Research On Background Harmonic Suppression And Motor Harmonic Simulation Of Electric Machine Emulator On Electric Vehicles

New energy electric system reliability and safety test is one of the new energy.vehicles is crucial,and motor simulator can simulate the real motor electrical characteristics of motor controller power level test,and compared with the mechanical bench testing,motor simulator with repeatable configuration,the working condition of the limit test characteristic,prompting them to more comprehensive and fast testing machine controller verification,greatly shorten the development cycle,become the important link of the motor controller development testing.However,if the motor simulator can completely replace the real motor,it is required to accurately simulate the current characteristics and harmo nic characteristics of the motor.The key to the current harmonic characteristics of the motor simulator lies in the output inverter system and the motor model module.The output inverter system has voltage and current distortion due to the existence of dead zone,voltage drop and other factors,which leads to the existence of harmonic current in the output current.Therefore,it is necessary to suppress the harmonic current in this part.The motor itself has saturation characteristics,harmonic characteristics and cross-coupling characteristics,which requires the motor model to be able to simulate these characteristics,so as to more accurately output the target current and current harmonics.This paper will expand from the following three aspects: the basic design of the motor simulator,the harmonic suppression of the output inverter,and the harmonic simulation of the motor model.First,this paper carries out the basic design of the motor simulator system,builds the realization scheme and deduces the mathematical model of the motor simulator by establishing the simplified topology structure.The current control strategy of the motor simulator is designed and the stability of the system is analyzed.The relations between coupling network inductance and power supply voltage of motor simulator is deduced.Aiming at the harmonic suppression of the output inverter,starting with the voltage distortion of the output inverter,the influence of various factors on the voltage distortion is quantified by the volt-second balance method.On the basis of considering the dead zone,voltage drop,delay and parasitic capacitance,the influence of the midpoint potential is added into the consideration,and the quantitative formula is given.The saturation,cross coupling and the source of harmonic effect of the motor are analyzed,and the 6k harmonic relation between the flux harmonic of the motor and the electric angle is deduced,which provides theoretical support for harmonic simulation.Then,harmonic suppression is carried out.the core of determining voltage distortion compensation according to quantization formula is the accurate judgment of current polarity and the accurate obtain of actual duty cycle.In view of the current through zero is zero current clamp current polarity no measurement result of current polarity judgment comparison method for comparing the voltage of the proposed in this paper,the main principle is according to the size between terminal voltage and neutral voltage for the diode to the anti pressure drop and the size of the IGBT is the sum of the pressure drop pressure difference,by detecting the differential pressure polarity judgment direction of current flow,in turn,determine the polarity of current.Aiming at the problem of actual duty cycle acquisition,the voltage comparator is used to obtain the duty cycle,and the duty cycle is determined by collecting the rising edge and falling edge.Since the inverter is a three-level structure,two voltage comparators are needed and the comparison results are screened,which is called the double threshold comparison method.By solving these two problems,the accurate distortion voltage can be obtained,and t he voltage harmonics and current harmonics brought by the inverter can be eliminated by voltage compensation.The method is verified in the simulation and experiment,and the results show that the proposed method can well suppress the harmonics brought by the inverter.Last,the harmonic simulation is carried out.The magnetic flux obtained at each current working point was described in the form of polar coordinates,and the Fourier series coefficients were interpolated and fitted by a binary polynomial with dq-axis magnetic flux as the independent variable,and then the analytical expression of current reconstruction describing the saturation and harmonic characteristics was obtained.The method takes into account the saturation and harmonic effects and the cross-coupling effects of the motor,and takes the flux as the independent variable and the current as the dependent variable to realize the correspondence between the flux and the current.Secondly,according to the relation of power flow,the motor torque formula is deduced again,which takes into account not only the electromagnetic torque of the motor,but also the reluctance torque and the cog torque of the motor,which improves the calculation accuracy of the motor torque.The current and torque formulas greatly simplify the implementation process of the motor model in the motor simulator.At the same time,this method has the characteristics of small space occupation and fast operation speed,and is suitable for high-speed operation of FPGA.Simulation and experimental results show that the proposed method can describe the harmonic characteristics of the motor,and can be compiled and implemented on FPGA.