Research And Design Of Programmable AC Electronic Load Based On DSP

AC electronic load is one of the necessary equipment for power supply manufacturers and scientific research institutions.In the power product test and R&D process,different types of loads are required to be tested according to the difference in amplitude,frequency,and output waveform of the measured power supply voltage to verify its electrical performance.The traditional test loads are composed of inductors,capacitors,and resistors.These passive components are selected by calculation.Such loads have obvious disadvantages in parameter adjustment,energy consumption,and volume.In order to solve the shortcomings in the traditional load testing process,electronic loads have become mainstream devices in the power test market.Therefore,the study of AC electronic load has a higher engineering significance.Based on the control of TMS320F28335,a low-cost AC power load with 1kW power feedback device is designed in this paper.Based on literature research and understanding of existing products in the market,the main circuit topology using AC-DC-AC is dentified in this paper.It consists of two single-phase back-to-back PWM converters.The front stage is the load analog converter part,and a PI control system based on a single current loop is designed to flexibly simulate different types of loads,including constant impedance load,constant current load,constant power load and even non-linear load,etc.;Analysis and rigorous calculations selected the main circuit inductance and capacitance parameters;in order to solve the double frequency pulsation of DC bus,100 Hz notch filter and Butterworth filter are designed,effectively inhibited the bus harmonic.The influence of the wave on the subsequent control system improves the reliability of the grid-connected inverter and the power factor of the system.The inverter circuit adopts the voltage and current double-closed loop control strategy,in which the voltage outer loop adopts a PI regulator for stabilizing the DC bus voltage to ensure the stable operation of the system,and the current uses a quasi-PR regulator to eliminate the voltage fluctuation of the power grid on the system.Through the voltage type PWM grid-connected inverter,the high power factor of the electric energy sent out by the measured power source is fed back to the grid,achieving the purpose of energy conservation and environmental protection.The MATLAB/Simulink platform was used to build the system simulation model.By simulating various types of load,the unity power factor is connected to the grid,which proves the feasibility of the proposed scheme.On this basis,the sampling circuit,level shift circuit and drive of QP12W05S-37 chip are designed for AC electronic load system and protection circuits.The experimental platform was set up.Through DSP software programming,the experiment of AC electronic load prototype was realized,which proved the correctness of the design scheme of this paper.