As a critical device for ensuring stable operation in power substations, an Uninterruptible Power Supply (UPS) plays a vital role in maintaining a continuous power supply, improving power quality, and enhancing system reliability. However, startup inrush current and backflow ripple voltage significantly impact the stability of DC power supply equipment. This paper proposes a DC-DC circuit-reuse method with double-line frequency ripple suppression for substation UPS systems. This approach utilizes a boost converter to transfer the double-line frequency pulsation from the DC input to the bus capacitor side, thereby reducing the double-line frequency components at the input. Notably, this Boost converter simultaneously serves as part of the power factor correction (PFC) circuit connecting the grid and DC bus, achieving functional integration that significantly reduces system costs. A 3 kVA UPS experimental platform was constructed to validate the proposed method. The test results demonstrate that while the bus voltage exhibits slight pulsation at double-line frequency, the input current transforms into an approximate DC quantity. This second-harmonic ripple suppression method effectively improves key performance indicators: Startup inrush current decreases by 38% compared to conventional designs, and backflow ripple voltage amplitude is suppressed below 0.5% of the nominal DC voltage. The proposed topology demonstrates superior compatibility with existing substation DC systems and provides a cost-optimized solution for power quality enhancement in critical infrastructure applications.
Sun et al. (Fri,) studied this question.