축전지 전원을 사용한 소형 선박 추진용 PMSM 구동 시스템의 운전 제어에 관한 연구

Abstract

This study deals with the development of the electric motor driving system for a small ship propulsion powered by DC battery source. And it can be evaluated as part of an intensified effort to reduce carbon dioxide emission, leading to development of greenship technology in the future. Assuming that application to small ship for special purposes such as leisure boats, working vessels in coastal zone and inland, this dissertation will address on designing various components for electric motor driving system which depends on battery source. Electric propulsion system like this method can save navigation cost comparing to existing diesel engine propulsion system. It is known that the whole world is becoming environmentally conscious as enough damage has been caused due to careless ways in using fuel oil. This amazing design concept for maritime transportation systems would help in protecting our environment significantly. Owing to its simple construction, more stronger and low cost performance, the induction motor has been used as the prime mover in most ship's electric propulsion system. However, its efficiency at low speed region is generally low, and also it has disadvantage in the power factor due to heat loss of rotor. To enhance the efficiency and power factor, adoption of the permanent magnet synchronous motor is possible for high speed operations. More recently, there is a growing tendency to use the PMSM as prime mover for electric propulsion system. In this study, after establishing motor experimental system, then some operating characteristics and energy efficiency issues have been investigated together with batteries. Through some experimental comparisons and analyses, it will be confirmed that the BLDC motor is more suitable as the prime mover than induction motor. Next, some comparisons are performed on operation characteristics and energy efficiency of the BLDC motor system driven by two different types of power conversion methods using same battery source. As a result, direct power conversion method is more superior to indirect power conversion in view of electrical energy saving. And, this study proposed an estimating approach of ship operating performances such as total navigation distance and speed from basic voltage discharge characteristics of batteries. Finally, it is carried out basic studies on which control method is more proper for vector control scheme on PMSM driving system. In classic vector control, some coordinate transformations are inevitable to build up the d-q reference model; it is a kind of drawbacks to accomplish low cost operation and simple design because of complicated arithmetic computation and tremendous coordinate transformations. Thus, this study suggested the simplified control scheme which has to be reduced computing process. Through extensive simulation results, it is cleared that the suggested algorithm can provide same control performances as the classic vector control. Also, this paper analyzed the Vdc drop problem of inverter DC link voltage and investigated some compensation methods for controlling the PMSM system efficiently. Detailed theoretical analysis and simulation results show that the new compensation method for the Vdc drop is suggested using the simplified vector control scheme for PMSM. In addition, the method will be used in the open-loop control of PMSM system. If the DC link voltage is dropped within allowable range in the open-loop, it can be compensated by adjusting K. Moreover a limitation for compensating voltage drop is conveniently cleared. Also it is confirmed that the voltage drop can be compensated without adjusting K in the closed-loop because of feedback loop of electric current within allowable range. It is expected that the whole research results can be used as useful data for the design of the PMSM driving system for small ship propulsion based on DC battery source.