Nazri Othman

Minimization of torque ripple utilizing by 3-L CHMI in DTC

A topology of multilevel inverter was to analysised and performed by using the 3-Level Cascaded-H Brigde-Multilevel Inverter (3L-CHMI) in DTC conventional hysteresis-based controller. This topology is similar with the conventional inverter, but it has more strategy for switching states. In this work, hysteresis comparator were used for flux and torque, with 12 sectors stator flux angle and will provide more selection of voltage vector. The basic concept of DTC system for torque and flux control consists of estimator of flux and torque and voltage vector. In conventional DTC, it has a several major issues which are largest torque ripple and unconstant switching frequency at low speed condition operation. So, the main purpose of this research is focusing more on how to reduce the output torque ripple at low speed operation condition. A simulation program had been developed to validate the results by using Matlab/Simulink.

High efficiency of switching strategy utilizing cascaded H-bridge multilevel inverter for high-performance DTC of induction machine

This paper presents about the control switching strategies of switching frequency by using the multilevel inverter. In previous topology inverter, 2-level inverter is commonly implemented by using direct torque control technique. However, this inverter has some major problem issues which occur due to the limitation of capability the semiconductor device. Basically, there exist two problems; Firstly, high torque ripple and secondly variable switching frequency. Both problems will affect the performance in controlling the AC drive. Besides that, the 2-level inverter is not capable to operate in high power application. Over the past decades, the multilevel topology was constructed to solve the problem in high application. In general, there are three types of multilevel inverters proposed, Firstly, Cascaded H-bridge Multilevel Inverter, secondly, Flying diode multilevel inverter and lastly, Neutral-Clamped multilevel inverter. Thus, in this paper, the Cascaded H-Bridge Multilevel Inverter (CHMI) is chosen to improve the switching frequency as well as a enhance response for motor drive. An algorithm is introduced to improve the torque ripple by using information of flux status.

Comparison performance of 3-Level and 5-Level Cascaded H-Bridge multilevel inverter of DTC of Induction Machine

Development of electrical vehicle (EV) and hybrid electrical vehicle (HEV) gives many opportunities and challenges in power electronic drive, especially in the development of traction motor drive that requires advanced power electronic inverter. Multilevel inverter was first proposed by Nabae in early 1980. The general structure of the multilevel inverter is to synthesis a sinusoidal voltage out of several levels of dc voltages. This paper shows comparison between the 3-Level Cascaded H-Bridge Multilevel Inverter and 5 -Level Cascaded H-Bridge Multilevel Inverter. It is found that by using 5-level Cascaded H-Bridge Multilevel Inverter (CHMI) can reduce torque and flux ripples compare to 3-Level CHMI and hence can improve DTC performances.

Modeling and simulation of torque hysteresis controller for brushless DC motor drives

This paper presents modeling and simulation of a torque hysteresis controller for brushless DC motors. Brushless DC (BLDC) motors can offer great advantageous compared to other machines used in industrial applications due to its compactness, high torque density, simpler controller and lower maintenance. At first the mathematical modeling of BLDC motor that is suitable to analyze the dynamic performance will be given. A method of torque hysteresis controller will be adapted to drive the motor such that the current (or torque) ripple can be restricted within the predefined band-gap. Moreover, a new current blocking strategy is proposed to prevent the current drained from DC supply when the torque demand is set to zero, that can prolong the capacity voltage of batteries. Some simulation results were carried out using MATLAB/Simulink to verify the proper modeling as well as functionality of the controller.

Improved performance of Direct Torque Control of induction machine utilizing 3-level Cascade H-Bridge Multilevel Inverter

This paper presents the advantages of using multilevel inverter which can provide greater number of voltage vector selection in minimizing the output torque ripple for Direct Torque Control (DTC) of induction machines. By employing a 3-level Cascaded H-Bridge Multilevel Inverter (CHMI), it provides 19 effective voltage vectors where each vector may give different effects on control performance for various operating conditions. This paper reports a simple switching strategy based on the hysteresis controllers and lookup table for DTC utilizing a 3-level CHMI. The torque hysteresis controller with 7-level of hysteresis band is introduced to determine the most appropriate voltage vectors which inherently suitable for different motor operating conditions. It can be shown that the selection of the proposed voltage vectors using multilevel inverter has better DTC performances in terms of torque ripple and quality of output waveforms (i.e. THD) as compared to the DTC with the conventional 2-level inverter.

