不平衡三相類Z源換流器之二倍市電頻電流漣波消除控制

Abstract

本論文提出應用於三相類Z源換流器之二倍市電頻電流漣波消除控制。三相類Z源換流器具有單級降壓升壓的輸出能力，所以很適合用來做為太陽能系統或儲能系統和交流電網之間的直流-交流換流器。然而當電網發生故障時，因電壓不平衡會造成三相輸出電流不平衡且有諧波成分產生，也會有二倍市電頻的震盪反映在直流電流和輸入功率上。在不平衡狀況下，傳統三相換流器架構，透過正序和負序控制可以降低諧波成分提高功率因數，但無法同時實現平衡三相電流和消除二倍頻輸入電流漣波，即只能在「平衡三相電流控制」和「消除二倍頻輸入電流漣波控制」，兩者擇一使用或交替使用。為了改善此情況，本論文提出基於類Z源換流器之不平衡控制方法，來達成同時實現「平衡三相電流」和「消除二倍頻輸入電流漣波」，即本論文所提出之二倍市電頻電流漣波消除控制。本論文提出之控制策略經過電腦模擬驗證，且實際研製一組3kW之類Z源換流器原型機來進行實作驗證。

In this thesis, a novel double-line-frequency current ripple cancellation control for the three-phase quasi-Z-source inverter (qZSI) is proposed. The qZSI has the single stage DC/AC conversion with buck-boost capability, which is good for the application of the grid-connected photovoltaic (PV) power system or energy storage system. However, when the grid voltage sag occurs, the three-phase output current become unbalanced and containing harmonic components. Also, the input current and power will have double-line-frequency ripple. Under the unbalanced situation, the conventional three-phase inverter with the positive-sequence and negative-sequence control can reduce the harmonic components to improve the power factor. But it can not achieve the balanced three-phase current and eliminate double-line-frequency input current ripple at the same time. In order to solve the problem, a double-line-frequency current ripple cancellation control strategy for qZSI under unbalanced condition is proposed. It can achieve three-phase output current balancing and double-line-frequency input current ripple cancelation simultaneously. In this thesis, operation principle of the qZSI under unbalanced grid voltage is first introduced. Then, the mathematical derivation of the proposed control method is presented. Both computer simulations and hardware experimental results of a 3kW phototype circuit are presented to verify the performance of qZSI with the proposed double-line-frequency current ripple cancellation control.