# Special Issue: New Technologies for Power Electronic Converters and Inverters
## 2 A Brief Description of the Papers Published in the Special Issue  
The paper [1] concerns the problem of the high-frequency harmonics suppression using an additional LC filter when driving the high-speed permanent magnet synchronous motor (HPMSM) that has a low inductance. Such an LC filter between the inverter and the HPMSM introduces additional system resonance. Therefore, the adaptive notch filter with the frequency tracking capability is designed in the control system to offset specific resonant peaks by constructing an antiresonant peak. The harmonic contents of HPMSM are significantly reduced, and the dynamic response performance of the control system is improved. Simulation and experiment results prove the effectiveness of the proposed scheme. The paper [2] investigates the roadmap for power loss optimisations of switches and inductors in high-frequency power supply in package (PSiP). Power losses of the integrated Si LDMOSFET switches and air-core inductors are calculated with switching frequency up to 100 MHz and the output power up to 10 W. The paper predicts the efficiency boundaries of PSiPs. The presented power loss optimisations improve the efficiency, which provides potential roadmaps for achieving high-frequency PSiPs. The research [3] introduces an improved control strategy for an active power filter (APF) system. It utilises an adaptive super-twisting sliding mode control (STSMC) scheme. The proposed approach integrates an interval type-2 fuzzy neural network with a self-feedback recursive structure (IT2 FNN-SFR) to enhance the overall performance of the APF system. The IT2 FNN-SFR estimator is used to approximate the unknown nonlinear function within the APF. Simultaneously, the STSMC component is integrated to reduce system chattering, improving control precision and overall system performance. STSMC combines the robustness and simplicity of traditional sliding mode control, effectively addressing the chattering problem. An adaptive law of sliding mode gain is formulated to achieve optimal gain solutions. Experimental validation is successfully conducted to verify the harmonic suppression capability of the control strategy. In the paper [4], the issue of an ageing process's influence on power LEDs' properties is considered. Some measured DC characteristics of these devices and their thermal and optical parameters obtained are presented after considering different values of the ageing process duration. Components soldered using different metal-ceramic composite pastes, e.g., with TiO\({}_{2}\), were tested. It is shown that after the ageing process at elevated temperatures, worse properties were observed for the power LEDs soldered using classical SACX0307 alloy. Most of the samples soldered with reference alloy (not composite) were damaged during the test. The best properties were obtained for the samples soldered with solder paste with the addition of titanium oxide. It is very important because most diodes soldered with classical SACX0307 alloy failed before testing was completed, and some were damaged after 100 h of the test. The paper [4] was distinguished as a Featured Application because the presented results can be useful for engineers working on the reliability of the soldering process. The paper [5] aims to enhance the performance of photovoltaic (PV) systems by developing and evaluating maximum power point tracking (MPPT) algorithms capable of operating effectively under both uniform irradiance and partial shading conditions (PSCs). Two metaheuristic algorithms--Particle Swarm Optimisation (PSO) and Cuckoo Search Optimisation (CSO)--are modelled, implemented, and tested for tracking the global peak power (GPP) in various static and dynamic scenarios. Simulation results indicate that both algorithms accurately and efficiently track the GPP under static uniform and PSCs. Under dynamic conditions, while both the PSO and CSO can initially locate the GPP, they fail to maintain accurate tracking during subsequent intervals.