In this paper, speed control of Brushless DC (BLDC) motor drive under Direct Torque Control scheme with modified integrator for flux estimation is investigated using optimal controller. The modified integrator reduces the initial transient in flux linkage in first switching. Here the drive is operated in the constant torque region under the DTC scheme. The performance comparison between PI controller and optimal controller for speed control operation is evaluated. The electrical rotor speed and the back EMF in dq-reference frame is used for the torque estimation. The inverter DC-link voltage, speed and two line currents are measured for control the drive. The effectiveness of the proposed scheme is verified through extensive simulation under MA TLAB. Simulation results indicate better speed regulation of BLDC motor achieved using optimal controller.

In this paper, sensorless control of Brushless DC (BLDC) motor drive under Direct Torque Control scheme with modified integrator for flux estimation is investigated. The initial transient in flux linkage in first switching is reduced by the modified integrator. The drive is operated in the constant torque region under the DTC scheme. The sensorless control is achieved using PI controller and back EMF observer. Torque estimation is carried out by the observed electrical rotor speed and the back EMF in dq-reference frame. The inverter DC-link voltage and two line currents are measured for control. In DTC, two level hysteresis controllers are used for the torque and the flux control. The effectiveness of the introduced scheme is verified through extensive simulation under MATLAB. Simulation results indicates good speed response is achieved by the BLDC motor.

Boost converters plays a crucial role in high power applications. They can be combined with a voltage doubler to have a better performance. The low output of a renewable energy sources is boosted to suitable voltage using boost converter and voltage doubler circuit. The proposed converter eliminates the limitations of the conventional converters and they have the advantages like interleaving structure, nonisolated structure and soft switching scheme. Due to soft switched scheme, the current stress and voltage stress are eliminated and hence reduced switch losses. Interleaving structure guarantees equal current sharing and hence reduced component size. Non-isolated structure reduces the circuit size and complexity. A 10 W converter is designed and simulated. A closed loop control method is adopted to overcome the voltage drift problem.

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