## 1 Introduction
Accordingly, scholars have proposed an iterative method for short-circuit calculation of distribution networks containing renewable DGs [22; 23; 24] to fully take into account the influence of the strong coupling relationship between the fault current of DGs and the voltage at the point of common coupling (PCC). In these methods, the initial voltage values of all buses in the distribution network after the fault is obtained via traditional short-circuit current calculation methods, in which the DGs are regarded as ideal current or voltage sources. And then, the change in the node voltage caused by the output current of DGs under LVRT strategies is repetitively and iteratively calculated to form the final short-circuit current of each branch of the distribution network. The calculation results in these papers show that the accuracy of short circuit current calculation can be improved by 10% compared with the traditional simplified methods. In fact, the output power of renewable DGs has strong randomness [25; 26; 27], and the average hourly output in 24 h is not the same. Hence, the node voltage has strong volatility during normal daily operation of the distribution network. The calculation of short-circuit current according to the rated power output of DGs is not in line with the actual situation and affects the sensitivity calibration of over-current protection. In other words, the node voltage along the feeder varies with the output power of DGs and the electricity loads. Hence, the short-circuit current in electrical distribution systems should be calculated based on the real-time operation conditions of the distribution network. To address the abovementioned problems, existing short-circuit current calculation methods are analyzed for the distribution network with renewable DGs. And then, the daily output power of PV stations is analyzed, clustered, and modeled for the real-time power flow calculation of distribution networks, as well as the residential loads. Once the node voltage value before the fault time is obtained in real time by considering the source-load stochasticity, an improved iterative short-circuit current calculation algorithm is proposed and verified considering high penetration of DGs with LVRT strategies. The main contributions of this paper are given as follows:  
* An improved iterative short-circuit current calculation algorithm is proposed considering real-time output power of DGs and electricity loads under high penetration of DGs with LVRT strategies;* Output power fluctuation analysis of PV stations of residential loads are conducted via clustering algorithms. Several typical daily curves of PV stations and electricity loads are obtained and used to obtain the typical daily short-circuit current curves for all branches. The rest of this paper is organized as follows. Section 2 introduces a traditional simplified short-circuit current calculation in a distribution network with renewable DGs, including the equivalent short-circuit analysis networks, equivalent model of renewable DGs for short-circuit calculation, and the corresponding calculation equations. Section 3 provides a detailed illustration of our proposed real-time short-circuit current calculation considering fluctuation in DGs and loads. Section 4 presents the analysis and verification short-circuit results of a 69-node distribution network with different scales of PV stations using our proposed method and traditional calculation methods. Section 5 summarizes the research findings and discusses future prospects.