Samarjit Sengupta

Bandpass Second-Degree Digital-Integrator-Based Power System Frequency Estimation Under Nonsinusoidal Conditions

A novel digital signal processing algorithm for online estimation of the fundamental frequency of the distorted power system signals is presented. The basic algorithm relies on the development of an efficient variance reduction algorithm; and design of a new stable bandpass infinite impulse response (IIR) second-degree digital integrator (SDDI) with reduced approximation error. Compared with the well-established technique such as the enhanced-phase-locked-loop (EPLL) system, the proposed algorithm provides the following: 1) higher degree of immunity and insensitivity to harmonics and noise and 2) faster response during step frequency change. Structural simplicity, wide range of application, controls over speed and accuracy, and parameter robustness are other salient features of the method. The only limitation as compared with the EPLL system is its slower transient response during step change in signal magnitude. Based on simulation studies, performances of the proposed algorithm at different operating conditions have been presented, and its accuracy and response time have been compared with the EPLL systems.

Area-Based Approach in Power Quality Assessment

This paper presents an approach for assessment of power quality parameters using analysis of fundamental and harmonic voltage and current waveforms. Park transformation technique has been utilized for the analysis in three-phase system, which has reduced the computational effort to a great extent. Contributions of fundamental and harmonic components in power system voltage and current signals have been assessed separately. An algorithm has been developed to calculate the power quality parameters from online signals. This algorithm has been simulated for a radial system, and the results have been compared with that obtained from a standard FFT-based system. The results are seen to be in good agreement with that of the standard system.

A Low-Cost Fault-Tolerant Real, Reactive, and Apparent Power Measurement Technique Using Microprocessor

Errors may creep in when measuring power by conventional methods due to the inductance and capacitance of the coils and the induced eddy current in the metal parts of the instruments through the alternating magnetic field of the current coil. Apart from these, if a fault occurs in any of the potential transformer secondary circuits or the potential coil of the measuring equipment, a conventional meter cannot detect it, which results in underregistration. In this paper, a microprocessor-based threephase real, reactive, and apparent power measurement system is developed, which displays the power being fed to a load under both normal and faulty conditions. The microprocessor provides a simple, accurate, reliable, and economical solution to these problems. A framework of the hardware circuitry and the assembly language program for the evaluation of power values is given, and the problems to which attention should be paid to execute the proposed algorithm using the microprocessor are discussed. Illustrative laboratory test results confirm the validity and accurate performance of the proposed method in real-time.

Novel diagnosis technique of mass unbalance in rotor of induction motor by the analysis of motor starting current at no load through wavelet transform

This paper presents an improved technique for detection of mass unbalance in rotor of an induction motor by the analysis of transient stator current during starting period using both discrete wavelet transform (DWT) and continuous wavelet transform(CWT). The unbalanced magnetic pull due to centrifugal force developed for mass unbalance in rotor produces excessive vibration in the rotor as well as in the stator, resulting changes in air gap flux distribution which induces voltage in the rotor and in the stator and generation of unique signature pattern in the stator current. During starting, unbalanced magnetic pull is very high, the rotor is pulled across the whole air gap which increases the amplitudes level of the harmonics already present and generation of new harmonics due to this fault in the stator current. In the present paper, the starting current at no load is captured and analysed for diagnosing the motor fault. As motor current signature (MCS) significantly depends on loading condition of the induction motor during steady state, the detection of faults using MCS at no load or light load by FFT technique is difficult. This has been overcome by this proposed improved technique as motor current does not depend on load and is very high even at no load during starting. This technique has been developed and implemented in the laboratory using machine fault simulator.

Power quality assessment in V-V, Clarke and Park domain

This paper presents a computer aided novel technique for electric power quality assessment. This has been done by assessment of unbalance and presence of harmonics in a power system. This is achieved by developing some feature patterns formed by power system data, wherefrom rule set has been generated to analyze unbalance and presence of harmonics in a power system. The study of the unbalance is accomplished in voltage-voltage plane, whereas the study on harmonics is done in Clarke and Park domain using Clarke and Park transformation matrices.

The Nonuniform Discrete Short Time Fourier Transform - A New Tool for Electrical Power Components' Monitoring

This paper presents a new discrete short time Fourier transform (DSTFT) implementation algorithm, called nonuniform discrete short time Fourier transform (NDSTFT) for real time estimation of power components according to the IEEE Standard 1459-2000. The proposed NDSTFT algorithm is capable of detecting the spectrum of each finite short time section of the power signals at arbitrarily located specified frequencies and is able to perform sample by sample processing, thus, suitable for real time implementation in uniprocessor system. The NDSTFT based power components estimation algorithm has been implemented in real time by means of a Texas Instruments TMS320VC5416 digital signal processor. Fast and accurate estimation of power components has been observed utilizing the developed scheme.

Induction Motor and Faults

The chapter deals with general description of an induction motor followed by different faults. First, construction of induction motor has been discussed. Then a review of induction motor fault has been presented. Faults like rotor broken bar, mass unbalance, stator faults, single phasing, crawling, bearing faults, etc. are discussed along with causes and effects.

Congestion management of a multi-bus transmission system using distributed smart wires

Congestion management, demand for increase of reliability, upcoming renewable generation causing distributed generation and increase of load demand have led to the development of new technologies capable of improving network operation without new line construction. An attempt for reconfiguration of an existing network with the help of sectionalizing switches to find out the least loss configuration sometimes causes overloading of certain lines. Among many developed technologies, Smart Wire is a new concept for a low-cost, high reliability method to control the power flow in a transmission line. This paper presents a technique by which, if congestion is detected, it can be managed by a Smart Wire. It improves a passive grid asset, like a power line; with improved reliability relative to traditional FACTS because it can be bypassed if it fails, leaving the passive asset in service. This is called fail-normal operation.

Alleviation of line congestion using Multiobjective Particle Swarm Optimization

This paper presents a methodology based on Particle Swarm Optimization technique for rescheduling of generation patterns to manage congestion in contingent power networks. In deregulated systems, line congestion attract additional penalties which add on to the overall operational cost to be incurred by the Independent System Operators (ISO), apart from causing limit violations, and stability problems. Thus, limiting the congestion level of lines and restricting power flows within the safe limits is important from stability as well as economy point of view. The algorithm proposed in the present paper uses a Standard Sensitivity Index to identify the congested zone(s) in a large power network and then adopt corrective actions for limiting line congestion at the cost of a nominal rescheduling cost without any load curtailment and installation of FACTS devices. It has been demonstrated that the proposed method can reduce congestion even below the minimum level obtained from the conventional cost optimization results. It has been depicted that the methodology on application can provide better operating conditions in respect of improvement of bus voltage profile. The efficiency of the proposed methodology has been tested on a IEEE 30 bus benchmark system and the results look promising.

Clarke and Park Transform

This chapter presents a brief idea of Clarke and Park transformations in which phase currents and voltages are expressed in terms of current and voltage space vectors. The space vectors are then represented in stationary reference frame. Then general rotating frame of reference has been introduced. The rotating frame of reference is then described in terms of d and q axes. The space vector is then expressed with respect to d-q reference frame. Clarke, Park and Inverse Park transformations have been described. These transformations are used in the subsequent chapters for assessment of power quality items.