ECE PhD Dissertation Defense: Yue Zheng

PhD Dissertation Defense: Modular Plug-and-Play Photovoltaic Subpanel System

Yue Zheng

Location: Zoom Link

Abstract: This thesis designs, builds and tests plug-and-play photovoltaic (PV) panels. A prototype modular PV system is built consisting of a dozen small PV units that can slide in and out of a mechanical frame without impacting other units. Each unit contains one PV subpanel and a DC-DC converter with a distributed maximum power point tracking (dMPPT) control board. Each PV unit works at its maximum power, while every output of the converter is connected in parallel to a DC bus. A new combined control strategy is proposed in which the decision to use centralized or distributed control depends on the system efficiency at the varying load operating points. A disadvantage of this dMPPT structure is that in each PV unit, the DC-DC converter must convert the entire power from its PV subpanel. Therefore, this research also explores the use of Differential Power Processing (DPP) system, which harvests maximum power while only processing a small amount of power due to the mismatches between PV panels. Thus, DPP structure reduces power loss compared to traditional dMPPT structure. Since it processes only a small amount of power, differential power processing structure has the potential to further be integrated on a chip and become installed in the junction box during the assembling process. Finally, the research proposes to implement the plug-and-play features of the solar PV system using wireless power transfer (WPT) instead of hard wire connectors. A series-to-series topology of WPT system (L-R-C series circuit) for one PV unit is proposed. In this system, the DC-DC converter on the PV side is used to perform MPPT, while the DC-AC inverter simultaneously perturbs its switching frequency to match possible variations in resonance frequencies. Wireless communication is used between transmitter and receiver. Thus, the maximum efficiency point on the constant output voltage trajectory can be tracked dynamically under wide and varying operating conditions.