In order to allow a wireless power transfer system to operate in a large-scale space where coupling coefficient has a significant variation due to different air gaps and displacements, a double-side self-tuning LCC /S system using a variable switched capacitor based on parameter recognition is proposed in this article. The main innovation is that the parameter recognition method is able to recognize both mutual inductance and double-side self-inductance with only rms value of sampling signal, phase information and auxiliary circuit being needless. Besides, based on the result of parameter recognition, the double-side use of variable switched capacitors and corresponding control strategy allow the proposed system to operate in a large-scale coupling space and help to improve system efficiency. Experiment results show parameters recognizing error less than 5%. A contrastive simulation verifies that variable switched capacitor can be equivalent to discrete capacitor with the same branch current in the proposed system. System feasibility is testified by a 700-W prototype and the effectiveness of the proposed system is demonstrated by a contrastive experiment with and without pulsewidth modulation (PWM) tuning, efficiency from dc to dc will increase about 3% with PWM tuning.

In the application of wireless power transfer system, parameter drift of resonant tank is a general situation which induces natural frequency of primary side or secondary side deviates from switching frequency. This frequency deviation phenomenon will deteriorate load-independent constant current characteristics and decrease output power capacity for an S/S compensation system. This article illustrates the problems caused by frequency deviation through output characteristic analysis and addresses them by a self-tuning method based on switched capacitors (SCs). The proposed self-tuning method requires no resonant parameters such as compensation capacitance and coil self-inductance in advance. Primary and secondary natural frequencies can be both tuned to switching frequency continuously by SCs. The proposed method is verified by a simulation and a 500 W S/S compensation experimental prototype. After completion of self-tuning process, load-independent constant current characteristic is recovered and the output power capacity is boosted, which are in consistent with the theoretical analysis of system output characteristics. The proposed method is also applicable to LCC /S and LCC / LCC topologies.

Discrete silicon carbide (SiC) MOSFETs are usually connected in parallel to increase their current carrying capacity. However, unequal switching losses and unequal transient current overshoot can limit the maximum switching frequency and maximum current carrying capacity of the paralleled unit. In this paper, a paralleled half-bridge unit is proposed to improve transient current sharing performance, which is characterized by a distributed arrangement of dc capacitors. Firstly, the main causes of transient current imbalance in traditional power layout are analyzed theoretically for the first time. Then, the traditional power layout is optimized by the AnsysEM co-simulation techniques to improve transient current sharing performance. The layout of gate driver is also optimized to reduce the transmission delay of gate drive signal. The double pulse tests are carried out to verify the current sharing performance under normal and short circuit operating conditions. Compared with traditional power layout, the difference in transient current overshoot of the low-side paralleled SiC MOSFETs is decreased significantly from 10.22% to 2.78% and the difference in switching losses is also reduced. A boost converter is constructed based on the paralleled half-bridge unit. A more uniform temperature distribution indicates the improved current sharing performance by optimizing the power layout.

This article presents a new configuration of onboard integrated battery charger for electric vehicles (EVs) using six-phase machine and three-phase ac source. The configuration proposes the utilization of symmetrical six-phase open-end winding machine, twelve-leg inverter, and a dc-dc converter. The charger circuit is constructed by connecting directly the three-phase grid to the middle point of machine's phase winding, where the grid currents split into equal portions and flow in opposite directions, without adding an extra mechanical switch (or relay). From this concept, the proposed system has the advantages of obtaining high-power density with a large value of inductance for grid-side filter during charging and avoiding an electromagnetic torque as well as providing a high fault tolerant capability. Moreover, through proper control strategy, the proposed system is able to operate under unity power factor (UPF) with total harmonic distortion (THD) below 5%. In this article, the possibility of vehicle-to-grid (V2G) mode is also investigated. Detail of the control strategy for charging and V2G are given. Furthermore, simulation and experimental results are provided to validate the theoretical analysis.

The integration of nine-phase permanent magnet synchronous machines (9-PMSMs), employed in on-board integrated battery charger for electric vehicles (EVs), into three-phase grid generates an inevitable torque fluctuation in charging and vehicles-to-grid (V2G) modes. This undesirable torque which is source of motor vibration and noise, is due to the interaction between zero-sequence current, triplen harmonics (3rd and 9th) of induced back EMF and rotor position. This paper considers a new solution for nine-winding integrated battery chargers of EVs. A segmented three-phase PMSM with nine windings (S3-PMSM-9W) is used to replace the 9-PMSMs. With this configuration, the system has the advantage of torque-free in charging/V2G mode, low core loss, and simple control (based on three-phase control) in both traction and charging/V2G modes, with the privilege of employing reduced number of sensor and with no additional new elements. Through proper three-phase control strategy, the system operates under unity power factor (UPF) with total harmonic distortion (THD) below 5 %. Control strategies for charging, V2G and motoring are given, moreover simulation and experimental results are provided to validate the theoretical analysis.

This paper proposed a fast and robust control strategy for a wireless power transfer system using primary side control. First, a sinusoidal reference trajectory signal was generated by analyzing the properties of the vector fields associated with all possible configurations of the primary power converter. Then, a switching controller was designed based on the switching behavior of the converter and the trajectory reference signal for the switched differential equations, capturing the dynamics of the primary side converter. Finally, a set of points around the reference trajectory was defined to establish the global asymptotic stability. The proposed control strategy has higher dynamic responding speed to large variations and perturbations of the load in comparison to other suggested controllers. The simulation and experimental results show that the primary current overshoot was efficiently suppressed, and the system response performance was improved.