A NOVEL SINGLE STAGE AC–DC SELF-OSCILLATING SERIES-PARALLEL RESONANT CONVERTER

This project presents an improved self-sustained oscillating controller suitable for the single stage single phase power factor correction circuits. It has a modified active controller, which improves the performance from no-load up to full-load. The steady state characteristics are developed and a design example is given in detail. The proposed controller allows zero voltage switching at any loading condition with a reasonable power factor that satisfies the IEC 61000-3-2 standards together with a promising efficiency. Analytical, simulation, and experimental results verify the achievement the design specifications.

INTRODUCTION

CONVENTIONAL off-line power supplies usually include the full-bridge rectifier and large input filter capacitor at their input stages. They generate highly distorted input current waveforms with a large amount of harmonics. Recently, standards such as IEEE 519 and IEC 61000-3-2 impose a limit on the harmonic current drawn by pieces of equipments connected to an ac line in order to prevent the distortion of an ac line voltage. Therefore, the aimed ac–dc converter is the one that draws a pure sinusoidal current at unity power factor from the mains, also enjoys a precisely regulated output voltage without any ripple. The common operation for switching mode power supplies (SMPS) is to use two separate converter stages, an ac–dc conversion stage and another isolated dc–dc conversion stage, to convert the input ac mains voltage into an isolated and regulated dc voltage. A boost converter is typically used as the ac–dc conversion stage because it can perform power factor correction (PFC) by shaping the input current so that it is sinusoidal and in phase with the input voltage. The dc–dc conversion stage is usually a full-bridge converter for high power applications. 

In order to reduce the cost and complexity associated with operating two separate converter stages, converters that integrate the functions of PFC and isolated dc–dc conversion in a single stage PFC converter are preferable. Most conventional power factor correcting systems introduced so far employ pulse width modulation (PWM) techniques to achieve the features of the PFC converter. 

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SENSORLESS DIRECT TORQUE CONTROLLED DRIVE OF BRUSHLESS DC MOTOR BASED ON FUZZY LOGIC

INTRODUCTION
Permanent magnet brushless DC motor (BLDC) with trapezoidal back-EMF have been widely used in many field of variable-speed drives for their higher power/weight and higher efficiency. However, in practice, torque ripple may exist for the motor itself and feeding system. Particularly, torque ripple during the commutation period is one of the main drawbacks which deteriorate the performance of BLDC drives. To reducing torque ripple effectively, various torque control methods. In, a novel torque controller attenuating the undesired torque pulsation for BLDC with non-ideal trapezoidal back- EMF is presented, in which the torque is estimated from the product of the instantaneous back-EMF and current. However, the winding resistance was neglected and the back-EMF shape functions according to the rotor position are tested by offline, and set up at the look up table. 

For achieving instantaneous torque control and reducing the torque ripple, direct torque control (DTC) has been successfully extended to a three-phase BLDC drive operating in the 120 elec. Degrees conduction mode. DTC scheme was originally developed for induction machines drives which was first proposed by Takahashi and Depenbrock in the mid 1980s. Control of torque is exercised through control of the amplitude and angular position of the stator flux vector relative to the rotor flux vector. It is claimed that the electromagnetic torque and the amplitude of stator flux linkage can be controlled simultaneously. However, the control effect of the stator flux linkage is not good from the simulated and experimental result.  In this paper, a sensorless fuzzy direct torque controlled BLDC drives is proposed to reducing torque ripple in twophase conduction mode. The proposed scheme differs from the direct torque controlled BLDC drives in that the amplitude of stator flux linkage is not controlled since it is automatically determined by every 60 elec. degrees commutation. In the system, the torque error and flux linkage angle of BLDC were all properly fuzzified into several subsets to accurately select the voltage space vector in order to smooth the torque and quicken the torque response. The torque and rotor speed are derived from the back-EMFs, which are estimated from a designed state observer. Its effectiveness is validated by simulations. 

IMPLEMENTATION OF FUZZY BLDC-DTC SYSTEM
The block diagram of a sensorless BLDC drive with fuzzy DTC may be as shown in Fig.

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SPEED CONTROL OF BRUSHLESS DC MOTOR USING GENETIC ALGORITHM BASED FUZZY CONTROLLER

The brushless DC motor (BLDCM) is receiving wide attention for industrial applications because of their high torque density, high efficiency and small size. Conventional controllers suffer from uncertain parameters and the non-linear of the BLDCM. The fuzzy control has been focus in the field of the control of the BLDCM. However, a systematic method for designing and tuning the fuzzy logic controller is not developed yet. In this paper, an auto-tuning method for fuzzy logic controller based on the genetic algorithm (GA) is presented. And the scheme is applied into the BLDCM control. Two closed loops are constructed which is given below. The inner loop is current feed back which is to adjust the torque of the motor. The outer loop is the fuzzy logic controller whose control rules are optimized off-line and parameters are adjusted based on the genetic algorithm. 

BLDCM Servo System
Fig. I shows the block diagram of the configuration of fuzzy model control system for BLDCM. The inner loop of Fig. I limits the ultimate current and ensures the stability of the servo system. The outer loop is designed to improve the static and dynamic characteristics of the BLDCM servo system. In this paper, a fuzzy control is used to make the outer loop more stable. To make the fuzzy controller more robust, this paper presents the genetic algorithm to optimize the fuzzy rules, and auto-tuning the coefficient of the controller. 

Fig. II is the control configuration of the BLDCM servo system. The TMS320LF2407A DSP is used to generate the PWM and an IR2130 is used to drive the MOSFET. The A/D Unit is used to sample the current of the motor. The position signal of the rotor in gained by the Capture Unit of the DSP, and the speed value is calculated from the position information.

VIDEO DEMO