Performance analysis of a new elevated gain switched inductor-based quasi-Z-source-T-type inverter for small-scale grid-tied WECS

Wind energy conversion systems (WECS) benefit greatly from minimizing the number of power conversion stages, as this simplification improves the overall system efficiency. Among the single-stage converter topologies, the quasi-Z-source inverter (qZSI) is widely recognized for its inherent voltage boost capability, immunity to shoot-through faults, high output power quality, and flexibility for diverse applications. These characteristics make the qZSI an attractive choice for the WECS. However, directly connecting a small-scale, low-voltage WECS to a high-voltage grid requires a significantly higher boost ratio than conventional qZSI designs without compromising power quality. Standard qZSI topologies face an inherent trade-off: increasing the shoot-through duty cycle to achieve a greater boost reduces the modulation index, limiting the performance at high boost ratios. To overcome these limitations, this study introduces an elevated gain three-level switched inductor-based quasi-Z-source T-type inverter (SL-qZST2I) tailored for WECS. The proposed SL-qZST2I topology achieves a substantially higher voltage gain at a lower shoot-through duty ratio while maintaining a high modulation index, making it well-suited for direct high-voltage grid integration. Additionally, the proposed system incorporates a coordinated control strategy comprising a DC-link voltage regulator, neutral-point voltage balancing controller, maximum power point tracking (MPPT) controller, and grid current controller. This comprehensive control scheme ensures optimal power extraction from the wind turbine and stable and efficient power delivery to the grid. The performance and effectiveness of the proposed inverter are validated through detailed MATLAB simulations and experimental tests on a laboratory prototype, demonstrating its practical viability and robust operation.