Wireless Power Transmission Circuit and System Design

Antennas play a very important role in wireless power transmission (WPT) systems using microwave since they affect the system transmission efficiency. General requirements for an antenna used for WPT systems are high directivity and narrow beamwidth. This paper presents the design, simulation and fabrication of microstrip patch antenna arrays for close-range WPT systems. Various antenna prototypes such as single patch, 2×2, 2×4, 4×8 and 8×8 microstrip patch antenna arrays working at 2.45 GHz are proposed. The 2×4 microstrip patch antenna array is fabricated and measured using Anritsu 37364D Vector Network Analyzer and NSI2000 Nearfield System. Measurement results show that the fabricated antenna obtains a directivity of 14.7 dBi and a 3 dB beamwidth of 23.2 degree. The experiment with the WPT system is carried out. This paper also presents structure of a WPT system and the role each building block in the system.

This article describes a novel rectifying-antenna design with extended input power range operating at 2.4 GHz for both ambient wireless energy harvesting and wireless power transmission (WPT) systems. The rectenna consists of a 2 × 2 fractal antenna array and a rectifier circuit with a high-power conversion efficiency (PCE) in a wide input power range. This circuit contains two conversion stages based on two different Schottky diodes, and a third stage that dissipates the unconverted input power, which can disturb the harvesting process. These three stages are controlled by a power management block based on circulators, that direct the input power to the adequate stage according to its power range. A prototype of the proposed harvesting system is fabricated and experimentally validated. The measurement results confirm the wide input power range behavior of the designed rectenna with a relatively constant and high PCE (between 58% and 67%) for a power density ranging from 4 to 252 μW/cm2. The proposed solution can be successfully used for both ambient energy harvesting and WPT systems.

Compensation topologies for wireless power transmission system in medical implant applications: A review

This paper presents a development of a low power wireless power transmission system. A phase shift phase-lock loop (PLL) control for WPT was also proposed. The proposed control strategy was used to optimize the phase offset between the fundamental primary side voltage and primary side current at all operating points. Then, the phase compensation can be achieved. In order to verify the proposed control scheme, a hardware prototype of the proposed wireless power transmission (WPT) system has been constructed. The coupling coefficient was measured at different air gaps and lateral offsets. Several simulations and experimental results such as voltage and current measurement of primary voltage and current were reported and discussed.

In this paper are analyzed the main methods of wireless transmission of electrical energy, as well as their applications. For the beginning, there is a brief history of the development of the wireless electric power transmission technology. There are presented the principles of functioning of the main methods of wireless transmission of electrical energy, as well as the technical problems that need to be solved in the future. There are also presented the main applications of this technology, as well as the main companies that produce commercial wireless electrical power transmission equipment. Finally, we present the future opportunities of these wireless power transmission technologies and recommendations for future research topics in this field.

In the context of a smart grid, sensors act as real-time monitoring devices. They enable the continuous assessment of the performance index for high-voltage transmission lines. Compared with the traditional lithium battery energy supply system, wireless power transmission (WPT) systems not only ensure the safety but also reduce the maintenance schedule. In the process of energy transmission, traditional insulator-clamped WPT systems are susceptible to interference from metal connectors. Moreover, electromagnetic energy leakage can pose threats to the safety of personnel working with charged equipment and the stable operation of nearby conductive sensing devices. This study analyzes the general principles of energy flow in multicoil WPT systems based on the Poynting's theorem. We introduce the energy contraction coefficients to analyze the distribution of electromagnetic energy in the three-coil systems Achieving energy confinement in the system by adding the relay coils. Combined with an engineering background, we establish constraints and optimize the relay coil's radius and position. We clarify the relationship between relay coil parameters and system energy confinement. Through simulations and experiments, it is shown that with a constant system output power, the optimized three-coil systems improve the energy contraction coefficient by 20.9% compared to the initial two-coil system and increase the magnetic flux density contraction coefficient by 19.4%. This effectively enhances the stability of energy transfer and the safety of the external electromagnetic environment in insulator-clamped WPT systems.

