A Control System of PV Sources for DC Microgrid with Seamless Switching Operation between I-V Droop Control and MPPT Control

Abstract

As one of the decentralized control methods for the DC microgrid, DC bus signaling is considered which switch an operation mode of each connected converter based on a bus voltage. In a PV converter, a control method that switches between MPPT control, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V-P$</tex> droop or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V-I$</tex> droop control based on the bus voltage has been studied. This research proposed a new control method for PV converter which switches between MPPT control and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I-V$</tex> droop control with regulating a PV current. Compared to previous method using <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V-I$</tex> droop control, the proposed method can reduce a number of dynamic feedback loops, which will simplify the system design. This paper shows that the droop characteristics of the previous and the proposed methods are almost the same, and discusses how to analyze the DC operating point for system design. In addition, the steady-state and dynamic characteristics of the proposed method are confirmed through numerical calculations and circuit simulations.