The Digital Control Technology Research Of The Sigle-phase SPWM Inverter Based On DSP

Earlydays, the analog and open-loop control are widely used in inverter design because of the simple circuit and low cost, but the output waveform has harmonic distortion, high THD value and slower dynamic response. When the load mutates, the output voltage will decrease sharply and need a long time to become stable, and also when the input voltage fluctuation, the output voltage won't be stable too. Therefore open-loop control is only applicable in less demanding on the power quality of the occasion, and for more demanding occasions, the closed-loop control strategy is used to overcome the limitations of open-loop control.Nowadays, inverter power supplies are widely used, and full digital control can be realized when high performance DSP ( Digital Signal Processor ) controllers are produced. Digital controlled circuits with the merits of simple structure and high reliability tend to realize advanced arithmetic and the convenience of real-time control.This article introduces digital control technologies of a single-phase SPWM inverter based on TMS320LF2407A. The digital system will be the introduction with the output inductor current and output capacitor voltage with the formation of dual loop control, in the dual loop control system, the outer loop control are const value systems, and inner-loop is follow-up control system, the inner-loop's value can be decided by the outer-loop in accordance with the load and the system still has good quality. So, the dual-loop control system has a strong ability to adapt the changes of the load and it will enable greater improvement of the output performance of the inverter.Firstly, the advance of digital control and the control strategy of the inverter system have been introduced, then analyses the control technology and realization way of the single-phase SPWM inverter. Based on the mathematical model, the simulation is validated by the way of MATLAB.For digital control system based on the DSP-microprocessor, the article analysis its theoretical and experimental needs, on this basis, the entire hardware system platform is designed in details, including the overall structure of power, the main circuit, filter circuit, driver circuit , signal conditioning circuits realize. Control system focuses on the inverter digital control system design. The structure of the software is given and the single-output voltage control, output voltage and inductor current dual loop control are taken as the studying object. Through the discrete domain compensator designing, the stability and dynamic response of two types of inverter control strategy are analyzed and compared. The results show that the dual-loop control for inverters is superior to the single-voltage loop control in the stability and dynamic response.Finally, the article describes the realization of the control system, solves the main problem, and gives the designing parameters of prototype and software flow chart, the prototype is verified by experiments, and the results verify the correctness and effectiveness of control systems.