Key Technologies Of Efficiency Improvement For High Efficiency Permanent Magnet Synchronous Motor Control System In Aircraft

The high performance batteries,high efficiency and high power density permanent magnet synchronous motor devices and high efficiency propellers have been main power sources solutions for near-space-craft.The improvement of the power density and operation efficiency of PMSM drive system will significantly affect the quality,payload and endurance time of near-space-craft.The accurate calculation method of motor loss and drive loss is the premise and foundation of system loss optimization technology.The efficiency optimization control strategy under the coupling of motor and drive loss is the difficulty and key to system efficiency improvement.The conventional efficiency optimization strategies for PMSM drive system always ignore the coupling relationship between the motor and the inverter,and only consider the individual optimization of the partial loss in the system.These strategies do not focus on the influence of the special temperature environment(-70? ?70?)in the adjacent space on the internal parameters of the drive system.These will serious affect the efficiency optimization performance of the PMSM drive system,which can only achieve the optimization of the system loss under a certain working condition.The conventional efficiency optimization strategies can not meet the needs of the system efficiency improvement among the whole working condition range in the near space.Therefore,this paper takes the electric propulsion system of the aircraft in the extreme environment of the near space as the application background,and carries out research on the modeling method of the full frequency domain loss of the PMSM drive system.This paper focuses on the studies the efficiency improvement control strategy of the motor drive system,which can broaden the application range of PMSM system in the near space.In order to realize the accurate loss calculation of power device in the extreme environment of the near space,this paper creats a semi-physical model of SiC MOSFET static parameters by the semiconductor physics theory,and baded on the semi-physical model,it takes research on the SiC MOSFET loss parameter calculation method in the near space.This paper applies the semiconductor physics theory to analyze the influence of the near-space environment on the characteristics of SiC materials.Based on the structural characteristics of the planar SiC MOSFET,it studies the semi-physical model of the SiC MOSFET parameters,and deeply analyze the changing rules of the SiC MOSFET internal parameters in the near-space environment.On the basis of semiphysical model,a parametric loss calculation method of SiC MOSFET is proposed,which is suitable for the limit conditions of the near space.This mathod can improve the precise calculation of inverter loss in the PMSM system.In order to improve the inverter efficiency,this paper proposes a linear and smoothed normalized minimum switching loss DPWM algorithm,and studies the inverter loss calculation method which can considers about the internal parameter disturbance of the power element and improve calculation accuracy of the inverter loss in the near space.Firstly,according to the topological structure characteristics of the three-phase halfbridge circuit,this paper analyzes the allowed clamping area of each bridge,and then proposed a normalized minimum switching loss DPWM algorithm.The proposed DPWM can calculate the zero-vector by the the two-stage compound modulation algorithm for clamping arm.The current in the clamping bridge is alwats kept at the maximum value by adjusting the injected zero vector.The porposed DPWM algorithm can overcome the the motor power factor angle limit in the traditional minimum switching loss modulation.On this basis,this paper bulids a parameterized inverter loss calculation method for a wide temperature range.This mathod can improve the accuracy of inverter loss model within the internal parameter disturbance in the limit working condition of the near space.To improve the motor efficiency in the limit working conditions of the near space,thsi paper creats a parameterized analytical calculation method for the motor stator loss and rotor eddy current loss.And based on the motor loss model,an efficiency optimization control strategy suitable for a wide temperature range is proposed in this paper,which can solve that the traditional control strategies can not achieve the optimal loss in the near space.This paper analyzes the changes of the internal material characteristics in the near space,and builds a parameterized calculation model of the iron loss by the agnetic circuit method,which can weaken the impact of the motor parameter disturbance on the stator iron loss calculation.This paper analyzes theeddy current loss caused by tooth harmonics and armature reaction respectively,and propose a calculation method of eddy current loss by the combination of field and circuit..The eddy current loss equation can intuitively characterize the influence of environmental parameters and operating conditions on the rotor eddy current loss.Based on the PMSM loss model,this paper proposes a motor efficiency optimization control strategy suitable for the near space.The analytical method is applied to solve the loss minimization condition.The proposed strategy can comprehensively optimize the stator loss and iron loss,and achieve beter motor performance in the near space.In order to further optimize the loss of the PMSM drive system in the near space,this paper proposes the maximum efficiency per current control strategy based on the wholefrequency-domain loss model to improve the operation system efficiency in the full working range.Firstly,the output voltage spectrum of the inverter under the normalized minimum switching loss modulation is analyzed by the method of double Fourier integration to overcome the limitation of the traditional fast Fourier decomposition on the modulation carrier ratio to an integer.Secondly,the harmonic loss of PMSM is studied in the harmonic dq axis coordinate system.After analyzing the skin effect on the stator winding and the stator core,a parameterized equation is applied to directly calculate the harmonic motor loss under the coupling relationship between PMSM and inverter.On the basis of harmonic loss model,a whole-frequency-domain loss model of PMSM drive system is constructed to realize the accurate calculation system loss under the operation conditions of the near space.Based on the whole-frequency-domain system loss model,this paper proposes the maximum efficiency per current control strategy,which solves the loss minimization condition in two stages and basically achieve the decoupling of the system loss.By comprehensively adjusting the current and modulation frequency,the maximum efficiency per current control strategy can achieve the global optimization of the fundamental motor loss,harmonic motor loss and inverter loss,which can suppress the influence of the internal parameter perturbation on the system performance.The proposed control strategy can maximize the operation efficiency of PMSM drive system in the near space.