Power Tracing Research Articles

Reactive Power Tracing Index LQP_LT for Voltage Unstable Load Bus Identification in Power Systems

Existing power systems are significantly susceptible to voltage instability problem since such systems are stressed with the huge power transfers across the grids. To guarantee power system stability during stressed conditions, it is important to first identify the voltage unstable load buses to determine appropriate locations for under voltage load shedding. In this study, a new method is proposed for determining weak load bus locations by using reactive power tracing to develop a novel reactive power tracing capable index, named as LQP_LT. The reactive power tracing algorithm is integrated with the LQP_LT index formulation to generate priority ranking list of weak load buses. The LQP_LT index was tested on the 57 bus system and the resulting priority ranking list is found to have successfully determined the weak load buses for load shedding in the test system. Comparison with other stability indices revealed that the LQP_LT has better sensitivity and response towards determining the location of the weakest load bus for under voltage load shedding implementation.

Comparison of Weak Load Bus Detection using LQP_LT Index with PV and QV Analysis of PSS/E

Identification of weak load buses which contributes to voltage instability problem is crucial in order for an appropriate mitigation action to be executed. The current power system transmission is not only stressed to deliver high load demand at the receiving end but also facing new challenges brought by the penetratrion of renewable energy sources. This new scenario requires power system operation and analysis to be robust and fast in detecting the accurate weak load bus for correction action. Due to this, many online indices to detect weak load bus during power system contingency have been developed. Nevertheless, LQP_LT is of the latest index developed which ultimately has the reactive power tracing capability for weak load bus detection and generate priority ranking list of the weak load buses. This index was tested on IEEE 14 bus test system for different contingency scenarios. The results obtained from the LQP_LT index is compared and validated with the PV and QV analyses obtained using industrial graded PSS/E software. It was concluded that the LQP_LT index is found to be robust, efficient and need less computation time as compared to the execution of voltage stability analysis using the PSS/E Tool.

Power Tracing Monitoring incorporating Optimal Reactive Power Dispatch

General power flow studies do not manage to trace the contributors by generators on power losses in the whole power transmission system. Thus, power tracing approach is utilized to address this issue. Power tracing is a termed used to describe the contributors for the power losses dissipated on the transmission line. The traditional technique made use the knowledge of circuit analysis such as cut set theory. However, there was no element of optimization which can help to achieve the optimal solution. This paper presents the power tracing monitoring during voltage stability improvement process, implemented by optimal reactive power dispatch. In this study, the impact of power tracing on voltage stability variation was investigated. Evolutionary Programming (EP) was developed and utilized to incorporate power tracing, along with voltage stability improvement. A pre-developed scalar voltage stability index was incorporated to indicate the voltage stability condition. On the other hand, the voltage stability initiative was conducted via the optimal reactive power dispatch. The power tracing was monitored for both; the pre-optimization and post-optimization scenarios. Small system model was tested to realize the power tracing phenomenon, which is rather rare study in power system community. Results on power tracing obtained during the pre- and post-optimal reactive power dispatch revealed that not all generators will involve in the contribution on the total transmission loss in the system. This can be beneficial to power system operators for allocating the cost without discrimination in the long run.

Analytical Review of Power Flow Tracing in Deregulated Power System

Electric Power starts flowing when there is a Source and Sink gets connected. Transmission corridor facilitates that power to flow. The problem arises in the analysis of individual power through a common transmission corridor of a larger system which is called power flow tracing. In the pre-deregulated system, due to the monopolistic nature of governance, the consumer was nothing to say about the tariff or choosing its service provider. But in the free-market or deregulated market system, the price to be charged must be based on fair and transparent manner. So analysis of individual customer’s power in a common supply corridor is a major contribution towards the fair and transparent analysis of price. Efficient power flow tracing would make it possible to charge the generators and/or consumers on the basis of actual transmission facility used. This paper deals with the detailed procedure for obtaining active and reactive power tracing for the actual active and reactive power transmitted through a common corridor between generators and loads. Initially, from the Newton-Raphson based load flows, the line flows are computed and then the multiplying factors of the lossy lines are calculated using proportional sharing method. Finally, based on the multiplying factors, the contributions of each line to concerned loads are obtained for both active and reactive power flow tracing. The method is used elaborately in a Six-bus system and subsequently applied to standard IEEE-14 and IEEE-30 Bus test systems and the results are presented.

