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LCC resonant converters have been widely adopted to achieve high power density and high efficiency. Due to high switching frequency and large reactive power in the resonant tank, the efficiency of LCC converters at light load decreases dramatically. Burst mode, which is commonly used in dc–dc converters to improve efficiency at light load, has not been applied to LCC resonant converters due to the oscillation of resonant tank during the burst off -time of burst mode. In this article, a simplified state model, which has only two state variables that can easily describe its state trajectory in the state plane, is proposed for LCC resonant converters with a capacitive output filter. Then, optimal state trajectory control of LCC converters for burst mode is proposed based on the state model, which can eliminate the resonance during the burst off -time. In addition, the transition from start-up mode to burst mode is proposed based on state trajectory control, which can complete this transition in one switching cycle. Finally, the proposed optimal trajectory control in burst mode is verified by an LCC converter prototype.

LCC resonant converters have been widely adopted in pulse-modulated high-voltage generators to achieve high power density and high efficiency, which require a short rising time of output voltage. However, if the LCC resonant converter starts up too fast, the voltage and/or current stresses of the resonant tank during startup may be several times higher than those of the steady state due to the complex dynamic behavior of the resonant tank. In this article, a simplified state model of LCC resonant converters is first introduced. Then, optimal state trajectory control (OTC) is proposed to optimize the startup performance of LCC converters. Besides, to combine the advantages of OTC in the startup and power integrity (PI) control in the steady state, hybrid control is adopted. Finally, an LCC resonant converter prototype is constructed to verify the proposed OTC, which achieves a minimal rising time of output voltage with no additional current and/or voltage stresses in the resonant tank during startup compared to the conventional control.

There are two significant problems for the virtual synchronous generator (VSG) under the nonideal grid, including power coupling and current distortion. Although the virtual impedance (VI) is often used to decouple the control of active power and reactive power, it can neither suppress current harmonics nor solve current imbalance caused by the nonideal grid. Therefore, this paper proposes the configurable virtual impedance (CVI) approach to improve both the power coupling and the output current quality. The proposed methodology could aid the independent design of the virtual sequence impedance (VSI) for any harmonics, of which the virtual fundamental positive sequence impedance can be used to realize power decoupling, and the other VSI is designed to mitigate current aberration. Due to the requirements of VSI, the novel harmonic extraction algorithm (NHEA) based on the state space model is presented to separate the positive-sequence component (PSC), negative-sequence component (NSC), and zero-sequence component (ZSC) in the fundamental and harmonic current. Then, under this harmonic extractor, 90° phase lead for each SC can be easily achieved by means of simple vector rotation. Excellent extraction performance of the NHEA and remarkable ability of current quality control and power decoupling regarding CVI are demonstrated by simulations and experiments.

Gallium nitride high electron mobility transistor has been seen as a power semiconductor devices with lots of potential since it has been commercialized. However, the advantages of fast switching speed with low conduction resistance always have to compromise to the fast switching on evoked overvoltage. Though it has been realized that the overvoltage problem arises from the joint effect of fast switch speed and parasitics, there is a lack of ways for quantitative analysis. This paper proposes a reliable circuit model based on a quantitative way to analyze the cause of overvoltage and finds optimized parameters to suppress. A normalized method is adopted to make the analysis more general, and the voltage and current stress determined safe operation area during the switching on process under the constraint of maximum overvoltage is detailed. The analysis is verified by a double pulse test experiment, with the calculated and measured maximum overvoltage matching very well. The analysis can help us to choose reasonable turn- on speed and power loop parasitic inductance before the printed circuit board (PCB) manufacture with an acceptable maximum overvoltage guaranteed.

One-cycle control power-factor correction (OCC-PFC) with vector operation is a promising rectification method that eliminates harmonics and improves the power factor. It features great simplicity, high performance, and excellent stability. This paper performs analysis and design of OCC-PFC in both the steady-state and dynamic transients. The sufficient stability condition for three-phase OCC-PFC is derived. Some typical large-signal perturbations in practice are then used to verify the theoretical predictions. The paper also provides some guidelines for the selection of the circuit parameters in practical application. All analysis results were verified by simulation or experiments based on a three-phase 1-kW pre-industrial OCC-PFC prototype.