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Fast and safe start-up is crucial for the dual-active-bridge (DAB) converters. Conventional closed-loop start-up controls fail to achieve theoretical maximum power output due to manually predefined phase-shift modes, limiting start-up speed and safe operational range. To address these issues, this letter proposes a novel variable frequency plus extended phase-shift (EPS) control. This approach enables ultrafast and wide-safe-range start-up of DAB converters by maximizing power-per-current-stress capability within safety limitations. In addition, sole EPS modulation is required in the proposed control, thus eliminating complex mode transitions and streamlining the start-up process. Experimental results indicate that the proposed control achieves a broader safe start-up range and improves start-up speed by up to 43% under voltage-match condition compared to the state-of-the-art methods.

Dual active bridge converters are extensively adopted in more electric aircrafts, wherein maintaining a sufficient hold-up time is crucial for air safety. As the current stress in conventional phase-shift controls couples with voltage gain, high-degree voltage gain occurred in the hold-up process would lead to terrible current stress higher than safe limit, which not only heightens the risk of device failure but also shortens the hold-up time due to the potential execution of protective measures. To address such issues, this letter proposes a novel hybrid phase-frequency (HPF) control method, particularly suitable for operations under low input voltage with high inductor currents. The HPF control facilitates the decoupling of the current stress from operation gain, offering advantages such as further optimized and fully regulated current stress, an extended hold-up time and enhanced operational safety. Experimental results show that current stress at full-load can be reduced 56% with HPF control, thereby extending hold-up time by 3 times. Additionally, the reduced current stress under certain power ranges contributes to improved steady-state efficiency

Quadruped locomotion is challenging for many learning-based algorithms. This is because it requires tedious manual tuning to cope with different types of terrains and is difficult to deploy in reality due to the sim-to-real gap between the training and the testing scenarios. This paper proposes a quadruped robot learning system for agile locomotion which does not require any pre-training and works well in various terrains. We introduce a hierarchical framework that uses reinforcement learning as the high-level policy to adjust the low-level trajectory generator for a better adaptability to various terrains. We compact the observation and the action spaces of reinforcement learning to deploy the proposed framework on a host computer interfaced with the robot. Besides, we design an omnidirectional trajectory generator guided by robot posture, which generates omnidirectional foot trajectories to interact with the environment. Experimental results and the supplementary video demonstrate that our hierarchical framework only trained in simulation can be easily deployed in the real world, and also has the advantages of fast convergence and good terrain adaptability. Note to Practitioners—This paper presents a hierarchical framework for quadruped robots. It combines a high-level reinforcement learning controller with a posture-guided trajectory generator to adaptively generate omnidirectional motions. Our method is easy to train as it converges fast and does not need to adjust a dozen or so of rewards. The quadruped robot can be deployed in a real environment directly after being trained in simulation. With the trained hierarchical framework deployed on a remote host computer, the robot works well in a variety of real-world environments unseen in the simulation.

The decoupled-type triple active bridge converter (DTAB) offers improved power density and power-decoupling features by removing an auxiliary inductance from one port. However, traditional phase-shift modulation schemes fail to extend the zero-voltage-switching (ZVS) range, limiting efficiency and practical application. To broaden the ZVS range of DTAB converters, in this paper, a streamlined quadruple phase-shift (QPS) modulation scheme, evolved form the volt–sec-balance principle in dual active bridge (DAB) converters, is proposed to achieve ZVS operation in the two ports maintained with the auxiliary inductance. To avoid increasing computational burden, the influence of magnetizing inductance is considered for the ZVS operation in the inductance-canceled port, whose optimal design is analyzed, particularly suitable for DTAB converters. Consequently, this software–hardware-integrated strategy offers computational efficiency, particularly advantageous for time-intensive scenarios such as electric vehicle (EV) charging system. Additionally, to simplify the ZVS analysis, a unified ZVS model of DTAB converters based on the complete circuit response equation is introduced, obviating the need for complex mode-dependent ZVS analysis and also applicable to TAB converters. Finally, the efficacy of the proposed strategy is validated in a 3.3 kW/100 kHz SiC-based DTAB prototype, tailored to the EV a plications, achieving peak efficiency of 95% at partial load conditions.