Browsing by Author "Cuzmar Leiva, Rodrigo Hernán"

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    Dual-Stage MPC for SoC Balancing in Second-Life Battery Energy Storage Systems Based on Delta-Connected Cascaded H-Bridge Converters
    (2024) Poblete Durruty, Pablo Martín; Cuzmar Leiva, Rodrigo Hernán; Aguilera, Ricardo P.; Pereda Torres, Javier Eduardo; Alcaide, Abraham M.; Lu, Dylan Dah-Chuan; Siwakoti, Yam Prasad; Konstantinou, Georgios
    Using second-life batteries (SLBs) to build battery energy storage systems (BESS) yields substantial environmental and economic benefits. The cascaded H-Bridge (CHB) converter has emerged as an attractive candidate to integrate SLBs into the electrical grid, allowing the unbalanced power distribution among its sub-modules (SMs) with high efficiency and a low estimated cost. However, capacity differences among SLBs pose further challenges for the control system in meeting the BESS power constraints, while balancing the state-of-charge (SoC) of SLBs. This work proposes a dual-stage model predictive control (DS-MPC) strategy to balance the SoC of SLBs using a delta-connected CHB (DCHB) converter. The formulation of the proposed DS-MPC strategy is based on a discrete-time SoC dynamic model, which considers the SM modulating signals and the DCHB circulating current reference in the rotating synchronous dq-frame as control inputs. In this way, the proposed DS-MPC strategy obtains optimal charging and discharging currents for each SLB-SM by solving two sequential optimizations, which include maximum current ratings and converter modulation constraints, ensuring the safe operation of the BESS. Experimental results that verify the effectiveness of the proposed DS-MPC strategy are provided for a DCHB converter with nine SMs connected to Lithium-ion SLB packs of different capacities.
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    Offset-Free Optimal Control of Cascaded H-Bridge Converters Based on a Kalman Filter Harmonic Compensator
    (2024) Poblete Durruty, Pablo Martín; Aguilera, Ricardo P.; Pereda Torres, Javier Eduardo; Cuzmar Leiva, Rodrigo Hernán; Alcaide, Abraham M.; Lu, Dylan Dah-Chuan; Siwakoti, Yam Prasad; Acuña, Pablo
    Cascaded H-bridge (CHB) converters are suitable candidates for numerous applications, including electrical drives, static synchronous compensators, and battery energy storage inverters. Optimal control strategies for CHB converters have attracted significant interest in recent decades due to their flexibility in including multiple control objectives and their simple design process. However, the steady-state performance of these control strategies deteriorates if the CHB converter model has parameter mismatches and/or the sub-module (SM) capacitor voltage ripples are not measured. This work proposes a Kalman Filter (KF) based strategy to eliminate the steady-state error and undesired low-frequency harmonic components in the CHB converter output currents. The proposed KF strategy estimates the instantaneous arm voltage harmonics representing the converter modelling errors and unaccounted disturbances. Then, these estimated voltage harmonics are used to improve the arm current predictions and obtain a compensation term for the steady-state arm voltage references to be used by the optimal control strategy. Experimental results for three different optimal control schemes are provided for a three-phase CHB converter with nine SMs to confirm the effectiveness of the proposed KF strategy.
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    Phase-Shifted Model Predictive Control to Achieve Power Balance of CHB Converters for Large-Scale Photovoltaic Integration
    (2020) Cuzmar Leiva, Rodrigo Hernán; Pereda Torres, Javier Eduardo; Aguilera, Ricardo P.
    Cascaded H-Bridge (CHB) converters are attractive candidates for next generation photovoltaic (PV) inverters. CHB converters present a reduced voltage stress per power switch and a high modularity. Therefore, the plant can be divided in several PV strings that can be connected to each H-bridge cell. However, due to variability on solar irradiance conditions, each PV string may present different maximum available power levels, which difficult the overall converter operation. To address this issue, this paper presents a model predictive control (MPC) strategy, which works along with a phase-shifted PWM (PS-PWM) stage; hence its name phase-shifted MPC (PS-MPC). The novelty of this proposal is the way both inter-bridge and inter-phase power imbalance are directly considered into the optimal control problem by a suitable system reference design. Thus, the inter-phase imbalance power is tackled by enforcing the converter to operate with a proper zero-sequence voltage component. Then, by exploiting the PS-PWM working principle, PS-MPC is able to handle each H-bridge cell independently. This allows the predictive controller to also deal with an inter-bridge power imbalance using the same control structure. Experimental results on a 3 kW prototype are provided to verify the effectiveness of the proposed PS-MPC strategy.
