Load Transfer Scheme Research Articles

Research on load transfer scheme optimization with probabilistic graphical computing based distribution network operation mode verification

In this paper, an optimization method for distribution system load transfer scheme with consideration of the operation mode verification is proposed. The method aims to recover the distribution system from the largescale power outage caused by complete shutdown of the substations. Firstly, a physical-probabilistic-network (PPN) model is introduced to estimate the operation mode of the distribution network by using belief propagation algorithm to recognize the states of switches. Then, a two-stages optimal transfer scheme which takes both the shortest recovery time and maximum load recovery rate as objectives is brought forward to determine alternative feeders for the outrage loads. The substations with high probability of overload after the first-stage of optimization are identified as the “weak links” and the second-stage optimization strategy which considers the capacity constraints is applied to further transfer the load from the “weak links” to their neighbours. Thus, the overload chances for the “weak links” are reduced and the overall load recovery rate is improved. Case study results prove that the verification of the distribution network operation mode can help improve the accuracy of the two-stages optimal load transfer scheme. Meanwhile, the proposed algorithm can effectively reduce the recovery time of the outage loads.

Load Transfer Path Search and Its Evaluation between Networks in Consideration of the Mobile Energy Storage of Electric Vehicles

Load transfer is an important way of restoring a power supply after equipment failure or maintenance. However, current methods ignore cooperation between networks and users, and they also fail to take into account the vehicle-to-grid (V2G) potential of electric vehicles (EVs). In this paper, a load transfer scheme between transmission and distribution networks is proposed, considering the mobile energy storage capacities of electric vehicles. First, the mobility characteristic and the available discharge capacity of EVs are analyzed on the basis of the parking generation rate. Then, the breadth-first algorithm is used to search the load transfer paths within and between stations, and an edge matching method is proposed to realize the conversion between networks with different voltage levels. Lastly, the optimal combination weighting method was adopted to combine subjective and objective index weights and to evaluate power supply paths. The effectiveness of the proposed scheme is validated in a case composed of an IEEE 30-node network and an IEEE 57-node network, with four typical scenarios.

Research on load transfer strategy optimisation with considering the operation of distributed generations and secondary dispatch

In this study, a three-stage optimisation method for distribution system load transfer scheme with consideration of the participation of distributed generations (DGs) is proposed. The algorithm aims to recover loads from the large-scale power outage caused by substation-complete-shutdown accidents (SCSAs), thus improving the power supply reliability. First, the principle of the SCSA load transfer strategy considering DGs and the secondary dispatch is introduced. The capacities of DGs were used to provide the additional power supply in grid-connected or island operations. Meanwhile, to relieve the stress of the backup substation for further load transfer, a secondary dispatch strategy is proposed to dispatch loads among the direct-connected and secondary-connected substations. Afterwards, a three-stage optimisation model is built to obtain the optimal load transfer scheme. The first-stage optimisation determines the island partitions in the unrecovered areas. The second-stage optimisation comprises a tie-line transfer model considering the load importance and the recovery time. The third-stage optimisation intends to determine the optimal secondary dispatch to achieve a better overall recovery rate. Case study results prove that the proposed three-stage optimisation method can improve the overall load recovery rate while ensuring the reliability of important loads and the operation safety of the system.

Comparison Between Torsional Spring Constants of Rectangular and V-Shaped AFM Cantilevers

The properties of force-sensing micro-cantilevers are of fundamental importance for measurements employing atomic force microscopy (AFM) techniques. Due to the well-known arguments of Sader, it is generally accepted that V-shaped cantilevers are more sensitive to lateral forces than rectangular ones. We present results of numerical (finite element modelling) and experimental comparison between torsional spring constants of rectangular and V-shaped commercial AFM cantilevers. As representative example of such beams, we considered AFM probes available commercially. In particular, we tested scaled-up models of V-shaped cantilevers which had the same geometrical shapes as commercial AFM cantilevers. Both the rectangular and the V-shaped larger scale models were made of the same material; they had the same length, thickness, normal spring constant, as well as the same location and shape of the tip base. In the experiments and the simulations, an external lateral load was applied to the free end of the tip. A good agreement between the experimental work and finite element method (FEM) simulations was observed. The results show that the torsional spring constant of the V-shape cantilevers considered here was greater than that of the equivalent rectangular beams by up to 45%. The discrepancy with the results from Sader should be caused by differences in both the load transfer scheme and the geometrical shapes of the V-shaped beams.

A Moving Coordinate Numerical Method for Analyses of Electromagneto-Mechanical Coupled Behavior of Structures in a Strong Magnetic Field Aiming at Application to Tokamak Structures

Analysis of the electromagneto-mechanical coupling effect contributes greatly to the high accuracy estimation of the EM load of many EM devices, such as a tokamak structure during plasma disruption. This paper presents a method for the numerical analysis of the electromagneto-mechanical coupling effect on the basis of Maxwell's equations in the Lagrangian description and staggered load transfer scheme, which can treat the coupled behaviors of magnetic damping and magnetic stiffness effects at the same time. Codes were developed based on the ANSYS development platform and were applied to solve two typical numerical examples: the TEAM Problem 16 and dynamic behavior analysis of a shallow arch under electromagnetic force. The good consistency of numerical results and experimental data demonstrates the validity and accuracy of the proposed method and the related numerical codes.

