Study On DSP Control Output Waveform Of Fuel Cell Generating Power Inverter System

With the contradictions of energy and environmental protruded increasingly, Fule Cell, as a green energy resources popularized, has been paid on more and more attention. And the research is carried out more and more in-depth. Combined with the output characteristics of fuel cell, three-phase full-bridge inverter was adopted to achive power conversion with the digital control in this paper. And the quality of output waveform was the basic requirements in power. To achieve nearly sinusoidal output voltage even with nonlinear loads and less harmonic content, the feedback control technical was important part in the three-phase inverter system. Due to advangages of digital technolgy and the development trend, the digital signal processor(TMS320F2812)was adoped to control output waveforms when the three phase inverter developed.Firstly, the three-phase full-bridge inverter that connected to the system was refined and improved by simulation analysis according to the capacity and output of the Fuel Cell power plant, and its protection circuit was optimized. Meanwhile, the hardware platform of three-phase inverter system was established when the sampling and driver circuit of control system were designed copmeletely.Secondly, the output harmonic factor of the three-phase SPWM inverter was detailed analysed in this paper. A mathematical equation of three-phase inverter output voltage was deducted on the condition of bipolar control. It was optimal designed with the harmonic of carrier-ratio and degree of modulation and sample mode. The effect of output waveform is analyzed in depth , under load especially non-linear load disturbance. While these effects were simulated, and that use of feedback control techniques to improve the output waveform. Then harmonic currents caused by nonlinear load was detected and filtrated by digital control. SPWM modulation was realized by DSP digital PI(Proportional Integral)control strategies under voltage instantaneous feedback control method adopted with filter inductor current inside loop. And the transfer function model of the two closed-loop control was builded. Parameters of the controller was determined through theoretical calculation and experimental after analysis of the impact of the controller parameters on system finally. The simulation results show that the output waveform was good and the THD(Total Harmonic Distortion) values was smaller.Lastly, the experiments were carried out for the whole platform in this paper. Good output waveforms and below 5% harmonics of voltage were obtained on the condition that linear and nonlinear loads and so on. System had good dynamic response and protection capability when mutation load and fault scenarios occurred. Experiments show that the three-phase inverter system platform and the control strategy are effective and feasible.