Enhanced Power System Operational Performance with Anticipatory Control under Increased Penetration of Wind Energy

abstract: As the world embraces a sustainable energy future, alternative energy resources, such as wind power, are increasingly being seen as an integral part of the future electric energy grid. Ultimately, integrating such a dynamic and variable mix of generation requires a better understanding of renewable generation output, in addition to power grid systems that improve power system operational performance in the presence of anticipated events such as wind power ramps. Because of the stochastic, uncontrollable nature of renewable resources, a thorough and accurate characterization of wind activity is necessary to maintain grid stability and reliability. Wind power ramps from an existing wind farm are studied to characterize persistence forecasting errors using extreme value analysis techniques. In addition, a novel metric that quantifies the amount of non-stationarity in time series wind power data was proposed and used in a real-time algorithm to provide a rigorous method that adaptively determines training data for forecasts. Lastly, large swings in generation or load can cause system frequency and tie-line flows to deviate from nominal, so an anticipatory MPC-based secondary control scheme was designed and integrated into an automatic generation control loop to improve the ability of an interconnection to respond to anticipated large events and fluctuations in the power system.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Can geoengineering be optimised?

Geoengineering is the intentional, large-scale manipulation of Earth’s climate. It has been suggested that this could be done to counteract or ameliorate the effects of anthropogenic climate change, to reduce its negative impacts or buy time for global greenhouse gas emissions to be reduced. Stratospheric aerosol injection, where aerosols in the stratosphere are used to reflect sunlight and so cool climate, has been widely studied. Altering the altitude, latitude, or timing of aerosol injections could result in different radiative forcing patterns, which suggests there may be potential to “optimise” stratospheric aerosol injection geoengineering to achieve particular climate goals. The extent to which geoengineering could be optimised, beyond idealised studies that counteract the global mean temperature increase of greenhouse gases, has only relatively recently begun to be explored. Chapter 1 discusses the background of geoengineering as a concept and includes a literature review and discussion of robust results that have emerged from modelling studies of geoengineering. Chapter 2 uses a combination of analytical techniques and the simple climate model, FaIR, to examine different scenarios for “peak-shaving” – temporarily using geoengineering to hold global mean temperatures below a certain threshold – and examines trade-offs between the amount of warming avoided and the implied duration of commitment to geoengineering. Chapters 3-5 analyse simulations from the HadCM3 climate model, simulated using climateprediction.net, which uses thousands of volunteer computers to generate large ensembles of simulations with differing distributions of stratospheric aerosol optical depth counteracting an abrupt quadrupling of carbon dioxide to represent different attempts at tailoring geoengineering. Chapter 3 details initial calibration and characterisation of the response to simple patterns of radiative forcing, and establishes that the temperature response to different patterns of forcing is, to a good approximation, linear and additive. Chapter 4 expands on this and discusses various methods for optimising for temperature and precipitation, including analysis of trade-offs for attempting to optimise temperature in different regions, and analysis of whether there are a limited number of fundamental modes of response in the HadCM3 climate model to a range of imposed radiative forcing patterns. Chapter 5 examines the impact of geoengineering on climate and weather extremes, using metrics that represent heatwaves, flooding, and dry periods, and analysing any differences in the distribution of extreme events between simulations of the preindustrial and geoengineered climates. In the final chapter, results and conclusions are summarised, and possible future work is outlined

Design, Implementation, and Verification of a Reactor Protection System Using HFC6000

Recently, a nuclear power plant physical simulator to support instrumentation and control (I&C) research has been constructed at the University of Western Ontario using industry-grade sensors and actuators. This platform, known as the Nuclear Power Control Test Facility (NPCTF), provides means to safely inject faults and examine their effects on the system. The NPCTF may be configured into a number of nuclear power plant (NPP) types, but focus has been placed on CANadian Deuterium Uranium (CANDU) type. In a CANDU based NPP, there are two independent and separated systems with decision-making units capable of actuating two shutdown systems. These units form the reactor protection system, and monitor critical system variables to ensure that they remain within safe operating limits. For this work, in ongoing efforts to further improve the fidelity of the NPCTF, a dedicated reactor protection system has been realized. This system has been implemented through a United States Nuclear Regulatory Commision certified safety programmable logic controller (PLC), known as the HFC6000. This has been integrated with the NPCTF through a standard industrial interface, and performs monitoring functions and decision logic operations. The reactor protection system responds to contingencies by issuing trip signals to perform safety shutdown actions. The designed system has undergone a full verification and validation (V&V) process. Nine CNSC design basis events have been considered under full-system testing, including the loss-of-coolant-accident and loss-of-reactor-control. The designed logic achieved a 100% success rate on 25 trials. Further, the implemented system produced no spurious trips during normal operations. The relationship between CANDU type NPPs and the NPCTF has been established. The work has also concluded that the NPCTF is capable of replicating dynamic relationships among different variables in an NPP. Through V&V tests,, the designed logic, and implemented system using HFC6000 have been proven to be successful according to the safety system criteria from the Canadian Nuclear Safety Commission

