Research On Control Technology Of Quasi-Z Source DC Electronic Load System

The electronic load is a flexible and variable power electronic system that can meet the specific electrical load characteristics of the specific situation.It can replace some specific loads to meet the test requirements of different types of power supplies.The electronic load system can simulate various types of load characteristics through the cooperation of topology and power devices to meet the power supply test requirements.In order to further improve the boost ratio of DC electronic load system and the technical problem of high power factor feedback,this project proposed a DC electronic load device with single-phase quasi-Z source topology.The system uses a quasi-Z source topology as the load simulation unit,and combines with the single-phase H-bridge to form a quasi-Z source DC electronic load technology with high ratio boost and high power factor energy feedback.Based on the proposed single-phase DC electronic load structure using quasi-Z source inverter topology,the steady-state working principle of the system based on simple boost control technology is analyzed.The unified state space equation for the system is listed.Under the premise of considering capacitor series resistance and inductor series resistance,the relationship between steady-state voltage and current is derived,and the mathematical model of quasi-Z source DC electronic load is established.The stability of the system is analyzed,and the input current of the DC electronic load system and the small signal transfer function of the capacitor voltage are provided for the proposed control strategy.In order to achieve the goal of error-free load simulation and high power factor energy feedback,the load simulation control strategy and energy feedback control strategy of the electronic load system are studied.According to the established transfer function model,a load simulation strategy based on current tracking control is proposed.The input current is tracked without error by changing the duty cycle.The PI controller is used and the setting basis of related parameters is given.At the same time,an energy feedback control strategy combining straight-through technology is proposed.The DC bus voltage is indirectly stabilized by controlling the capacitor voltage,and the quasi-resonant controller is used to control the amplitude and phase of the inverter output current.The simulation results of static load mode and dynamic load mode show that the system can achieve the target of load simulation target and high power factor energy feedback.In order to further optimize the technical performance and technical indicators of the quasi-Z source DC electronic load system,the inductor current ripple,capacitor voltage ripple and output current ripple in the SPWM modulation method are analyzed,and the corresponding ripple expression is derived.Based on this theory,the inductance,capacitance and filter inductance of the main circuit of the system are designed.The main components of the system are selected and the hardware platform is built.According to the DC electronic load specification(GBT 29843-2013,JJF1462-2014)and the characteristics of low-voltage DC power supply(GBT-17478-2004)and other test standards,the effectiveness of the system’s boost,load simulation and power feedback control strategies is verified by experiments.