Browsing by Author "Aguilera, Ricardo P."

Now showing 1 - 12 of 12
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    An Improved Reference Generator Based on MPC of Circulating Currents and Common-Mode Voltage for Modular Multilevel Matrix Converters
    (IEEE-Inst Electrical Electronics Engineers Inc, 2024) Cuzmar Leiva, Rodrigo Hernan; Mora, Andres; Pereda, Javier; Aguilera, Ricardo P.
    This article proposes an improved reference generator based on model-predictive-control (MPC) for the modular multilevel matrix converter (M3C). The novelty of the proposal is in optimally obtaining the circulating currents and CMV references to achieve the intercluster balancing (ICB) control and low-frequency oscillations mitigation (LFOM) of the M3C. Additionally, the proposed optimal control problem is designed in the original framework and includes bound constraints for circulating currents and CMV for a proper operation of the M3C. As a result, the MPC-based reference generator allows to regulate the cluster energies with low capacitor voltage ripple and operate at low and equal frequencies while keeping the cluster currents under safe limits. Experimental results have been conducted using a 3 kVA prototype to validate the proposed strategy's effectiveness and high-quality performance.
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    Closed-Loop Performance Improvement for MMCs Based on Optimal Reference Governor
    (2021) Poblete, Pablo; Neira, Sebastian; Cuzmar, Rodrigo; Aguilera, Ricardo P.; Mora, Andres; Pereda Torres, Javier
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    Distributed Current Control of Cascaded Multilevel Inverters
    (IEEE, 2019) Poblete Durruty, Pablo Martín; Pereda Torres, Javier Eduardo; Nuñez Retamal, Felipe Eduardo; Aguilera, Ricardo P.
    Multilevel inverters are widely used in the medium voltage energy market. Among them, the Cascaded H-Bridge (CHB) and Modular Multilevel Inverter (MMC) stand out for their modular hardware, which allows the easy replacement of their modules in the case of failures. Normally, these converters are operated with centralized control schemes, which require a large processing capacity, multiple digital outputs and wires for the switching signals of the transistors. The use of a centralized controller reduces the modularity of the system and generates difficulties as the number of inverters connected in series (cells) increases. In this work, a distributed control strategy for CHB converters is proposed, allowing each cell to have an independent local controller, which increases the modularity of the multilevel converter without deteriorating the performance of the system. Extensive simulations are carried out, showing the advantages and disadvantages of the proposed distributed control strategy offers when compared to a PI current controller on dq axes and Shifted PWM. The proposed control scheme is also tested under fault conditions and is finally applied in a Field Oriented Control (FOC) of a permanent magnet synchronous machine (PMSM), in order to evaluate its performance in electrical drives applications.
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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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    Enhanced PI Control Based SHC-PWM Strategy for Active Power Filters
    (2024) Ibanez-Hidalgo, Irati; Cuzmar, Rodrigo H.; Sanchez-Ruiz, Alain; Perez-Basante, Angel; Zubizarreta, Asier; Ceballos, Salvador; Aguilera, Ricardo P.
    Low-switching frequency modulation techniques, such as selective harmonic control-pulsewidth modulation (SHC-PWM), have been recently proposed for high-power medium-voltage active power filter (APF) application. Compared to high-switching frequency modulation techniques, these methods reduce the switching losses and avoid derrating the current. This results in enhanced power density and efficiency, and facilitates a reduction in costs. However, the low-switching frequency tends to worsen the closed-loop dynamic response and system stability if countermeasures are not taken during the design process of the closed-loop controllers. Moreover, the digital filter used to obtain the harmonic components of the measured signals introduces a delay that can affect the stability and performance of the closed-loop control. This work presents different methods to improve the dynamic response of traditional proportional-integral based closed-loop controllers, which are applied along with SHC-PWM for high-power medium-voltage APFs. A current predictor that substitutes the traditional cross-coupling terms and a Smith predictor are proposed to compensate the delay introduced by the digital filters. In addition, different digital filter implementations are analyzed and compared in terms of dynamic and stationary response with the aim of improving the harmonic estimation from the measured signals. Experimental results for a 3-level NPC converter are provided to verify the effectiveness of the control.
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    Generalized Feed-Forward Sampling Method for Multilevel Cascaded H-Bridge Converters
    (IEEE-Inst. Electrical Electronics Engineers Inc., 2023) Alcaide, Abraham M.; Poblete Durruty, Pablo Martin; Vazquez, Sergio; Aguilera, Ricardo P.; Leon, Jose I.; Kouro, Samir; Franquelo, Leopoldo G.
    Multilevel cascaded H-bridge (CHB) converters are usually operated applying a phase-shifted pulsewidth modulation (PS-PWM) method. In this modulation strategy, it is important to define the sampling instants in order to obtain a superior harmonic performance in the CHB output waveforms. Previous approaches to define the PS-PWM method consider a shorter sampling time, becoming even smaller when the number of cells of the CHB is large. In addition, unbalanced operational conditions in the CHB aggravate this issue also degrading the CHB harmonic performance. In this article, both challenges (small sampling time and unbalanced operational conditions) are faced. A feed-forward compensation technique is proposed to face with the unbalanced operating conditions and enlarging the available computational time for control schemes keeping the good CHB harmonic performance. Experimental results demonstrate the superior performance of the proposed strategy.
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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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    Optimal Switching Sequence Direct Power Control for AC/DC Converters with Enhanced Converter Model for Lower Switching Frequencies
    (2022) Poblete, Pablo; Syasegov, Yaroslav Y.; Farhangi, Majid; Aguilera, Ricardo P.; Siwakoti, Yam P.; Lu, Dylan; Pereda Torres, Javier
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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 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
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    Sequential Phase-Shifted Model Predictive Control for Modular Multilevel Converters
    (2021) Poblete Durruty, Pablo Martín; Neira Castillo, Sebastian Felipe; Aguilera, Ricardo P.; Pereda Torres, Javier Eduardo; Pou, Josep
    Model predictive control has emerged as a promising approach to govern modular multilevel converters (MMCs), due to its flexibility to include multiple control objectives and simple design process. However, this control scheme presents relevant issues, such as high computational complexity and variable switching frequency. This work proposes a sequential phase-shifted model predictive control (PS-MPC) for MMCs. The key novelty of this proposal lies in the way the predictive control strategy is formulated to fully exploit a phase-shifted pulsewidth modulation technique, by means of an appropriate choice of synchronized average models for each carrier. In this way, the proposed predictive controller obtains independent optimal modulating signals for each carrier in a sequential manner, by solving an optimization problem with reduced computational effort independent of the number of submodules. This allows one to formulate the optimal control problem to achieve multiple control objectives, similarly to the finite-control-set MPC (FCS-MPC). Nevertheless, the MMC governed with the proposed PS-MPC generates an output voltage with fix-spectrum and operates with an even power loss distribution among semiconductors in steady-state, outperforming the standard FCS-MPC strategy. Experimental results are provided to verify the proposed PS-MPC effectiveness when governing a three-phase MMC with four half-bridges per stack.