Hanifah Jambari

A single phase hybrid active power filter using unified constant-frequency integration control

This paper proposes a single-phase hybrid active power filtering using Unified Constant-Frequency Integration (UCFI) as the controller. The proposed topology interconnects the passive filter with shunt active power filter through point of common coupling (PCC). The topology chosen for active power filtering is a cascaded H-bridge multilevel inverter (CHMI) which offers wide range of advantages over basic configuration of active power filter. The hybrid topology provides advantages over non-hybrid active filter which is able to compensate both higher and lower order of harmonics. This paper describes the multilevel inverter circuit topology, passive filter design to be incorporated with the shunt active power filter (APF) and the implementation of UCFI control scheme. The system is verified using MATLAB/Simulink. Comparison analysis shows the performance evaluation of each compensation circuit from basic H-bridge inverter circuit to non-hybrid multilevel inverter circuit and the proposed hybrid configuration. Simulation results shows that the total harmonic distortion of the source current have been reduce abruptly from 125.53% to 3.47% after compensation using the proposed hybrid configuration.

Simulation of Cascaded H-Bridge Multilevel Inverter for liquid food sterilization with various distance of the electrodes gap

This paper presents the simulation results of the Cascaded H-Bridge Multilevel Inverter (CHMI) with various distance of the electrodes gap in liquid food sterilization using pulsed electric field (PEF). The utilization of the difference gap between the electrodes allow the system to reduce the applied voltage of the HVDC power supply, while fulfilling the requirements for effective liquid food sterilization. Thus it can reduce power consumption and will reduce cost. In this paper, the CHMI circuit has been simulated using MATLAB/Simulink and the distance of the electrodes gap has been simulated using Quickfield simulation software. Peak output voltage 1.2 kV, 2.4 kV and 6 kV with gap distance 0.1 cm, 0.2 cm and 0.5 cm respectively has been obtained in which the values can produce electric field strength of up to 12 kV/cm. All of the specifications meet the requirements for liquid food sterilization, particularly inactivate saccharomyces cerevisiae spoilage microorganisms in pineapple juice.

Cascaded H-bridge multilevel inverter based pulsed power supply for liquid food sterilization

This paper proposes a Cascaded H-bridge Multilevel Inverter (CHMI) based pulsed power supply for the sterilization of liquid foods using Pulsed Electric Field (PEF). The utilization of a CHMI allows the system to reach high voltage without the use of transformers while fulfilling the pulse requirements for effective liquid food sterilization. By using the CHMI topology, no extra clamping diodes or voltage balancing capacitor is needed. In this work, the proposed CHMI circuit operation is simulated using MATLAB/Simulink where unipolar and bipolar square wave pulses with pulse width range of 1 µs to 1 ms are generated. A peak output voltage of 6 kV and peak output power of 3.6 kW have been obtained with both values meeting the pulse specifications for liquid food sterilization applications.

Implementation of cascaded H-bridge multilevel inverter for liquid food sterilization using pulsed electric field

This paper presents on evaluating a performance of Cascaded H-bridge Multilevel Inverter (CHMI) pulsed power supply, which can produce high-voltage output pulses and electric field strength for effective inactivation of microbes in liquid food sterilization process. The unique feature of the CHMI allows the system to produce bipolar square wave pulses with less power consumption and high stability compared to an exponential decay pulse (EDP) and oscillatory decay pulse (ODP) in liquid food sterilization. The CHMI pulsed power supply can achieving high output voltage without using a transformer while fulfilling the requirements specification for sterilizing an identified liquid food. This in turn can reduce the power losses due to omission of winding coil as well as reduce cost. The experimental results on the 7-level CHMI indicate that, output voltage and electric field strength up of 2.0 kVp-p and 10 kV/cm respectively have been produced with both values meeting the pulse specifications for liquid food sterilization applications particularly for inactivation of Saccharomyces cerevisiae in orange juice.

IDENTIFICATION OF EMPLOYABILITY SKILLS AMONG TECHNICAL AND VOCATIONAL EDUCATION MASTER STUDENT IN UNIVERSITY TUN HUSSEIN ONN MALAYSIA (UTHM): A CASE STUDY

The factor that is most commonly discussed related to employability rate among masters’ graduates is the lack of employability skills, set by the employers apart of the academic qualifications. This study is conducted to identify the level of employability skills among final year student of Master in Technical and Vocational Education, Universiti Tun Hussein Onn Malaysia (UTHM) and to identify the employability skills set by the employers. Quantitative research design using survey opted where the samples focus on 108 masters’ students and 42 employers selected randomly among educational institutions. The questionnaires were distributed to the respondents using simple random sampling and the data was analysed using descriptive statistical and statistical inference. The results recorded average level of employability skills among the students, with the mean score of 3.025. It can be concluded that the lecturers play an important role to enhance the students’ employability skills. However, the students must be responsible for enhancing their employability skills so that their employability rate could be enhanced to grab the working opportunity upon graduation.

EFFECTIVENESS OF PROJECT-BASED LEARNING (PJBL) IN IMPROVING KNOWLEDGE RETENTION AMONG TECHNICAL AND VOCATIONAL STUDENTS

TVET in Malaysia is becoming more popular as government started a new transformation on technical and vocational education. The establishment of Vocational College (KV) changes the requirements needed for new teachers as KV only seek new teachers with high level of skills and knowledge. Nevertheless, most of the teacher trainees voiced out their concerns as they unable to retain knowledge that they have learned during their study in university. Thus, this study is conducted in order to seek the effectiveness of PjBL in improving knowledge retention among technical and vocational students, who also teachers-to-be for KV. This study was conducted qualitatively by using experimental research design, which using two groups of students. The students from both groups are interviewed in order to seek the effectiveness of PjBL. The findings show that PjBL is able to improve the students’ knowledge retention as they able to apply and practice their knowledge throughout the semester. It is imperative for educators to provide best teaching practice for students in order to improve their knowledge retention.

Pulsed electric field by Cascaded H-bridge multilevel inverter for liquid food sterilization

This paper focuses on evaluating the effectiveness of a Cascaded H-bridge Multilevel Inverter (CHMI) based pulsed power supply for liquid food sterilization using pulsed electric field (PEF). The utilization of the CHMI allows the system to produce PEF with high stability, less heat and power consumption if compared to the conventional methods such as pulsed forming network (PFN) or transmission line techniques. The CHMI pulsed power supply can attaining high output voltage without using a transformer to meet specification necessities for sterilizing liquid food. By using the CHMI, the power loses due to omission of winding coil can be reduced. A MATLAB/Simulink software has been used to simulate the effectiveness of a 5-level CHMI circuit in order to generate PEF output pulses with pulse width 1 ms and at constant frequency of a 50 Hz. The simulation and experimental results indicate that, an output voltage up to 4.52 kV p-p and maximum output power of 348 W have been generate with the values fulfil the pulse requirements for liquid food sterilization applications. Most importantly, the CHMI has been operated with less power consumption if compared with conventional method that can prove to be beneficial in terms of lowering its cost and size particularly for industrial application to inactivate various type of microbial.