Capacitive Current Feedforward Control Strategy for a Three-Phase LCL-filter-based T-type Grid-connected converter with the Fuzzy-PR

A three-level T-type grid-connected inverter has been widely used in the current medium power distributed PV inverters, charging station and active power filter system with the advantages of high equivalent switching frequency, high efficiency, small filter inductance and grid current harmonic. However, the grid-connected inverter with LCL-filter is a third-order and multi-variable system, to meet the high-performance requirements for grid-connected current, claiming a higher requirement for the grid-current control system. Aiming at this, a new control strategy named capacitive current feedforward control based on the carrier-based PWM modulation scheme on is put forward. Further, to improve the power density, the capacitor current is generated indirectly calculated by the capacitor voltage. Finally, to verify the correctness and effectiveness of the proposed control strategy, a complete digital simulation model and experimental prototype platform is established, the detailed theoretical analysis and design method of the proposed control strategy are presented. The simulation and experimental results show that the steady and the transient performance of the grid current with the proposed control strategy are effectively improved, and no additional sensors are needed.