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The need of higher powers in electrical drives has forced the researchers to develop new power source possibilities. Multilevel inverters have been presented as a cost effective solution for various high voltage and high power applications including power quality and motor drive problems. The traditional pulse width modulated (PWM) Inverter does not completely eliminate the unwanted harmonics in the output waveform. Using the multilevel inverter as an alternative to traditional PWM inverters for electric motor drive applications is investigated. The concept of the Optimized Harmonic Elimination Stepped-Waveform (OHESW) technique for a multilevel inverter is presented. The effectiveness of this technique in minimizing the inverter switching losses and its output voltage harmonic content which cause reducing harmonic losses and torque pulsations of an induction motor fed form is investigated analytically. Comparison between the Selective Harmonic Eliminated PWM (SHEPWM) as a traditional PWM technique for three-level inverter and the OHESW technique for multilevel inverter with regard to the switching losses, harmonic distortion, additional harmonic losses in the motor and the pulsating torques is also presented.

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This paper represents new method to determine the optimum switching angles forSelective Harmonic Eliminated PWM (SHEPWM) inverter. Such switching angles aredefined by a set of nonlinear equations to be solved using the Resultant method. This isdone by first converting these equations that specify the harmonic elimination problem intoan equivalent set of polynomial equations. Then, using the mathematical theory ofResultants, all solutions to this equivalent problem can be found without the need for anyinitial guess. The complete solutions for unipolar SHEPWM switching pattern whichproduce the fundamental while not generating specifically chosen harmonics areinvestigated.

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One of the most important problems of power inverter is finding the desired harmonic frequency for representing the transmitted signal with low power consuming, so, to eliminate specific order harmonics, the switching angles must be calculated. There are many methods or techniques used to find optimum switching angles. In this research a new method is used which is a genetic algorithm (GA). GA used to find optimum switching angles which give a certain amplitude waveform with minimum harmonics frequency.

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The DC motor is an important part of an equipment in many industrial applications requiring variable speed and load characteristics due to its ease of controllability. Nowadays, there are lots of good-quality motor speed controllers on the market. However, their costs are relatively high. A speed controller with both low cost and good performance will be highly marketable, especially for small mobility applications. The current work allows controlling the speed of a DC motor in both forward and reversing direction, from fully off to fully on. It runs in switch mode so it is quite efficient. In this work, designing motor bi-directional DC control circuit using Pulse Width Modulation (PWM) based on an operational amplifier model LM324 is implemented. The proposed system offers many advantages such as simple structure, low cost, accurate, quite efficient, lightweight nature, small volume, and bi-directional speed control.

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Abstract Elimination of load harmonics can be achieved by either filtration of selected harmonics or the use of pulse-width modulation PWM technique. Many PWM techniques are developed, but the most commonly used in industrial applications is the SPWM technique where the distortion factor DF (one of the most important performance parameters of the quality and efficiency of a lot of the electronic devices) is significantly reduced. In this paper,the SPWM technique for harmonic elimination (HE)is implemented using 8051 microcontroller and the well known MATLAB software. The result is tested on a prototype inverter which was designed since 1998. This method is based on the analysis of Fourier series and Fourier coefficients of the required SPWM output voltage waveform. In this paper, the odd function technique with three and five pulses per half cycle to generate the required SPWM control signals is achieved. The basic flow chart of the control program, samples of the experimental results as well as an appendix illustrating the complete source code programs (INV1) and (INV2) in an assembly language of 8051 microcontroller are given. Key words :Harmonics elimination, PWM,Microcontroller, Inverter .

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There are many approaches and methods for changing the speed of DCmotors. One of these approaches is through the intensity of light. In thispaper, a microcontroller-based control circuit for adjusting the speed of aDC motor by means of interrupting the incident light is proposed andimplemented. The adopted technique in this circuit uses two lightdependent resistors as photo-sensors to detect the illumination of light byproducing a prescribed digital sequence to activate one of the input portsof an 8051 microcontroller. An assembly program stored in the on-chipprogram memory of the microcontroller generates the proper PWM signalat an output port based on the received sequence. This signal is suppliedto the driving circuit of the motor in order to run it with the relevant speed.The circuit has been implemented and tested successfully in thelaboratory.

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The study and simulation of a PI speed controller for small UAV or quadcopter motor is discussed in this research. The motor under consideration is MAXON 2260 215, which is a brushless DC motor that has permanent magnets on the rotating part and the stationary windings are connected so that the back electromotive force is trapezoidal. The motor utilizes a PI controller, which dominate the duty cycle of the PWM pulses applied on the switches of the inverter so that the motor can run at the required speed. A Chopper is used as a power converter and a proportional–integral as speed and current controller. The DC motor, which is being run individually, can be controlled on a wide range of operation up to the rated speed. The simulation is implemented and evaluated using PSIM software program under a wide range of speed, voltage and load torque inputs such as the rated speed and load torque, half the rated load torque and half speed since these tests are vital to test maneuver movement such as roll, pitch, yaw and throttle. The main objectives of this paper are; to understand the process of deriving the model for a propeller motor, to evaluate the stability and accuracy of the control loop for successful aviation, to apply a tuning plan on a closed loop system (PI) and to check the system procedure versus the given technical specifications.

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In this paper, we present a design and simulation of an efficient solar charge controller. This solar charge controller works with a PWM controlled DC-DC converter for battery charging. The system is implemented using an inexpensive PIC microcontroller and simulated by using Proteus ISIS ® Professional package and the simulation results for different PV cell and battery voltage levels.

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ABSTRACT :- In variable speed drive (VSD), it is desirable to reduce the harmonic effects, which causes current distortion and torque pulsation, besides, the harmonic power losses is an additional power losses that is introduced in the motor due to the presence of harmonic voltages.However, the problem of the high total harmonic current distortion (THD) still exists specially at low and medium speeds by using sub-optimal pulse width modulation (PWM) strategy. In the past to generate optimized PWM, is done by defining a general PWM in terms of a set of switching angles. Which result in a set of nonlinear equations in terms of the unknown switching angles. These equations are nonlinear as well as transcendental in nature. There is no efficient method that can be applied to solve such equations. The practical method of solving these equations is a trial and error process. Taking all the factors into account, a numerical technique can be applied to solve these set of nonlinear equations, but with some limitations. To overcome these limitations, Genetic algorithms (GAs) serves to search for optimal switching angles setting. In addition, the (THD) will be reduced, this lead to obtain the optimal PWM waveform and to simplify the practical implementation, and then improving the performance of the system output. GAs were employed as a search and optimization engine. Normally the tuning of the switching angles is a trail and error problem. In this paper, GAs provides a much simpler approach to off-line tuning of PWM switching angles than the rather complicated non-genetic optimization algorithms.Keywords:- Optimization, Genetic algorithm, PWM.

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Use of nonlinear loads, such as power converters, power sources,uninterruptible power supply (UPS) units, and arc devices like electric furnaces and fluorescent lamps and large adjustable speed motor drives, is expected to grow rapidly. All of these loads inject harmonic currents and reactive power into the power system. This paper presents a study and simulation of a three phase active power filter. A multilevel PWM inverter is used with current control technique. The proposed control system is very simple and therefore practicalimplementation of active power filters is available. The presented system is able to compensating current harmonics, reactive power and unbalance current of non linear loads. The total harmonic distortion is calculated for deferent load before and after filtering with deferent type of filter. A comparison is made between passive filter and active.The results have been obtained using software called PSIM, which hasdemonstrated its reliability for almost 10 years of simulations, which have been approved with real experimental results.

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