MW Losses Research Articles

Micro Genetic Algorithm to Solve Economic Dispatch in IEEE 30 Bus Transmission System

To produce electric power in a power system, it is necessary to find a way to keep the cost of generator fuel consumption or operating costs of the entire system to a minimum by determining the combined output power of each generating unit under the constraints of the system load demands and the limits of the generation capacity of each generating unit. . This method is known as economic generation. The researcher usually using conventional method such us Lagrange and more modern methods, Artificial Intelligence, such us Particle Swarm Optimization (PSO), Genetic Algorithm (GA) to solve economic dispatch problem. The newest technology in Artificial Intelligence had invented a new method to solve economic dispatch, it’s named micro-Genetic Algorithm (µ-GA). In this paper, µ-GA is applied to solve economic dispatch in IEEE 30 Bus Transmission System. Then the result will be compared by Lagrange and conventional GA. Thus the simulation show that µ-GA has better result than Lagrange and conventional GA. In IEEE 30 Bus System, μ-GA method results generation cost of 568.80 $/h with the generated power of 189.45 MW and system losses of 0.25 MW in 30th generation. It is 2.64% cheaper than the GA method and 1.15% cheaper than the Lagrange method. Finally, it can be said that in the case of economic dispatch in IEEE 30 Bus Transmission System, the μ-GA method is the best method compared to the Lagrange and GA methods.

Optimal Planning and Operation of Multi-Frequency HVac Transmission Systems

Low-frequency high-voltage alternating-current (LF-HVac) transmission scheme has been recently proposed as an alternative solution to conventional 50/60-Hz HVac and high-voltage direct-current (HVdc) schemes for bulk power transfer. This paper proposes an optimal planning and operation for loss minimization in a multi-frequency HVac transmission system. In such a system, conventional HVac and LF-HVac grids are interconnected using back-to-back (BTB) converters. The dependence of system MW losses on converter dispatch as well as the operating voltage and frequency in the LF-HVac is discussed and compared with that of HVdc transmission. Based on the results of the loss analysis, multi-objective optimization formulations for both planning and operation stages are proposed. The planning phase decides a suitable voltage level for the LF-HVac grid, while the operation phase determines the optimal operating frequency and power dispatch of BTB converters, generators, and shunt capacitors. A solution approach that effectively handles the variations of transmission line parameters with the rated voltage and operating frequency in the LF-HVac grid is proposed. The proposed solutions of the planning and operation stages are evaluated using a multi-frequency HVac system. The results show a significant loss reduction and improved voltage regulation during a 24-hour simulation.

Evaluation and Improvement of Total Transfer Capability in an Interconnected Power System

With deregulation, the total transfer capability (TTC) calculation, which is the basis for evaluating available transfer capability (ATC), has become very significant. Total transfer capability (TTC) is an important index in power markets with large volume of interarea power exchanges and wheeling transactions taking place on hourly basis. Its computation helps to achieve a viable technical and commercial transmission operation. The aim of the paper is to evaluate TTC in the interconnections and also to improve it using reactive optimization technique and unified power flow controller (UPFC) device. TTC computation is carried out considering normal and contingency conditions such as single line, tie line and generator outages. Base and optimized results are presented, and the results show how reactive optimization and UPFC help to improve the system conditions and tie flows. Repeated power flow method is used for transfer capability computation due to its ease of implementation. A case study is carried out on a 72-bus equivalent system, which is a real-life system, a part of Indian Southern grid. The developed procedure is successfully applied to the three-area 72-bus system. Parameters like voltage magnitude, L-index, minimum singular value and MW losses are computed to analyze the system performance.

An Expert System Approach for Multi-Year Short-Term Transmission System Expansion Planning: An Indian Experience

This paper proposes an expert system approach to short-term expansion planning (STEP). The rules which drive STEP can be classified into MW, MVAR, and ampacity management rules. MW and ampacity management rules are for alleviating transmission line congestion. Reactive power management is required for voltage control at load busses, conformity to the capacity curve of the generators, and containing the MW losses within acceptable limits. Embedding reactive power management in STEP is a challenging task since ac load flow may not converge in absence of proper reactive power planning and load modeling. Therefore, we also propose enhancements to the fast decoupled load flow algorithm for on-the-fly reactive power management. The enhanced algorithm not only can detect divergent load flow scenarios but also self-correct it by restarting the whole process with greater degree of freedom in reactive power controls. The proposed approach leads to development of an automated tool for STEP which has the capability to work, even with incomplete information. A simple method for evaluating location and requirement of shunt reactor is also proposed. By analysis and comparative evaluation, we show that the proposed system can arrive at a solution which is close to optimal. Results on the Western Regional Grid of India with an approximate load of 28 000 MW and 1200 nodes are presented to demonstrate effectiveness of the proposed approach.

