Z-SOURCE NEUTRAL POINT CLAMPED INVERTER FED MOTOR DRIVE

Z-source inverter is a recently invented new power conversion concept mainly developed for fuel vehicular applications by advantageously utilizing the shoot through states to boost the DC-bus voltage. The impedance network contains two inductors and three diodes and is connected in between the DC source and inverter bridge. This shoot through state provides the unique buck-boost feature to the DC-link voltage and hence the AC output voltage of the inverter. By varying the boost factor and modulation index, the output AC voltage can be maintained at any value between zero and infinity regardless of DC voltage giving a wide range of voltage. Thus Z-source inverter overcomes the conceptual and theoretical barriers and limitations of the traditional inverters and provides high efficiency single stage structure for buck and boost operation. Previous publications have shown speed control of BLDC motor by controlling the DC link voltage of voltage source inverter using bridgeless buck boost converter. This paper presents the speed control of BLDC motor by controlling the shoot through states of Z-source neutral point clamped inverter using a space vector modulation technique which possess advantage of reduced harmonics with boosted output voltage. The proposed technique is demonstrated in simulation by using MATLAB software.