A variable-switching constant-sampling frequency critical soft switching model predictive control (VSCS-MPC) method is proposed in this paper to improve the dynamic behavior, efficiency and power density of the DC/DC power converters. Firstly, this paper analyzes the boundary constraints of critical soft switching that are derived with the key parameters of the interlock time and threshold current for typical SiC and GaN devices. Then, the VSCS-MPC method is proposed for synchronous DC/DC converter. Both the current source load and resistive load converters are validated with the proposed MPC method. VSCS-MPC includes two controlling parts. First is the frequency controller to maintain the critical soft switching operation by adjusting the switching frequency based on the pre-defined boundary conditions with a constant sampling frequency. A discretized frequency controller is developed to improve the stability of the system by maintaining a fixed sampling frequency. Second part is the model predictive controller to track the output voltage/current and maintain critical soft switching during dynamic periods. The explicit optimization and oversampling methods are applied in the MPC controller to meet the high frequency demand. A large current ripple ( $\triangle i_L$ $\ge$ 200 %) is introduced to achieve the critical soft switching and reduce the inductance. The switching losses are decreased by the frequency controller and the critical soft switching is maintained especially in dynamic periods due to the fast response of MPC.

中文翻译：

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用于DC / DC转换器的可变开关恒定采样频率临界软开关MPC

为了提高DC / DC电源转换器的动态性能，效率和功率密度，本文提出了一种可变开关恒定采样频率临界软开关模型预测控制（VSCS-MPC）方法。首先，本文分析了临界软开关的边界约束条件，这些约束条件是根据典型SiC和GaN器件的互锁时间和阈值电流的关键参数得出的。然后，提出了用于同步DC / DC转换器的VSCS-MPC方法。电流源负载和电阻负载转换器都通过提出的MPC方法进行了验证。VSCS-MPC包括两个控制部分。首先是频率控制器，通过基于预先定义的边界条件以恒定的采样频率调整开关频率来维持关键的软开关操作。开发了离散频率控制器，以通过保持固定的采样频率来提高系统的稳定性。第二部分是模型预测控制器，用于跟踪输出电压/电流并在动态期间保持关键的软开关。MPC控制器采用显式优化和过采样方法来满足高频需求。大电流纹波（ $ \三角形i_L $ $ \ ge $引入200％的电阻以实现关键的软开关并降低电感。频率控制器可以降低开关损耗，并且由于MPC的快速响应，尤其是在动态周期中，可以维持关键的软开关。