Enhanced Capacitor Voltage Balancing of Interleaved Modular Multilevel Converter in Medium Voltage DC Collection Grid

Nowadays a wide range of medium voltage DC collection grid technologies are used in renewable energy applications to increase power density. The existing medium voltage DC collection grids are integrated with medium voltage DC-DC converters. These DCDC converters are employed with bulky passive components like step-up transformers, which lead to more cost and space requirement. This paper considers a medium voltage DC collection grid technology for large-scale solar PV power plants having Interleaved Modular Multilevel (IMMC) DC-DC step-up converter, which consists of four sets of IMMC converter blocks connected in series which are powered by two sets of solar panels. With regard to these IMMC, imbalance in the voltage of each sub-module capacitors is a major issue to be addressed. Simulation of the system is designed for converting 1500 V DC input to 16 kV at DC collection grid. A PID controller is proposed to balance the voltage of each sub-module capacitors in the interleaved modular multilevel converter (IMMC). The results obtained by simulation in Matlab Simulink shows the better performance in voltage balancing.