## 1 Introduction
### Literature Review  
Previous papers can be categorized into three major research areas: power semiconductor technology, phase conversion methods, and Power Quality (PQ) issues in PDSs caused by unbalanced loads. First, several studies have explored the application of power semiconductors in PDSs. These studies highlight the flexibility of power semiconductors in power distribution, emphasizing that power electronics technology enhances energy transmission efficiency, improves overall system performance, and enables the efficient management of distributed energy resources (DERs) in smart grids. Furthermore, power electronics technology has been widely recognized for its role in optimizing PDS operations [1; 2; 3; 4]. Some papers specifically analyze power semiconductor applications in PDSs. For instance, one study examines solid-state transformers applicable to PDSs [5]. Another study discussed modular converter transformers, which are combinations of several converters [6]The second category relates to other phase conversion methods. Prior research includes a study on converting three phases to single phases for traction power supply [7], and another about controlling DC/AC converters in unbalanced three-phase systems [8]. Previous papers that discuss a topology most similar to the one proposed in this paper can also be found [9; 10]. Despite the similar topology, the control method is different, and this paper differs in that it uniquely investigates experiments on various actual loads (nonlinear, unbalanced, and motor loads), fault current tests, and field tests of the PDS. Therefore, further verification is required to assess its applicability to an actual PDS. The specific differences are presented in the comparative analysis shown in Table 1.  
There are other methods besides those utilizing power semiconductors for phase conversion. These include static phase converter and rotary phase converter methods [11]. The two methods are more economic feasibility than the approach proposed in this paper, but they are primarily suitable for single-load applications within PDS. However, they convert to a three-phase 220 V input, not three-phase 380 V. Therefore, they require an additional transformer when converting a three-phase 220 V input to three-phase 380 V.  
The final previously published paper to mention discusses the impact of power semiconductors on a PDS. In an STPC, not only are three-phase loads connected, but also single-phase loads, which can either be evenly distributed across phases or concentrated on a specific phase. Among the previous papers, there was a paper on improving PQ due to load imbalance in LVDSs [12]. In addition to the aspect of imbalance, there are numerous papers that have focused on PQ. Unlike PTSs, various loads are connected to the PDS, so research on harmonics is essential when studying new distribution equipment. Previous studies include papers on PQ compensation methods according to DER interconnection [13; 14], papers on Total Harmonic Distortion (THD) caused by power semiconductor equipment [15], and papers on control methods for PQ in microgrids [16]. Unlike previous papers that primarily focused on laboratory-level validation or theoretical modeling, this paper conducts practical testing on actual PDSs under diverse load conditions. Several studies have addressed short-circuit behavior and PQ issues in PDS with inverter-based distributed generation, including the influence of transformer topology and temporary overvoltage phenomena [17; 18]. These studies offer valuable insights into protection coordination strategies and grid behavior under abnormal operating conditions;