Utility scale wind turbines (greater than 1 MW) are used to produce green energy and support the transmission grid. However, small to midsize wind turbines can support rural areas and local niches such as factories, farms and rural electric cooperatives while stabilizing the distributed power grid. In previous research we have shown that replacing the conventional gearbox transmission of midsize turbines with a hydrostatic transmission can increase system reliability, decrease nacelle weight, lower the levelized cost of electricity, and remove power electronics from the system [1].Previous wind turbine control research focuses on maximizing the power capture in region 2, when wind speeds are below the rated wind speed. In region 3, when wind speeds are above the rated speed, turbine blades are pitched to intentionally dissipate power so that the turbine operates at its rated power. The goal of hybridization, presented previously [2], is to capture and store extra energy when the turbine is in region 3, and release that&nbsp; energy when the turbine is in region 2, increasing the total energy captured by the turbine. This extra energy is stored in a hydraulic accumulator. The proposed system also has ancillary benefits. High power stored in the accumulator can help with fault ride-through, create a smoother power output, and stored energy can be used to power pitch and yaw axes in high wind conditions.This paper reports on recent experimental results on the hydrostatic hybrid wind turbine transmission. An energy storage system has been added to the power regenerative hydrostatic transmission test platform at the University of Minnesota [3]. With this test platform, realistic wind loading conditions for a 60-kW horizontal axis wind turbine with a hybrid transmission can be emulated. The new experimental setup is shown in figure 1.&nbsp;&nbsp;Figure 1: Power Regenerative Test Platform with Hybrid UpgradeIn this paper, the benefits of the hybrid transmission are summarized. The design of the hybridization system for the power regenerative test platform, the hardware embodiment and the experimental procedure are described in detail. The previous simulation results that predicted &nbsp;how much additional power can be obtained [2] are validated experimentally. The effect of accumulator size, pre-charge pressure and maximum pressure on additional energy obtained by hybridization are also documented.&nbsp;References:[1] B. Mohanty and K. A. Stelson, “High Fidelity Dynamic Modeling and Control of Power Regenerative Hydrostatic Wind Turbine Test Platform,” Proc. of the 2018 Bath/ASME Symposium on Fluid Power and Motion Control, American Society of Mechanical Engineers, 2018.[2] E. Mohr, B. Mohanty and K. A. Stelson, “Short-Term Energy Storage System for Hydraulic Hybrid Wind Turbine Transmission,” Proc. of the 2020 Bath/ASME Symposium on Fluid Power and Motion Control, American Society of Mechanical Engineers, 2020.[3] B. Mohanty, F. Wang and K. A. Stelson, Design of a Power Regenerative Hydrostatic Wind Turbine Test Platform, JFPS International Journal of Fluid Power Systems, 2019, vol. 11, &nbsp;no. 3, pp. 130–135.&nbsp;

Experimentation on a Hydraulic Energy Storage System for Mid-Size Wind Turbines

Paper Proceedings: https://asmedigitalcollection.asme.org/FPST/FPMC2021/volume/85239

2021 ASME/BATH Symposium on Fluid Power and Motion Control (FPMC2021)

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