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Summary Isolated microgrids including several sources of clean energy such as photovoltaic system can be considered as the auxiliary source of power generation. However, unbalanced condition is inevitable in typical microgrids due to asymmetric power generation and consumption. To supply load from different distributed generation, an interface 4‐wire power converter is essential. A 4‐leg inverter with suitable control method is a beneficial solution to support unbalanced loading condition. However, high reliable low‐cost control method achieves more attention to avoid any power outage. As a result, a low‐cost sliding mode control method is proposed in this paper to control the output voltages of the 4‐leg inverter. The proposed method can provide fast dynamic response, fixed switching frequency, high robustness against model parameter mismatches, and external disturbances without any current sensors. Furthermore, to reduce the chattering of the sliding mode control method more effectively, an improved low‐cost method with adaptive discrete coefficient is also proposed. Finally, to evaluate the performance of the proposed method, a 3‐kW test bench with digital control board based on TMS320F28335 processor is provided.

The design of porous gradient scaffolds for bone tissue engineering scaffolds is a relatively new approach. This strategy is based on imitating bone tissue in order to stimulate enhanced cellular responses. An additive manufacturing (AM) method, such as the fused filament fabrication (FFF) system, provides precise and repeatable pore size control. FFF is a well-known AM manufacturing process for producing high-quality parts at a low cost. In this study, polycaprolactone (PCL) and variable hydroxyapatite (HA) amounts were fed into a FFF printer to print four scaffold designs with different porosity gradients. These porous gradient scaffolds were constructed using simple (Si) and shifting (Sh) models, with gradient pore diameters ranging from 400-600 to 400-800 μm. The specimens featured thicker walls but more open cores. The scaffolds' structural, mechanical, and biological properties were evaluated. The results showed that higher gradient porosity and larger pore size led to better biological results, but lower mechanical strength resulted. Furthermore, adding HA increased mechanical strength from 81.8% to 100% and enhanced cellular response. In all scaffolds, an increase in porosity and a decrease in density led to a reduction in compressive strength. The toxicity of the samples and cellular adhesion was evaluated using MTT and DAPI tests on hFOB (human Fetal OsteoBlastic) cells. Alkaline phosphatase and Red Alizarin analyses demonstrated an increase in mineralization as HA content increased.

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