With the continuous development of human civilization from “the age of steam”, “the age of electricity” to “the age of information" and the rapid rise of steel, machinery, energy, chemical industry and other heavy industry, the interaction of the information and resource round the world has become more convenient. Accompanied by fact that human development has entered an unprecedented period of prosperity, the consumption of global energy became so sharply, making the energy crisis and ecological crisis becomes more and more obvious. In this regard, the energy structure is moving towards a cleaner and low-carbon form. A new generation of integrated energy power systems based on the Internet concept, fused deeply with new energy power generation, flexible transmission system, high-efficiency energy storage, intelligent control, remote monitoring and diagnosis, “big data”, “cloud computing” and other advanced technologies, makes full advantage of the complementary characteristics of multiple energy systems , using hydrogen (natural gas), heat and electric vehicles (EVs) as new energy storage media, opening up energy conversion channels between electric power and natural gas networks, thermal networks and transportation networks, through energy conversion, network interconnection, information interaction and coordination control, to realize the goal of reducing fossil energy consumption, carbon emissions and improving the comprehensive utilization efficiency of energy.
Wireless power transmission (WPT) technology can make EVs getting rid of the shackles of charging cables and improving interaction flexibility with the new generation of energy systems and can supply energy for various types of sensors widely distributed in the energy system in order to reduce maintenance costs. In addition, with the further enhancement of electrification, informatization, and intellectualization in production and life, the potential of WPT technology for great applications is being gradually explored in household appliances and consumer electronics, implantable medical devices, industrial automation equipment, unmanned aerial vehicle, unmanned underwater vehicle, internet of things, wireless sensor networks and other aspects. WPT technology, regarded as one of the most important focuses in the field of electrical engineering, is assisting the development of a new round of technological revolution, changing the way human beings live and work.
With the rapid development of WPT technology, the systematic performance index of transmission power, transmission efficiency and transmission distance etc. are developed to satisfy the general application requirements. Before the large-scale application, its electromagnetic safety must meet the standard requirements, especially in high power applications such as electric vehicles, as well as in long exposure scene such as home appliance and consumer electronics. Electromagnetic environment become particularly prominent in WPT systems that rely on magnetic field coupling for energy transmission. However, the electromagnetic environmental problem of WPT technology has not been paid enough attention at home and abroad. There are still some bottlenecks in the research of WPT electromagnetic environment: no reasonable unified evaluation index, no method for safe, convenient, rapid, accurate analysis of electromagnetic exposure of human body, the lack of systematic optimization method of the electromagnetic environment.
Aiming at the main problems of electromagnetic environment research in WPT system, the paper focuses on the analysis, measurement, evaluation and optimization of electromagnetic environment of radio energy transmission systems, mainly including:
1) Study on the analysis method of human electromagnetic exposure in resonant wireless power transmission system. A precise human anatomy model based on the OPDR (On-Demand Polygon Reduction) is designed to adjust the accuracy and focus of the analysis. The WPT system and the application environment are equivalent to a two port network, using field-circuit method to operate quick analysis on electromagnetic environment of WPT system and the electromagnetic exposure of the human body.
2) Experimental study on electromagnetic environment of resonant wireless power transmission system. By building a resonant WPT electromagnetic environment test platform, the characteristics of electromagnetic environment is studied by the experimental method, the accuracy of numerical methods for analysis of electromagnetic environment of combining field and circuit is verified. For study on the electromagnetic environment, the preliminary outcomes are the characteristics of resonant wireless power transmission system, the law of human exposure and methods of electromagnetic environment optimization, providing reference for the follow-up study.
3) Study on the evaluation method of human electromagnetic exposure to resonant wireless power transmission system. By combining the characteristics of WPT technology and the coupling mechanism between system and organism selection of suitable electromagnetic field evaluation indexes, effectively field measuring positions can be selected based on the WPT system field distribution by computer analysis, the positions are usually in the strong field region and the sites where the body often stays. When the electric field exceeds the standard limit, ceaselessly revisies are performed to the model until the deviation of the results analyzed by the computer and measured are controlled in a reasonable range. Then in vivo induction field and SAR calculated by computer are used for accurate-reasonable-safe evaluation of ex vivo human exposure to WPT system (Ex Vivo Assessment Method, EVAM). In special applications, some indexes cannot reflect the real harm that the human body may suffer, and then all the indexes should be satisfied and not be surpassed.
4) Research on electromagnetic compatibility design and comprehensive assessment of resonant wireless power transmission system. The electromagnetic environment of WPT system is discussed from three aspects of electromagnetic disturbance source, coupling path and sensitive equipment. The corresponding feasible schemes for electromagnetic environment control are also studied. The electromagnetic environment regulation capability of different regulation schemes and their effects on the system performance are deeply studied. Through a case study, the scheme is evaluated by comprehensively considering the electromagnetic environment regulation ability and system characteristics.
Through the research of the paper, reasonable measurement and evaluation method of WPT electromagnetic environment is acquired, which takes a significant supporting role in supporting WPT field measurement or evaluation standard, and also has a great significance in optimizing the system of electromagnetic environment consummation. The comprehensive evaluation of the electromagnetic environment control scheme of WPT system is beneficial to the design of WPT system with high performance and high security. The research results can further promote the popularization and application of WPT technology.