船舶馬達啟動引起電壓驟降之模擬分析

Simulations of Voltage Sag in Ships Due to Motor Starting

電壓驟降是指電壓有效值在短時間減少的現象，在船上多數起因於大型馬達啟動，容易使敏感性負載，如電腦、程控設備、可調速驅動器等產生誤動作或功能失靈。為能有效地評估因船上馬達啟動引起的電壓驟降現象，本文推導電壓驟降數學模型，並建構船舶主要電力設備動態數學模型，利用動態模擬技術分析船舶電力系統動態、運轉行為，以完整呈現電壓驟降過程，包括電壓驟降大小及持續時間。測試對象以一艘發電裝置容量為9.6MW之貨櫃輪，進行不同馬達啟動狀況，包括群集式冷凍壓縮機、船艏側推進器、舵機馬達之電壓驟降實例分析，並與解析法比較。測試結果已顯示本文所提出的方法與解析法之計算誤差均在2%內，可有效地分析船上馬達啟動引起的電壓驟降問題，以協助工程師決定適當的供電品質改善設備或馬達啟動方案。 Voltage sag that is a short-duration reduction in rms voltage is usually caused by the starting of large or grouping motors in shipboard electric power systems and easily causes sensitive loads such as computers, process control devices and adjustable speed driver to misoperate or malfunction. To effectively assess the voltage sags in shipboards due to motor starting, a dynamic simulation method is proposed in this paper. A mathematical model of the voltage sags is derived. The dynamic mathematical models of several vital shipboard electric power equipments are developed and the dynamic behavior of the power system is analyzed by using the proposed method to present the change of the voltage sag including magnitude and duration. Voltage sags due to motors starting including grouping reefer containers, bow thruster, and steering pumps in a practical container vessel with a total generation capacity of 9.6 MW are analyzed by using the proposed method and the results are compared with those obtained from the analytical method. Using the results obtained from the analytical method as a basis, the calculation errors for the maximum voltage sags are within 2% for the proposed method. Test results have indicated that the proposed method could effectively analyze the voltage sag problem and assist engineers in deciding suitable mitigation devices or motor starting options for maintaining supply quality.