| The permanent magnet synchronous machine(PMSM)is widely used in the electric drive system of electric vehicle(EV)because of the high power density,high efficiency and wide speed range.The safety is the primary object in EVs,so the reliability of PMSM and its driving system has become a research hotspot in recent years.The sensorless control of PMSM is an important part of the reliability research in the electric driving system,in addition to which the realization of sensorless control is also of great significance to reduce the cost and the volume for EVs.The research of the sensorless algorithm has been studied for nearly 50 years,among which the sensorless algorithms based on back electromotive force(EMF)or flux observer are mature and successfully commercialized.Howerer these methods are only suitable for the operation at medium and high speed and may fail at zero-start and low-speed operation.Although high frequency injection(HFI)technique which is based on the salient-tracking principle has been proved to be an effective method to achieve low and zero-speed sensorless operation,there are still many problems to be solved.In this thesis,the HFI sensorless control algorithm is studied by taking a new five-phase fault-tolerant fractional-slot concentrated winding interior permanent magnet(FTFSCW-IPM)machine as the research object.The main research contents of this thesis include the following aspects:1.The basic structure and electromagnetic characteristics of this FTFSCW-IPM motor are introduced.Then the mathematical model of the motor is established and the space vector modulation strategy(SVPWM)suitable for this five-phase FTFSCW-IPM motot drive system is studied.In addition,the vector control with position sensor is introduced,and the parameters of the speed and current regulators are designed in the discrete-time domain through the analysis of the control system‘s transfer function.2.The sources of the magnetic saliency inside a PMSM are analyzedfrom the view of magnetic circuit,and the mathematical model of the machine based on incremental inductance is established considering the nonlinearity of magnetic circuit.Then the position estimation principle of high frequency square wave voltage injection is analyzed,and an effective signal separation strategy is given based on the deliberate design of the time-sequence between the injected high frequency voltage and fundamental voltage from current regulator.Finally,a methodology to select the appropriate high-frequency voltage amplitude and frequency for rotor position estimation is described.3.The initial rotor position detection based on high frequency square wave injection is studied,and the magnetic polarity is identified by injecting fundamental current into the estimated d axis.In addition,the transfer functions of PI-type and PID-type PLL are analyzed and both parameter design methods are proposed.4.The position estimation error of the PLL observer is analyzed and it is found that two reasons can account for the estimation error,one is discrete control characteristics under digital processor,the caused estimation error of which is related to the velocity,and the other is the influence of cross-saturation inductance,which can cause the error varying with load current.In this thesis,an optimized time-sequence is proposed to eliminate the estimation error caused by the first one,and the online look-up table(LUT)compensation strategy based on offline measurement of estimation error is adopted to solve the cross saturation effect.5.The simulation model of the drive control system of the FTFSCW-IPM motor is built under the MATLAB/Simulink platform,and the theory is verified by simulation.The hardware of the five-phase drive system including the main power circuit,sampling circuit and encoder processing circuit are designed and manufactured.Finally,based on digital signal processor TMS320F28335,experiments are conducted to verify the feasibility and effectiveness of the studied theory. |
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