Nasrudin Abdul Rahim

Voltage sag detection - A survey

Voltage sag has been the focus of considerable research in recent years. It can cause expensive downtime. Research on voltage sag detection has also grown up and it is an essential part of the voltage sag compensator. There are many methods have been introduced to measure and detect voltage sags. Among these are RMS Value Evaluation, Peak Value Evaluation, Missing Voltage technique and Hysteresis Voltage Control technique. In this paper, a study is carried out to observe the different techniques of voltage sag detection. Since, precise and fast voltage detection is an essential behavior for a voltage sag compensator, therefore, observation on detection time of each detection methods will also be carried out.

Optimized PID controller for both single phase inverter and MPPT SEPIC DC/DC converter of PV module

Introduced here is an implementation of an optimized Proportional, Integral, and Derivative (PID) controller that controls single-phase inverter and single-ended primary-inductor DC/DC converter (SEPIC). The main improvement is the endowment of classical PID controller with gradient-descent optimization method, which generates exact values for PID-controller parameters Kp, Ki, and Kd, which in turns track the maximum power. The method was applied post-use of Ziegler-Nichols method, reducing optimization time. SEPIC maximum-power-point tracker (MPPT) ensures optimal utilization of PV cells. The method further proves its efficacy in variable-load conditions. TMS320F28335 DSP has been used to implement the controlled pulse width modulation (PWM). The controlled system has been verified by simulation and implemented in a prototype. Then, experimental results have been compared with those for conventional single-phase inverter.

Fuzzy Logic Controller for MPPT SEPIC converter and PV single-phase inverter

This paper introduces an implementation of Fuzzy Logic Controller (FLC) for the single-ended primary-inductor converter (SEPIC) that control the maximum power point tracking (MPPT) signal together with the cascaded single-phase inverter. The extracting of the maximum power through using the SEPIC fuzzy controller is considered the main improvement here. Fuzzy-controlling in duty cycle increases/decreases the voltage level for the SEPIC according to the maximum power. SEPIC MPPT ensures optimal utilization for the PV array. The controller further proves its accuracy in variable-load conditions. TMS320F28335 DSP has been used to implement the controlled pulse width modulation (PWM). The controlled system has been verified by simulation and implemented in a prototype. Then, experimental results have been compared with those for conventional single-phase inverter.

Self-tuned NFC and adaptive torque hysteresis based DTC scheme for IM Drive

This paper presents a simplified self-tuned Sugeno-type neuro-fuzzy controller (NFC)-based direct torque control (DTC) scheme for induction motor (IM) drive. A simple tuning algorithm is developed based on the reference and actual acceleration of the motor. The online tuning strategy adjusts the parameters of the consequent layer of the NFC in order to minimize the square of the error between the actual and the reference acceleration of the motor. In a conventional DTC scheme, the band limits of flux and torque hysteresis controllers remain fixed, and hence, the torque and flux ripples are high. In order to minimize the torque ripples of the IM, the hysteresis band limits are adjusted online for the torque hysteresis controller. Thus, the proposed NFC is used to achieve high dynamic performance of the drive, and the variable hysteresis controller is used to reduce the steady-state torque ripple. The proposed NFC-based DTC scheme is successfully implemented in real time using the DSP board DS1104 for a prototype 1-hp squirrel-cage IM. The performance of the proposed drive is tested at different operating conditions in both simulation and experiment. The proposed NFC-based DTC scheme is found superior to the conventional DTC scheme in both steady-state and transient conditions.

A novel multi-string five-level PWM inverter for photovoltaic application

This paper presents a single-phase multi-string five-level PV inverter topology for grid-connected photovoltaic (PV) systems with a novel PWM control scheme. Three PV strings are cascaded together in parallel configuration and connected to a five-level inverter to produce output voltage in five levels: zero, +1/2Vdc; Vdc; -1/2Vdc and -Vdc. Two reference signals identical to each other with an offset equivalent to the amplitude of the triangular carrier signal were used to generate PWM signals for the switches. DSP TMS320F2812 is used to implement this PWM switching scheme together with a digital PI current control algorithm. The inverter offers much less THD and can operate at near unity power factor. The validity of the proposed inverter is verified through a prototype. The experimental results are compared with conventional single-phase multi-string three-level grid-connected PWM inverter.

Simulation of grid connected THIPWM-three-phase inverter using SIMULINK

This paper presents a grid connected system. Three phase DC-AC inverters used to convert the regulated DC power to AC power suitable for grid connection. Third harmonic injection PWM (THIPWM) was employed to reduce the total harmonic distortion (THD) and for maximum use of the voltage source. the accurate generation of THIPWM minimize the THD and make the inverter suitable for grid connection, by synchronizing the inverter voltage with the grid voltage. The application of THIPWM to inverter increases efficiency of the inverter. Simulation results validate the developed model and the proposed system.

An analytical complementary FEA tool for optimizing of axial-flux permanent-magnet machines

This paper presents an analytical approach to calculate the magnetic field in a slotted axial-flux permanent-magnet machine. The method is modeled on a simple nonlinear magnetic analysis of an equivalent magnetic circuit with a saturationpossible magnetic-reluctance core in a slotted axial-flux permanent-magnet machine. It calculates flux distribution and torque characteristic in various operating conditions. Its accuracy and validity are verified by results that match those of a Finite Element Analysis model. This method serves as a complementary design tool to FEA especially in expediting design optimization of an electrical machine. The method is as accurate as FEA but betters FEA with its shorter computation time, making it the better alternative in initial estimations. After verification of the analysis, sensitivity to design variables by using the proposed model is presented. The sensitivity analysis through the proposed magnetic circuit of the AFPM machine provides an effective way for selection of design parameters. These parameters are iteratively adjusted through multi-objective optimal design in order to obtain maximum output torque and efficiency. Simulation results show AFPM machine efficiency to be affected the most by its diameter, followed by magnet fraction, and the least by back-iron thickness.

A comparison between the TORUS and AFIR axial-flux permanent-magnet machine using finite element analysis

This paper presents a comparison between TORUS and AFIR, the two topologies for double-sided axial-flux permanent-magnet machines. Their slotted and non-slotted topologies were investigated and compared in terms of power density and torque quality. The critical field analysis of the topologies was by finite element method. Results show TORUS topologys high power-density in high current-density and low electrical-loading. AFIR topology has high power in low current-density and high electrical-loading. Non-slotted TORUS and AFIR AFPM machines have negligible cogging torque and lower ripple torque than their slotted counterparts.

Small-signal AC modeling technique of Buck converter with DSP based Proportional-Integral-Derivative (PID) controller

Control applications of switched mode power supplies have been widely explored. The main objective of research and development (R&D) in this field has always been to find the simplest method to analyze and model the DC/DC converter and the most suitable control method to be implemented in various DC/DC converter topologies. This paper presents a simple and systematic approach to the design of a practical Digital Signal Processing (DSP) based Proportional-Integral-Derivative (PID) voltage controller for Buck converters. A simple and easy-to-follow design procedure is demonstrated. Experimental results are presented to illustrate the design procedure.

An iterated-based optimization method for economic dispatch in power system

This paper proposes an iterated-based algorithm to solve economic dispatch (ED) problem. The algorithm aims to determine the schedules of generating units in order to minimize the total generation cost. The problem is formulated mathematically as an optimization problem including objective function and constraints. Also the network loss as an important element for economic dispatch in power systems has been considered in the problem. The proposed method applied on 3-unit power system and the results were obtained and compared to classical and intelligent optimizations methods. The results clearly show that the proposed algorithm is capable of solving ED problem as well as other optimization methods.