Jing Lu

A DVR based on superconducting magnet energy storage (SMES-DVR) could offer higher power in milliseconds to compensate for the voltage disturbance. However, nonlinearities and load disturbances of SMES-DVR usually induce voltage fluctuations on DC-link, which reduces the accuracy and response performance. A novel composite control strategy based on high-order sliding mode control with extended state observer (ESO-HOSMC) is proposed to address the critical challenge of DC-link voltage fluctuations in SMES-DVR. By synergizing extended state observer-based disturbance estimation with super-twisting high-order sliding mode control, ESO-HOSMC control method effectively balances the contradiction between rapid response and operational stability during the charging and discharging process of the superconducting magnet, while reducing total harmonic distortion of sensitive load voltage. Theoretical analysis containing controller modeling, designing and stability analysis has been demonstrated. In addition, performances among the ESO-HOSMC control, model predictive control (MPC) and conventional PI control of SMES-DVR have been compared under different voltage sag or swell scenarios. The results show that the proposed control scheme effectively elevates compensation performance and the stability of DC bus voltage for SMES-DVR.

With the ever-growing integration of renewable energy sources (RESs) into the power grid to meet escalating power demand, the intermittent and volatile nature of these sources poses significant challenges to the stability of power grid. To address the unstable output power resulting from the inherent randomness and fluctuation of RES, this paper introduces a novel cooperative control strategy designed for a photovoltaic-based grid-connected system. This proposed strategy leverages both battery energy storage system (BESS) and superconducting magnetic energy storage (SMES) within the hybrid energy storage system (HESS) framework. At top-level control (TLC), the control strategy employs a fuzzy control-based low-pass filter (LPF) to dynamically regulate filtration coefficient and realize transient power allocation optimization. Simultaneously, at the underlayer level control (ULC), a fast Model Predictive Control (MPC) method is implemented to maintain DC bus voltage by one-step prediction horizon. The feasibility and superiority of the proposed control strategy are systematically validated under diverse operating conditions, demonstrating its efficacy in enhancing the stability and performance of the grid-connected system.

Power impact frequently occurs during operation of shock loads, such as fusion devices, threatening the stable operation of the power system. Meanwhile, both short-time high pulse and long-time steady power exist, which have distinct time scales and amplitude characteristics. Currently, the capacity of power supply system is designed according to the maximum impulse power, causing the large redundancy and high cost. Aiming at this issue, hybrid power supply scheme based on energy storage technology with high power density provides a potential approach. However, little research focuses on the reasonable static configuration for different type of power supply. This paper presents the non-dominated sorting genetic algorithm (NSGA) algorithm to divide the two kinds of power, where impulse power can be treated by high-density energy storage and stable power is sustained by substation devices. In specific, taking the static investment and dynamic response of energy storage as the objectives, the critical optimal power can be determined. Finally, power scenario based on a typical Tokamak fusion device, international thermos-nuclear experimental reactor (ITER), is applied as case study of the proposed algorithm. The results show that the obtained crucial power can reasonably decrease the static capacity for substation to achieve the optimal economy and satisfy the mentioned objectives, providing the basis for other static capacity allocation circumstances and assisting accurate and high-efficiency smart control for power converters.

Megawatt-impulse power generated by Tokamak fusion devices seriously threats to the stable operation of the whole system. The current power supply scheme needs to leave large redundancy to suffer such a huge power impact, resulting in a high cost of the power supply system. Moreover, no reasonable configuration for impulse power and stable power causes unnecessary waste of power supply capacity. The rapid development of energy storage technology provides a potential approach to solve the operation stability problem caused by large amounts of power impact. Thus, a novel hybrid power supply scheme is creatively put forward with centralized energy storage, which can effectively decrease the voltage level of the grid and achieve smooth connection into the public grid when validly compensating for the impulse power. The cost evaluation model and principles are proposed to analyze and assess the economic advantages of the hybrid power supply scheme with centralized energy storage. Finally, a power scenario based on the international thermosnuclear experimental reactor (ITER) is applied as a case study of the cost evaluation model for various schemes, and the results verify that the novel hybrid power supply scheme has benefits on economics and the capacity of the grid over other schemes.

Tokamak is a promising device for using nuclear fusion energy, and the triggering of Tokamak power supply has the characteristics of extreme asymmetry and drastic instantaneous change, which bring spectrum-rich harmonics to the DC side of the power supply, threatening the operational safety of the device. Although the harmonic analysis method of the DC side already exists, however, it still has the problem of cumbersome and inaccurate calculation when it is oriented to fusion power systems with complex operation modes. Based on the three-phase unified switching function, this paper introduces delay factor, and establishes a non-linear function model of converter suitable for the case of asymmetrical triggering. According to the principle of the switching function method, the frequency domain equation of the proposed model is obtained, then combined with power grid parameters, the harmonic analysis of the DC side can be derived. The correctness of the theoretical analysis is verified by comparing the calculation results with the harmonic frequency spectrum data obtained by direct Fourier decomposition of the DC side voltage.

This publisher’s note contains a correction to Opt. Lett. 47, 1770 (2022)10.1364/OL.453113 .

With the rapid decreasing production cost of green energy and the increasing urgency to mitigate greenhouse gas emissions, hydrogen is receiving unprecedented momentum as a key energy transition pillar. The number of related policies and projects is expanding rapidly. China is highly dependent on energy-intensive and high-emission industries. Thus, clean hydrogen has become an irreplaceable tool to realize deep decarbonization in some hard-to-abate sectors. Hydrogen energy will have close interaction with the power grid in various forms, among which hydrogen electrolysers are considered to be the dominant way in the near future. In this study, different interaction modes between hydrogen electrolysers and the power grid are analyzed, based on which, the production costs of hydrogen are calculated and compared. Concerning existing issues, relevant suggestions to accelerate the development of clean hydrogen are put forward.