This paper proposes a gain scheduled control technique using time-delay for the nonlinear system with plant uncertainties and unexpected disturbances. The time delay-based gain scheduled control depends on a direct estimation of a function representing the effect of uncertainties. The information from the estimation is used to cancel the unknown dynamics and the unexpected disturbances simultaneously. The proposed estimation scheme with a finite convergence time is formulated in order to estimate the unknown scheduling variable variation. In other words, the time delay-based gain scheduled control uses the past observation of the system's response and the control input to directly modify the control actions rather than to adjust the controller gains or to identify system parameters. It has a simple structure so as to minimize the computational burden. The benefits of this proposed scheme are demonstrated in the simulation of an electromagnetic suspension system with plant uncertainties and external disturbances, and the proposed controller is compared with the conventional state feedback controller.

This paper deals with the electromagnetic field analysis of slotless brushless permanent magnet machines with three different magnetization patterns such as Halbach, parallel and radial magnetization. The magnetization modeling of Halbach, parallel and radial magnetization is performed analytically. And then, analytical solutions for open-circuit field distributions, armature reaction field distributions, flux linkages due to PMs and stator windings, torque, back-emf and inductance are derived in terms of magnetic vector potential and two-dimensional (2-d) polar coordinate systems. The analytical results are validated extensively by finite element (FE) analyses. The magnet volume required in order to produce identical flux density is compared with each magnetization. Finally, analytical solutions and derivation procedures of those presented in this paper can be applied to slotless and slotted brushless permanent magnet AC and DC machines.

Magnetization loss of high temperature superconductoring BSCCO tape and YBCO coated conductor(YBCO CC) is most important issue in the development of superconducting power devices. In this paper, the measured results of magnetization losses in BSCCO tape and YBCO CC are presented and compared with each other. Measurements of magnetization losses are performed under various angles of external magnetic field to consider the anisotropic characteristics of YBCO CC. Also, we present the compared results of magnetization losses measured at arbitrary directional magnetic fields and analyzed with perpendicular magnetic field components of those. The results show that magnetization loss of YBCO CC agree well with the analyzed value by it's perpendicular magnetic field component, but BSCCO tape is not.

In this paper, a low loss magnetic levitation(Maglev) system is suggested and tested. The suggested Maglev system includes four hybrid magnets which consist of permanent magnet and coil. In the steady state, the levitated module system can be supported by attraction force generated by permanent magnet. The coil current controls only dynamic loads due to external disturbances. The module systems are designed by using finite element method(FEM) software tools such as MAXWELL and ANSYS. Also, digital control systems are designed to keep the magnet airgap at a constant value. The control systems include a VME(versa module europa)-based CPU(central processing unit) board, AD(analog to digital) board, PWM(pulse width modulation) board, 4-quadrant chopper, and sensors. In order to estimate the vertical velocity of the magnet, we use second order state observer with acceleration and gap signals as input and output signals, respectively. The characteristics of the suggested low loss Maglev system are demonstrated by experimental results showing coil current of 0A in the steady state of 3m airgap and performance specifications are satisfied for reference gap and force disturbance.

This paper presents a novel single-stage high-power-factor electronic ballast for fluorescent lamps operating in critical conduction mode. The proposed topology is based on integration of boost converter as power factor corrector(PFC) and a half-bridge high frequency parallel resonant inverter into a single stage. The input stage of the boost converter is operating in critical conduction mode for positive and negative half cycle voltage respectively at line frequency(60Hz). So that a boost converter makes the line current follow naturally the sinusoidal line voltage waveform. The simulated and experimental results for 100W fluorescent lamps operating at 42kHz switching frequency and 220V line voltage have been obtained. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, fluorescent lamp and DC-DC converter etc.

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

We considered of the buck and half bridge series DC-DC converter. It has good applications in areas with low voltage/high current, wide input voltage. The buck converter ratings and the half bridge converter ratings are $36\~72V$ input and 22V/5A output, $19\~24V$ input and 3.3V/30A output, respectively. Developed the buck and half Bridge series DC-DC converter ratings are of $36\~72V$ input and 3.3V/30A output. The buck converter is operated with zero voltage switching process to reduce the switching losses. The $80.1\%\~97.6\%$ of the efficiency is measured at $18.4{\mu}H$ output filter inductance of buck converter. In the half bridge converter, the $86\%\~96.4\%$ efficiency is measured at 150kHz switching frequency with PQI core. In the case of synchronized the buck and half bridge DC-DC converter, the measured efficiency is higher than that of the unsynchronized converter. In the synchronized converter, the maximum efficiency is measured up to $92.3\%$ with PQI core at 150kHz. 7A output.

This paper is given a full detail of mathematical analyses of input current and output voltage for a novel active type power factor correction (PFC) converter. These are compared with harmonics components of input current for a conventional PFC converter. The proposed PFC converter is constructed in using a new loss-less snubber circuit to achieve a soft switching of control device. Also the proposed converter for discontinuous conduction mode (DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity and the control method is simple. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of conventional PFC converter. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

This paper proposes a new anti-windup strategy to suppress integrator windup for PI speed controller and to be implemented on the existing system with minimal modification. When the speed control mode is changed from P controller to PI controller. an appropriate initial value for integrator is assigned. This value restricts overshoot and high settling time. Also, the proposed method guarantees the designed performance independent on operating conditions, i.e. different set-point change and load torque. Simulation and experimental results for PMSM speed controller have shown its superior performance compared with the conditional integration and tracking back calculation.