Design and Development of Low Cost Certified Green Building for Non Residential Existing Building (NREB)

The Green Building Index (GBI) is one of rating tool which are provides a prospect for building developers and owners for designing and constructing a green and sustainable buildings. The proposed low cost GBI buildings provide many advantages such as energy savings, water savings, a healthier indoor environment, and better connectivity to public transport. Besides, adoption of recycling and greenery for the projects and can reduce the impact on the environment. However, the implementation to certify as Green Building Index has a lot of concerns such as cost constraint, know how constraints and etc. Therefore, in this paper, the design and development of low cost certified green building by fulfilling the Green Building Index (GBI) is proposed in order to ease the development of green building to have better life for human and environment in this world in term of energy efficiency performances.

Electric Vehicle Development and Prediction of Battery Consumption Based on a Journey Profile

The lack of internal combustion engine (ICE) for electric vehicle (EV) makes it solely dependable on battery supply. Due to this, the prediction of battery consumption becomes crucial to determine the accurate driving range before the car needs to be re-charged. The developed prediction model can also be applied as simulation tool and help in reducing the length and the cost of the EV design process. This paper presents the prediction of battery power requirement for a small re-engineered EV converted from a commercial ICE car by using vehicle dynamic mathematical equations. The prediction is performed based on multiple journey profile that gathered before the actual test. The development of re-engineered EV is also presented, along with the experimental result of an actual drive test on a racing circuit to validate the prediction model.

Direct self control (DSC) of induction machine utilizing 3-level cascade H-bridge multilevel inverter

This paper presents a new 3-level direct self-control (DSC) scheme for induction motor drive by selecting proper voltage vector for different speed operational. In conventional DTC two different voltage vectors are assigned to vary flux for low speed, medium speed and high speed motor operational. This paper proposed a scheme where only a single voltage vector is applied during low speed, medium speed and high speed motor operating condition, thus resulting hexagonal flux locus. The significant of the proposed method is new scheme improve the torque capabilities and able to achieve fastest torque dynamic performances during large torque demand. A comparison has been carried out between the conventional schemes and proposed method by using the Simulink\MATLAB environment.

Digital implementation of direct torque control of induction machines

This paper presents a digital implementation of Direct Torque Control (DTC) for three-phase induction machine using eZdspF28335. It can be shown that the execution of DTC algorithm can be optimized by applying IQ-Math blocks which are available in MATLAB software. Applying this approach, the complex digital calculation for all mathematic operations such as multiplication, division, subtraction and etc., can be simplified and hence calculate at faster rate. It is also emphasized that the selection of Q-point that represents the fraction length of data should be appropriate in order to achieve high-degree of computational accuracy. The DTC algorithm based IQ-Math blocks was simulated and implement in real practice using eZdsp F28335 to verify its feasibility and effectiveness.

Investigation of model parameter variation for tension control of a multi motor wire winding system

Tension is the force required to pull the wire against the accumulation of all resistance, forces and loads. Tension is one of the important controlled parameters in winding process in order to determine the quality of the product. Winding process in electric discharge machine (EDM) wire manufacturing is the last process before the product is packed and sent to customers. In EDM wire manufacturing process, incorrect tension will result in wire winding failure and wire straightness failure. Since it is the last process in EDM wire manufacturing, it is needed to ensure that there is no reject product contributed in this process. The increase of the pendulum dancer fluctuation and deviation angle when the winding diameter gets bigger especially when it is in high speed will course winding tension problem. This project mainly describes about the modelling of the system and the variation parameters that affects the system performance. The system performance is validated by changing the value of radius of winder.