Power-electronic systems and components thereof such as electrical-energy storage apparatuses/subsystems in the form of supercapacitors and power-electronic apparatuses/subsystems are disclosed. A supercapacitor has a conductive or semi-conductive first metasurface layer, a conductive or semi-conductive second metasurface layer, and a dielectric layer sandwiched between the first and the second metasurface layers for electrically insulating the first metasurface layer from the second metasurface layer. An electrical power conversion apparatus has a first power conversion circuitry for converting a first portion of electrical power received from an electrical power source and outputting the converted electrical power via an output. The electrical power conversion apparatus also has one or more direct power transfer (DPT) channels electrically coupling to the first power conversion circuitry in parallel for bypassing the first power conversion circuitry and directing transferring a second portion of the electrical power received from the electrical power source to the output.