Surveillance Using Multiple Unmanned Aerial Vehicles

This study examines the performance and limitations of a heuristic cooperative control (CC) surveillance algorithm for multiple unmanned aerial vehicles (UAVs) under both simulation and demonstration. The algorithm generates Dubin\u27s based paths and provides velocity feedback to accomplish simultaneous arrival onto a surveillance orbit around the target and maintains position while orbiting. The CC algorithm has two modes: one that generates commands to multiple UAVs for simultaneous arrival to a surveillance orbit, and one that maintains equal angular spacing about the orbit. In addition to positional performance metrics, percentage of target in-view time was also measured based on the UAV\u27s side camera field of view (FOV). Simulation tested both modes under wind conditions of 0%, 10%, 25%, and 50% of the nominal airspeed (Vnom). Results showed that the algorithm maintained UAV position with winds 25% of Vnom, but instabilities appeared at 50% where large overshoots appeared on the downwind side of the orbit. Target visibility was most impacted by crosstrack errors that steadily grew with increasing winds. Roll of the UAV showed the greatest impact on the FOV due to its coupling effect with crosstrack error. Overall target in-view time also improved with increasing numbers of UAVs for all wind conditions

Implementation of self-tuning control for turbine generators

PhD ThesisThis thesis documents the work that has been done towards the development of a 'practical' self-tuning controller for turbine generator plant. It has been shown by simulation studies and practical investigations using a micro-alternator system that a significant enhancement in the overall performance in terms of control and stability can be achieved by improving the primary controls of a turbine generator using self-tuning control. The self-tuning AVR is based on the Generalised Predictive Control strategy. The design of the controller has been done using standard off-the-shelf microprocessor hardware and structured software design techniques. The proposed design is thus flexible, cost-effective, and readily applicable to 'real' generating plant. Several practical issues have been tackled during the design of the self-tuning controller and techniques to improve the robustness of the measurement system, controller, and parameter estimator have been proposed and evaluated. A simple and robust measurement system for plant variables based on software techniques has been developed and its suitability for use in the self-tuning controller has been practically verified. The convergence, adaptability, and robustness aspects of the parameter estimator have been evaluated and shown to be suitable for long-term operation in 'real' self-tuning controllers. The self-tuning AVR has been extensively evaluated under normal and fault conditions of the turbine generator. It has been shown that this new controller is superior in performance when compared with a conventional lag-lead type of fixed-parameter digital AVR. The use of electrical power as a supplementary feedback signal in the new AVR is shown to further improve the dynamic stability of the system. The self-tuning AVR has been extended to a multivariable integrated self-tuning controller which combines the AVR and EHG functions. The flexibility of the new AVR to enable its expansion for more complex control applications has thus been demonstrated. Simple techniques to incorporate constraints on control inputs without upsetting the loop decoupling property of the multivariable controller have been proposed and evaluated. It is shown that a further improvement in control performance and stability can be achieved by the integrated controller.Parsons Turbine Generators Ltd

Constraints on Earth system functioning at the Paleocene-Eocene Thermal Maximum from the marine silicon cycle

