Cascaded H-bridge control for PV application

In this paper, application of a cascaded H-bridge (CHB) converter to connect strings of solar panels to a single-phase medium voltage AC grid is discussed. With solar insolation levels differing from one string to another, it is challenging to control a CHB converter in order to minimize the variations in the dc link voltages of each of the converter modules and hence the device voltage stress levels. To minimize the device voltage stresses, in this paper, a new Maximum Power Point Tracking (MPPT) method is proposed. The proposed method equalizes the power drawn from each of the solar strings connected to the CHB across a large geographical area (e.g. along a railway line) and avoids excess device stresses. The proposed MPPT method is verified using simulation results.