Passive Model Predictive Control on a Two-Body Self-Referenced Point Absorber Wave Energy Converter
Passive Model Predictive Control on a Two-Body Self-Referenced Point Absorber Wave Energy Converter
复制标题
二体自参考点吸收波能转换器的无源模型预测控制
作者：
D. Montoya;E. Tedeschi;L. Castellini;T. Martins
波浪能是当今最有前途的可再生能源之一，然而，波浪能技术尚未达到完全商业化的阶段。实现这一目标的一个关键方面是为每个选定的波浪能转换器（WEC）确定有效的控制策略，以便从波浪中提取最大能量，同时尊重设备的物理约束。模型预测控制（MPC）可以满足这些要求。通常，MPC被公式化为具有线性约束的二次规划问题（例如，位置、速度和动力输出（PTO）力）。由于在最一般的情况下，这种控制技术需要PTO系统和电网之间的双向功率流，因此它具有与无功控制类似的特性。这意味着，在某些操作条件下，能量损失可能等于或甚至大于产生的能量。由于许多WEC的设计只允许单向潮流，它是必要的设置非线性约束。这使得优化问题在计算时间方面显著更昂贵。这项工作提出了两个MPC控制策略应用于两体点吸收器，从两个不同的角度来解决这个问题：（a）适应MPC制定被动加载策略;（B）适应线性约束的MPC，以便只允许单向功率流。结果表明，这两种替代方案具有相似的性能，在计算时间相比，定期MPC和获得更多的权力比线性被动控制，从而证明是一个很好的选择，单向PTO系统。
Wave energy is nowadays one of the most promising renewable energy sources; however, wave energy technology has not reached the fully-commercial stage, yet. One key aspect to achieve this goal is to identify an effective control strategy for each selected Wave Energy Converter (WEC), in order to extract the maximum energy from the waves, while respecting the physical constraints of the device. Model Predictive Control (MPC) can inherently satisfy these requirements. Generally, MPC is formulated as a quadratic programming problem with linear constraints (e.g., on position, speed and Power Take-Off (PTO) force). Since, in the most general case, this control technique requires bidirectional power flow between the PTO system and the grid, it has similar characteristics as reactive control. This means that, under some operating conditions, the energy losses may be equivalent, or even larger, than the energy yielded. As many WECs are designed to only allow unidirectional power flow, it is necessary to set nonlinear constraints. This makes the optimization problem significantly more expensive in terms of computational time. This work proposes two MPC control strategies applied to a two-body point absorber that address this issue from two different perspectives: (a) adapting the MPC formulation to passive loading strategy; and (b) adapting linear constraints in the MPC in order to only allow an unidirectional power flow. The results show that the two alternative proposals have similar performance in terms of computational time compared to the regular MPC and obtain considerably more power than the linear passive control, thus proving to be a good option for unidirectional PTO systems.