Nodal Analysis Research Articles

Análise de fluxo de potência através de métodos numéricos

O Sistema Elétrico de Potência tem como função básica fornecer energia elétrica com qualidade e quando solicitada. Para que isso seja possível são necessárias algumas análises do sistema, dentre elas a Análise do Fluxo de Potência. Essa análise é importante para delineação dos sistemas de potência, assim como também, na definição das melhores condições de operação, controle e supervisão dos sistemas existentes. O sistema é modelado da seguinte forma: Geradores, Cargas, Reatores e Capacitores que são ligados entre um nó (barra) qualquer e o nó terra, já as linhas de transmissão e transformadores são ligadas entre dois nós quaisquer. Assim será gerada através de análise nodal a matriz de admitância do sistema, onde este problema é resolvido através de métodos numéricos. Um dos objetivos deste trabalho é a análise de fluxo de potência de um sistema com auxílio de métodos numéricos. Outro objetivo é verificar a exatidão dos resultados, com soluções obtidas pelos métodos de Eliminação de Gauss, Fatoração LU, Gauss Seidel e Método de Crout, implementados em linguagem C. A análise da exatidão dos resultados deu-se através do erro relativo em comparação com os resultados obtidos pelo software MatLab.

Convex relaxation of Sparse Tableau Formulation for the AC optimal power flow

Optimal power flow (OPF) approaches employing such methods as semi-definite programming (SDP) have garnered considerable interest in the literature of the last decade. The OPF formulations for these approaches have almost universally relied on Ybus admittance matrix representations, which derive from nodal analysis, and restrict allowable network elements to be voltage-controlled only. Limitations of nodal analysis long been recognized, and to overcome these, commercial power system software often employs modified nodal analysis (MNA). Here, we consider a novel general power system modeling approach based on multi-port representation of individual components with Sparse Tableau Formulation (STF) of network constraints, which is more versatile than MNA for OPF requiring many monitored links with constrained flows. In STF, one is better able to exploit the fact that the vast majority of power grid network elements have voltage-current behavior that is well-modeled as linear. This opens the door to simple, engineering-based convex relaxations. We discuss two relaxations, admittance-based and current-based. The tightness of the relaxation is shown to improve when angle constraints and narrow bounds for active power generation are provided. Sequential bound tightening and reduced spatial branch-and-bound are discussed to obtain stronger relaxation solution. We conduct case studies to show the effectiveness of our relaxations with standard test cases.

Distribution Network Power Loss Analysis Considering Uncertainties in Distributed Generations

Distribution network loss analysis is crucial for the economic operation in residential distribution networks. The increasing level of distributed generation (DG) has considerably improved the overall sustainability but raised the uncertainty in system losses and exacerbated voltage profiles. This paper presents a nodal distribution loss analysis approach in which the losses induced by loads and DGs are calculated recursively. In order to characterize the uncertainty, the Latin hypercube sampling (LHS)-based approach is presented for obtaining DG output samples. Further, the LHS-based sampling and loss analysis methods are combined into a proposed stochastic framework for loss analysis, which takes into account the DG output uncertainty. Case studies on a 36-bus radial distribution network verified the stochastic loss analysis method. Compared with the simple random sampling method, the proposed LHS-based stochastic loss analysis method can reach the same accuracy level for nodal voltages and losses more efficiently.

A Scaled Mesh/Nodal Formulation of Magnetic Equivalent Circuits With Motion

In this paper, the focus is on the efficient solution of magnetic equivalent circuits that include relative motion between components. It is shown that by combining the use of mesh and nodal analysis, one can avoid the need to restructure the circuit topology, which is a step encountered in strictly mesh-based approaches. In addition, one can overcome the poor convergence properties observed in strictly nodal-based formulations. A scaling of variables is introduced to ensure the condition that the number of the mixed mesh/nodal matrices remains relatively low. The proposed scaled model structure is then extended to magnetic equivalent circuits that are coupled to electrical systems for the analysis of dynamic performance. It is shown that the numerical properties of the coupled scaled model remain strong.

