順滑控制在降壓型直流轉換器之應用

Abstract

本文研製之順滑模態控制器應用在降壓型直流轉換器電路，改善過去使用誤差狀態方程式設計順滑模態控制器時必須掌握負載狀況的缺點，以及為了估測負載降低系統精確度與響應速度的缺點。我們利用轉換矩陣法選取一順滑函數，並額外加入輸出電壓與命令電壓之誤差函數的積分，使系統在順滑平面上是穩定的，再決定系統的控制法則，使系統軌跡在有限時間內接觸到順滑平面。 本文利用此順滑模態控制器產生控制開關狀態的責任週期，經由固定頻率切換的脈波寬度調變控制Buck 直流轉換器，使其輸出電壓到達期望值，並且不因負載變動影響系統之穩定。利用MATLAB/SIMULINK 模擬上述直流轉換器與順滑模態控制器，由模擬結果驗證系統對於不同負載均能產生穩定的責任週期，使輸出電壓到達正確值，而且當負載變動時，控制器也具有不錯的暫態響應。

A sliding mode controller with the error integration between output voltage and command voltage for PWM-based Buck DC-DC converter is proposed. Constant switching frequency can be achieved with the proposed approach. For the controller design, this thesis adopts sliding mode control theorem because of its well-know robustness for system uncertainty. Without load estimator in the controller, this closed-loop system ideally should convert power flow into the prescribed form in spite of the load variation. With the unknown load condition we choose a sliding function with an integral term of error function such that the system is stabilized on the sliding surface. Then design the control algorithm such that the system reaches the sliding mode in a finite time. The simulation of the proposed closed-loop control scheme is illustrated to process fast transient response and robustness to load variation.