Research On PI+Repetitive Control Of Dual Buck Inverter

Inverter as DC/AC power conversion device plays a very important role in distributed generation system and uninterrupted power supply system(UPS).In recent years,with the wide application of power semiconductor devices and the development of inverter topology,high performance inverter has became a hot research topic.The traditional full bridge inverter which have shoot-through problems in bridge legs.The inductor current flows through the body-diode,which have problems of serious loss of inverter and reverse recovery.This leads to the reduction of the reliability and efficiency of the DC/AC converter.Dual Buck inverter have advantages of high reliability,high efficiency and so on to be studied and used,which is due to the elimination the of the shoot-through problems and optimization of the freewheeling diode.Output waveform of Inverter with load contains a large number of harmonics,which is difficult to consider just rely on LC filter.There fore,Sine Pulse Width Modulation stechnology is used to obtain high quality output waveform and reduce the filter volume.For dual Buck inverter,it also needs to use other efficient control strategy based on SPWM modulation to improve output waveform quality.Dual Buck inverter with high reliability as the reseach object in this paper.Firstly,the significance and research status of the inverter is described and several types of dual Buck inverter and some control strategies are summarized.Then,the working mechanism of the dual Buck inverter is studied,and the transfer function of dual Buck inverter is analyzed under half cycle current SPWM modulation.At last the mathematical model based on current feedback and SPWM modulation is obtained.This paper will focus on the analysis of control strategy of dual Buck inverter.Firstly,this paper uses PI regulator to get the reference signal of half cycle current modulation.The system resonance is relatively large through the analysis of a single PI control in the no-load and overloaded and the control effect is not good.Then,this paper introduces embedded PI+ repetitive control method for dual Buck inverter.The whole control structure is simplified,and the equivalent control object of repetitive control is obtained.A suitable compensator is designed according to the equivalent control object.Through analysis,it is found that the equivalent control object is complex,and the design of the perfect compensator is very difficult.On the basis of the above,the state feedback decoupling of the inverter is also carried out.Based on the decoupling of inverter,the design of the embedded PI+ repetitive control stability condition and the repetitive control compensation function are analyzed in detail on the basis of Inverter decoupling.The design of repetitive control for the inverter system after decoupling is more simple,and the control effect is better.Finally,the accuracy of control strategies is verified by PSIM software,and Dual Buck inverter of 110V/50Hz/500VA is built to test theoretical analysis and simulation result based on the DSP(TMS320F28029).The feasibility of the proposed control algorithm is further verified.