New multi-pulse diode rectifiers with reduced kVA capacities for harmonic current reduction in static power converter systems /
In most power electronic applications, such as ac/dc motor drives, switch mode power supplies, uninterruptible power supplies for critical loads, induction heating, electrochemical process control and aircraft power systems, the interface between the static power converter system and the electric ut...
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1995.
|
| Subjects: |
| Summary: | In most power electronic applications, such as ac/dc motor drives, switch mode power supplies, uninterruptible power supplies for critical loads, induction heating, electrochemical process control and aircraft power systems, the interface between the static power converter system and the electric utility is via three-phase uncontrolled diode rectifier. Due to the presence of a large dc-link smoothing capacitor and the nonlinear operation of the rectifier diodes, the input line current is highly distorted and rich in low order harmonics. The excessive harmonics drawn by power electronic equipment contribute to a number of problems in the power system including increased VA rating of the components, excessive heating in power delivery equipments, malfunctions of sensitive electronic equipments such as computers, protective relays and interference in communication system. The recommended practice, IEEE 519, has evolved to maintain utility power quality at acceptable levels. In response to these concerns, this research proposes three new multi-pulse diode rectifier systems with 'clean' power characteristics. The proposed systems exhibit improved performance, lower total harmonic distortion (THD) in input line currents and reduced transformer kVA. In the first study, reduced kVA polyphase transformer arrangements are proposed for harmonic current reduction in diode rectifier type utility interface. Both 12-pulse and 18-pulse diode rectifier systems are proposed with transformer kVA ratings of 0. 18 P. (PU) and 0. 16 P. (PU), respectively. This translates into over 80% reduction in transformer size and cost compared to the conventional systems. The second study includes a passive and an active PWM approach employing a tapped interphase reactor. In the passive approach, a new 24-pulse rectifier system with 5th, 7th, I I t, 13th, 17th and 19th harmonics eliminated in the utility line currents is obtained by design of a specially tapped interphase reactor. This approach is further extended to a 48-pulse system by PWM control of two gate turn-off devices. Finally, in the third study, an active interphase reactor is introduced to draw sinusoidal input currents from the electric utility. In this scheme a low kVA PWM-controlled current source is injected into the secondary winding of the interphase reactor. The exact shape of the injected current is mathematically computed and is shown to be near triangular in wave shape-The active interphase reactor virtually eliminates all of the harmonic currents drawn by the rectifier type utility interface. This results in near sinusoidal input currents from the utility with less than I% THD. For all of the above proposed schemes, simulation results are included and experimental results are provided from a lOkVA, 208V laboratory prototype diode rectifier system. |
|---|---|
| Item Description: | Vita. "Major Subject: Electrical Engineering". |
| Physical Description: | xii, 123 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |