Research On Wavelet Modulation For Two Stage Matrix Converter

Two-stage matrix converter is a new kind of AC-AC power transformer, and it has its own unique advantages compared to the traditional single stage matrix converter. Its energy directional is reversible, input and output current are sinusoidal, and input power factor is adjustable. Meanwhile, it overcomes the shortcomings of the traditional matrix converter, which include large quantity of switches, complicated process of current converter control. As a consequence, it makes the topological structure more simple and the process of current converter more reliable. Various non-ideal conditions in practical application will affect the quality of two-stage matrix converter’s output voltage. Therefore, by using good modulation strategy to improve the quality of the output voltage has been many scholars research emphasis.Good control strategy can not only effectively improve the input and output characteristics, but alse reduce the harmonic component and the switching loss, that why it attracts the attention of many scholars. Unlike the traditional modulation strategy, this paper proposes a new type of wavelet modulation(WM) strategy which works in the two-stage matrix converter. Due to its unique analysis ability of local time-frequency and the principle of multi-resolution analysis, wavelet theory is widely used in communication and seismic survey area. Foreign scholars have started the research of the wavelet theory and applied the modulation technology to the power transformer. It has been implemented in the rectifier and inverter, and shows good output performance.In this paper, the two-stage matrix converter is the research object. First of all, two aspets including rectifier and inverter are studied. To the rectifier, the paper analyzes the input current and the DC output voltage, where WM strategy is applied. Besides, compare its performance with the classic space vector modulation(SVM) strategy. Then the paper analyzes the three-phase output voltage and harmonic distortion rate of the inverter with WM strategy, and also compares it with SVM strategy. Secondly, the paper conducts the coordinate modulation in rectifier and inverter with the WM strategy, and successfully applies the WM strategy into two-stage matrix converter, analyzes the performance of the input and output from the converter. Meanwhile, it carries on the analysis of the changing of performance in a variety of cooperation mode. After that, the common-mode voltage instantaneout value of two-stage matrix converter with WM strategy is analyzed. By improving algorithm, the paper successes to restrain the common-mode voltage, and compares its voltage waveforms between restrained ones and unrestrained ones. Finally, according to the simulation analysis of each part with the WM strategy, the software and hardware experiment platform is setted with the DSP2812 as the core. The experiment of simulation content is accomplished. By means of comparing with experimental waveforms and simulation waveforms, it draws a conclusion that the WM strategy simulation analysis is valid and WM strategy is reliable.The research results show that the WM strategy can realize effective control of two-stage matrix converter. Besides, by using WM strategy, there are many advantages both of in rectifier and inverter. These include the high quality of input current or output voltage, low harmonic distortion rate of output voltage and easy algorithm to implement. Meanwhile, the two-stage matrix converter common-mode voltage inhibition method becomes simple and convenient with the WM strategy, which can also have obvious inhibition effect.