Research On Performance Of AC Electronic Load Based On DSP Control

With the development of power electronics technology,various power electronic power supply devices provide stable,reliable and continuous power guarantee for daily life and industrial production,such as high-power AC power generator,uninterrupted power supply,inverters and so on.In order to prevent the adverse effects caused by power supply damage,it is necessary to carry out long-term aging test and electrical performance test of the power supply before the product leaves the factory.The traditional test load is composed of seriesparallel passive devices such as resistors,inductors and capacitors.There are many shortcomings when using the traditional test load to test,such as parameter adjustment is not flexible,energy waste,high calorific value,high cost and so on.In order to save cost,improve accuracy and flexibility,save energy and other considerations,this thesis mainly studies an AC electronic load device with energy feedback function.Energy feedback AC electronic loads can accurately simulate various types of loads.The energy feedback AC electronic load can accurately control the amplitude and phase of the output current of the tested power supply according to the requirements,and it can feed back the power output of the tested power supply to the power grid.The main contents of this thesis are as follows:Firstly,this thesis introduces the research status of electronic load at home and abroad,including the research status of electronic load topology and control methods.The core part of AC electronic load studied in this thesis is voltage source PWM rectifier.By analyzing the working principle of four quadrant operation of voltage source PWM rectifier,the operating principles of load simulation side and grid-connected feedback side are discussed.On this basis,the realization scheme and overall structure of the AC electronic load studied are designed.The topological structure of AC electronic load with LCL filter is designed.The reason of using LCL filter is analyzed,and the method of selecting circuit parameters is given.Then,the mathematical model of AC electronic load is established in different coordinate systems.Secondly,the control strategy of AC electronic load is studied in this thesis.The advantages and disadvantages of several different control strategies are compared and discussed.In order to overcome the shortcomings of traditional control strategies,a single current loop control strategy based on instruction impedance and SVPWM is proposed in the load simulation part.The calculation method of converting instruction impedance into instruction current is given.In the energy feedback side,the double closed-loop control strategy of voltage outer loop and current inner loop is adopted.The simulation model is built by Simulink software,and the simulation results are analyzed.Finally,in order to verify the feasibility and correctness of the experimental scheme,an experimental platform of AC electronic load based on DSP control is built.The performance of AC electronic load is studied through experiments.The experimental platform takes the TMS320F28335 DSP controller produced by TI Company as the control core.The hardware and software of the control system are designed.In the software implementation part of the control strategy,a control algorithm based on instruction impedance combined with SVPWM is implemented by using the method of generating code by MATLAB and CCS.The experimental results show that the control strategy can accurately control the analog side current of the load.It is proved that the control strategy can simulate the required load characteristics.On this basis,the performance of AC electronic load is studied through experiments.The harmonics of input current in the analog side of AC electronic load under different switching frequencies and different properties are analyzed.The experimental results are analyzed by spectrum analysis and their changing rules are summarized.When the hardware parameters of AC electronic load have been fixed,it has certain guiding significance for the selection of switching frequency of electronic load.