Research On Electrolytic Capacitor-less Motor Drive System With Tiny Boost Converter

Permanent magnet synchronous motor(PMSM)is widely applied in various kinds of VF speed control system.It is because that PMSM has advantages of simple control algorithms and high power density.In home appliance area,PMSM is usually used in single-phase power supply system,namely,the dc-voltage of inverter and motor side is rectified from single-phase ac power supply.A bulk dc-link capacitor is necessary to stabilize bus voltage.Nevertheless,electrolytic capacitor has demerits of short lifetime,instability,capacitance error and leakage current.As a result,this paper introduces an electrolytic capacitor-less power decoupling circuit,which aims to decouple the power between grid side and motor side.In addition,the replacement of electrolytic capacitors may cause dc-link voltage fluctuating as twice the grid frequency.To solve this problem,this paper proposes an active damp control strategy.This paper consists of following parts:Firstly,the meaning and background of this research is discussed.Then,the fundamental principle of PMSM is introduced,which includes PMSM mathematical models,coordinate transformations,field-orientated control and SVPWM algorithm.On this basis,the characteristics of electrolytic capacitor-less driving system are analyzed and power balance equation is derived.According to theoretical analysis,the 100 Hz fluctuation caused by small dc-link capacitor brings disturbances to the motor side.Secondly,according to above research,this paper introduces a novel electrolytic capacitor-less power decoupling circuit,which applied in PMSM driving system.The voltage gain of this circuit is approximate to one and the new one overcomes the shortages of existing power decoupling circuits.Simultaneously,the structure and operating modes are presented.Then,the parameters of passive components are derived.In the third part,a predictive control strategy is applied in this topology,compared to traditional circuit,grid voltage and current are sampled and calculated to get the control signal.It has advantages of low current harmonic and high speed response.Additionally,an active damping control method is proposed to lower the torque ripple.In this strategy,the machine winding acts as passive component to absorb the fluctuated energy.Finally,based on theoretical analysis and simulation results,the experimental platform on account of TMS320F28335 is built to verify the feasibility and effectiveness of the proposed electrolytic capacitor-less driving system.