Presas Alexandre, Valentin David, Egusquiza Mònica, Valero Carme, Egusquiza Eduard
Center for Industrial Diagnostics and Fluid Dynamics (CDIF), Polytechnic University of Catalonia (UPC), Av. Diagonal, 647, ETSEIB, 08028 Barcelona, Spain.
Sensors (Basel). 2018 Mar 30;18(4):1038. doi: 10.3390/s18041038.
Hydropower plants are of paramount importance for the integration of intermittent renewable energy sources in the power grid. In order to match the energy generated and consumed, Large hydraulic turbines have to work under off-design conditions, which may lead to dangerous unstable operating points involving the hydraulic, mechanical and electrical system. Under these conditions, the stability of the grid and the safety of the power plant itself can be compromised. For many Francis Turbines one of these critical points, that usually limits the maximum output power, is the full load instability. Therefore, these machines usually work far away from this unstable point, reducing the effective operating range of the unit. In order to extend the operating range of the machine, working closer to this point with a reasonable safety margin, it is of paramount importance to monitor and to control relevant parameters of the unit, which have to be obtained with an accurate sensor acquisition strategy. Within the framework of a large EU project, field tests in a large Francis Turbine located in Canada (rated power of 444 MW) have been performed. Many different sensors were used to monitor several working parameters of the unit for all its operating range. Particularly for these tests, more than 80 signals, including ten type of different sensors and several operating signals that define the operating point of the unit, were simultaneously acquired. The present study, focuses on the optimization of the acquisition strategy, which includes type, number, location, acquisition frequency of the sensors and corresponding signal analysis to detect the full load instability and to prevent the unit from reaching this point. A systematic approach to determine this strategy has been followed. It has been found that some indicators obtained with different types of sensors are linearly correlated with the oscillating power. The optimized strategy has been determined based on the correlation characteristics (linearity, sensitivity and reactivity), the simplicity of the installation and the acquisition frequency necessary. Finally, an economic and easy implementable protection system based on the resulting optimized acquisition strategy is proposed. This system, which can be used in a generic Francis turbine with a similar full load instability, permits one to extend the operating range of the unit by working close to the instability with a reasonable safety margin.
水电站对于将间歇性可再生能源并入电网至关重要。为了使发电量与用电量相匹配，大型水轮机必须在非设计工况下运行，这可能会导致涉及水力、机械和电气系统的危险不稳定运行点。在这些情况下，电网的稳定性和电厂本身的安全性可能会受到损害。对于许多混流式水轮机来说，这些关键点之一，即通常限制最大输出功率的满负荷不稳定。因此，这些机组通常在远离这个不稳定点的情况下运行，从而缩小了机组的有效运行范围。为了扩大机组的运行范围，在有合理安全裕度的情况下更接近这个点运行，监测和控制机组的相关参数至关重要，而这些参数必须通过精确的传感器采集策略来获取。在一个大型欧盟项目的框架内，对位于加拿大的一台大型混流式水轮机（额定功率为444兆瓦）进行了现场测试。使用了许多不同的传感器来监测机组在其整个运行范围内的几个工作参数。特别是对于这些测试，同时采集了80多个信号，包括十种不同类型的传感器和几个定义机组运行点的运行信号。本研究着重于采集策略的优化，其中包括传感器的类型、数量、位置、采集频率以及相应的信号分析，以检测满负荷不稳定并防止机组达到这一点。遵循了一种系统的方法来确定这一策略。已发现用不同类型传感器获得的一些指标与振荡功率呈线性相关。基于相关特性（线性、灵敏度和反应性）、安装的简易性和所需的采集频率确定了优化策略。最后，提出了一种基于所得优化采集策略的经济且易于实施的保护系统。该系统可用于具有类似满负荷不稳定情况的通用混流式水轮机，通过在有合理安全裕度的情况下接近不稳定点运行，允许扩大机组的运行范围。
