| In order to avoid the influence of harmonics generated by non-linear loads in MoreElectric-Aircraft on the quality of aircraft grids,aviation power sources usually use active power factor correction technology,and it is of great significance to carry out research on PWM rectifiers suitable for AC variable frequency power supply systems in More Electric Aircraft.As a power factor correction device,the PWM rectifier is divided into voltage source rectifier and current source rectifier.The bus voltage of the three-phase voltage source rectifier usually reaches above 650 V,the output voltage level is high,and the change range is narrow,which is not conducive to the design of the subsequent stage converter.The output voltage of the current source rectifier has the ability to be adjusted and has a wide range of changes.It will not produce the problems of over current caused by load short circuits,and has a broader application prospect.At present,the research on the application of the three-phase current source rectifier is mostly limited to the field condition of 50 Hz grid frequency.This paper proposes to extend the application of the three-phase current source rectifier to 400Hz-800 Hz grid frequency.The rectifier tracks the phase and frequency of the power grid through the synchronous reference frame phase locked loop to meet the work requirements of the rectifiers for power supply system in the aviation field.In addition,this article also carried out the following research:Firstly,this paper studies the working principle of the three-phase current source rectifier,and analyzes the PWM signal generation technology of the three-phase current source rectifier.By establishing a mathematical model,the control strategy of the current source rectifier is studied.In this paper,a dual closed-loop indirect current control strategy using a combination of an output voltage outer loop and a DC-side inductor current inner loop is used to indirectly control the grid-side current by controlling the DC-side inductor current to achieve the unit power factor of the device.This method does not require the collection of grid current,eliminates the need for grid-side current sensors,and reduces the amount of data processing and the complexity of system design.Secondly,for the resonance problem of the grid-side LC filter,this paper uses a resistor-capacitor hybrid passive damping method with good high-frequency attenuation characteristics to effectively suppress the grid-side current oscillation.In order to meet the requirements of the spacecraft bus voltage,this article uses Boost converter as the post-stage circuit of the three-phase current source rectifier to increase the output voltage to 270 V.Using TMS320F28035 and EPM570T100I5 as the control chip to realize digital control of the circuit.The closed-loop simulation of direct current control and indirect current control is completed by using PSIM software.The correctness of the control strategy is verified by simulation results.Finally,an 1.35 kW experimental prototype of three-phase 115 V input was fabricated and tested.The test results show that the PFC function is implemented on the input side of the prototype.Under the condition of 400 Hz power grid,the measured PF value is greater than 0.96;the peak efficiency of the three-phase current source circuit reaches 94% at half load.In addition,the prototype still works normally and achieves a unit power factor under the conditions of grid frequencies of 500 Hz,600Hz,700 Hz,and 800 Hz. |
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