CPLD based controller for single phase inverters

The DC-AC converter, also known as inverter, converts DC power to AC power at desired output voltage and frequency. The DC power input to the inverter is obtained from an existing power supply. Nowadays inverters use high power switching transistors either IGBT's and/or MOSFETs. In addition, the voltage and frequency of the source can be adjustable. These single phase inverters and their operating principles are analyzed in detail. In this project, a full-bridge, single phase inverter that uses a digital Pulse Width Modulation (PWM) to control the power switches at 18 kHz was constructed. The concept of PWM with different strategies for inverters is described. A type of filter is used to improve the distortion in the output waveform. A design and implementation of PWM by using complex programmable logic device (CPLD) from Altera MaxPlus II is constructed and programmed. The involved software, hardware, and suitable algorithm to implement and generate the PWM are developed in details. To verify the significant of this single phase inverter, the output voltage will be tested with resistive load and inductive load

Improvement of Single-Switch Bridgeless PFC Cuk Converter for Circulating Current Elimination and Components Maximum Current Stress Reduction

This paper presents the improvement of a single-switch bridgeless PFC Cuk converter for circulating current elimination and maximum current stress reduction on components. Circulating current is eliminated by rearranging the position of input diodes thus the input diodes can block the returning path of current through the input inductors. The principle of circulating current elimination is also discussed in detail in this paper. A 100 W converter with an output voltage of -48 V has been tested to verify the principle. The results of the experimental hardware show the removal of the circulating current, the maximum current stress in input diodes is reduced from 8 A to 2.8 A and the maximum current stress in input capacitors also reduced from 11 A to 9.8 A

Microstrip Patch Antenna Design with Artificial Magnetic Conductor (AMC) at 26 GHz

Advancements in 5G wireless communication systems are expected to enhance the communication capability significantly to achieve the higher data rate by accommodating broad bandwidth. In this paper, three compact sizes of rectangular microstrip patch antennas that were made of RT5880, FR-4 and RO3003 substrates with 0.5 mm thickness and resonating at 26 GHz were proposed for the 5G applications. However, the antenna having narrow bandwidth and low gain which contributes to drawback of this microstrip patch antenna design and hence an Artificial Magnetic Conductor (AMC) was proposed to overcome this drawback. The 3.5 mm ´ 3.5 mm rectangular loop-slot AMC was designed at 26 GHz using FR-4 and it is found that integrating the AMC structure to the printed patch antenna significantly improved the gain and directivity of the antenna. With the help of AMC design, for RT5880 patch antenna, the gain increased for approximately 5% from 6.04 dBi to 6.34 dBi. Besides that, RO3003 patch antenna gain improved for 78.62% from 4.77 dBi to 8.52 dBi and for FR-4 patch antenna, the gain escalated from 2.24 dBi to 7.86 dBi (roughly 251% increment). As a conclusion, the directivity of RT5880 substrate solely decreased for approximately 13.75%. Meanwhile for RO3003 and FR-4 patch antennas, with the assist from AMC design, the directivity of antenna escalated for more than 120 % compared to without AMC and this proved that this design has potential to be used for 5G wireless networks and applications

Harnessing Trichoderma in Agriculture for Productivity and Sustainability

Increased agricultural activities driven by rising food demand have led to environmental problems mostly arising from the high levels of external inputs and resources that are required. Additionally, environmental changes, such as global warming, can lead to various biotic and abiotic stresses, which have negative impacts on crop production. Numerous solutions and agricultural strategies have been introduced to overcome these problems. One of the ways to improve plant production as well as to increase resistance towards biotic and abiotic stresses is by utilizing beneficial microbes as soil inoculants. A better understanding of the ability of Trichoderma to enhance crop production and the mechanisms that are involved are important for deriving maximum benefits from their exploitation. These versatile fungi hold great promise for the development of viable commercial products that can be used widely in agriculture for increasing crop productivity in a more sustainable way. Many previous reviews on Trichoderma have tended to focus on the mechanisms of Trichoderma in enhancing plant growth and yield. This current review discusses the sustainability aspect of using Trichoderma as plant growth regulators, the impact on plant growth and yield as well as their effects in regulating biotic and abiotic stresses

Improvement of Single-Switch Bridgeless PFC Cuk Converter for Circulating Current Elimination and Components Maximum Current Stress Reduction

This paper presents the improvement of a single-switch bridgeless PFC Cuk converter for circulating current elimination and maximum current stress reduction on components. Circulating current is eliminated by rearranging the position of input diodes thus the input diodes can block the returning path of current through the input inductors. The principle of circulating current elimination is also discussed in detail in this paper. A 100 W converter with an output voltage of -48 V has been tested to verify the principle. The results of the experimental hardware show the removal of the circulating current, the maximum current stress in input diodes is reduced from 8 A to 2.8 A and the maximum current stress in input capacitors also reduced from 11 A to 9.8 A