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Industrial estates in Thailand, which are usually connected to distribution systems, allow power producers to directly negotiate with their own customers. Therefore, distribution utilities have to calculate wheeling charges with fairness and transparency. This paper proposes a concept of wheeling charge calculation based on “power flow based MW-Mile method” with the consideration of differentiation of line flow magnitude before and after the power transaction. The results show that the proposed concept computes the different wheeling charge against existing power flow based MW-Mile method and can reflect an increase or decrease of line flow due to power transaction.

Transmission CA (TCA), a powerful function in EMS, is to help system operators maintain the security of a TPS. It simulates the post-contingency power flow of the TPS and activates alarms if operational limits of some components (e.g., bus voltage magnitude limits or line flow limits) are violated in a contingency.

This paper presents a FACTS operation scheme to enhance the power system security. Three main generic types of FACTS devices are introduced. Line overloads are solved by controlling active power of series compensators and low voltages are solved by controlling reactive power of shunt compensators, respectively. Especially, the combined series-shunt compensators such as UPFC are applied to solve both line congestions and low voltages simultaneously. Two kinds of indices that indicate the security level related to line flow and bus voltage is utilized in this paper. They are iteratively minimized to determine operating points of the devices for security enhancement. The sensitivity vectors of the indices are derived to determine the direction of minimum. The proposed algorithm is verified on the IEEE 14-bus system with FACTS devices in a normal condition and in a line-faulted contingency.

This paper presents a load shedding algorithm for alleviating line overloads employing Teaching learning based optimization (TLBO). The buses are selected for load shed based on the sensitivity of severity index with respect to load shed. Load shed is based on the next interval predicted load which could cause emergency situation from thermal limit consideration. Line flow constraints have not only considered for next predicted interval but in present base case loading conditions also. Optimum load shed at the selected buses have been obtained for 30-bus, 39-bus standard test systems. Further another technique modified version of bare bones particle swarm optimization known as (BBExp) has been used to validate the algorithm for load shedding.

This paper describes a method for alleviation of line over load in a line by regulation power flow in another line having Series Power Flow Controller (SPFC). For this purpose, the sensitivity relations between the line flow of the line with SPFC and the over loaded line are determined. These sensitivity relations are used to determine the required amount of change in power flow at the line with SPFC to reduced power flow of the over loaded line. IEEE 30 system is used to verify the applicability of the proposed method.

This paper defines flow control algorithms for loop flow cancellation based on the allocation and tracing of bilateral transactions and loop flows. In Part I of this paper, we have shown that the main difference between transportation and electrical networks is caused by the existence of loop flows. We have introduced a distributed framework for the modeling and tracing of bilateral transactions and the corresponding loop flows. Its zooming-out capability provides a valuable mechanism for representing external (inter-area) loop flows based on simplified topologies of individual areas. The tracing information accurately allocates bilateral transactions with associated contract paths to line flows and loop flows. Furthermore, this information can be used for determining the set points of control equipment so that loop flows are minimized. In this framework, phase angle regulators (PARs), commonly used for line flow control, are represented through their effects on loop flows. We define sufficient conditions for achieving complete loop flow cancellation. A new distributed algorithm for determining PAR set points in a coordinated way without revealing operating conditions of individual areas is introduced in this part. Finally, complete loop flow cancellation and the distributed algorithm for finding PAR set points are demonstrated in the Reliability Test System (RTS) 96-bus system with wheeling loop flows.

This paper investigates voltage stability of the power system during steady state and transient conditions. The voltage stability enhancement is achieved by utilizing FACTS devices at the best location of the system. The weakest bus in the system is the best location to implement shunt compensation device. In this paper, the weakest buses are identified via a fuzzy technique that utilizes two critical indices: Line Flow Index (LFI) and Voltage Profile Index (VPI) during normal and fault conditions. These indices are used to evaluate Criticality Index (CI) using Fuzzy rules, and thus, the system buses are ranked. Remedial actions are discussed to enhance the power system voltage stability by using FACTS devices (SVC and STATCOM) at the most vulnerable system buses. The results of this study show that the (STATCOM) performance is preferable to that of the (SVC) during fault conditions.

