 per cent and 15.32 per cent, respectively. It is also shown that the proposed scheduling of EVs can reduce the peak load of distribution substations and lower the network congestion without affecting the EV charging requirements. With a 55 percent penetration of EVs, the peak load and thermal overload in distribution lines are reduced by 20.53 per cent and 5.88 per cent, respectively.

Automated routing of feeders in electrical distribution grids

The energy transition in Europe is bringing a high number of decentralized generation units and new types of loads. This change in the load structure increases the complexity of planning processes, creating a need to reinforce and expand electrical distribution grids. Automating planning processes can help to accelerate and optimize expansion and reinforcement measures. This paper presents a modular method for automated routing based on rendered images of geographic maps and territory information in medium- and low-voltage grids with regards to economic factors and technical requirements. Optimized routes are determined on the basis of geographic information and under consideration of underground construction costs for cables depending on ground characteristics. Subsequently, the generated synthetic grids are benchmarked against real low-voltage grids of a German grid operator, Westfalen Weser Netz GmbH. The geographical comparison shows a significant reduction of trenches and cables. The comparison of the power flow results shows similar line loads and voltage bands for the synthetic and the real grids. This comparison with real grids confirms that the developed method is suitable for the automated planning of routes and configuration of feeders and thus it is an important contribution to automate the planning processes in distribution grids.