Research On Control Parameters Estimation And Control Strategy For IPMSM In HEV Application

As a significant form of new energy vehicles deemed as the trend of vehicledevelopment, hybrid electric vehicle (HEV) requires excellent characteristics of the drivingmotor to fulfill the optimization of whole vehicle performance match of the HEVs. Withhigh efficiency, high power density, wide constant power range and some other advantages,interior permanent magnet synchronous motor (IPMSM) is the priority for the HEVs.Compared with the motors for industry use, there are some control requirements asaccuracy, high efficiency and high reliability for the HEVs. Since the parameters of IPMSMare easily affected by the temperature, magnetic saturation and some other factors in poorconditions and a large load mutation, the control parameters of the driving motor changesgreatly and irregularly, increasing the difficulty of accurate and efficient control. Thepermanent magnets of the IPMSM make the motor reaching saturation voltage easily,which impacts the rapid response of the motor. As the Automotive facilities with highvoltage and current, the reliability of the motor controller influences driving safety of theHEVs directly, and the IGBT is the most important as well as the most vulnerable device inthe motor controller. Aiming at the control requirements for the driving motor using byHEVs, the parameters estimation matching, flux weakening control, IGBT protection andopen-circuit fault diagnostics of the IPMSM driving system are studied in the paper.First, based on the mathematical model of IPMSM built in this paper, both the kindsloss of IPMSM and the acquisition circuit of the crucial current signal have been analyzed.According to the phase-shift rule, zero position calibration strategy of rotary transformer isproposed combining the comparison of counter electromotive force and zero torquedetermination based on phase-shift characteristic of current acquiring. A current regulatorcontaining of feed-forward decoupling and desaturation is designed to improve the currentresponse speed as well as to restrain integral saturation effect. The self-correcting control ofcurrent PI regulator based on fuzzy logic has also been adopted for the self-adaption of thecurrent regulator parameters at different working conditions.Second, variable parameter maximum torque per ampere (MTPA) control strategy,integrating off-line measured value and on-line parameter prediction, is put forward to ensure the efficiently accurate control of IPMSM. In this strategy, loss parameters ofIPMSM is obtained through off-line measurement in steady state and d-axis inductance isfitted based on experiment curve; the on-line parameter estimation algorithm is composedof flux linkage estimation algorithm based on integration element of current regulator,ensuring the calculation of transient items. And L estimation algorithm (difference of d-qaxis inductance) based on the close loop power control guarantees the precise prediction ofparameters and IPMSM control. Control model of IPMSM is built in Matlab/Simulink, forthe simulation of the strategy proposed. The effectiveness of the approach is verified byboth the simulation and experiment result.For another, a high-speed response field-weakening control strategy is proposed on thebasis of over-modulating current compensation. This strategy integrates the typical outervoltage field-weakening control and over-modulation algorithm to run on the maximumlinear modulation instead of over-modulation in field-weakening conditions, avoiding theharmonics of current and torque and availing the operating efficiency. The high-speedresponse have been achieved by introducing over-modulation field-weakening current ininstantaneous conditions. Simulation and experiment result shows that the output voltagecan be maintained at the maximum linear modulation region and the responding speed is upto15ms, which verifies the high operation efficiency and high responding speed.Last, a controller open-circuit fault diagnosis method on the basis of three phasecurrent deviation and variable element moving average method is present dealing with thefault protection of IGBT, applying the average value of the difference value between actualthree-phase current value and referential three-phase current in one cycle as diagnosisparameter. With the purpose of the decrease of interference resulting from load disturbanceand power variation, normalization method is adopted to normalize the mean value of d-qaxis current amplitude and variable parameters moving average method is also used torealize the period average. The responding speed has been demonstrated through bothsimulation analysis and experiment result, which is less than half electric period.Both the software and hardware system of motor controller and basic debuggingplatform are designed. The motor test bench and hybrid power system test bench are alsobuilt to measure the control precision of motor and the efficiency of the electric drivingsystem. The speed governing process during shifting of hybrid power system has also beentested in the field-weakening work condition of IPMSM, which certify the validity of thesealgorithms proposed in this paper.