Nodal flexibility and kinematic indeterminacy analyses of symmetric tensegrity structures using orbits of nodes

A tensegrity structure may undergo large deformations under external loads, resulting in significant impact on its mechanical properties. Therefore, the nodal flexibility analysis of tensegrity structures, that is, analyzing the sensitivity of nodal displacements to external loads and the evaluation of critical nodes, is important in the structural design of tensegrities. Here, we present a numerical method for the symmetry-adapted flexibility analysis and kinematic indeterminacy of tensegrity structures using orbits of nodes and the Moore–Penrose inverse of involved matrices. To evaluate the contribution of each node to the total kinematic indeterminacy of a tensegrity structure, the distributed kinematic indeterminacies associated with the nodes of different orbits are independently computed. A flexibility ellipsoid is introduced to visually characterize the nodal flexibility of tensegrity structures. Several examples of tensegrities with different symmetries are presented to demonstrate the efficiency of the presented method. This method can be applied to the design and analysis of tensegrity structures under external loads, where flexibility ellipsoids are expected to be full and similar and each node is expected to have proper sensitivity to the external loads along different directions.

The significance of [18F] fluorodeoxyglucose-positron emission tomography/computed tomography in detection of pelvic nodal metastases in endometrial cancer

Objective This study was conducted to assess the accuracy of [18F] fluorodeoxyglucose-positron emission tomography/computed tomography (18FDG PET-CT) in detection of pelvic nodal metastases in endometrial cancer. Methods Patients with endometrial cancer from January 2015 to June 2017 confirmed by the postoperative pathology were retrospectively analyzed. 30 patients finished PET-CT before operation. The findings on histopathology were compared with 18FDG-PET/CT findings to calculate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 18FDG-PET/CT. To analyze the efficacy of maximum standardized uptake (SUVmax) and lymph node maximum standardized uptake (LN-SUVmax) of PET-CT in the diagnosis of pelvic lymph node metastasis. Results For detection of pelvic nodes, based on patient analysis, 18FDG-PET/CT had a sensitivity of 75.0%, specificity of 88.5%, PPV of 50.0%, NPV of 95.8% and accuracy of 86.7%. Based on a nodal region analysis, 18FDG-PET/CT had a sensitivity of 83.3%, specificity of 98.3%, PPV of 55.0%, NPV of 99.6%, and accuracy of 98.3%. When maximum standardized uptake values (SUVmax)>8, area under curve (AUC)=0.64, Yonden Index=0.42. When maximum standardized uptake values of lymphonodus (LN -SUVmax)>3 (AUC=0.79, Yonden Index=0.63), the sensitivity and specificity of diagnosis of lymph node metastasis were 100%, 42.31%, and 75.0%, 88.5%, but without statistically significant difference. Although AUC of LN-SUVmax was higher than SUVmax of primary lesion, but the difference was not statistically significant (P>0.05). Conclusions 18FDG-PET/CT has high specificity, NPV for detection of pelvic LN metastasis area in endometrial cancer, which can provide preoperative basis for patients with endometrial cancer to avoid lymph node resection, thereby reducing the risk of early endometrial cancer surgery and improving the quality of life after surgery.We concluded that, there were no exact cutoffs of SUVmax for the prediction of lymph node metastases, neither primary lesion, nor lymph node. There is clearly a need for multicenter, large-scale trials to find out better parameters in judging metastasis of lymphnodes. Key words: Fluorodeoxyglucose F18; Positron-emission tomography; Endometrial neoplasms; Lymphatic metastasis

Distributed Generation Placement in Port Harcourt Network using Nodal Analysis

Distributed Generation Placement in Port Harcourt Network using Nodal Analysis - written by Ajabuego O. G., Uzoechi L. O. published on 2019/01/17 download full article with reference data and citations

Pressure Transient Analysis of an Intersecting Rollover Faulted Crest Boundary in Niger Delta Oil Field

Pressure transient analysis has been extensively applied to detect anomalies in a reservoir system. These anomalies may be presented in the form of an intersection of the crestal and the antithetic fault associated with a growth fault. Interpretation of this fault can only be achieved through the use of pressure transient analysis. The objective of the research work is to analyze and test the faulted crest, depth of the anticline structure and examine the near well bore conditions in order to evaluate whether the well productivity is governed by wellbore effects (skin effects + well bore effect) or the reservoir at large. A case study of a well in the Niger delta is considered with a series of build up test carried out in two intervals of both upper and lower gauge readings. In this study, a computer aided design which uses a pressure derivative approach is used in this work to match the pressure derivative of an intersecting fault (angle) model to the field data, and the model assumes the characteristics of the reservoir. Based on the result of the interpreted data, simulation is done by using a non linear regression method (least square). The simulated data interpreted are achieved through the regression coefficient which provides a quantitative measure of the agreement between field data and the model. In conclusion, the best cases are taken from all the results and a nodal analysis is performed to diagnose the inflow performance of the well through the transient analysis in order to optimize the recovery of the oilfield.

Voltage Balancing for Bipolar DC Distribution Grids: A Power Flow Based Binary Integer Multi-Objective Optimization Approach

The re-emergence of two-phase bipolar dc distribution network, which utilizes the neutral wire for efficient distribution, has spurred research interest in recent years. In practice, system efficiency (power loss) and voltage unbalance are major concerns for the planning and design of the two-phase dc bipolar network. While most of the existing methodologies are power electronics solutions, there are very few works on resolving the problem from the power system perspective. This paper proposes a model-based optimization method by first formulating the power flow model for two-phase dc bipolar network using the single line modeling technique and nodal analysis. Second, a binary integer load distribution model is proposed to consider the re-distribution of unipolar loads across the two unipolar distribution poles. Together with the power flow model, the system power loss and system voltage unbalance indices are formulated as a binary integer quadratic model. Third, a multi-objective optimization model is formulated and solved using the weighted sum approach. The proposed method is applied to a dc LED lighting system design, which considers both voltage unbalance and power loss. Using a 15 bus single source and a 33 bus multi-source network as case studies, the developed power flow model is validated with very high accuracy. Compared to existing iterative methods, the proposed model-based approach is able to significantly improve the voltage balancing across the distribution system .

A Sparse Tableau Formulation for Node-Breaker Representations in Security-Constrained Optimal Power Flow

Realistic representations of contingencies in AC optimal power flow (ACOPF) often challenge traditional bus-branch network models. Derived from nodal analysis, such approaches represent network constraints in terms of the familiar bus admittance matrix, $Y_{\text{bus}}$ . A fixed $Y_{\text{bus}}$ is unable to represent common circuit breaker actions such as bus splitting. Work-arounds for $Y_{\text{bus}}$ -based analysis typically rely on topology processing, switching between different $Y_{\text{bus}}$ matrices depending on breaker settings. In this paper, we propose a very general node-breaker approach, employing multi-port element models and using a sparse tableau formulation (STF) for network constraints. Instead of treating breaker action as altering network topology, and hence changing the structure of Kirchhoff's voltage law (KVL) and Kirchhoff's current law (KCL) equations, this approach represents a breaker's position as impacting only constraints associated with a single component, thereby maintaining fixed structure in the KVL and KCL constraints. While larger numbers of variables are required, STF proves sparser than $Y_{\text{bus}}$ formulations. Numerical case studies herein demonstrate that STF provides computational efficiency comparable to a $Y_{\text{bus}}$ -based ACOPF at the scale of several hundred buses, and lower computational cost in an example of over one thousand buses.

A sand-production control system for gas production from clayey silt hydrate reservoirs

ABSTRACT Sand production is a crucial problem during the process of extracting natural gas from hydrate reservoirs. To deal with sand-production problems systematically, a sand-production control system (SCS) is first proposed in this paper, specialized for pore-distributed clayey silt hydrate reservoirs. Secondly, a nodal system analysis method (NSAM) is applied to analyze the sand migration process during hydrate exploitation. The SCS is divided into three sub-systems, according to different sand migration mechanisms, and three key scientific problems and advances in SCS research in China Geological Survey are reviewed and analyzed. The maximum formation sanding rate, proper sand-control gravel size, and borehole blockage risk position were provided for clayey hydrate exploitation wells based on the SCS analysis. The SCS sub-systems are closely connected via bilateral coupling, and coordination of the subsystems is the basis of maintaining formation stability and prolonging the gas production cycle. Therefore, contradictory mitigation measures between sand production and operational systems should be considered preferentially. Some novel and efficient hydrate exploitation methods are needed to completely solve the contradictions caused by sand production. © 2019 China Geology Editorial Office.

Enhanced Pathological Element-Based Symbolic Nodal Analysis

An improved symbolic analysis procedure to enhance the analytic efficiency of the reported symbolic nodal analysis is presented. Two techniques are adopted in the proposed method to reduce the order of the system of equations when performing symbolic analysis. The first one uses voltage signal sources directly to perform symbolic analysis without replacing them with their nullor equivalences. The second one uses the nullor, grounded mirror, and floating mirror elements to model the active devices that involve differential or multiple single-ended signals. Practical examples are given which demonstrate the feasibility of the proposed methods.

Waveform relaxation: a convergence criterion for differential-algebraic equations

While waveform relaxation (also known as dynamic iteration or co-simulation) methods are known to converge for coupled systems of ordinary differential equations (ODEs), they may suffer from instabilities for coupled differential-algebraic equations (DAEs). Several convergence criteria have been developed for index-1 DAEs. We present here a convergence criterion for a coupled system of an index-2 DAE with an ODE. The analysis is motivated by the wish to combine electromagnetic field simulation with circuit simulation in a stable manner. The spatially discretized Maxwell equations in vector potential formulation with Lorenz gauging represent an ODE system. A lumped circuit model via the established modified nodal analysis is known to be a DAE system of index ≤ 2. Finally, we present sufficient network topological criteria to the coupling that are easy to check and that guarantee convergence.

CUSUM charts in the quality control of colon cancer lymph node analysis: a population-registry study

BackgroundThe most important determinant of survival in patients with colon cancer is the presence or absence of regional lymph node metastases. This factor is consistently associated with long-term and disease-specific survival. Cumulative summation of differences (CUSUM) charts can help to discriminate abnormalities that cannot be explained by the general variability of a process. We used CUSUM charts to analyse the quality of nodal analysis in colon cancer and to use a population-registry cancer database to estimate the optimal number of lymph nodes for adequate prognostic analysis.MethodsThis was a multicentre population-registry cancer study from January 2004 to December 2007. We used these data to produce the different CUSUM curves, focusing on the main variables. To calculate survival, we used the Kaplan–Meier method.ResultsIn this study, we examined 548 patients. The CUSUM curves were calculated for overall mortality, specific mortality, and recurrence according to (1) the number of lymph nodes analysed and affected and (2) compared the ratio of the number of lymph nodes affected to the number analysed. Finally, the lymph node ratio was compared to the overall survival CUSUM curve.DiscussionThis CUSUM control chart analysis reinforces the unquestionable importance of analysing at least 12 lymph nodes in patients with colon cancer in order to accurately estimate their prognosis. However, our findings indicate that the analysis of at least 20 lymph nodes is a more appropriate cutoff point for accomplishing the demanding objective of diagnosing a high-quality prognosis in colon cancer patients.

