Research Of Control Strategy Of Unbalanced Three-phase Buck Rectifier Under Wide Input Voltage Frequency

With the emergence of Airbus A380 commercial aircraft,Boeing B787 commercial aircraft,and F-35 fighter jets,More-Electric-Aircraft(MEA)has become the development trend of future aircraft.The problem of harmonic pollution has also aroused widespread concern in the aviation industry.Due to the advantages of simple structure,high power generation efficiency,and small volume and weight of the three-phase variable frequency alternator system,it is widely used in new multi-electric aircraft.Its output voltage frequency varies from 360 Hz to 800 Hz,and in actual application scenarios,the output voltage of the generator may be unbalanced due to various factors,such as load changes,parameter asymmetry,and external interference.As a result,the output voltage and output current of the DC side of the rectifier produce even-numbered non-characteristic harmonics,and the input current of the AC side produces odd-numbered non-characteristic harmonics.The input current is severely distorted,and the rectifier may even be damaged in severe cases.The three-phase Buck rectifier has a wide range of adjustable output voltage and good short-circuit protection features,so it has a good application prospect in aviation power supply systems.Therefore,it is of great significance to study a three-phase Buck rectifier unbalance control strategy suitable for wide input voltage frequency.This paper takes the three-phase Buck rectifier as the research object and introduces its topology and working principle.On this basis,the three-phase Buck rectifier 12-sector fivesegment SVPWM modulation strategy is studied,and the corresponding vector action time is derived according to the working mode.Introduces several different vector distribution strategies and duty cycle generation methods,and compares them in terms of actual implementation difficulty,switching loss,and impact on input current quality.a wide-Line Frequency three-Phase Buck rectifier Control Strategy under unbalanced AC Input Conditions is emphatically studied.The equivalent DC/DC model of the three-phase Buck rectifier is established and the equivalent parameters are derived.The state equation of the equivalent DC/DC model and its AC small-signal circuit model are calculated.Then based on the idea of single-phase Boost PFC average current control in CCM mode,the working principle of the three-phase constant resistance input control strategy based on average inductor current control is analyzed in detail,and the current inner loop and voltage outer loop are designed according to the equivalent DC/DC model.This control strategy can significantly improve the quality of the AC side input current when the three-phase input is unbalanced,but its DC side output voltage still has a ripple of twice the operating frequency,so a new method based on Constant On Time(Constant On Time,COT)controlled Buck DC/DC series compensation strategy to achieve a constant total output voltage.The unbalanced control strategy combined with the output voltage ripple compensation strategy can improve the quality of the input current on the AC side of the three-phase Buck rectifier,and ensure that the output voltage is a constant DC value.Finally,The stress of the power device was calculated,and the AC side LC filter,DC side inductance and output capacitor were designed,and a 1000 W three-phase Buck rectifier principle prototype was built.The experiment verified the correctness and feasibility of wideline frequency three-phase Buck rectifier control strategy and ripple compensation strategy.