Harmonic Compensation Type Energy Self-Feedback Electronic Load Design

Electronic load is a device that implements load characteristic simulation using a switching device.It has better flexibility than the traditional static load,and can implement energy recycling by energy feedback when used for power supply testing.As a hot spot in the development of power supply testing technology,electronic load has essential research value.This paper analyzes the structural characteristics of existing electronic load systems at home and abroad,and proposes an energy self-feedback electronic load with harmonic compensation function,which solves the harmonic interference problem generated by the power supply itself and realizes energy recycling.The main circuit of the electronic load adopts a three-stage structure.The front stage is a Boost circuit for simulating load characteristics.The middle stage uses full-bridge DC/DC convertor to realize the conversion of low-voltage to high-voltage energy.The output of the rear-stage inverter is connected in parallel with the input of the measured power supply,to implement energy self-feedback.The electronic load system is connected in series with the inductor on the grid side to isolate the harmonics of the inverter output from the grid.In this paper,the 24V/50 A DC regulated power supply is used as the test object,and the parameters of the power switching devices,filter inductor,storage capacitor,diodes and high-frequency transformer in the main circuit are designed.The small-signal model of electronic load circuit and inverter is established by state space averaging method,and the incomplete differential PID controller is designed.In order to realize harmonic compensation and energy feedback,this paper designs a fundamental wave separation algorithm that can be used in single-phase circuits.The inverter is controlled to compensate the current harmonics at the input end of the power supply,and the fundamental component is modulated by the DC capacitor voltage to achieve a balance of energy for the electronic load system.The control algorithm is implemented using the DSP chip TMS320F28335.This paper gives the control program design of DSP chip and the design of DSP peripheral circuit,including voltage/current sampling circuit,PWM enhancement circuit,switching tube drive circuit and so on.At the end of this paper,the whole circuit is simulated by MATLAB,then the experimental platform is built on the basis of the above design,and the joint debugging of software and hardware and related circuit and algorithm experiments are completed.Finally,the feasibility of the harmonic compensation energy self-feedback electronic load design is verified by analyzing the simulation and experimental results.