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Owing to the flawed design of the jumper cable between floating bodies, excessive bending, stretching, and collision with the floating bodies occurred during operation, thereby affecting the reliable operation of the system. To solve the problem of fatigue failure in cross-floating cables, this study proposes a method for interconnecting cables between multiple floating bodies in offshore floating photovoltaic systems. First, the structure of the floating body is analyzed, and the cable-jumper scheme between typical hexagonal floating bodies is determined. Second, by analyzing the influence of the floating body structure on the jumper scheme, the key parameters and limiting conditions in the design steps of the cable straddle float were determined. A method is proposed to meet operational requirements through the reasonable planning of jumper parameters, and a two-stage solution framework for cable jumper schemes is established. In the first stage, trust-region particle swarm optimization is employed to determine the feasible solution region of the spanning scheme variables. In the second stage, the maximum fatigue life in the feasible solution region is determined as the optimal solution. Finally, a cable jumper model was built using Orcaflex software to verify the proposed scheme, and the effectiveness of the proposed method was demonstrated through an example analysis. The research shows that through reasonable planning of the jumper cable path, the bending state of the cable can be alleviated to a certain extent, thereby reducing fatigue damage and ensuring reliable operation during the operational period. (1) Optimizing the jumper parameters through reasonable planning of the jumper path can improve the reliability of flexible cables in harsh environments. This approach achieves the desired effect while reducing both time and economic costs compared with the use of protection devices such as bending limiters. (2) Cosserat theory was used to accurately model flexible cables, fully considering the influence of cable structural parameters on linear lines. The maximum fatigue life was identified as the key focus in solving the framework presented in this study, which is consistent with the simulation results obtained using Orcaflex software. This demonstrates the feasibility and effectiveness of the proposed framework and solution method. (3) In the floating scenario, the solution for the cable jumper scheme should focus on the bending protection of both ends and the middle part. This can be achieved through the installation of protective devices or the reasonable selection of parameters, such as cable length and effective span, through careful analysis.

Abstract The rapid development of offshore wind farms (OWFs) calls for economical and reliable power transmission technology. This review paper focuses on the diode‐rectifier‐unit based high voltage direct current (DRU‐HVDC) transmission systems. The main technical features of DRU‐HVDC are highlighted and the comparisons with MMC‐HVDC and LCC‐HVDC are conducted. Considering the uncontrollability of DRU and the necessity of offshore wind turbines (WTs) to establish offshore network, the existing decentralized and centralized control strategies are reviewed in detail. For the fully‐grid‐forming converter, the operation principle of the P–V and Q–f power control is explained from the OWF‐DRU level and the WT level, respectively. For the partial‐grid‐forming converter, why the voltage control loop can be eliminated is analysed. Focusing on the start‐up issue caused by the unidirectional‐power‐flow characteristic of DRU, several start‐up solutions are reviewed, including medium voltage alternative current (MVAC) umbilical cable, auxiliary MMC, energy storage for WTs, auxiliary low voltage DC cable. Then considering different fault locations, the fault characteristic and protection of the DRU‐HVDC system is presented, including the offshore AC faults, DRU faults, HVDC faults and onshore AC faults. Finally, the future research topics worth exploring for DRU‐HVDC system are identified.

Abstract Constrained by the AC voltage amplitude modulated by a modular multilevel converter‐based static synchronous compensator (MMC‐STATCOM), its reactive power output may be subject to oscillations under grid contingencies, posing a threat to the grid stable operation. To solve this problem, this paper proposes a variable DC voltage (VDCV)‐based reactive power enhancement scheme for MMC‐STATCOM. In this scheme, a novel variable DC voltage control is designed, which can increase the DC voltage in a transient state for relaxing the constraint of the AC voltage amplitude modulated by MMC‐STATCOM and improving its reactive power output capability (RPC). At the same time, to make full use of the improved RPC of MMC‐STATCOM, a VDCV scheme also proposes an optimisation algorithm of its reactive current‐AC voltage droop coefficient using the established reactive power model of the MMC‐STATCOM. Based on small signal modelling and analysis, the key parameters of the proposed VDCV scheme are optimised. The performance and reactive power enhancement of the VDCV scheme is evaluated through the hardware‐in‐the‐loop experiment under grid disturbances.

With large-scale grid integration of renewable energy sources (RES), power grid operations gradually exhibit the new characteristics of high-order uncertainty, leading to significant challenges for system operational security. Traditional model-driven generation dispatch methods require large computational resources, whereas the widely concerned Reinforcement Learning (RL)-based methods lead to issues such as slow training speed due to the high complexity and dimension of processed grid state information. For this reason, this paper proposes a novel Grid Expert Strategy Imitation Learning (GESIL)-based real-time (5 min intervals in this paper) dispatch method. Firstly, a grid model is established based on the graph theory. Secondly, a pure rule-based grid expert strategy (GES) considering detailed power grid operations is proposed. Then, the GES is combined with the established model to obtain a GESIL agent using imitation learning by offline–online training, which can produce specific grid dispatch decisions for real-time. By designing a graph theory-based grid model, a model-driven purely rule-based GES, and embedding a penalty factor-based loss function into IL offline–online training, GESIL ultimately achieves high training speed, high solution speed, and strong generalization capability. A modified IEEE 118-node system is employed to compare the proposed GESIL to traditional dispatch method and RL method. Results show that GESIL has significantly improved computational efficiency by approximately 17 times and training speed by 14.5 times. GESIL can more stably and efficiently compute real-time dispatch decisions of grid operations, enhancing the optimization effect in terms of transmission overloading mitigation, transmission loading optimization, and power balancing control.