Lean HC gas injection pilots analysis and IPR back calculation to examine the impact of asphaltene deposition on flow performance

Gas injection is one of the most economical and effective approach to improve oil recovery. However, outcome of such approach is contingent to reservoir heterogeneities impacting gas override and fingering. Furthermore, injected fluid composition and its compatibility with the reservoir fluid potentially impact flow assurance issues such as asphaltene precipitation into the wellbore and surface facilities.The objective of this paper is to examine the lesson learnt from a couple of field scale 5 spot patterned lean hydrocarbon gas injection pilots which were deployed in a heterogeneous carbonate formation of a giant field located offshore Abu Dhabi under secondary and tertiary drive mechanisms. Said pilots provides a valuable insight on production performance, pressure support, gravity override, fluid composition and evidence of asphaltene deposition that resulted in heavy production loss prior to the solvent treatment.This paper presents the overall pilot performance including pattern recovery, fluid front movement, potential role of heterogeneity in gas breakthrough timings and the operational events to witness asphaltene deposition affecting the flow performance. The deposited asphaltene cake thickness was measured mechanically during routine tubing clearance check operation that was helpful in estimating production loss due to altered production tubing flow opening. Also an integrated approach is applied to confirm the AOP laboratory measurements with the actual deposits of asphaltene that were found in to the production tubing.In order to confirm the effect of asphaltene deposition on inflow from near wellbore formation to the wellbore, a straightforward yet innovative nodal analysis approach was applied to study well performance using the calibrated and history matched well model. It was noticed that not only the outflow was altered because of asphaltene deposition into wellbore but also the inflow (productivity index) was seriously impacted potentially due to asphaltene deposition in near wellbore formation.

Low-levels of HBsAg quantification at 48-week in HBeAg-negative chronic hepatitis B patients are the advantageous population for HBsAg clearance

Objective: To analyze the therapeutic effect on HBeAg-negative chronic hepatitis B patients treated with Peg-IFNα-2a combined with NAs to obtain the influencing factors for predicting HBsAg clearance. Methods: A retrospective study was conducted to investigate the effect of pegylated interferon alpha-2a combined with nucleoside analogues (lamivudine/adefovir dipivoxil) on HBeAg-negative chronic hepatitis B. The treatment course was 96 weeks. Patients were followed up 120 weeks after the treatment. HBsAg clearance at 120 weeks was taken as the objective of the study. Logistic regression and receiver operating characteristic curve analysis screened the related factors affecting HBsAg clearance. χ (2) test was used to compare count data. Results: 111 patients were treated with pegylated interferon alpha-2a combined with nucleoside analogues, and 107 patients completed the scheduled course of treatment and follow-up. HBsAg clearance rate at120 week was 29.0% (31/107). The influencing factors for analysis were: (1) gender had no effect on HBsAg clearance rate; age and baseline levels of HBV DNA and alanine aminotransferase had no significant effect on HBsAg clearance; low baseline level of HBsAg (< 3.023 lgIU/ml) was beneficial to HBsAg clearance. The area under the working characteristic curve of the subjects was 0.746, the positive predictive value was 44.4%, and the negative predictive value was 86.8%. (2) HBsAg quantification or decline in 24 weeks and 48 weeks of treatment had a good predictive effect on HBsAg clearance, and the 48 weeks predicted value was higher than 24 weeks. When the HBsAg quantification was≤2.070 lgIU/ml at 48 weeks, the area under the receiver operating characteristic curve was 0.931, the positive predictive value was 52.8%, and the negative predictive value was 94.4%. When HBsAg decreased from baseline to≥0.991 lgIU/ml, the area under the receiver operating characteristic curve was 0.888, the positive predictive value was 50.8%, and the negative predictive value was 97.9%. (3) The analysis of HBsAg subgroup levels at 48 weeks suggested that the "interval analysis" can forecast HBsAg clearance more exactly than "nodal analysis" .The final HBsAg clearance rate of 100 IU/ml < HBsAg≤1 000 IU/ml, 10 IU/ml < HBsAg≤100 IU/ml and HBsAg≤10 IU/ml groups reached 6.7%, 31.8% and 67.7%, respectively. (4) The ALT abnormal group in the course of treatment obtained a higher HBsAg clearance rate (48.0%, 12/25). Conclusion: 96-weeks long-term treatment with pegylated interferon-alpha -alpha-2a combined with nucleoside analogues for HBeAg-negative chronic hepatitis B has a good predictive value for HBsAg clearance at baseline and during treatment. The "interval level" of HBsAg at 48-weeks is more accurate in predicting HBsAg clearance, suggesting that HBeAg-negative chronic hepatitis B patients with low HBsAg levels at 48-weeks are the advantageous populations with HBsAg clearance. These patients are worthy of prolonged treatment to pursue "clinical cure".

