We devise a model predictive control algorithm for impulsive linear systems with autonomous flow dynamics and controlled jumps. Thereby the moments of jumps are not fixed, but rather considered as decision variables. ...
详细信息
We devise a model predictive control algorithm for impulsive linear systems with autonomous flow dynamics and controlled jumps. Thereby the moments of jumps are not fixed, but rather considered as decision variables. To this end, the complete system dynamics is formulated as a mixed-logical dynamical system after an appropriate discretization step. The resulting optimization problem contains both discrete and continuous decision variables, giving rise to a mixed-integerprogramming problem. The objective of the optimization is to steer the states into a target set. The stability is addressed through an appropriate cost function together with invariance conditions, as well as by introducing terminal constraints which are only enforced within a certain distance to the target set, thus, providing a trade-off between guaranteed convergence to the target set and computational complexity.
As inverter-based distributed energy resources (DERs) such as photovoltaic (PV) and battery energy storage system (BESS) penetrate within the distribution system. New challenges regarding how to utilize these devices ...
详细信息
As inverter-based distributed energy resources (DERs) such as photovoltaic (PV) and battery energy storage system (BESS) penetrate within the distribution system. New challenges regarding how to utilize these devices to improve power quality arises. Before, PV systems were required to disconnect from the grid during a large disturbance, but now smart inverters are required to have dynamically controlled functions that allows them to remain connected to the grid. Monitoring power flow at the point of common coupling is one of the many functions the controller should perform. Smart inverters can inject active power to pick up critical load or inject reactive power to regulate voltage within the electric grid. In this context, this thesis focuses on a high level and local control design that incorporates DERs. Different controllers are implemented to stabilize the microgrid in an Islanding and resiliency mode. The microgrid can be used as a resiliency source when the distribution is unavailable. An average model in the D-Q frame is calculated to analyze the inherent dynamics of the current controller for the point of common coupling (PCC). The space vector approach is applied to design the voltage and frequency controller. Secondly, using inverters for Volt/VAR control (VVC) can provide a faster response for voltage regulation than traditional voltage regulation devices. Another objective of this research is to demonstrate how smart inverters and capacitor banks in the system can be used to eliminate the voltage deviation. A mixed-integerquadratic problem (MIQP) is formulated to determine the amount of reactive power that should be injected or absorbed at the appropriate nodes by inverter. The Big M method is used to address the nonconvex problem. This contribution can be used by distribution operators to minimize the voltage deviation in the system.
We propose a method to select the subset of features in multiple linear regression models that considers the collinearity between features. The proposed method first detects collinear groups of features and then uses ...
详细信息
We propose a method to select the subset of features in multiple linear regression models that considers the collinearity between features. The proposed method first detects collinear groups of features and then uses collinear groupwise feature selection constraints to estimate the coefficients of the regression model. The constraints simultaneously control the number of features selected and predefined collinear feature groups. We manage the multicollinearity in the regression model by controlling the parameters of the fusion group constraint. To address the NP-hard problem of the proposed method, we propose a modified discrete first-order algorithm. We use simulation and real-world data to demonstrate the usefulness of the proposed method by comparing it to existing regularization and discrete optimization-based methods in terms of predictive accuracy, bias, and variance. The comparison confirms that the proposed method outperforms the alternatives. (C) 2018 Elsevier Ltd. All rights reserved.
High-precision motion industrial systems must satisfy tight performance requirements. Both positioning accuracy and throughput demands are typically achieved through improvements in hardware, thereby raising the bill ...
详细信息
High-precision motion industrial systems must satisfy tight performance requirements. Both positioning accuracy and throughput demands are typically achieved through improvements in hardware, thereby raising the bill of materials. A cost saving alternative could be to strive for a reduction in the hardware components needed, in combination with advanced motion control, to still meet the desired specifications. Particularly, in this paper, the possibility is analyzed to allow for resource sharing among several actuators. This results in a switched system, for which we develop a real-time MPC algorithm for optimization of both the input and the switching signals. This implementation applies to a fairly general class of nonlinear systems and uses a novel offset-free formulation in velocity form for LTV prediction models, to realize good tracking performance under the resource sharing constraints. We provide a proof of concept for this MPC solution on a high fidelity model of an industrial SCARA robot, where it is proposed to use a single amplifier to serve two actuators. The MPC solution is compared to heuristically switched LTI controllers, and the potential of the proposed approach is shown in simulations. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
We consider in this paper a class of semicontinuous quadraticprogramming problems, which arises in many real-world applications such as production planning, portfolio selection, and subset selection in regression. We...