SCUC‐based optimal power tracing approach for scheduling physical bilateral transactions and its verification via an integrated power‐money flow analysis

This study discusses a security-constrained unit commitment (SCUC) based optimal power tracing approach, which adopts the proportional power tracing method to trace power flows of the network for simultaneously satisfying physical contract paths and financial contract quantities of bilateral transactions. Thus, optimal solutions of the proposed model, including unit commitment and generation dispatch of generators and angle statuses of phase shifters, would simultaneously meet physical and financial requirements of bilateral transactions, and in turn reduce the impacts of loop flows induced by bilateral transactions to third parties of the networked system. The proposed model is a mixed integer non-linear programming problem because of the non-linear proportional power tracing constraints, and the revised outer approximation algorithm is discussed to effectively solve the problem. The effectiveness of the proposed model is further evaluated via an integrated power-money flow analysis, based on the locational marginal price based energy payments and the min–max fairness policy based transmission usage charges. Numerical case studies show that the proposed model, as compared with traditional financial bilateral transaction models, presents potential advantages to avoid loop flows and reduce the impacts to third parties in terms of energy and transmission usage payments.

Transmission cost allocation by power tracing based equivalent bilateral exchanges

Transmission cost allocation by power tracing based equivalent bilateral exchanges

上游风电机组偏航控制对下游机组功率影响研究

目前风电机组偏航控制策略研究主要是集中在单台风力发电机组的最大功率追踪，没能考虑到尾流对下游风电机组功率的影响。因此本文主要围绕上游风电机组偏航状态下，其尾流中心偏移量进行系统的研究。根据现有的理论依据推到出尾流偏移量的简化计算公式，依据推公式在MATLAB中编程计算。得到尾流偏移量各参数之间的关系，并对参数之间的关系进行分析。随后在Bladed软件中建立风力发电机组模型，并利用得到的尾流中心偏移量，进行两台距离7倍风轮直径的风电机组在某一特定风向条件下，由上游风电机组主动偏航控制一定角度后，对两台机组功率的特性进行分析与总结。 At present, the research on the yaw control strategy of wind turbines is mainly focused on the maximum power tracing of a single wind turbine, which cannot take into account the influence of wake on the power of downstream wind turbines. Therefore, this paper mainly focuses on the study of the center deviation of the wake turbulence in the yaw state of the upstream wind turbine. According to the existing theoretical basis, the simplification formula of the wake displacement is deduced, and the formula is programmed in MATLAB. The relationship between the parameters of the wake displacement is obtained, and the relationship between the parameters is analyzed. Then the model of wind turbine was established in Bladed software and the two sets of wind turbine with 7 times wind wheel diameter were taken by the center deviation of the wake center. Under certain wind direction, the wind turbine was active yaw control. After a certain angle, the power characteristics of the two units were analyzed and summarized.

Corneal powers measured with a rotating Scheimpflug camera

Background/aimKeratometry measures the anterior corneal curvature only. Corneal power is calculated by multiplication with the keratometric refractive index, which takes into account the average negative posterior corneal power. The aim...

Modified Novel Line Stability Factor Index with Reactive Power Tracing for Identification of Vulnerable Buses in Power System

Many power tracing techniques have been developed but are limited to the application of transmission service pricing in a deregulated environment. To expand the knowledge of power tracing theory and its application, this paper adopts the power tracing theory into voltage stability improvement. This paper proposes a modified novel line stability factor index with load tracing capability known as LQP_LT for the purpose of finding the appropriate locations in a power system network for any preventive and corrective actions. Unlike the commonly applied real power tracing, this method presents the reactive power tracing utilizing the proportional sharing method (PSM) with all the line reactive losses being taken into consideration in the network study with the system size remain the same. IEEE 5 bus system is used to demonstrate the LQP_LT concept and all the results obtained are compared with modified Fast Voltage Stability Index with load tracing ability (FVSI_LT). The results obtained found to be efficient in determining the reactive power contributed by a certain load bus in a transmission line which ultimately responsible to cause a stressed line and overall voltage instability in a system.

무효전력 흐름 추적을 이용한 무효전력 취약지역 판단

Abstract - The paper analyzes reactive power flow characteristic in power system by reactive power tracing. In addition, virtual buses are inserted in the algorithm to consider losses of transmission lines, and shunt capacitor treated as a reactive power generator. The results of simulation are analyzed by two points of view. The one is load’s point of view and another is generator’s point of view. Classic purpose of the reactive power tracing consists in the reactive power pricing. However, it is significantly used to select vulnerable area about line outage in this paper. To find the vulnerable area, reactive power tracing variations between pre-contingency and post-contingency are calculated at all load buses. In heavily load area, buses which has highest variation become the most vulnerable bus. This method is applied to the IEEE 39-bus system. It is compared with voltage variation result and VQ-margin to verify its effect.Key Words : Reactive power tracing, Vulnerable area, Proportional sharing rule, Power flow, Virtual bus†Corresponding Author : Department of Electrical Engineering, Korea University, KoreaE-mail : leeb@korea.ac.kr* Department of Electrical Engineering, Korea University, KoreaReceived : January 9, 2015; Accepted : June 16, 2015