The Paleocene‐Eocene Thermal Maximum (PETM, ca. 56 Ma) is marked by a negative carbon isotope excursion (CIE) and increased global temperatures. The CIE is thought to result from the release of 13C‐depleted carbon, although the source(s) of carbon and triggers for its release, its rate of release, and the mechanisms by which the Earth system recovered are all debated. Many of the proposed mechanisms for the onset and recovery phases of the PETM make testable predictions about the marine silica cycle, making silicon isotope records a promising tool to address open questions about the PETM. We analyzed silicon isotope ratios (δ30Si) in radiolarian tests and sponge spicules from the Western North Atlantic (ODP Site 1051) across the PETM. Radiolarian δ30Si decreases by 0.6‰ from a background of 1‰ coeval with the CIE, while sponge δ30Si remains consistent at 0.2‰. Using a box model to test the Si cycle response to various scenarios, we find the data are best explained by a weak silicate weathering feedback, implying the recovery was mostly driven by nondiatom organic carbon burial, the other major long‐term carbon sink. We find no resolvable evidence for a volcanic trigger for carbon release, or for a change in regional oceanography. Better understanding of radiolarian Si isotope fractionation and more Si isotope records spanning the PETM are needed to confirm the global validity of these conclusions, but they highlight how the coupling between the silica and carbon cycles can be exploited to yield insight into the functioning of the Earth system

A 200-million year delay in permanent atmospheric oxygenation

S.W.P. acknowledges support from a Leverhulme Research Fellowship and a Royal Society Wolfson Research Merit Award. A.B. acknowledges support from the University of Johannesburg in the form of a Distinguished Visiting Professorship. D.T.J. acknowledges support from a NASA Exobiology award (NNX15AP58G).The rise of atmospheric oxygen fundamentally changed the chemistry of surficial environments and the nature of Earth’s habitability1. Early atmospheric oxygenation occurred over a protracted period of extreme climatic instability marked by multiple global glaciations2,3, with the initial rise of oxygen concentration to above 10−5 of the present atmospheric level constrained to about 2.43 billion years ago4,5. Subsequent fluctuations in atmospheric oxygen levels have, however, been reported to have occurred until about 2.32 billion years ago4, which represents the estimated timing of irreversible oxygenation of the atmosphere6,7. Here we report a high-resolution reconstruction of atmospheric and local oceanic redox conditions across the final two glaciations of the early Palaeoproterozoic era, as documented by marine sediments from the Transvaal Supergroup, South Africa. Using multiple sulfur isotope and iron–sulfur–carbon systematics, we demonstrate continued oscillations in atmospheric oxygen levels after about 2.32 billion years ago that are linked to major perturbations in ocean redox chemistry and climate. Oxygen levels thus fluctuated across the threshold of 10−5 of the present atmospheric level for about 200 million years, with permanent atmospheric oxygenation finally arriving with the Lomagundi carbon isotope excursion at about 2.22 billion years ago, some 100 million years later than currently estimated.PostprintPeer reviewe

The impact of volcanic halogens, climate change, and sulfate aerosol geo-engineering on the atmospheric effects of volcanic eruptions

The evolution of volcanic sulfur, stratospheric composition and radiative forcing following explosive volcanic eruptions injecting sulfur directly into the stratosphere is well understood. However, how the co-emission of volcanic halogens, climate change, and concurrent sulfate aerosol geo-engineering would alter the atmospheric effects of sulfur-only explosive volcanic eruptions has, previously, been under-researched. In this thesis, aerosol-chemistry-climate model simulations are utilised to show that the co-emission of volcanic halogens alongside sulfur (halogen co-emission) and climate change amplify the volcanic forcing of volcanic eruptions, mainly caused by a reduction in the aerosol lifetime and aerosol size. Stratospheric ozone is shown to be less vulnerable to sulfur-only eruptions, but more sensitive to halogen co-emission eruption scenarios in the future compared to the present-day, due to the projected decline in stratospheric halogen abundance and ozone recovery. An explosive volcanic eruption during stratospheric sulfate aerosol geo-engineering is found to lead to additional negative radiative forcing and total column ozone depletion, but the response is complex and non-additive. This thesis emphasises the need to include volcanic halogen emissions when simulating the climate effects of past or future eruptions as well as the necessity to maintain space-borne observations of stratospheric compounds to better constrain the stratospheric injection estimates of volcanic eruptions. It identifies a novel climate-volcano feedback and highlights the need to re-evaluate the use of constant volcanic forcing typically used in future climate projections. Furthermore, this thesis demonstrates the difficulties associated with maintaining a stable level of radiative forcing in the event of an explosive volcanic eruption during sulfate aerosol geo-engineering