详细信息
We consider in this paper a class of semicontinuous quadraticprogramming problems, which arises in many real-world applications such as production planning, portfolio selection, and subset selection in regression. We build upon the idea of the quadratic convex reformulation approach, i.e., adding to the original objective function an additional convex term that is zero at all points of the feasible region. Exploiting the structure of semicontinuous variables, we derive the most general set of quadratic functions that can be added. We also incorporate the state-of-the-art perspective reformulation into our new framework. Within this framework, the set of optimal reformulations with the tightest continuous relaxation can be found by solving a semidefinite programming problem. We also explore the relationship among different reformulations within our framework and simplify the search for optimal ones in certain cases with the help of second-order cone programming. Among the proposed set of optimal reformulations, we can choose one with or without the perspective component. If the perspective component is present, the new reformulation can be solved by the perspective cut algorithm in the literature. If the perspective component is not present, the new reformulation is a standard mixed-integer quadratic programming (MIQP) problem and can be plugged into and solved by any MIQP solvers. Our preliminary numerical tests in both portfolio selection and subset selection problems have demonstrated the effectiveness of our new reformulations, and the comparison results indicate that the performance of the new reformulation without the perspective component, when solved in general MIQP solvers, is competitive to the perspective cut approach.
In this paper we study the effect of a decision maker's risk attitude on the median and center problems, two well-known location problems, with uncertain demand in the mean-variance framework. We provide a mathema...
详细信息
In this paper we study the effect of a decision maker's risk attitude on the median and center problems, two well-known location problems, with uncertain demand in the mean-variance framework. We provide a mathematical programming formulation for both problems in the form of quadraticprogramming and develop solution procedures. In particular, we consider the vertex and absolute median problems separately, and identify a dominant set for the center problem. Glover's linearization method is applied to solve the vertex median problem. We also develop a branch and bound algorithm and a heuristic as the linearization technique takes too long for the vertex median problem on large networks. A computational experiment is conducted to compare the performance of the algorithms. We demonstrate the importance of taking into account the volatility and correlation structure when a location decision is made. The closest assignment property is also discussed for these location problems under the mean-variance objective. (C) 2016 Elsevier Ltd. All rights reserved.
This paper is on the problem of short-term hydro, scheduling, particularly concerning head-dependent cascaded hydro systems. We propose a novel mixed-integer quadratic programming approach, considering not only head-d...
详细信息
This paper is on the problem of short-term hydro, scheduling, particularly concerning head-dependent cascaded hydro systems. We propose a novel mixed-integer quadratic programming approach, considering not only head-dependency, but also discontinuous operating regions and discharge ramping constraints. Thus, an enhanced short-term hydro scheduling is provided due to the more realistic modeling presented in this paper. Numerical results from two case studies, based on Portuguese cascaded hydro systems, illustrate the proficiency of the proposed approach. (C) 2009 Elsevier Ltd. All rights reserved.
A recent series of papers has examined the extension of disjunctive-programming techniques to mixed-integer second-order-cone programming. For example, it has been shown-by several authors using different techniques-t...
详细信息
A recent series of papers has examined the extension of disjunctive-programming techniques to mixed-integer second-order-cone programming. For example, it has been shown-by several authors using different techniques-that the convex hull of the intersection of an ellipsoid, , and a split disjunction, with , equals the intersection of with an additional second-order-cone representable (SOCr) set. In this paper, we study more general intersections of the form and , where is a SOCr cone, is a nonconvex cone defined by a single homogeneous quadratic, and H is an affine hyperplane. Under several easy-to-verify conditions, we derive simple, computable convex relaxations and , where is a SOCr cone. Under further conditions, we prove that these two sets capture precisely the corresponding conic/convex hulls. Our approach unifies and extends previous results, and we illustrate its applicability and generality with many examples.
This paper treats the problem of position formation flight control of a group of three multirotor aerial vehicles under obstacle and collision avoidance constraints. In order to solve the problem, a distributed archit...
详细信息
This paper treats the problem of position formation flight control of a group of three multirotor aerial vehicles under obstacle and collision avoidance constraints. In order to solve the problem, a distributed architecture with model predictive controllers for each vehicle includes a set of convex constraints on the vehicles's position to prevent collisions with other vehicles and obstacles. The resulting distributed scheme controls the formation based on a virtual structure approach where the computers of the architecture exchange position data through diagrams in Simulink. The performance of the method is assessed through simulations considering that the vehicles are subject to disturbance forces and the results show the effectiveness and the ability of the control architecture to handle the obstacle and collision avoidance constraints.
Stiction is a nonlinear friction phenomenon that causes poor performance of control loops in the process industries. In this work, we develop a mixed-integer MPC (Model Predictive Control) formulation including valve ...
详细信息
ISBN:
(纸本)9780993244049
Stiction is a nonlinear friction phenomenon that causes poor performance of control loops in the process industries. In this work, we develop a mixed-integer MPC (Model Predictive Control) formulation including valve dynamics for a sticky valve in order to improve control loop performance. The introduction of the valve nonlinearity into the model prevents the MPC from requesting physically unrealistic control actions due to valve stiction. Simulation studies using a two-tank systems show that, if the deadband value is known a priori, the mixed-integer quadratic programming (MIQP) can effectively improve the closed-loop performance in the presence of valve stiction.
暂无评论