This research and development work deals with the design methodology for
Cascaded Multilevel Converter (CMC) based Transmission STATCOM (TSTATCOM)
and development of a ± / 12MVAR, 12kV line-to-line wye-connected,
11-level CMC. This CMC module constitutes the basic building block of TSTATCOM
systems. Sizing of the CMC module, number of H-Bridges in each phase
of the CMC, AC voltage rating of the CMC, the number of paralleled CMC modules
in the T-STATCOM system, optimum value of series filter reactors and
determination of busbar in the power grid to which the T-STATCOM system is
going to be connected are also discussed in the thesis in view of IEEE Std.519-1992,
current status of HV IGBT technology and the required reactive power variation
range for the T-STATCOM application. In the field prototype of the CMC module,
the AC voltages are approximated to sinusoidal waves by Selective Harmonic
Elimination Method (SHEM) and by the use of an optimized series input filter
reactor. The use of n number of HBs in each phase provides us n number of freedom in the application of SHEM. One of them is allocated to the fundamental component
while n-1 is for the elimination of low order harmonics. Since n is chosen to five in
the prototype system, 5th, 7th,11th and 13th harmonic components are successfully
eliminated in the AC voltage waveforms of the CMC module. The equalization of
DC link capacitor voltages is achieved according to Modified Selective Swapping
(MSS) algorithm. MSS is applied every 400&mu / s period if needed to obtain a perfect
equalization of DC link capacitor voltages at the expense of higher switching
frequency and hence switching losses. In this research work, an L-shaped laminated
bus has been designed and the HV IGBT driver circuit has been modified for
optimum switching performance of HV IGBT modules in each HB circuit. The
performances of the HB circuit and the resulting 11-level CMC module have been
obtained not only in the laboratory but also in the field. Design works for HB and the
CMC are based on MATLAB and PSCAD simulations. The laboratory and field
performance of the HB circuit and CMC module is found to be satisfactory and quite
consistent with the theoretical results and design objectives. In addition to these, 154
kV, ± / 50MVAr T-STATCOM prototype has been designed, implemented and
installed at Sincan Transformer Substation-Ankara primarily for the purposes of
reactive power compensation and terminal voltage regulation. The T-STATCOM
prototype is composed of five parallel operated CMC modules developed within the
scope of this PhD thesis research work. The T-STATCOM configuration permits the
operation of any number of CMC modules in the range from one to five for
experimental purposes. The performance of this T-STATCOM system is also
presented in this PhD thesis as a sample application.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12614941/index.pdf |
| Date | 01 September 2012 |
| Creators | Gultekin, Burhan |
| Contributors | Ermis, Muammer |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | Access forbidden for 1 year |
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