Applied Mechanics and Materials Vol. 793

Abstract: The investigation of the direct current (dc) bias effect on single phase power transformer through their harmonics performance is present in this paper. The experimental study is done by the dc bias current injected simultaneously with alternating current (ac) source to primary winding of transformer. The input ac voltage to primary winding is maintained constant during investigation and the dc currents increased gradually. Compare to pure ac power applied, the results show that the waveforms distorted when the dc bias exist. The pulsated waveforms are pushed to half cycle in which the bias current is in the same direction as magnetizing current (unsymmetrical pulsated) and even harmonics are significant.

Abstract: This paper deals with an elimination of lower order harmonics in the seven - level cascaded inverters. The main objective of selective harmonic elimination pulse width modulation strategy is eliminating lower order harmonic by solving nonlinear equations, while the fundamental component is satisfied. In this paper, the Particle Swarm Optimization (PSO) is applied to a seven-level inverter for solving the nonlinear equation. With the proposed approach, the required switching angles are computed efficiently by PSO algorithm. Lower order harmonics up to the 7^th are eliminated. Simulation results verify the proposed method.

Abstract: Switched mode DC-DC converters are electronic circuits which convert a voltage from one level to a higher or lower level voltage. This paper presents a new solution approach to controller and observer controller of DC-DC Buck converter. The designs in this paper of DC-DC Buck converter is input voltage 20V step down to 12V output voltage. For control the system simulation investigation into development of controller and observer controller using MATLAB Simulink® software. The simulation develops of the controller and observer controller with mathematical model of DC-DC Buck converter. This paper also providing LQR controller to compare the performance of the system. Finally, the performance output voltage of DC-DC Buck converter is analyzed in terms of time response, overshoot and steady state error.

Abstract: Modular structured multilevel inverter is very useful for electrical application especially in high power and high voltage applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a new mathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM) by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Phase opposition disposition (POD). A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result.

Abstract: This research focused on the effect of harmonic to the performance of current transformer (CT) operates under harmonic conditions. Due to the increasing of harmonic in power system, the CT did not perform well. The CT may saturates due to the presence of voltage and current harmonics. In this project, a laboratory test was conducted to investigate and analyze the influence of harmonics to the CT performance. This CT has been test with different Total Harmonic Distortion Current (THD_i) at primary side and constant primary current. The experiment result shows the secondary current CT errors will increases when THD_i increases.

Abstract: This paper proposes a new regular sampled pulse width modulation (PWM) for three-phase current source inverters. The theoretical basis of the proposed modulation strategy is described, including dwell time calculations and switching sequence selection. This strategy is well suited for digital implementation, and enjoys all the flexibilities and degree of freedoms as in space vector modulation. In addition, it ensures a minimum number of switching transitions per fundamental cycle, unlike other PWM methods. It is therefore promising for high-power medium-voltage applications. The validity of the proposed modulation strategy has been confirmed using simulation and experimentation. To furthermore substantiate the superiority of the proposed modulation strategy against other PWM methods, its performance is compared to sinusoidal PWM, selective harmonic elimination, and space vector modulation.

Abstract: DC-DC converters are widely used in many applications such as power supplies, PV system, renewable energy systems and industrial applications. One of the main problems in dc-dc converters is the switching loss which affects efficiency and also the power density of the converter. To alleviate the switching loss problem this paper proposes novel soft switching PWM isolated dc-dc converters topology. The proposed full bridge dc-dc converter with active auxiliary circuit is designed and tested with full-bridge rectifier diode. The proposed converter is designed and evaluated in term of soft switching. In the proposed topology, the soft switching operations are achieved by charging and discharging process of the capacitor and additional switches. In the proposed topology, all the power switches operate under soft-switching conditions. Therefore, the overall switching loss of the power switches is greatly reduced. The output voltage of the converter is varied by PWM control. The effectiveness of the new converter topology is evaluated by experimental results of a laboratory scale down prototype. The obtained experimental results are found agreed with theoretical and soft switching is achieved.

Abstract: Energy meter monitoring with automatic tariff calculation is a project that can produce the output from energy meter to prepare a bill of electricity. Energy meter is a device that measure the amount of electric energy consumed. In Malaysia, the meter of Tenaga Nasional Berhad (TNB) travels for a long distance and take the reading manually to prepare the bill by visiting inside each of consumer house. This is high dependent on human forces. Sometimes the absence of consumer during billing process visiting make difficult to the meter reader to get the reader. Moreover many consumers are not satisfied with the estimate bills which are calculated based on average consumption. Soaring bill by estimate bills of electricity which consumer have to pay extra for the electricity billing. By using microcontroller and radio frequency transmitter for remote monitoring, the meter reader do not have to travel anymore. Global System for Mobile (GSM) uses to transmit and receive data from energy meter. The output which is calculated bill will be shown at Liquid Crystal Display (LCD) after apply the program coding in the microcontroller.

Abstract: This paper compares the performance of UPFC damping controller (, and ) to damp Low Frequency Oscillations (LFO) in power system equipped with UPFC based on Fuzzy Logic Power System Stabilizer (UPFC based FLPSS). The power system model was developed using linearized model of Phillips-Heffron Single Machine Infinite Bus (SMIB) and simulated in Matlab Simulink. The ability of each controller to damp LFO present in the rotor speed was monitored when the system being perturbed by small disturbances. The results obtained shown that UPFC controller had better performance to damp LFO compared to the other UPFC damping controllers as it had the lowest overshoot and less settling time.

Abstract: Increasing demand for large-scale power delivery with high reliability and quality necessitates the use of multiple distributed energy resources to be connected in parallel; for example, parallel inverters operation. Proper operation of parallel inverters requires sophisticated control techniques and many have been proposed and continue to evolve. This paper depicts the droop control techniques for the parallel inverter systems. The recent improvements and variants of this control technique are presented