## 2 Modeling of Novel Electrical Load Resources in UDNs
### 5G Base Stations
In the operation process of 5G base stations, there is a dynamic coupling relationship between relevant parameters and voltage regulation strategies, which has an important impact on the voltage stability of UDNs:  
(1) Downlink data rate and base station power consumption fluctuation  
\(D_{\text{dd}}^{t}\) is one of the key factors affecting the power consumption of 5G base stations. In the \(P_{i,\text{AAU}}^{t}\), the \(P_{\text{idd,AAU}}^{t}\) is closely related to the downlink data rate. As \(D_{\text{dd}}^{t}\) increases, \(P_{\text{idd,AAU}}^{t}\) increases because more data transfers require AAU to consume more energy to process and send. When users watch high-definition videos or download large files, the downlink data rate of 5G base stations will increase, and \(P_{\text{idd,AAU}}^{t}\) will also rise accordingly, resulting in an increase in the total power consumption of the base station. Conversely, when \(D_{\text{dd}}^{t}\) is reduced, such as when the user is engaged in simple instant messaging, \(P_{\text{idd,AAU}}^{t}\) is reduced, the base station power consumption is also reduced, and this fluctuation in power consumption changes in real time as the downlink data rates. (2) The influence of base station power consumption fluctuation on UDNs voltage stability  
As a load in UDNs, 5G base stations' power consumption fluctuations will affect the voltage stability of UDNs. When the base station power consumption increases, the current in the UDNs will increase. According to [PERSON]'s law, when the UDN resistance R is particular, the current increase will increase the line's voltage drop. When multiple 5G base stations experience increased power consumption at the same time, this accumulation of voltage drops may cause local voltage drops in UDNs. Suppose the voltage drop is too significant and exceeds the normal operating voltage range of the UDN device. In that case, the voltage stability of the UDNs will be affected, resulting in abnormal operation of the device and even the safe and reliable operation of the entire UDNs. On the contrary, when the power consumption of the base station is reduced, the current in the UDNs will decrease, and the line voltage drop will also decrease, which has a specific positive impact on the voltage stability of the UDNs. (3) Feedback effect of voltage regulation strategy on relevant parameters:  
In order to maintain the voltage stability of UDNs, some voltage regulation strategies are usually adopted. Power is adjusted in the 5G base station scenario when the UDN voltage drops are detected. The usual way is to reduce base station power consumption by reducing the downlink data rate of some non-critical services. For example, under the premise of ensuring the essential communication quality, reduce the resolution of the video stream, thereby reducing \(D_{\text{dd}}^{t}\), thereby reducing \(P_{\text{idd,AAU}}^{t}\) and the total power consumption of the base station, and alleviate the pressure of UDN voltage drop. Thisregulation strategy will affect the relevant parameters of 5G base stations and achieve a dynamic coupling between the voltage regulation strategy and the base station parameters. If the UDN voltage is too high, the power of the base station can also be appropriately increased to improve the downlink data rate, consume excess electrical energy, and stabilize the UDN voltage.