LC-Filter Integrated Quasi-Z Source Indirect Matrix Converter

ABSTRACT:The indirect matrix converter (IMC) is one of matrix converters that achieve sinusoidal input currents, variable frequency and variable voltage output, high power factor, bidirectional power flow, without bulky DC-link capacitors/inductors of conventional ac-dc-ac converters. Moreover, the IMCs overcome the commutation problems of the direct matrix converter (DMC). Therefore, the IMCs become increasingly attractive in applications to motor drives, military power supplies, energy conversion, etc. However, the voltage gain of conventional IMCs is not higher than0.866, input filters are required to lower input current harmonics, and output is sensitive to grid disturbances. All these defects restrict industrial applications of IMCs. Z-source concept provides a promising method to extend voltage gain of matrix converter and improve anti-interference ability. The continuous quasi-Z source network was combined into the IMC in this thesis, quasi-Z source IMC achieves high voltage gain, all silicon solution, sinusoidal input current without additional input filters, because the continuous quasi-Z source network integrated the LC filter.Firstly, operating principle and boost feature of the new topology is provided. A small-signal modeling is employed to build the impedance network transfer function, and second-order LC filtering performance is achieved. Pole-zero sensitivity has been analyzed with change of quasi-Z source network parameters including inductance, capacitance, inductance stray resistance, capacitor equivalent series resistance and shoot-through duty ratio.Secondly, space vector modulation is proposed for quasi-Z source matrix converter through inserting shoot-through vector into the rectifier stage, and an optimal switching timing sequence is selected.Thirdly, common mode voltage (CMV) issue of quasi-Z source IMC is analyzed and the factors that affect CMV are figured out. Three modulation strategies are proposed to reduce CMV of quasi-Z source IMC. Two solutions named as methods I and II are achieved in the inverter stage, and the third CMV reduction method is proposed through modifying modulation method of the rectifier stage. Comparative evaluation is carried out between three methods and conventional modulation method. Experimental results verify that three methods can significantly reduce the CMV of quasi-Z source IMC. Fourthly, this thesis analyses the parameters of quasi-Z source IMC, including voltage/current stress, ripple and power loss of capacitors, inductors and power devices, respectively. Calculation formulas and design principles interrelated are given.Fifthly, quasi-Z source IMC is applied to induction motor drive, and the indirect field oriented control is achieved. Simulation results verify the dynamic and steady state characteristics of the system.Finally, this thesis designs and implements the experimental bench of LC-filter integrated quasi-Z source IMC, using DSP and CPLD as the controller. Experimental results validate the availability and correctness of basic principle, boost capability, filtering performance, modulation strategy and design ideas.