Application of pscad-emtp-phase shifter modeling.pdf
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Chapter 5: Transformers 48 Applications of PSCAD/EMTDC PHASE SHIFTING TRANSFORMERS Phase shifting transformers can be assembled in PSCAD using multi-winding single phase transformers. This requires that the winding connections be known. Tap changers can be applied to effect a variable phase shift. If core modeling is a requirement, the advantage of the UMEC three phase transformer with its core modeling capability is of limited benefit because each winding end cannot be brought out for connections. If the actual phase shifter is constructed with a three limb core, a fictitious delta winding may need to be added in the model built from single phase units to obtain the correct zero sequence effects. As an example, converters with 24 pulse or higher employ phase shift transformers. Consider a 24 pulse converter transformer comprised of two similar 12 pulse converter transformers, one phase shifted +7.5° and the other phase shifter –7.5°. Each 12 pulse transformer is assembled in single-phase units from the UMEC four winding model in the Transformers Page in the Master Library. The connections are made as shown above with the star primary windings in series. Leakage reactance is best checked by undertaking a simulated short circuit test. Apply a short circuit to the secondary wind- ings with small resistances and determine the p.u. transformer short circuit reactance as calculated from the measured voltages. Adjust the transformer leakage reactance until the desired short circuit reactance is observed by short circuit test. Other types of complex transformers, such as 6-phase and zig-zag transformers, can also be built by assembling single-phase units. The winding connections for each transformer are shown. The winding turns for each winding and is proportional to the number indicated (kV rating of the winding). The core on which each winding is wound is defined by the angle of alignment depicted in the diagram. The AC side windings are wound to provide a 7.5 o phase shift. 3.649 0.6 3.649 3.649 3.649 3.649 3.649 0.6 0.6 0.6 0.6 0.6 0.16 0.16 0.16 0.16 0.16 0.16 0.278 0.278 0.278 0 278 0.278 0 278 More complex winding arrangements might require more than four coupled windings, which is not available in the Master Library. Contact [email protected] if you have a need for more coupled windings.
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phase shifter modeling
Transcript of Application of pscad-emtp-phase shifter modeling.pdf
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Chapter 5: Transformers
48 Applications of PSCAD/EMTDC
PHASE SHIFTING TRANSFORMERS
Phase shifting transformers can be assembled in PSCAD using multi-winding single phase transformers. This requires that the winding connections be known. Tap changers can be applied to effect a variable phase shift. If core modeling is a requirement, the advantage of the UMEC three phase transformer with its core modeling capability is of limited benefit because each winding end cannot be brought out for connections. If the actual phase shifter is constructed with a three limb core, a fictitious delta winding may need to be added in the model built from single phase units to obtain the correct zero sequence effects.
As an example, converters with 24 pulse or higher employ phase shift transformers. Consider a 24 pulse converter transformer comprised of two similar 12 pulse converter transformers, one phase shifted +7.5 and the other phase shifter 7.5.
Each 12 pulse transformer is assembled in single-phase units from the UMEC four winding model in the Transformers Page in the Master Library. The connections are made as shown above with the star primary windings in series.
Leakage reactance is best checked by undertaking a simulated short circuit test. Apply a short circuit to the secondary wind-ings with small resistances and determine the p.u. transformer short circuit reactance as calculated from the measured voltages. Adjust the transformer leakage reactance until the desired short circuit reactance is observed by short circuit test.
Other types of complex transformers, such as 6-phase and zig-zag transformers, can also be built by assembling single-phase units.
The winding connections for each transformer are shown. The winding turns for each winding and is proportional to the number indicated (kV rating of the winding). The core on which each winding is wound is defined by the angle of alignment depicted in the diagram. The AC side windings are wound to provide a 7.5o phase shift.
3.649
0.6
3.649 3.649
3.649
3.649 3.649
0.6 0.6
0.6
0.6
0.6
0.16
0.16 0.16
0.16 0.16 0.16
0.278
0.278 0.278
0 278
0.278
0 278
More complex winding arrangements might require more than four coupled windings, which is not available in the Master Library. Contact [email protected] if you have a need for more coupled windings.
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Applications of PSCAD/EMTDC
49Applications of PSCAD/EMTDC
REFERENCES
1. Hermann W. Dommel, Transformer Models in the Simulation of Electromagnetic Transients, 5th Power Systems Computation Conference, Cambridge, England, Sept 1-5, 1975.
2. W. Enright, O.B. Nayak, G.D. Irwin, J. Arrillaga, An Electromagnetic Transients Model of Multi-limb Transformers Using Normalized Core Concept, Proceedings of IPST97 International Conference on Power System Transients, Seattle, June 22-26, 1997, pp 93-98.
EXERCISES
5.1 Load example case Example5.1.psc which is the case of a DC current saturation test with a Y-Y winding con guration and a UMEC three limbed core. Start the case with 0.1 kA of DC current in the neutral and con rm the transformer does not saturate. Change to a 5 limbed core and repeat the test. Build the transformer from single phase units for a Y-Y winding con guration of the same 3 phase rating as the UMEC model using the general transformer model. Repeat the test with 0.1 kA in the transformer neutral showing saturation. Design a third delta winding to represent a 3 limb core and repeat the test and compare with the UMEC test with a 3 limb core.
5.2 With example case Example5.1.psc studied above for the Y-Y winding con guration, observe the harmonics detected in the primary windings of the transformer (winding #1). Make note of the 3rd harmonic level. Change the secondary winding to a winding and repeat the test with all other parameters remaining equal. Was any 3rd harmonic detected and why?
5.3 Load example case Example5.3.psc which is a case to energize a transformer with remanence setting. With the circuit breaker initially closed, and the remanence at zero in each phase, ramp the source volts up slowly (change the Three Phase Source parameter Voltage Input Time Constant on the data entry sheet) and observe what the peak ux linkages are in reference to the 230 kV winding (#1). Is this level expected? Return the breaker to close at 0.5 second, and the Voltage Input Time Constant to 0.05 seconds, and adjust the remanence initializing current sources until a maximum inrush current on one of the phases is observed. Do not take the remanence above 0.8 p.u. of rated ux. Adjust the In rush decay time constant in the saturation data sheet of the transformer model to 0.0, thus removing any arti cial inrush current damping, and observe response.
Connection of six four-winding single-phase UMEC transformers for 24 pulse converter application.
