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Papers by CARLOS XAVIER ROSERO CHANDI
Microgrids (MGs) are small-scale power systems containing storage elements, loads and distributed... more Microgrids (MGs) are small-scale power systems containing storage elements, loads and distributed generators that are interfaced with the electric network via power electronic inverters. When an MG is in islanded mode, its dynamics are no longer dominated by the main grid. Then, the inverters, driven by digital processors that may exchange data over digital communication, must act as voltage source inverters (VSIs) to take coordinated actions to ensure power quality and supply. The scope of this thesis is bounded to control strategies for active power sharing and frequency regulation in islanded MGs. The focus is on the analysis of prototype control policies when operating conditions are no longer ideal. In particular, the thesis covers the effect that a) clock drifts of digital processors, b) damage in power transmission lines, and c) failures in digital communications have in control performance. The work is submitted as a compendium of publications, including journal and international conference papers, where two main areas of research can be distinguished. The first area refers to the analysis of the effect that clock drifts have on frequency regulation and active power sharing. VSI digital processors are equipped with oscillators which run at not necessarily identical frequencies. As consequence, the local clocks in the physically distributed inverters may differ. This part, reported in two conference papers and one journal paper, investigates state-of-the-art control policies when clocks of the computational devices drift. The contributions related to this part are a) the reformulation of existing control policies in terms of clock drifts, b) the steady-state analysis of these policies that offers analytical expressions to quantify the impact that drifts have on frequency and active power equilibrium points, c) the closed-loop model capable of accommodating all the policies, d) the stability analysis of the equilibrium points, and e) the experimental results. The second area copes with the analysis of the effect that electrical and communication failures have on frequency regulation and active power sharing. This investigation focuses on distributed/cooperative control policies where each inverter control action is computed using both local measures and data received from other inverters within the MG. This part, reported in one conference paper and two journal papers, investigates two control policies when the considered failures in terms of damage in power links and/or loss of communications between inverters provoke partitions within the MG. The contributions related to this part are a) the formulation of the MG as two connected graphs corresponding to the electrical and communication networks where both type of failures lead to disconnected electrical/communication sub-graphs, named partitions, that co-exist within the MG, b) the closed-loop Miguel Castilla, Jaume Miret and Antonio Camacho, for the scientific collaboration, resource management, and lab facilities, useful to successfully overcome this work.
La U Investiga, Jun 30, 2020
2017 IEEE 26th International Symposium on Industrial Electronics (ISIE), 2017
The application of consensus theory in the control of islanded microgrids (MG) is gaining increas... more The application of consensus theory in the control of islanded microgrids (MG) is gaining increased attention because it facilitates the development of distributed control solutions. In particular, its application to active power sharing and frequency regulation has lead to satisfactory results. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG) when governed by a distributed consensus algorithm. Analytical expressions that relate the steady-state frequency and active power as a function of each VSI local drift are provided. These expressions allow extracting tuning rules for the consensus-based control algorithm. Simulation results permit corroborating the theoretical analysis.
MASKAY, 2021
El rendimiento de los lazos de control cerrados a través de redes de comunicación puede deteriora... more El rendimiento de los lazos de control cerrados a través de redes de comunicación puede deteriorarse debido a retardos variables de tiempo provocados por congestión y latencia en la red, y por procesamiento de los algoritmos de control, efecto conocido en muestreo periódico como jitter. Para remover este efecto perjudicial sobre la estabilidad/rendimiento, el método de sincronización en instantes de actuación usa un observador que estima el valor de los estados en el instante de actuación, conociendo las medidas de estos en el instante de muestreo, lo que conlleva a actuaciones estrictamente periódicas. Sin embargo, su aplicación exitosa requiere de muestras libres de ruido y procesos sin perturbación, cuestiones no alcanzables en la realidad. En este artículo se extiende el modelo mencionado al caso de condiciones no ideales de funcionamiento. En particular, se incorpora un filtro de Kalman en el modelo de actuación sincronizada, considerando que las mediciones disponibles de los e...
SATHIRI, 2018
Los sistemas embebidos de hardware libre (OSHW, Open Source Hardware) han sido ampliamente aplica... more Los sistemas embebidos de hardware libre (OSHW, Open Source Hardware) han sido ampliamente aplicados en la enseñanza de sistemas microprocesados; la edición, compilación y programación de aplicaciones para OSHW se realizan a través de entornos de desarrollo integrado (IDEs, Integrated Development Environments). Este artículo presenta una metodología para evaluar la usabilidad de IDEs de OSHW y se centra en la plataforma de Arduino por ser una de las más utilizadas hoy en día en la academia; conocer qué tan fácil y confortable es aprender a programar microcontroladores en Arduino es un objetivo colateral pero de igual importancia. La principal contribución de este trabajo consiste en utilizar enfoques de efectividad, eficiencia y satisfacción del usuario para la evaluación de usabilidad de IDEs de programación de OSHW. La evaluación se centra en la realización de programas con complejidad dentro de una escala ascendente. La efectividad se determina en relación al cumplimiento satisfa...
