Transmission Power Flow Research Articles

Optimal configuration and power scheduling algorithm of distributed power system with large range power flow transfer

The distributed power system is composed of multiple distributed energy sources, loads and energy storage devices, which have the characteristics of decentralization and complexity. Therefore, a distributed power system optimal allocation and power dispatching algorithm considering large-scale power flow transfer is proposed. Calculate the power flow values of different nodes, and construct an optimization model according to the results to complete power flow transmission. In the inner loop, the current dispatching is set as the objective, and in the outer loop, the voltage dispatching is set as the objective. Distributed power system scheduling is completed by double closed-loop vectors. The experimental results show that the power oscillation amplitude of this method is small and the duration is short.

Generalized acoustic impedance metasurface

Impedance theory has become a favorite method for metasurface design as it allows perfect control of wave properties. However, its functionality is strongly limited by the condition of strict continuity of normal power flow. In this paper, it is shown that acoustic impedance theory can be generalized under the integral equivalence principle without imposing the continuity of power flow. Equivalent non-local power flow transmission is instead realized through local design of metasurface unit cells that are characterized by a passive, asymmetric impedance matrix. Based on this strategy, a beam splitter loosely respecting local power flow is designed and demonstrated experimentally. It is concluded that arbitrary wave fields can be connected through arbitrarily shaped boundaries, i.e. transformed into one another. Generalized impedance metasurface theory is expected to extend the possible design of metasurfaces and the manipulation of acoustic waves.

Vibration energy transfer in variable stiffness laminated composite panel with a cutout

This study investigates the vibration power flow transmission behavior of laminated composite plates with a cutout and a variable angle tow (VAT) design. The steady-state response of the harmonically excited plate is determined. The power flow density vectors (PLDV) are used to show the vibration transmission paths. The effects of the VAT design parameters on the dominant power flow paths within the plate are explored. It shows that the forced vibration responses and vibration energy transfer within the structure can be tailored with fiber layer scheme. The findings benefit enhanced vibration suppression of composite plates with a cutout.

Energy transfer and vibration suppression of laminated composite plates coupled with a line hinge

This study investigates the vibration energy flow transmission behavior of laminated composite plate structures coupled with a line hinge. The time-averaged vibration energy transfer is determined using the substructure-based power flow analysis (SPFA) method. The effects of the fiber orientation, boundary conditions and the position of the coupling hinge on the vibration transmission path and its level are examined. It is demonstrated that the fiber orientations can be used to modify substantially the power flow transmission path and locations of energy sinks. Enhancement of vibration suppression of the coupled structure can be achieved by tailor designing the fiber angles.

A Quasi-Two-Stage Isolated Bidirectional Buck-DAB Converter for Wide Input Voltage Range

In this article, a quasi-two-stage buck-DAB (QBDAB) converter is proposed for improving the performance of the conventional dual active bridge (DAB) solution under a wide voltage range. For the proposed QBDAB converter, the DAB can always work under voltage matching conditions for wide voltage range applications, and the gain is adjusted through the added front-end circuit. The front-end circuit is similar to a buck converter, while only part of the transmission power flows through the circuit, which could also reduce the burden of achieving ZVS of the front-end circuit. Therefore, compared with the traditional two-stage buck-DAB converter solution, the related loss for the buck circuit can be reduced. The working principle, power transfer characteristics, and full load range ZVS design are analyzed deeply in this article. A detailed comparison of the QBDAB and other related combined buck+DAB topologies is also presented. Finally, the effectiveness of the proposed QBDAB is verified through experimental results from a 1kW prototype.

