Research On Line-to-line Voltage Control Strategy Of Matrix Converter Under Unbalanced-input Voltage

AC-AC matrix converter (MC) is known as a new non-pollution converter. MC contains many potential applications in power electronic fields. At present, many researchers are carrying out research into MC under balanced-input voltage condition, but there still exists difference between the research results and the practical situations. Therefore, it is a practical signification to carry out the research by taking into account the unbalance of actual input voltage.This paper introduces the theory of double line-to-line voltage for three-phase AC-AC MC. The influence to output-voltage and input-current of MC is analyzed under unbalanced-input voltage. In order to improving output-voltage and input-current waveform quality, the double line-to-line voltage control strategy of MC is modified in the follows. Also, a series of control function expressions of double line-to-line voltage are figured out under unbalanced-input voltage.The simulation models of double line-to-line voltage and its modified control strategy under unbalanced-input-voltage are constructed using Matlab. The simulation results indicate that the non-modified modulation strategy under unbalanced-input-voltage is possessed of self-adapting performance. The simulations are also carried out to verify the correctness of the modified control strategy which can obtain the balanced three-phase output voltage waves and improve input-current waveform quality under unbalanced-input voltage.In the paper, a prototype of matrix converter based on double line-to-line voltage modulation strategy is built. DSP (Digital Signal Processor) and CPLD (Complex Programable Logic Device) programs are designed, and the experiments are done for the above theory. The output-voltage and input-current waveforms are given and analysed. The experiment results further demonstrate that the non-modified control strategy can obtain excellent performance which improves output waveform quality, and the modified control strategy can obtain excellent performance which improves output and input waveform quality under unbalanced-input voltage, which further verify the validity and feasibility of the improved control MC.