| The 400Hz medium frequency static power supply has greater advantages over the traditional rotating unit type medium frequency power supply,thus gradually replacing the traditional rotating unit type medium frequency power supply,and has been widely used in aviation power system,naval system,high performance uninterruptible power supply and other occasions.Traditional static power supply mostly uses input side 50Hz frequency transformer or output side 400Hz medium frequency transformer to achieve electrical isolation between input and output,however,transformer fundamental frequency is low,and the system power density need to be further enhanced;In addition,the high output voltage fundamental frequency and the large output current leads to the contradiction between the switching frequency and control bandwidth;The loads of medium frequency static power supplies are generally mostly nonlinear and unbalanced loads.In order to obtain high performance static power supplies,traditional control strategies are no longer available and suitable control strategies are needed.Therefore,the study of high power density static power supply and its control strategy is essential to improve the transient steady-state performance,efficiency and reliability of the system.First,this paper starts from the system topology,using a dual active bridge DC/DC converter instead of the original low-frequency transformer to achieve electrical isolation between the input and output and to improve the power density of the system;a three-phase four-leg inverter topology is used on the output side to meet the demand of unbalanced loads.For the above system,this paper designs the key parameters of a 30kVA capacity prototype,the hardware circuit of the main control circuit,sampling and driving circuit,and completes the construction of the prototype with the assistance of the cooperative enterprise.As the grid-side rectifier circuit,dual active bridge DC/DC topology have been widely researched and the control technology is relatively mature,the following research on the control strategy mainly focuses on the threephase four-bridge arm inverter circuit with 400Hz output.Secondly,for the problem of output voltage waveform distortion under nonlinear load,this paper analyzes the causes of output voltage distortion in nonlinear load line by traditional control methods,analyzes the problems of traditional multi-resonant quasi-PR control applied in 400Hz static power supply,and reproduces an αβ0 coordinate system under three-phase decoupling without differential beat control strategy to achieve the suppression of output voltage distortion under nonlinear load is achieved.Finite set model predictive control(FCS-MPC)is suitable for handling nonlinear power electronic converter systems such as 400 Hz static power supplies because of its advantages of simple design,good dynamic performance,and flexible structure.However,the traditional finite set model predictive control relies on the accuracy of sensor measurement results and system parameters,and is less robust to sensor faults and system parameter mismatch.To address this problem,a predictive voltage control method based on load current observation is proposed in this paper.This method uses an expansive state observer to estimate the perturbations caused by changes in load current and system parameters to reduce the dependence on the accuracy of system parameters and sensor measurements.In addition,the predictive control method is introduced to effectively improve the dynamic performance of the 400 Hz static power supply.In summary,this topic improves the system power density through the power circuit topology and improves the control strategy of the 400Hz output three-phase four-bridge arm inverter circuit to achieve high performance and high reliability operation of the static power supply system. |
