| In this paper,the hybrid power electronics system is studied.Based on the existing researches on the hybrid singals system,the analysis and improvement for the nonlinear problem in hybrid power system are deeply excavated.The combination characteristics and operation mechanism of hybrid power system are explored in various aspests,including the combination characteristics of high-order network,the electromagnetic energy transfer in multi-port impedance network,hybrid pulse sequence control for motor drive,etc.Focusing on the caused constraints and effects,the dynamic characteristics of hybrid system such as high-order oscillation,low damping and harmonic distortion are analyzed.Considering the above factors,three application technologies in the hybrid power electronics system are proposed,including the assembly combination for standard modular units,the active impedance network converter system and the dual-frequency drive for multiphase motor with asymmetric winding structures.Then the design and performance improvement methods get summarized for the combination and expansion of hybrid power electronics system.The reseaches are validated by the experiments on various types and power levels of platforms,so that the practical application of the proposed theoretical study on the hybrid power electronics system gets realized.The busbar and the dc-link capacitor in the current converging part of the modular converter form the potential parasitic impedance network.This will lead to the resonant modes in high-order hybrid impedance network and electrical stress,which causes problem such as insulation and thermal breakdown.In addition to the previous method of finding the optimal parameters through experiments and iterations,this paper proposed a forward design and evaluation method for largesize dc-link busbar network structure.Firstly,the admittance parameter matrix for the subnetwork of each component in the dc-link is constructed to obtain the system combination characteristics.The multi-peak resonance phenomenon caused by the interaction of the subnetworks gets revealed.Then,aiming at the difficulty of the non-sinusoidal dc-link current analysis,the transfer function matrix is combined with the positive and negative sequence decomposition method to deduce the transfer function for each sequence current and the exact subnetwork current.Finally,based on the above theory,the forward design of the dc-link busbar structure is proposed,and the simulation and field experimental verification are carried out around the 315 k W photovoltaic system.The results show that with the proposed design method,the estimated values of resonant current in dclink busbar are in good agreement with the experimental results.The effective value of the resanont current gets reduced by 49% mostly and reaches the effect of laminated busbar.The thermal stress of the capacitor caused by the resonance in the dc-link busbar is successfully resolved.In order to reduce the loss and cost of battery power converter,the method of extending the power transfer and management of the existing passive impedance network converter is explored in this paper.The active impedance network converter with single-stage power conversion is constructed to realize the energy management between motor drive and hybrid energy storage.According to the system poles variation with the energy storage unit embedded,an active damping control method is designed to solve the low damping issue caused by combining energy storage unit with the passive impedance network converter.Then the multi-mode power distribution in the hybrid energy storage impedance network converters gets ensured.Wide range operation of active impedance network system is realized with 40% system loss reduction and two times increment in the current controller bandwidth.The comprehensive control strategy and transient peak value estimation of battery current can effectively avoid the stress caused by current surge.The frequency division coordinated control strategy for power management,which considers the performance requirements of time domain and frequency domain,is proposed to ensure the dynamic response of hybrid energy storage system and the seamless switching of operation modes.Aiming at the torque ripple caused by low carrier ratio for the high power motor drive system,the power distribution and recombination method of multiphase motor winding network is studied,and a multiphase motor drive system based on two sets of diffenernt winding structures is proposed.The circular combination flux in the motor is ensured by injecting high frequency harmonic current into the windings to form the compensation flux and then combining with the the flux of master windings with low carrier ratio.It provides a new way to suppress the torque ripple with low carrier ratio operation.Further studies effectively solve the issues of the influence from mutual inductance between two windings,the design of motor winding network structure and the combination of hybrid pulse sequence for the proposed motor drive.It is found that the proposed motor drive system gains the advantages of actively eliminating torque ripple,vibration noise and torsional vibration from load.Meanwhile,when the same torque ripple requirement is satisfied,the loss of proposed master-slave windings motor drive system can be reduced by about30% compared with the existing three-phase system with high carrier ratio operation. |
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