Developing distributed renewable energy sources is essential for constructing modern power systems; however, the low output voltages (24–48 V) of these sources do not allow direct connection to high-voltage grid-tied systems or standard 400 V DC buses. Although various high-gain DC–DC converters have been introduced, most suffer from hard-switching losses or lack common-ground characteristics, severely compromising their conversion efficiency and forcing the use of expensive differential probes during experimental testing. To resolve these efficiency and structural bottlenecks, this research designs a new quasi-resonant, soft-switching, high-gain DC–DC converter based on the Sepic topology. The objective is to simultaneously achieve high voltage gain, elevated efficiency, and common-ground characteristics to simplify waveform observation and reduce hardware costs. Crucially, the proposed topology deduction and soft-switching design methodologies are intended for extension into the practical sessions of the “Power Electronics Technology” course to develop students’ complex engineering problem-solving and innovative capabilities.

A systematic methodology spanning topology derivation, mathematical modeling, and experimental prototyping is developed. Starting from the basic Sepic circuit, a Y-source network is integrated to utilize the coupled inductor turn ratio for high-ratio voltage boosting. A passive clamping circuit is implemented to recycle leakage energy and suppress switch-voltage spikes. Then, a three-winding coupled-inductor voltage multiplier cell is embedded, followed by a unique branch reconfiguration strategy to eliminate internal loop conflicts and achieve a stable, common-ground layout. Under continuous conduction mode, the converter exhibits four distinct operating modes within a single switching cycle. A complete mathematical model based on Kirchhoff’s voltage law and volt-second balance is established to derive the formulas for the voltage gain and component stresses. A quasi-resonant mechanism is established via the interaction between the leakage inductance and intermediate capacitors. In particular, the resonance frequency is configured higher than the switching frequency to achieve zero-voltage switching (ZVS) for the switch and zero-current switching (ZCS) for the diodes. Finally, a 200 W experimental prototype is fabricated to verify the operational performance of the proposed converter.

Steady-state experimental tests were conducted on the 200 W prototype under a 37.5 V DC input voltage, with a duty cycle of 0.4 and turn ratios of n₂ = 0.5 and n₃ = 1.5. Under these conditions, the converter steps up the 37.5 V input to a stable 400 V output, verifying a practical voltage gain of 10.67, which closely matches that of the theoretical model. In addition, the main switch operates with ZVS at turn-on with its voltage stress clamped at 60 V, while the clamp and multiplier diodes achieve ZCS turn-off with minimized reverse recovery. Moreover, the average input current is 5.6 A, yielding a peak overall system efficiency of 95.23%. Furthermore, under full-load operation at 23 ℃, the peak component temperature stabilizes at 40.2 ℃, and the low temperature rise of 17.2 ℃ validates the effectiveness of the quasi-resonant loss reduction.

The proposed converter successfully fulfills all design expectations by effectively resolving the trade-off between ultra-high voltage gain and conversion efficiency. Experimental results confirm its high efficiency (95.23%), excellent thermal stability, and high suitability for low-voltage renewable energy integration. Crucially, the common-ground structure simplifies the measurement layout, eliminating the need for expensive differential probes while significantly reducing experimental research costs. Furthermore, the systematic engineering methodology encompassing rigorous topology deduction and soft-switching optimization provides a structured paradigm for the practical modules of the “Power Electronics Technology” course, effectively guiding students through complex engineering problem-solving and enhancing their innovative practical capabilities.

The accelerated progress in power electronics technology, notably the pervasive implementation of Insulated Gate Bipolar Transistors in critical domains such as renewable energy generation and flexible HVDC transmission systems, has resulted in unparalleled demands on insulation systems. These systems are subject to extreme operational stresses that include high-frequency, high-amplitude voltage stresses generated by pulse width modulation techniques, coupled with significant Joule heating effects. This leads to the formation of severe electro-thermal multi-stress coupling conditions, which challenge the long-term reliability of insulating materials such as epoxy resin. In such conditions, microscopic defects can initiate an electrical treeing phenomenon, a destructive occurrence that can significantly reduce dielectric strength. Nevertheless, the microscopic evolution of electrical trees is abstract and complex, rendering it difficult for students to comprehend the fundamental physical mechanisms. The primary objective of the present research is to address the prevailing educational challenge through the development of an integrated teaching and research platform. This platform is designed to integrate experimental observation with simulation methodology. This platform aims to transform the abstract process of insulation degradation into a tangible, visible phenomenon, thus enabling a more profound understanding of failure mechanisms under high-frequency and high-temperature conditions.

A comprehensive “experiment-simulation” methodology was employed in this study. The experimental component incorporates a platform that is integrated with four specialized modules: a high-voltage pulse power supply, a precise temperature control system, an observation unit, and an imaging system. The configuration of the setup utilizes a needle-plane electrode configuration within a polytetrafluoroethylene (PTFE) mold to simulate electric field concentration. The utilization of a high-speed CCD camera in conjunction with a high-magnification stereomicroscope facilitates the capture of the real-time morphology of electrical trees in epoxy resin. In the domain of simulations, the research introduces a sophisticated multi-physics model grounded in the phase-field method. In contrast to conventional models that prioritize electric fields, this model incorporates five critical energy components: phase separation free energy, gradient energy, electrostatic energy, Joule heating energy, and strain energy. The model solves heat balance equations to account for temperature effects on material properties, such as dielectric loss. This allows for the prediction of early-stage tree growth under coupled electro-thermal fields.

The experimental results indicated the presence of distinct treeing behaviors in response to varying stress conditions. When subjected to high-frequency stress at ambient temperature (10 kHz, 25 ℃), trees exhibited accelerated growth, forming distinctive “ball-chain-like” carbonized channels as a result of substantial localized energy deposition. In contrast, when subjected to low-frequency (50 Hz) and high-temperature (90 ℃) conditions, a phenomenon of “growth stagnation” emerged. This phenomenon was characterized by the facilitation of bond breaking by heat, while the low frequency allowed for sufficient time for space charge accumulation to shield the electric field, thereby inhibiting its propagation. Under conditions of synergistic high frequency (10 kHz) and high temperature (90 ℃), the most severe degradation was observed, resulting in rapid, dense branching and the formation of large, bubble-like carbonized areas. The simulation model effectively predicted initial propagation paths that aligned with experimental observations. However, as these organisms developed, discrepancies became apparent: while actual trees demonstrated complex, stochastic three-dimensional branching patterns, simulations remained two-dimensional and lacked this complexity. This divergence underscores the limitations of idealized homogeneity assumptions in modeling complex physical-chemical processes.

The present study successfully validates an integrated platform that serves to bridge the gap between theoretical modeling and practical observation in the domain of high-voltage insulation education. The platform successfully visualizes the synergistic effects of frequency and temperature on electrical treeing. It reveals mechanisms ranging from rapid carbonization to charge-induced stagnation. While phase-field simulations offer valuable insights into early-stage driving forces, a comparison with experimental data underscores the complexity of material inhomogeneity in real-world scenarios. This “experiment-simulation” approach significantly enhances students’ comprehension of multi-physics coupling and cultivates essential engineering competencies for insulation system design and reliability assessment for modern power electronics.