Theses and Dissertations
Displaying 1 - 3 of 3
Filtering by
- All Subjects: Solid State Transformer
- Creators: Ayyanar, Raja
Description
The Solid State Transformer (SST) is an essential component in the FREEDM system. This research focuses on the modeling of the SST and the controller hardware in the loop (CHIL) implementation of the SST for the support of the FREEDM system demonstration. The energy based control strategy for a three-stage SST is analyzed and applied. A simplified average model of the three-stage SST that is suitable for simulation in real time digital simulator (RTDS) has been developed in this study. The model is also useful for general time-domain power system analysis and simulation. The proposed simplified av-erage model has been validated in MATLAB and PLECS. The accuracy of the model has been verified through comparison with the cycle-by-cycle average (CCA) model and de-tailed 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 the SST in RTDS is described in this report. The parameter setup of the model has been discussed in detail. One of the dif-ficulties is the choice of the damping factor, which is revealed in this paper. Also 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 distributed energy storage interface power injection and reverse power flow have been validated. Some limitations are noticed and discussed through the simulation on RTDS.
ContributorsJiang, Youyuan (Author) / Ayyanar, Raja (Thesis advisor) / Holbert, Keith E. (Committee member) / Chowdhury, Srabanti (Committee member) / Arizona State University (Publisher)
Created2014
Description
In recent years, wide bandgap (WBG) devices enable power converters with higher power density and higher efficiency. On the other hand, smart grid technologies are getting mature due to new battery technology and computer technology. In the near future, the two technologies will form the next generation of smart grid enabled by WBG devices. This dissertation deals with two applications: silicon carbide (SiC) device used for medium voltage level interface (7.2 kV to 240 V) and gallium nitride (GaN) device used for low voltage level interface (240 V/120 V). A 20 kW solid state transformer (SST) is designed with 6 kHz switching frequency SiC rectifier. Then three robust control design methods are proposed for each of its smart grid operation modes. In grid connected mode, a new LCL filter design method is proposed considering grid voltage THD, grid current THD and current regulation loop robust stability with respect to the grid impedance change. In grid islanded mode, µ synthesis method combined with variable structure control is used to design a robust controller for grid voltage regulation. For grid emergency mode, multivariable controller designed using H infinity synthesis method is proposed for accurate power sharing. Controller-hardware-in-the-loop (CHIL) testbed considering 7-SST system is setup with Real Time Digital Simulator (RTDS). The real TMS320F28335 DSP and Spartan 6 FPGA control board is used to interface a switching model SST in RTDS. And the proposed control methods are tested. For low voltage level application, a 3.3 kW smart grid hardware is built with 3 GaN inverters. The inverters are designed with the GaN device characterized using the proposed multi-function double pulse tester. The inverter is controlled by onboard TMS320F28379D dual core DSP with 200 kHz sampling frequency. Each inverter is tested to process 2.2 kW power with overall efficiency of 96.5 % at room temperature. The smart grid monitor system and fault interrupt devices (FID) based on Arduino Mega2560 are built and tested. The smart grid cooperates with GaN inverters through CAN bus communication. At last, the three GaN inverters smart grid achieved the function of grid connected to islanded mode smooth transition
ContributorsYao, Tong (Author) / Ayyanar, Raja (Thesis advisor) / Karady, George G. (Committee member) / Qin, Jiangchao (Committee member) / Tsakalis, Konstantinos (Committee member) / Arizona State University (Publisher)
Created2017
Description
With the penetration of distributed renewable energy and the development of
semiconductor technology, power electronic devices could be utilized to interface re-
newable energy generation and the distribution power grid. However, when directly
connected to the power grid, the semiconductors inside the power electronic devices
could be vulnerable to the power system transient, especially to lightning strikes.
The work of this research focuses on the insulation coordination of power elec-
tronic devices connected directly to the power distribution system. The Solid State
Transformer (SST) in Future Renewable Electric Energy Delivery and Management
(FREEDM) system could be a good example for grid connected power electronic
devices. Simulations were conducted in Power Systems Computer Aided Design
(PSCAD) software. A simulation done to the FREEDM SST showed primary re-
sults which were then compare to simulation done to the grid-connected operating
Voltage Source Converter (VSC) to get more objective results.
Based on the simulation results, voltage surges caused by lightning strikes could
result in damage on the grid-connected electronic devices. Placing Metal Oxide Surge
Arresers (MOSA, also known as Metal Oxide Surge Varistor, MOV) at the front lter
could provide eective protection for those devices from power transient. Part of this
research work was published as a conference paper and was presented at CIGRE US
National Conference: Grid of the Future Symposium [1] and North American Power
Symposium [2].
semiconductor technology, power electronic devices could be utilized to interface re-
newable energy generation and the distribution power grid. However, when directly
connected to the power grid, the semiconductors inside the power electronic devices
could be vulnerable to the power system transient, especially to lightning strikes.
The work of this research focuses on the insulation coordination of power elec-
tronic devices connected directly to the power distribution system. The Solid State
Transformer (SST) in Future Renewable Electric Energy Delivery and Management
(FREEDM) system could be a good example for grid connected power electronic
devices. Simulations were conducted in Power Systems Computer Aided Design
(PSCAD) software. A simulation done to the FREEDM SST showed primary re-
sults which were then compare to simulation done to the grid-connected operating
Voltage Source Converter (VSC) to get more objective results.
Based on the simulation results, voltage surges caused by lightning strikes could
result in damage on the grid-connected electronic devices. Placing Metal Oxide Surge
Arresers (MOSA, also known as Metal Oxide Surge Varistor, MOV) at the front lter
could provide eective protection for those devices from power transient. Part of this
research work was published as a conference paper and was presented at CIGRE US
National Conference: Grid of the Future Symposium [1] and North American Power
Symposium [2].
ContributorsRong, Xuening (Author) / Karady, George G. (Thesis advisor) / Heydt, Gerald T (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2017