Reproduction and Verification of Transmission Power Flow Using Power Production Cost Simulation Model

Reproduction and Verification of Transmission Power Flow Using Power Production Cost Simulation Model

Generalized Smooth Functions for Modeling Steady-State Response of Controls in Transmission and Distribution

• Present generalized continuous functions to model steady-state response of grid controls. • Employ homotopy and limiting techniques for scalability and robustness. • Traditional controls as well as newer controls are mapped to smooth continuous functions. • Applied to both transmission and distribution power flow to scale to systems as large as 70k buses. The promise of renewables and the consequent fluctuations in the power grid necessitate a robust simulation framework to capture the steady-state behavior of new controls. However, standard non-differentiable models of control mechanisms produce divergence and/or numerical oscillations in large power flow simulations. In this paper, we describe a methodology that introduces two generalized class C 1 smooth basis functions to model the steady-state of various controls in power flow for transmission and three-phase distribution as well as optimization settings. These models are accompanied by homotopy methods and limiting techniques in the simulation engine that ensure scalable and robust convergence. We map standard power flow controls, typically modeled as non-differentiable functions in commercial tools, to the proposed class C 1 basis functions and demonstrate the benefits for robustness in comparison to commercial tools on test cases as large as the US Eastern Interconnection system. We further extend the approach to model non-standard devices such as STATCOMs and the steady-state effects of inverter-based generators in three-phase distribution and optimization problems.

Fast tuning of transmission power flow routers for transient stability constrained optimal power flow under renewable uncertainties

This paper proposes a robust transient stability constrained optimal power flow (OPF) problem that addresses the impact of renewable uncertainties by the coordination of power flow router (PFR) tuning and generation re-dispatch. PFR refers to a general type of network-side controller that enlarges the feasible region of OPF problem. The coordination between network-side and generator-side control in the proposed model is more general than the traditional methods which focus on generation dispatch only. Applying semidefinite programming (SDP) relaxation and scenario approach allows us to simplify the original robust optimization problem into a scenario-based SDP problem. Then, an offline–online solution framework is developed to solve the problem efficiently. Under this framework, the time-consuming transient stability analysis and scenario reduction are carried out at the offline stage. At the online stage, we only need to solve a lower-dimensional deterministic problem based on the information obtained offline, which achieves fast implementation of PFR parameter tuning and generation re-dispatch. The proposed method is verified on a modified New England 39-bus system. Numerical results demonstrate that the proposed method is efficient and achieves lower generation cost without compromising the robustness of transient stability under renewable uncertainties. • A robust TSC-OPF is proposed with power flow routers and renewable uncertainties • The model introduces a coordination of network control and node power control • An offline–online solution framework is designed to efficiently solve the problem • The model achieves lower cost without compromising the stability robustness

Faster identification of redundant security constraints in SCUC

One of the main reasons why it has long been difficult to solve the security-constrained unit commitment (SCUC) problem is that there are a large number of security constraints in SCUC such as transmission constraints in the base case and N-1 criterion constraints, and adding all of them to the model will make the solution of the problem very challenging. Related research shows that most of these security constraints are redundant for solving SCUC, so identifying and eliminating most of the redundant security constraints in the model will greatly improve the speed of solving SCUC. In this paper, a fast and efficient algorithm is proposed for identifying redundant security constraints in SCUC. The proposed algorithm introduces parameters in the basic transmission constraints to additionally limit the transmission capacity. In the N-1 constraints based on Line Outage Distribution Factor (LODF), more redundant constraints are identified and removed in the model by comparing the upper limit of transmission line capacity with the maximum transmission power flow that may occur in the line when the system is running. More importantly, the proposed algorithm does not need to solve additional auxiliary optimization problems or iteratively solve multiple models, and only needs to identify a large number of redundant security constraints through a quick calculation and logical judgment in the early stage of model establishment. It has been tested on the IEEE 30-bus system and the IEEE 118-bus system. The numerical experimental results show that the algorithm can identify 98.52% and 99.3% of redundant security constraints, and the computational speed is 1.63 times and 17.85 times of the full model, respectively. Compared with other methods in the literature, it has more advantages in computational efficiency.

