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This paper presents an advanced path-integral algorithm to determine bus-wise transmission loss allocation using smooth properties of loss sensitivities. The properties of loss sensitivity have been investigated with typical system trajectories in consideration of the market-operating strategy. The smoothness of the loss sensitivity is extensively examined along the integral paths to verify that all paths of straight line segment keep the smoothness of loss sensitivity well. The previous study has shown that, given an integral path, accurate loss allocations can be obtained by the path integral method, however, the integration procedure may require excessive computational burden for large power systems. This paper proposes an advanced loss allocation algorithm to drastically reduce the computational burden by using the smooth property of the loss sensitivity.

In this paper, a new type of Solid-State Fault Current Limiter(FCL) is proposed. Magnetic Turn off(MTO) FCL is composed of transformer cores and windings. And it utilizes thyristor controller to implement limiting operation. The primary winding is connected to the power grid. The secondary & tertiary windings are wound opposite direction to the primary winding. During the 'Turn On' state, magnetic fluxes produced in the primary winding are canceled out by the secondary winding. The secondary & tertiary windings are controlled by thyristors, and this state makes no impedance throughout the FCL. When fault occurs, MTO FCL will be immediately switched to 'Turn Off' state and this makes the secondary & tertiary windings open. After this operation high impedance will be induced throughout the FCL. MTO FCL is expected to be more practical to implement, because it does not use any superconducting materials or additional complex cooling systems.

In this study, the state estimation of electric power systems which contain FACTS and HVDC devices is investigated. A detailed steady-state model for the Unified Power Flow Controller (UPFC), the most general power flow controller, is formulated and implemented. The model is specified by the steady- state model parameters, such as voltage magnitudes and phase angles for the parallel and the series branches, and reactances associated with the parallel and the series transformers. The DC side HVDC bus net injections are assumed to be measured and error-free for the state estimation of HVDC. In order to include the new devices in the system, formulations of the state estimation algorithm are modified. Simulations of the test system are presented to demonstrate the use of the developed program. Test results show that the developed solution algorithms and formulations for the FACTS and HVDC devices are valid and effective.

As the competitive market system has been introduced to the electrical power trade, the priority concern would be that the price of electrical power should be reasonable. It is because, when this rule is solid, we can avoid the distortion of competition and assure the greater efficiency in management. LMP(Locational Marginal Price) means marginal price at each bus. This components consist of energy , loss and congestion cost. At this point, the LMP result that is calculated by traditional model is changeable by the location of the slack and can not be used in bilateral Transaction. This paper proposed algorithm is proved its rationality and credibility by comparing the result of the simulation of virtual 6_bus system that is calculated by traditional method, and showed that the LMP components are changed according to the Transaction Strategy. Furthermore, It shows the effect of additional congestion cost on the transmission line that has bottle neck frequently by simulation.

This paper presents a new algorithm to determine accurate bus-wise transmission loss allocation utilizing path-integrals dictated by the transaction strategy. For any transaction strategy, the total sum of the allocated transmission losses of all buses is equal to the actual loss given by the AC powerflow calculation considering the distributed slack. In this paper, the bus-wise allocation of the transmission loss is calculated by integrating the differential loss along a path determined by the transaction strategy. The proposed algorithm is also compared with Galiana’s method, which is the well-known transmission loss allocation algorithm based on integration. The performance of the proposed algorithm is evaluated by case studies carried out on the WSCC 9-bus, IEEE 14-bus, New England 39-bus, and IEEE 118-bus systems. The simulation results show that the proposed algorithm is fast and accurate with a large step size.

This paper describes a linear matrix inequality (LMI) approach to the design of robust loworder power system stabilizers (PSSs), which are used to damp out local-mode oscillations of synchronous generators. The performance of a PSS is expressed as the location of the closed-loop poles, and a single fixed-gain pole-placement controller is synthesized for a wide range of operating conditions. The synthesis results in simultaneous regional pole-placement stabilization through static output feedback, and is formulated as a novel LMI feasibility problem with a rank condition. A penalty method is applied to solve the rank-constrained LMI problem. Numerical experiments with a single machine connected to an infinite bus system were performed to demonstrate the proposed LMI method, and the results were compared with those of previous work.