The goal of this work is to calculate the total loss in the system and minimize this loss by implementation of distributed generation (DG) technology. In this paper, load flow analysis method is followed to calculate the loss in the system in conjunction with the line flows. A simple 5 bus system with the main bus of the substation as the slack bus, three Plant generators at the generator bus and three load buses are taken for analysis. For loss minimization two distributed generators at two load buses are connected. One generator is a synchronous type model and the other is asynchronous type model. We searched for the most economical penetration level and the ratings of the distributed generators are decided by the magnitude of penetration power at each load bus. Using software, power system simulation for electrical (PSSE), the system with and without DG technology is modeled and the output from the PSSE is observed.

This paper presents a new decoupling strategy by strengthening P – δ and Q – V relationships based on line flow and voltage magnitude measurements in order to obtain a reliable convergence and higher computational speed. The real and reactive set of measurements are combined using simple multiplying factors such that the modified set is decoupled into two set of equations without making any assumption on r / x ratios. The resulting Jacobian matrices that contain only line parameters are sparse and constant. The technique is applied on three test systems and is solved by WLS and WLAV methods to illustrate its superior performance.

This paper presents a new method for calculating the individual generators’ shares in line flows, line losses and loads. The method is described and illustrated on active power flows, but it can be applied in the same way to reactive power flows. Starting from a power flow solution, the line flow matrix is formed. This matrix is used for identifying node types, tracing the power flow from generators downstream to loads, and to determine generators’ participation factors to lines and loads. Neither exhaustive search nor matrix inversion is required. Hence, the method is claimed to be the least computationally demanding amongst all of the similar methods.

This paper proposes two fast calculation methods of ATC. These two methods evaluate ATC with thermal constraints(Thermal ATC) and ATC with voltage stability constraints(Voltage ATC) respectively. The ATC with thermal constraints was based on the linear incremental power flow to account for the line flow thermal loading effects when the n-1 security constraints were included. The ATC with voltage stability constraints used two-bus equivalents of the system to find the maximum load at a load bus before reaching the voltage stability problem. The methods were tested on the IEEE 30bus systems and the results obtained were compared with those found by some other methods.

Load flow analysis is essential to know the detailed description of a complex power network. Load flow solutions provide the basic computational techniques in order to determine the voltages at various buses and the power flowing through the elements of the system. In this chapter, some basics of load flow analysis have been discussed along with N–R method and fast decoupled method of load flow analysis. These techniques are applied to the online/offline studies of multi-bus power networks using developed soft computing techniques.

Analysis of radial distribution systems with embedded series Flexible AC Transmission System (FACTS) devices is facilitated by a formulation of power flow equations with bus voltage magnitudes and line flows as independent variables. Since control variables such as the line and bus reactive powers figure directly in the formulation, handling the control action of FACTS devices in distribution systems is direct and easily implemented. Using the Breadth-First-Search (BFS), the bus incidence matrix of a radial distribution system is first rendered strictly upper diagonal, leading to reduced computational effort. All the common FACTS device models under steady-state conditions are easily incorporated in the new framework by a simple process of "variable swapping." Using IEEE standard systems, the line flow-based (LFB) formulation is shown to provide easy implementation with multiple series and shunt FACTS devices in the system and enable direct evaluation of the FACTS device ratings.

The practical power system operation criterion along with short term and long term expansion planning are most important parameter to be factored into the decision of the optimal location of FACTS controllers for achieving the maximum benefit of FACTS controllers. This paper proposes the optimal location of TCSC controllers in the power transmission system to eliminate or alleviate line overloads in the system based on practical power system operation criterion. The concept of line flow overload sensitivity index (LFOSI) of the system lines with reference to real time generation mix strategies based on conventional and nonconventional generation, seasonal load pattern, peak and off-peak conditions, adhering grid discipline, permitting power transactions, future projected demand, network modification and capacity addition have been developed. The proposed concept of FACTS placement using LFOSI based on practical operation criterion and expansion planning approach has been extensively analyzed and implementation methodology is also developed to decide the optimal location of FACTS controllers so as to consider practical operation criterion and expansion planning systematically.

