Accurately determining the daily theoretical line loss rate in low-voltage distribution networks is challenging, making it difficult to quantitatively assess its fluctuation range. To address this issue, this paper proposes a probabilistic analysis method for evaluating the daily theoretical line loss rate in low-voltage distribution networks. First, the actual three-phase four-wire connection of the low-voltage distribution network is considered, and it is assumed that the random models of three-phase voltage, distributed power output, and the three-phase active and reactive power of the distribution transformer on the low-voltage side are known and simulated. Then, source-load correlation is incorporated, and Latin hypercube sampling, combined with the equal probability transform principle and rank correlation, is employed. Finally, using the Monte Carlo simulation method, the probabilistic distribution of power flow and the daily theoretical line loss rate is calculated by the Newton injection current method, taking three-phase unbalance into account. This approach provides a decision-making basis for reducing losses in low voltage distribution networks. Experimental data from the Hengshan Garden low-voltage distribution network validate the effectiveness of the proposed method.

In large hub city power grids, load centers often lack flexible and continuously adjustable reactive power sources across multiple voltage levels, leading to a “hollowing-out” of power supply. This paper proposes a coordinated two-level voltage control optimization method tailored for such “hollowed-out” power grids. In this method, the high-voltage busbar of all controllable power plants within a region are generalized as voltage-dominant nodes, and regional voltage regulation is achieved by minimizing the sum of squared deviations between the busbar voltages and their reference values. Meanwhile, the coordination relationships among upper-level and lower-level regions are explicitly distinguished, and threshold-based control objectives between hierarchical regions are introduced to improve the reactive power support capability of lower-level areas. The effectiveness of the proposed method for regional reactive voltage control in hollowed-out power networks is verified through simulations using a standard test system combined with actual grid data from China.