Voltage Unbalance Reduction in Low Voltage Feeders by Dynamic Switching of Residential Customers Among Three Phases

To dynamically reduce voltage unbalance (VU) along low voltage distribution feeders, a distributed intelligent residential load transfer scheme is proposed. In this scheme, residential loads are transferred from one phase to another to minimize VU along the feeder. The central controller, installed at the distribution transformer, observes the power consumption in each house and determines the house(s) to be transferred from an initially connected phase to another. The transfer is carried out by the help of a static transfer switch, with a three-phase input and a single-phase output connection, through which each house is supplied. The steady-state and dynamic performances of the proposed load transfer scheme are investigated by MATLAB analyses and PSCAD/EMTDC simulations.

The Development of Load Transfer Decision Assistant System for Regional Power Grid

According to the features of distribution network, this paper designed the implementation scheme of load transfer decision assistant system. Based on the load transfer path search method and expert system method to analysis the load transfer path, the economic index and safety index evaluate function was established by the switching times , the grid loss, impulse current, load rejection and off-limit value. Through the economic security indicators, the feasibility and risk of load transfer scheme was determined.

A Novel Load Transfer Scheme for Peak Load Management in Rural Areas

This paper proposes a novel peak load management scheme for rural areas. The scheme transfers certain customers onto local nonembedded generators during peak load periods to alleviate network under voltage problems. This paper develops and presents this system by way of a case study in Central Queensland, Australia. A methodology is presented for determining the best location for the nonembedded generators as well as the number of generators required to alleviate network problems. A control algorithm to transfer and reconnect customers is developed to ensure that the network voltage profile remains within specification under all plausible load conditions. Finally, simulations are presented to show the performance of the system over a typical maximum daily load profile with large stochastic load variations.

An enhanced load transfer scheme for power distribution systems connected with distributed generation sources

This paper presents an enhanced load transfer scheme for power distribution systems connected with distributed generation sources. Load transfer is an important approach to improve the reliability ...

Conservative load transfer along curved fluid–solid interface with non-matching meshes

We investigate the effect of curvature on the accuracy of schemes used to transfer loads along the interface in coupled fluid–solid simulations involving non-matching meshes. We analyze two types of load transfer schemes for the coupled system: (a) point-to-element projection schemes and (b) common-refinement schemes. The accuracy of these schemes over the curved interface is assessed with the aid of static and transient problems. We show that the point-to-element projection schemes may yield inaccurate load transfer from the source fluid mesh to the target solid mesh, leading to a weak instability in the form of spurious oscillations and overshoots in the interface solution. The common-refinement scheme resolves this problem by providing an accurate transfer of discrete interface conditions across non-matching meshes. We show theoretically that the accurate transfer preserves the stability of the coupled system while maintaining the energy conservation over a reference interface. Finally, we introduce simple analytical error functions which correlate well with the numerical errors of the load transfer schemes.

Assessment of conservative load transfer for fluid-solid interface with non-matching meshes

We present a detailed comparative study of three conservative schemes used to transfer interface loads in fluid–solid interaction simulations involving non-matching meshes. The three load transfer schemes investigated are the node-projection scheme, the quadrature-projection scheme and the common-refinement based scheme. The accuracy associated with these schemes is assessed with the aid of 2-D fluid–solid interaction problems of increasing complexity. This includes a static load transfer and three transient problems, namely, elastic piston, superseismic shock and flexible inhibitor involving large deformations. We show how the load transfer schemes may affect the accuracy of the solutions along the fluid–solid interface and in the fluid and solid domains. We introduce a grid mismatching function which correlates well with the errors of the traditional load transfer schemes. We also compare the computational costs of these load transfer schemes. Copyright © 2005 John Wiley & Sons, Ltd.

Rule-based approach to load transfer to alternate supplies based on the phase of the residual voltage on the disconnected busbar

Transfer techniques and a rule-based approach to an in-phase load transfer scheme for secondary selective substations are developed. The transfer scheme, with its developed transfer techniques and rule based algorithm, integrates into a microcontroller-based in-phase transfer controller to maintain the continuity of power supply to process loads. The rule sets initiating conditions, blocking transfer criteria, load shedding schedules and possible events. It provides a safe and successful bus transfer system. Operations of the load transfer scheme with simulated load conditions have been tested through the in-phase transfer controller. The results of computer simulation and test measurements show that the load transfer operation is performed successfully. The inrush current, transient torque and service reliability can also be improved by using this transfer scheme.

Structural Analysis of Concrete Pavement Systems

Performance of concrete pavements is controlled by the behavior and performance of the jointing system used, especially the performance and load transfer efficiency of the joint. A finite-element program is presented that includes the analysis of slabs with various joint systems in PCC pavements. Dowelled joints, joints with aggregate interlock, and joints with various types of load transfer schemes can be taken into account during the analysis of the slab under load rather than analyzing the slab and joint systems separately and superimposing the results. The program described is also capable of analyzing slabs comprised of two layers with different material properties, either bonded together or unbonded. Slab thickness, slab modulus values, and subgrade support values can each be varied at each node point in the program to evaluate jointed slabs of nonuniform stiffness and nonuniform support.

A Least Squares Estimate of Satellite Attitude

A Least Squares Estimate of Satellite Attitude