Aiman Zakwan Jidin

FPGA based high precision torque and flux estimator of direct torque control drives

This paper presents an improved FPGA-based torque and stator flux estimators for direct torque control (DTC) induction motor drives, which permit very fast calculations. The improvements are performed by 1) using twos complement fixed-point format approach to minimize calculation errors and the hardware resources usage in all operations, 2) calculating the discrete integration operation of stator flux using backward Euler approach, 3) modifying the non-restoring method to calculate complicated square root operation of stator flux, 4) introducing a new sector judgment method, and 5) reducing the sampling frequency down to 5μs. To avoid saturation due to DC offset present in the sensed currents, the LP Filter is applied. The simulation results of DTC model in MATLAB/Simulink, which performed double-precision calculations, are used as references to digital computations executed in FPGA implementation. The Hardware-in-the-loop (HIL) method is used to verify the minimal error between MATLAB/Simulink simulation and the experimental results, and thus the well functionality of the implemented estimators.

A simple strategy to solve complicated square root problem in DTC for FPGA implementation

This paper presents a digit-by-digit calculation method to calculate the complicated square root problem faced in implementing the direct torque control (DTC) of induction motor drives using Field Programmable Gate Arrays (FPGA). The main principle of the proposed method is based on a two-bit shifter and a subtractor-multiplexor operation that gives simpler implementation and faster calculation. The proposed strategy was successfully implemented on an FPGA device using unsigned 32 bit and 64-bit binary square root. The strategy can be easily expanded to larger number.

A wide-speed high torque capability utilizing overmodulation strategy for direct torque control of induction machines

This paper presents a simple overmodulation method employed in Direct Torque Control (DTC)-Constant Switching Frequency (CSF) controller of induction machines. The proposed overmodulation method is utilized to extend a constant torque region and hence produces high torque capability in field weakening region with six-step operation. It is shown that the overmodulation operation using the DTC-CSF scheme can be established by controlling the stator flux locus from circular to the hexagonal shape. This is achieved by modifying the flux error status produced from flux hysteresis controller, before it is being fed to the look-up table. The main benefit in the proposed strategy is its simplicity and it can be implemented in many electric drive applications to obtain maximum torque capability for a wider speed range operation.

Simulation of three-phase cascaded H-bridge Multilevel Inverter with THIPWM

This paper presents the simulation of a Three Phase Five Level Cascaded H-bridge Multilevel Inverter. Third Harmonics Injection Pulse Width Modulation (THIPWM) technique was employed through s-function approach in SIMULINK environment to minimize the complexity of circuit design. The advantages of THIPWM are revealed in term of voltage and current THD reduction compared to Sinusoidal Pulse Width Modulation (SPWM) in three phase system. Simulation results reveal that voltage and current THD of THIPWM improved as much as 36% and 28% respectively compared to SPWMs.

Optimizing the flux and torque estimator of DTC in FPGA by using low-area square root calculator

This paper presents an alternative to improve the implementation of the torque and flux estimator for the Direct Torque Control (DTC) of induction motor drives in Field Programmable Gate Array (FPGA). The square root architecture is optimized to have low hardware resources utilization, by reducing the number of logic elements used, and subsequently contributing to reducing the power consumption. This is achieved by sharing the common hardware and eliminating parallel computation in the square root calculator, which is implemented by using the non-restoring algorithm. The proposed strategy was successfully implemented in ALTERA Cyclone II FPGA and the functionality of the system was validated via functional simulations.

Microgeneration of electrical energy using piezoelectric from car movement

The paper discuss on the method and process of microgeneration of potential energy power produce by piezoelectric on vehicles. This microgeneration method of harvesting from the vibration of the car itself will be used in order to generate power and the piezoelectric expected capable of produce low voltage output. The piezoelectric generator will be used as the main component in the microgeneration design. The study involved on investigation of vibration from different point within the car and choosing the best point. The piezoelectric device is then mounted near the selected vibration source from the vehicle. The outcomes will be contributed by vibrations in the vehicle, thus vibrates and displacement to the piezoelectric device to produce electricity.