This paper proposes a voltage-controlled voltage source inverter (VCVSI) using a coated conductor (CC) as a decoupling inductor. Up to the present, the topologies to protect the power system from a short circuit effectively and to improve power quality simultaneously have been rarely developed. In the proposed topology, a decoupling inductor, which is essential component for a VCVSI operation, was designed with a YBCO CC and was integrated into a VCVSI. However, to determine the optimal CC specification, it is necessary to consider design parameters such as fault current, active power flow from the system and reactive power required by the decoupling inductor. With the optimal CC specification, the proposed system can perform the fault current limiting operation for a short circuit. In addition, in the normal time, it can compensate for the reactive power that a non-linear load requires, as well as perform load voltage stabilization. Specifications for a test model are discussed and the fault current limiting and power conditioning operations are presented. By using computer simulations, we validate the analyses and discuss its multi-operation.

SCADA is the acronym of Supervisory Control and Data Acquisition which means the communication scheme for telemetry measurement and control of the automated control system. SCADA system was introduced for the monitor and control of manufacturing process on local basis in the beginning. As the information technology has been advanced SCADA system has also evolved into larger and more automated system covering wide area. Today SCADA system has been introduced into the critical infrastructures as well as modern industrial facilities. Electric Power system is a representative system using SCADA network. Electricity is not able to be stored in large quantity especially considering economic efficiency therefore it is critical to be balanced between supply and demand, which is the main function of SCADA system. This paper introduces the structure and characteristics of SCADA system and communication, and the security devices which it has been studied for securing SCADA communication.

This paper presents a new systematic approach to find a global solution to economic dispatch (ED) with multiple fuel units using a function merger (FM). Currently, no systematic approach has been developed to find a global solution to economic dispatch with multiple fuel units. Various heuristic methods have been proposed, however it is almost impossible to guarantee a global solution by those methods yet. The proposed method uses the FM and λ-P functions. A FM merges several fuel cost functions into one that satisfies the optimal conditions of an ED. The FM procedures are described in detail with illustrative examples. The global optimality of the proposed method is checked with the ACM (All-Combination Method). The proposed method is tested with a 10-generator system. The results show that the global optimality is achievable by the proposed method.

This paper presents a study to estimate the composition of an electric load, i.e. to determine the amount of each load class by the direct measurements of the total electric current waveform from instrument reading. Kalman filter algorithm is applied to estimate the electric load composition on a consumer side of a distributed power system. The electric load supplied from the different voltage level by using a non-ideal delta-wye transformer is also studied with consideration of the practical environment for a distributed power system.

A new acridine derivative was synthesized as a fluorescent chemosensor for Zn2+ in an 100% aqueous solution. Compound 1 displayed a selective CHEF (chelation enhanced fluorescence) effect with Zn2+, on the other hand, a similar anthracene derivative 2 did not display any significant change with the metal ions examined.

In this paper a Hybrid Real Time HYDC Simulator for both operator Training and Re-searching in the Cheju-Haenam HYDC System is proposed and its performance is studied by means of RTDS (Real Time Digital Simulator), EMTDC (Electro-Magnetic Transients system for DC), PSS/E (Power System Simulator for Engineering), and experienced scenarios. The objective of this paper is to represent the strategy in development for KEPCO's hybrid HYDC simulator for the Cheju-Haenam HYDC system. This simulator consists of two DC stations, DC cables, external digital/analog controllers, monitoring systems and control desk for education, and AC networks. Its suitability for operator's education is tested during startup/shutdown and normal state operations. Dynamic performances of it are also verified.

This paper presents a new approach to economic dispatch (ED) problems with actual fuel cost curves using a λ-P table method. Conventional ED algorithms are developed on the basis of approximated fuel cost function, which cannot be adapted to actual fuel cost curves properly. In this paper, a λ-P table method is proposed to improve accuracy of ED solution. It is noted that the proposed algorithm is very simple and has some advantages in considering the must-run condition and modifying the ED solution associated with generator addition/elimination. Numerical results of the proposed algorithm are compared with those of the conventional algorithms.

This paper presents a new approach to perform time simulation of power system transient stability using implicit quadratic integral method. Fast and reliable simulation of the transient stability is required to achieve high reliability based on the online stability assessment. The trapezoidal method has been mainly adopted for this purpose. However, the proposed method shows the possibility of improvement in accuracy with no loss of the computation speed. The proposed method is tested with some typical case of ‘stiffness problem' and for transient stability analysis in power systems.

This paper deals with a numerical method for the design of mixed H2/H∞ static output feedback controllers. We first formulate the problem as a new type of rank-constrained linear matrix inequalities (LMIs). Then, the LMI optimization problem subject to a rank condition is tackled by the recently developed penalty function method, where a linear penalty function is introduced for the nonconvex rank constraint. The overall procedure results in solving a series of convex optimization problems. With an increasing sequence of the penalty parameter, the solution of the penalized optimization problem moves towards the feasible region of the original nonconvex problem. Comparisons with previous research are performed to illustrate the proposed method.

