The application of the multi-coil or coil array, which enhances the freedom of power transfer, is an important topic in Megahertz Wireless Power Transfer (MHz WPT). The most typical and straightforward approach for driving multiple coils is to use the same number of power amplifiers (PAs), with each coil driven by a separate PA. A more efficient and simplified solution is to use a single PA to drive multiple coils or a coil array simultaneously, which significantly reduces the number of required PAs, thereby simplifying the overall system complexity and lowering costs. This work provides a method that uses a Class D PA and a Zero Voltage Switching (ZVS) tank, together with properly designed impedance matching networks, to realize the driving of multiple coils using a single PA. The soft switching, the gain design, and the influence of the mutual inductance between coils are all taken into consideration. A 6.78 MHz WPT system with a GaN-based Class D PA driving two coils arranged in a Double-D-like structure is implemented. The system supports arbitrary placement, number, and the power level of the receiving sides. The peak efficiency of 88.7% is achieved with a total output power of approximately 200W. The experimental results validate the proposed multi-coil driving method and demonstrate its potential for multi-coil MHz WPT applications.

Rapidly developing household energy storage systems raise the demand for corresponding DC-DC converters. Although topologies like LLC have already achieved good performance in these large-power and wide-voltage-range applications, they still have shortcomings in dealing with low-voltage battery cells. When converting from low voltage to high voltage, conventional methods can hardly control output current well when the normalized voltage gain is greater than one. Moreover, they cannot ensure a constantly small turn-off current on the low-voltage side over various working conditions, which affects efficiency and stability. To overcome these drawbacks, the paper proposes a hybrid strategy combining frequency and phase modulation for LC resonant converters. First, the theoretical model of the proposed method is constructed and analyzed. Second, a circuit is built and the proposed method is implemented, which is subsequently tested at different working conditions. As the experimental result, the actual output current is close to the expectation and the turn-off current is nearly a small constant at all the working conditions. Hence, the proposed modulation strategy is verified to solve those drawbacks. Furthermore, based on this method, close-loop output current and voltage controller will also be easier to design.

The continuous-control-set model predictive control (CCS-MPC) has been proven as a suitable multi-input multi-output (MIMO) control method for the Multi-Active-Bridge (MAB) converter. It can improve the dynamic response, minimize the cross-coupling effect inherently, and simplify the controller design. However, the constraints on the phase shift angle of the MAB converter are inevitable and have not been addressed in the existing CCS-MPC scheme. To overcome this issue, this paper proposed a CCS-MPC method for MAB converter that considers the phase shift constraints. The optimization problem is formulated based on the predictive model and then converted to a standard quadratic programming (QP) problem with phase shift constraints. The optimization package OSQP is employed for solving the constrained QP problem. The effectiveness of the proposed control method is validated through simulation and experiment.

Traditionally, the theoretical model of a coil is considered to be an ideal inductance in series with a resistor. The ability of a coil in a wireless power transfer (WPT) system to transfer power wirelessly is assessed by the Q value, which is the ratio between the imaginary part and the real part of the input impedance, describing the relationship between the amount of power transferred and the power loss. However, as the working frequency increases, the traditional model does not seem to fit the impedance characteristic well. In this work, the theory of one-port black-box circuit and the traditional coil model are firstly discussed and then a novel model based on the equivalent parasitic capacitor of the port is proposed to describe the behaviors of a coil. Based on the new model introduced, two new parameters are defined to suggest the power transfer ability. Two experiments are conducted. One of the experiments investigates the electric characteristic of the coil and another one understands its magnetic characteristic. Both experiments suggest the reasonability of the new model.

Multi-Active-Bridge (MAB) converter has complex power flow control requirements, which can be tackled by the continuous-control-set model predictive control (CCS-MPC) method. This controller has a simple and extensible design procedure, exhibiting excellent dynamic performance and in-tuitive parameters, without requiring decoupling consideration. However, the inevitable digital delay can reduce the phase margin and negatively impact its dynamic performance. To overcome this issue, this paper introduces a delay compensation mechanism that alters the execution sequence of control actions. The modified system model, predictive law, and control law under this mechanism are derived. The effectiveness of this method is validated by simulation. The influence of weighting factors is also analyzed to present a controller design guidance.

As the renewable power sources increase their penetration in power systems, the proper schedule and control for battery storage systems have become an urgent problem. In this paper, we proposed a new system framework for multi-port energy router-based battery pack active balance system. Three ports of the energy router are serially connected so that the power can flow among each battery pack to balance state of charge. Besides, the power level of the system is expanded due to this topology. A hierarchical power schedule strategy is proposed to form a comprehensive energy management in schedule layer, control layer, and driver layer. Simulation results show the effectiveness of the proposed framework and control strategy.

With the development of technology in modern society, more and more electrical and electronic instruments has been invented and used in factories and our daily life. Power supply is the basic and important need of any electrical and electronic appliance, but energy storage technologies for mobile use is far from satisfactory. For instance, one of the most important performance of Electric Vehicle(EV) is the range ability. Because of the constraints of battery capacity and charging consumes a long period of time, range anxiety is the fatal shortcoming of EV.Wireless power transfer(WPT) technology could alleviate the shortcoming of range anxiety to a large extent. With the WPT system’ spread, the charging process could be happening wherever and whenever the EV is parked.In the research area of WPT system, circuits design, coil design, compensation topology and control methods are the four most important parts. Improving the power transfer capacity(including power capacity and the range of transfer distance), system’s reliability and efficiency of the system are the main purposes of this research. By applying medium-frequency and optimized coil design as well as specially designed control strategy, a medium-frequency high-power WPT system is realized.