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    Predictive control strategies of modular multilevel matrix converter
    (2024) Cuzmar Leiva, Rodrigo Hernán; Pereda Torres, Javier Eduardo; Aguilera Echeverría, Ricardo; Mora Castro, Andrés; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Actualmente, el mundo está cambiando la forma en que genera energía, pasando de un sistema eléctrico basado en baja penetración de energías renovables, flujos de potencia unidireccionales y baja participación de conversores de potencia, a un sistema eléctrico con alta inclusión de energías renovables, flujos de potencia bidireccionales y alto uso de conversores de potencia. Los conversores AC-AC jugarán un rol fundamental en los sistemas del futuro, en aplicaciones como la interconexión de sistemas de potencia, sistemas de transmisión AC de baja frecuencia (LFAC), sistemas de conversión de energía eólica (WECS) y como accionamiento de motores de medio/alto voltaje para bombas, molinos, cintas transportadoras, tracción marina, entre otras aplicaciones. Chile y Australia predicen que, para el 2050, los sistemas eólicos serán una de las principales fuentes de energía para industrias y personas. Adicionalmente, ambos países presentan una actividad minera activa, aplicación que considera múltiples accionamientos para motores. Sin embargo, los futuros conversores AC-AC para las aplicaciones mencionadas anteriormente, como por ejemplo el conversor matricial modular multinivel (M3C), presentan diversos desafíos para su implementación, tales como alto acoplamiento de los estados internos, alta complejidad para el control y balance de varios capacitores flotantes, gran cantidad de señales de control y oscilaciones en el voltaje de los capacitores a frecuencias críticas, desafíos que complican su implementación en aplicaciones de alto voltaje que requieren un gran número de sub-módulos. Este proyecto de investigación apunta al desarrollo de estrategias de control predictivo para controlar un M3C, que se componen de dos partes: un controlador interno encargado del control de corrientes y del control de balance local del clúster, y un controlador externo que logra el control de balance entre clústeres y mitiga las oscilaciones de baja frecuencia del voltaje de los capacitores de los sub-módulos. Por un lado, se proponen dos estrategias como controlador interno: una basada en control predictivo por modelo con desplazamiento de fase secuencial y otra basada en control predictivo por modelo con conjunto de control finito (FCS-MPC). Por otro lado, se proponen dos generadores de referencia como controlador externo: el primero genera corrientes circulantes en función de la energía de los clústeres en un espacio transformado, y el segundo considera corrientes circulantes y voltaje de modo común para balancear la energía del M3C. Finalmente, los resultados experimentales prueban la eficacia de la estrategia de control diseñada para controlar un M3C, logrando alcanzar las referencias de corriente y energía. Más aún, todas las propuestas son comparadas con estrategias de la literatura. En estado estacionario, el error de seguimiento promedio de corrientes y voltajes es de 1.96% y 1.82%, respectivamente, reduciendo el rizado del voltaje de los capacitores para baja frecuencia en 31% y para frecuencias iguales en 36%. Durante transientes, por un lado, cambios en escalón de potencia y frecuencia son seguidos instantáneamente. Por otro lado, cambios en escalón en los controles de balance local y entre clústeres son seguidos en 80 y 200 ms, respectivamente. Finalmente, la carga computacional de todas las propuestas incrementa linealmente con el número de sub-módulos, con excepción de la estrategia basada en FCSMPC.
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    Predictive Optimal Variable-Angle PS-PWM Strategy for Cascaded H-Bridge Converters
    (2024) Poblete Durruty, Pablo Martín; Gajardo Rojas, José Ignacio; Cuzmar Leiva, Rodrigo Hernán; Aguilera, Ricardo P.; Pereda Torres, Javier Eduardo; Lu, Dylan; Márquez, Abraham M.
    Cascaded H-bridge (CHB) converters are an attractive candidate for numerous applications, including static synchronous compensators and next-generation photovoltaic and battery energy storage inverters. Due to its simplicity, scalability, and excellent harmonic performance, phase-shifted pulsewidth modulation (PS-PWM) is one of the preferred modulation strategies for CHB converters. However, the latter advantage might be drastically affected when an unbalanced operation in the H-bridge cells is required, e.g., setting different dc-voltage levels and/or ac-voltage references among cells. This work proposes a predictive optimal variable angle PS-PWM (OVA-PS-PWM) strategy for CHB converters. The proposed OVA-PS-PWM introduces a bilinear dynamic model that describes the impact of the phase-shift angles (PS-angles) over the CHB output voltage harmonics. This model is then employed to formulate an optimal control problem that minimizes the output voltage harmonic distortion. An analytical optimal solution for a PS-angle update rule that applies to CHB converters of any number of cells is derived. As a result, the proposed OVA-PS-PWM updates each PS-angle at every sampling instant, significantly improving the harmonic content of the CHB output voltage even under severely unbalanced operation scenarios. Experimental results are provided with a CHB converter with nine cells to verify the effectiveness of the proposed optimal modulation strategy.
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    Sequential Phase-Shifted Model Predictive Control for a Multilevel Converter with Integrated Battery Energy Storage
    (IEEE, ) Neira, Sebastián; Poblete, Pablo; Cuzmar Leiva, Rodrigo Hernán; Pereda Torres, Javier Eduardo; Aguilera, Ricardo P.
    Cascaded converters have risen as a suitable solution for the connection of Utility-scale Battery Energy Storage Systems (BESS) to the grid. These converters allow to split the battery array into the power modules, reducing the total series-connected battery cells and improving the reliability of the system. Different types of modules have been proposed to integrate the batteries in the converter. The three-port full-bridge module connects the batteries through a second deport decoupled from the harmful low-frequency oscillations and current peaks. However, the multi-variable controller required to manage the power interaction between the battery and the grid presents a challenge in terms of computational burden and scalability. This work proposes the use of the Sequential Phase-Shifted Model Predictive Control (PS-MPC) in a multilevel BESS implementation using three-port full-bridge modules. The proposed controller outperforms a standard FCS-MPC, as it obtains the optimal duty cycles for the operation of the converter with the same fast dynamic response, but also with the fixed spectrum of the PS-PWM and low computational burden, which facilitates its scalability to multilevel BESS with a large number of cells. Simulation results show the ability of the system to exchange different amounts of power with the grid, ensuring the best battery operational conditions