Research Of Harmonic-Compensate-Type Energy-Feedback Electronic Analog Load

With the continuous development of power equipment at various power levels,energy-feedback electronic analog loads are increasingly used as tools for testing the characteristics of power supplies.At present,the grid-connected energy-feedback analog load is developing toward miniaturization,high efficiency,energy saving,and complete test functions.It is also used in the testing of various types of power supplies.However,the grid-connected function of the grid-connected energy-feedback analog load will increase the cost and introduce harmonic interference,and the grid-connected energy-feedback analog load cannot solve the harmonic interference caused by the conventional rectifier at the input end of the measured power supply.Aiming at the problems of the above-mentioned grid-connected energy-feedback electronic analog load,a novel harmonic-compensate-type energy-feedback electronic analog load is presented.The load,using a two-stage circuit structure,includes a pre-stage analog load module and a post-stage inverter circuit module,and connects the output of the inverter circuit with the input of the measured power supply.The pre-stage adopts BOOST converter,and combines the single closed-loop PI current control algorithm to track the given load characteristics and realize the function of analog load characteristics.The post-stage adopts three-phase DC/AC inverter circuit,and combines the energy feedback and harmonic compensation algorithm presented in this paper,so that the output current of the inverter circuit compensates the current harmonics at the input end of the measured power source,and realizes energy feedback and harmonic compensation functions.This paper takes the regulated power supply output of 24V/500 A as the test object,and focuses on the design of the power circuit and control circuit of the harmonic-compensation-type energy-feedback electronic analog load,and implements the corresponding control algorithm.Among them,the power circuit mainly includes input inductance,power switch device,power diode and output storage capacitor of the pre-stage BOOST converter,and power switch device and three-phase LC filter of the post-stage three-phase DC/AC inverter circuit.At the same time,combining the design parameters of the two-stage power circuit,this paper firstly establishes a small-signal model based on current tracking for the pre-stage BOOST converter,and obtains the PI controller from the engineering tuning method.And then this paper establishes mathematical model for the single-phase DC/AC inverter circuit,equivalently separated from the post-stage three-phase DC/AC inverter circuit,and obtains the PI controller of the single-phase DC/AC inverter circuit,which provides a theoretical basis for the independent control of each phase under the three-phase stationary coordinate abc.To meet the physical realization of the two-stage circuit,the control circuit designed in this paper mainly includes current detection conditioning circuit,voltage detection conditioning circuit,grid voltage phase lock circuit,DSP control circuit,IGBT isolation drive and protection circuit,and low-voltage power supply circuit.In addition,this paper designs the corresponding DSP program.Finally,this paper uses Matlab/Simulink to build a simulation model of harmonic-compensation-type energy-feedback electronic analog load.The simulation results verify the rationality of the circuit structure and the feasibility of the control algorithm.On the basis of the above design,this paper also preliminarily builds the experimental platform of the pre-stage analog load module and debugs it.The experimental results prove that the analog load module,designed theoretically,meets the requirements of the project and the singleclosed-loop PI control algorithm can achieve accurate tracking of the current instruction.