A dual inverter based grid connected solar power conditioning system with coordinated closed loop control

Abstract

In grid connected parallel solar inverter configuration, the power sharing between the inverter modules are achieved by sharing the current at identical AC output operating voltage across each inverter module. In conventional parallel configuration, high DC potentials are required to synthesize the identical AC output voltage across the inverter modules. Due to high DC voltages, the DC capacitor and switching devices would experience high dv/dt during inverter operation that would affect the performance of the solar power conditioning system (PCS). In this work, a method of reducing DC potentials across the individual inverter module is evaluated using dual two level inverter configuration. In the dual two level inverter configuration, the DC bus voltage would be shared between the inverter modules to synthesize the full AC voltage across the grid terminals. For appropriate sharing of the DC potential between the inverter modules based on the maximum available power point of the solar farm, a coordinated closed loop control is implemented based on the small signal analysis aiming to track not only the maximum power point but also grid voltage. The proposed configuration along with the closed loop control is evaluated analytically and results are validated by simulating circuit in MATLAB simulink.