This paper examines high-frequency disturbances in interconnected converters within dc microgrids, focusing on the effects of electromagnetic interference (EMI) filters and long interconnection cables. Understanding these phenomena is essential for systems with multiple power converters as it facilitates the identification and mitigation of voltage and current oscillations. The study investigates the beating effect in dc microgrids, providing an analytical derivation of the oscillation amplitudes at the beat frequency. It also explores how interactions between long cables inductive impedance and EMI filter capacitors can influence the system performance, distinguishing it from previous works. The study examines a dc microgrid consisting of two connected cascaded buck converters. Two scenarios are analyzed: one considers no filters between the two converters, while the other includes a low-pass filter (LPF), an EMI filter, and a cable feeder between them. The proposed theoretical models are validated using a 2 kW experimental prototype comprising two interconnected buck converters. In addition, the paper presents various strategies to mitigate the beating effect in dc microgrids, discussing their effectiveness and the associated implementation challenges.

This work presents a droop-based control strategy for a dc nanogrid designed to operate under the Net Zero Energy (NZE) concept, enabling seamless transitions between grid-connected and islanded modes. The nanogrid integrates photovoltaic (PV) generation, a fast electric vehicle charging station (EVSE), and a battery energy storage system (BESS) into a $700~$V dc bus interfacing with the ac grid via a bidirectional three-phase AC-DC converter. An isolated DC-DC converter establishes a secondary $48~$V dc bus for powering dc loads. An energy management system (EMS) defines an optimal day-ahead power dispatch for the BESS to meet NZE objectives. At the primary control level, a modified power-to-voltage droop strategy ensures accurate power tracking and parallel operation with the AC-DC converter. This approach enables continuous voltage regulation of the main bus under instantaneous power imbalances caused by schedule deviations or operational mode transitions. Additionally, the proposed strategy eliminates the need for secondary control or high-bandwidth communication. The system is validated through hardware-in-the-loop (HIL) simulations using the Typhoon HIL 604 platform, with the control strategy implemented on a DSP. Real-time simulation results confirm stable performance under various operating conditions, including transitions between modes.

This paper presents the validation of a voltage balancing converter for a bipolar DC microgrid designed to ensure reliable operation in both grid-connected and islanded modes. This microgrid includes unipolar constant power loads (CPL), a unipolar Battery Energy Storage System (BESS), and local PV generation. The BESS converter employs a V–I droop strategy using only inductor current feedback, reducing sensing requirements while maintaining plug-and-play capability and ensuring smooth transitions between connected and islanded modes. In such a microgrid, the voltage balancing converter regulates the differential voltages under severe unbalanced load conditions and during transients caused by changes in unipolar loads and sources. The experimental results validate the voltage balancing strategy across various scenarios in a small-scale prototype. The results show tight voltage regulation under unbalanced conditions, and smooth transitions during load transients and unintentional islanding, even if there is no dc voltage source in one of the poles of the bipolar dc bus. For both conditions, the imbalance between the unipolar voltages is less than 0.5% of the total bipolar voltage.

Este trabalho propõe utilizar uma estratégia de controle multivariável centralizada para um conversor CC-CC isolado de três-portas que irá figurar como o elemento integrador entre um sistema fotovoltaico, um banco de baterias e o barramento CC de um sistema de dessalinização. O conversor é representado através de um modelo multivariável de espaço de estados com 3 chaves do tipo MOSFET como entradas de controle; a tensão de saída e a corrente de magnetização como saídas controladas; e as tensões do painel fotovoltaico e da bateria como perturbações externas. A estratégia de controle é formulada usando-se a abordagem LQG com recuperação do ganho da malha de transferência (LTR) para garantia de estabilidade a um controlador de realimentação de estados com ação integral. As principais contribuições do trabalho são: (i) a aplicação, em eletrônica de potência, de uma estrutura de controle robustacentralizada de realimentação de estados, (ii) consideração dos distúrbios de entrada no sistema fotovoltaico e na bateria e (iii) uso do estimador de estados para a malha da corrente de magnetização. Por fim, resultados de simulação são apresentados e discutidos para validação do desempenho da abordagem proposta.

A dc microgrid comprises distributed energy sources and loads interconnected through a common dc bus via dc–dc converters. Their inherent switching behavior necessitates input filters to attenuate high-frequency components. However, interactions between cable impedances and converter filters can lead to high-frequency resonance, degrading bus voltage quality and system performance. This paper proposes a design-oriented mitigation approach for high-frequency resonance in dc microgrids. The method is based on a detailed analysis of the interaction between cable feeders and EMI filters, considering converter dynamic behavior and switching frequency effects. A damping strategy based on the optimal placement of an R–C branch is developed to suppress resonance and improve stability while ensuring compliance with voltage ripple limits derived from MIL-STD-704F. A key contribution of this work is establishing a direct relationship between cable length and the grid-forming converter switching frequency, providing practical design guidelines. This reveals that higher switching frequencies reduce the critical cable length required to trigger resonance, imposing more stringent constraints on dc microgrid layouts. The proposed approach is validated through analytical modeling, simulation results, and experimental tests on a 2 kW dc microgrid prototype, demonstrating significant reduction in high-frequency distortion and compliance with power quality limits.