A CLLC converter is a high-frequency, high-efficiency, isolated bidirectional DC/DC converter that is widely used in DC microgrid applications. The typical topology and basic working principle of CLLC converters are introduced herein. Subsequently, both analysis methods and control technologies are reviewed. On the one hand, several steady-state analysis models are listed, consisting of a harmonic approximation-based model in the frequency domain and a state equation-based model in the time domain, and some initial dynamic models are also included. On the other hand, numerous new control technologies are presented for different targets, such as soft startup control methods from a safety perspective, synchronous rectification (SR) control methods for efficiency optimization, highly dynamic control methods for better performance, bidirectional switching control methods, and wide voltage gain control methods aimed at popular vehicle-to-grid (V2G) and electric vehicle (EV) charging application scenarios. Finally, the future evolution of CLLC resonant converters is discussed.

This paper introduces a novel fully distributed economic power dispatch (EPD) strategy for distribution networks, integrating dynamic tariffs. A two-layer model is proposed: the first layer comprises the physical power distribution network, including photovoltaic (PV) sources, wind turbine (WT) generators, energy storage systems (ESS), flexible loads (FLs), and other inflexible loads. The upper layer consists of agents dedicated to communication, calculation, and control tasks. Unlike previous EPD strategies, this approach incorporates dynamic tariffs derived from voltage constraints to ensure compliance with nodal voltage constraints. Additionally, a fast distributed optimization algorithm with an event-triggered communication protocol has been developed to address the EPD problem effectively. Through mathematical and simulation analyses, the proposed algorithm's efficiency and rapid convergence capability are demonstrated.

Phase-shift (PS) dual-active-bridge (DAB) interlinking converters (ILCs) exhibit considerable potential in linking DC buses. DC ILC control research is focused on addressing three issues, namely modular series–parallel connection, control adaptability in various microgrid-operation modes, and microgrid stability with constant power loads. However, PS DAB converters operating with open-loop control cannot maintain bus voltage when load changes. Based on the open-loop controlled resonant converters which are called DC transformers (DCXs), this study proposes a closed-loop dc-transformer (CL-DCX) control method for DAB ILCs. In conventional control techniques, specialized control loops are used for addressing each control issue. It is hard to combine these loops to address all three control issues simultaneously. By contrast, the CL-DCX control method is simple and can address all three control issues simultaneously. The proposed CL-DCX control method is conducive for implementation in independent microgrids and may benefit medium-voltage applications because of its versatility and simplicity.

The equilibrium between dc bus voltage and ac bus frequency (Udc-f equilibrium) is the algorithm core of unified control strategies for ac-dc interlinking converters (ILCs), because the equilibrium implements certain mechanism. However, what the mechanism is has not been explicitly explored, which hinders further studies on unified control. This paper reveals that the state-space model of a Udc-f equilibrium controlled ILC is highly similar to that of a shaft-to-shaft machines system. Hence a detailed mechanism is discovered and named “virtual shaft-to-shaft machine (VSSM)” mechanism. A significant feature of VSSM mechanism is self-synchronization without current sampling or ac voltage sampling.