- 學位論文
結合模式預測控制和重複控制策略改善不平衡與非線性負載時孤島模式下電力轉換器控制
Dynamical Performance Enhancement of Isolated Power Converters under Unbalanced and Nonlinear Load Conditions by Combining Model Predictive Control and Repetitive Control
摘要
在微電網孤島模式的操作下，輸出電壓波形受到負載條件的不同而有所影響，其中又以不平衡負載與非線性負載影響甚鉅。為了降低不平衡負載所造成的電壓不平衡率以及改善總電壓諧波失真率(Total Harmonic Distortion,THD)，本文於現有的電壓源轉換器（Voltage Source Converter,VSC）之雙迴圈控制架構下，採用模式預測控制於內迴圈電流控制器設計，並將重複控制用於外迴圈電壓控制器。其中，由推導得知內迴圈電流閉迴路系統轉移函數，並根據它來設計外迴圈之重複電壓控制器。結合兩者的優點，不僅在追蹤週期性訊號或抑制週期性的干擾都能有效達到零穩態誤差追蹤的效果，且系統動態特性也有較快的響應。此外，基於d-q同步旋轉座標下建立離散時間數學模型來分析模式預測控制器與重複控制器的參數挑選對於整體系統的穩定性、誤差收斂速度及穩態誤差特性有何影響。 本文除了介紹控制器的參數設計方法外，並於不平衡負載、非線性負載及各種換載條件下來測試PCC(Point of Common Coupling)點電壓的命令追蹤能力。由模擬結果發現，不僅在動態追蹤行為上有令人滿意的結果，在穩態追蹤能力也相當出色。並於相關參數的變動下針對系統補償結果來做討論。因此結合模式預測控制和重複控制的複合控制法對於電壓不平衡率及電壓總諧波失真率改善效果顯著。此控制策略透過Matlab/Simulink模擬環境下實現，驗證所提出的理論分析與控制器設計之可行性。
並列摘要
Under the isolated microgrid, the output voltage of the inverter is influenced by different load conditions; further, the unbalanced load and the nonlinear load affect the output voltage of the inverter significantly. In order to mitigate voltage unbalance rate and improve total harmonic distortion (THD) caused by the unbalanced loads under the existing converter structure, this thesis not only applies model predictive control on inner current control loop to improve the dynamic response, but also performs the repetitive control on the outer loop to improve THD. Besides, the discrete model for analyzing effect of the predictive controller and repetitive controller are constructed to prove the stability of the system. The proposed control strategy is performed by Simulink; moreover, the presented theory are also verified by different simulations such as unbalanced loads, nonlinear loads and switching loads.