Research On Two-stage Matrix Converter Based On The Series Z-source And Five-leg Inverter

Dual-AC motors drive system offers a number of advantages, including small torque ripple, low DC bus current harmonic and high system reliability, it has been found more and more applications in hybrid electric vehicles, railway traction system, aerospace, etc. With the development of the power electronics technology and power electronics, the drive system is subjected to space constraints, the number of switching devices and manufacturing costs and other factors, and thus, the performance including the size, suitability, reliability and other aspects for dual output power converter draws higher demand. As a green power converter, two-stage matrix converter(TSMC) has some attractive features such as sinusoidal input/output currents, bidirectional power flow, high power density, and high input power factor, so it has recently been widely discussed. Deriving from TSMC, the five-leg inverter TSMC is proposed, whose topologies without the DC-link energy storage can increase the power density and reliability. However, it is sensitive to the power source/grid disturbances, and the maximum voltage transfer ratio is 0.866 which limit its application range. In this paper, the series Z-source is introduced to five-leg inverter stage TSMC, by useing the unique nature of the series Z-source network to solve some of the inherent flaws of the five-leg inverter stage TSMC.A series Z-source five-leg inverter stage TSMC(SZS-FLI-TSMC) topology is proposed by introducing Z-source network in this paper. The fundamental modulation strategy of the proposed topology is presented and its theoretical equation of the overall voltage transfer ratio is derived. The modulation strategy using a zero-current communication can remove the dead time that is necessary for traditional AC-AC power converter, which guarantees the quality of the output waveform. In order to increase the inverter stage modulation index, and decrease the capacitor voltage of the Z-source network and simplify the calculation, an improved space vector modulation strategy with dynamic boost factor is proposed. In addition, a linear soft starting method with maximum inverter stage modulation index is presented, which can reduce the inrush current at startup effectively. Finally the proposed topology and its modulation strategies are verified by simulation and experiment resules.