Design and Miniaturization of Power Efficiency Optimizer for Series PV Modules

With continuous cost down and technological progress development, the worldwide installed photovoltaic (PV) generation capacity has tended toward exponential growth in recent years. However, a major challenge in using the PV source is solving its inherent low voltage compatibility with an electrical load. PV modules in series connection might provide a feasible solution to the voltage matching problem but are subject to a significant decline in power generation because the current flowing in a PV string is confined to the PV module with the lowest photocurrent. The series PV modules subject to partial shading (PS) and aging are typical cases that cause inhomogeneous photocurrent. Conventional solution to reduce the power loss due to PS is to connect a diode anti-parallel to each PV module in order to bypass the partial shaded PV modules from the PV string. However, the bypassed PV modules might be many and are capable of providing power. The accumulative amounts of the available power the bypassed PV modules owned would be significant. This project presents a Distributed Power Optimizer to restore part of power loss caused by the PS. A maximum voltage point tracking (MVPT) algorithm is performed to drive the operating point of the PV modules simultaneously toward respective maximum power points (MPPs) and guarantee power peak uniqueness. The power optimizer circuit is realized by means of a controllable current transformer (CCT) disposed at the terminal of each PV module permitting compatible current in the series path of a PV string. Appropriate CCT output current can be determined by a commercial grid-tied PV inverter with the function of MPPT. The MPPT can avert undue CCT activation and consequently reduce the switching loss and copper loss of the converter circuit. This project is devoted to the development of power optimizer key technologies for the PV modules. The achievements are summarized as follows: (1) PV cell numerical modeling; (2) power optimizer circuit design; (3) MVPT derivation and convergence verification; (4) control power source design (5) on site test and tuning; (6) print circuit board merging. The key technologies developed in this project with the superiority of the simple control and circuit construction is a revolution in the solar power market and in favor of the setup of the self-contented technologies of industry.

Project ID:PB10411-0073
External Project ID:MOST104-2622-E845-001-CC3