In compliance with environmental regulations at sea and the introduction of unmanned autonomous ships, electric propulsion ships are garnering significant attention. Induction machines used as propulsion electric motor (PEM) have maintenance advantages, but speed control is very complicated and difficult. One of the most commonly used techniques for speed control is DTC (direct torque control). DTC is simple in the reference frame transformation and the stator flux calculation. Meanwhile, two-level and three-level voltage source inverters (VSI) are predominantly used. The three-level VSI has more flexibility in voltage space vector selection compared to the two-level VSI. In this paper, speed is controlled using the DTC method based on the specifications of the PEM. The speed controller employs a PI controller with anti-windup functionality. In addition, the characteristics of the two-level VSI and three-level VSI are compared under identical conditions. It was confirmed through simulation that proper control of speed and torque has been achieved. In particular, the torque ripple was small and control was possible with a low DC voltage at low speed in the three-level VSI. The study confirmed that the application of DTC, using a three-level VSI, contributes to enhancing the system's response performance.

서 론
재료 및 방법
    직접토크제어
    2레벨 인버터
    3레벨 인버터
결과 및 고찰
결 론
References

• 류기탁(한국해양수산연수원 해양기술교육팀 교수) | Ki-Tak RYU (Professor, Ocean Technology Training Team, Korea Institute of Maritime and Fisheries Technology, Busan 48562, Korea)
• 김종필(한국해양수산연수원 오션폴리텍팀 교수) | Jong-Phil KIM (Professor, Ocean Polytech Team, Korea Institute of Maritime and Fisheries Technology, Busan 48562, Korea)
• 이윤형(한국해양수산연수원 해양기술교육팀 교수) | Yun-Hyung LEE (Professor, Ocean Technology Training Team, Korea Institute of Maritime and Fisheries Technology, Busan 48562, Korea) Corresponding author