The Hybrid DC/DC converter is proposed to be used in the condition of bidirectional asymmetric power flow between DC buses. Firstly, this paper analyzes the switching mode of the Hybrid DC/DC converter under Extended Phase Shift (EPS) Control. Then, this paper calculates the converter losses and models the losses of the power and magnetic devices based on soft-switching characterization. The losses of those are not only by their material characteristics, but also closely related to the phase shift ratio. Based on the loss model and transmission power model of the converter, the power optimization allocation control strategy is proposed with the goal of efficiency optimization. Finally, the optimization method is verified through simulation analysis.

In DC microgrid, the uncontrollable DC link short-circuit current seriously shortens the life of the electrolytic capacitors in conventional AC/DC converters. To solve the issue, a new AC/DC converter with controllable DC link short-circuit current is proposed. Simulation results have verified the performance of the proposed converter.

This article proposes a new type of flux modulation linear permanent magnet (FMLPM) generator with dual-sided modular primary and consequent-pole structure to fulfil the low-cost and large-scale deployment requirements of wave energy converter. The key parameters of the generator are optimized using finite element analysis and the Taguchi method to maximize the performance of the designed generator. By comparing with traditional FMLPM, it is demonstrated that the proposed generator has advantages in terms of cost and performance and is more suitable for large-scale deployment of wave energy converter.

This paper investigates the design of passivity-based control for LCL-filtered grid-connected inverter based on the port-controlled Hamiltonian with dissipation (PCHD) model. The interconnection matrix is changed from the original antisymmetric matrix to the upper triangular matrix with zero corner elements, which simplifies the design process. What’s more, to enhance the stability of the system, the combination of classic control theory and modern control theory is proposed to design the damping parameters of the controller. The main idea is to ensure the inverter output impedance is passive. The relationship between the controller parameters and the external interaction stability is compared. The simulation results are carried out to validate the effectiveness and robustness of the proposed approach.

The power supply system design of a marine data buoy system is a challenge. Due to cost reasons, it is difficult for marine buoys to obtain electricity directly from the power grid. At present, marine buoys use solar energy, wind energy or wave energy to supply power to sensors. Among them, the employment of wave energy and solar energy has broad application prospects due to the complementary power production of these sources. This paper presents a new wave energy conversion (WEC) device for a marine buoy, which is composed of a floating body and a power generation device. In addition, a three-dimensional finite element simulation model of the buoy movement is established, and the simulation is carried out using hydrodynamic software. On the basis of simulation, experiments are carried out on a 50 kg core power generation unit to estimate the power generation performance of the proposed WEC device.

In grid-tied DC/AC inverter applications, the equivalent grid impedance often varies widely, which may limit the bandwidth of the inverter control system. This paper introduces a new method to perform the online estimation of the equivalent grid impedance with a Kalman filter by observing the grid voltage and grid current, as well as the voltage at the point of common coupling (PCC). With the estimated grid impedance, a high control bandwidth can be achieved for the grid-tied inverter through online regulation of the proportional coefficient of a current controller. A MATLAB/Simulink model of a grid-tied single-phase inverter has been setup to demonstrate the effectiveness of the proposed method. The simulation results show that the online estimated impedance is accurate enough and the inverter system can continuously maintain a high bandwidth, even under weak grid operating conditions.

Magnetic lead screw (MLS) owns many merits for wave energy generation system applications. However, to resist the huge, instantaneous impact of the waves, the radius of the mover and rotor of the MLS should be large to obtain sufficient stiffness. And the length of the mover needs to match the height of the wave to transfer as much power as possible. Therefore, a great many of permanent magnets (PMs) will be consumed when size of the traditional MLS is huge, and the maximum thrust force would be much greater than the wave excitation force. This will lead to the waste of PMs and poor starting performance. Also, the ideal spiral PMs are quite difficult to manufacture. Therefore, in this paper, a novel type single-helix MLS, which adopt single spiral PMs on the surface of the rotor and translator, is proposed to save PM consumption on the premise of meeting the demand of wave power generation system. The new structure provides a new choice for the application of magnetic screw in wave power system. The performance and the design features of the proposed novel MLS is analyzed through the three-dimensional finite-element method and compared with the traditional MLS and reluctance-based MLS. In addition, a simple spiral PM installation method based on discretized PMs for the proposed MLS is also proposed in this paper.

As a promising new transmission device, the magnetic lead screw (MLS) is considered to have a huge potential for wave energy conversion (WEC). The wave power generation device which using MLS can well transfer low-speed linear motion into high-speed rotation and offer much higher force density than that using traditional linear permanent magnet generator. The MLS has the advantages of inherent overload capability, high force density, no mechanical friction, and low maintenance. Therefore, in this paper, a wave power generation system consists of MLS and a permanent magnet synchronous generator (PMSG) is proposed. And a linear motor is used to simulate the sea wave. To verity the system, the prototype is manufactured and tested in the laboratory. In addition, the MLS performance is evaluated by using the finite- element analysis (FEA).