Track wireless power transfer (WPT) systems are increasingly used for monorail robots, industrial transportation, etc. Conventionally, the track WPT system's primary power supply is designed to be equal or higher than the total running pickups' rated power. However, in practice, some of the pickups may transiently require more power than their normal operating state. It is not cost effective to increase the power rating of the primary source for the transient case. Hence, this article proposes a method to strengthen the track's power transfer capability by reversely injecting energy from available online pickups to the transiently over-rated one. A bioperation mode is proposed, which includes both the normal operation and the strengthening operation. A bidirectional pickup topology is used, and the equivalent circuit is analyzed accounting the bioperation mode. In addition, a synchronization method of the primary and reverse injection pickups is proposed. A criterion to determine the boundary of the reverse energy injection is also presented. By detecting the peak current, this energy injection method can be practically implemented and the proposed method is verified through the experimental results.

The significant benefits of brushless doubly fed induction generators (BDFIGs) are higher reliability and lower maintenance cost due to the lack of a brush gear. Recent studies on BDFIGs have shown promising applications in wind power generation. The low-voltage ride-through (LVRT) capability of wind turbines is one of the most important properties specified in the grid codes of many countries. A crowbarless LVRT control strategy based on flux linkage tracking for a BDFIG under symmetrical voltage dips is proposed in this paper. A novel and simple controller in static reference frame is presented to implement flux linkage tracking. To both suppress the control winding (CW) current and increase power winding (PW) reactive current, a time-sharing control and CW current-first control solution is proposed. In the most severe case, where the BDFIG rotor speed is 100% of the maximum rotor speed and under 100% symmetrical voltage dips, the experimental results show that the CW current peak can be limited to 2.01 p.u. of the CW current rating and the torque ripple is small during the fault. The experimental results also show the possibility of the BDFIG to ride through the severest voltage dips without extra hardware, such as a crowbar.

For the application of wireless power transfer (WPT) technology in robot arm, it is necessary to provide flexible power supply for each arm device across multiple arm joints. However, rotation of the joints and the variation of the loads will lead to the fluctuation of the output voltage at each stage. To guarantee stable output voltage, a bi-directional multi-stage wireless power transfer (BM-WPT) method is proposed to provide energy for multiple loads. A bowl-coupling structure and three-dimensional orthogonal ring coil arrangement are proposed to reduce coupling variation against joint rotation. With a special resonant topology design for each stage, energy can be injected or output freely on each stage regardless of energy transfer direction. This topology can also reduce the sensitivity of the output voltages with the variation of the loads. The simulation and experimental results have verified the effectiveness of the proposed method and the coupling mechanism.

Wireless power transfer network (WPTN) is composed of nodes and power transfer routes, which can supply power for group devices. In the WPTN, it is difficult to build a definite power transfer route under the random node distribution condition. In this article, a dynamical construction and optimization strategy of power transfer route is proposed to adapt to random node distribution. In order to establish a definite route among grouping nodes, each node is designed to switch its role flexibly through a topology switching method. Furthermore, in the switching process of power transfer route, the switching method of node role shows that the transition is smooth. Then, an actual WPTN with five randomly distributed nodes verifies the effectiveness of the proposed method.

The autonomous wireless power transfer (WPT) system with series–series compensation has the advantage of the output power being approximately independent of variations in the coupling coefficient and load within the bifurcation region. However, the system encounters the issue of nonuniqueness in steady-state oscillation frequency, influenced by factors, such as varying system parameters, unpredictable external disturbances, and initial conditions. To overcome this issue, this letter proposes a relay-switching technique for manipulating the oscillation frequencies of autonomous WPT systems. This technique utilizes an adjustable relay threshold to dynamically modify the phase relationship between the input voltage and current, guiding the system to operate at the desired oscillation frequency. Complementary to the relay-switching technique, a gain-shaping strategy is presented to enhance the current gain at the target frequency, thereby increasing the possibility of convergence to that frequency. Finally, an experimental setup is built to verify the effectiveness of the proposed method. A video demonstrating the switching of different steady-state oscillation frequencies is attached to this letter.