Paying attention to optimization and combination of the preoperative biomeasurement with intraocular lens power calculation in cataractous eyes

As the development of surgery related technology and clinical application of premium intraocular lens (IOL), cataract surgery has been in the era of refractive surgery. To restore the refractive system by surgery has been focused on and challenges have been brought up in preoperative measurement and accurate IOL power calculation methods. It is necessary to know developments of the related measurement technologies and the possible error resources to decrease refractive errors. Different means of measuring axial length, cornea curvature and anterior chamber depth were related here, co-operated with varied IOL power calculation methods, such as standard power, traditional formulas and real ray tracing method. Researchers should pay close attention to the preoperative measurement and IOL power calculation methods in cataract patients, the combination of accurate measurement with different calculation methods can help to acquire an increasingly satisfactory visual result. Key words: Cataract/surgery; Biometrical measurement; Axial length; Corneal curvature; Anterior chamber depth; Intraocular lens

LOSS ALLOCATION OF TRANSMISSION LINE AND MINIMIZATION OF LOSS FOR 5 BUS,14 BUS &30 BUS SYSTEMS

The paper focuses on the issue of transmission loss allocation and transmission loss minimization by incorporating UPFC injection model using load flow analysis. To investigate the effect of the UPFC on the steady state condition of the system and load flow, different models can be used. These models are usually based on modification of traditional load flow methods. In this project, a mathematical model for UPFC referred as UPFC injection model is used. Since accurate power tracing is very difficult, allocation of losses for a particular transaction (in power business it is buying and selling system) may not be effectively realized. However loss allocation is an important aspect in determining the cost of transmission. Thus a methodology to find the losses accurately is vital. It is imperative to make sure that all users of the transmission network are charged proportionate to their usage and this aspect is all the more important because of the common infrastructure they use. The Z-bus loss allocation method is used to achieve the required objective. This method will promote more efficient network operations when implemented in deregulated electric industries. The Unified Power Flow Controller (UPFC) injection model is incorporated in Load Flow Model by the method of Newton Raphson Algorithm to study its effects for power flow control and losses minimization in the power system. In this project optimal placement of UPFC is conducted based on active power loss Sensitivity factors. Based on these sensitivity factors the UPFC is optimally placed in the required transmission line to investigate the impact of UPFC in the system. The changes in the system are studied to see the impact of the UPFC. The impact of UPFC are analyzed by using 5-Bus, IEEE.

Thermal and Optical Performance of a Light-Emitting-Diode Metal Package With an Integrated Reflector and Heat Spreader Structure

We develop a light-emitting diode (LED) metal package consisting of a reflector integrated with a heat spreader as one body. The structure functions obtained from the thermal transient measurement reveals that the integrated structure of the metal package leads to improved thermal performance. We make significant efforts to clarify the interaction between the extracted light from the LED chip and the inside surface of the metal package. The radiant flux from the LED chip is calculated from the definition of thermal resistance and is implemented as an input parameter to predict the optical power and ray tracing. The simulated optical output power in the far-field mode is 145.3 mW, which is in good agreement with the value measured by an integrating sphere. It is shown that a large portion of the emitted light (37.12 mW) is lost by the interaction with the package surface before it reaches the far-field receiver. It is demonstrated that the angle of the first reflector cup is one of the critical design parameters in the metal package structure that we investigate. When the first reflector angle is optimized from 80° to 55° (with the second reflector angle of 50°), the optical power increases from its original value of 145.3-170.15 mW with an improved optical extraction efficiency from 75.63% to 88.57%. The ray tracing and illuminance raster charts also confirm that the improved optical performance of the metal package mainly stems from the optimization of the reflector angles.

Study on Maximum Power Tracing Controller Based on Self-Adaptive Strategy for Variable Speed Constant Frequency Brushless Doubly-Fed Generator

The key technology of variablespeed constantfrequency (VSCF) brushless doubly-fed generator (BDFG) was getting the maximum power under the variable wind speed by adjusting the rotor speed of the induction generator according. Wind turbine systems had many uncertain factors with strong nonlinear multivariable with and disturbances. Based on the prototype of wind electricity conversion system (WECS), a new maximum power point tracking control which is realized by self-adaptive controller strategy for variable speed constant frequency wind generation system has been developed in this paper. A experiment platform of a 8kW laboratory variable speed constant frequency wind generation system controlled by TMS320LF2812 and TMS320VC33 was developed. Experimental results show that the system can operate at the expected points in the wide range of wind velocities and realize the control of maximum power point tracking very well.

