Operation and Control of Smart Transformer for Improving Performance of Medium Voltage Power Distribution System

ABSTRACT:  

Smart transformer (ST) is a power electronic based transformer equipped with effective control and communication. It is expected to play a significant role in future power distribution system, however, their operational features in the medium voltage (MV) power distribution systems are yet not explored.

In this paper,operation and control of ST are presented for improving its performance and operational range in a power distribution system consisting of two radial feeders in a city center. For investigating the performance of ST in above system, one conventional power transformer (CPT) is replaced by the ST whereas other feeder is continued to be supplied through the CPT. In this scheme, the ST is operated such that it makes total MV grid currents of the combined system balanced sinusoidal with unity power factor.

Therefore, in addition to providing continuous and reliable operation of ST based loads, the ST can also improve the performance of the loads which are supplied by the CPT in a different feeder. Moreover, the proposed scheme eliminates the need of power quality improvement devices at the other feeder. Therefore, the scheme also makes the application of ST in the distribution system cost effective. Simulation results validate the suitability of ST in improving the performance of multiple feeder medium voltage power distribution system.

KEYWORDS:

  1. Smart transformer (ST)
  2. Medium voltage rectifier
  3. Power distribution system

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 Fig. 1. A schematic of conventional power distribution system consisting of

two radial feeders in a city center.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulated waveforms when ST is not compensating for feeder II. (a) PCC voltages. (b) Grid currents. (c) MV rectifier currents (d) Feeder II currents.

Fig. 3. Simulated waveforms when ST is compensating for feeder II. (a) PCC voltages. (b) Grid currents. (c) MV rectifier currents (d) Feeder II currents.

Fig. 4. Simulated waveforms during transient conditions when load in feeder II is changed. (a) PCC voltages. (b) Grid currents. (c) MV rectifier currents (d) Feeder II currents.

 CONCLUSION:

 In this paper, the operation and control of a futuristic power distribution system consisting of two radial feeders with one CPT replaced by an ST is presented. It is shown that the ST can compensate for the loads connected at the feeder supplied by the CPTs, in addition to supplying their own loads. This scheme has potential to eliminate the requirement of power quality improvement devices such as STATCOM, power factor correcting capacitors, etc., connected at the second feeder. This ancillary feature in the medium voltage power distribution systems has potential to make application of ST more attractive and cost effective.

REFERENCES:

[1] S. Bifaretti, P. Zanchetta, A. Watson, L. Tarisciotti, and J. Clare, “Advanced power electronic conversion and control system for universal and flexible power management,” Smart Grid, IEEE Transactions on, vol. 2, no. 2, pp. 231–243, Jun. 2011.

[2] X. She, R. Burgos, G. Wang, F. Wang, and A. Huang, “Review of solid state transformer in the distribution system: From components to field application,” in Energy Conversion Congress and Exposition (ECCE),

2012 IEEE, Sep. 2012, pp. 4077–4084.

[3] S. Alepuz, F. Gonzalez, J. Martin-Arnedo, and J. Martinez, “Solid state transformer with low-voltage ride-through and current unbalance management capabilities,” in Industrial Electronics Society, IECON 2013 – 39th Annual Conference of the IEEE, Nov. 2013, pp. 1278–1283.

[4] S.-H. Hwang, X. Liu, J.-M. Kim, and H. Li, “Distributed digital control of modular-based solid-state transformer using dsp+fpga,” Industrial Electronics, IEEE Transactions on, vol. 60, no. 2, pp. 670–680, Feb. 2013.

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