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- Conventional Hydro
Coordinated Predictive Control of a Hydropower Cascade
Lead Companies
Carnegie Mellon University
Lead Researcher (s)
- Andrew Hamann
Hydropower is an important renewable energy resource. It is low-carbon, emits nearly no particulate pollution, can ramp quickly, and is capable of storing energy across many hours or days. While it is a very valuable resource by itself, hydropower can also serve as a key enabler for the increased penetration of non-dispatchable renewable energy resources like wind and solar power. This project focused on developing an optimization-based coordinated control framework for a hydropower cascade. It consisted largely of two parts. The first is the development of the coordination scheme. The second is the simulation and state estimation tools that were developed to allow comparisons between historical operations and the operations dictated by the coordination scheme. The coordinated control scheme that we developed is based on a control technique known as Model Predictive Control (MPC), wherein a linear state space model is designed to model the hydraulics of a hydropower cascade. Here, the hydraulics model describes how water flows in a hydropower cascade change the reservoir elevations behind each hydropower plant. The model accounts for the delay between water discharged from the upstream plant affecting the forebay elevation of the downstream plant. The control scheme also accounts for the non-linear character of tailrace elevations. There is an obvious relationship between the amount of water discharged into the tailrace and the tailrace elevation. Our modeling work takes that a step further by identifying the conditions that lead to encroachment and modeling encroachment. Encroachment is when the downstream forebay backs up into the upstream tailrace, causing the tailrace elevation to be higher than it would be otherwise. The optimization scheme also accounts for the relationship between turbine discharge, hydraulic head, and powerhouse generation in a hydropower plant. Turbine discharge and hydraulic head are mapped to a corresponding amount of powerhouse generation using a three-dimensional piecewise planar function. This function is fit to historical operations data. Since the relationship between the three variables can be represented using a set of linear functions, the model for hydropower production can be integrated into a linear or quadratic program. This results in an optimization model that is both fast and accurate, an improvement over other coordinated control schemes that are based on nonlinear or mixed-integer programming. The objective function was formulated to minimize the sum of the squared turbine discharge and spill for each hydropower plant. The weights were chosen such that water was preferentially discharged from large surface area reservoirs to small surface area reservoirs. This allocates a certain volume of water such that it results in the maximum total hydraulic head. Weighting turbine discharges in this way is unique in the hydropower optimization literature. We tested the coordinated control scheme on the Mid-Columbia hydropower system. The MidColumbia consists of seven dams on the Columbia River in Eastern Washington State. Historical data on system operations allowed us to benchmark the performance of our coordination scheme with actual system operations. Further data was provided that allowed us to properly calibrate the parameters of our model, including forebay and tailrace curves, travel times, and hydropower production functions. Simulations were conducted for a five-day period with five-minute time resolution. The results of our simulations, in brief, can be condensed into four areas. 1. The hydraulic potential of the system (H/K) increased steadily over the course of the simulations. At the end of the simulation period, the total system H/K was 0.6% higher than in the historical case. This translates to several feet of additional hydraulic head. 2. The net energy stored in the cascade increased. Overall, the net energy benefit was 1708 MWh, or 0.33% of the total energy generated during the simulation period. In general, Grand Coulee ran an energy deficit (i.e., its forebay was lower in the optimized case than the historical case) and the remaining hydropower plants ran an energy surplus. 3. Ramping was reduced substantially. Quantitative measures indicated that ramping decreased substantially at every hydropower plant besides Grand Coulee. Qualitatively, the discharge profiles were much smoother in the optimized case than in the historical case. This method of operation could have substantial (but uncertain) benefits to hydropower plant owners and operators due to less unit cycling and ramping, which results in lower maintenance and repair costs. 4. System constraints were satisfied. The Mid-Columbia system is constrained at many times of the year due to environmental limits on turbine discharge, spill, and flow ramping. These limits are designed to ensure the health of salmon runs on the Columbia River and the spawning areas in the Hanford Reach downstream of Priest Rapids. One of the primary benefits of doing coordinated control in an optimization framework is that system constraints can be explicitly obeyed. This ensures that regulatory and legal bounds on system operations are satisfied completely. The second part of the research involved the development of a state estimation procedure for a hydropower cascade. Evaluating the coordinated control scheme necessitated developing a state estimation procedure to reconcile measured values of turbine discharge, spill, and forebay elevation. In lieu of being able to test the outputs of the coordinated control scheme on the actual Mid-Columbia system or on a high-fidelity simulator, an inherently inaccurate computer model must be used. This model will contain some modeling errors. Likewise, the measured flows and forebay elevations can be biased and noisy. These biases and noise levels are unknown and, a priori, we do not know which values can be trusted and to what extent. The state estimation procedure takes these values and the hydraulic model, and adjusts the measurements such that the model is open-loop stable and the estimated measurements are consistent with each other. The general idea is that one flow measurement is assumed to be the true flow through the system, and the other flows (upstream and/or downstream) are adjusted to reduce the residual error between the estimated flow and the measured flow. Constraints are added to the procedure to ensure that the estimated flow profile is similar to the measured flow profile. Results are given demonstrating the practical efficacy of the proposed state estimation method.
