DC-bus voltage balancing control for 3-level DC/DC converters in renewable generation systems

Abstract

This paper investigates the dc-bus voltage balancing for 3-level DC/DC converters. First, the system control diagram is introduced. Then, based on duty cycle and operating modes, four different cases are illustrated. The output voltages under four cases are detailed, and the dc-bus voltage balancing actions for different cases are summarized. The dc-bus voltage balancing situation becomes worse when the system is in the condition of D > 0.5 and DCM. Therefore, three methods are proposed to solve the issue raised. The first method is to limit D≤0.5. The second method applies an opposite control when D > 0.5 and DCM. The third solution adopts an intelligent control.

Keywords

• 3-level converter
• DC/DC
• DC-bus balancing