This paper proposes a computation method for fixed order controller synthesis which often arises in H ∞ or robust control. With the motivation that the fixed order control problem can be casted to a non-convex quadratic objective function minimization subject to linear matrix inequality (LMI) constraints, a quadratic semidefinite programming (SDP) problem is solved by primal dual interior point method (IPM). The advantage of the proposed method is two-fold. First, the existing SDP solving method can be used with a slight modification. Second, since the method directly computes the solution of the problem, much faster results can be obtained than the existing successive LMI relaxation method such as cone complementarity linearization algorithm. In order to demonstrate the algorithm presented, an excitation system for a synchronous generator connected to an infinite bus is designed and simulated. A proportional-integral type automatic voltage regulator and a power system stabilizer considering H ∞ performance are co-designed to provide appropriate damping for the system. The results show the practical applicability of the method.

In this paper, an EMM(Equivalent Mechanical Model) is developed to explain the voltage collapse mechanism by reflecting the effects of reactive powers. The proposed EMM exactly represents the voltage instability mechanism described by the system equations. By the use of the EMM model, the voltage collapse mechanism has been illustrated to explain the role of the load power factor by showing the exactness of the results. The stable region has been investigated with a reactive-power-controlled two-bus system, which shows that special alerts are required when the system operates with leading power factor. It is also discussed a system transform technique to eliminate the resistance component of the Thevenin equivalent impedance for practical applications considering load factors.

This paper presents a new theoretical approach to energy-based power system analysis using the equivalent mechanical model for multibus power transmission systems. On the basis of mechanical analogy, an exact energy integral expression is derived for lossy multi-bus systems through rigorous energy analysis. A simple rigid rod model of mechanical power transfer system is introduced to address the physical meanings of potential energy terms associated with transfer conductances as well as transfer susceptances. Finally, energy-based analysis has been proposed with the Lagrange's Equations and Hamiltonian Equations, which shows that the energy function has all information of the power system characteristics.

This paper proposes a new approach to simultaneous contingency analysis with Double Circuit Simultaneous Faults. To improve the accuracy and the computation speed of the contingency analysis, the Peterson method has been adopted with the ShennanMorrison formula and a matrix decomposition method. The triangular factor table technique is also adopted, to compute the inverse matrix in the loadflow calculation. Based on these methods, simulation considering several cases show that double circuit simultaneous faults analysis suggested in this paper offer fast loadflow computation in short time by calculating relative accurate phase angle variation

Recently, the deregulation has been a hot issue in electric power industries with the introduction of the bidding system to electric power markets. One of the main topics associated with the deregulation is spot pricing where the exact analysis of transmission loss and the method of calculating reliable penalty factor play an important role. Penalty factors calculated with conventional methods are highly dependent on the location of the slack bus, which brings about unfair competition to Independent Power Producers (IPPs). This paper presents a new method of calculating the exact and reliable penalty factor independent of the change of the slack bus. The proposed method is tested on IEEE 14 bus system, New England 39 bus system and OH-145 bus system. The test results show that the proposed method can give more reliable information of the penalty factors for the regional spot pricing.

This paper presents an extended integral control to load frequency control (LFC) scheme with the presence of generation rate constraints (GRC) in order to get rid of overshoot of the conventional proportional-integral (PI) control. The conventional LFC scheme does not yield adequate control performance with the consideration of the singularities of speed-governor such as rate limits on valve position and GRC. In order to overcome this drawback, an extended integral control is developed for the PI control of the speed governor in the presence of GRC. The key idea of the extended integral control is using a decaying factor to reduce the effects of the error in the past. The decaying factor greatly affects the control performance, and should be carefully selected. This study determines the decaying factor in proportion to the degree of deviation in several levels. The computer simulation has been conducted for the single machine system with various load changes. The simulation results show that the proposed controller based on extended integral control yields much improved control performance, compared to the conventional PI controller.

This paper shows that a well-defined energy function can be developed to reflect the transfer conductances for multi-machine power systems under an assumption that all transmission lines have uniform R/X ratios. The energy function is derived by introducing a pure reactive equivalent system for the given system. In this study, a static energy function reflecting transfer conductances is also derived as well as the transient energy function. The proposed static energy function is applied to voltage stability analysis and tested for various sample systems. The test results show that the accuracy of voltage stability analysis can be considerably improved by reflecting transfer conductances into the energy function.

