State-of-the-Art and Future Trends of Zero-Sequence Current Excited Machines:Drive Topology and Control Technologies
A type of zero-sequence current excited machine(ZSCEM)has been proposed recently,in which the functions of excitation/armature winding are integrated.Correspondingly,the DC-biased sinusoidal current is injected into the integrated winding.The DC-biased component is used as an excitation source,and the sinusoidal component is used to drive the machine.The phase resistance and copper consumption are reduced while the overall efficiency is improved since the cross-sectional area of the winding is increased.At the same time,the excellent capability of magnetic field regulation is obtained by regulating the DC-biased component in the phase current.This paper overviews several key issues of the ZSCEM and prospects for its development directions.Firstly,the drive topologies of ZSCEM are summarized,which mainly consist of open-winding/dual three-phase drive topology with common DC bus,open-winding drive topology with common mode connected DC bus,nine-switch drive topology,series-end winding drive topology,and three-phase four-leg drive topology.Besides,since the DC-biased sinusoidal current is injected into ZSCEM,the amplitude of positive and negative currents is different.Therefore,a series of asymmetry drive topologies are proposed and presented to save costs and balance the heat pressure.Secondly,the modulation strategies for the above drive topologies are mainly summarized,including different space vector modulation(SVM)strategy and sinusoidal pulse width modulation(SPWM)schemes.Moreover,the basic voltage vector distribution and linear modulation region are carried out for each drive topology of ZSCEM.Therefore,it can be easily seen the zero-sequence modulation region from three-dimension space.Thirdly,the control methods,such as vector control,direct torque control,and fault-tolerant control,are presented.The introduction of zero-sequence current can add one degree of freedom to control technologies.Therefore,the zero-sequence current control loop should be added to the vector control strategy,and a new look-up table with a zero-sequence component should be revised in direct torque control.Furthermore,since the drive topology of ZSCEM provides a zero-sequence loop,the number of power switches is increased,which brings excellent fault tolerance to the ZSCEM drive topology.The existing fault-tolerant control methods(directly driving in post-fault operation and driving after drive topology reconstitution)are also carried out.Then,the above drive topologies and their basic performances are compared regarding basic constructure,modulation ability,and control ability.Moreover,several modulation strategies are carried out.Different drive topologies have different advantages and disadvantages,which can be selected according to actual situation requirements.Furthermore,the concept of integrated winding is extended to the memory machine.Therefore,this paper proposes a new type of ZSCEM called zero-sequence current magnetized memory machine(ZSCM-MM).The principle of its operation is introduced in detail,and the regulation method for the magnetization state of ZSCE-MM is revealed.During the normal drive operation,the zero-sequence current should be suppressed to zero,while in the magnetization operation,the zero-sequence current should be controlled to the reference value.Finally,further research and application directions are summarized,providing references for in-depth research of the ZSCEM.
Drive topologyhybrid-excitedmachine controlmemory machinevariable fluxzero-sequence current magnetization
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