Research On The Dual-loop Control Of 400Hz Inverter Under Wide Input DC Voltage

With its advantages of light weight and small size, 400 Hz medium frequency inverter is widely used in the field of vessels and aviation. In these occasions, to ensure its safe operation and reliable power supply, the inverter is not only required to output good quality of steady-state and dynamic waveforms, but also own the ability to protect the inverter when short circuit occurs and returns to normal if the short circuit fault disappears within several seconds. Based on a 2k VA 400Hz/230 V single-phase voltage-source inverter, this thesis will do some research on its dual-loop digital control strategy.Firstly, the mathematical model of single-phase full-bridge inverter is established, and in order to keep the simulation system in high according with the actual control system, this paper presents a simple and effective experimental measurement method, to modify the equivalent resistance parameter in the model. In addition, combined with the technical requirements, the paper gives the design method of the filter parameters, and considering the concrete requirement of dynamic performance, the original designed filter parameters are modified. Then, the dead-time effects of unipolar double frequency SPWM modulation are analyzed in detail, which provides a theoretical basis for the design of harmonic compensation controller.Secondly, aiming at the serious and non-ignorable influence of digital control delay on 400 Hz system, this paper takes the control time delay into consideration and gives the design method of dual-loop. Based on the traditional dual-loop control, this paper introduces the output voltage feed-forward and load current feed-forward control to improve the property of inductor current inner-loop. And puts forward a multi Proportional Resonant(PR) control method, which guarantees the inverter outputs a good quality of steady-state waveform and dynamic response speed, as well as small voltage overshoot when the load changes. PR controller makes the tracking performance of the inner-loop is also good, which can realize the short circuit current limiting protection, and improve the security of the system. For the impact of wide input DC voltage fluctuation range on the control system design, a simplified and equivalent design method is adopted in this paper. To avoid complicated theoretical analysis and simplify design process, MATLAB tools are used to design the controller parameters, and the design result is effective and feasible.Finally, some simulation and experimental verification are carried on to prove the proposed scheme in this paper, the simulation and experimental results are very consistent that the inverter outputs good quality of steady-state voltage waveform and dynamic performance, as well as the ability of short circuit current limitation protection and restoration. Then, summarizes all the contents in the paper, and makes a prospect for the future work.