A Flexible Power Control for PV-Battery Hybrid System Using Cascaded H-Bridge Converters

The cascaded H-bridge (CHB) is a good candidate to integrate multiple photovoltaic (PV) arrays into the power grid. However, due to the internal uncertain power supply of renewable sources, it is difficult to meet the power grid power command with only PV arrays. To overcome this limitation, a CHB converter with both PV arrays and energy storage units in the dc rails is proposed in this paper. First, a two-layer hierarchical control is developed for independent PQ control and power distribution among each CHB cell, while meeting with the grid PQ reference command at the same time (P represents “active power” and Q represents “reactive power”). Then, a modified power management method is developed to adaptively modify the current power points for PV panels from their maximum power points to solve the potential overmodulation problem caused by frequent battery charging and discharging. With the proposed approach, a good harvesting of PV power can be ensured in various situations. Verification results are provided to validate the performance of the proposed system.