This study presents a novel structure proposal of a variable inductance high-frequency transformer for enhancement power level of a dual-active-bridge (DAB) converter. The DAB converter is a solid-state transformer (SST) that requires high efficiency, power density, flexibility, and stability. Variable inductance facilitates achieving and extending maximum power levels. The proposed method adjusts the inductance based on the core insertion conditions of the transformer used in the DAB converter without requiring an additional inductor. The method was verified by analyzing the variable inductance characteristics of the transformer based on core insertion conditions via finite element analysis (FEA) and simulation and experiments within the variable inductance range.

The installed capacity of photovoltaic (PV) systems has increased significantly over the past few decades, and related technologies have advanced significantly. The electrical characteristics of a PV system change nonlinearly based on irradiation and temperature, and the I–V characteristic curve, expressed in terms of the voltage and current, is used to verify these characteristics. The maximum power point tracking (MPPT) control method was applied to maximize the performance of the PV system. Voltage and current sensors are used to control the I–V characteristic curve and MPPT; however, current sensors have various disadvantages in terms of price and system configuration. Therefore, this study presents a method for calculating the current of a PV system using the charging characteristics of a capacitor. The method presented in this paper analyzes the I–V characteristic curve’s qualities through simulations and experiments under normal, shaded, and mismatched conditions of the PV module.

This study investigates the impact of photovoltaic (PV) module configurations on the output performance of power-to-heat (P2H) systems under fixed-load conditions, considering regional solar irradiance characteristics in South Korea. Through both simulations and experimental analyses using a P2H testbed, two configurations, namely 6S (6Series) and 3S2P (3Series-2Parallel), were compared under varying irradiance levels. Based on an irradiance threshold of 533.2 W/m², an adaptive PV configuration method is proposed to optimize energy output. The performance of the resistive-heating-based P2H system was evaluated using solar radiation data from major regions of Korea. Experimental results demonstrated that this approach can increase output power by up to 65% at low irradiance and improve annual energy yield by about 16% compared with a fixed configuration. This study offers practical guidance for designing P2H systems tailored to the climatic conditions in Korea.