IEEE Transactions on Power Electronics, 2018
Local hardware clocks in physically distributed computation devices hardly ever agree because clo... more Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.
IEEE Transactions on Industrial Electronics, 2019
The droop-free control for AC microgrids achieves active power sharing and frequency regulation b... more The droop-free control for AC microgrids achieves active power sharing and frequency regulation by replacing the centralized secondary control and the primary-level droop mechanism by a cooperative distributed control strategy. This paper analyses the performance of the droop-free control when an islanded microgrid suffers electrical and communication failures. The microgrid is modeled by two connected graphs corresponding to the electrical and communication networks. The considered failures leads to partitioned electrical/communication subgraphs that co-exist within the microgrid. A closed-loop model integrating the power flow equations, the droop-free control, and the electrical and communication graphs is derived. The stability analysis identifies critical partitions where the microgrid is driven to the instability, and the steady-state analysis characterizes the equilibrium points when the partitioned microgrid remains stable. The paper also provides a control strategy that is able to avoid the instability scenario. Selected experimental results on a low-scale laboratory microgrid illustrate the impact that failures have in system performance and the ability of the proposed control for confining the microgrid operation into a safe region.
IEEE Transactions on Smart Grid, 2019
IEEE Transactions on Energy Conversion, 2018
In islanded microgrids, voltage source inverters working in parallel are expected to provide regu... more In islanded microgrids, voltage source inverters working in parallel are expected to provide regulation of the local frequency while granting active power sharing. This paper presents a local control approach at each inverter based on an event-driven operation of a parameter-varying filter. It ensures perfect active power sharing and controllable accuracy for frequency restoration without requiring the exchange of control data between inverters over the communication network. The paper includes stability analysis and design guidelines for the control parameters using a modeling approach that considers the interaction between inverters. Selected experimental results on a three-inverter laboratory microgrid corroborate the effectiveness of the proposed control scheme, and outlines its advantages with respect to previous similar schemes and the performance cost that implies not using communications.
MASKAY, Nov 17, 2017
The self-triggered control includes a sampling strat-C.X. Rosero and J. Benavides are with the Ap... more The self-triggered control includes a sampling strat-C.X. Rosero and J. Benavides are with the Applied Sciences Faculty,
Microgrids (MGs) are small-scale power systems containing storage elements, loads and distributed... more Microgrids (MGs) are small-scale power systems containing storage elements, loads and distributed generators that are interfaced with the electric network via power electronic inverters. When an MG is in islanded mode, its dynamics are no longer dominated by the main grid. Then, the inverters, driven by digital processors that may exchange data over digital communication, must act as voltage source inverters (VSIs) to take coordinated actions to ensure power quality and supply. The scope of this thesis is bounded to control strategies for active power sharing and frequency regulation in islanded MGs. The focus is on the analysis of prototype control policies when operating conditions are no longer ideal. In particular, the thesis covers the effect that a) clock drifts of digital processors, b) damage in power transmission lines, and c) failures in digital communications have in control performance. The work is submitted as a compendium of publications, including journal and international conference papers, where two main areas of research can be distinguished. The first area refers to the analysis of the effect that clock drifts have on frequency regulation and active power sharing. VSI digital processors are equipped with oscillators which run at not necessarily identical frequencies. As consequence, the local clocks in the physically distributed inverters may differ. This part, reported in two conference papers and one journal paper, investigates state-of-the-art control policies when clocks of the computational devices drift. The contributions related to this part are a) the reformulation of existing control policies in terms of clock drifts, b) the steady-state analysis of these policies that offers analytical expressions to quantify the impact that drifts have on frequency and active power equilibrium points, c) the closed-loop model capable of accommodating all the policies, d) the stability analysis of the equilibrium points, and e) the experimental results. The second area copes with the analysis of the effect that electrical and communication failures have on frequency regulation and active power sharing. This investigation focuses on distributed/cooperative control policies where each inverter control action is computed using both local measures and data received from other inverters within the MG. This part, reported in one conference paper and two journal papers, investigates two control policies when the considered failures in terms of damage in power links and/or loss of communications between inverters provoke partitions within the MG. The contributions related to this part are a) the formulation of the MG as two connected graphs corresponding to the electrical and communication networks where both type of failures lead to disconnected electrical/communication sub-graphs, named partitions, that co-exist within the MG, b) the closed-loop Miguel Castilla, Jaume Miret and Antonio Camacho, for the scientific collaboration, resource management, and lab facilities, useful to successfully overcome this work.
