Small-Signal Analysis of Cascaded Multilevel H-Bridge Inverter for PV Integration

This paper presents a small-signal modeling of cascaded H-bridge converter connected to a solar photovoltaic (PV) system. By analyzing eigenvalues of state-space equations of the system, the closed-loop controller has been designed to control the DC-link voltage in each cell as well as the grid current. The sensitivity and stability margins of the system have been examined by changing the grid impedance, capacitors of DC-link, and parameters of the controller. Also, the dynamic response of the system was analyzed by applying a step change in the DC-link setpoints. To verify the performance and effectiveness of the controllers, simulation has been conducted in MATLAB/SIMULINK for a three-phase cascaded H-bridge with three cells in each phase.