Maximum Torque Per Ampere Control Of DC-biased Hybrid Excitation Machine Based On Virtual Signal Injection

DC-biased Hybrid Excitation Machine(DC-biased HEM)is an emerging type of hybrid excitation machine in recent years,which possesses the characteristics of high torque density and flexible flux modulation,and has good application prospects in traction fields such as electric vehicles.Unlike traditional hybrid excitation machines,DC-biased HEM incorporates the functions of the armature winding and field winding into one set of integrated winding,and the hybrid excitation and torque output can be achieved simultaneously by feeding dc-bias sinusoidal current with zero sequence current into each integrated winding.However,the output torque is generated by the interaction of permanent magnet flux,zero sequence current,and AC current components,making its composition complex.Reasonably adjusting the proportion of AC and DC components in the phase current,fully utilizing the excitation performance of zero sequence current,and achieving efficient torque output are of great research significance.Therefore,based on the basic characteristics of DC-biased HEM,this thesis proposes a MTPA control strategy combining the Maximum Torque Per Ampere(MTPA)control law with virtual dc-bias signal injection method.The MTPA control law is responsible for calculating the main current reference value while ensuring the rapid dynamic response.The virtual dc-bias signal injection method eliminates the cascade filters,taking into account the nonlinearity of the inductance,and corrects the current reference value calculation deviation caused by parameter variations in realtime in the form of compensating for zero-axis current reference.The proposed control strategy aims to achieve high torque output of the DC-biased HEM and improve system operation efficiency.The main contents of this thesis are as follows:1.The basic structure and electromagnetic characteristics of DC-biased HEM are analyzed.The driving topology,driving principle,and modulation strategy of the machine are introduced.The mathematical model of the machine in the commonly used coordinate system are derived.2.The feasibility of applying virtual sinusoidal signal injection MTPA control strategy and virtual square wave signal injection MTPA control strategy to DC-biased HEM is analyzed in detail theoretically.The advantages and disadvantages of both methods are pointed out through simulation results.3.An MTPA control strategy consisted of MTPA control law and virtual dc-bias signal injection method is proposed.The respective roles of MTPA control law and virtual dc-bias signal injection method are elaborated.The effect of the combination of two methods has been verified through simulation and it is proved that the proposed control strategy possesses precise MTPA control accuracy and good performance of dynamic response and resistance to parameter variations.4.The DC-biased HEM experimental platform is established and the software and hardware configurations are briefly outlined.The proposed control strategy is experimentally validated and analyzed on the experimental platform.The experimental results show that the proposed control strategy can be applied to DC-biased HEM.Good dynamic response performance can ensure the flexible flux regulation ability of the machine,accurate MTPA tracking performance is conductive to improve the torque output ability of the machine.