Technology Application
Conventional Hydro
Research Category
Interconnect Integration and Markets
Research Sub-Category
Hydraulic Forecasting
Status
complete
Completion Date
2015
- Conventional Hydro
Cost Data Collection and Modeling for Hydropower
Lead Companies
Oak Ridge National Laboratory (ORNL)
Lead Researcher (s)
- Gbadebo Oladosu (oladosuga@ornl.gov)
This project encompasses the data collection, modeling, and analysis of the costs and performance of hydropower plants in U.S. markets. The project and associated activities are essential to provide necessary capabilities for DOE and other stakeholders to track and quantify the impacts of research activities on the economic competitiveness of hydropower technologies. Thus, the three core aspects of the project are 1. Information gathering and analysis to support the identification and justification of high-impact R&D efforts 2. Provide data on national-scale hydropower costs and performance for use by research organizations and policymakers 3. Provide a vehicle by which DOE WPTO can track and communicate the impact of R&D investments.
Technology Application
Conventional Hydro
Research Category
Environmental and Sustainability
Research Sub-Category
Markets
Status
ongoing
Completion Date
TBD
- Pumped Storage
Cost Effective Small Scale Pumped Storage Configuration [HydroWIRES]
Lead Companies
Obermeyer Hydro
Lead Researcher (s)
- Greg Stark, greg.stark@nrel.gov
Since 2000 only one new pumped storage hydropower project has been constructed in the United States. In order to increase the future opportunity for pumped storage development, reductions in cost and scale are necessary. Historically, pumped storage projects have required large capacity to overcome the fixed costs associated with custom engineering of complex underground structures with associated geological risk. The Obermeyer Hydro submersible pump-turbine offers a standard, scalable solution which reduces underground construction and risk. Technology Application
Pumped Storage
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
ongoing
Completion Date
TBD
- Conventional Hydro
Cyanophage treatment development for mitigating freshwater Harmful Algal Blooms caused by cyanobacteria
Lead Companies
Bureau of Reclamation
Lead Researcher (s)
- Christopher Waechter
This study will identify a new treatment for harmful algal blooms that could potentially lead to Reclamation administered HAB treatments, as well as help develop mitigation techniques that could be commercialized with potential future private industry partners. Recent large scale harmful algal bloom (HAB) events in lakes and large river systems emphasize the need for more research on freshwater HAB to improve water quality and protect public health.
Technology Application
Conventional Hydro
Research Category
Environmental and Sustainability
Research Sub-Category
Water Resources
Status
ongoing
Completion Date
2022
- Physical & Cyber Security
Cybersecurity Guidance for Marine Renewable Energy Systems
Lead Companies
PNNL
Lead Researcher (s)
- Fleur dePeralta
This project provides an approach to assessing the cyber security threats to the information systems and the consequences on the assets. The approach will then be used as input to a guidance document that will inform developers of future digital assets and ways to secure their operational and information systems.
Technology Application
Physical & Cyber Security
Research Category
Research Sub-Category
Status
ongoing
Completion Date
TBD
- Conventional Hydro
Dam Anchoring Principles
Lead Companies
CEATI International
Lead Researcher (s)
- #0238
to develop current practice design principles to guide designers and dam owners in selecting the most appropriate anchor type and detailing for the situation at hand, based on the experiences and lessons learned from past case histories of dam anchoring designs.
Technology Application
Conventional Hydro
Research Category
Dam or Weir
Research Sub-Category
Dam Safety
Status
ongoing
Completion Date
Expected 2020
- Conventional Hydro
Dam Management Matters for Survival of Endangered Fish in Grand Canyon
Lead Companies
U.S. Geological Survey
Lead Researcher (s)
- Kimberly Dibble
This study modeled temperature changes in the Colorado River and imagined a future in which water storage is either mostly in Lake Powell or mostly in Lake Mead and what those different scenarios mean for native fish.
Technology Application
Conventional Hydro
Research Category
Environmental and Sustainability
Research Sub-Category
Fish and Aquatic Resources
Status
complete
Completion Date
2020
- Conventional Hydro
Dam Safety Essentials for Engineers
Lead Companies
CEATI
Lead Researcher (s)
- #0237
A training program for dam safety engineers, including customizable powerpoint files, e-learning modules and materials for a failure modes workshop.
Technology Application
Conventional Hydro
Research Category
Dam or Weir
Research Sub-Category
Dam Safety
Status
complete
Completion Date
2020
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Contact Marla Barnes at: marla@hydro.org