As a crucial part of cyber-physical systems, a digital twin can process data, visualize processes, and send commands to the control system, which can be used for the research on thermal power plants that are vital for providing energy for manufacturing and industry, and also daily consumptions. This article introduces the methodologies and techniques toward a web-based digital twin thermal power plant. To implement a web-based digital twin thermal power plant, the architecture, modeling, control algorithm, rule model, and physical-digital twin control are explored. The potential functionalities of the web-based digital twin including real-time monitoring, visualization and interactions, and provided services for physical thermal plants and universities are also presented. A case study has been provided to illustrate the web-based digital twin power plant. The research in this article can provide potential solutions for web-based digital twin research and education.

In this paper, a robust neighbor-based distributed cooperative control strategy is proposed for dc cyber-physical microgrids, considering communication delays and slow switching topologies. The proposed robust control strategy can synchronize the voltages of a dc microgrid to the desired value while achieving the optimal load sharing for minimizing distributed energy resources' (DERs) generation cost to achieve their economic operation at the same layer via a sparse communication network considering communication delays and slow switching topologies synchronously. The continuous interaction of physical-electrical and cyber networks generally exacerbates the occurrence of communication delays. Moreover, the arbitrary switching topologies could destroy the system's transient characteristics at the switching time instants. To further quantify these impacts on the system stability, the communication delay and average switching dwell-time-dependent control conditions for the proposed control strategy are proved based on the Lyapunov-Krasovskii theory. Some sufficient conditions for the exponential stability of the cyber-physical delayed-switching system are developed, which guarantees the robustness of the proposed strategy against the communication delays and dynamically changing interaction topologies. The proposed control protocols are shown to be fully distributed and implemented through a sparse communication network. Finally, several cases on a modified IEEE 34-bus test network are investigated which demonstrate the effectiveness and performance of the results.

This paper proposes a fault location method based on the adaptive control of neutral-to-earth complex impedance in a resonant grounded system, whose neutral grounds via an Electromagnetic Hybrid Petersen Coil (EHPC). The EHPC can be equivalent to a parallel circuit of a negative resistance and an inductance, both of which can be adjusted respectively. When a permanent single line-to-earth fault occurs, the ground-fault current will be compensated to almost zero, and the capacitance to earth and leakage resistance of system can be measured accurately for subsequent fault detection. Then, the complex impedance of EHPC is adjusted, and the faulty feeder and its faulted section can be identified online based on the characteristics that the measurements of zero-sequence admittances of points along faulty feeder change with system's neutral-to-ground complex impedance. The detection criterion is certain and unique, without comparing all the feeders. This paper also proposes an jitter adjustment and decoupling control of EHPC, which is adaptive to the grounding resistance and is repeatable, can ensure that the magnitude of zero-sequence parameter is large enough to be measured while without arc reignition, including in HIF states. Simulations and experiments verified the feasibility of this detection method and its control strategy.

In order to provide high and extendable power levels for inductive power transfer (IPT) system, a parallel multi-inverter system based on modular inverter is presented. Various power requirements can be implemented via adjustment of the number of paralleled inverters, which provide a high modularity. A master-slave scheme is employed for the switching-driver signals of parallel inverters, where one acts as a leader while others as followers. Despite of the master-slave scheme, the proposed circuit topology has natural robustness because of the equality in terms of the hardware configuration of each modular inverter. For proper parameters, the output phase (current lagging corresponding voltage) of an inverter is lower than the average of output phase of all inverters, when its output voltage lags behind others, and vice versa. Based on this approach, PI controllers are designed to implement phase synchronization for output voltages of all inverters. An IPT prototype supplied by the proposed parallel multi-inverter with 3 inverters was designed, built and tested. Experiments shown that the proposed parallel multi-inverter system has not only good circulating current suppression capacity, but also excellent performance of phase synchronization. The maximum DC-DC efficiency was 94% at a 35.1 kW receiving power. This paper is accompanied by a Matlab/Simulink file demonstrating phase synchronization control.

A multiphase inverter with phase-shifted control is proposed for the inductive power transfer (IPT) of EVs where the charging voltage can be regulated by adjusting the angle among the inverter phases. An equivalent circuit model is developed and linearized to analyze the system dynamic characteristics at its operating point. In terms of the high order model, a balanced model reduction method is used to remove the fast modes which are outside the desired system bandwidth and insignificant to controller design. In addition, the model is discretized and the communication delay of the feedback loop is considered in the discretized model. Based on this model, the parameters of a PI controller are designed to achieve the expected performance indexes. A 6.5 kW S-S compensation IPT system prototype with constant voltage control is built and tested to verify the control performance. The experimental results show that the charging voltage can be maintained constant within 6 ms and has no overshoot under disturbances, which verifies that the closed-loop system with PI controller operates properly and efficiently for IPT. Besides, the measured transmission efficiency of the system at a receiving power of 6.5 kW is 95.1%

This paper is to present the design, analysis and verification of a new hybrid wireless power transfer (HWPT) system, which has a space-saving coupler structure. The key of the design is to simplify two coupling capacitor plates into one single frame-shaped plate at each side. Then, the coupling coil for inductive power transfer (IPT) is embedded into the metal frame to form a compact hybrid coupler. Meanwhile, the coupling polarity between the coils is specified to realize the superposition of the inductive and capacitive coupling. As a result, the proposed HWPT system can offer a good comprise of efficiency promotion and a space-saving coupler structure simultaneously. To illustrate the system working principle, the equivalent circuit model is firstly derived. Then, a detailed analysis is conducted in terms of the reflected impedance. Consequently, the mechanism of the efficiency promotion can be clearly explained. Finally, a prototype is constructed with experiments, which validates the effectiveness of the proposed HWPT system. Results show that an efficiency increase of 14% over the pure IPT is obtained at 35 cm distance. Moreover, the effects of varying the resonant frequency are also carried out to instruct the practical system design.