Synergism of MW and Mvar Losses for Contingency Ranking Using Fuzzy Approach

Security assessment of a power system is very important function to detect any violation in the system and to ensure secure operation of the system in deregulated environment. Contingency ranking is the process of indexing the possible contingencies of system on the basis of their severity. The contingencies of higher ranking are further analyzed for detailed analysis. The contingencies based on the real power flow and the voltage deviations should be dealt simultaneously for better ranking. The paper presents fuzzy approach to combine ranking based on MW and Mvar losses and a new rank list is prepared. The proposed approach is tested on IEEE-30 bus test system.

A genetic based method for optimal reactive power compensation of transmission network

Reactive power compensation is known as an effective tool to overcome the violations of voltage limits in electric power systems. It is also deployed to be an efficient method to minimise transmission losses. In order to maximize the effectiveness of reactive power compensation, VAr sources of proper sizes should be placed at some network buses. In this paper, a new VAr expansion tool has been developed to improve the voltage profile and reduce MW losses in a bulk power network. Keeping the minimum expansion cost and minimum switching of capacitor banks during change of load level of the system are emphasized in the proposed method. This method is based on application of genetic algorithm in conjunction with linear programming. Selection of candidate buses for VAr compensation is performed with a modified weak bus oriented method. Genetic algorithm is effectively employed in this algorithm both for selecting the candidate buses for VAr compensation and for preliminary suggestion of optimal solution. The developed method is then applied to the transmission network of Bakhtar Regional Electric Company (BREC) which supplies three provinces of Iran. The simulation results of this case study are also presented in this paper.

The mechanical properties and in vitro biodegradation and biocompatibility of UV-treated poly(3-hydroxybutyrate- co-3-hydroxyhexanoate)

Strong mechanical properties and controllable biodegradability, together with biocompatibility, are the important requirement for the development of medical implant materials. In this study, an ultraviolet (UV) radiation method was developed to achieve controlled degradation for bacterial biopolyester poly (3-hydroxybutyrate- co-3-hydroxyhexanoate) (PHBHHx) which has a low biodegradation rate that limits its application for many implant applications required quick degradation. When UV radiation was applied directly to PHBHHx powder, significant molecular weight (Mw) losses were observed with the powder, Mw reduction depended on the UV radiation time. At the same time, a broad PHBHHx Mw distribution was the result of inhomogeneous radiation. Interestingly, this inhomogeneous radiation helped maintain the mechanical properties of films made of the UV-radiated powder. In comparison, the PHBHHx films subjected to direct UV radiation became very brittle although their degradation was faster than that of the PHBHHx powders subjected to direct UV radiation. After 15 weeks of degradation in simulated body fluid (SBF), films prepared from 8 and 16 h UV-treated PHBHHx powders maintained 92% and 87% of their original weights, respectively, while the untreated PHBHHx films lost only 1% of its weight. Significant increases in growth of fibroblast L929 were observed on films prepared from UV-radiated powders. This improved biocompatibility could be attributed to increasing hydrophilic functional groups generated by increasing polar groups C–O and C O. In general, UV-treated PHBHHx powder had a broad Mw distribution, which contributed to fast degradation due to dissolution of low Mw polymer fragments, and strong mechanical property due to high Mw polymer chains. Combined with its improved biocompatibility, PHBHHx is one more step close to become a biomedical implant material.

Calculation of Energy Transaction Allocation Factors

The ability to allocate the MW loading on transmission lines and groups of lines is the basis of NERC's "flow based" transmission allocation system. In such a system, the MW flows must be allocated to each line or group of lines in proportion to the MW's being transmitted by each transaction. This is accomplished through the use of the linear power transfer distribution factors. Unfortunately, no linear allocation models exist for other transmission phenomena such as MW losses, MVA flows, etc. This paper presents a methodology to calculate energy transaction allocation factors (ETA factors, or η factors), using the well-known process of integration of a first derivative function. The factors give a highly accurate allocation of any nonlinear transmission system quantity to the active transactions placed on a transmission system.

