Browsing by Author "Garces A."

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An Exact Feedback Linearization Control of a SMES System to Support Power in Electrical Grids
(Institute of Electrical and Electronics Engineers Inc., 2018) Montoya O.D.; Garrido Arévalo, Víctor Manuel; Gil-González W.; Holguín E.; Garces A.
This paper presents an exact feedback linearization control strategy to operate superconducting magnetic energy storage (SMES) systems connected to an electric distribution network through a pulse-width-modulated current source converter (PWM-CSC). To model this system an average model is employed by using dq reference frame. The dynamical model of the SMES system considering the PWM-CSC is transformed algebraically into an equivalent linear model by simple substitutions, avoiding to use an equivalent linearization technique or Taylor's series. The linear model preserves all features of the nonlinear model, which allows obtaining control laws to be applicable in its non- linear system. The proposed control scheme permits the active and reactive control of the SMES system in a wide range of operating independently. The effectiveness and the robustness of the proposed control methodology are tested in a low-voltage distribution network considering unbalance and high harmonic distortion in the voltage provided by the utility. All simulation cases are carried out in MATLAB/ODE environment under time domain reference frame, and they are compared with a conventional PI controller. © 2018 IEEE.
Control for EESS in Three-Phase Microgrids under Time-Domain Reference Frame via PBC Theory
(Institute of Electrical and Electronics Engineers Inc., 2019) Montoya O.D.; Gil-González W.; Garces A.
This brief presents a general form of designing passivity-based controllers for electrical energy storage systems (EESS) in three-phase microgrids (TP-MGs) under time-domain reference frame. The control strategy proposed in this brief use the Clark's transformation known as αβ reference frame, avoiding to use phase-locked loop systems, which allows improving the dynamical performance in the energy storage devices. Passivity-based control guarantees stable operating conditions in the sense of Lyapunov for each EESS for different grid operation scenarios in the TP-MG. The design of the controllers is made by using passivity-based control (PBC) theory in conjunction to the dynamics of the error approach. A comparison to classical proportional-integral control method is used to show the applicability of the PBC approach presented in this brief. Simulation results are conducted via MATLAB/Simulink software. © 2004-2012 IEEE.
Control of a SMES for mitigating subsynchronous oscillations in power systems: A PBC-PI approach
(Elsevier Ltd, 2018) Gil-González W.; Montoya O.D.; Garces A.
This paper proposes a methodology to control the active and reactive power of a superconducting magnetic energy storage (SMES) system to alleviate subsynchronous oscillations (SSO) in power systems with series compensated transmission lines. Primary frequency and voltage control are employed to calculate the active and reactive power reference values for the SMES system, and these gains are calculated with a particle swarm optimization (PSO) algorithm. The proposed methodology is assessed with a classical PI controller, feedback linearization (FL) controller and a passivity-based PI control (PI-PBC). Operating limits for VSC are also considered, which gives priority to active power over reactive power. The IEEE Second Benchmark model is employed to demonstrate the assessment of the proposed methodology where PI-PBC presents better performance than the classical PI and FL controllers in all the operating conditions considered. © 2018 Elsevier Ltd
Controller design for VSCs in distributed generation applications: An IDA-PBC approach
(Institute of Electrical and Electronics Engineers Inc., 2019) Montoya O.D.; Garrido Arévalo, Víctor Manuel; Gil-González, Walter; Garces A.; Grisales-Noreña L.F.
This paper presents an asymptotically stable global controller design for distributed energy integration in electrical distribution networks using a three-phase voltage source converter (VSC). An invariant Park's transformation is used to obtain the mathematical representation of the VSC in dq0 reference frame. To design of the proposed controller, interconection and damping assignment passivity-based control (IDA-PBC) theory is applied via a Hamiltonian representation for the open-loop dynamic as well as the desired closed-loop dynamic of the system. The control law obtained allows guaranteeing asymptotic stability properties in the sense of Lyapunov for closed-loop operation. To verify the robustness and effectiveness of the proposed controller a classic connection of a distributed generator with a VSC converter using an ideal voltage source in its DC side is employed. Simulation results show the capability of the proposed controller to support active and reactive power independently under unbalance voltage conditions and harmonic distortion as well as the possibility of using the VSC as a dynamic power factor corrector. Additionally, all simulation scenarios are compared to classic PI controllers to show the good dynamic performance of the proposed controller using IDA-PBC theory. MATLAB/SIMULINK software is employed as simulation environment. © 2018 IEEE.