In this paper the stability region (domain of attraction) of damping-dependent energy functions for multi-machine power systems is analyzed and visualized for two-machine-infinite-system. It is shown that the damping-dependent energy functions give larger estimate of domain of attraction than conventional energy functions which don't consider damping effect. Also the limitation of the previous structure-preserving damping-dependent energy functions for multi-machine systems in absolute angle form is addressed. In order to overcome the limitation an improved damping-dependent energy functions in the center of inertia (COI) form is presented as an extension of the previous work. Finally future work and possible applications are discussed.

In this paper, instant current limiter using a Magnetic Switching for DC power system is proposed. In DC power system, it is very difficult to cut off the fault current because it has no Zero-Crossing. This paper proposes an instant current limiter to reduce the DC current instantaneously by using a magnetic switching circuit, which can be utilized as a DC FCL(Fault Current Limiter) for DC circuit breaker. The existing cut-off approach for DC system uses dI/dt to decide whether the fault occurs or not in order to achieve fast cut-off approach before the fault current is increased. But fast fault decision using dI/dt has a relatively large uncertainty so it would cause malfunctions. With the aid of the proposed FCL, it is possible to achieve a safe cut-off of the fault current after the fault current is increased enough. We can ensure an enough time to decide the fault occurrence and reduce a cut-off capacity and increase a safety to cut off the fault current. The suggested system can also be utilized to AC current limiter for power systems with a large range of application in the future.

This paper represents a calculation method of stochastic generation cost (SGQ taking into consideration the wind power generation expressed as random variables, and shows its necessity. As wind power generation is stochastically predictable, a system demand should be expressed to a random variable with its own probability density function (PDF) instead of a constant value in unit commitment (UQ and economic dispatch (ED) problems, etc. Assuming that the produced wind power generation is fully consumed in power systems, total generation distributed to thermal generators, which becomes a modified system load, is equal to the difference between total system demand and total wind power generation. Given that the total wind generation is based on normal distribution, the modified system load should be also based on normal distribution. The proposed method is applied to illustrative examples and simple UC problems.

This paper describes a linear matrix inequality (LMI) approach to the design of low-order power system stabilizers (PSSs), which are used to damp out local-mode oscillations of synchronous generators. The performance of a PSS is expressed as the location of the closed-loop poles, and a single fixed-gain pole-placement controller is synthesized for a wide range of operating conditions. The synthesis results in simultaneous regional pole-placement stabilization through static output feedback, and it is formulated as an LMI feasibility problem with a rank condition. The rank-constrained LMI problem is solved by the recently developed iterative penalty function method. Numerical experiments with a single machine connected to an infinite bus system were performed to demonstrate the proposed LMI method.

This paper is concerned with an iterative linear matrix inequality (LMI) approach to the design of a structurally constrained output feedback controller such as decentralized control. The structured synthesis is formulated as a novel rank-constrained LMI optimization problem, where the controller parameters are explicitly described so as to impose structural constraints on the parameter matrices. An iterative penalty method is discussed to solve the rank-constrained LMI problem. Numerical experiments and comparisons with previous works are performed to illustrate the practicality of the proposed method.

This paper represents the dynamic behavior of reactive power compensation for the Cheju-Hanam HVDC system. Due to changes in the Juju AC network form as it when the Cheju-Haenam HVDC system was built, the need to simulate the exiting reactive power compensation scheme is rising. In order to consider reactive power supply from new thermal power plants of Jeju AC network, a new-reactive compensation method for the stable operation of the HVDC system is proposed. The strength in Jeju AC network is simulated by PSS/E simulation program. Time domain simulation by PSCAD/EMTDC is used to verify the new reactive compensation method

This paper proposes a hierarchical approach to simultaneous contingency evaluation considering simultaneous double faults. The expectation of contingency impact is discussed with consideration of the probability of fault occurrence and the estimated damage of the fault. A hierarchical approach is adopted for contingency analysis; the higher level deals with the online contingency evaluation for single line contingencies and the lower level deals with offline evaluation for numerous double contingencies. To improve the accuracy and the computation speed of the contingency analysis, the Peterson method has been adopted with the Sherman-Morrison formula and a matrix decomposition method. The triangular factor table technique is also adopted, to compute the inverse matrix in the load flow calculation. Based on these methods, simulation considering several cases show that double circuit simultaneous faults analysis suggested in this paper offer fast load flow computation in short time by calculating relative accurate phase angle variation.

This paper presents a new theoretical approach to energy-based power system analysis for multibus power transmission systems. On the basis of mechanical analogy, an exact energy integral expression is derived for lossy multibus systems through rigorous energy analysis. A simple rigid rod model of mechanical power transfer system is introduced to address the physical meanings of potential energy terms associated with transfer conductances as well as transfer susceptances. Finally, energy-based analysis has been proposed to show that the energy function has all information of the power system characteristics.

