Research On Control Methods Of Permanent Magnet Synchronous Motor Driven By Quasi-Z-Source Inverter

Adopting quasi-Z-source inverter(q ZSI)to supply the permanent magnet synchronous motor(PMSM)contributes to better performance and higher reliability of drive systems.This dissertation is dedicated to exploring q ZSI-PMSM system's novel control methods to promote deeper integration of q ZSI's exclusive features and PMSM's operation characteristics and make them complementary to each other.First of all,mathematic models of q ZSI and PMSM are estabilished and steady and transient operation features of q ZSI are analyzed.Then researches are made on the problems existing in conventional variable dc-link voltage control method,single current sensor control method and sensorless flying restart control method of PMSM system and possibility to overcome these limitations by taking advantages of q ZSI's exclusive features are pointed out.As to the variable dc-link voltage control method,a PI-style regulator is utilized to control the minimum value of zero vector's duty cycle in a fundamental wave cycle to be zero.This helps to indirectly adjust the amplitude of dc-link voltage,which can meet the requirement of PMSM's normal operation,to be minimized.The method can get rid of the dependence on realtime measurement of input voltage and avoid requirement for a large margin index of dc-link voltage due to simplified modeling of q ZSI which is hard to be accurate.With the proposed method,the cost of the drive system tends to be lower and its operation efficiency is expected to be higher.As to the single current sensor control method,the sum of two branch currents in the inverter bridge is selected as the sampling target and a new way to perform the current sampling under the action of shoot-through vector is explored to reconstruct the three-phase currents.On the basis,a modulation strategy for q ZSI which features shoot-through of double arms is customized for the benefit of single current sensor's sampling.Besides,a switch-over mechanism of sampling methods and matched modulation strategies is supplemented.The novel single current sensor control method can totally eliminate current measurement's dead zone and overcome the limitation on utilization rate of the input voltage accordingly.As to the sensorless flying restart control method,the shoot-thorough vector's dual attributes are made full use of by substituting part or all of the zero vectors in the conventional double zero vector short-circuit method with shoot-thorugh vectors to pre-boost the dc-link voltage during the process to estimate initial motor speed and rotor position of sensorless PMSM before flying restart.Accordignly,the period from the power supply's recover to the instant when the electromagnetic torque reaches its reference value for the first time can be effectively shortened.With the proposed method,not only the q ZSI-PMSM drive system has got the ability to restart under the condition that the motor is rotating and has no position sensor but also the flying restart process of PMSM gains the advantage of fast torque response.Finally,a prototype is setup to verify the performance of the three proposed control methods for q ZSI-PMSM system and the experimental results shows the three control methods can operate well and have advantages of strong robustness,high system efficiency,full input voltage utilization and fast torque response.