Control and performance of a cascaded H-bridge photovoltaic power system

This thesis presents the control and performance of a Cascaded H-Bridge photovoltaic power system. The cascaded H-Bridge multilevel converter offers a number of attractive features for use in photovoltaic power systems. They provide opportunities for increases in efficiency, superior tracking of the maximum available power and direct connection to higher voltages. This system topology is a relatively immature technology and a number of key areas exist for research. In particular, the individual maximum power point tracking performance requires further analysis and development, the operation of the system in the presence of variable power generation in the photovoltaic arrays requires further investigation and the ability of the system to maintain operation under different array configurations is an interesting area for investigation. The details and the performance of a heuristic model predictive control scheme are presented, as well as the control techniques used to compensate for the power variability. The operation of the system when some arrays have zero power is also investigated. Two new maximum power point tracking techniques are proposed and the performance relative to the established Perturb and Observe technique is evaluated. A photovoltaic array current sensorless technique is also developed to exploit the switching characteristics produced by the model predictive control scheme. Finally, simulation and experimental results are presented that evaluate and validate the performance of the proposed control techniques. The results show that the proposed control techniques offer excellent performance.