This paper observes impact of the various chokes on resonant frequency for the two different topologies of current-mode class-D (CMCD) amplifier used in the transmitter side of wireless power transmission (WPT) system. Both topologies are evaluated through measurements and simulations and the chokes with different inductance values were selected and applied to determine their impact on transmitter performance. In resonant WPT system, in particular transmitter subsystem, we suggest CMCD amplifier with center tapped transmitter coil. The most relevant features that are achieved, using CMCD amplifier with center tapped transmitter coil, in comparison to common CMCD amplifier are decreased choke voltage and significantly lower impact on resonant frequency.

Wireless power transmission (WPT) using magnetic resonance has been attracting increasing attention from power electronics engineers and industry. A number of studies have investigated WPT circuits based on magnetic resonance and have verified the high-efficiency power transmission characteristics of such circuits. However, a 10-MHz-class high-frequency power supply suitable for high-power transmission systems has not been sufficiently investigated. Hence, the authors propose a new circuit topology for high-power and high-frequency inverter systems suitable for high-power wireless power transmission. In this paper, the authors propose a novel high-frequency current-output-type inverter circuit topology using an immittance conversion element, parallel operation of the two proposed inverters and a WPT circuit using magnetic resonance at the parallel resonant frequency. In the prototype tests, a system consisting of a single-unit inverter and the proposed WPT circuit provides an output power in excess of 100 W when the conversion efficiencies of the inverter and the entire system are 85.4% and 80.2%, respectively. In addition, parallel operation of the two proposed inverters with a load RLC circuit yields an output power greater than 290 W, which is twice the output power of a unit of the proposed inverter. Thus, the conversion efficiency of the inverter exceeds 80.4%.

An overall view of past, present and proposed wireless space power transmission projects is presented. Activities in the United States, Canada, France, the former Soviet Union and Japan are highlighted. The recent Japan-US space-to-space wireless power transmission demonstration ISYMETS is described as are the 1995 demonstrations of wireless power transmission systems in Kyoto, Japan, at the WPT 95 conference.

The strong reactive near-field wireless power transmission (WPT) systems induce electric fields in the body tissue of persons in their close vicinity. This may pose potential direct health hazards or indirect risks via interference with medical implants. In this paper, the safety guidelines and the fundamental coupling mechanisms of the human body with the electromagnetic near fields of WPT are reviewed as well as the methodology and the instrumentation for the demonstration of the safety of such systems operating between 100 kHz and 50 MHz. Based on this review, the advantages and shortcomings of state-of-the-art numerical and experimental techniques are discussed and applied to a generic WPT operating at 8 MHz. Finally, current research needs are identified which include: 1) the extension of safety guidelines for coverage of persons with implants; 2) more computationally efficient full-wave solvers; 3) higher quality human models which cover different population groups and include improved models of nerve tissue; 4) experimental dosimetric methods for the WPT frequency range; and 5) product standards to demonstrate safety of specific WPT.

To realize electromagnetic safety of wireless power transmission (WPT) system for electric vehicle (EV), the shielding methods should be analyzed. This paper proposes a method of using assistant reactive shielding coils to cancel the electromagnetic field (EMF) outside the working area of WPT system. By tuning compensation capacitance of shielding coil automatically, we design 3 cases with different location and shape of coils to achieve reactive shielding. By comparison and simulation, placing ring shielding coils above receiving (Rx) pad and under transmitting (Tx) pad is the best way to suppress EMF of WPT system's non-working area. The shielding coils' radius is slightly bigger than coupling coils' outer radius. This paper also provides a new method to realize WPT shielding system's automatic adjustment for resonance. Besides, assistant reactive shielding coils' cost is lower than traditional aluminum plate.

