Panel-to-Substring PWM Differential Power Processing Converter and Its Maximum Power Point Tracking Technique for Solar Roof of Plug-In Electric Vehicles

Abstract

In photovoltaic (PV) panels comprising multiple substrings, a mismatch in substring characteristics is known to reduce energy yield significantly. Substring characteristics in solar roofs of plug-in hybrid vehicles (PHVs) are always mismatched to some extent due to the curved surface of the panel. This paper proposes a PWM differential power processing (DPP) converter based on a panel-to-substring power redistribution architecture and its dual maximum power point tracking (MPPT) control technique for PHEVs’ solar roofs. Depending on the degree of characteristic mismatch, the proposed DPP converter adjusts its output current to maximize the energy yield of the panel. With the proposed dual MPPT control, a duty cycle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d_{DPP}$ </tex-math></inline-formula> of the DPP converter is manipulated to optimize the panel characteristic while an external boost converter manipulates its duty cycle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{boost}$ </tex-math></inline-formula> to track an MPP of the panel. A prototype for 180-W solar roofs comprising seven substrings was built, and laboratory testing was performed using solar array simulators to emulate characteristic mismatch conditions. Thanks to the dual MPPT control technique, the proposed DPP converter operated with the optimal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d_{DPP}$ </tex-math></inline-formula> while the external boost converter tracked the MPP by manipulating <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{boost}$ </tex-math></inline-formula> , realizing the enhanced energy yield.