Swamidoss Sathiakumar

Project-Based Lab Teaching for Power Electronics and Drives

Project-based learning motivates students to learn actively, so it has been widely applied to many engineering subjects. However, the applications of this approach are limited in electric power courses because of the hazards associated with high voltage or mains voltage (240 V in Australia). This paper presents a project designed for a power electronics and drives course. In this project, students use a programmable intelligent computer (PIC) microcontroller and an H-bridge to design a control system for a real practical application, such as a washing machine, tram, or electric lift. Students gain hands-on experience, and also improve their skill in product development, self-directed learning, teamwork, and project management. Practical projects increase the challenge for students and, hence, their interest level. The project includes both hardware and software. Each part of the project and the student assessment are described here.

Microprocessor-based random PWM schemes for DC-AC power conversion

This paper compares and evaluates two classes of microprocessor-based random PWM (RPWM) real-time generation schemes for DC-AC power conversion. The practical performance of the RPWM schemes based on mathematical and logical approaches are examined. The proposed schemes exhibit excellent EMC and harmonic content with all low and high order harmonics suppressed, and are suitable for both MOSFET and IGBT inverters. >

Novel random PWM schemes with weighted switching decision

A new random pulse-width modulation (RPWM) scheme, which includes a weighted decision switching process, has been developed and tested. The switching strategy can be applied to the entire range of the modulation index. The scheme combines the advantages of the deterministic nature of the standard pulse-width modulation (PWM) schemes, and the nondeterministic spread-spectral characteristic of RPWM schemes. Test results have confirmed the improved spectral performance of the proposed schemes over a standard RPWM scheme at both low- and high-modulation indexes.

Improved spectral performance of random PWM schemes with weighted switching decision

The authors present a statistical approach to the analysis of random pulsewidth modulation (RPWM) methods which generate PWM signals by comparing a reference modulating function with random numbers or signals. Such an approach is used to analyze and optimize a new weighted RPWM (WRPWM) method and also a standard trapezoidal RPWM method. The WRPWM scheme combines the advantages of the nondeterministic and deterministic PWM methods by adding some deterministic nature into the nondeterministic RPWM method. Both theoretical and experimental results confirm that the optimized WRPWM method has better spectral performance over the standard RPWM schemes and has attractive features such as the potential of third-harmonic boosting, reduced acoustic noise, and minimal low-order harmonics under an overmodulation condition for electronic drive applications.

Noise analysis of DC-AC random PWM schemes

Random pulsewidth modulation (RPWM) techniques for DC-AC power converters usually work well with high-sampling frequency. When RPWM schemes are implemented in digital signal processors (DSPs), the sampling frequency is limited by the speed of the processors. This paper analyzes the noise spectrum of various DSP-implemented RPWM techniques using a statistical approach. The relationship of the noise components and the sampling frequency for both the standard RPWM and the weighted RPWM methods is generalized. The dependency of the noise characteristics on various factors is calculated theoretically and verified experimentally. The generalized noise theory for randomized PWM switching provides useful practical guidelines to the choice of sampling frequency.

A buck converter with simple maximum power point tracking for power electronics education on solar energy systems

This paper introduces a solar photovoltaic (PV) system suitable for undergraduate engineering education and training. The system consists of a buck converter using a simple maximum power point tracking (MPPT) method. Constant voltage control method is used for the approximate tracking and is implemented by analogue circuits. The circuit simplicity helps students to appreciate the benefit of MPPT in a short period of time without the need to work on complicated circuits and software coding. The proposed converter has been successfully implemented and served as a mini-project in a unit of study in power engineering studies.

Progressive change of chaotic PWM patterns in DC-AC random PWM schemes using weighted switching decision

This paper shows that random PWM (RPWM) schemes are in fact chaotic in nature and that the degree of chaos can be manipulated in order to improve the spectral performance of the RPWM method for DC-AC power conversion. An improved RPWM method which involves a weighted switching decision process for controlling the degree of chaos in RPWM is described. With an appropriately added deterministic nature, progressive change of such chaotic behaviour in RPWM schemes caused by the weighted process is demonstrated in a qualitative manner.

A simple high efficient torque control for the electric vehicle induction machine drives without a shaft encoder

A new torque control scheme without a shaft encoder is proposed. The scheme is based on considering the effect of temperature on rotor and stator resistances in the conventional induction machine equivalent circuit. Although the model is appropriate for both the steady state and transient conditions, the steady state behavior of the induction machine is analyzed in this paper. The induction machine is tested over more than two thousand operating points. The tests are carried out with a variable voltage and variable frequency voltage source in both motor and generator regions. Parameter values of the proposed model are identified and the model is used to estimate speed of the induction machine from its body temperature, input power, and input current. The required voltage and frequency to obtain maximum efficiency in a particular speed and command torque is calculated using the new model. This had been done for the whole torque and speed plane and the results are accumulated in a look up table. Under all circumstances, the induction machine temperature is taken into consideration. High efficiency and speed sensorless operation are two main advantageous of the proposed control technique.<<ETX>>

Flexible power consumption management in smart homes

The complexity of the power system keeps growing due to the penetration of alternative sources of electric energy such as solar plant and wind farm to meet the growing demand for electricity. In order to overcome the challenges due to complexity the power grid needs to be intelligent in all aspects. As the grid gets smarter, considerable efforts are being undertaken to make the houses and businesses smarter in consuming the electrical energy to minimize and level the electricity demand. It also necessitates that the conventional way to do modeling, control and energy management in all sectors needs to be improved or replaced by intelligent information processing techniques. We propose a policy based framework which allows intelligent and flexible energy management of home appliances in a smart home which is complex and dynamic in ways that save energy automatically. In this paper, we consider the challenges in formalizing the behavior of the appliances using states, and managing the energy consumption using policies. Our simulation results show that the proposed system can efficiently manage energy in a smart home in a user friendly way.

Comparative study of asynchronous and synchronous discrete delta modulation schemes for DC-AC power conversion

This paper presents a comparative study on the performance of two discrete delta modulation (DDM) schemes for DC-AC power conversion, namely the asynchronous (ADDM) scheme and the synchronous (SDDM) scheme. The ADDM scheme operates with asynchronous switching frequency and generates harmonics that spread over a wide range of frequency. The SDDM scheme operates with constant switching frequency and generates harmonics at well defined frequencies that correspond to the switching frequency and its multiples. Both schemes have been implemented successfully in a TMS320C25 processor. Experimental and computed results are presented. The advantages and disadvantages of both schemes are discussed.<<ETX>>