Research On Control Strategy Of Open Winding Six-Phase Permanent Magnet Synchronous Generator System With Common DC Bus

Open winding permanent magnet synchronous generator system is widely used in high voltage and high power situation with its advantages of high power density and high busbar voltage utilization.According to whether the converter DC bus connected on both sides of the motor winding is connected,the open winding permanent magnet synchronous motor can be divided into common DC bus structure and isolated DC bus structure.Among them,the common DC bus structure has greater potential in the application of new energy field by virtue of its higher power density and lower hardware cost.In this paper,the common DC bus type open winding six-phase permanent magnet synchronous motor system is taken as the object,aiming at the problems of high zero sequence current and high frequency change of common mode voltage in the system,the following work is done to optimize the control strategy of the system:(1)The mathematical model of open winding six-phase permanent magnet synchronous motor in static coordinate system and d-q rotating coordinate system is established,and the zero-axis voltage model under the common bus structure topology of two convertors is analyzed,and the open winding six-phase permanent magnet synchronous motor model is built in Simulink.(2)The zero-sequence current component in the common bus topology is analyzed,and a four-dimensional current modulation method based on 180° space vector decoupling is proposed.The zero-sequence current can be suppressed by using the vector with zero common-mode voltage.(3)The SVPWM modulation method of zero vector redistribution is proposed.Based on the idea of three harmonic cancels of the output voltage and the back potential of the converter,the zero sequence current loop is introduced,and the action time of the zero vector is controlled by the proportional resonance controller,so as to realize the effective suppression of the zero sequence current.On this basis,a simulation model is built to verify and analyze the effect of zero sequence current suppression.(4)Based on the principle of unified voltage modulation,the SVPWM modulation method of vector synchronous compensation is proposed.The proportional resonance controller controls the sum of common-mode voltage of the left and right converters to keep constant,and the difference is equal to the third harmonic back potential,thus controlling the common-mode voltage to keep constant on the basis of effectively suppressing zero sequence current.Finally,the corresponding simulation model is built and verified.(5)The experimental platform of open winding six-phase permanent magnet synchronous motor was built to verify three zero-sequence current suppression methods.