Six-phase Synchronism Motor Control System For The Ship Electric Propulsion

Ship electric propulsion is an advanced way of propulsion, which has achieved unprecedentedly prosperity in the resent decades. The control technique of propulsion motor is one of the key technologies of ship electric propulsion. The ship electric propulsion system is composed of propulsion motor, inverter of propulsion motor, ship propeller and control devices. The ship electric propulsion system that we are going to discuss consists of the following parts: six-phase double Y winding shifted by 30°synchronous motor, diode clamped three-level inverter, fixed pitch propeller and control installment of electric propulsion systems based on air-gap-field orientation vector control.This subject derives from the construction of national key laboratory on ship integrated electric power technology and simulation research on ship electric propulsion system.After comprehensive analysis of the researches and development about ship electric propulsion system from both domestic and foreign, this paper introduces a deep discussion about ship electric propulsion system, putting much emphasize on control strategies of three level multi-phase electrically excited synchronous motor and its ship electric propulsion system. And also some improvement measures are come up to the problems in the control system. The contents are as follows.In order to investigate high harmonics and electromagnetic relationship of multi-phase motor, the mathematical model of multi-phase electrically excited synchronous motor is used in the dq rotating coordinate system based on Park transform. A universal simplified model for multi-phase motor is proposed. A simulation research is conducted on the example of six-phase double star winding shifted by 30°synchronous motor.In order to investigate the control algorithm of multilevel inverter , high harmonics as well as its problems, a mathematical model of the control algorithm based on the voltage space vector is built. For the first time, the principle along boundary is introduced to confirm the chosen switch state when many switch states are corresponding to the same vector. Simulation analysis and hardware realization are conducted with the combination of diode clamped three-level inverter and five-level inverter.In accordance with the characteristics of electrically excited six-phase synchronous motor, the control system based on air-gap-field orientation vector control is adopted in this paper. The mathematical models of every stage in the vector control are built. A voltage feed-forward method is used to realize the independent control of the current in the MT shaft. On the basis of simplified models, the controlling parameters of the adjuster are gained through engineering design method. A flux observer of six-phase motor is designed based on the flux observer of three-phase electrically excited synchronous motor. According to the advantages and disadvantages of flux observing method, this paper adopts a mixed voltage-current model as the flux observer model. In order to make the vector control method based on non-salient pole synchronous motor fit for salient pole synchronous motor, the equivalent mathematical model of non-salient pole motor is gained after the equivalent substitute of salient pole motor with the theory of two reaction theory of synchronous motor. Simulation research is conducted on the performance of six-phase electrically excited synchronous motor control system based on gap motor flux oriented vector control.According to the study of ship propeller load, a motion model of integrative model of the ship and propeller is built on the basis of propeller properties across four quadrants and the interaction between the propeller and ship. Relative simulation study is done.In view of the uncertain load disturbances and parameter variations and so on, the disturbance restraint performance of the six-phase synchronism motor control system for the ship electric propulsion is improved under the robust control theory. The propeller load, disturbance of current and wave on the sea are treated as load disturbance in this paper, and the field influence is treated as a kind of parameter variation. Then a closed-loop motion model of speed is set up in the ship electric propulsion system only considering the torque current component. The design of H_∞controller in the ship electric propulsion system is summed up as the problem of mixed sensitivity. According to the uncertainty analysis of the model, a weighed function is chosen and a generalized mathematical model of the marine electric propulsion system is established .The transfer function of H_∞controller is gained by virtue of solving the "2-Riccati" equation. Simulation result proves that the designed robust controllor has improved the robustness of the electric propulsion system, and successfully solve the problem of disturbance resistance and parameter variation in the ship electric propulsion system.