A rehomogenization-based approach to model spectral effects of local nuclide density changes in nodal calculations

In reactor core nodal analysis, the dependence of few-group, homogenized cross sections on the local physical conditions (i.e., the thermal-hydraulic state and material composition) is commonly represented via multivariate interpolation in parameterized libraries. In this paper, we propose a novel approach to model the spectral effects of changes in the moderator density and in the concentrations of diluted boron and xenon. This method is based on the spectral rehomogenization technique developed at Framatome and TU Delft to account for neighbor effects on the nodal cross sections. We compute on the fly the variation in the infinite-medium energy-collapsing spectrum from a nominal state to a perturbed condition (i.e., with different values of the aforementioned state parameters). The dependence of the microscopic and macroscopic cross sections on these three variables is thus resolved without the standard multidimensional interpolation. This strategy reduces substantially the computational burden of the lattice calculation, the cross-section library memory requirements, and the run time of the on-line cross-section reconstruction.The proposed approach is applied to a pressurized-water-reactor UO2 fuel assembly at zero burn-up, covering a wide range of the values of the water density and of the concentrations of boron and xenon. Both normal and abnormal operating conditions are considered. We show that, in most cases, cross-section changes are predicted with an accuracy comparable to that of traditional interpolation. Higher errors (but reasonably small compared to the range of accuracy of nodal computational tools) are only found at very low moderator densities, typical of accidental conditions. As further validation of the methodology, we simulate a heterogeneous multiassembly configuration. With this benchmark problem, we prove that the method can reconstruct the spectrum variation between the real environment in a perturbed state and the infinite lattice in the nominal one, thus modeling simultaneously the non-separable spectral effects of local physical conditions and internodal neutron leakage.

Optimal planning of battery systems for power losses reduction in distribution grids

The minimization of the power losses in the distribution grid is one of the main issue for the Distribution System Operator in order to reduce the management costs of the grid. The recent development of the battery technologies has introduced new possible applications for these systems within the radial distribution grid. In fact, batteries can be opportunely integrated in the grid and managed in order to reduce the power losses, and consequently increasing, for instance, the penetration of the renewable distributed generation and contributing to voltage regulation through reactive power production from battery inverter. In this context, one of the main research interest is the definition of the optimal siting and sizing of the energy storage solutions, considering a battery management capable to reduce network power losses and taking into account battery installation costs.Since network losses are expressed by means of quadratic function, an approach based on Mixed Integer Quadratically Constrained Quadratic Programming is proposed here to identify possible batteries optimal management strategies capable to minimize the power losses. Evaluation of the grid variables is obtained by the iterative Backward/Forward Sweep method implemented within the formulation of the optimization problem. The reactive power generated by the battery inverter is modeled as well by introducing quadratic constraints in order to further contribute in the network power losses reduction, taking into account the power factor limitation due to the inverter capability curve.An optimization procedure, called D-XEMS13, based on the formulation of the optimization problem, is implemented within a single loop optimization algorithm in order to identify the best size of the connected BESSs units, capable to maximize the reduction of the power losses in test grids. BESS optimal placement is also identified through a proposed approach based on a nodal sensitivity analysis of the network power losses. Validation of the proposed approach is then obtained by means of a cost/benefit comparison from energy point of view.Finally, the single loop optimization algorithm is further implemented on two test grids with optimal BESSs sizes and siting, assuming different capability curves for the BESS inverters. The results of simulations with the corresponding benefits are then presented and discussed.

