Integrated Model Predictive Control of Double-Stage Solid-State Transformers With Dynamic Reference

The dc-link voltage control is crucial for double-stage solid-state transformers. Due to differences in bandwidth and response speed between the two stages, overvoltage and undervoltage may occur in transient states, potentially leading to overmodulation in the rectifier stage and overcurrent in the dc stage. In extreme cases, the reliable operation of the entire system is threatened. Model predictive control (MPC) methods have been utilized to improve the dynamic performance of the dc-link in some previous works. However, they mainly work as the inner loop. While the inner loop is indeed enhanced, the overall dynamic remains limited by the employment of linear controllers in the outer voltage loop. To address this issue, this article proposes an integrated MPC with dynamic reference generation. Herein, the integrated cost functions for both stages account for all relevant variables. Following with it, the dynamic reference method generates real-time commands for the dc-link based on load estimation, eliminating the need for linear controllers in the outer loop. The response speed of the MPC is fully released, significantly improving the dynamic performance of the dc-link while maintaining a straightforward implementation. Finally, the experimental comparisons with other schemes verify the effectiveness and superiority of the proposed method.