Nattapon Chayopitak

Efficiency Improvement of Three-Phase Cascaded H-Bridge Multilevel Inverters for Photovoltaic Systems

Medium-scale photovoltaic (PV) systems using cascaded H-bridge multilevel inverters have a capability to perform individual maximum power point tracking (MPPT) for each PV panel or each small group of panels, resulting in minimization of both power losses from panel mismatch and effect of partial shading. They also provide high power quality, modularity, and possibility of eliminating dc-dc boost stage and line-frequency transformer. However, each PV panel in the system is subjected to a double-line-frequency voltage ripple at the dc-link which reduces the MPPT efficiency. This paper proposes a dc-link voltage ripple reduction by third-harmonic zero-sequence voltage injection for improving the MPPT efficiency. Moreover, a control method to achieve individual MPPT control of each inverter cell is also presented. The validity and effectiveness of the proposed methods were verified by computer simulation.

A design of switched reluctance motor and drive system for high performance electric motorcycle

Traction drive for electric motorcycle (EM) is one of the most promising applications for switched reluctance (SR) motor. A design of EM system, SR traction drive sub system and components is presented in this paper. A prototype has been manufactured and tested in test facilities as well as in several real road conditions. The prototype passed EMI/EMC and safety standards which make it possible to run fleet test in the near future.

Adaptive and repetitive controller for robotic manipulators with slowly updating scheme using B-spline shape function

This paper studies the real-time adaptive and repetitive control problem using the Desired Compensation Learning Law (DCLL) that has the advantage of robustness under the presence of unknown parameters with low memory requirement. The control structure of DCLL consists of a feedforward compensator that is designed by a linear combination of shape functions that is adaptable to parameter variations; hence the selection of appropriate shape functions plays an important role in the adaptive ability and accuracy of DCLL. In this study, the B-spline shape function is proposed to be used under the slowly updating scheme and the obtained results show that the robustness and accuracy of the tracking can be greatly improved even under payload variation and torque limits.

Electric motor based head controller for power wheelchairs with joy stick input

In this paper, a design of a head controller and an adapting unit for interfacing with a power wheelchair is presented. The proposed controller is based on a servo mechanism of stepper motors, which provide motion in the x- and y-axis to actuate a modified joystick-controlled power wheelchair. The technical design aspects of the proposed head controller, adapting unit as well as the microcontroller implementation are discussed.

Torque ripple reduction in brushless DC motor using repetitive control

Brushless DC (BLDC) motors have been widely used in industry. However, one of the main drawbacks of using BLDC motors is the undesirable torque ripple. The torque ripple can cause mechanical vibration, acoustic noise and bearing damage that reduces the lifetime of the machine. This paper proposes a simple repetitive control scheme to attenuate torque ripple of BLDC motors. In this method, the ripple is considered as an undesirable repeated signal that will be minimized by the repetitive control scheme. The control input used in the proposed method is controlled transistors switching using space vector pulse width modulation technique. Simulation results show the proposed repetitive control technique results in the apparent reduction of the torque ripple when compared to a conventional control scheme.