A wireless power transmission (WPT) requires high switching frequency to achieve energy transmission; however, existing switching devices cannot satisfy the requirements of high-frequency switching, and the efficiency of current WPT is too low. Compared with the traditional power inductors and capacitors, fractional-order elements (FOEs) in WPT can realize necessary functions though requiring a lower switching frequency, which leads to a more favorable high-frequency switching performance with a higher efficiency. In this study, a generalized fractional-order WPT (FO-WPT) is established, followed by a comprehensive analysis on its WPT performance and power efficiency. Through extensive simulations of typical FO wireless power domino-resonators (FO-WPDRS), the functionality of the proposed FO-WPT for medium and long-range WPT is demonstrated. The numerical results show that the proposed FOE-based WPT solution has a higher power efficiency and lower switching frequency than conventional methods.
The slow balancing speed of switched-capacitor (SC)-based equalizers makes this structure difficult to apply in series-connected battery strings. In order to reduce the number of energy conversion processes and achieve leapfrog transmission of energy, a hybrid-structured voltage equalizer (HSVE) is developed in this work for battery strings to achieve high-speed any-unit-to-any-unit (AU2AU) equalization, in which each unit can also achieve internal balance in any arbitrary imbalance status. Compared to the conventional equalizers using complex monitoring and control strategy, the proposed equalizer does not need any cell monitoring circuits-all MOSFETs are triggered by a pair of complementary pulse signals with a fixed switching frequency and constant duty ratio, and electricity can automatically and directly exchange among all battery cells. Hardware experiments on super-capacitors and Li-ion batteries are conducted in this study, which prove the feasibility of the proposed voltage equalizer. The proposed battery management strategy will have wide applications in modern battery-related industries such as electric vehicles (EVs).
The VIENNA rectifier is of high reliability, high power density, and low complexity, which has been widely applied in telecommunication systems.However, it has 25 switching states complicating the control design. Besides, it is easy for the VIENNA rectifier to distort the input currents at zero-crossing points, which will degrade the grid power quality. To address these problems, a novel mode-reduction space vector pulse width modulation (SVPWM) control method is proposed in this paper. By analyzing the switching states of the VIENNA rectifier, 3-mode, 6-mode, and 18-mode control framework are compared, and it is found that the 18-mode has advanced features. Specifically, the proposed 18-mode control algorithm will have fewer calculation steps and a simpler processing flow. More importantly, it can eliminate the input current distortions for power quality improvement. A 4 kW hardware prototype of the VIENNA rectifier is developed, and experiments have been performed to verify the harmonic reduction feature of the proposed 18-mode control.
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