Voltage Stability Control of Bus Switch Capacitor in PV DC Collection System

Abstract

In PV DC Collection System, the application of parallel large-capacity electrolytic capacitors is capable to suppress the low-frequency voltage ripples on the DC Bus voltage. However, when a short circuit occurs on the DC Bus, large-capacity DC Bus capacitors dramatically discharge, which will introduce a large short circuit current, exposing the control and protection of the system in a extreme case. In order to reduce the electrolytic capacitors on the DC Bus side and limit the short-circuit current under inter-pole short-circuit conditions, this paper proposes the application of switched-capacitor topology in a PV DC Collection System, based on a Buck-Boost circuit. A flexible adjustable control strategy has also been designed for the equivalent capacitance value based on this topology. The research results show that this topology and control method can effectively suppress voltage ripples, reduce the use of electrolytic capacitors, and realize electroless capacitance of the system. Finally, the effectiveness of the proposed topology and control strategy is verified by the MATLAB/Simulink simulation model.