Calculation of energy transaction allocation factors

The ability to allocate the MW loading on transmission lines and groups of lines is the basis of NERCs flow based transmission allocation system. In such a system, the MW flows must be allocated to each line or group of lines in proportion to the MWs being transmitted by each transaction. This is accomplished through the use of the linear power transfer distribution factors. Unfortunately, no linear allocation models exist for other transmission phenomena such as MW losses, MVA flows, etc. This paper presents a methodology to calculate energy transaction allocation factors (ETA Factors, or /spl eta/ factors), using the well-known process of integration of a first derivative function. The factors give a highly accurate allocation of any nonlinear transmission system quantity to the active transactions placed on a transmission system.

Microwave properties of ferroelectric film planar varactors

A set of microwave (1–30 GHz) measuring resonators and procedure of measurements for the investigation of microwave properties of ferroelectric film planar varactors were elaborated. The fabricated resonators enabled MW losses and tunability of ferroelectric varactors under dc bias voltage to be determined. The SrTiO3 and (Ba,Sr)TiO3 film planar varactors were tested on microwaves at room temperature. A ratio of varactor capacitance at zero bias to bias conditions, K, was found as 2 for the SrTiO3 varactors and K=2.2 for the (Ba,Sr)TiO3 varactors. The microwave losses in the ferroelectric varactors were measured at frequencies of R-, X-, K-, and Ka-bands. Temperature stability of the varactor capacitance was estimated.

Calculations of tuning effect and MW losses in HTS microstrip resonators with ferrite thin film components

The formulas for calculating the resonance frequency and MW losses in HTS microstrip resonators containing perpendicularly and tangentially magnetized ferrite films were obtained using perturbation methods. The conditions for obtaining a maximum tuning effect were analyzed.

Development of three-phase Newton optimal power flow for studying imbalance/security in transmission systems

Abstract This paper presents a three-phase optimal power flow (TOPF) method based on Newton's method for the off-line balance/imbalance and security analysis of large scale transmission systems. The TOPF deals with minimization of the system three-phase MW losses while satisfying three-phase power flow equations, three-phase security constraints and voltage imbalance factor (VIF) constraints, etc. The three-phase models considering the coupling effect among the phases are used in this method. All models are based on the phase frame representation. The sparse matrix technique is used and the pivoting programming techniques for reducing the computer memory required is addressed. Several functions are implemented in the proposed software for a more realistic simulation; these functions include the reduction of the controller set, treatment of infeasibility, implementation of static VAR compensators (SVCs), selection of load models, and initialization, etc. An algorithm covering the main and trial iterations is used for identifying an accurate set of active inequality constraints. The 265-bus Taipower system is used to serve as an example for illustrating the performance of the proposed method in studying the imbalance problem caused by the upcoming high-speed electric railway load in Taiwan.

Three-phase active power line conditioner planning

The active power line conditioner (APLC) is considered to be a very efficient type of active power filter that compensates the voltage waveform distortion caused by nonlinear loads in power systems. A new approach is based on a previously presented two-level algorithm, the three-phase optimal harmonic power flow (TOHPF), to investigate the determination of locations and sizes of three-phase (3phis) APLCs. The objective is to minimise the new APLC investment cost, the 3phis voltage distortion, and the system 3phis MW losses while satisfying the 3phis power flow equations, 3phis harmonic power flow equations, 3phis security constraints, and the harmonic standard. The master level of TOHPF determines the compensator/tap settings and the new APLC locations/sizes; the slave level of TOHPF includes subproblems which involve cases of fundamental and harmonic frequencies separately. Test results for an 18-bus distribution system show the applicability of the proposed method.

Optimal harmonic power flow

A new optimal harmonic power flow (OHPF) method is proposed in this paper. This new OHPF is designed to minimize the MW losses and the total harmonic voltage distortion while satisfying the power flow equations, harmonic power flow equations, security constraints and harmonic standard, etc. A two-level algorithm is used to solve the problem: the master level determines the settings of compensators and taps; and the slave level includes subproblems which involve cases of fundamental and harmonic frequencies separately. The test results for two power systems show the applicability of the proposed method.

