Download Modeling of Solid State Transformer for the FREEDM System

School of Electrical, Computer and Energy Engineering
M.S. Final Oral Defense
Modeling of Solid State Transformer for the FREEDM System Demonstration
by
Youyuan Jiang
Date: April 18, 2014
Time: 8:00 AM
Room: GWC 208 C
Committee:
Dr. Raja Ayyanar (chair)
Dr. Keith Holbert
Dr. Srabanti Chowdhury
Abstract
The Solid State Transformer (SST) is an essential component in the FREEDM
system and it would have made much more impact in the future smart grid. This report
focuses on the modeling of SST and the controller hardware in the loop implementation
of SST for the support of the FREEDM system demonstration.
The Energy based control strategy for three stage SST is analyzed and applied, a
simplified average model of three stage SST that suitable for RTDS simulation has been
developed in this report. The model is also useful for general time-domain power system
analysis and simulation. The proposed simplified average model has been validated in
MATLAB and PLECS, the accuracy of the model has been verified through comparison
with the CCA average model and detailed switching model. These models are also
implemented in PSCAD, and a special strategy to implement the phase shift modulation
has been proposed to enable the switching model simulation in PSCAD.
The implementation of the CHIL test environment of SST in RTDS is described
in this report. The parameter setup of the model has been discussed in detail. One of the
difficulties is the choice of the damping factor, which is revealed in this paper. Also,
because of the solver, the grounding of the system has large impact on the RTDS
simulation. Another problem is that the performance of the system is highly dependent on
the switch parameters such as voltage and current ratings. Finally, the functionalities of
the SST have been realized on the platform. The DES interface power injection and
reverse power flow has been validated. Some limitations are noticed and discussed
through the simulation on RTDS.