Wireless power transmission (WPT) technology has been widely applied in various fields, such as electric vehicles and wireless sensor networks. Magnetic coupling resonance technology is one of the most important technologies in wireless power transmission. A large number of experimental studies have shown that wireless power transmission systems have good power transmission performances when they work at the natural frequencies. Nevertheless, many relevant parameters‘ differences in design, such as the choice of coupling coil structures and parameters, the coupling coefficient between transmitting coil and receiving coil and the quality factor of each coil, will lead to changes in terms of transmission performances. To reduce these adverse effects and make the wireless power transmission system maintain better transmission efficiency, a resonant magnetic coupling four-coil model with Series-Series-Series-Series (SSSS) structure is established based on the equivalent circuit theory. An optimization factor α is proposed to evaluate the transmission performances of the wireless power transmission system. Parameters characteristics of the optimization factor α between the excitation coil and the transmitter coil in the established symmetric structural system model are analyzed in detail. By means of the simulation analysis software MATLAB, the influences of the distance between the excitation coil and the transmitter coil and their respective radius on the optimization factor α are analyzed. And the variation tendency of α with regard to the parameters of the excitation coil and the transmission coil is clarified. Also, the influence of the optimization factor α on the transmission efficiency of the wireless power transmission system is analyzed and the variation trend is cleared up. By studying the optimization factor, the selection specification of system parameters is analyzed and provides a theoretical basis for system design. A resonant magnetic coupling four-coil wireless power transmission experimental system was built through optimization design. Theoretical models and experimental measures are in good agreement in terms of the influence of system transmission distance on transmission efficiency. After optimization, the transmission efficiency is increased by 3.1% compared with the system before optimization

The paper presents the derivation of systems of equations, relating the efficiency of the wireless power transmission system (WPT) with the transmitted power and the distance or displacement between the receiving and transmitting spiral coils. The initial data for the derivation of equation systems were obtained on a prototype assembly of a bidirectional WPT. Experiments were performed in which the values of efficiency and transmitted power were obtained for distances in the range up to 25 mm and displacements between the receiving and transmitting coils in the range up to 30 mm. When the distance between the coils with a diameter of 62 mm is changed to 25 mm, the maximum transmitted power of the prototype system is reduced by ~2.8 times compared to the assembly with minimum distance between the coils. With an axial displacement between the coils equal to approximately half the diameter of the coils, the maximum transmitted power drops by ~3.5 times. Several expressions have been proposed for converting the characteristics of the prototype into relative units and connecting them with the geometric parameters of the coil. The presented systems of equations can be used to develop algorithms that provide for identification of various kinds of interference during the operation of WPT, affecting the efficiency and transmitted power. When operating a WPT as part of a mobile autonomous robotic system, the derived systems of equations will make it possible to assess the feasibility of transferring energy between robots or a charging station and a robot at a given relative position.KeywordsWireless power transmission systemEfficiency equationsPower transmission distanceSpiral coilsMobile robotics

This paper presents the theory and design of coupled resonant systems for wireless power transmission (WPT) system for the next generation electrical power transfer application. A detailed analysis and experimental design of solenoid and spiral coil based wireless power transmitter and receivers are addressed. Experimentally, it is found that the power transfer efficiency reaches the maximum at resonant frequency, and the efficiency decrease with the increase of the distance between the source transmitter and receiver coils. The performance of the proposed WPT has been studied and a laboratory model is developed for experimental verification. The results show that spiral based WPT system shows better results.

Recently the wireless power transmission (WPT) technology is a priority research direction in the world. The WPT can be divided into two main orientations: firstly WPT using inductive coupling, resonant coupling, and secondly WPT using the beam power technologies by microwave power beam and laser power beam. The WPT system with the beam power technology consists of a solar power satellite and rectenna array. The solar power satellite is composed of a large solar cell matrix to receive solar energy, microwave devices (or laser devices) to convert from solar energy into microwave (or laser) beam power, and a transmitting antenna array to transmit the power beam via the space to the rectenna array. The rectenna array receives microwave power beam and rectifies to DC power. The most important requirement for WPT using beam power technology is high collection efficiency. In order to get high collection efficiency, the rectenna array has to fulfill optimal requirement of its efficiency. This requirement plays a very important role in a wireless power transmission system. In this paper, we represent the simulation, design and the experimental fabrication of rectenna array with 4-element and 32-element rectenna array using micro strip dipole antennas with the integrated J shaped balun at the frequency of 2.45 GHz. Some simulation, design and fabrication results as well as several experimental measurement results of 4-element rectenna were shown and discussed.