The Interconnection and Damping Assignment Passivity-Based Control (IDAPBC) is applied phase-independently to the Modular Multilevel Converter (MMC) in order to overcome "dqo"-based control problems. In addition, an equilibrium point estimator is proposed to determine the time-varying equilibrium state of the MMC needed as input for the non-linear controller. This control strategy provides global robust stabilization of the MMC against variations on both its AC and DC sides. The control + estimator strategy combines both the state-space and energy dynamics models of the MMC.

Abstract Mitigation measures to protect marine mammals from sound emissions can be implemented more effectively if the sound output of a seismic source is known beforehand. We present a forward modelling workflow to assess the environmental impact of seismic exploration in areas with marine mammal activity at the survey planning stage. The focus is on modeling the output sound exposure level created by the seismic source, typically an airgun array. The employed physical model considers the hydrodynamics of marine airguns, including air bubble oscillations, near-source interactions with other airguns in array-configurations as well as interaction with, and impact of, the surface ghost reflection. Sound pressure and/or sound exposure levels can be obtained as a function of distance from the source through consideration of different geometrical spreading models and a hearing threshold term for different marine mammal species. Combined, these results allow for the estimation of sound output and propagation properties in a number of different scenarios, in line with most recent regulatory requirements. The presented model allows an accurate estimation of sound output of seismic sources up to about 1 kHz, which marks on average the frequency at which airgun sources have decayed by 50 dB from their respective spectral maximum. We present example modeling results that illustrate how the workflow can be employed for the planning of specific mitigation measures, such as exclusion zones, safety radii, and soft-start procedures.

Abstract ExxonMobil and Imperial Oil Resources (Imperial) are conducting a Solvent Assisted - Steam Assisted Gravity Drainage (SA-SAGD) experimental pilot at Cold Lake in the Clearwater formation where up to 20% by volume of hydrocarbon solvent (diluent) has been injected along with dry steam in a dual horizontal well SAGD configuration. Experimental work performed by the Alberta Research Council (ARC) (Nasr, 2003) and Imperial indicated that addition of solvent to steam increases bitumen rates and decreases steam-oil ratios relative to the conventional SAGD process. The main objective of this pilot has been to produce high quality field data to definitively support these experimental conclusions. The pilot scope includes two horizontal well pairs (four wells), six observation wells, associated steam and diluent injection facilities, artificial lift, as well as, dedicated production measurement and testing facilities. The SA-SAGD pilot uses existing steam generation, water treatment, bitumen separation and processing facilities at Imperial's Mahkeses plant and existing steam distribution and production gathering systems. The main focus of this paper is to document the integrated approach taken to ensure that this multi-year pilot is successful and to provide information resulting from this multi-year pilot. Key surveillance products, such as, production/injection measurements, horizontal-well temperature logs, observation-well temperature and saturation logs, time-lapse 3D seismic, and the impact of a mid-pilot solvent switch will be discussed. In addition, this paper will review how these surveillance products are integrated with laboratory data and simulation efforts to improve our understanding of this process and increase confidence in go-forward predictions. Given the emerging importance of solvent-assisted thermal heavy-oil processes and the accelerated conversion of this technology from laboratory-scale to field-scale, data from a field pilot provides invaluable information in the quest to deploy this emerging in-situ recovery technology.

The main objective of this work is to study, characterize finely the defects created in photovoltaic cells made from mono crystalline silicon wafer based on semiconductor has continued its operation under extreme conditions (electrical stress). We will demonstrate the effect of reverse stress current injected in solar cell structure on the I-V and C-V characteristics under dark conditions at room temperature for several time periods. These experimental measurements were numerical analyzed using double exponential model.Experimental evidence showed that different levels of reverse currents are confirmed to be a major degrading factor affecting the performance, efficiency, and power of solar modules. The experimental results were consistent with computational predictions.

In this paper, buck converters with input filter are modeled using the Euler Lagrange formalism and then build a PBC (passivity based controller). The model is validated, by comparing its response with those of two switched circuits: symmetric and asymmetric. In the former, both switches are realized by MOSFETS while in the second one of them is realized by a diode. It is then showed by simulation and, explained with energy-based arguments why the obtained model thoroughly represents only the symmetric circuit. The model is then used to build a passivity-based control law. As this control law assumes the stability of the zero dynamic, conditions under which this hypothesis is satisfied, are first given. It is shown by simulation with switched circuits the robustness of the proposed controller against load variations. Then, a prediction of the source variations is included in the controller in order to render it robust against source variations.

In a recent paper a procedure to design globally asymptotically stabilizing linear proportional plus integral controllers for switched power converters was proposed. The construction requires the measurement of the full state of the system, which is often unavailable in practice. In this note we identify a class of converters for which an asymptotically convergent reduced order observer, preserving the aforementioned stability property of the closed-loop, can be designed. The class is characterized by a simple linear matrix inequality. The new controller is illustrated with the widely-popular, and difficult to control, single-ended primary inductor converter, for which simulation and experimental results are presented.

