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This paper proposes a non-isolated three-port converter which integrates the input port, battery port, and load port into one converter for renewable energy applications. The coupled inductor and switched capacitor are used to achieve high voltage gain and three power switches can be utilized to realize the power flows between the sources, the battery, and the load. The energy stored in the leakage inductance is recycled to reduce the voltage stress of the power switch. In addition, various operating stages are analyzed and design considerations are presented. Compared to the relevant converters, the proposed converter can realize power flows and achieve high voltage gain by using few components. Finally, a laboratory prototype of the proposed converter with input port voltage 24 V, battery port voltage 48 V, and output voltage 400 V with 200 W rated power is implemented to validate the feasibility and effectiveness of the theoretical analyses.INDEX TERMS Three-port converter, high voltage gain, coupled inductor, switched capacitor, renewable energy applications.

A high step-up DC-DC converter for renewable energy applications is proposed. Based on a three-winding coupled inductor and two voltage multiplier cells, the proposed converter obtains a high voltage conversion ratio. Through the passive clamp circuit, the voltage stress of the main switch is suppressed and the leakage energy of the coupled inductor is recycled. This leads to utilize a low on-state power resistance and low voltage-rating power switch that decreases the conduction losses. Meanwhile, the current stress of the diodes is minimized and the reverse recovery problem is alleviated. Thus, high efficiency can be achieved. Under continuous conduction mode (CCM) and discontinuous conduction mode (DCM), different operating principles and the mathematical derivations of the proposed converter are described in detail. To validate the feasibility of the proposed converter, a 320 W prototype with 25-38 V input voltage and 400 V output voltage is implemented. The measured maximum and full load efficiencies are 95.83 % and 94.96 %, respectively.

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Purpose The gait planning and control of quadruped crawling robot affect the stability of the robot walking on a slope. The control includes the position control in the swing phase, the force control in the support phase and the switching control in the force/position switching. To improve the passing ability of quadruped crawling robot on a slope, this paper aims to propose a soft control strategy. Design/methodology/approach The strategy adopts the statically stable crawling gait as the main gait. As the robot moves forward, the position/force section switching control is adopted. When the foot does not touch the ground, the joint position control based on the variable speed PID is performed. When the foot touches the ground, the position-based impedance control is performed, and a fuzzy multi-model switching control based on friction compensation is proposed to achieve smooth switching of force and position. Findings The proposed method offers a solution for stable passage in slope environment. The quadruped crawling robot can realize smooth switching of force/position, precise positioning in the swing process and soft control of force in the supporting phase. This fact is verified by simulation and test. Originality/value The method presented in this paper takes advantage of minimal tracking errors and minimal jitters. Simulations and tests were performed to evaluate the performance.

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