Resonance Control Based on Hydrodynamic Analysis for Underwater Direct Drive Wave Energy Converter

Wave energy has great prospect among many forms of marine renewable energy for its high density and storage. This paper proposes an underwater direct drive wave energy converter (UDDWEC), which is composed of a submerged point absorbing buoy and a linear-rotating axial flux permanent magnetic generator (LR-AFPMG). In addition, a maximum energy capture control strategy, resonance control, is derived for UDDWEC, based on small amplitude oscillation and hydrodynamic analysis. The proposed control strategy assumes the availability of sea condition such as wave height and period. This control strategy has three main characteristics. Firstly, this control strategy is derived based on hydrodynamic analysis of the submerged point absorber. Added mass, radiation damping and other hydrodynamic parameters are obtained to participate in UDDWEC dynamic model. Secondly, a LR-AFPMG is applied as power take-off device to realize energy conversion, which can improve the power density. Thirdly, small amplitude oscillation can be changed into long stroke rotary motion through the LR-AFPMG. The reliability and effectiveness of the proposed control strategy are assessed at various operation conditions for a heaving system and the validity for the UDDWEC is verified.

Design of Inverter Side of Modular Grid Simulator Based on Proportional integral-Quasi-proportional resonance Control

The tracking of a given voltage in the traditional double closed-loop proportional integral control in the current power grid simulator has problems such as static difference, delay and oscillation. It is proposed that the voltage outer loop and current inner loop of the inverter side of the power grid simulator adopt proportional integral and quasi-proportional resonance control respectively, and the topology of the inverter adopts a cascaded modular design to establish a single-phase inverter model. Compared with the traditional double closed-loop proportional-integral control, it is verified that the proportional-integral-quasi-proportional resonant controller can effectively improve the system’s ability to track the command voltage and the stability of the output voltage.

Application of electric spring in coal mine power supply

With the continuous improvement of mine automation, coal mines have higher and higher requirements for the quality of power supply voltage, and voltage fluctuations have become one of the factors that threaten the safe operation of coal mines. In order to solve this problem, this article uses the electric spring (ES) in the coal mine power supply system. First, it analyzes the working principle of the electric spring. Next, aiming at the deficiencies of the resonance control strategy, a compound control strategy in which quasi-proportional resonance control (QPR) and repetitive control are parallel is proposed. The introduction of repetitive control can suppress the periodic disturbance of the power grid, effectively improve the steady-state accuracy, and reduce system harmonics. Then, the design method of repeated controller parameters is studied in detail. Finally, MATLAB/Simulink is used to build a simulation model, and dSPACE is used as the control core to build an ES experiment platform. Simulation and experimental results verify the correctness and effectiveness of the proposed control algorithm, and point out that the electric spring can ensure the voltage stability of key electrical equipment and provide a reliable guarantee for the safe production of the mine.