Voltage and Power Balancing in Solar and Energy Storage Converters

With recent growth in the rapid adoption of solar photovoltaic (PV) power conversion, the integration of energy storage systems (ESS) is also on the rise. Successful ESS integration depends on the balance between system cost and performance. In this paper we focus on system performance, enabled by the proposed architecture which includes voltage and power balancing. The ESS becomes a valuable asset that allows flexibility in three-level neutral-point clamped converters (3L-NPC) to expand and develop new functionality. A bidirectional three-level buck-boost (3L-BB) converter plays an instrumental role in the proposed PV-ESS architecture. The 3L-BB is designed to perform dc-split bus neutral-point voltage balancing and damping through a 3ω-harmonic controller. This new feature leads to an immediate benefit of expanding the dc bus voltage utilization and eliminating the dissipative components for voltage balancing of any 3L-NPC operating mode. The bidirectional feature of the 3L-BB allows PV-ESS power balancing with reduced grid disturbance under dynamic events (e.g., transient clouds) of solar power production. The proposed PV-ESS system architecture was evaluated using a 100kW three-phase 3L-NPC converter and a 10kW 3L-BB converter. The simulation results indicate that the dc bus utilization can be increased by 4% with the proposed strategy. The evaluation results demonstrate the architecture's performance with voltage and power balancing.