Current PI Control for PV Systems in DC Microgrids: A PBC Design
(Institute of Electrical and Electronics Engineers Inc., 2019) Gil-González, Walter; Garces A.; Montoya O.D.
This paper proposes a passive PI control for applications of photovoltaic (PV) systems integrated with boost DC-DC converters. The proposed controller guarantees asymptotically stability in closed-loop for the boost DC-DC converter using Lyapunov theory. In addition, the proposed controller is robust to parametric uncertainties and unmodeled dynamics since it does not depend on the system parameters. The current control mode is selected for the PV system since it is modeled as a current source, where its current is computed as a function of solar irradiance and the cells temperature. The current reference is calculated to a perturbing and observe MPPT algorithm with a current-mode controlled to extract the maximum power available in this solar source. The PI-PBC applied to the boost DC-DC converter is compared with a classical PI approach for validating its effectiveness and the robustness. Simulation results are performed in MATLAB/Simulink with a switching frequency of 5 kHz. © 2019 IEEE.
Direct power control for VSC-HVDC systems: An application of the global tracking passivity-based PI approach
(Elsevier Ltd, 2019) Gil-González W.; Montoya O.D.; Garces A.
This paper proposes a direct power control (DPC) for a high-voltage direct-current system using voltage source converters (VSC-HVDC) by applying passivity-based control theory. This system allows doing an efficient and reliable integration of electrical network from renewable energy sources. The DPC model permits instantaneous control of the active and reactive power without employing the conventional inner-loop current regulator and the phase-locked loop, thus diminishing investment costs and increasing the reliability of the system. The proportional-integral passivity-based control (PI-PBC) is chosen to control the direct power model of the VSC-HVDC system since this system exhibits a port-Hamiltonian formulation in open-loop and as PI-PBC can exploit this formulation to design a PI controller, which guarantees asymptotically stable in closed-loop based on Lyapunov's theory. Passivity-based control is an active research subject in the control community which has gained a reputation of being a very theoretical subject. Nevertheless, it can have advantages from a practical point of view including an implementation similar to the conventional controls for power systems applications. The paper is oriented to the power & energy systems community, taking into account this practical approach. The proposed controller is assessed by simulations in a two-terminal VSC-HVDC system and compared with a PI direct power controller. Four simulation conditions using MATLAB/SIMULINK were conducted to verify the effectiveness of PI-PBC against a PI controller and a perturbation observer-based adaptive passive control under various operating conditions. © 2019 Elsevier Ltd
Direct power control of electrical energy storage systems: A passivity-based PI approach
(Elsevier Ltd, 2019) Gil-González, Walter; Montoya O.D.; Garces A.
This paper proposes a direct power control for electrical energy storage systems (EESS) in ac microgrids. This strategy allows managing instantaneous active and reactive power without using a conventional inner-loop current regulator and without a phase-locked loop, increasing the reliability of the system while reducing investment costs. PI passivity-based control (PI-PBC) is selected to control the direct power model of EESS. This is because their models exhibit a port-Hamiltonian formulation in open-loop, and PI-PBC exploits this formulation to design a PI controller, which guarantees global asymptotically stability in closed-loop in the sense of Lyapunov. Simulations tested the proposed model in a microgrid and compared with conventional vector oriented controls in a dq reference frame and a direct power model controlled via feedback linearization (FL). PI-PBC has a better performance than other two controllers in all considered scenarios. Simulation results have conducted through MATLAB/SIMULINK software by using the SimPowerSystem toolbox. © 2019 Elsevier B.V.
