A Dual-Energy-Source Uninterruptible Power Supply (UPS)

In this paper, a dual-energy-source uninterruptible power supply system (DES UPS) is investigated. There are two energy sources with independent infrastructures in the system, grid and natural gas pipeline. It boosts the reliability of traditional UPS. Grid is the primary energy source, while natural gas generator (NG-Gen) acts as the secondary energy source for long-time backup. Firstly, reliability and source cost of the system are evaluated. Then, cold-start characteristic of NG-Gen is analyzed and the seamless transfer strategy of DES UPS is proposed based on the cold-start characteristic of NG-Gen. It achieves the uninterruptible load power supply when system operation mode changes at the grid fault. Then the control diagram is designed accordingly and state of the system during working mode transfer is analyzed. Finally, the concept and control strategy of DES UPS are verified in a 10kW prototype.