Abstract Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by excessive proliferation of rheumatoid arthritis synovial fibroblasts (RASFs) and accumulation of inflammatory cytokines. Exploring the suppression of RASFs and modulation of the RA microenvironment is considered a comprehensive strategy for RA. In this work, specifically activated nanoagents (MAHI NGs) based on the hypoxic and weakly acidic RA microenvironment are developed to achieve a second near‐infrared fluorescence (NIR‐II FL)/photoacoustic (PA) dual‐model imaging‐guided multi‐treatment. Due to optimal size, the MAHI NGs passively accumulate in the diseased joint region and undergo rapid responsive degradation, precisely releasing functionalized components: endogenous melanin‐nanoparticles (MNPs), hydrogen gas (H2), and indocyanine green (ICG). The released MNPs play a crucial role in ablating RASFs within the RA microenvironment through photothermal therapy (PTT) guided by accurate PA imaging. However, the regional hyperthermia generated by PTT may exacerbate reactive oxygen species (ROS) production and inflammatory response following cell lysis. Remarkably, under the acidic microenvironment, the controlled release of H2 exhibits precise synergistic antioxidant and anti‐inflammatory effects with MNPs. Moreover, the ICG, the second near‐infrared dye currently approved for clinical use, possesses excellent NIR‐II FL imaging properties that facilitate the diagnosis of deep tissue diseases and provide the right time‐point for PTT.

Abstract A supercapacitor‐based coordinated synthetic inertia (SCSI) scheme for a voltage source converter‐based HVDC (VSC‐HVDC)‐integrated offshore wind farm (OWF) is proposed. The proposed SCSI allows the OWF to provide a designated inertial response to an onshore grid. Under the SCSI scheme, a supercapacitor is added to the DC side of each wind turbine generator via a bidirectional DC/DC converter, varying its voltage along with the offshore frequency to synthesise the desired inertial response. The HVDC grid side VSC employs a DC voltage/frequency droop control to convey the onshore frequency information to DC voltage without communication. Meanwhile, the wind farm side VSC regulates the offshore frequency to couple with the conveyed onshore frequency, considering voltage drop across the DC cables. An offshore frequency switching algorithm is incorporated to avoid undesired SCSI maloperation under offshore faults. The key parameters of the proposed SCSI are optimised through a small signal stability analysis. The effectiveness of the SCSI scheme is evaluated using a modified IEEE 39‐bus test system. The results show that the proposed SCSI scheme can provide required inertial support from WTG‐installed supercapacitors to the onshore grid through the VSC‐HVDC link, significantly improving the onshore frequency stability.

Solar generation systems with battery energy storage have become a research hotspot in recent years. This paper proposes a grid-forming control for such a system. The inverter control consists of the inner dq-axis current control, the dq-axis voltage control, the phase-locked loop (PLL) based frequency control, and the DC voltage control. The proposed control embeds the PLL into the grid-forming inverter control, offering the advantages of better synchronization and fault current-limiting capability. With the proposed control, the battery energy storage is able to provide inertial and primary frequency support during the grid frequency disturbance. Simulation models are established in PSCAD/EMTDC, and the results during the active power variation and AC voltage variation, the grid frequency disturbance, grid fault, and mode switch validate the effectiveness of the proposed control.

Abstract System kinetic inertia is declining due to the rapid replacement of synchronous generators (SG) by renewable power generations (RPG). To maintain grid inertia, this paper proposes a generic synthetic inertia (GSI) scheme for RPGs, enabling inertial response by a supercapacitor (SC) bank integrated with a voltage source inverter (VSI) DC link via a DC/DC converter. A GSI control loop is developed for the DC/DC converter controller to vary the SC voltage along with the grid frequency for power exchange following the SG swing equation. The GSI scheme realizes plug‐and‐play advantage without modifying the RPG original system. Small‐signal stability analysis is carried out to optimize the GSI controller parameters. The performance of the GSI scheme is evaluated using a modified IEEE 39‐bus test system.

Experimental and numerical experiments were carried out to study the coffee rings or coffee splats formed by droplet evaporation with micro or nano polystyrene sphere particles (Dp = 10 μm or 100 nm). Particle image velocimetry (PIV) and a high-resolution camera were used in this experiment, along with a temperature-controlled heater and a data-acquisition computer. The results showed that a nano particle could form a homogeneous coffee splat, instead of the common coffee ring formed when using micro particles. In order to account for this phenomenon, this paper developed a complex multiphase model, one which included the smooth particle hydrodynamics (SPH) fluid model coupled with the van der Waals equation of state for droplet evaporation, the rigid particle model of finite-size micro particles, and the point–particle model of the nanometer particles. The numerical simulation was operated on a GPU-based algorithm and tested by four validation cases. A GPU could calculate 533 times the speed of a single-core CPU for about 300,000 particles. The results showed that, for rigid solid particles, the forms emerged spontaneously on the wall, and their structure was mainly affected by the boundary wettability, and less affected by the fluid flow and thermal condition. When the wall temperature was low, it was easier for the particles to be deposited on the contact line. At high wall temperature, the coffee ring effect would be weakened, and the particles were more likely to be deposited in the droplet center. The hydrophilic surface produced a larger coffee ring compared to the hydrophobic surface. The experimental and numerical results proved that particle size could play a significant role during the particle deposition, which may be a possible route for producing uniform-distributed and nano-structure coatings.