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Power and Voltage Regulation of a Quad Active Bridge

Hatatah, Mohammed A. (2021) Power and Voltage Regulation of a Quad Active Bridge. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The solid-state transformer (SST) has received substantial attention because of its potential in helping to achieve more intelligent grid systems. The SST is a combination of power electronic (PE) converters and a high-frequency transformer (HFT), thus, reducing volumetric footprint resulting in space savings. The SST provides several functions such as controllable voltage and disturbance isolation. It also provides a dc-link voltage that helps advancements towards complete DC distribution systems.
A challenge identified from within the literature is balancing the voltages for each of the ports on the MV side of the QAB. Renewable energy supply to these ports will be stochastic in nature resulting in voltage variations at the output of the MV bridges feeding the transformer. If this is not managed appropriately, unequal power flow will be drawn by each of the ports leading to undesired voltage ripples that impact the DC-link voltage. In addition, the voltage unbalance problem makes it difficult to feed a common load without violating its voltage limits. Therefore, voltage regulation has to be investigated to target this voltage unbalance and maintain constant output voltage.
The proposed approach is based upon linear–quadratic regulator (LQR) control for the DC-DC stage of the SST to alleviate the issues mentioned for improved renewable energy regulation for SST applications. Despite the effort reported, nonlinearity and uncertainty are still a challenge in some applications. So, other combined techniques have been investigated to mitigate the phenomena mentioned earlier. This motivates the use of adaptive linear–quadratic regulator (ALQR) and nonlinear model predictive control (NMPC) to track the nonlinear change of the QAB converter due to the renewable energy. Although regulation purpose has been maintained in, stability is still a challenging point in the NMPC design. Thus, a control strategy is proposed to improve the regulation of the SST based QAB considering a practical NMPC scheme with guaranteed stability.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Hatatah, Mohammed A.mah332@pitt.edumah332
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorGrainger,
Committee MemberKwasinski,
Committee MemberKerestes,
Committee MemberDallal,
Committee MemberSolomon,
Date: 26 January 2021
Date Type: Publication
Defense Date: 5 August 2020
Approval Date: 26 January 2021
Submission Date: 8 September 2020
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 136
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Electrical and Computer Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: linear quadratic regulator (LQR), adaptive linear quadratic regulator (ALQR), nonlinear model predictive control (NMPC), power regulation, quadratic active bridge (QAB), solid-state transformer (SST).
Date Deposited: 26 Jan 2021 16:08
Last Modified: 26 Jan 2021 16:08

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