Publications

The new frontier maritime magnetohydrodynamic (MHD) engine drive generates the fields of magnetic and electric to accelerate seawater inside the engine duct. The dc system is overwhelmed by the ac for no explosive and poison gases emission. The proposed power circuit applies a transformer to provide a new drive design for the ac system, by reallocating the field generation currents for propulsion. The excitation current for magnetic field generation now is higher in the primary side of transformer and thus to decrease the current flowing the liquid that drew plenty of the conduction loss in previous ac MHD drive in series-resonant design. To conduct the high-frequency ac to mitigate the gas emission and the phase difference between the fields, three resonant tanks are deployed, constructing a resonant circuit for high circuitry efficiency operation. This article starts from introducing the concept of maritime MHD engine and the research fundamental. The comparison to the conventional ac MHD engine drive stresses its advantage. A steady-state analysis elaborates that the proposed topology and design consideration highlights the optimal design to the turn ratio and engine duct design. The electrical-fluid experiment and the concept verified converter will be demonstrated with the 82% converter efficiency at 470 W, maximum 92% efficiency to back the validity.

The Magnetohydrodynamic (MHD) thruster is an electrical propulsion system that utilizes Lorentz force to convert the electric power to mechanical, accelerating the conductive fluid without the need for conventional moving propellers. However, most propulsion analyses of MHD thrusters are based on fluid dynamics, which is not of the electrical engineering discipline. This article proposes a novel modeling approach that combines Lorentz force with Stokes law in fluid mechanics to figure out the operation mechanism of the MHD thruster. The study investigates the propulsion force towards charged particles in a vacuum and conductive solutions under DC and AC, displaying the resulting moving profiles. Furthermore, this article presents a 550 mm long MHD thruster prototype design that includes the testing liquid solution, electromagnetic field generation, and the power electronic circuit for the electric thruster propulsion, to provide convincing validation of the proposed modeling.

Given the unpredictable nature of renewable energy injection, a combination of second-life batteries and three-phase electric springs (ESs) is utilized to stabilize the bus voltage from the load side. Voltage stability for critical loads is achieved through the use of a voltage feedback-based reactive power regulation strategy, which makes effective use of the limited output current provided by the second-life batteries. In addition, a consensus algorithm is introduced to facilitate information sharing among multiple ESs, thereby ensuring voltage consensus and restoration. However, the consensus controller is exposed to the risk of false data injection (FDI) attacks, which could lead to voltage fluctuations in the converters. To address this issue, a distributed high-order differentiator (DHOD) is proposed, characterized by its fast response speed and high estimation accuracy, to detect and eliminate attack signals. Through both simulation and experimental validation, it is demonstrated that the proposed strategy enhances voltage stability and energy throughput, even when subjected to FDI attacks.

This article proposes a wireless power transfer (WPT) system that can deliver power to multiple receivers with additional resonant frequencies and concurrent frequencies. It employs a multiple frequencies H-bridge inverter, which can control the frequencies and the output powers of the receivers independently. Compared with the typical multiple-frequency and multiple-receiver WPT system, the proposed WPT system can power a considerable number of receivers simultaneously or independently. Additional resonant frequencies and concurrent frequencies can be obtained by the original transmitter without any physical changes. The resonant frequencies transmission, additional resonant frequencies transmission, and concurrent frequencies transmission are investigated analytically in detail. To validate the proposed design performance, a tapped-inductor transmitter, along with three receivers designed at a frequency range from 50 to 200 kHz have been fabricated. At 30-mm separation, the system is able to deliver a maximum power of 240.8 W and a maximum efficiency of 92.36% at 50 kHz and 200 kHz, respectively.

Mutual inductance estimation (MIE) plays an essential role in the primary-side control for dynamic wireless power transfer (DWPT) systems. Traditional MIE method that is only based on primary-side transmitter (Tx) information contributes to no redundant hardware components. However, this method can cause huge calculation effort in multi-Txs DWPT systems because it involves the solution of multivariable multiple equations. In this letter, a new method for estimating mutual inductance for series–series (SS)-compensated multi-Txs DWPT systems is proposed, where dual-side communication and auxiliary position sensor are not required. By first solving the mutual inductance ratio and then calculating the exact mutual inductance, the proposed method is proven to avoid solving multiple equations, thus greatly reducing complexity of the calculation. This study also includes simulations and experiments that are carried out in a DWPT system with two Txs to one receiver (Rx).

An alternative wireless power transfer (WPT) using near-field magnetic power distribution is proposed. The new method is characterized by using a low permeability path in serial with a high permeability path as the main unit or the basic cell. The output can be tapped into the main unit by paralleling the low permeability path. The magnetic cores are integrated with different permeability to form a multiple-transmitter geometry. Every transmitter corresponds to more than one receiver that is integrated with back-end circuits such as rectifiers to convert ac voltage into dc voltage. The receiver can be easily installed in the electrical devices, and hence power is transferred wirelessly to drive the devices. Analysis of the working mechanisms of the proposed WPT system is given in detail and design considerations are also investigated. Power loss distributions for the converter and coupler are also analyzed fully. Experimental results show that a basic cell driven by an 80 kHz pulse wave, supplying three resistive loads at 321 W achieves 86.6% efficiency. The system efficiency can be maintained at a high level over a wide output power range. Finally, a magnetic panel comprising seven basic cells supplying multiple loads is demonstrated. Results show the feasibility of the proposed system by lighting up multiple LED loads.