The Industrial Internet of Things (IIoT) is of great significance to the improvement of industrial efficiency and quality, and to reduce industrial costs and resources. However, there are few openly-reported practical project applications based on the IIoT up to now. For legacy automation devices in traditional industry, it is especially challenging to realize the upgrading of industrial automation adopting the IIoT technology with less investment. Based on the practical engineering experience, this paper introduces the automation renovation of a sewage treatment plant. The legacy automation devices are upgraded by the central controller of a STM32 processor (Produced by STMicroelectronics company, located in Geneva, Switzerland), and the WeChatApplet (Developed by Tencent company, located in Shenzhen, China) is used as the extended host computer. A set of remote monitoring and control systems of sewage treatment based on the IIoT is built to realize the wide-area monitoring and control of sewage treatment. The paper describes the field hardware system, wide-area monitoring and control application program, management cloud platform and security technologies in detail. The actual operation results show that the monitoring system has the requirements of high accuracy, good real-time performance, reliable operation and low cost.

As the largest global renewable source, hydropower is a useful supplement to mountainous distribution networks with abundant water resources, and shoulders a large portion of the regulation duty in many power systems. In particular, in the form of decentralized energy sources located to their customers, small hydropower (SHP) improve grid stability by diversifying the electricity system and reducing power loss. The mountainous distribution networks supplied by small hydropower are closed-loop design but open-loop operation, which easily causes the tripping of tie line even further the off-grid operation of small hydropower system. Once the tie line trips, the current countermeasures—such as hydropower shutdown and load shedding—do not fully guarantee the reliability of power supply and the utilization efficiency of hydropower. This paper studies the amplitude-frequency characteristics of SHP off-grid, according to the typical integration of hydropower in South China, a SHP on-grid/off-grid model is established based on the Power Systems Computer Aided Design (PSCAD) platform. It is found that due to the inertia of SHP, the amplitude-frequency characteristics of SHP island system are relatively slow, and the process of non-synchronization with the main grid is gradually expanded. The characteristic of SHP has a certain degree of synchronization with the main grid in the initial island operates stage, which helps to find a novel grid connection method. This paper further proposes the strategy of using fast busbar automatic transfer switch (BATS), which quickly connect the trip-off SHP to the distribution network under the condition of permitting distributed energy grid-connected. The PSCAD simulation results show that proposed strategy has a limited impact on the power grid and prove the effectiveness of the method.

Due to the diversity and complexity of distribution networks, the classical modular software development method may face the difficulty in modular division, data sharing and collaboration of different specialties. Inspired by the idea of separating the control plane from the data forwarding plane in software-defined networking (SDN), a method of power data virtual plane is proposed in this paper to improve software development efficiency. Layered processing of power data virtual plane is designed to meet the diversity characteristics of intelligent distribution network and the multi-source and heterogeneous characteristics of information. This paper introduces the design idea and implementation process of virtual plane in detail. The main component of the power data virtual plane, power data warehouse and application scheduling are presented. Finally, the performance of the proposed virtual plane method is verified by practical distribution network examples with different communication networks and information.

Direct current microgrid (DCMG) clusters are gaining popularity in power systems due to their simplicity and high efficiency. However, DCMG clusters are susceptible to minor disturbances due to low system inertia. This paper proposes a method to enhance the small‐signal stability of a DCMG cluster by optimizing the main control parameters of the system. This paper presents a small‐signal state‐space model of a DCMG cluster system at the system level, considering a multi‐bus network topology. Then, the control parameters that significantly affect the small‐signal stability of the DCMG are selected using the participation factor method. To enhance the system damping, the Pareto‐optimal frontier of the bi‐objective problem was determined using the elite non‐dominated sorting genetic algorithm (NSGA‐II). The optimal compromise is determined by using the fuzzy membership function method to extract it from the generated Pareto optimal front. The proposed method has been verified on a three‐sub DCMG test system with droop control.

DC microgrid (DCMG) is characterized by a high degree of power electronics, low system inertia, and CPL (CPL) with a negative damping feature. Its system-level transient stability is of great concern. The stability of a DCMG system is affected by many factors, such as component parameters, load types, converter control methods, etc. To analyze the system-level stability of the DCMG, the constraints of large signal stability of the DCMG based on droop control are derived by using the Lyapunov direct method. Based on this conclusion, the influence of system parameters on large signal stability and voltage deviation of the DCMG is revealed, and the optional range of filter element parameters and droop coefficient under the stability and voltage constraints is proposed. The parameter selection work involves two evaluation indicators, system stability, and voltage deviation. This article uses the variable weight coefficient method to normalize these two indicators into a comprehensive evaluation index, and the appropriate droop coefficient is selected based on the optimal comprehensive evaluation index. The work of this article has reference values for the parameter design of the DCMG system components and the selection of the droop coefficient.

DC microgrids are vital for renewable energy integration and distributed energy management, but their expanding scale and complex operation with diverse topologies expose critical limitations. These methods, primarily designed for simple single-bus structures, fail to coordinate voltage deviation suppression, system stability enhancement, and economic optimization effectively in multi-bus scenarios. To address this, a multi-objective optimization approach for DC microgrids (DCMG) with complex topologies is proposed. It integrates small-signal stability, bus voltage deviation, and operational economy into a unified framework, incorporates randomness of power generation and loads, and adapts to mesh topology with diverse node types. Case studies verify the method exhibits strong adaptability and robustness under stochastic scenarios, achieving balanced improvements in stability and economic efficiency: the system small-signal stability index is reduced by 19.3%, bus voltage deviation is lowered by 71.2%, and system power loss is decreased by 2.1%. This work provides key technical support for the efficient and reliable operation of DC microgrids with complex topologies, advancing their practical application in complex energy systems.