Short-term scheduling of reactive power controllers

A two-level approach is presented to solve the problem of 'optimal' short-term (one day) scheduling of reactive power controllers in this paper. The entire problem is decomposed into two levels: the master and the slave levels. The master level deals with minimization of the depreciation cost of compensators and EHV transformer taps in order to reduce the control action for compensators and EHV transformer taps while satisfying operating constraints. The slave level treats minimization of capitalized MW losses while satisfying system security constraints. The slave level also treats OLTCs and determines scheduling of the generator voltages. These two levels interact through linear constraints in the iteration process. A practical 265-bus system, namely Taiwan Power System, are used to serve as a sample to show the applicability of the presented approach.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimal short‐term scheduling of shunt compensators via a decomposition algorithm

Abstract The short term (one day) scheduling of VAr controllers involves the setting of shunt compensators, EHV taps and generator voltages. A decomposition approach is presented to solve the problem of optimal short‐term scheduling of shunt compensators in this paper. The entire problem is decomposed into two levels: the master and the slave levels. The master level deals with minimization of the depreciation cost of compensators in order to reduce the control actions for compensators while satisfying operating constraints. The slave level treats minimization of capitalized MW losses while satisfying system security constraints by adjusting generator voltages and taps. These two levels interact through linear constraints in the iteration process. The IEEE 30‐bus and a practical 265‐bus systems, namely Taiwan Power System, are used to serve as samples to show the applicability of the presented approach.

Investigation of factors causing slow convergence in Newton optimal power flow

Factors causing slow convergence in the Newton optimal power flow (OPF) approach are presented in this paper. The solution speed of the approach is evaluated by the numbers of the main and trial iterations. The OPF discussed in this paper deals with minimization of the system MW losses while satisfying system security constraints by adjusting reactive power controllers. The factors causing slow convergence include (a) insufficient sources of reactive power, (b) a solution space with a flat bottom, and (c) the load model. This paper helps to clarify the ambiguous phenomena of slow convergence. The main phenomena, explanations and termination criterion/enhanced treatment are presented for each factor. The IEEE 30- and 118-bus systems and a practical 217-bus system, namely, the Taipower system, are used to serve as samples in this paper.

Voltage stability indicator for identification of the weakest bus/area in power systems

Application of Newton optimal power flow (OPF) to identify the weakest bus/area, which is most likely to cause voltage collapse, is presented in this paper. The S-V curve (complex power to voltage) is examined via Newton OPF. Marginal costs (Lagrange multipliers) regarding power flow equations, VAr generations, voltages and taps, etc., to the system MW losses are obtained from Newton OPF. The weakest bus/area in the system is identified by an indicator achieved with these marginal costs via the Kuhn-Tucker theorem. This indicator helps users know which bus/area is most likely to cause voltage collapse. The IEEE 30-bus and a practical 251-bus systems are used to show the capability and feasibility of the proposed approach.

Enhanced Newton optimal power flow approach: experiences in taiwan power system

An enhanced Newton optimal power flow (OPF) approach is presented. The OPF deals with minimisation of the system MW losses while satisfying system security constraints by adjusting reactive power controllers. Programming techniques and treatments of inequality constraints are enhanced. The presented programming techniques reduce the computer memories required and improve the numerical stability while solving the algebraic equations of necessary conditions for optimality. The enhanced treatment for the inequality constraints enables Newton OPF to identify correct binding inequality constraints efficiently. A practical 217-bus system, namely Taipower system, is used to demonstrate the capability of the enhanced Newton OPF. >

Multi-year multi-case optimal VAR planning

An integrated methodology for long-term VAr planning is presented that results in determining the timing (year), the location, and the amount of VAr compensation. The system security and investment and operating economics are taken into account. The proposed methodology is an integration of the Newton-OPF with the generalized Benders decomposition (GBD). The total problem is decomposed into two levels: master and slave. The master level deals with the investment decision of installing discretized new VAr devices. The slave level deals with operating the existing controllers, in conjunction with the new devices solved in the master level, to maintain system feasibility and to reduce MW losses. The overall solution methodology contains numerous extensions to the basic theory. Tests performed on actual Taiwan power system data have been encouraging. Sample results are presented. >