Study on Control System for CS Mode of PHEV Based on State Space Description Method

Electric vehicles represent the direction for development of future vehicles. The control system for battery component is one of its key technologies and its performance has a vital impaction on the whole vehicle. In this paper, the state space description method is adopted to model the control system for battery component of PHEV. Taking equivalent fuel consumption and power tracing accumulated error as optimize object, the control system is testified and evaluated based on both ECE and NewYork drive cycles. The results indicate that the control system has good driving performance, good fuel economy and charge sustainability, thus satisfying the requirement of electric vehicle application well.

Utilizing Stability Index Tracing for Precise Load Buses Identification in Load Shedding Problem

This paper proposes a new approach for suitable load buses identification via stability index tracing in performing corrective load shedding. The proposed identification technique is called the Fast Voltage Stability Index Load Tracing (FVSI-LT). By implementing a power tracing algorithm, a group of major contributors on the stress experienced by a power system is able to be precisely identified by a system operator (SO) based on the traced values of FVSI. To be precise, the traced FVSI via FVSI-LT can be used to form a ranking list indicating the priority of buses committed for shedding purpose. After designing a Fuzzy Inference System (FIS) for deciding the allowable load powers to be shed and performing experiment on IEEE 57-Bus reliability test system (RTS), it is revealed that the ranking list provided by FVSI-LT results to the most consistent improvement in terms of voltage stability and losses minimization.

Preference Comparison of AI Power Tracing Techniques for Deregulated Power Markets

This paper compares the two preference artificial intelligent (AI) techniques, namely, artificial neural network (ANN) and genetic algorithm optimized least square support vector machine (GA-LSSVM) approach, to allocate the real power output of individual generators to system loads. Based on solved load flow results, it first uses modified nodal equation method (MNE) to determine real power contribution from each generator to loads. Then the results of MNE method and load flow information are utilized to estimate the power transfer using AI techniques. The 25-bus equivalent system of south Malaysia is utilized as a test system to illustrate the effectiveness of the AI techniques compared to those of the MNE method. The AI methods provide the results in a faster and convenient manner with very good accuracy.

The Research of a Derivation Calculation Method for the Maximum Power Point in Grid-Connect Photovoltaic System

A derivation calculation methods for the maximum power point tracking is proposed in this paper. This method is the direct calculation method for the maximum power point tracking, through the calculation of the derivative value of the power to voltage, adjust the change values of occupies emptiescompared, which is used to deduce the voltage and current value, judge whether the derivative of the power to the voltage is zero, if it is ture, the maximum power point is got. Hardware is used the method to regulate the duty ratio of PWM in DC/DC boost circuit ,though once sampling, it can calculate the value of voltage and the duty ratio at maximum power point. The prototype experiments using DSP2812 chip verify that the inverter can better realize the most power tracing, high accuracy, and the system has the high stability.

Grid-Connected Solar Microinverter Study and Design Using a dsPIC Digital Signal Controller

An interleaved flyback converter using a dsPIC digital signal controller is researched and designed, regarding to photovoltaic (PV) grid-connected micro inverter’s characteristics, the system structure and control principles is studied, and a new method combining Constant Voltage (CV) and Perturb and Observe(P&O) to track the Maximum Power Point (MPP) is applied. The prototype experiments verify that the inverter can better realize the most power tracing and island detection function, at the same time reduce the current output ripple, lower its THD.

Reactive power cost allocation by power tracing based method

A reactive power cost allocation method based on power tracing principle is presented here. A new solution is proposed to solve the problem of bidirectional reactive power flow to enable the application of power tracing method to reactive power flow. Reactive power supplied by the line charging capacitance is considered to be a separate reactive source and accordingly reactive load and loss are also allocated to it. Total system reactive demand including load and loss is first allocated to all the sources, viz. generators, synchronous condensers, capacitors and line charging capacitance and finally these sources are offered the revenue for supplying this power according to the pricing structure adopted. In the present work a quadratic reactive cost function is adopted for the generators and all other sources are considered to have a fixed cost per unit MVar supplied, which is calculated from the installation cost of the respective reactive power source. The work is demonstrated on IEEE standard test systems and a practical Indian grid system.