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Title: Performance improvement of a medium-voltage series-connected twelve-pulse current source converter
Author: Hamad, Mostafa Saad Abdallah
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2009
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This thesis investigates the performance of a medium-voltage (MV) 12-pulse controlled rectifier in conjunction with a tapped front-end transformer used with a shunt active power filter (APF) for ac-side compensation. A series APF based on a magnetic amplifier is used for dc-side compensation. The series APF is coupled with the shunt APF to a common controlled dc-bus. forming an ac/dc unified power controller. An operating power locus is introduced that combines symmetrical and asymmetrical firing of the two constituent 6-pulse converters. It provides the ' lowest' total harmonic distortion (THO) with a maximum reactive power of 0.5 pu. Even with the proposed power locus, a harmonic compensation technique is mandatory. Hence a shunt APF is connected to the secondary taps of the front-end, star/star/delta, transformer to improve the input current THD and power factor. The APF with predictive current control and synchronous d-q frame base control arc used. To avoid time delay effects, the actual APF inverter transfer function is u.sed to formulate an open loop control strategy, used to achieve better harmonic cancellation than previously investigated techniques. To reduce the active filter current, a fixed shunt capacitor bank is connected to the transformer secondary taps to offset the proposed power locus and consequently, to minimize VAr compensation required of the APF. A series APF with a magnetic amplifier is used as a voltage harmonic compensator on the deside. It improves the output voltage ripple factor (RF) and reduces the de-link smoothing inductance requirement. Coupling both compensation techniques improves the supply current TI-ID, produces a near unity power factor, and the output voltage RF is reduced. An auxiliary dc-voltage source for the series APF is avoided by coupling the two compensators back-to-back. MATLAi3 simulation results for the MY system are experimental1y verified with a scaled low-voltage prototype system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available