Distributed energy resources integration in single-phase microgrids: An application of IDA-PBC and PI-PBC approaches
(Elsevier Ltd, 2019) Montoya O.D.; Gil-González W.; Garces A.
This paper presents a unified Hamiltonian formulation for controlling distributed energy resources (DERs)in ac single-phase microgrids (SP-MGs)via proportional-integral passivity-based control (PI-PBC), and interconnection and damping assignment passivity-based control (IDA-PBC). The proposed Hamiltonian formulation allows us to consider both pulse-width modulated voltage source converters (PWM-VSC)and pulse-width modulated current source converters (PWM-CSC)under a unified model. Renewable generation and supercapacitor energy storage systems are integrated via PWM-VSC technologies, while superconducting coils are integrated through PWM-CSC technologies. IDA-PBC and PI-PBC theories enable us to design control strategies begin that consider Lyapunov's stability theory combined with the well-known advantages of proportional and integral control actions. Our simulation's results corroborate the applicability of the proposed control approaches under stability paradigm. MATLAB/Simulink is employed for computational implementations via begin the SimPowerSystems toolbox. © 2019 Elsevier Ltd
Economic dispatch of energy storage systems in dc microgrids employing a semidefinite programming model
(Elsevier Ltd, 2019) Gil-González W.; Montoya O.D.; Holguín E.; Garces A.; Grisales-Noreña L.F.
A mathematical optimization approach for the optimal operation focused on the economic dispatch for dc microgrid with high penetration of distributed generators and energy storage systems (ESS) via semidefinite programming (SDP) is proposed in this paper. The SDP allows transforming the nonlinear and non-convex characteristics of the economic dispatch problem into a convex approximation which is easy for implementation in specialized software, i.e., CVX. The proposed mathematical approach contemplates the efficient operation of a dc microgrid over a period of time with variable energy purchase prices, which makes it a practical methodology to apply in real-time operating conditions. A nonlinear autoregressive exogenous (NARX) model is employed for training an artificial neural network (ANN) for forecasting solar radiation and wind speed for renewable generation integration and dispatch considering periods of prediction of 0.5 h. Four scenarios are proposed to analyze the inclusion of ESS in a dc microgrid for economic dispatch studies. Additionally, the results are compared with GAMS commercial optimization package, which allows validating the accuracy and quality of the proposed optimizing methodology. © 2018 Elsevier Ltd
Group-Theory for the Analysis of Heuristic Algorithms in Power Distribution Systems
(Institute of Electrical and Electronics Engineers Inc., 2018) Garces A.; Gil-González, Walter; Castano J.; Montoya O.D.
This paper applies group theory to four classic problems in power distribution systems, namely: phase balancing, primary feeder reconfiguration, optimal tap setting of voltage regulator transformers and optimal placement of fixed capacitors. The main focus of the paper is in the codification and the use of groups as a tool for analysis. A simple random search algorithm is used as a test for the first problem. It is demonstrated that the groups formalism allows a simple analysis of heuristics and could be an interesting path for future investigations. © 2018 IEEE.
Integration of PV Arrays in DC Power Grids via Unidirectional Boost Converters: A PBC Approach
(Institute of Electrical and Electronics Engineers Inc., 2018) Montoya O.D.; Campillo Jiménez, Javier Eduardo; Gil-González W.; Garces A.
This paper presents a general control design for photovoltaic systems integrated with Direct-Current power grids by using an unidirectional boost converter. Passivity-based control (PBC) theory is used as a control technique since the dynamical model of the boost converter has an intrinsically port-Hamiltonian structure, where PBC theory is based upon, to design stable controllers via Lyapunov stability theory. To control the photovoltaic solar system, a current control mode is used, since photovoltaic cells are mathematically modelled as current sources, where the photo-current determined by the solar irradiance and the cell's temperature. Proportional and proportional-integral passivity-based controllers are developed to operate the boost converter under current control mode to extract the maximum power available in the PV array. Simulation results are conducted via MATLAB/ODE-package software. © 2018 IEEE.
