Research On Control Strategy Of DC-biased Vernier Reluctance Machine System

As a key component of electromechanical energy conversion,the motor system is widely used in various fields of the national economy.The research on high performance and high reliability motor drive system has become the key to the high-quality development of the equipment manufacturing industry.In recent years,with the rapid development of power electronics technology and automatic control technology,modern electric drive is no longer limited to the traditional three-phase AC motor system.In some special application occasions,the technical innovation of motor drive system is emerging constantly.Compared with the traditional three-phase AC motor system,the phase current of the DC-biased vernier reluctance machine system contains not only the AC current component,but also superposed with additional DC bias current.This new motor system has the characteristics of low cost,high reliability,simple manufacturing process,good heat dissipation,excellent speed regulation performance.It has a better competitive advantage in aviation starting/power generation,mining machinery,automobile turbocharged motor and other applications where the environment is harsh and the reliability and speed regulation performance are strictly required.In this paper,the DC-biased vernier reluctance machine system is taken as the research object,with the application requirements of high performance and high reliability as the research objective,the control strategy of the system is studied in depth.Firstly,the basic control problems of the DC-biased vernier reluctance machine system are studied,including the system structure,the mathematical model of the motor,the basic operating principle,and the precise decoupling control of each current component,which are the basis of the subsequent high performance and high reliability control strategy.Then,around the additional zero-axis current component of the DC bias vernier reluctance motor system,the optimal distribution of the subspace current components in constant torque region and flux weakening region,the direct torque control(DTC)strategy with zero-axis current regulation ability,and the fault tolerant control strategy for open circuit faults of switching devices are studied comprehensively.The aim is to provide a complete solution for high performance and high reliability speed control of DC-biased vernier reluctance machine system,and enhance China's position in high-end equipment manufacturing industry.The research contents are summarized as follows:Firstly,the research background and significance of this paper are introduced.The development history and research status of DC-biased vernier reluctance machine system are summarized from three aspects of motor body,converter topology and system control strategy.The main research achievements and shortcomings are summarized and analyzed.Aming at the requirement of the synchronous control of DC bias current and AC current in DC-biased vernier reluctance machine system,the precise decoupling control in the synchronous rotation coordinate is studied as the basis of the subsequent high performance and high reliability control strategy.Firstly,the mathematical model of DC-biased vernier reluctance machine considering the zero-axis component is constructed,and the basic operation principle is analyzed.Then,the current loop is optimized to suppress the distortion of current waveform.Then,the modulation strategy based on the zero-axis current regulation is introduced to realize the decoupling control of the subspace current components.On the basis,a current distribution strategy with variable DC/AC current ratio in constant torque region is proposed to improve the output ability of the motor system under the overload condition.Aming at the requirements of wide speed range operation of DC-biased vernier reluctance machine system,the optimal control strategy of the DC bias current in flux weakening region is studied.Firstly,the voltage and current constraint equations considering the zero-axis components are established as the theoretical basis for the optimal control of the DC bias current in flux weakening region.Then,this paper analyzed the limited control freedom of traditional two-dimensional current distribution flux weakending control strategy,and a three-dimensional current distribution flux weakending control strategy is proposed.Through the flexible change of distribution between d axis,q axis and 0 axis current in motor winding,the flux weakening control is realized under the three-dimensional plane,and it improves the output ability within the flux weakening region.On this basis,the influence of inductance nonlinearity on the optimal current distribution is represented by constructing inductance parameter table.The proposed flux weakending control strategy provides an effective solution to optimize the motor performance and realize the high performance speed regulation control of the motor system.Aming at the problem of high power tube failure probability due to the large number of power tubes,affecting the reliability of the system,a fault-tolerant control strategy under the power tube open circuit fault condition is investigated.Firstly,the current stress asymmetry characteristics of the power tube during the normal operation of the system is analyzed,and the influence of the open circuit fault on the system operation is analyzed.Then,a fault-tolerant control strategy based on DC bias current injection is proposed.By using the redundancy characteristics of the power components of the open-winding converter,the topology of the converter in the fault state is reconstructed,and the output ability of the motor is maintained under the fault state by the reallocation of DC bias current.Furthermore,a pulse width modulation(PWM)strategy is investigated to reduce the current ripple in fault-tolerant operation state.The proposed fault-tolerant control strategy realizes the fault-tolerant operation of the motor system under the power tube open circuit fault state without adding additional components,and further improves the reliability of the system.Aming at the target of direct control the torque and flux of DC-biased vernier reluctance machine system,a DTC strategy with zero-axis current regulation ability is invetigated.Firstly,the mathematical model of the motor based on stator field orientation in three-dimensional space is established,and the basic operation principle of DTC is analyzed based on switching table DTC method.Then,a space vector modulation(SVM)based DTC strategy with zero-axis current regulation ability is proposed,and the distribution of zero-axis current relative to the reference torque and reference flux is optimized.On this basis,a simplified reference voltage vector distribution method is proposed,which further reduces the process of rotation coordinate transformation.The proposed SVM-DTC strategy provides a technical solution for the direct control of torque and flux in the motor system with the requirement of zero-axis current regulation,and has the advantages of quick dynamic response,simple control process and strong robustness.Finally,the research achievements and innovation of this paper are summarized,the limitations and deficiencies of the current research work are pointed out,and the development trend of the zero-axis current optimal control strategy of the DC-biased vernier reluctance machine system is prospected.