Research On Problems Of Wireless Power Transferring System Fed By Switching Power

With the rapid development of electronic products, the power supply has become a bottleneck because dragging cables or carrying large batteries greatly restricts the use and development of electronic products, so such requirement makes the wireless power transmission has become a hot research in recent years. According to the transferring distance wireless power transmission (WPT) can be classified into three categories: non-contact power transmission, power transmission in long-distance and power transmission in middle-distance. Long-distance power transmission is primarily achieved by laser or microwave, and distance can reach tens of thousands of kilometers and even farther; non-contact power transmission can reach tens of centimeters without the cable. This paper studies the strong resonant medium-range wireless power transfer which can reach a few meters distance.Such system mainly contains power converters and high-frequency wireless power transferring, and mainly involving power electronics, electromagnetic theory and control theory. The strong resonant wireless power transmission is studied from the following aspects.1. Power factor correction As for passive power factor corrector,Valley-fill circuit is a typical passive power corrector, and the classic valley-fill circuit has been analyzed in detail in the paper, and an enhanced valley-fill power factor correction circuit is proposed which improves the power factor furtherly with less harmonics. This paper has proposed an isolated and bridgeless active power factor corrector based on SEPIC topology, and electrical characteristics of the circuit has been analyzed and simulated, and such circuit further improve the efficiency with a high power factor, less harmonic and high security.2. High-frequency inverter, the inverter fed by voltage souece will engender large transient current because of the electrode capacitance, and such current can cause greate interference and mislead the other MOSFET to conduct. Acording to features of current-fed and voltage-fed inverter, a combined current and voltage feed circuit has been proposed, so that driving performance to power switch has been improved with less disturbance to other power switch, less electromagnetic interference and enhanced system security and stability.3. High-frequency driver, high-frequency driver is the key to the switching power converter, and it can impact directly on the stability and security of the system. In this paper, based on the traditional bootstrap drive cicuit a novel bootstrap drive circuit has been proposed, which maintains the simplicity of the bootstrap circuit, but it also can shutdown MOSFET/IGBT with negative voltage, and so the system has better reliability.4. Feeding and pick-up of power in the RWPT system, this paper has proposed an indirect power feeding circuit with the combinations of serial-parallel resonance to achieve a soft-switching in the half-bridge circuit, and to feed power to parallel resonance indirectly with a constant current source, and such scheme keep the parallel resonance away from interference of switching devices, while the serial resonance compensates reactive power of the parallel resonance. This paper presents a pick-up circuit with serial-parallel resonant circuit, such crcuit has a better characteristics with a wide range of load, and avoids impacting on the impedance of the primary resonant circuit.5. RWPT topology analysis, based on analysis of the transformer principle, this paper presents further analysis of the leakage inductance. According to serial or parallel resonant compensation is applied in the primary and secondary side a variety of topologies are derived. This paper analyzed the voltage, current and power characteristics of various topologies, and wherein the frequency splitting of the two topologies are analyzed.6. Analysis and optimization of the RWPT system fed indirectly by switching power, based on scheme of RWPT proposed by MIT Institute research team, the electrical characteristics of RWPT system were studied further. This paper summed up some electrical characteristics of a multi-stage series resonance, and further analysis has been carried out on the coil inductance, capacitance values and the number of turns to make greater transmission power and transmission efficiency.