Purpose Low-voltage renewable sources require substantial step-up conversion for bipolar DC microgrids, while their interfaces must suppress source-current ripple and prevent pole-voltage imbalance caused by parasitics. This paper aims to propose an interleaved coupled-inductor high-gain DC/DC converter with bipolar outputs. Design/methodology/approach The converter’s operating modes and steady-state characteristics are analyzed. Voltage gain, device stresses, input-current ripple and input-branch power sharing are derived, and a nonideal model incorporating component parasitics is established. A 400 W laboratory prototype verifies the operating principle and steady-state analysis. Findings Interleaving reduces the input-current ripple. The two main-switch gate signals remain 180° phase-shifted, while their duty cycles can be adjusted independently to regulate the total output voltage and compensate for the bipolar voltage deviation caused by the Mode-VII zero-current interval and component parasitics. The coupled-inductor and voltage-multiplier structure provides high voltage gain with low device voltage stress, and the topology retains a common input–output ground. Originality/value The converter combines unequal-duty-cycle interleaving, coupled-inductor high-gain conversion and bipolar output balancing. The independent duty cycles preserve the 180° phase displacement while enabling total-output-voltage regulation and bipolar voltage balancing. Clamp branches recover leakage energy and suppress switch-voltage spikes. In addition, S2 turns on under ZCS, while S3, S4 and S5 turn on and off under ZCS.
Purpose-The reliable integration of multiple renewable energy sources into autonomous DC microgrid requires effective power sharing to ensure stable operation. Conventional droop control schemes often face issues, such as loop current sharing and inadequate voltage regulation. This paper introduces an adaptive droop control strategy that dynamically tunes the control parameters to enhance the current distribution and suppress circulating currents under variable operating conditions. Design/Methodology/Approach-The strategy uses an adaptive droop coefficient tuned through a modified Droop Index (DI), improving response under varying loads. A 96 V, 1.5 kW solar-battery-based autonomous DC microgrid is modeled and simulated in MATLAB/Simulink along with realtime experimental simulator to validate the approach for four operating scenarios. Findings-The findings indicate that the proposed approach confirms a substantial enhancement in current sharing accuracy and suppresses circulating currents compared to conventional droop control. It maintains DC bus voltage to 96 V during dynamic load variations, ensuring stable and reliable operation. Practical implications-This approach eliminates circulating currents and improves power sharing in real-time DC microgrid systems. Social implications-Enhanced microgrid reliability promotes clean energy access and resilience for communities transitioning to renewable power. Originality/value-This study introduces a DI-based adaptive droop strategy that dynamically adjusts droop coefficients in real-time without requiring high-bandwidth communication among converters. The proposed method simultaneously improves current-sharing accuracy and minimizes circulating currents, and its effectiveness is validated through both simulations and real-time hardware-in-the-loop testing using the OPAL-RT platform.
Purpose This study aims to investigate the effects of parasitic-parameter-induced sneak circuits on the stability and bifurcation behavior of the Buck converter, and to overcome the limitations of conventional ideal or weak-parasitic models in describing practical dynamic behavior and stability boundaries. Design/methodology/approach A three-mode piecewise state-space model is established, where the sneak-circuit mode is represented by an equivalent LCR network. A discrete-time mapping and Filippov monodromy matrix are derived for stability analysis. The bifurcation and stability characteristics of the proposed model are compared with those of the conventional discontinuous conduction mode (DCM) model, and experimental validation is conducted. Findings Sneak circuits are not simple parasitic disturbances but introduce additional dynamics that reconstruct the cycle-to-cycle mapping. This leads to changes in eigenvalue evolution, bifurcation boundaries and stability regions. The proposed model provides more realistic predictions and shows a delaying effect on complex bifurcations compared with the conventional DCM model. Research limitations/implications The study focuses on a Buck converter under proportional voltage-mode control and does not consider more complex control strategies or active suppression methods. Future work can extend the analysis to broader operating conditions and advanced control schemes. Practical implications Designs based solely on conventional DCM models may overestimate the stable operating range. The proposed model provides a more accurate basis for parameter tuning and helps ensure sufficient stability margins in practical applications. Social implications Improved stability analysis of the Buck converter enhances the reliability of power conversion systems used in processors, data centers and vehicular electronics, reducing the risk of instability and improving system safety. Originality/value This work integrates sneak-circuit mechanisms into nonlinear stability analysis of the Buck converter. The proposed model reveals how parasitic-induced dynamics reconstruct operating modes and stability boundaries, providing a new perspective and tool for practical converter design.
Purpose This paper aims to address stability issues from dynamic short-circuit ratio (SCR) variations caused by high distributed energy penetration. The limitations of soft open points using single control strategies, which are challenged by varying grid strengths, are overcome and severe transients experienced during direct control mode switching are mitigated. Design/methodology/approach An adaptive smooth-switching control strategy based on dynamic SCR identification is proposed. First, small-signal models under two control modes are established, and the stable operating boundaries are analyzed. Second, a nonintrusive impedance identification method using secondary-side virtual disturbance is introduced for real-time SCR estimation. Finally, continuous phase angles and current references during transitions are ensured by a switching mechanism incorporating phase pre-synchronization and state tracking. Findings Simulation and experimental results demonstrate that real-time SCR variations are accurately identified by the proposed method. Disturbance-free, zero-deviation smooth switching between grid-following and grid-forming modes during transitions across strong and weak grids is enabled, whereby severe voltage/current transients and power fluctuations are effectively eliminated. Originality/value The need for extra hardware injection is eliminated by the nonintrusive SCR identification via virtual disturbance. Furthermore, combined with the pre-synchronization loop, an active, impact-free transition mechanism is provided, by which the adaptive support capability and operational robustness of flexible distribution networks are significantly enhanced.
Purpose The sliding mode observer (SMO) exhibits excellent dynamic performance and robustness, making it widely used in motor control applications. However, traditional SMOs suffer from issues such as chattering and higher-order harmonics, which significantly reduce their observation accuracy. This paper aims to tackle the above drawbacks by proposing a two-stage filtered SMO based on a fourth-order generalized integrator (FOGI). Design/methodology/approach By replacing the conventional low-pass filter (LPF) in the SMO with a FOGI, higher-order harmonics can be effectively eliminated, thereby considerably improving observation accuracy. Moreover, the FOGI has no phase shift at the central frequency, which eliminates the need for additional phase compensation. Using a two-stage filtering approach, information from the first-stage filter is fed back into the observer, while the second stage filtered information is used as input to a phase-locked loop. Findings Simulation and experimental results demonstrate that the proposed two-stage FOGI-filtered SMO effectively suppresses chattering and significantly improves position observation accuracy. Originality/value A FOGI-based two-stage filtered SMO has been developed to improve rotor position and speed estimation in sensorless PMSM control. By replacing the conventional LPF with a FOGI and introducing adaptive center frequency tuning and two-stage filtering, the observer achieves enhanced harmonic suppression, improved dynamic performance and reduced chattering. Simulation and experimental results confirm significant reductions in back-EMF harmonics, electrical angle error and speed estimation error, with faster transient response and halved speed fluctuation.
