State Grid Corporation of China (China)

The symmetrical phase-shift modulation of the three-to-two-level neutral-point-clamped dual-active-bridge (3/2LNPC-DAB) DC-DC converter has more controllable control variables than the conventional two-level DAB converter. The increase in control variables leads to an increase in the number of operating modes and inequality constraints, significantly complicating the modulation optimization process. To enhance the efficiency of the converter, this paper proposes an optimized quadruple phase-shift (OQPS) modulation considering both conduction losses and switching losses. Five effective operating modes that have the potential to achieve zero-voltage-switching (ZVS) for all switching devices are screened based on the ZVS inequality constraints. The inductor peak current is used as an optimization objective to minimize the conduction losses while satisfying the ZVS inequality constraints. The boundary of the feasible region satisfied by the optimal solution is derived by numerical optimization. Based on this, an improved Lagrange function and Karush-Kuhn-Tucker (KKT) conditions are proposed to solve the analytical solution of OQPS modulation. Finally, the proposed OQPS modulation is applied to a 1.6kW prototype to verify the improvement of efficiency. The designed prototype can achieve 96.9% peak efficiency at 300V input and 150V output voltages. Compared with previous modulations, the proposed OQPS modulation can achieve the highest efficiency in the full power range.

Power-over-fiber (PoF) systems suffer from energy waste and instability under dynamic conditions due to fixed laser output and time-varying load demands. This study presents a closed-loop feedback control mechanism based on capacitor-voltage monitoring, which effectively filters transient disturbances while accurately reflecting system energy balance. Employing an 808 nm laser with 12 W maximum output, the system uses a GaAs-based photovoltaic power converter (PPC) with high measured MPP efficiency under our test conditions and a Proportional-Integral-Derivative (PID) algorithm to achieve rapid response, automatic compensation for fiber losses up to 1500 m, and 17.9% end-to-end efficiency over 500 m fiber, while ensuring long-term reliability with stable operation exceeding 3000 s. A practical WiFi access scenario with live video streaming is further demonstrated, validating stable closed-loop powering under traffic-driven load dynamics.

ABSTRACT In recent years, extreme cold disasters have occurred frequently worldwide. The security of rural distribution network is threatened. The current research on enhancing the resilience of distribution network fails to consider the changes in the operating characteristics and efficiency of equipment under extreme cold disasters. To address this, this paper uses hydrogen‐integrated energy systems (HIES) to enhance the resilience of rural distribution network under extreme cold disasters. The method considers ensuring the power supply of rural lifeline load. A power support capability evaluation model of HIES is established. The model takes into account the impacts of low‐temperature conditions on the operational characteristics and efficiency of hydrogen energy equipment and photovoltaic equipment. An energy demand model considering livelihood security lifeline load, public service lifeline load and cultivation‐breeding lifeline load under extreme cold disasters is established. A rural distribution network resilience enhancement model is developed. Its goal is to maximise the restored energy demand of lifeline load. The example shows that the lifeline load recovery rate is increased by 38.98% and the primary load recovery rate is increased by 5.44% using the method proposed in this paper.