Abstract

Nowadays, Digital Sinusoidal PWMs are playing a major role in the generation of pure sinusoidal waveforms using micro-controller based inverters. The types of DSPWMs that can be generated depend on the micro-controller hardware resources and are therefore limited, but provide performance benefits not possible with an analogue controller. For instance, digital controllers offer a programmable solution and therefore more flexibility, as advanced algorithms and additional features can be added to the system in software instead of hardware. Digital controllers are also less sensitive to environmental conditions and show precise behaviour compared to their analogue counterparts. In this paper,  the theory of the three major DSPWMs are presented, including mathematical models and simulation results. The PWM patterns required to generate these DSPWMs and the benefits and limitations of each are examined.

Abstract

This paper proposes vector based load flow technique for the solution of balanced and unbalanced radial distribution networks using sparsity technique. The proposed method presents a simple algorithm to solve radial distribution systems with realistic R/X ratio, which involves the evaluation of a simple algebraic expression for receiving end voltage. The algorithm uses basic principle of circuit theory, and can be easily understood. The proposed algorithm has been tested with several distribution systems and results are compared with an existing method [10]. The effectiveness of the proposed algorithm is demonstrated through three examples, two for balanced and another for unbalanced radial distribution networks.

Abstract

The aim of this research is to detect incipient faults like turn to turn faults in the windings of power transformer using Wavelet transform technique. An experimental procedure of frequency response analysis (FRA) test is conducted on the windings of power transformer by applying impulse voltage of 1.2/50µs wave and the winding neutral currents are recorded. The recorded waveforms are convoluted into wavelet domain and the winding deformations are identified. Different incipient faults have been simulated using SPICE software and the waveforms are analyzed using MATLAB WAVELET toolbox. Experiments and simulations are carried out on a 61MVA, 230kV class transformer winding to identify the winding deformations on the characteristics of transformer. In this paper simulated results for discrete wavelet transform have been presented for fault identification. By using this technique, exact time of fault where it is occurred can be identified. By knowing the exact time of fault occurrence, we can detect the exact location of the fault.

Abstract

In this paper we consider and solve the motion planning problem for an underwater vehicle. The nonlinear control system is referred to as nonholonomic system due to nonintegrability of its generalized velocities. The motion planning problem with constraints on the velocities is transformed into a control problem having fewer control inputs than the degrees of freedom. Controllability results for this nonholonomic system are presented. The paper presents design of a feedback control law for the trajectory tracking. For the design of feedback controller, the system is transformed into chained form. The work presented in this paper is a step towards the study concerning the applicability of kinematic-based control on underwater vehicles.

Abstract

The Field Programmable Gate Array (FPGA) technology becomes widely used in industry. To prepare engineering students better for the need of the industry, the FPGA technology has been used in the academic filed as one cost-effective platform for prototyping digital systems in both teaching and research activities. This paper presents the usage of FPGA technology in the design of a digital audio recorder. It describes several building blocks including power amplifiers, analog-to-digital converter (ADC), digital-to-analog converter (DAC), SRAMs, LCD and the role of FPGA as a central controller. The main focus of this paper is to investigate the circuit design issues and Verilog hardware description language based FPGA design. The implementation of this digital audio FPGA project has been tested and the audio speech sound can be played back with the satisfying result.

Abstract

In this paper, design and implementation of a low power inverse SINC filter (ISF) is described. The proposed ISF is designed to compensate for SINC distortion and maintain flat output amplitude over the bandwidth of 0 to 80% of the first Nyquist zone. In order to reduce circuit area and power consumption, a modified canonic signed digit (MCSD) algorithm is used to replace multiplications with additions, subtracts, and logic shift. In addition, binary shifts are replaced by hardwiring without using any logic gates. The circuit area required for MCSD multiplication is thus approximately proportional to the number of adders and subtractors. Since the impulse response of this filter is symmetrical relative to the centre, the filter is further simplified by adding the symmetrical taps outputs together before the “multiplications”. The proposed ISF is implemented in 0.18µm CMOS technology. With the filter length equal to 9 and input/output interfaces set to 12 bits, the power consumption of the core area is 2.785 mW when clock frequency is 50 MHz, and 8.342 mW when clock frequency is 150 MHz.

