Magnetically coupled resonant wireless power transfer (MCR-WPT) technology has received significant attention due to its ability to realize mid-range power transfer. However, the transmission characteristics of MCR-WPT systems are susceptible to variations in coupling coefficients and loads. Parity-time (PT) symmetry has been introduced into the WPT system (PT-WPT) to achieve constant power and high-efficiency transmission over medium distances. This paper provides a comprehensive review of the PT-WPT technology.

First, the paper introduces the PT-WPT system’s basic structure and operating mechanism. It analyzes how the system balances energy gain and loss through the nonlinear saturated negative resistor, allowing it to maintain stable power transmission under varying coupling conditions. Coupled-mode and circuit models are used to construct the PT-WPT system. The two models’ similarities and differences in the energy transmission mechanism, PT symmetry conditions, and system characteristics are described. In addition, PT-WPT can be considered a novel wireless power transfer technology.

Next, the paper discusses the construction methods of nonlinear saturated negative resistors, which can be divided into two categories based on the components used: operational amplifiers and power converters. While operational amplifiers provide a simple and low-cost solution, they are limited in power output. In contrast, power converters, such as half-bridge, full-bridge, and class E inverters, enable higher power output and efficiency but require more complex control strategies. Then, the advantages and disadvantages of these methods are discussed, and directions for improving the design of negative resistors are given.

This paper introduces the different types of coupling mechanisms and the implementation of charging functions. Among the topologies of PT-WPT systems, single-transmitter-single-receiver is the most basic structure; high-order compensation networks and the introduction of relay coils are commonly used to extend the transmission distance of the PT-WPT system. Multi-transmitter/multi-receiver can also improve the system’s reliability and realize stable power transmission in multi-load systems. Furthermore, the charging control strategies are investigated to realize the constant power and constant current/voltage functions independent of the coupling coefficient and load variation, further promoting the practicalization of PT-WPT systems.

Finally, this paper summarizes the existing research on PT-WPT systems and future research issues. PT-WPT technology is expected to find broader applications in the future and promote the development of wireless charging technology.