Multi-port AC-coupled converter (MAC) is promising to become the next-generation energy router in future Micro-grid and energy Internet to satisfy the upcoming requirement. As the most critical component of MAC, the multi-winding transformer needs a suitable model to achieve power flow analysis and flexible control. This paper analyzes the multi-winding transformer model suitable for MAC application. Three existing transformer modeling methods have been investigated, i.e. self-/mutual-inductance matrix, extended T model, and extended cantilever model. Their equivalent conversions to the expected model have been derived. A four-port multi-winding transformer is designed for the Multi-Active-Bridge converter. The experiment and simulations are performed to compare the advantages and disadvantages of three transformer models.

There are 2 wireless power standards for the mobile device market: Qi standard and AirFuel standard with frequencies of hundreds of kHz and 6.78 MHz. This paper presents a dual-band wireless transmitter operating at both 200 kHz and 6.78 MHz. A dual-band reconfigurable PA with Class E and half-bridge modes is introduced to decrease the size of transmitter. Meanwhile, the eddy current loss model of parallel connected dual-band coils is established to provide guidance for coil design. Finally, a dual-band charging pad with specially designed "decoupling ring" is proposed, which can effectively reduce the extra loss of dual-band operation.

Wireless power transfer (WPT) operating at megahertz (MHz) frequency, i.e., MHz WPT, is favorable for its compact and light circuit component and higher special freedom (longer transfer distance). This paper proposes a Class E active rectifier for MHz WPT applications. The active rectifier is consist of a ac inductor (the receiving coil), a resonant capacitor, an active switch (MOSFET) and a filter capacitor. The duty cycle of the switch can be controlled to achieve output voltage regulation. Voltage and current waveforms of the active rectifier as well as the relationship between output voltage and switch duty cycle are derived. Proposed derivation and analysis are well verified in the simulation platform and real experiments. The proposed active rectifier is favorable for its concise circuit topology and can be widely used in the consumer electronic devices applications.

Compact, isolated DC-DC converters are required in many applications such as communication terminals. This paper presents a compact, planar Class E2 DC-DC converter via wireless inductive coupling. For high frequency converters working at megahertz (MHz), it is challenging to design the system parameters under the condition of different final loads and voltage ratios. In this paper, a design method is proposed to adjust the voltage ratio of a Class E2 DC-DC converter without changing the turn ratio of the coils. An experimental 6.78 MHz Class E2 converter system with flexible voltage ratio is built, with the coupling coefficient k=0.33 and overall efficiency above 80 %.

In this paper, we propose a straightforward method to select the parameters of the PI controllers in Field Oriented Control (FOC) scheme for Permanent Magnet Synchronous Motor (PMSM) based on geometric model reduction and structured H∞-synthesis. The main contribution of this paper is that, by recognizing the essential linear system structure of PMSM model and using mature robust control method, the six parameters for PI controllers in FOC can be computed offline without resorting to trial and error online manual tuning. In addition, we also simulate the rotor speed tracking example to demonstrate the validity of the proposed parameter selection method.

In this paper we design a linear time-invariant (LTI) two-input-two-output (TITO) controller for the Permanent Magnet Synchronous Motor (PMSM). First the nonlinear system of a PMSM is approximated using a linear system with structured uncertainties according to the PMSM geometric structures. We then design a linear controller for the approximated linear system using a standard μ-synthesis robust control method. The main contribution of this paper is that a unified LTI controller is designed for the nonlinear PMSM plant using mature modern control theory, without referring to classical PID control. Thus largely reducing the design effort. The newly designed robust controller is not only easy to calculate, it is also easy to implement and requires less sensors. By virtue of modern robust control theory, it responds fast to exogenous inputs, and robust against parameter uncertainties as well.

High frequency wireless power transfer (WPT) such as working at megahertz (MHz) is widely considered to be a promising candidate for charging the lithium-ion batteries of mobile electronic devices. However, in a real battery charging application, the varying battery voltage and charging current will significantly affect the system efficiency and lead to the high power loss in the whole charging process, especially at MHz due to the obvious rectifier input reactance. Moreover, it makes the optimization design of wireless battery charging system more complicated and difficult. In this case, a 6.78-MHz wireless battery charging system is proposed and an optimization design procedure is developed to minimize the average power loss in the whole charging process. By using the circuit model of the wireless battery charging system, the system efficiency is derived and services as the basis for the optimization design. Finally, the experimental results are provided for verification. It shows that the system using the proposed optimization design can achieve a 24.5% reduction of the average power loss compared to the conventional one.

A wireless power transfer system can increase its system frequency to several Megahertz for large spatial freedom. A MHz system usually uses the same compensation as those kHz systems. Traditionally, the rectifier is modeled as a pure resistive load for the coupling coils when designing the compensation capacitors. However, the rectifier input reactance cannot be ignored for MHz systems. This reactance can affect the system resonance and is usually not considered when designing the compensation capacitors. This paper analyzes the rectifier input impedance and discusses its undesirable effects. A non-zero phase is shown to exist seeing into the coupling coils for MHz WPT system. In order to limit the phase, the optimal compensation capacitors are discussed and found. Finally, a 6.78 MHz system is used to verify the proposed optimal compensation method. It shows the phase variation can be limited from the original range [15°-35°] to the optimal range [-5°-5°].