With the continuous increasing requirement of dc power generations and dc electrical equipment, dc microgrids (MGs) show great natural advantages and development potential. In this paper, aiming at optimal sizing method of distributed generations (DGs) in the dc MGs, the output and capacity of photovoltaic units, wind turbine units, and an energy storage system (ESS) are presented based on the components structures and operation characteristics of the dc MGs. Due to the feature of the dc MGs that demands grid-connected converter (GCC) to exchange power with ac grid, the operating status of GCC and on-grid price are taken into account in the economic objective functions of the dc MGs. Meanwhile, with constraints including battery state of charge, loss of power supply probability (LPSP), renewable energy efficiency (REE), and so on, a particle swarm optimization algorithm is adopted to calculate the optimal sizing results targeting at the lowest annualized capital cost and operation & maintenance (O&M) cost. Furthermore, based on the analysis of the operation schemes of the dc MGs and the dynamic lifespan estimated results of ESS, an optimal sizing approach with comprehensive consideration of system operation modes and operation targets of the dc MGs is proposed. The variation trends of annualized capital cost and O&M cost are investigated under different LPSP and REE. Meanwhile, the system operation schemes are validated by using the obtained results, and the comparison and analysis of the detailed results are conducted.

A three-port converter (TPC) as a compact dc/dc energy conversion unit can effectively integrate renewable energy sources (RESs) and energy storage units (ESUs) into dc microgrids (MGs). In this paper, a series-resonance-based isolated TPC is developed to integrate photovoltaic (PV) and ESUs into dc MGs. A hardware decoupling approach using a series-connected capacitor in the half-bridge of the isolated TPC is proposed and studied. The decoupled power flow model among different ports is derived based on the equivalent circuit model of the converter, and the power transmission principle of the resonant circuit is analyzed. On this basis, considering the characteristics and operation modes of PV and ESU, which are connected at the two input ports of the TPC, a unified autonomous control method based on minimum value competition logic is proposed to coordinate the operation of PV and ESU, and achieve voltage regulation of the common bus in dc MGs. Simulation and experimental results are obtained in different test scenarios to demonstrate the effectiveness of the power decoupling effect and the proposed control method.

DC microgrids (MGs) have gained significant attention for its remarkable advantages of integrating renewable energy sources (RESs) and electronic loads. In order to improve the operational performance of the DC MG in both steady and transient states, a fully distributed fixed-time based secondary controller is proposed to remove the DC voltage deviation and provide proportional current sharing simultaneously. The secondary control of each DG consists of a fixed-time consensus-based current and voltage regulators that use relative information from the neighboring DGs through a sparse communication network. In contrast to the existing controllers, the proposed controller is distinguished with its accelerated convergence time which does not rely on the initial values. Besides, the stability of the proposed method is verified through the Lyapunov function. A simulation model is built in PLECS to prove the effectiveness of the proposed control strategy. Some scenarios are introduced to validate the link-failure resiliency, plug and play capability, the scalability, and the feasibility under various time delays. Meanwhile, a DC MG experimental prototype is built to verify the controller performance.

This paper addresses a fully distributed hierarchical coordination controller, which minimizes the global total generation cost (TGC) for a cluster of DC microgrids (MGs) through handling the optimal power-sharing between MGs. It consists of local and global tertiary controllers, in which a two-layer communication network is modeled to share information with a reduced complexity as one or some distributed generators (DGs) of each MG are pinned from the local network to broadcast the information between MGs at the global network. Under this control structure, the global tertiary controllers, based on dynamic consensus technique, generate the global optimum incremental cost (IC) reference to attain the entire cluster's economic operation. Moreover, using pinning-based leader-follower consensus algorithm, the local tertiary controllers assign MG average voltage reference at which the ICs of all DGs are matched at the global reference to ensure optimal operation of the cluster with considering DGs generation boundaries. Finally, the nominal voltage set points of each DG can be determined by the secondary controller to guarantee the generation-demand power balance. The feasibility of the proposed controller is demonstrated by simulation and experiment under various test scenarios.

Silicon carbide (SiC) power electronic devices feature the advantages of fast switching speed, low conduction loss, and reliable operation in high temperature environment, etc. Due to the differences of parasitic parameters and threshold voltage between SiC mosfets and Si mosfets, crosstalk problem is easy to be triggered when SiC mosfets are applied to bridge topologies. In this paper, the crosstalk effect with different parasitic parameters of SiC mosfets is firstly analyzed, and then an improved active crosstalk suppression method for high-speed SiC mosfets is proposed. By using the proposed method, when the crosstalk occurs, the crosstalk voltage will be decreased by reducing the equivalent gate resistance and increasing the equivalent gate-source capacitance in an active way. Consequently, the crosstalk problem can be suppressed without affecting the switching speed. To verify the effectiveness of the proposed method, a prototype of a buck-boost converter is built and the proposed modified gate driver is applied to the half-bridge topology. Comparative experimental study is conducted and the crosstalk voltage is analyzed. The experimental results verify that effective crosstalk suppression is achieved.

This paper presents a fully distributed finite-time control strategy to optimize the load power dispatch of islanded DC microgrids (MGs) in a finite-time manner. In which, based on the finite-time consensus protocol, a power optimizer is developed to realize MG’s optimal operation by matching the incremental costs (ICs) of all the distributed generators (DGs) within a finite settling time. Moreover, the finite-time voltage regulator restores the average voltage across the MG to preserve the power balance among generation and demand. The developed controller achieves an improved performance with an accelerated convergence rate, which is important for MGs with a high penetration level of renewable distributed generators (RDGs), over the conventional distributed secondary controllers. The convergence of the proposed controller is confirmed by a thorough analysis. The performance of the developed controller is validated through simulation and experimental results under different case studies.