For evaluating and optimizing the efficiency of power converters, the loss model of the power semiconductor devices is needed. The analytical loss model is favorable for its simplicity. However, the model accuracy needs to be improved. This paper proposes an analytical loss model for the commutation pair of silicon carbide (SiC) MOSFETs and SiC Schottky barrier diodes. Compared to the conventional loss calculation method, the proposed model is derived based on the conservation of energy, which considers the impact of the displacement currents on estimating the turn-on and turn-off losses. The modeling and extraction methodology of the model parameters are given, and the impact of operational conditions on the model parameters is studied. Using the proposed model, the losses can be calculated analytically and also the switching trajectories can be predicted with good consistency. A double pulse tester is built to verify the proposed model. The results show that an average modeling error is reduced from 20% using the conventional piecewise linear model, to around 10% using the proposed model under various operational conditions, and the time cost is at least 3000 times smaller compared to the existing SiC MOSFETs models.

A comprehensive time-domain model of CLLC class isolated bidirectional DC-DC converter (IBDC) is proposed in this article. Based on the circuit analysis and the solution of the state equations, analytical expressions of the state variables are provided. The model is a piecewise time-domain analytical model and can accurately describe the transformer currents and capacitor voltages under almost all basic types of control strategies, e.g. phase-shift control and frequency modulation control. With the model, the steady-state analysis of IBDC can speed up evidently (up to 330 times faster compared to MATLAB/Simulink and more than 10 times compared to SIMPLIS and PLECS), which gives great support to parameter sweep and case comparison in design procedure. By assigning specific parameters, the presented model can also be applied to the analysis of LLC resonant IBDC or typical DAB IBDC since LLC converter and DAB converter are similar to CLLC converter in circuit topology. The transformation of the model from CLLC to LLC/DAB is provided and several application examples are given. Finally, the simulation and experimental results are presented, verifying the effectiveness of the model.

For the bidirectional wireless power transfer (BWPT) technology, the phase synchronization between the transmitting and receiving converters is very essential and difficult to achieve by wireless communication between two sides because the delay and data transfer interval of wireless communication severely influence the control performance. This paper proposes a novel control strategy for BWPT, which can achieve the phase synchronization and maximum efficiency point tracking (MEPT) independent of the real-time wireless communication. To solve the overshoot and oscillation problem incurred by the proposed control strategy and the nature of the system itself, the dynamics of a series-series (SS) compensated BWPT system is then analyzed and a small-signal model of this system is derived based on the generalized state space averaging (GSSA) and extended describing function (EDF) methods. Using the small-signal model, a BWPT control system based on the proposed control strategy is designed and optimized. The validity of the proposed strategy and the performance of the control system are verified experimentally using a 3.3-kW prototype system.

This letter proposes a deadbeat current controller for isolated bidirectional dual-active-bridge dc-dc converter (IBDC). The controller uses an enhanced single phase shift (ESPS) modulation method by exploiting pulse width as an extra control variable besides phase shift ratio the only control variable of the conventional single phase shift (CSPS) modulation. The current reference can be tracked within one switching cycle during the bidirectional power transmission and transition of the two directions. Deadtime effect is studied and the compensation method for the controller is presented. Parameter robustness is analyzed by mathematical derivation and the online auto-tuning method for the inductance is presented. The proposed deadbeat current controller is simple and easy for implementation. Moreover, it shows superior dynamic performance, which is verified by experimental results during the transient processes of the converter. The effectiveness of the auto-tuning method is also validated by the prototype experiment.

Taking switching transients of switching devices into consideration in design and simulation of power electronic systems has long been a huge obstacle. Sufficient accuracy has to be ensured, meanwhile more significantly the transient model has to be practical, i.e. providing a convergent result with an acceptable solving speed and a convenient parameter extraction technique. Aiming at both targets, this paper proposes a piecewise analytical transient (PAT) model for switching device commutation unit, taking an IGBT-PiN diode pair as an example. A piecewise time-varying voltage source-current source pair is utilized to model the IGBT-PiN diode pair. With sufficient accuracy, PAT modeling methodology noticeably increases the solving speed and improves the convergence of converter simulations. Model expressions and datasheet-driven parameter extractions are illustrated in detail. Experimental and simulated results are presented and compared to validate both the accuracy and the practicability of the proposed PAT model, expected to be employed in transient simulations of power electronic systems.

To gain accurate control of the whole switching transients, this paper proposes a self-regulating voltage-source gate drive (SRVSD) method for high-power IGBTs working under hard switching conditions. The SRVSD has a high-speed circuit capable of adjusting drive levels. With high-speed feedbacks, the on-board FPGA identifies each switching stage and accordingly varies drive voltages. In this way, switching delay, diC /dt and dvCE/dt are regulated individually. The SRVSD allows accelerated delays and dvCE/dt stages without increasing diC/dt. Based on their principles, SRVSD is compared with existing active drivers comprehensively to verify its delay and loss reductions performance. By experiments, compared to conventional gate drive (CGD), SRVSD achieves at most 80%, 72% reductions in turn-on, -off delays, and 58%, 31% reductions in turn-on, -off losses at identical current/voltage overshoots. Moreover, the proposed adaptive control concept is verified in this paper. Within several cycles, this concept automatically regulates durations of all delay, diC/dt and dvCE/dt stages to reach individual target values, largely independent of switching conditions. A practical piecewise linear switching-based loss model is proposed. Combined with SRVSD, this practical loss model can offer convenient sensing and control of switching losses in an accurate and online manner.