Browsing by Author "Neira Castillo, Sebastian Felipe"

Now showing 1 - 7 of 7
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    A Novel Three-Port NPC Converter for Grid-Tied Photovoltaic Systems with Integrated Battery Energy Storage
    (IEEE, 2020) Neira Castillo, Sebastian Felipe; Lizana Gajardo, Alonso Javier; Pereda Torres, Javier Eduardo
    The variable behaviour of the photovoltaic (PV) generation arises as the main drawback of this technology. Therefore, Battery Energy Storage (BES) units appear as a promising solution to overcome the inherent intermittent generation profile of PV systems. BES can be implemented separated from the PV generation units or integrated within a single power system. The latter option gives a better dynamic response, as the variable generation can be directly complemented with the BES, controlling the power flow between both elements with the grid. Thus, there is a need for power converters with capability of interface both PV and BES with the grid in a reliable and efficient way. This paper proposes a Three-Port NPC converter to connect a PV array and a BES unit with the ac grid using a single power processing stage. The converter is based in the H-NPC inverter and allows the connection of a low voltage battery to act as a power buffer ensuring a firm energy dispatch to the grid. Furthermore, simulation results show that the proposed topology maintains the good performance of the H-NPC in terms of efficiency, voltage harmonic distortion and reduced leakage current.
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    Consensus-Based Distributed Control of a Multilevel Battery Energy Storage System
    (IEEE, 2020) Neira Castillo, Sebastian Felipe; Poblete Durruty, Pablo Martín; Pereda Torres, Javier Eduardo; Nuñez Retamal, Felipe Eduardo
    Battery Energy Storage Systems (BESS) based on modular multilevel cascaded topologies allow splitting the battery array into the converter sub-modules, improving efficiency and reliability of the solution. Modular converters can perform active balance of the battery packs and regulation of the output power through the use of multi-objective controllers commanding the power of each sub-module accordingly. However, despite the hardware modularity of multilevel BESS, the controller is usually based on centralized designs, which present issues in terms of computational load and scalability. This paper proposes a two-layer distributed control scheme, based on a high-level consensus algorithm to perform the State of Charge (SoC) balance and low-level individual multi-variable controllers to regulate the operation of the converter sub-modules. The controller was implemented in a cascaded topology, where each sub-module determines and regulates its output power considering the information of its neighbours. The proposed solution allows to fully exploit the modularity of the converter, distributing the control units in the power modules to improve the overall flexibility and scalability of the system. Simulations results validate the operation of the proposed system, showing how the converter sub-modules distribute its power outputs to equalize the SoC levels. Furthermore, the distribution of the multi-variable controllers reduces the computational burden, as each unit just regulates the operation of the respective sub-module.
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    Sequential Phase-Shifted Model Predictive Control for a Multilevel Converter with Integrated Battery Energy Storage
    (IEEE, 2020) Neira Castillo, Sebastian Felipe; Poblete Durruty, Pablo Martín; Cuzmar Leiva, Rodrigo Hernán; Pereda Torres, Javier Eduardo; Aguiler, R. 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.
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    Three-Port Full-Bridge Bidirectional Converter for Hybrid DC/DC/AC Systems
    (IEEE, 2020) Neira Castillo, Sebastian Felipe; Pereda Torres, Javier Eduardo; Rojas, Félix
    Sustainable solutions such as renewable energies, distributed generation, energy storage, and electric vehicles require power conversion and advance control techniques. This process is usually done in two stages by more than one power converter, specially in hybrid systems, increasing power losses and costs. The configuration with two dc stages and one ac port is widely used in several applications, such as grid-connected photovoltaic inverters; fuel cells, hybrid and electric vehicles; and ac/dc microgrids. Thus, three-port topologies have been developed to operate such systems, most of them comprising multiple power processing stages for the connection of the different elements. This article proposes a three-port full-bridge converter with a single power processing stage for dc/dc/ac systems. The ac port can be single-phase or three-phase, using two legs like an H-bridge or three legs like the conventional three-phase inverter. In both configurations, each leg is used as an inverter and as a buck-boost converter at the same time. The converter is able to manage the power flow among three ports with just four or six switches through a multivariable control strategy. Simulation and experimental results show the capability of the converter to manage the interaction between a battery and a capacitor connected to the grid achieving a fast dynamic response, bidirectional capability in all ports and reduction of components.
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    Three-Port Full-Bridge Cell for Multilevel Converters with Battery Energy Storage
    (IEEE, 2019) Neira Castillo, Sebastian Felipe; Pereda Torres, Javier Eduardo; Merlin, Michael; Rojas, Félix
    Utility-scale Battery Energy Storage Systems (BESS) have increased rapidly during the last years providing grid support for variable renewable energies, operating reserve, and any other possible ancillary service. BESS can be connected to the MV grid through conventional converters such as two-level or NPC, or through multilevel converters such as CHB or MMC. Multilevel converters do not require LV/MV transformer or ac filter, which increases the efficiency and reduces the footprint and cost. Different cell topologies for multilevel converters have been proposed in order to interface the batteries with the ac side, where the key performance indicators are the battery current peaks, number of semiconductors, footprint, efficiency and cost. This paper proposes a three-port full-bridge cell (TPC) to connect the battery in multilevel converters through a Model Predictive Control. This cell adds passive elements that decouple the battery from the cell capacitor, avoiding the battery current peaks, downsizing the cell capacitor and improving the footprint. Simulation and experimental results show that the power flow between batteries and the grid can be controlled keeping the cell capacitors balanced and ensuring the best battery treatment.
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    Trapezoidal Current Mode for Bidirectional High Step Ratio Modular Multilevel dc-dc Converter
    (IEEE, 2019) Pineda Fornerod, Cristian Andres; Pereda Torres, Javier Eduardo; Neira Castillo, Sebastian Felipe; Bravo, P.; Rodríguez, J.; Garcí­a, C.
    High voltage direct current (HVDC) transmission systems and low voltage direct current (LVDC) networks are becoming popular due to their advantages and present feasibility, mainly pushed by the advance in power electronics. However, one of the main drawbacks of dc networks is the lack of a dc-dc converter that performs as the ac transformer in terms of efficiency, reliability and high-step voltage ratio, specially in medium and high voltage. Modular multilevel converters are an attractive alternative because they can manage medium and high dc voltages with standard semiconductor devices, and they can achieve high efficiency with soft switching modulation, such as resonant, trapezoidal or triangular currents usually used in double active bridges (DAB). This paper proposes a novel generalized trapezoidal current mode applied to high step ratio Modular Multilevel dc-dc Converters. The proposed modulation increases the efficiency and achieves bidirectional control of the power, soft-switching and a natural balance of the voltage in the capacitors. The simulation results show the bidirectional operation and the capacitor voltage balance of the converter under different operating conditions with high efficiency (98.2%).