Online SoC Balancing Strategy for Distributed Single-Stage MMC-Based BESS

Coordinated State-of-Charge Balancing and Energy Management for a DC Microgrid Under Dynamic Renewable Conditions

This paper presents an energy-management and state-of-charge (SoC) balancing scheme, denoted OEMSS, for a DC microgrid comprising photovoltaic generation, a fuel-cell source, two energy storage systems (ESSs), and six household loads. A demand-driven power-allocation layer first determines whether generation is sufficient, ESS support is required, or priority-based load scheduling must be activated. A supervisory balancing layer then allocates the fleet charging or discharging request by using a capacity-weighted average SoC and separate mode-dependent correction laws. The balancing command is dimensionally expressed as an energy-capacity deviation divided by the control interval and is projected onto the SoC and power limits. A Python simulation driven by recorded generation profiles is used to evaluate four seasonal operating conditions. In the tested equal-capacity case, the maximum inter-ESS SoC deviation is reduced from 18% to 4.8%, synchronization is reached within approximately 2 to 4 h, and simulated over-discharge events are avoided. The reported increase from 45% to approximately 70% is interpreted as a 25-percentage-point increase in the ESS storage contribution rate, rather than an increase in conversion efficiency. During shortage intervals, the retained priority demand is supplied, whereas satisfaction of the original uncurtailed demand is not claimed. A discrete-time Lyapunov analysis gives the nominal convergence condition 0<γb<2, and the online implementation has O(J+K+H) time complexity. The study provides simulation evidence for a simple coordinated allocation rule; hardware performance, battery-life extension, converter-level stability, and global optimality remain to be established.

Adaptive Control of Dual-Phase Bidirectional Flyback Converters for Efficient Cell Balancing in Lithium-Ion Battery Packs: A Comprehensive Review

The intensive development of electric vehicle (EV) technology, renewable energy systems, and stationary energy storage solutions has amplified the demand for advanced Battery Management Systems (BMS). The imbalance in cells within lithium-ion battery packs, due to manufacturing tolerances, varying aging, and thermal gradients, reduces available capacity, cycle life, and can cause thermal runaway. Active charge equalization with DC–DC converters has become a recent research focus among various balancing techniques because it has a better capability of redistributing energy. This paper gives a detailed study of converter-based cell-balancing topologies with a specific focus on the bidirectional flyback converter and the interleaved two-phase variant. Non-isolated topologies (buck–boost, Cuk converter topology, interleaved buck–boost) and isolated topologies (flyback, push–pull, dual-active bridge, LLC resonant) are compared concerning functional efficiency, component reduction, galvanic isolation, scalability, and bidirectional capability. The concept of soft-switching, including zero-voltage switching (ZVS) and zero-current switching (ZCS), and their circuit realizations are discussed. Advanced control models and artificial intelligence (AI) for the estimation of state-of-charge (SoC) and real-time optimization are mentioned. Thermal issues, scalability, reliability, and wide-bandgap semiconductor devices (SiC/GaN) are discussed.

Effective Energy Management Framework for Standalone Photovoltaic Fuel Cell Direct Current Microgrid without Auxiliary Storage Devices

The objective of this paper was to propose an effective energy management framework for a standalone Photovoltaic–Fuel Cell Direct-Current (PV–FC DC) microgrid without auxiliary storage devices using an appropriate standard control strategy. The proposed framework demonstrates that accurate source sizing combined with coordinated power balancing can inherently maintain DC bus voltage stability through real-time generation–load equilibrium. The PV array operates as the primary energy source under high irradiance conditions using a perturb and observe, P&O algorithm for maximum power point tracking. This is then combined with a PEMFC subsystem, interfaced through a two-phase interleaved boost converter that compensates for power deficits during low solar availability. The EMS continuously evaluates the instantaneous power mismatch and generates a reference current for the fuel cell to restore equilibrium without centralized voltage reference enforcement. Simulation results under step irradiance variation demonstrate smooth source transition, negligible overshoot of <5% and tight DC bus regulation within ±1.25%. The findings confirm that DC bus stability can be achieved as a direct consequence of power balance rather than aggressive hierarchical voltage control. The proposed architecture eliminates battery storage, thereby reducing system complexity, cost, and maintenance requirements. Moreover, the EMS improves hydrogen utilization efficiency by activating the fuel cell only during periods of insufficient solar generation. As a result, hydrogen fuel is conserved and used strictly when a solar power deficit occurs. This operating strategy makes the system particularly suitable for medium power standalone applications such as remote telecommunication stations and rural electrification systems.

