## 1 Introduction
As seen in [10], a 380 V\({}_{\text{DC}}\) data center as a part of direct current (DC) _u_grid at Duke Energy was presented. A \"solar-to-EV\" project was performed at the San Diego Zoo to present how energy storage, EV charging and solar energy can be successfully integrated in autonomous electric vehicle _u_grid [11]. SIEMENS now is trying to develop blockchain technology in the New York Brooklyn _u_grid system [12]. Different types of _u_grid systems can scale to be economically efficient, environmentally supportive, and produce varied levels of self-sustainable power. Based on these _u_grid categories, research related to _u_grid technology includes: (1) distributed energy resource (DER) integration technology; (2) _u_grid grid-supporting capability; (3) applications of  
Figure 1: Taiwan Kinmen Dongkeng C-_u_grid system. power electronics technology in the \(u\)grid, (4) \(u\)grid economics; (5) operation, control and protection of the \(u\)grid; (6) \(u\)grid communication; and (7) standardization and testing of the \(u\)grid. Authors of [13,14] present complete surveys on these issues; and in this paper, the residential-type C-\(u\)grid is the major object to be investigated and discussed. For residential electricity users, the greatest electricity consumption is generally due to use of various electric appliances, like lighting devices, air conditioners, washing machines etc., for each user. With increasing use of electricity by these users, traditional fuel-type power generations may not able to provide sufficient electricity due to a lacking system upgrade. Furthermore, electricity users are not able to take initiative in participating in demand regulation under the single-direction power flow situation. This may force residential electricity users to face the risk of power outage. To overcome the problem, an application of the C-\(u\)grid is thus introduced, integrated into electric grid to provide sustainable energy sources for electricity supporting services to multiple electricity customers within a community. When the C-\(u\)grid operates into electric grid, the electricity can thus be observed from different locations in system, such as utility grid side, user side, and C-\(u\)grid energy facility (i.e., inverter) output side. Meanwhile, if it can effectively monitor the electricity status on these sides, it will be able to help the electricity users in the C-\(u\)grid carry out correct energy management and system control. Simulations, in addition, are often required for \(u\)grid analysis purposes. Simulations can assist researchers to test different problem scenarios in a simulated domain in an economical way. Overall, this paper thus aims to propose a simulation-based electricity analysis method for a C-\(u\)grid system based on the configuration in Figure 1 by integrating various modelling and simulation methodologies. The rest of this paper is organized as follows. Section 2 describes the C-\(u\)grid system layout and major characteristics of the study. Section 3 illustrates the proposed modelling methodology, simulation mechanism, and control strategy used in the C-\(u\)grid system. Section 4 presents the simulation results of using different test scenarios in this work, and conclusions are given in Section 5.