A multi-shift phase angle control strategy for bidirectional wireless power transmission system

Using the charging and discharging capability of battery-based loads and a two-way wireless energy transmission system, grid-load balancing can be achieved in both directions. The system can be applied to many locations by deploying power flow in real time. In the scenario of vehicle network interconnection, it realizes peak-shaving and valley-filling to optimize grid dispatching capability; in the scenario of modular satellite interconnection, it realizes load balancing and effectively improves energy utilization. Therefore, a suitable control strategy is needed to precisely change the output power flow and the output power magnitude. A method to coordinate multiple phase shifting angles in the system hierarchy to achieve power flow regulation is proposed for a bidirectional wireless power transmission system with a dual full-bridge topology. In this paper, we first model the bidirectional transmission system and analyze the relationship between each phase shift angle and active and reactive power. The traditional control strategy is optimized by reducing the number of control loop variables and using the system power factor angle instead of the difficult-to-control external phase shift angle, while ensuring the voltage gain for optimal system efficiency. Finally, only two control loops are used to control the direction and magnitude of the output power respectively, and the effectiveness and correctness of the control strategy are verified by using the corresponding simulation experiments to achieve smooth switching of the bidirectional electric power transmission power flow.

Dynamic Analysis of Gear Rattling of a Certain Type of Dual-Clutch Transmission

In order to accurately explore the transmission rattling phenomenon and the influence of different factors on the dynamic characteristics of the gear rattling of the dual-clutch transmission under the condition of preselected gears, this paper establishes the gear rattling dynamics model of the transmission with the 1st gear without preselection and the preselected 4th gear, respectively; The model takes into account factors such as time-varying mesh stiffness, mesh damping, nonlinear oil film force, nonlinear backlash, and the drag torque generated by the clutch in the unengaged state. In addition, the feasibility of the dynamic model was verified by the bench test. On this basis, we took the gear meshing power and system power loss as quantitative indexes to analyze the influence of the preselected gear state and different parameters on the rattle vibration of the transmission. The results show that the pre-selected gear will not have a significant effect on the gears that have been rattled in the non-pre-selected state, and the torque fluctuation of the non-power flow shaft is aggravated by the influence of the transmission power flow branch and transmission ratio at different levels, which makes the overall rattling strength increase. In order to improve the transmission efficiency of the gear, the torque fluctuation of the input end of the system should be reduced as much as possible, and a larger lubricant viscosity can be appropriately selected, the inertia of the empty gear can be properly reduced, and the tooth clearance can be relaxed for selection.

Compilation of Load Spectrum of PHEV Transmission Assembly and Its Simulation Application

This paper presents a method for compiling the load spectrum of the transmission assembly of plug-in hybrid electric vehicles (PHEVs). Based on the analysis of the control strategy of the test vehicle, the power flow transmission route in the transmission assembly is different under different operation modes, so it is necessary to divide different load spectrum blocks according to the operation mode. Based on the big data survey of China’s national standard, it is determined that the typical working conditions are urban road working conditions, high-speed road working conditions, provincial road working conditions and poor road conditions. The mileage proportion of the various working conditions is 55:30:10:5, and the mileage of one cycle is 300 km. A total of three cycles are collected. After data processing and time-domain verification, based on the principle of maximum damage, the cycle with the largest pseudo damage is selected as the sample load data for load spectrum extrapolation. The rain flow counting method is used to count the sample load, and a two-dimensional kernel density estimation mathematical model with adaptive bandwidth is established to estimate the probability density function of the data. The extrapolated rain flow matrix is obtained through Monte Carlo simulation. The load spectrum of the two-dimensional rain flow matrix is transformed into a one-dimensional eight-stage program load spectrum by using a variable mean method, Goodman equation and equal damage principle theory. Finally, the fatigue life of the transmission assembly is simulated and calculated under the environment of Romax Designer simulation software. The two-dimensional kernel density estimation model with adaptive bandwidth is used to fit and extrapolate the load rain flow matrix of each hybrid mode of the PHEV, which solves the problem wherein the shape of the rain flow matrix of each hybrid mode of the hybrid electric vehicle is complex and difficult to fit. Finally, taking the after-sales maintenance data of this model from 2020 to the present as auxiliary proof, the failure components and the failure mileage life of the simulation test results are consistent with the results used by the actual users. This shows that the kernel density estimation model proposed in this paper can well fit the rain flow matrix of the PHEV load spectrum. The extrapolated load spectrum based on this model has high accuracy and authenticity. The method of compiling the load spectrum of the transmission assembly of a hybrid electric vehicle in this paper is effective.

