Voltage sag independent operation of induction motor based on Z-source inverter
Purpose - The purpose of this paper is to investigate the impact of different distribution of shoot through mode on Z-source inverter efficiency and particularly on complexity of switching pattern generation. Switching pattern generation has been optimized for field-oriented control (FOC) of induction motor operating beyond its nominal speed which can be easily accomplished due to the input voltage boosting implemented inherently by Z-source inverter. The proposed drive is unaffected to supply voltage sags, too. Design/methodology/approach - The space vector modulation switching pattern of the traditional FOC drive was modified in order to insert shoot through mode necessary for input voltage boosting. Since this can be accomplished only on account of zero mode of the inverter, the active modes have to be reduced. Consequently, the output voltage space vector has to be reduced, as well. Findings - In order to maximize profit of the input DC voltage and to omit the output voltage distortion, mathematical limitations have been derived giving the optimal boost ratio for required output voltage and ride-through capability during voltage sags. Practical implications - The experimental tests of upgraded FOC of induction motor with the proposed distribution of shoot through mode in the switching pattern of Z-source inverter and optimized control of inverter voltage are demonstrated. It is also shown that such a drive can withstand a long period of input voltage sags and operate in a broader field weakening regime. Originality/value - The paper's value lies in the overall, DSP-based control of the induction motor supplied with Z-source inverter gaining the maximum utilization of the input DC supply source and optimum trade-off between inverter efficiency and inverter components voltage stress.
z-source inverter space vector modulation field weakening field oriented control electromagnetic induction electromagnetism