Abstract

A lot of research effort has been put in recent years on sensorless drive system for reason such as reliability, robustness, ease of control etc. A number of sensorless schemes are in practice for three-phase drive system. An attempt is made here to implement the existing sensorless techniques on a five-phase induction motor drive system under vector controlled condition. This paper presents a comparison between the performances of an adaptive flux observer and those of an extended Kalman filter-based algorithms, used to estimate the rotor speed  in a vector-controlled five-phase induction motor drive. The estimate is obtained by measuring stator voltages and stator currents in both schemes. Performance of vector controlled drive system is investigated for acceleration, loading and reversing transients. Simulation results are provided.

Abstract

This paper analyses various space vector PWM schemes for a seven-phase voltage source inverter. At first the conventional method of utilising only two neighbouring large active space vectors and a zero space vector is illustrated. This is followed by using four active space vectors and finally six active and a zero space vectors are used to synthesis the input reference. A comparison of the developed schemes is presented based on various performance indices. Extensive Simulation results are provided.

Abstract

A voltage source inverter is commonly used to supply a variable frequency, variable voltage to a three phase induction motor in a variable speed application. A suitable pulse width modulation (PWM) technique is employed to obtain the required output voltage in the line side of the inverter. Real-time methods for PWM generation can be broadly classified into triangle comparison based PWM (TCPWM) and space vector based PWM (SVPWM). In TCPWM methods such as sine-triangle PWM, three phase reference modulating signals are compared with a common triangular carrier to generate the PWM signals for the three phases. In SVPWM methods, a revolving reference voltage vector is provided as voltage reference instead of three phase modulating waves. The magnitude and frequency of the fundamental component in the line side are controlled by the magnitude and frequency, respectively, of the reference vector. In SVPWM based inverter determination of sector at each instant of the output voltage is the key algorithm which is very complex, where as TCPWM produces larger magnitude of harmonics in the output voltage so we proposes a novel carrier in lieu of conventional triangular carrier. The proposed carrier gives good fundamental component and less total harmonic distortion when compared with the conventional triangular carrier. The proposed carrier was implemented in the real time using an arbitrary signal generator AFG3102.

Abstract

This paper demonstrates an application of fuzzy logic to the load-frequency control (LFC) using fuzzy gain scheduling of PI controllers. The controller has been designed for a single area system, two-area interconnected power system. The fuzzy based PI controller is designed using a set of control rules, and the control signal is directly deduced from the knowledge base and the fuzzy inference. A comparison between a conventional PI controller and the proposed fuzzy controller is presented and it has been shown that the proposed Fuzzy controller can generate the best dynamic response with less overshoot and settling time following a step load change.

Abstract

A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a mis-operation of end user equipments. Utility distribution networks, sensitive industrial loads and critical commercial operations suffer from various types of outages and service interruptions which can cost significant financial losses. With the restructuring of power systems and with shifting trend towards distributed and dispersed generation, the issue of power quality is going to take newer dimensions. In developing countries like India, where the variation of power frequency and many such other determinants of power quality are themselves a serious question, it is very vital to take positive steps in this direction .The present work is to identify the prominent concerns in this area and hence the measures that can enhance the quality of the power are recommended.

This paper describes the techniques of correcting the supply voltage sag, swell and interruption in a distributed system by three power electronic based devices i.e., Dynamic Voltage Restorer, Distribution Static Compensator and Solid State Transfer Switch. A new PWM-based control scheme has been implemented to control the electronic valves in the two level VSC used in D-STATCOM and DVR. A DVR injects a voltage in series with the system voltage and a D-STATCOM injects a current into the system to correct the voltage sag, swell and interruption. The SSTS ensure continuous high quality power supply to sensitive loads by transferring the load from a faulted bus to healthy one. Comprehensive results are presented to assess the performance of each device as a potential custom power solution.