Values and impacts of incorporating local flexibility services in transmission expansion planning

This paper presents a cost-based TSO-DSO coordination model to quantify the value of local flexibility services and analyze its impact on the transmission grid expansion and the system operation. Flexibility is provided to the DC power flow transmission grid model by microgrids within the integrated AC power flow distribution grid model. The model’s objective is to minimize the overall cost of transmission investments and procured flexibility and is achieved using a bilevel optimization approach where the power exchanges on all connected grid interfaces are controlled. Case studies using a combined test system of the IEEE RTS-96 transmission network interfacing multiple 33-bus distribution grids were performed to validate the model and assess the values and impacts of local flexibility on the transmission system expansion. The results showed that the proposed model modified the investment plan and dispatch of flexibility resources reducing the investment and operation cost of the transmission system.

Optimization of Voltage Security with Placement of FACTS Device Using Modified Newton–Raphson Approach: A Case Study of Nigerian Transmission Network

Power flow reliability, voltage security and transmission congestion management are paramount operational issues in a power system. Flexible AC transmission system (FACTS) controllers are suitable technologies that can provide compensation and dynamic control of power system transmission parameters to enhance effective performance and reliability. The interline power flow controller (IPFC), if optimally placed, can regulate the impedance of multiple lines to improve active power transfer capacity and voltage profile. This study examines the performance of IPFCs for voltage enhancement by suppressing fluctuation. A modified Newton–Raphson load flow problem with an incorporated IPFC variable has been formulated with the objective to improve voltage stability and maintain active power flow. The effectiveness of the proposed method was tested on the Nigerian 41 bus transmission network. The obtained result of the system with an IPFC placed at the weakest bus of the network was compared with Newton–Raphson load flow analysis of the same network without an IPFC. The results of load flow analysis for Case 1 (the system without an IPFC) showed that the transmission network without an IPFC had a real power loss of 4.699488 p.u., and reactive power loss of 4.467413 p.u., whereas the integration of an IPFC to the power flow formation in Case 2 resulted in the reduction in the transmission network’s overall losses to 0.55297 p.u. and −38.3329 p.u. The modified method proves effective as the power system network with an IPFC returns a more stable voltage profile and improves active power flow. In addition, this method, similar to all other mathematical optimization approaches, returns a strong accurate result but may be a drawback in terms of longer computational time compared with metaheuristic methods which are preferred for a larger network system.

Enhancement of Power Quality in Power Distribution Systems Using FC- TCR Based Compensation Systems

The development of modern electronic systems and increasing number of application areas (computers, office equipment, rectifiers, converters, speed control devices, uninterruptible power supplies, switched power supplies) has led to harmonic generation and reduced energy efficiency. The majority of loads are inductive in nature and the draw of reactive power has increased in networks and transmission lines resulting in problems with power quality. In addition to efficient power flow in transmission systems, there is also a need to compensate for the reactive power flow in order the meet the requirements of the load and system. As an alternative to traditional solutions, FACTS (Flexible Alternating Current Transmission Systems) has been developed in order to operate electrical systems efficiently and improve stability and power quality. Technological applications such as SVC, STATCOM, SSSC and active harmonic filter are becoming widespread in order to improve power quality. In this study, applications within the scope of FACTS systems are explained and analysis of a fixed capacitor-thyristor controlled reactor (FC-TCR) to improve power factor is discussed. A circuit model of the FC-TCR is developed as a simulation and used to investigate how power factor may be kept within desired limits by adjusting the firing angle of the thyristors under different load conditions. A comparative evaluation has been carried out to determine the effect of FC-TCR by presenting results before and after the load compensation process is applied. From the simulation it is observed that reactive power compensation can be achieved even for varying linear loads.

