Browsing by Author "Siwakoti, Yam Prasad"

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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.