Multiscale modeling of the coupled electromechanical behavior of multifunctional nanocomposites

In this first time effort, we developed a multiscale coupled electromechanical model capable of computing the piezoresistive properties of carbon nanotube (CNT)-reinforced composites. Monte-Carlo based algorithm was used to generate representative volume elements (RVEs) randomly filled with CNTs surrounded by the polymer matrix. The coupling between the applied mechanical load and the resulting electrical response was treated in a sequential manner in two steps. Firstly, a three-dimensional finite element model of the RVE was developed to determine the structural response of the nanocomposite system under different loading conditions. The results of the finite element model were then used to update the locations of the CNTs in the deformed RVE. Secondly, an electrical model based on the modified nodal analysis technique was developed to calculate the corresponding electrical conductivity of the nanocomposite. The developed model was successfully used to determine the piezoresistive behavior of CNT-epoxy composite under tension, compression, and shear loads. The results show that the composite gauge factor can reach up to 3.95 and is sensitive to the loading direction and CNT volume fraction. The predictions of the current model are in good agreement with the experimental findings of earlier studies, verifying its validity.

Model Helps Guide Choke-Management Strategies Under Constraints

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 187190, “Choke Management Under Wellbore, Completion, and Reservoir Constraints,” by Emmanouil Karantinos, SPE, and Mukul M. Sharma, SPE, The University of Texas at Austin, prepared for the 2017 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 9–11 October. The paper has not been peer reviewed. Choke-management strategies vary significantly among operators. No rigorous methodology exists for properly selecting choke sizes when constraints are placed on completions, wellbores, and fluid pressures and velocities. In this paper, the authors propose a coupled wellbore/reservoir model that performs dynamic nodal analysis using integrated models for surface-facilities, wellbore, and reservoir simulators and allows an operator to select choke sizes as a function of time. Introduction The suggested algorithm consists of three primary entities: the reservoir, the wellbore, and the completion. A reservoir simulator provides the rate as a function of drawdown or bottomhole pressure (BHP), and a wellbore model is used to calculate the frictional pressure loss along the wellbore and the surface flowlines. Depending on the fluid system, the appropriate choke-flow model is used. Dynamic (time-dependent) nodal analysis ensures the continuity of pressure and rates between the wellbore and reservoir entities at every timestep. The algorithm suggests the maximum available choke that satisfies, at all times, the entire set of user- specified constraints. The complete paper applies the method to two scenarios. The first is a high-permeability, vertical casedhole well in which screen erosion is a serious concern. For that particular case, the choke sizes should be adjusted to limit perforation velocities under the critical threshold of 10 ft/sec, which has been shown to cause screen erosion in high-permeability offshore wells. The authors show that choke sizing depends on various parameters, including the separator pressure, the well trajectory, and the true vertical depth. Finally, the method is applied to the design of a flowback operation in order to prevent proppant flowback and proppant crush-ing in a hydraulically fractured unconventional well. Design Considerations To mitigate the risk of productivity impairment or failures associated with the completion or other equipment, production engineers should take into consideration existing guidelines for allowable values of flow velocities or drawdown limits. These recommendations can be classified into three major categories: wellbore, completion, and reservoir constraints. Wellbore constraints include, but are not limited to, the maximum pressure drop across the choke to prevent hydrate or wax and asphaltene formation downstream of the choke, the maximum fluid velocity in the surface flowlines to prevent erosion, and the minimum fluid velocity along the wellbore trajectory to ensure effective proppant transport during flowback operations. Completion and reservoir constraints depend on the completion type in place. Table 1 of the complete paper presents several completion and reservoir constraints along with their maximum allowable values reported in the literature.