A distributed active and reactive power control strategy for balancing grid-tied cascaded H-bridge PV inverter system

Unbalanced operation between panel-level modular inverters constrains the operating range of grid-tied cascaded H-bridge Photovoltaic (PV) inverter system when the active and reactive power of the architecture changes. The main objective of this paper is to propose a distributed control approach for balancing reactive power among inverters. The distributed controller allows fully decentralized architecture in terms of control and physical implementation of a PV system, resulting in higher reliability and potentially lower cost. The proposed control approach autonomously compensates reactive power contents of inverters caused by the active and reactive power changes by shifting their phase angle with local AC current measurement. Detailed modeling and analysis are provided to show the feasibility of the proposed control strategy. The decentralized control scheme is verified by real-time hardware-in-the-loop setup.