This paper presents the development of a nonlinear model predictive controller (MPC) for controlling variable speed hydropower (VSHP) plants. The MPC coordinates the turbine controller with the virtual synchronous generator (VSG) control of the power electronics converter to optimize the plant’s performance. The main objective is to deliver a fast power response to frequency deviations by utilizing the kinetic energy of the turbine and generator. This is made possible by allowing the turbine rotational speed to deviate temporarily from its optimal speed. In addition, the efficiency should be maximized while keeping the electric and hydraulic variables within their constraints. The simulation results show that the proposed MPC is also able to damp power oscillations in the grid, reduce water hammering in the penstock and improve the estimation of turbine head, turbine power and turbine flow. This ensures that the turbine head does not exceed its limits and that the overshoot in the turbine speed after a disturbance is reduced. Besides, the VSG converter control enables a fast power response by utilizing the rotational energy of the turbine and generator. Thereby, the VSHP can provide a significant amount of fast frequency reserves (FFR) to the grid.

本文介绍了用于控制变速水力发电厂（VSHP）的非线性模型预测控制器（MPC）的开发。MPC将涡轮机控制器与电力电子转换器的虚拟同步发电机（VSG）控制配合使用，以优化电厂的性能。主要目的是通过利用涡轮机和发电机的动能对频率偏差提供快速的功率响应。通过允许涡轮转速暂时偏离其最佳速度，可以实现这一点。另外，应在使电气和液压变量保持其约束范围内的同时，使效率最大化。仿真结果表明，提出的MPC还能抑制电网中的功率振荡，减少压力管道中的水锤现象，并改善涡轮机头，涡轮机功率和涡轮机流量的估算。这确保了涡轮机盖不超过其极限，并且减小了扰动之后涡轮机速度的过冲。此外，VSG变频器控制通过利用涡轮机和发电机的旋转能实现快速的功率响应。因此，VSHP可以为电网提供大量的快速频率储备（FFR）。