Linear power flow formulation for low-voltage DC power grids
(Elsevier Ltd, 2018) Montoya O.D.; Grisales-Noreña L.F.; González-Montoya D.; Ramos-Paja C.A.; Garces A.
This paper presents a reformulation of the power flow problem in low-voltage dc (LVDC) power grids via Taylor's series expansion. The solution of the original nonlinear quadratic model is achieved with this proposed formulation with minimal error when the dc network has a well defined operative conditions. The proposed approach provides an explicit solution of the power flow equations system, which avoids the use of iterative methods. Such a characteristic enables to provide accurate results with very short processing times when real operating scenarios of dc power grids are analyzed. Simulation results verify the precision and speed of the proposed method in comparison to classical numerical methods for both radial and mesh configurations. Those simulations were performed using C++ and MATLAB, which are programming environments commonly adopted to solve power flows. © 2018 Elsevier B.V.
Modeling and control of a small hydro-power plant for a DC microgrid
(Elsevier Ltd, 2020) Gil-González W.; Montoya O.D.; Garces A.
This paper presents the modeling and control of a small hydro-power plant (SHP) for a DC microgrid based on passivity theory. The SHP is made up of a turbine, a permanent magnet synchronous generator (PMSG), a voltage source converter and a DC microgrid. The electrical, mechanical and hydraulic dynamics in the mathematical model of the SHP are considered. We employ a nonlinear controller based on passivity, whose stability is guaranteed under practically reasonable assumptions. Our simulation results show better performance of the proposed controller when compared with a PI controller in all of the scenarios that were considered. © 2019 Elsevier B.V.
Optimal conductor size selection in radial distribution networks using a mixed-integer non-linear programming formulation
(IEEE Computer Society, 2018) Montoya O.D.; Garces A.; Castro C.A.
In this paper a mixed-integer non-linear programming formulation for optimal conductor selection in radial distribution networks is proposed. The objective function in this problem corresponds to the minimization of power losses and costs of investment in conductors. A typical set of constraints corresponding to the operative conditions in distribution systems, as power flow balance, voltage regulation, thermal capacity and telescopic conductors distribution, among others, are employed. Three different demand scenarios are considered to evaluate their impacts in the final conductor selection. The proposed mathematical model is solved using the general algebraic modeling system (GAMS) and DICOPT solver. Two radial distribution networks with 8 and 27 nodes, respectively, are employed to verify the general performance of the mathematical model proposed. © 2003-2012 IEEE.
Optimal Location of DGs in DC Power Grids Using a MINLP Model Implemented in GAMS
(Institute of Electrical and Electronics Engineers Inc., 2018) Montoya O.D.; Garrido Arévalo, Víctor Manuel; Grisales-Noreña L.F.; Gil-González W.; Garces A.; Ramos-Paja C.A.
This paper addresses the problem of optimal location and sizing of distributed generators (DGs) in direct-current (dc) power grids by using a mixed-integer nonlinear programming (MINLP) formulation. The reduction of the power losses in all branches of the network are considered as the objective function; while the restrictions are the power balance, voltage regulation, maximum penetration and maximum distributed generation units available. The general algebraic modeling system (GAMS) is selected as nonlinear optimizing package to solve this problem; besides, a small numerical example of energy production is introduced to illustrate the usability of using GAMS. Finally, a 21-node dc grid with two ideal generators, and multiple constant power loads, is used as test system. © 2018 IEEE.
Optimal Power Flow on DC Microgrids: A Quadratic Convex Approximation
(Institute of Electrical and Electronics Engineers Inc., 2019) Montoya O.D.; Gil-González, Walter; Garces A.
This express brief shows a convex quadratic approximation for the optimal power flow (OPF) in direct-current microgrids (dc-μ Grid) via Taylor's series expansion. This approach can be used for solving OPF problems on radial and meshed dc-μ Grids with multiple constant power terminals, allowing to cover a wide range of configurations. Two test dc-μ Grids with 10 and 21 nodes were used to validate the proposed model. Nonlinear large-scale solvers were employed to compare the proposed linearization with the conventional nonlinear nonconvex model. © 2004-2012 IEEE.
