Abdul Halim Mohd Yatim

A new AC-DC converter using bridgeless SEPIC

A new bridgeless power factor correction circuit (PFC) based on single ended primary inductance converter (SEPIC) is proposed. The number of component conducted at each subinterval mode is reduced compared to the existing topologies. Analysis of the converter operated in discontinuous-conduction mode (DCM) is discussed. Experimental circuit for the proposed converter is developed with universal input voltage capability for 50V DC output voltage connected to 100W load. The simulation and experimental results are presented to show the performances of the proposed circuit.

Direct torque control of induction machines with constant switching frequency and improved stator flux estimation

Direct torque control (DTC) of induction machines is known to have a simple control structure yet has comparable performance to that of the field oriented control (FOC). To maintain this simple control structure while at the same time improving the performance of the DTC drive in terms of switching frequency and stator flux estimation, two simple techniques are proposed. The effectiveness of the proposed techniques are verified experimentally which is centered around a TMS320C31 digital signal processor.

A Novel Overmodulation and Field Weakening Strategy for Direct Torque Control of Induction Machines

This paper presents a new simple overmodulation strategy in direct torque control (DTC) of induction machines. The strategy increases the inverter voltage limit and therefore extends the constant torque region. The minor modification on the conventional flux weakening method is also introduced to improve the torque capability in the field weakening region and hence improving the operation over a wide speed range. These strategies are implemented with a DTC-constant switching frequency (CSF) based system. To perform the DTC-CSF in overmodulation mode, the flux error status is modified before it is being fed to the voltage vector selection table. With this proposed strategy, a single-mode overmodulation based on stator flux vector control with smooth PWM to six-step transition is developed. This strategy also proposes a dynamic overmodulation to obtain fast torque transient with six-step operation including the field weakening region. The proposed strategy has been verified through computer simulations and shown to improve the torque capability of DTC induction motor drives with a fast dynamic torque response.

Dynamic evolution control of interleaved boost dc-dc converter for Fuel Cell application

An electric vehicle powered by the fuel cells called Fuel Cell Electric Vehicles has higher efficiency and lower emissions compared with the internal combustion engine vehicles. In this application, a high power boost dc-dc converter is adopted to adjust the output voltage, current and power of fuel cell engine to meet the vehicle requirements. The major challenge of designing a boost converter for high power application is how to handle the high current at the input and high voltage at the output. In this paper an interleaved boost dc-dc converter is proposed for stepping-up the voltage on high power application. The controller of converter system was designed. A new approach for interleaved boost converter controller based on dynamic evolution control theory is presented. Performance of the interleaved boost converter with the proposed dynamic evolution controller is tested through simulation.

An isolated bridgeless AC-DC converter with high power factor

This paper introduce a new isolated bridgeless AC to DC converter with power factor correction capability. This power factor correction (PFC) circuit is capable to perform the AC to DC conversion without the diode bridge rectifier and able to obtain low output voltage which is more suitable to most applications. The detail small signal and steady state analysis of the converter operated in discontinuous conduction mode (DCM) are presented using the current injected equivalent circuit approach (CIECA). The dynamic and steady state response at the input current and output voltage are included to verify the converter capability as a PFC circuit.

Dynamic Evolution Controller for single phase inverter application

This paper proposes a new control method based on Dynamic Evolution Control for single phase inverter. A new approach for synthesis of inverter controller based on dynamic evolution control theory presented. In order to synthesize the converter controllers, this method uses a simple analysis of non-linear equation models of the converter. Synthesis of single phase inverter controller based on the proposed control method is discussed in detail. Performance of the proposed dynamic evolution control is verifying through simulation under step load condition. Simulation results show that the proposed techniques are suitable for controlling power inverter.

A simple PEM fuel cell emulator using electrical circuit model

This paper presents the development of a simple emulator for proton exchange membrane (PEM) fuel cell. This emulator is built based on the dynamic model of PEM fuel cells using electrical circuits. The electrical circuit model has been modeled in Matlab Simulink environments. The double-layer charging effect characteristic inside the fuel cell is included in the models. The steady-state and transient response of the model is investigated. Emulator performance is validated using experimental data from a 500-W commercial PEM fuel-cell stack. The emulator could be used in PEM fuel-cell control related studies.

A simple dynamic overmodulation strategy for fast torque control in DTC of induction machine with constant switching frequency controller

This paper presents a simple dynamic overmodulation method to obtain a quick dynamic torque response in Direct Torque Control with constant switching frequency (will be referred as DTC-CSF) induction machines. A fast dynamic torque control can be achieved by applying a voltage vector that produces the largest tangential flux component during the transient condition. To perform this, the flux error status produced from the flux hysteresis comparator is modified before it is being fed to the look-up table, during dynamic condition. The effects of different switching and operating condition on dynamic torque performance are presented. The main benefit of the proposed method is its simplicity since only minor modification is made to the basic DTC hysteresis-based structure.

Curve fitting technique for optimal pulsewidth modulation (PWM) online control of a voltage source inverter (VSI)

A curve fitting technique to allow online computation of switching angles based on the optimal PWM switching strategies is presented. Detailed description of the curve fitting technique as applied to the optimal PWM switching angles trajectories for a VSI particularly for AC power conditioner or UPS applications is provided in this paper. This includes some analysis on the accuracy of the calculations based on the curve fitting technique compared with the exact solutions. The approach taken to actually implement this technique on a practical system is also highlighted.

A DSP-based online optimal pulsewidth modulation (PWM) switching strategies for a modular structured multilevel (MSM) inverter

Implementation of a low switching frequency modulator for optimal pulsewidth modulation (PWM) switching strategies using Texas Instruments TMS320C31 digital signal processor (DSP) as the main processor for online control of a modular structured multilevel (MSM) inverter output is presented. This is made possible through a proposed curve fitting technique to allow for online computation of the optimal PWM switching angles. A detailed description on the online optimal PWM switching strategies is provided. The performance of the MSM inverter employing the control strategy based on simulation and experimental results are shown for comparison purposes.