Development Of A Kind Of DC Energy-feedback Electric Load

In order to ensure the safe and stable operation of the power supply equipment,it is necessary to carry out the load test on the power supply equipment according to the different performance before leaving the factory.Traditional load test method adopts a static impedance for discharge testing.However,this method has many shortcomings,such as the static impedance of the load in a single form,the huge waste of energy eventually emitted in the form of heat.Energy-fed DC electronic load has the advantages of being capable to simulate the characteristics of the load,being light and flexible,having excellent test performance and being capable to feedback energy to the grid to achieve energy recycling,etc.,and thus hopeful is widely used in the factory testing of power supply equipment.This paper first analyzes the working principle of energy-fed DC electronic load,then compares the advantages and disadvantages of several types of energy-fed DC electronic load structures,and gives the system design scheme of this paper.In this paper,a DC-DC converter and a DC-AC converter are connected in series,and finally the energy is fed back to the grid through the transformer.The main function of the pre-stage DC-DC converter of the energy-fed DC electronic load is to realize the control of the input voltage and current,and the H-bridge Boost circuit is used as the topology of the main circuit.Because the input current is larger,each bridge arm of the H-bridge Boost circuit uses the structure of four power tubes connected.The control chip adopted by the DC-DC converter is the SG3525,which adopts a single-closed-loop control strategy and controls the output voltage and current by adjusting the duty cycle of the PWM wave.The main function of the after-stage DC-AC converter of the energy-fed DC electronic load circuit is to convert the DC power into AC power and have it feed back into the power grid to realize the recycling of energy.DC-AC converter selects the TI's TMS320F2812 as the main control chip.DC-AC converter is modulated in bipolar SPWM and is controlled by the double-closed-loop control of outer voltage and inner current,and is added with the feedforward control of the grid voltage,equipping the DC-AC converter with fast response,higher stability and robustness.Finally,the modeling and simulation is established through the Simulink module in Matlab,and an experimental prototype is set up to analyze the experimental results so as to verify the feasibility of the scheme.That is the system can better simulate the characteristics of the load,and the output current of the AC side of the inverter satisfies the grid connection,the content of the harmonic of the output current is very low as it is close to the unit power factor,and the system can operate stably and reliably.