We present a workflow to assess the risk of excessive sound exposure on marine mammals based on forward modelling of the far-field signatures from airgun arrays. The employed physical model takes into account the hydrodynamic effects around an airgun including the air bubble, directivity effects of realistic airgun arrays, and the interaction of the primary signals with the surface ghost reflection. Based on such signatures, we are calculating sound pressure and sound exposure levels as a function of distance and direction from the source, taking into account different geometrical spreading models. We also consider the frequency-dependent hearing threshold for different cetacean species. The workflow allows the estimation of a variety of different properties and scenarios in line with most recent regulatory requirements. Results can be used as a base for the planning of mitigation measures, such as exclusion radii around sensitive areas and soft-start procedures.

Alex Goertz, Jens Fredrik Wisløff, Francis Drossaert and Jaafar Ali discuss how modelling the source output of marine airgun arrays can be used for planning marine mammal mitigation measures as part of marine seismic survey design and environmental permitting.

Abstract ExxonMobil and Imperial Oil Resources (IOR) are conducting a Solvent Assisted - Steam Assisted Gravity Drainage (SA - SAGD) experimental pilot at Cold Lake in the Clearwater formation. In this SA-SAGD pilot, up to 20% by volume of a hydrocarbon solvent (diluent) has been injected along with dry steam in a dual horizontal well SAGD configuration. The primary objective of the pilot was to quantify the impact of solvent addition on bitumen production and steam-oil ratio (SOR). Key surveillance data collected during the pilot include production/injection rates (oil, water, and solvent), production/injection pressures, horizontal well temperatures, observation well temperatures, saturation logs, and time-lapse 3D seismic surveys. The objective of this paper is to discuss the modeling efforts that were completed in order to interpret the initial results of the pilot. Specifically, this paper will address (1) the construction of a detailed 3D geologic model and the corresponding flow simulation model and (2) the history-matching results. The geologic model incorporates information from 3D seismic surveys as well as core and log data from the pilot observation wells. Using the geologic model and the field production data, the SA-SAGD process was modeled using a thermal simulator. An acceptable match to the total hydrocarbon production rate, injection pressure, and SOR was achieved through a minor adjustment to the model permeability. The completed simulation studies are invaluable in increasing our understanding of the key parameters that control flow behavior in the SA-SAGD process. Ultimately, these learnings will be used by ExxonMobil and Imperial Oil Resources to optimize the process and make decisions related to full-field commercial deployment of the SA-SAGD recovery process.

This paper presents the application of predictive deadbeat control to the high switching frequency DC/DC Single-Ended Primary Inductor Converter (SEPIC). An extended Kalman observer with load variation estimation is designed to achieve current sensorless operation of the controller. A hybrid Delta-Sigma (Δ-Σ) Digital Pulse Width Modulation (DPWM) is used to effectively achieve 11-bit resolution at high-frequency and reduce the system clock frequency. The proposed DPWM along with the predictive deadbeat control algorithm is validated by using a Virtex-II FPGA. Experimental studies are conducted for a laboratory prototype with switching frequency of 500kHz. Simulation and experimental results prove the performance of the proposed solution.

In a recent paper a procedure to design globally asymptotically stable linear proportional plus integral controllers for switched power converters was proposed. The construction requires the measurement of the full state of the system, which is often unavailable in practice. In this note we identify a class of converters for which an asymptotically convergent reduced order observer, preserving the aforementioned stability property of the closed-loop, can be designed. The class is characterized by a simple linear matrix inequality. The new controller is illustrated with the widely-popular, and difficult to control, single-ended primary inductor converter, for which experimental results are presented.

This paper presents the application of fixed frequency (or indirect) Sliding Mode Control (SMC) to the DC-DC Single-Ended Primary Inductor Converter (SEPIC) where the switching frequency is in the range of hundreds of kHz and consequently a FPGA is required. Due to the constraint of EPGA, only the output voltage is measured. As the proposed SMC requires the knowledge of all the states, an extended Kalman observer is introduced to estimate the state vector and the load variation. A multi-bit second-order Δ-Σ modulator is used to effectively achieve 11-bit resolution at high-frequency through only a 8-bit hardware Core Digital Pulse Width -Modulator (DPWM). Simulation and experimental studies are conducted for a laboratory prototype with switching frequency of 500 kHz. Results proved the performance of the proposed solution.

Abstract ExxonMobil and its affiliate Imperial Oil Resources are currently operating a Solvent-Assisted Steam-Assisted Gravity Drainage (SA-SAGD) experimental pilot plant at Cold Lake, Canada. During pilot operation, up to 20 percent by volume of a light hydrocarbon solvent will be injected with dry steam in a dual horizontal well SAGD configuration. The pilot scope consists of two horizontal well pairs (four wells total), six observation wells, associated steam and solvent injection facilities, artificial lift, and dedicated production measurement and testing facilities. Previous experimental and computer modeling work completed by the Alberta Research Council (ARC) (Nasr, 2003), Imperial Oil Resources, and ExxonMobil indicates that the addition of solvent to the dry steam increases bitumen production rates and decreases the steam oil ratio (SOR) relative to conventional SAGD processes. A key objective of this pilot is to safely collect high-quality field data to support these findings and quantify process improvement. This paper will focus on the pilot design approach taken to ensure that the multi-year pilot is successful as well as highlight early pilot performance and operation. Specific design aspects which will be discussed include the choice for the pilot location, the use of detailed geologic models to design and place the horizontal wells, and solvent measurements. Early field results are consistent with expectations. However, longer term operation is required to make a more quantitative assessment. In addition, the pilot operation has demonstrated excellent control of injection pressure, which is critical to the application of this technology in settings with bottom water or top gas.