Volume 12, Issue 3

Transmission line parameters are essential inputs to various power system analysis programs and applications such as protective relaying algorithms, and precision of line parameters is thus significant in ensuring the analysis accuracy and algorithm reliability. This paper proposes methods for estimating positive sequence parameters of a series compensated transmission line. The methods are based on distributed parameter line model and utilize voltages and currents from both terminals of the line during normal operations. In particular, based on nonlinear estimation theory, an optimal estimator is designed for deriving positive sequence line parameters. The algorithm is capable of detecting and identifying bad measurement data, and thus improving the estimation accuracy. The proposed method is independent of the operation status of the compensation device.

Frequency oscillations due to large load disturbance can be effectively damped by fast acting energy storage devices, because additional energy storage capacity is provided as a supplement to the kinetic energy storage in the moving mass of the generator rotor. The energy storage devices share the sudden changes in power requirement in the load. This paper deals with the concept of Load Frequency Control (LFC) in a deregulated power system considering Battery Energy Storage (BES) system. Time domain simulations are carried out to study the performance of the power system and BES system. The performance of the power system under realistic situation is investigated by including the effects of Generation Rate Constraint (GRC) and governor Dead Band (DB) in the simulation studies.

In this paper, the perfect harmonic cancellation (PHC), unity power factor (UPF) control strategies of distribution static compensator (DSTATCOM) are compared along with a newly proposed control strategy. In the proposed strategy, to get the best power factor, the conductance factors for the compensated load are evaluated for a specified source current total harmonic distortion (THD) limit. The performance of this method along with perfect harmonic cancellation (PHC) and unity power factor (UPF) strategies is evaluated on a distribution system model developed using PSCAD 4.2.1. In the distribution system, harmonic resonance is one of the prime factors for the harmonic propagation. Hence, in damping the harmonic resonance, selection of an appropriate control strategy for the DSTATCOM is crucial and this is verified with a detailed study. The simulation results are presented to show the performance of these strategies in load compensation and damping the harmonic propagation in the distribution system.

In this paper on strong white Gaussian noise background based on discriminant analysis theory, we mainly adopt synchronized sequence measurements of PMU to search for laws of electrical quantities marked changes. We have developed a method to quickly and accurately discriminate fault components and fault sections. The research has shown that the fault discrimination by discriminant analysis theory is effective and reliable. Under the interference of strong random white Gaussian noise, discriminant analysis still has high redundancy.

Power line communication (PLC) is a promising technique for information transmission using existing power lines. We analytically model a finite-source PLC network subject to channel noise (disturbance) and evaluate its call-level performance through a queueing theoretic framework. The proposed PLC network model consists of a base station (BS), which is located at a transformer station and connected to the backbone communication networks, and a number of subscriber stations that are interconnected with each other and with the BS via the power line transmission medium. An orthogonal frequency division multiplexing based transmission technique is assumed to be used for providing the transmission channels in a frequency spectrum. The channels are subject to failure during service due to disturbance. We determine the steady-state solution of the proposed model and derive a set of performance metrics of interest. Numerical and simulation results are presented to show the derived metrics with respect to different system parameters. The proposed modeling method can be used for evaluation and design of future PLC networks.

Nowadays a sensor-less vector control system for a motor drive becomes promising to avoid a position sensor. A back electro-motive-force or flux observer is used for sensor-less drive of permanent magnet synchronous motors from middle to high speed range. Thus, the estimation accuracy of the observer influences sensor-less drive performance. This paper proposes a sensor-less vector control system using the H? flux observer in which the observer gain is designed based on the H? control theory. This observer is insensitive to high frequency disturbances such as voltage disturbance due to non-linearity of PWM voltage source inverter, measurement noise of current sensors, and modeling errors. So, the total performance of a sensor-less control system is enhanced. The detailed configuration of the H? flux observer is described in this paper. Simulation results are compared with the conventional full-order flux observer-based sensor-less system.

This paper investigates and compares wind power extraction from a DFIG (doubly-fed induction generator) wind turbine using stator-voltage and stator-flux oriented frames. The paper analyzes how wind power extraction control of a DFIG wind turbine is converted to speed control, and then how speed and reactive power control of the wind turbine is converted to generator current control using the two different orientation frames. The paper also investigates what are the differences in developing wind power extraction control strategies of a DFIG wind turbine using the two different orientation frames. Simulation study is conducted for a 1.5MW DFIG wind turbine, in which the turbine driving torque is modeled by considering typical wind turbine aerodynamic characteristics. The study shows that the performance of DFIG wind power extraction is similar using both stator-voltage and stator-flux oriented frames. But, it is found that a conventional wind power extraction approach using the stator-flux oriented frame could deteriorate the power quality of the DFIG system while it is more stable to estimate the position of the stator-flux space vector by simply adding -90 degree to the stator-voltage space vector.

A power system analyst wants to be absolutely sure, whether the divergence of power flow method is really due to infeasible operation, or failure of the numerical method, while performing power flow studies. Because of the special structure and characteristics of a distribution system, Newton based methods are not very well suited. Forward/backward sweep methods are well suited for these systems, which exploit the structural advantage of distribution systems. An efficient power flow is required for the analysis of ill-conditioned or highly stressed systems, which are more common in unbalanced systems. In this paper, a robust non-divergent power flow is developed for distribution system using optimal multiplier. It is based on Newton-like power flow derived from conventional forward backward sweep distribution power flow. Two versions of the power flow methods (i) normal variable matrix and (ii) constant matrix have been investigated. Results for three sample systems, with different loading conditions, demonstrate the potential of the proposed algorithm.