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Articles by S.M. Bashi
Total Records ( 6 ) for S.M. Bashi
  S.M. Bashi , N. Mariun , N.F. Mailah and S. Alhalali
  This study deals with the simulation and development of a single phase multilevel inverter. The aim of the study is to investigate the performance and features of transformer and transformer-less multilevel inverters. In order to generate sinusoidal wave with minimum THD, harmonic elimination method has been used to calculate conducting angle of each H-bridge. This generates the output waveform with certain voltage and low THD. PIC microcontroller has been used to generate the signals required to operate the system. The proposed circuit was simulated using Pspice/Orcad and the results were compared with the hardware experimental results and a good agreement has been found between simulation and laboratory results.
  S.M. Bashi , N. Mariun , S.B. Noor and H.S. Athab
  A harmonic injection technique, which reduces the line frequency harmonics of the single switch three-phase boost rectifier, has been implemented. In this method, a periodic voltage is injected in the control circuit to vary the duty cycle of the rectifier switch within a line cycle so that the fifth-order harmonic of the input current is reduced to meet the total harmonic distortion (THD) requirement. Since the injected voltage signal, which is proportional to the inverted ac component of the rectified three-phase line-to-line input voltages is employed; the injected duty cycle variations are naturally synchronized with the three-phase line-to-neutral input voltages.
  S.M. Bashi
  Power quality is one of the most talked about topics these days. Both the power utilities and customers are quite concern with the quality of the power supply, whether it be the power generated by the power utilities or the power consumed by the customers respectively. They need these supplies to be at its optimum value so that the cost is efficient; otherwise problems such as over voltage, under voltage, voltage swell, voltage sag, noise and harmonic caused by the disturbances in power supply could be disastrous. Several methods have been suggested and applied as the solution to these problems. One of the methods is by employing on-load power transformer with tap changer, where the output voltage of the power transformer remains constant irrespectively to the input voltage or variation of the load. The existing mechanical on-load tap changing power transformer has few disadvantages, as it is slower, produces arching each time the tap setting is changed and needs regular maintenance. With the emergence of high power semiconductor devices such as triac, problems associated with the mechanical on-load tap changing power transformer have been properly rectified. In this study, a small prototype consisting of triacs as the switching devices and microcontroller as the triggering circuit has been constructed. The results obtained from this study show that the prototype has a faster time response of approximately 0.4s for the circuit to react to any load changes, produces no arching problems as it has no mechanical contact and requires no maintenance. The system has been tested for reliability and proven to be reliable in maintaining the output voltage of the system.
  S.M. Bashi , A.U.M. Al-Abulaziz and N.F. Mailah
  The harmonics are generated by the switching operation of large power converters, such as Static Compensator (STATCOM), Static Reactive Power Controller (SVC) and UPFC. These harmonics may cover a wide range of frequencies and it can cause problems of interference with communication systems. Power Line Carrier (PLC) system is one of the systems used in transmission of signals for Tele-potations, Tele-tripping, Tele-control and speech communications. The Signal to Noise Ratio (SNR) of the PLC is based on the noise level at the input of the carrier receiver. These effects of harmonics result in overheating, extra losses in electric machines and capacitors; and over voltage due to excited resonance in the power system. The main source of disturbances resulting from harmonics has been proved to be from a high power converter. This problem becomes more complicated when harmonics are originating in many single source. These harmonics can be propagated throughout the entire interconnected power network. The interference due to large power converter will be superimposed on the background noise at lower levels causing it to reduce the SNR to an unacceptable value. This study deals with the analysis of the waveform of the converters and the methods used to reduce the noise imposed on PLC communication signal.
  N.F. Mailah , S.M. Bashi , N. Mariun and I. Aris
  This work deals with the study and simulation of Unified Power Flow Control (UPFC) at its normal and abnormal conditions. The systems are modeled and simulated using MATLAB software. Shunt inverter or Static Compensator (STATCOM) is modeled as a 3-phase multipulse converter and the series inverter or SSSC has been constructed as a 3-phase, 3-level multilevel converter. Faults are set to the system to observe the operation of STATCOM and phase shift, φ of the SSSC is varied to observe the operation of SSSC. Simulations are carried out and the results obtained agreed with the theory of operation of the UPFC.
  M. Hedayati , N. Mariun , H. Hizam and S.M. Bashi
  Shunt FACTS devices are prevalent in industrial application of induction motors. These equipments are effective to compensate disturbances and increase motor speeding up. In this study an assessment study between two different shunt FACTS (SVC and STATCOM) installed on terminals of motor is done. A conventional PI controller is used to control the thyristor firing angle of SVC or phase angle of STATCOM. A pole placement method is applied to specify the perfect gain settings of the controllers. The results of simulations display that STATCOM has better response over SVC for improving dynamic behavior of induction motor under ideal supply conditions. Power quality problem that influence the dynamic behavior of induction motor, include non ideal conditions such as harmonics, interruptions, voltage unbalance and voltage sags. Whereas voltage sags is one of the main cause of disturbances in distribution systems, the performances of the induction motor under symmetrical and unsymmetrical voltage sags are investigated in this study. The results prove that STATCOM is more effectual than SVC for reduction of transients and refinement the voltage profile.
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