This paper presents a solar-PV (photo-voltaic) system with wireless power transfer (WPT) and battery storage backup in various state changes throughout the day. A 378W PV module is connected with high-frequency converters at 20 kHz switching frequency and an LCL compensation network for the wireless power transfer across the primary and the pick-up coil. For the power backup, a 48V Li-ion battery is used for the storage. The voltage and current characteristics of the battery and IPT (Inductive Power Transfer) interface are investigated when the PV module is at STC(Standard Test Conditions). The simulation result shows that a complete analysis of wireless power transfer of PV power with battery storage can be achieved to form a robust and reliable system for low voltage(LV) applications. This paper also studies the effect of a variable load on the battery current and voltage respectively.

This paper presents a second-order sliding-mode (SOSM) control approach for inductively coupled power transfer (ICPT) systems based on zero-current-switching. A second-order dc equivalent model of a series-series (SS) compensated ICPT system is established by replacing its primary side with a dc source and simplifying the rectifier on the secondary side. A SOSM controller implemented by a digital state machine is designed to regulate the output voltage of ICPT systems by controlling the switches on the primary side. Parameters of the controller are derived with a simplified dc equivalent circuit model of the ICPT system. The proposed controller achieves fast dynamic response, robustness against load disturbances and parameter uncertainties without requiring current sensing or any integral terms in the controller. As a result, the output voltage of the system can reach steady state without any overshoots in several switching actions under load disturbances or mutual inductance variations. Simulation results on a 12V/2A system verify the effeteness of the proposed approach.

This paper presents a new approach to designing an indoor Wi-Fi energy harvester with a bridgeless converter that operates at low incident power. The design approach started with the analysis of the incident power available at a point of the harvester with certain harvesting distance, dimension, position, and height from the ground plane. Then, a simple single-plane antenna was proposed. Finally, a bridgeless converter circuit was proposed to boost the voltage at very low input power. The analysis showed typical calculated incident power at the antenna on the pathway of the transmitter is approximately 15μW/m2and in the case of non-line-of-sight, the values dropped down to about 2 μW/m2. The proposed system has been tested in an indoor environment where the measured signal strength is between -60 dBm to -50 dBm; and the output voltage and power at the output of the converter were measured as 3.86 mV and 0.15 nW, respectively, a 100 kΩ resistive load is connected for testing. An additional boost-buffer module was connected to the converter circuit for further voltage boost. It was found that the energy harvester stabilizes after 38 hours of operation and 1.8 V was measured at the output supercapacitor (1000 uF), meaning 1.67 J of energy has been stored for driving external low power devices.

Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies at large distances compared to the transmitting element dimensions, thereby increasing the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field of research, different approaches have been proposed to predict the behaviour of these systems from the physical theory of resonators (coupled-mode theory) and circuit theory. Although the equivalence of these models for a point-to-point link has already been studied together with the performance metrics Power Transferred to the Load (PTL) and Power Transfer Efficiency (PTE), the new challenges and applications of this technology emphasize the necessity of analytical models to predict and assess the behavior of Multiple Input - Multiple Output (MIMO) links. In this article we revisit the current analytical models from the MIMO perspective, derive the analytical equations for the equivalent performance metrics PTE and PTL and demonstrate how to maximize them in a non-radiative resonant wireless power transfer link from a circuit-centric point of view, providing design guidelines in terms of optimal source and load impedances. This work concludes with a prospective discussion on open challenges of WPT.

Wireless charging platforms are becoming popular due to the elimination of electrical connectors. However, generating a uniform magnetic field over the charging pad is technically a challenging task, and normally it ends up using a charging pad with multi-layers and coils. This paper proposes a novel wireless charging pad based on travelling magnetic field. The moving feature of the proposed magnetic field simplifies the pad to a simple single-layer design, while giving the free positioning of the receiver coil above the pad. The basic principle of operation of the new design is presented in details. A 3D finite element model is developed to study the magnetic coupling property, particularly the uniformity of the magnetic field distribution above the pad. A complete practical set-up is constructed to evaluate the system performance. The simulation results revealed a reasonably uniform magnetic field distribution above the charging pad without any ‘dead areas’ with zero magnetic field. The practical results has demonstrated that the average uncompensated power (Su=Isc.Voc) transferred to the receiver coil is about 1.3 VA, providing a maximum power transfer potential of 6.5W for charging consumer electronic devices such as mobile phones if the pickup circuit is tuned at a quality factor Q of 5.

Modern wireless power transfer (WPT) technology emerges and advances with the advent of high frequency power electronic devices. However, the circuit topologies using these devices to generate high frequency currents or voltages remain much the same over the years. In this paper, a new type of current-fed power converter using energy injection approach is proposed for inductive power transfer (IPT) applications. The idea of the new converter comes from the study of three existing converters: the push pull resonant converter, the voltage fed energy injection converter, and the Class E converter. The circuit topology, basic operating principle and control methods of the new converter are explained and analyzed in details. Simulation and practical experiments are conducted for circuit verification and performance evaluation. The proposed converter can achieve full resonance and realize zero voltage switching (ZVS) with no dead time requirement. As a result, it has the potential to operate at much higher frequencies compared to the voltage fed energy injection converter which suffers from the deadline problem. Moreover, it overcomes the drawback of Class E converters which normally operate at open-loop with no feedback control from the resonant tank to coordinate the precise soft switching operation.

Developing a resonant inductively powered system for implantable devices is difficult due to the constraints on the operating coupling range, power level, and size. It is not trivial to determine the suitable resonant topology, tuning capacitors, power transfer coils, and operating frequency. Often the system parameters, such as the operating frequency, are designed using nominal values or a trial and error approach. We present a detailed numerical model which included frequency dependent parameters to accurately model the resonant system of an inductive power system, so that unexpected characteristics that might be hidden through approximations will be revealed. A procedure based on numerical simulation in the frequency domain is proposed to determine the resonant topology and tuning capacitances for achieving maximum efficiency with a set of power transfer coils across the specified operating coupling and loading conditions. A wireless power supply has been designed using this methodology, which increased the power efficiency by 4% on average over the full operating conditions.