Research On Program Controlled Digital Inverter Based On DSP

Research and quality control of the electronic equipment needs many series of test in laboratory. Many of these test projects need AC signals at different voltages and frequencies. For example, the test of AC motor needs voltage source at different frequencies with whole range; The voltage and frequency of power source for evaluation of UPS need to be through 85~250V, 47~63Hz; Auto product line in factory needs different voltages and frequencies power source to test the products. This paper is going to develop a program controlled digital inverter with double-loop control in order to accomplish the product auto test procedure.Paper first builds the math model of the main circuit, and then makes the static state analysis and the ac small signal analysis to obtain the steady state equation, transfer function and some key information.What follows next is to contrast and analyze different control method, including instantaneous voltage control, peak current control and average current control. The result is simulated by Matlab/Simulink software to verify the correctness in order to guide the manufacture of the physical object. Ultimately the average current control method is chosen.Based on the need in the practical engineering, this paper designs the IGBT drive circuit, the digital control unit and its peripheral circuits with DSP2812.For the software part, paper first conducts the discretization process to the continuous transfer function to obtain the PI digital algorithm for DSP control. Finally, paper realizes the communication between DSP and the host computer with the function of controlling, sampling and analyzing. At last, the test of the inverter is done with load at different voltages and different frequencies, and respectively samples and analyzes the static and dynamic waveform. The result of experiment shows that the digital inverter based on DSP designed in this paper can adjust the voltage and frequency well, and the accuracy of the output voltage is below 3%. Hence this inverter is able to accomplish the work for auto test system, and runs well.