Optimal output power coordinated control strategy of distributed power flow controller

Distributed power flow controller (DPFC) is composed of multiple sub-units distributed on the line, which improves the power flow transmission capacity and ensures high reliability of the line. The overall performance and power losses of DPFC are the major concern, which is largely determined by the output power assigned to each sub-unit. This paper investigates the operating loss of its sub-units and analyzes the output of the DPFC device based on the topology of DPFC. Considering the total loss of the DPFC device, the capacity utilization rate of the sub-units and relative constraints, an optimal output power coordinated control strategy of DPFC multi-sub-unit is proposed. The simulation platform of PSCAD/EMTDC is used to develop the simulation model of a typical 110 kV system consisting of 10 groups of sub-units with different capacities. The simulation results show that the optimal output power coordinated control strategy proposed in this paper can greatly reduce the total loss of the device compared with the traditional methods, such as equipartition method and the capacity proportion method. And the capacity utilization rate of the operated sub-units can reach over 87.5%.

Research on road adaptability of roof bolter based on power flow transmission characteristics

Research on road adaptability of roof bolter based on power flow transmission characteristics

Energy flow and performance evaluation of inerter-based vibration isolators mounted on finite and infinite flexible foundation structures

This study investigates the vibration power flow behavior and performance of inerter-based vibration isolators mounted on finite and infinite flexible beam structures. Two configurations of vibration isolators with spring, damper, and inerter as well as different rigidities of finite and infinite foundation structures are considered. Both the time-averaged power flow transmission and the force transmissibility are studied and used as indices to evaluate the isolation performance. Comparisons are made between the two proposed configurations of inerter-based isolators and the conventional spring-damper isolators to show potential performance benefits of including inerter for effective vibration isolation. It is shown that by configuring the inerter, spring, and damper in parallel in the isolator, anti-peaks are introduced in the time-averaged transmitted power and force transmissibility at specific frequencies such that the vibration transmission to the foundation can be greatly suppressed. When the inerter is connected in series with a spring-damper unit and then in-parallel with a spring, considerable improvement in vibration isolation can be achieved near the original peak frequency while maintaining good high-frequency isolation performance. The study provides better understanding of the effects of adding inerters to vibration isolators mounted on a flexible foundation, and benefits enhanced designs of inerter-based vibration suppression systems.

Research on road adaptability of roof bolter based on power flow transmission characteristics

Research on road adaptability of roof bolter based on power flow transmission characteristics

Solution of the Optimal Reactive Power Flow Problem Using a Discrete-Continuous CBGA Implemented in the DigSILENT Programming Language

The problem of the optimal reactive power flow in transmission systems is addressed in this research from the point of view of combinatorial optimization. A discrete-continuous version of the Chu & Beasley genetic algorithm (CBGA) is proposed to model continuous variables such as voltage outputs in generators and reactive power injection in capacitor banks, as well as binary variables such as tap positions in transformers. The minimization of the total power losses is considered as the objective performance indicator. The main contribution in this research corresponds to the implementation of the CBGA in the DigSILENT Programming Language (DPL), which exploits the advantages of the power flow tool at a low computational effort. The solution of the optimal reactive power flow problem in power systems is a key task since the efficiency and secure operation of the whole electrical system depend on the adequate distribution of the reactive power in generators, transformers, shunt compensators, and transmission lines. To provide an efficient optimization tool for academics and power system operators, this paper selects the DigSILENT software, since this is widely used for power systems for industries and researchers. Numerical results in three IEEE test feeders composed of 6, 14, and 39 buses demonstrate the efficiency of the proposed CBGA in the DPL environment from DigSILENT to reduce the total grid power losses (between 21.17% to 37.62% of the benchmark case) considering four simulation scenarios regarding voltage regulation bounds and slack voltage outputs. In addition, the total processing times for the IEEE 6-, 14-, and 39-bus systems were 32.33 s, 49.45 s, and 138.88 s, which confirms the low computational effort of the optimization methods directly implemented in the DPL environment.