The Research And Development Of Program-controlled Electronic Load

With the rapid development of power electronics technology,the status of electric and electronic devices is particularly important.However,these devices must be tested with various indicators and meet national standards before they can be put into production and use.For load-carrying tests,conventional loads have completely failed to meet the load requirements.This kind of load is not only bulky,but also the resistance value will change with the change of the outside temperature,and it will be different from the real load.Program-controlled electronic load is a device that controls the load resistance through a program and relies on the power tube to consume power.It can accurately detect the load voltage,accurately adjust the load current,more realistic simulation of life in common use of electrical appliances.According to the principle of electronic load,the block diagram of the control system is designed.According to functional requirements,the entire hardware circuit is divided into multiple modules,and then the working principle of each functional module is analyzed in detail.The STM32F103 chip based on ARM-Cortex-M3 core is designed as the control core hardware system.It is mainly composed of digital control module,A/D sampling module and load driver.The software architecture is composed of the upper computer software and the lower computer software.The upper computer software is designed and the lower computer program is written.The Ethernet communication problem between them is solved and the upper computer is controlled by the upper computer.The software part of the lower computer is based on the flow chart of the program design.It explains the process of the program in detail.The upper computer is a human-computer interaction program based on MFC.The interface function and the implementation code are designed,and the communication message between upper computer and the lower computer are given.Finally,the relay protection tester was used as the measured object,and the related indicators were tested and the results were briefly analyzed.Accuracy is an important technical indicator for measuring electronic loads.The system designed this time is composed of a hardware PI regulator that forms a series negative feedback and uses a low noise differential amplifier to improve the accuracy of the electronic load.At the same time,the software uses average filtering algorithm to process the data,reducing the impact of accidental errors.In the calibration process of the system,the least squares method commonly used in engineering can be used to update the calibration coefficient of the electronic load according to the requirements after the system is powered on.Finally,in the test of the protective relay tester,the three performance indexes of the load current,the port voltage and the load carrying capacity were tested according to the procedures,and the current voltage distortion ratio was increased when the input was AC signal.Test results show that the program-controlled electronic load achieves the desired goal and has practical value.