Multi-input single output wireless power transmission (MISO-WPT) systems have decisive advantages concerning flexible receiver position in comparison to single coil systems. However, the supply of the primary side brings a large uncertainty in case of variable positions of the secondary side. In this paper, a compact multiplexed primary side electronic circuit is proposed, which includes only one signal generator, a passive peak detector, a communication module, and a compensation capacitor. The novel approach has been studied and evaluated for a MISO-WPT system having a 16 coils on primary side and one coil on secondary side having the double diameter. Results show that a standard microcontroller, in this case an STM32, is sufficient for the control of the whole system, so that the costs and the energy consumption are significantly reduced. An activation strategy has been proposed, which allows to determine the optimal transmitting coil for each position of the receiving coil and to switch it on. The time-to-start-charging at different positions of the receiving coil and different number of neighbors has been determined. It remains in all cases under 2.5 s.

Self-powered energy management circuits make energy harvesting converters more efficient and more reliable. This paper presents an improvement of a Maximum Power Point Tracking (MPPT) technique applied on a Parallel Synchronized Switch Harvesting on Inductor (P-SSHI) technique for piezoelectric vibration converters. The aims are to detect the unstable vibrational state, optimize the output voltage and maximize the output power of the piezoelectric transducer. First, the P-SSHI technique is implemented without an MPPT technique. Then, an MPPT technique based on Fractional Open Circuit (FOC) voltage method is implemented. An improvement of the FOC method is proposed to enhance the capability of the Piezoelectric Energy Harvesting (PEH) system. The comparison between different simulation results shows that by using the same input parameters, the maximum efficiency for the PEH system based on the P-SSHI technique implemented without MPPT is 8.82 % whereas the maximum efficiency of the system based on the (FOC) voltage MPPT method is 13.77 %. A significant improvement of the PEH system is obtained by using the modified (FOC) method, where the efficiency reached 24.59 %.

Inductive wireless power transfer is a promising technology for powering smart wearable devices. The spiral coil shape is widely used in wireless power transfer applications. Nevertheless, during the coil design process, there are many challenges to overcome considering all the design constraints. The most important is to determine the optimal coil parameters (internal radius, external radius, spacing, wire width, and conductive wire) with the aim of obtaining the highest coil quality factor. Coil modeling is very important for the wireless power transfer system’s efficiency. Indeed, it is challenging because it requires a high computational effort and has convergence problems. In this paper, we propose a new approach for the approximation of spiral coils through concentric circular turns to reduce the computational effort. The mathematical model determines the optimal coil parameters to obtain the highest coil quality factor. We have chosen the smart textile as an application. The system operates at a frequency of 100 Khz considering the $Q_i$ guidelines. To validate this approach, we compared the approximated circular coil model with the spiral coil model through a finite element method simulation using the COMSOL software. The obtained results show that the proposed approximation reduces the complexity of the coil design process and performs well compared to the model corresponding to the spiral shape, without significantly modifying the coil inductance. For a wire width smaller than 1 mm, the total deviation is around 4% in terms of the coil quality factor in a predetermined domain of its parameters.