Research Of UPS Parallel System Based On Power Control

Uninterruptible power supply (UPS) has the advantages of sustainable, stable and uninterrupted power supply, UPS paralleling system formed with N+X redundancy system, which has the advantages of strong scalability, high reliability and easy maintenance and management, so they are used more and more widely in power supply and power failure protection for important load.UPS redundant parallel can enhance the reliability of the whole system, how to reduce and even eliminate the circulation is the key to realize the UPS unit parallel operation problem. In terms of control flow, this paper analyzes the cause of circulation in parallel connection system, aiming at the effects of phase difference for circulation, designed a digital phase-locked loop, and ensure the phase and frequency of all the UPS inverter synchronization. Mainly introduced master-slave mode and distributed which are interconnected line control scheme. By comparing the two control scheme,the distributed control system i is better. By simulation to check the effect of flow.First, this paper establishes two UPS module parallel equivalent circuit as an example, studied the average power flow control strategy. Because both active power and reactive power flow control cannot eliminate DC circulation, circulation is not accused of DC can make DC bus voltage asymmetry, lead to over-voltage protection, so this article on the basis of active power and reactive power flow control, join current DC component control, effectively restrain DC circulation, improve the effect of the flow. Finally established the simulation model of with and without DC circulation to adjust strategies to compare, flow effects are verified.