La U Investiga, Jun 30, 2020
2017 IEEE 26th International Symposium on Industrial Electronics (ISIE), 2017
The application of consensus theory in the control of islanded microgrids (MG) is gaining increas... more The application of consensus theory in the control of islanded microgrids (MG) is gaining increased attention because it facilitates the development of distributed control solutions. In particular, its application to active power sharing and frequency regulation has lead to satisfactory results. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG) when governed by a distributed consensus algorithm. Analytical expressions that relate the steady-state frequency and active power as a function of each VSI local drift are provided. These expressions allow extracting tuning rules for the consensus-based control algorithm. Simulation results permit corroborating the theoretical analysis.
MASKAY, 2021
El rendimiento de los lazos de control cerrados a través de redes de comunicación puede deteriora... more El rendimiento de los lazos de control cerrados a través de redes de comunicación puede deteriorarse debido a retardos variables de tiempo provocados por congestión y latencia en la red, y por procesamiento de los algoritmos de control, efecto conocido en muestreo periódico como jitter. Para remover este efecto perjudicial sobre la estabilidad/rendimiento, el método de sincronización en instantes de actuación usa un observador que estima el valor de los estados en el instante de actuación, conociendo las medidas de estos en el instante de muestreo, lo que conlleva a actuaciones estrictamente periódicas. Sin embargo, su aplicación exitosa requiere de muestras libres de ruido y procesos sin perturbación, cuestiones no alcanzables en la realidad. En este artículo se extiende el modelo mencionado al caso de condiciones no ideales de funcionamiento. En particular, se incorpora un filtro de Kalman en el modelo de actuación sincronizada, considerando que las mediciones disponibles de los e...
SATHIRI, 2018
Los sistemas embebidos de hardware libre (OSHW, Open Source Hardware) han sido ampliamente aplica... more Los sistemas embebidos de hardware libre (OSHW, Open Source Hardware) han sido ampliamente aplicados en la enseñanza de sistemas microprocesados; la edición, compilación y programación de aplicaciones para OSHW se realizan a través de entornos de desarrollo integrado (IDEs, Integrated Development Environments). Este artículo presenta una metodología para evaluar la usabilidad de IDEs de OSHW y se centra en la plataforma de Arduino por ser una de las más utilizadas hoy en día en la academia; conocer qué tan fácil y confortable es aprender a programar microcontroladores en Arduino es un objetivo colateral pero de igual importancia. La principal contribución de este trabajo consiste en utilizar enfoques de efectividad, eficiencia y satisfacción del usuario para la evaluación de usabilidad de IDEs de programación de OSHW. La evaluación se centra en la realización de programas con complejidad dentro de una escala ascendente. La efectividad se determina en relación al cumplimiento satisfa...
IEEE Transactions on Power Electronics, 2018
Local hardware clocks in physically distributed computation devices hardly ever agree because clo... more Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.
IEEE Transactions on Industrial Electronics, 2019
The droop-free control for AC microgrids achieves active power sharing and frequency regulation b... more The droop-free control for AC microgrids achieves active power sharing and frequency regulation by replacing the centralized secondary control and the primary-level droop mechanism by a cooperative distributed control strategy. This paper analyses the performance of the droop-free control when an islanded microgrid suffers electrical and communication failures. The microgrid is modeled by two connected graphs corresponding to the electrical and communication networks. The considered failures leads to partitioned electrical/communication subgraphs that co-exist within the microgrid. A closed-loop model integrating the power flow equations, the droop-free control, and the electrical and communication graphs is derived. The stability analysis identifies critical partitions where the microgrid is driven to the instability, and the steady-state analysis characterizes the equilibrium points when the partitioned microgrid remains stable. The paper also provides a control strategy that is able to avoid the instability scenario. Selected experimental results on a low-scale laboratory microgrid illustrate the impact that failures have in system performance and the ability of the proposed control for confining the microgrid operation into a safe region.
IEEE Transactions on Smart Grid, 2019
IEEE Transactions on Energy Conversion, 2018
In islanded microgrids, voltage source inverters working in parallel are expected to provide regu... more In islanded microgrids, voltage source inverters working in parallel are expected to provide regulation of the local frequency while granting active power sharing. This paper presents a local control approach at each inverter based on an event-driven operation of a parameter-varying filter. It ensures perfect active power sharing and controllable accuracy for frequency restoration without requiring the exchange of control data between inverters over the communication network. The paper includes stability analysis and design guidelines for the control parameters using a modeling approach that considers the interaction between inverters. Selected experimental results on a three-inverter laboratory microgrid corroborate the effectiveness of the proposed control scheme, and outlines its advantages with respect to previous similar schemes and the performance cost that implies not using communications.
MASKAY, Nov 17, 2017
The self-triggered control includes a sampling strat-C.X. Rosero and J. Benavides are with the Ap... more The self-triggered control includes a sampling strat-C.X. Rosero and J. Benavides are with the Applied Sciences Faculty,