Research On Multi-drive System Based On The Novel Five-leg Inverter

Five-leg inverter is suitable for the multi-drive system, and it can be used to feed two motors running independently. Compare to the conventional dual motor system, the five-leg drive for dual motor drive system cut down the system hardware cost can be used as the fault-tolerant operation for dual motor drive system to improve the reliability of the dual induction motor speed control system. In this paper, the control strategy and the modulation method of multi-drive system based on five-leg inverter are investigated.The voltage transfer ratio of five-leg inverter is low under conventional modulation strategy, which will affect the capacity with load of system. To solve this problem, this paper proposes a novel PWM modulation method to improve the voltage transfer ratio of five-leg. By optimizing the distribution of voltage space vector pulse, voltage transfer ratio is enhanced effectively. This modulation strategy is easy to be realized and the voltage transfer ratio is improved enhanced effectively even if two motors are at different operating conditions.This paper analyzes harmonic componentsthe and the causes of reverse voltage pulses of the output line voltage waveform. In order to solve this problem, this paper proposes an improved modulation method based on finite state machine (FSM). It makes no more than two legs operated any time when the state changes. By optimizing the distribution of voltage space vector pulse, the output line voltage is improved significantly after optimization which means that the reverse voltage pulses are reduced and the high-order harmonic decreased obviously. The quality of output line voltage is effectively improved.In this paper, a dual motor drive system experimental prototype based on five-leg inverter is built. Traditional modulation strategy, modulation method to improve voltage transfer ratio and modulation based on FSM is verified.