Coordinated Control Strategy for Distributed Energy Storage MMC Drive System Based on ESO-MPC and Hierarchical Equalization

High-power induction motor drives (e.g., mine hoists) based on DEMMC face severe energy imbalances and power surges under extreme dynamics. This paper proposes a hierarchical coordinated control strategy to address these challenges and ensure system stability under variable-speed, heavy-load conditions. An ESO-MPC framework is established for robust torque tracking and active disturbance rejection. A dual-layer State of Charge (SOC) balancing mechanism is developed, employing fuzzy-logic-based nonlinear gain for inter-arm regulation and a novel DO-CDPWM strategy for rapid intra-arm equalization. The approach is validated via MATLAB/Simulink. Simulation results demonstrate that the ESO-MPC has an ultra-fast current settling time of 2 ms (within a 2% error band) with negligible overshoot. The proposed balancing strategy suppresses intra-arm SOC deviation from 4% to 0.5% within 0.2s, while effectively eliminating second-order harmonic circulating currents. A coordinated control strategy integrating ESO-MPC and dual-layer SOC balancing is proposed for DE-MMC mine hoists. Simulations demonstrate a 1ms current response and rapid SOC equalization (4% to 0.5%) within 0.2s. This strategy decouples motor drive from energy management, ensuring stable operation under heavy-load conditions. The proposed strategy effectively decouples motor drive from energy management, offering superior dynamic performance and global energy equilibrium compared to traditional PIbased methods, making it highly suitable for high-power mining applications.

Three-Phase Photovoltaic System with Battery Energy Storage and Volt–VAR Reactive Power Support: Architecture Assessment and Integrated Control Proposal

The growing share of photovoltaic generation in power grids intensifies the need for converter architectures capable of combining efficient energy conversion, DC-bus stability, and ancillary service provision at the grid coupling point. This paper presents the modeling, implementation, and simulation-based evaluation of a 91 kWp three-phase photovoltaic (PV) system integrated with a battery energy storage system (BESS), developed in the PLECS environment. The proposed architecture comprises three interleaved Boost stages for maximum power point tracking (MPPT), a DC bus regulated at 600 V, three independent bidirectional buck–boost converters for LiFePO4 bank management, and a two-level three-phase voltage source inverter (VSI) with an LC output filter. The control is organized in cascade voltage–current loops for the DC–DC stages and in vector control within the synchronous reference frame (SRF) for the inverter, with synchronization via SRF-PLL. A C-Script supervisory block integrates the Perturb and Observe (P&O) MPPT algorithm, independent state of charge (SOC) estimation per bank via coulomb counting, and Volt–VAR reactive power reference generation with a dead band of 0.90–1.10 pu. Five scenarios are analyzed for validation: DC-bus regulation under irradiance transients; reactive power support during undervoltage and overvoltage events (0.80–0.85 pu and 1.15–1.20 pu); BESS operation as an active DC-link support element; and PV curtailment with fully charged banks. All five scenarios were additionally corroborated on a Typhoon HIL402 Pro 2 hardware-in-the-loop platform, reproducing the PLECS waveforms within the amplitude and timing resolution of the oscilloscope captures. Across all scenarios, the DC bus is held within ±15 V (2.5%) of the 600 V reference, with the worst-case transient recovering in 80–100 ms; under a sustained 9 s bidirectional disturbance, redirecting PV surplus to BESS charging in both the undervoltage and overvoltage segments—with no externally imposed active-current limit—keeps the current-vector magnitude id2+iq2 below the 335 A rating throughout (≈271 A and ≈242 A, respectively), while the available reactive margin Qdisp reaches ≈78– 80 kVAr in both segments and the bank SOC advances by ≈0.03 pu; and supervisory curtailment under a sustained overvoltage ride-through with a saturated bank keeps the per-bank SOC dispersion within 4×10−5 pu while expanding the available reactive margin Qdisp from ≈50 to ≈90 kVAr.

Battery charger/discharger for bipolar microgrids with synchronous bus voltage regulation