併網太陽能換流器之直流鏈電壓雙階控制策略

DC-Link Voltage Dual-Level Control Strategy for Grid-Tied PV Inverters

楊承臻(Cheng-Jhen Yang)

指導教授 ： 陳耀銘

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201803701

摘要

本論文提出一種應用於併網太陽能換流器的自主式直流鏈電壓控制策略，目的在於解決當電網電壓驟降致使前後級電路功率不對等之問題，並能讓併網太陽能換流器在電網電壓驟降情況下持續正常的運作。當電網電壓驟降時，由於後級之換流器可能會因為線電流之最大額定電流限制導致其最大輸出功率受限，嚴重時將導致其失去穩定電容鏈電壓之能力。在此情況下，前級之轉換器則必須放棄其最大功率追蹤之操作模式來幫助穩定電容電壓。然而，欲達到此目的，則必須在前後級電路間建立起通訊機制，以達成正確的操作模式切換。不過，如此一來將會提升整體電路的複雜度及額外成本，同時，電路的可擴展性也會隨之而降低，除此之外，在通訊機制中的雜訊干擾更可能會降低整體電路之可靠度。
為了避免上述所提到的缺點，本論文新提出不需要通訊機制的直流鏈電壓雙階控制策略。在此控制策略中，直流鏈電壓將會被控制在不同的電壓準位中，而太陽能換流器的前級轉換器將能自動依據此時的直流鏈電壓大小值，來決定是否需要改變自身的操作模式。因為是自主式操作，因此不需要外加元件或是修改電路便能實現此控制策略。本論文將會詳細介紹並說明直流鏈電壓雙階控制策略之操作原理與數學公式推導，並且將會藉由電腦模擬以及一組三相4kVA原型機的實驗結果來驗證此控制策略之可行性與表現。

關鍵字

併網太陽能換流器 ； 電網電壓驟降 ； 功率不平衡 ； 直流鏈電壓控制

並列摘要

An autonomous control strategy, named DC-Link Voltage Dual-Level Control Strategy (DDLC), is proposed in this thesis to solve the power flow imbalance problem of the grid-tied PV inverter during grid voltage sags. When a grid voltage sag occurs, the rear-end inverter may lose the ability to regulate the dc-link voltage due to the limitation of the rated output current. Under this condition, the front-end converter should abandon the Maximum Power Point Tracking (MPPT) function to help to regulate the dc-link voltage. As a result, the communication scheme between the two-stage circuits must be established. However, the communication scheme may increase the cost and circuit complexity and further reduce the scalability and the flexibility. Also, the reliability of the PV inverter may also be reduced due to noise interference problem.
To avoid these drawbacks, an autonomous DDLC strategy is proposed. The dc-link voltage is controlled within two different levels and the operation mode of the front-end converter can be automatically changed according to the dc-link voltage value. Besides, to realize the proposed DDLC strategy, no extra sensors or devices are required. Details of the operation principle and the mathematical derivations are provided in this thesis. The simulations and experimental results of a three-phase 4 kVA prototype circuit are also presented to validate the performance of the proposed DDLC strategy.

並列關鍵字

grid-tied PV inverter ； grid voltage sag ； power imbalance ； dc-link voltage control

參考文獻

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