Research Of Inverter Parallel Technology In High Power AC Drive System

In the recent years, the high power AC drive system developed rapidly. Because of the limitation of the manufacture technique of the high power switching devices, the people proposed many kinds of topology based on the existing power switching devices to satisfy the requirement of the high power inverters. In these kinds of topology, the parallel structure of the inverters was the effective way to realize the high current capacity inverters. So, the research of the parallel inverter control technology had very important application value.This paper taken the drive system supplied by the parallel inverters based on the air-gap-flux oriented control strategy of the synchronous motor as the main research object, researched the circulating current characteristics of the parallel inverters, and analyzed the producing reasons of the fundamental circulating current, dc circulating current, harmonic circulating current, and Zero-Sequence circulating current. The topology and the control strategy were determined based on these research and analysis. The parallel inverters adopted two sets of independent ac-dc-ac rectifier-inverter structure to avoid the Zero-Sequence circulating current, and used the current control strategy to decreased the fundamental circulating current. This paper analyzed and compared the advantages and disadvantages of synchronous control strategy, unified control strategy, and respective control strategy, and then selected the unified control strategy that control the output current and the circulating current together to control the parallel inverters. This paper pointed out the traditional compound control of voltage feed-forward and Current Feedback could not control the circulating current well, proposed the view that Current Feedback was only used in the current loop, then designed the relevant current regulator, and then based on the simulation researched the performance of parallel inverters system when the system used different control strategies. The simulation results showed the designed current regulator was feasible and superior.This paper introduced the experimental platform main circuit of the AC drive system supplied by the parallel inverters, designed the master-slave structure control circuit based on three DSPs and CAN, and compiled the software program of the parallel control strategy. Finally, the paper did the dynamic and static experimentations to examine the performance of the AC drive system. The experimental results verify the parallel control strategy designed by this paper could inhibit the fundamental circulating current, and the dynamic and static performance of the system was fine.