The Research Of Output Waveform Control Technique For Single-Inverter

In recent years, with the development of the society, modern power electronic techenique has improved continuously, the number and the proportion of various non-linear electrical equipment are increasing. With the development of inverter waveform control technology, the low harmonic, high precision and fast response of inverter is demanded increasingly, high precision and low harmonic performance of the inverter play huge role for equipment protection and reducing electrical grid pollution, now there are a variety of waveform control technique.The paper has researched the single-phase inverter with nonlinear load, and it analyzes several closed-loop control strategies which can compensate disturbance of output waveform and increase the output voltage waveform quality, the research target is to make the inverter has advantages of good output waveform and fast dynamic response.Firstly, single-phase inverter mathematical models were established, and selection method of the single-phase inverter output filter parameter was analyzed, and actual parameters of the output filter were determined, also various factors of inverter output waveform distortion were analyzed.Secondly, the quality of the output waveform has been improved by adopting closed-loop control method and the repetitive control principle has been introduced, the repetitive control has been atopted on the simulated analysis of time and frequency domain for single-phase inverter, the simulated result of simulation has shown that repetitive control make the system has good steady-state performance and lower THD of the output voltage, but repetitive control has a cycle delay which causes slow response of the system. In order to compensating the shortage of the repetitive control, PI dual closed-loop control based on repetitive control is researched in this paper, the designing scheme of current loop of PI dual closed-loop control is analyzed, the simulated analysis of time and frequency domain has shown that output waveform of inverter has good steady-state and dynamic performance in the PI dual closed-loop control based on repetitive control and lower THD of the output voltage, but the compound control is bader than single repetitive control in the system steady-state performance, the repetitive control based on impedance regulation, which combines repetitive control with pole placement, adopts the pole placement to improve system damping and dynamic performance of the inverter, and the inverter output impedance is decreased, the simulated analysis of time and frequency domain has shown that output waveform of inverter has good steady-state and dynamic performance in the repetitive control based on impedance regulation, this compound control is smaller than single repetitive control in the THD of the output voltage.There is the transient oscillation on the single LC filter, the paper has adopted virtual impedance to improve the system damping and the output filter owns the advantage of strong ability of oscillation suppression, low loss and easy realization. The virtual impedance can be adopted in simulations and experiments of the single-phase inverter waveform control, which not only can eliminate the transient oscillation of the output filter, but also the transmission efficiency of the inverter and the quality of the inverter output waveform are improved.Finally, according to above research, a experiment platform is built as the ARM control chip of STM32F407IG model, various part hardware circuits is designed, each algorithms were realized by software programming, the result of experiment has proved that the paper has achieved research target by using control strategy of the thesis correctly and effectively.