This paper presents a new energy function reflecting the damping effect in multimachine power systems. The Lyapunov direct method provides precise and rigorous theoretical backgrounds for stability analysis of nonlinear systems. Incorporating damping effects into accurate estimates of the domain of attraction, which is a minor but crucial point, has been attempted with long history to yield partial success for single machine systems. In this paper, a damping-reflected energy function has been generalized for application to multimachine systems. The generalized energy function is tested for the WSCC 9-bus system to show the semi-negativeness of its time derivative.

This paper presents a new mechanical analogy of power systems for energy-based system analysis based on an equivalent mechanical model (EMM). The EMM is developed on the basis of mechanical analogy of power system by using spring connected rod-inertia system. The proposed EMM introduces an imaginary spring for the analogical correspondence to the transfer conductance of a transmission line with discussion of its energy storage properties. The imaginary spring produces its forces acting on the both ends perpendicular to its displacement vector. The rod-inertia system is completely analyzed in order to show that it has just the same dynamic equations as the power system. The proposed EMM provides theoretical background for energy-based analysis of power systems, which enables us to utilize well-known theories such as Lagrange's equation.

The power quality service has been considered to boost the competition in the distribution side, which is necessary to meet the customers' demands in the near future. Due to increasing demands for the high reliability, the fast service restoration has been a hot issue with the fault tolerable distribution system. In order to ensure high reliability, the scope of service restoration should be extended to severer faults such as multi-feeder outages, bus outages and transformer outages at the substation, and out-of-services of a whole substation. In this panel session, the fast service restoration is discussed with the necessity of developing new approaches to be adapted to the distribution system under deregulation, mainly focusing on fast solution search algorithms, multi-switching strategies for severer fault occurrence, search for the fault section, and fast power flow calculation.

This paper presents an extended integral control to the speed-governor system for damping power system oscillations. The power system oscillations mostly stem from the surplus kinetic energy which is stored in the generator during the fault period. The effective control of the surplus energy can be the most direct method to achieve the system stabilization. The LFC (load frequency control) loop can be utilized as a direct method to control the surplus energy. The proposed controller based on the extended integral control is applied to speed-governor to damp out the local and interarea mode oscillations. The proposed controller also provide good performance under presence of the singularities of speed-governor such as limits on valve position and GRC (generation rate constraints). The computer simulation has been conducted for the two-area multimachine system with various load changes. The simulation results show that the proposed controller yields much improved control performance, compared to the conventional PI controller.

This paper presents a complex line integral approach to derive an energy conservation law which reflects the resistance, flux-decaying effects, saliency with wide adaptability to various detailed generator models including the governor and exciter control loops. Especially, the previous work has shown that an exact energy conservation law can be derived under the assumption of stator network transients being negligible. In this paper, it is shown that an exact energy conservation law can be derived by using the complex line integral approach without any assumptions. Consequently, the proposed energy conservation law is applicable to power systems adopting any kind of detailed generator model. The stator resistance of the generator can be taken into account in a simple manner. The proposed energy conservation law is tested for several sample systems and the results show its validity.

This paper introduces the concept of polarized linear electric network and proposes a new approach to analyze it. It is well-known that the internal impedance of salient-pole generator has two reactance X/sub d/, X/sub q/ corresponding to the direct and quadratic current components. Two different reactance possessed by one circuit element provide the polarization characteristics in the current transfer. This study proposes a new analysis method which shows that the linearity of the polarized linear network makes it possible to calculate generator currents in one step for the given internal voltages and rotor angles of the generators. Tests have been performed for the sample systems, which shows remarkable improvement in computation time.

This study presents an application of fuzzy logic based method to determine the optimal parameters for the extended integral control scheme. The performance of the extended integral control is greatly dependent on the decaying factor. For an optimal or near optimal performance, it is necessary that the decaying factor as well as the feedback gains should be changed very quickly in response to changes in the system dynamics. However, because of its time-varing characteristic, the optimal decaying factor is difficult to be selected analytically. By adopting fuzzy set theory, the decaying factor can be determined quickly to respond to the variation of the feedback signals. This study builds a fuzzy rule base with use of the change of frequency and its rate as inputs. A set of decision rules is established to relate input signals to the decaying factor. The computer simulation has been conducted for the single machine system. The simulation results show that the proposed fuzzy logic based controller yields more improved control performance than the conventional PI controller.