Output Voltage Regulation for DC-DC Buck Converters: A Passivity-Based PI Design
(Institute of Electrical and Electronics Engineers Inc., 2019) Gil-González, Walter; Montoya O.D.; Garces A.; Serra F.M.; Magaldi G.
This paper presents a global tracking passivity-based proportional-integral (PI) control for output voltage regulation of a DC-DC Buck converter. The proposed controller is based on passivity formulation since DC-DC Buck converter has a passive structure in open-loop. Additionally, the controller takes advantage of the PI actions to design a control law that guarantees asymptotically stability in the Lyapunov's sense under closed-loop operation. The proposed controller does not depend on the parameters, which makes it a robust controller. The robustness of the proposed controller is checked by comparing its dynamical performance in front of a conventional PID controller. All simulation results were fulfilled via MATLAB software. © 2019 IEEE.
Passivity-Based Control for Hydro-Turbine Governing Systems
(Institute of Electrical and Electronics Engineers Inc., 2018) Gil-González, Walter; Garces A.; Escobar Mejía, Andrés; Montoya O.D.
In this paper an interconnection and damping assignment passivity-based control (IDA-PBC) applied to the hydro-Turbine governing systems (HTGS) is proposed to regulate the relative deviation of turbine speed in single machine infinite bus system. The passivity-based control (PBC) theory is selected because in the open-loop the HTGS has a port-Hamiltonian (pH) structure. The PBC theory takes advantage of the pH structure of the open-loop dynamical system to design a general control law, which preserves the passive structure in closedloop via interconnection and damping reassignment. Additionally, the PBC theory guarantees globally asymptotically stability in the sense of Lyapunov for the close-loop dynamical system. Time-domain simulations demonstrate the robustness and proper performance of the proposed methodology applied to the HTGS under different operative conditions. © 2018 IEEE.
Power flow approximation for DC networks with constant power loads via logarithmic transform of voltage magnitudes
(Elsevier Ltd, 2019) Montoya O.D.; Gil-González W.; Garces A.
This paper proposes a logarithmic transformation of voltages (LTVM) for the power flow in DC grids. This problem is non-linear due to the presence of constant power loads (CPLs), which also introduce a negative resistance effect that can create numerical instability for conventional algorithms. The proposed methodology is applied to dc-microgrids, dc-distribution and multi-terminal high voltage DC transmission (MT-HVDC). Two main approximations are presented and compared in terms of computational performance and the accuracy of the solution. Simulation results performed in Matlab/Octave demonstrate the advantages of the proposed methodology using a complete set of test systems, from low to high voltage applications. The proposed methodology does not require any consideration about the topology of the grid (radial or meshed) or the number of constant power loads. © 2019 Elsevier B.V.
SCES Integration in Power Grids: A PBC Approach under abc, αβ0 and dq0 Reference Frames
(Institute of Electrical and Electronics Engineers Inc., 2018) Montoya O.D.; Gil-González, Walter; Garces A.
This paper presents an integration of three-phase supercapacitor energy storage (SCES) in power grids via passivity-based control (PBC) theory under different reference frames. The SCES systems have the possibility to interchange active and reactive power between the supercapacitor and converter to the electrical power network. The active power is directly related to the energy stored on the supercapacitor, while the reactive power is redistributed by the forced commutated switches present in the voltage source converter (VSC) used to integrate the SCES system to the power grid. PBC theory allows designing Lyapunov stable controllers for autonomous and non-Autonomous dynamical sys-Tems via port-Hamiltonian (pH) representations. The averaging modeling theory employs to develop the controllers under abc, alpha\beta and dq reference frames. Simulation results show the possibility of using the SCES devices to compensate active and reactive power in power grids dynamically in all operating quadrants. All simulations are conducted via MATLAB/SIMULINK software. © 2018 IEEE.