Research on Optimal Power Control Technology of Direct-drive Wave Power Generation System Based on Model Prediction
Huang Lei1, Wei Lai1, Yang Jianlong1, Hu Minqiang2
1. School of electrical engineering Southeast University Nanjing 210096 China;
2. School of electrical and automation engineering Nanjing Normal University Nanjing 210023 China
The direct-drive wave power generation system has advantages of simple structure, low cost, and high efficiency, and has received extensive attention from scholars. Permanent magnet linear generators are implemented in direct-drive wave power generation system for its high power density, and electromagnetic force of the linear generator is controlled to realize maximum energy capture of the system. However, the power capture strategy of the direct-drive wave power generation system has a great influence on the energy obtained of the system. Model predictive control has the characteristics of multiple constraints and can solve the safety problems of wave power generation devices in extreme sea conditions, and is suitable for power capture control in direct-drive wave power generation systems. Therefore, based on Model Prediction, an optimal power control strategy of direct-drive wave power generation system is proposed to improve the energy capture of generators.
Firstly, the hydrodynamic mathematical model of the direct-drive wave power generation device is established, and frequency response of the wave front equation to an excitation force and obtained by using boundary element method. In addition, the dynamic mathematical model of the permanent magnet linear generator are analyzed are derived. Secondly, a power control strategy based on model prediction is derived for direct-drive wave power generation system. In the power control strategy, it is divided into power capture strategy and power tracking control strategy to realize the conversion of wave energy into electrical energy and import it into the DC bus. This paper focuses on the research on the power capture strategy, and analyzes the optimal power capture strategy based on model prediction from three perspectives: control strategy, prediction interval and cost function. The State-space equations, cost function and constraints are analyzed and derived. Then, the model predictive current control is implemented for dynamic power tracking. And the stability analysis of the control system was carried out. Thirdly, Based on the theoretical derivation, the Control block diagram of direct-drive wave power generation system is established. The simulation model of the system is built, and the simulation parameters of wave power generation are listed out. Moreover, the energy captured by the PMLG under different control strategies is compared, and the effect of prediction interval on power capture under different cost function are obtained and analyzed. Through comparative analysis, the optimized prediction interval parameters are obtained. Different cost function with considering the most power into the DC bus and considering the electromagnetic power of PMLG are compared and analyzed. All the simulation models are built, and simulation analysis was carried out. The simulation results show that the optimal power capture strategy based on model prediction can effectively improve the energy capture of generators under irregular waves from wave power generation systems. In addition, considering the cost function that maximizes the power imported into the DC bus can increase the energy imported into the DC bus by the generator, which has important practical value. Lastly,Experiment research are implement by lab experimental platform. The experiment results under different driving speed and dynamic wave condition adjustment are obtained and analyzed.
The following conclusions can be drawn: 1) the proposed optimal power control strategy is suitable for direct-drive wave power generation system and can improve the energy captured by the generator from the waves. 2) The prediction interval of EMPC can greatly affect the energy absorption of the system, and the cost functions have significant effect on the energy feeds into the DC bus. Therefore, the selecting of appropriate prediction interval and cost function is of great practical value for performance improvement. 3) The experimental results show that the system can effectively realize the tracking control of current under different working conditions, by using the proposed control strategy.
黄磊, 魏莱, 杨建龙, 胡敏强. 基于模型预测的直驱式波浪发电机机侧最优功率控制技术研究[J]. 电工技术学报, 0, (): 9033-33.
Huang Lei, Wei Lai, Yang Jianlong, Hu Minqiang. Research on Optimal Power Control Technology of Direct-drive Wave Power Generation System Based on Model Prediction. Transactions of China Electrotechnical Society, 0, (): 9033-33.
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