Research On The Control Strategy Of High Power Factor Three-Phase Six-Switch PWM Rectifier For Aviation Application

With the rapid development of More Electric Aircraft(MEA),there are more and more airborne electronic devices.As the front stage of the power system,high power factor,high power density and high reliability of the three-phase rectifier are very important.In the aviation applications,in where the input frequency is high and varies in a wide range,the main non-idealities faced by three-phase rectifier are time delay,dead time,and sampling DC offset.In this paper,for the digital controlled three-phase six-switch PWM rectifier using Average Current Mode(ACM)control,the performance of different types of current controllers under the influence of non-idealities is analyzed,and several improvements are given based on the existing control schemes.For the three-phase PWM rectifier,the commonly used circuit topologies,control strategies,modulation strategies and their advantages and disadvantages are introduced.According to the characteristics required by the three-phase PWM rectifier in aviation applications,the three-phase six-switch PWM rectifier topology,the average current mode(Average Current Mode,ACM)control strategy,and sinusoidal pulse width modulation(SPWM)strategy with the third harmonic injection are used.The operation mode and mathematical model of the three-phase six-switch PWM rectifier are analyzed,the structure and operation principle of the ACM control system are discussed,and the duty cycle feedforward and the third harmonic injection are discussed.The causes of time delay effect and dead time effect are introduced.The traditional control model of the traditional ACM control system is introduced and its drawbacks are pointed out.An improved ACM control model is proposed,which can intuitively reflect the influence of time delay and dead time on the inductor currents.With the consideration of time delay,dead time,DC offsets of sampled input voltages/currents,based on the improved control model,the performance of different types of current controllers is analyzed.It is proved that in the ACM control system,the PI type current controller features the high capability of suppressing the effect of time delay and dead time,but suffers the inevitable current distortion caused by the sampling DC offsets.The reason of current distortion is analyzed in detail,and the design principle of current controller is proposed.To overcome the shortcoming of the PI-type current controller,an impoved Average Line Current(ALC)control strategy is proposed,which completely eliminates the current distortion caused by the sampling DC offsets when the PI-type current controller is applied in the traditional ACM control system.It is proved that the ALC control system using the PI-type current controller has the advantages of high power factor and low input current harmonics.In addition,based on the advantages of the PI type current controller,a proportional integral lag(PIL)type current controller which has higher power factor than the PI type current controller is designed.A 4k W prototype is designed,the software and hardware design process of the power circuit and control circuit is introduced,and the steady-state experimental waveforms using different control strategies and current controllers are given,which verifies the correctness of the theoretical analysis.