Browsing by Author "Chen, Y."

Now showing 1 - 3 of 3
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    Multilevel Converters as Series VAR Compensators
    (IEEE, 1997-06) Mwinyiwiwa, Bakari M. M.; Wolanski, Z.; Ooi, B. T.; Chen, Y.
    This paper presents experimental results of a multilevel converter applied as a series static VAr compensator (SVS or STATCOM). An outer feedback loop maintains the VAr operating condition and inner feedback loops equalize the DC capacitor voltages. The delta connection of the transformer secondaries provide paths for zero sequence currents to flow. The tests show its capability for operation under normal balanced condition and under faulted conditions of single line and double line outages
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    Regulating and Equalizing dc Capacitance Voltages in Multilevel STATCOM
    (IEEE Transactions on Power Delivery, 1997) Chen, Y.; Mwinyiwiwa, Bakari M. M.; Wolanski, Z.; Ooi, B. T.
    Because of the high MVA ratings, it would be expensive to provide independent, equal, regulated DC voltage sources to power the multilevel converters which are proposed for STATCOMs. DC voltage sources can be derived from the DC link capacitances which are charged by the rectified AC power. This paper addresses two control issues: (1) regulation of the DC capacitance voltages and (2) their equalization. Equalization is necessary (i) to ensure the even sharing of voltage stresses in the gate-turn-off thyristors (GTOs), and (ii) to prevent the degradation of total harmonic distortion (THD) factors, as all harmonic elimination strategies depend on equal voltages in their assumptions. The strategies considered are: (a) the fundamental frequency method, and (b) the sinusoidal pulse width modulation method. Digital simulations are used to confirm the feasibility of the control methods
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    Unified Power Flow Controller (UPFC) Based on Chopper Stabilized Multilevel Converter
    (IEEE Transactions on Power Electronics, 2000) Chen, Y.; Mwinyiwiwa, Bakari M. M.; Wolanski, Z.; Ooi, B. T.
    As the diode-clamped, multilevel converter has been found to have attractive features for STATCOM application, there is interest in extending it to UPFC application by using multilevel converters as the series and the shunt converters. Unfortunately, as is demonstrated in this paper, the DC voltages at their DC links, are inherently unstable. Faced with this impasse, a solution is sought in a system of local feedback controlled Class B choppers to equalize the DC. A laboratory experimental model establishes the feasibility of the proposal. Digital simulations show that current ratings in the choppers need be only 10% of the current ratings in the converters. The chopper cost is estimated as 1% of the cost of the multilevel converters