Fast, accurate algorithms to compute network capabilities are indispensable for transfer-based electricity markets. Available Transfer Capability (ATC) is a measure of the remaining power transfer capability of the transmission network for further transactions. Transmission System Operators (TSOs) are encouraged to use the existing facilities more efficiently. One of the limitations of reactive ATC is the error produced by neglecting the effect of reactive power flows in line loading. This paper presents the determination of shunt reactive power compensation with Flexible AC Transmission System (FACTS) devices, the Static Synchronous Series Compensator (SSSC) to improve the transfer capability of a power system incorporating the Linear and Reactive power flows in ATC calculations. By redistributing the power flow, the ATC is improved. Studies on a sample 5-bus power system model are presented to illustrate the effect of shunt compensation along with line flow control.

A new methodology for a possible fast evaluation of a power flow is presented. The proposed method involves a transient stability constrained line-flow-based (LFB) fast contingency screening. This ‘direct’ method incorporates transient energy function (TEF) to carry out the evaluation of a power system. The proposed LFB method was tested on the WECC 9-bus, three machine, the IEEE 14-bus, five machine, and the IEEE 39-bus, ten machine systems. Results of the proposed LFB were compared with those obtained from the conventional Newton-Raphson (N-R) method. It was observed that the stable re-dispatch could be obtained by the LFB method within half the computation time as compared to the time required for the N-R method. Since the LFB method was based upon identification of the stable equilibrium points of the TEF, the proposed method appears to be inherently capable of delivering a stable power dispatch. In addition, a new index called critical energy performance index (CEPI) has been introduced to indicate the level of stability and to assist in the decisions related to the re-dispatch.

The application of Differential Evolution (DE) to compute the Total Transfer Capability (TTC) in deregulated market is proposed in this paper. The objective is to maximize a specific point-to-point power transaction without violating system constraints using DE. This algorithm is based on full ac optimal power flow solution to account for the effects of active and reactive power flow, voltage limits, and line flow limits. The real power output of generators in source area and the real power of the loads in the sink area were adjusted to obtain the maximum transfer capability. In order to calculate TTC more accurately, Transmission Reliability Margin is incorporated in the calculation of TTC by considering single and multiline outages and also a three phase to ground fault near a bus and clearing it by isolating the faulty line after certain time interval. The performance of the proposed method is tested on the modified IEEE-30 bus system and results are compared with that of Particle Swarm Optimization method (PSO). Further, the results are compared with other published results using CPF and EP. It is found that DE provides more reliable results than other methods. Keywords: Total transfer capability, available transfer capability, transmission reliability margin, differential evolution, particle swarm optimization.

This paper presents an on-line economic power dispatch method by calculating the B -coefficients from the network sensitivity factors. The sensitivity factors are established from a new line flow solution based on the DC load flow model. The derivation of a new loss coefficient formula is performed and the solution algorithm is described. Many assumptions in the use of the conventional loss coefficients are eliminated. Example systems are tested to demonstrate the performance of the proposed method. Compared with the exact solution of the optimal load flow method and the computational rapidity of the base-case database method, the proposed method has good accuracy and a fast execution time. This method is very suitable for on-line application in the economic operation of power systems.

