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Research On PMSM DTC Electric Propulsion System Based On 7-level Inverter

Posted on:2012-04-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:N QiuFull Text:PDF
GTID:1112330368980562Subject:Marine Engineering
Abstract/Summary:PDF Full Text Request
Ship electric propulsion technology has the advantages of improving performance of ship propulsion, reducing noise and vibration and improving fuel efficiency, and has become the primary propulsion scheme for high-performance ship design. Large AC motor has an important position in ship electric propulsion system. Especially PMSM has many advantages over other motors such as:high power, small volume, high power density, high efficiency, high power factor. PMSM is selected as the primary propelling motor for the high-performance ship propulsion system. In diving state, electric power is from the battery, not sufficient enough. So electric propulsion system for a deep-diving vessel is more critical, for example better efficiency, lower noise, smaller volume. For deep-diving vessel single charge voyage range must be longer without being detected. According to the demand, PMSM DTC electric propulsion system based on 7-level inverter is proposed in this article, study is carried out, achievement is gained listed below:A high power high efficiency high frequency DC/DC converter is designed in order to provide separate DC supply for 7-level cascaded inverter.The proposed DC/DC converter takes the place of traditional phase shift transformer.Not only the DC bus level is raised but also each DC supply is isolated.High frequency DC/DC converter cut off the volume of the input transformer. At the same time soft switching can raise the efficiency of the DC/DC converter.Experimental results indicate proposed DC/DC converter has good performance.Due to 7-level medium voltage cascaded inverter, based on traditional 60 degree coordinates SVPWM methodology, an improved switching states filtration method is proposed. A induced form is selected to filtrate the redundant switching states.And six segment PWM method is used to generate the control signal and control the switching device of the cascaded inverter.The proposed algorithm cut down the system losses due to reducing switching transition. At the same time, complicated judgements are eliminated, scheme becomes concise, and applicable for digital realization. Experimental result approves of the proposed scheme's effectiveness.A PMSM DTC system is constructed based on 7-level cascaded inverter and proposed improved SVPWM method. Compared with basic DTC,7-level inverter system can reduce torque ripple,vibration and niose.At the same time system volume is raised.The proposed scheme is very suitable for large volume electric ship propulsion system,especially suitable for deep-diving vessel to reduce noise and raise invisibility when diving.Experimental results prove that the scheme is valid and effective.
Keywords/Search Tags:multilevel inverter, cascaded inverter, SVPWM, redundant switching states filtration
PDF Full Text Request
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