| Power products need to be tested when they are out of the factory.Usually,static loads such as resistors are used to carry out on-load experiments.Not only the accuracy of load simulation is not high,but also a lot of waste of testing power is caused.The energy-fed electronic load can recover most of the measured energy from the feeder network.At the same time,the load matching is flexible and the effect of load simulation is good.Its application is more and more extensive.Firstly,the paper expounds the research background and significance of energy-feeding electronic load,and then describes its development trend and current research hotspots from the aspects of topological structure and control strategy of energy-feeding electronic load,and then introduces several mainstream companies.The energy-fed electronic load product is researched and designed with 1kW single-phase energy-fed DC electronic load,and a 1kW single-phase energy-fed DC electronic load prototype is realized to achieve constant current.The constant load and constant power three load simulation modes of operation,and the tested electrical energy is recovered into the feed network.The main contents of the thesis include:(1)Determine the topology of the main circuit.The main circuit adopts “Boost circuit + single-phase full-bridge inverter”.The Boost circuit of the front stage implements the load simulation function and raises the input voltage to 400 V to ensure the the inverter circuit operates reliably;the single-phase inverter circuit recovers the measured electric energy and connects to the grid to realize the recovery of electric energy.The hardware circuit of 1kW energy-feedable DC electronic load is designed,including power circuit module,signal input circuit,optocoupler isolation circuit,sampling circuit,protection circuit and power supply circuit.The device selection and parameters of each part of the circuit are introduced in detail.Use Altium Designer to draw the schematic and PCB diagram of the whole system,and complete the production and debugging of the prototype.(2)The double closed-loop load simulation control strategy based on current inner loop and voltage outer loop is researched and designed.The voltage outer loop stabilizes the output voltage of the boost circuit at about 400 V.The current inner loop controls the input current of the boost circuit according to the operating mode of the analog unit.And the current inner loop controls the input current to track the command value.The simulation results show that the control strategy can accurately track the current command value in the constant current mode,and can quickly track the new command value when the command value is abrupt,and the dynamic performance is good.(3)The current PI controller is designed for single-phase LCL full-bridge inverter circuit with filter capacitor current feedback.The amplitude margin,phase margin and steady-state error of the grid-connected current are used as constraints to derive the control requirements.Controller parameters.The simulation results show that the designed current PI controller meets the design requirements,and the grid power factor is the phase error.(4)According to the designed hardware circuit and control strategy,a 1kW single-phase energy-fed DC electronic load prototype was fabricated,and TMS320F28335 was used as the main control chip to realize the control module function of the system.An experimental platform was built to test the key circuits of the system,and then load simulation and power feed network experiments were carried out.The experimental results show that the 1kW single-phase energy-feeding DC electronic load can work in three load simulation modes of constant current,constant resistance and constant power.In constant current mode,the maximum steady-state error is 5%.When the system works at full load,the power factor of grid-connected power is 0.981,the DC component of grid-connected current is 6mA,and the energy recovery efficiency reaches 95%,which meets the design standard. |
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