Summary form only given. Research effort has been given to locate the optimal locations of thyristor-controlled series capacitor (TCSC) and their initial compensation levels using mixed-integer programming (MIP). As a useful technique for combinatorial optimisation over integer and continuous variables, the MIP approach can provide robust performance as well as high computational efficiency while solving complex optimal problems. Previous work using MIP employed DC load flow model ignoring reactive power balance, power loss and transformer tap ratios. In this paper, a new planning method is developed based on recently reported line flow equations and basic linearisation of binary-continuous products. The objectives of the planning strategy are to improve system loadability, voltage profile in the network, as well as to minimise the investment cost by choosing proper locations and settings of devices. Simulation results are presented and discussed for IEEE 9-, 57-, 118-, and 300-bus systems.

The most commonly used WLS state estimator in power industry is non-linear and formulated by using conventional measurements such as line flow and injection measurements. The computational burden becomes a concern for the existing WLS state estimation when integrating PMU measurements. Distributed state estimators, which can solve this problem of integrating, have been proposed for this reason. However, the discrepancy between distributed state estimator and the integrated state estimator exists. This paper proposes an approach to formulate the state estimation in a new manner that is able to formulate together the traditional measurements as well as PMU measurements easily and efficiently. The proposed estimator is tested on IEEE 118-bus system and ERCOT 5514- bus system.

In this paper a new approach for loss allocation is presented. The main idea is voltage angle allocation, i.e. determining the contribution of each contract on the voltage angle of each bus. DC power flow is used to compute a primary solution for angle decomposition. To consider the impacts of system non-linearity on angle decomposition, the primary solution is corrected in different iterations of decoupled Newton-Raphson power flow. Then, the contribution of each contract in power flow of each transmission line is computed based on angle decomposition. The loss of each transmission line is allocated among different contracts proportional to the square of their contributions in the line flow. The presented approach is applied to the IEEE 30-bus test system.

As a useful tool for combinatorial optimisation over continuous and discrete variables, the mixed-integer linear programming (MILP) approach can address complex control and planning models providing high computational efficiency as well as robust behavior. On power system planning, previous work using MILP employed conventional dc load flow model neglecting reactive power, power loss and transformer tap ratios. In this paper, a novel thyristor-controlled series compensator (TCSC) allocation model is proposed based on recently reported line flow equations and basic linearisation rule of binary-continuous products. The objectives of the planning strategy are to improve system loadability by choosing proper locations and settings of devices. Simulation results are presented and discussed for IEEE 9- and 118-bus systems.

This note derives an equation for the ratio of the maximum possible station flow to average line flow in a personal rapid transit or dual-mode system using fully synchronous control. It is shown that such a system is impractical except in very small networks.

The paper presents the implementation of the fast decoupled load flow technique for the inclusion of a multiterminal HVDC link in a large AC system. It is shown in the paper that reliability, computational speed and storage advantages, offered by the basic fast decoupled algorithms are preserved as far as the AC network is concerned. The method described in the paper is versatile to include any particular control mode of the HVDC link by changing some of the elements associated with the DC Jacobian matrix. Further tha outages of ac and dc lines are simulated by modifying the power injected to the affected buses using the fast decoupled line flow algorithms. A test example is worked out to highlight the formulas presented in the paper. The dynamic stability mcdeloof the multiterminal HVDC system is then attempted by using the linearised version of the DC Jacobian matrix and replacing the AC network by equivalent generations and loads.

Extending the theoretical foundations established in Part I(1), this paper further describes this efficient method of computing the real-time load flow solution for a power system network. An efficient numerical solution technique particularly applicable to this problem is outlined. Relative weighting of the measurements is analyzed in terms of the measurement accuracies. A method is given for dynamic determination of the frequency of the state estimate calculations. The effects of real-time changes in the network are discussed.

This paper presents a methodology for economic dispatch accounting line flow constraints in base case conditions. Functional Link Network (FLN) developed by Pao in 1989 has been used for this purpose. This single layer network has been trained using delta rule. Training set data have been obtained using Davidon-Fletcher-Powell's (DFP) method accounting inequality constraints by exterior penalty function method. An optimal brain damage technique has been employed for truncation and elimination of small weights. The algorithm is tested on IEEE 6-bus and 14-bus test systems.