With the increasing penetration rate of renewable energy in China’s power system in the future, the stability of the system will face more severe challenges. Long-term energy storage technology plays an important role in balancing grid demand, improving grid stability, promoting the consumption of renewable energy, and promoting green and low-carbon development in the power system. Long-term energy storage has a wide range of application scenarios on the power supply side, grid side, and load side of the system, which is of great significance for the development of China’s new power system. Firstly, the characteristics and development trends of the current new power system are introduced, and the supporting role of long-term energy storage technology in the new power system is analyzed. Then, the technical principles and routes of five long-term energy storage technologies, such as the compressed air energy storage, lithium-ion battery energy storage, liquid flow battery energy storage, molten salt energy storage, and hydrogen energy storage, are summarized. The advantages and disadvantages of various long-term energy storage technologies are also analyzed. Finally, the future application prospects of long-term energy storage technology in the new power system are discussed.

Latent heat thermal energy storage technology can realize recovery and supply of heat during solid-state hydrogen storage and release process, achieving self-thermal balance inside the solid-state hydrogen storage tank, and improve the hydrogen storage and release performance. For horizontal tube and shell latent heat thermal energy storage exchanger, a new movement method where the inner tube is placed eccentrically to rotate around the central axis is proposed. By the Fluent software, the user-defined function UDF is written using the dynamic mesh technique, and the influence of eccentric distance and rotation velocity of the inner tube on heat storage performance is focused. The results show that, compared with the conventional static arrangement of the central inner tube, the rotation movement of the eccentric inner tube can improve the heat storage performance significantly. The heat storage time reaches the shortest when the eccentric distance is 9 mm and the rotation velocity is 0.10 r/min, namely decreases by 92.16%, and the time average heat storage rate increases by 11.51 times. The heat storage time reduces by 13.57% when the eccentric distance is 9 mm and the rotation velocity is decreased from 0.30 r/min to 0.1 r/min, it decreases by 70.48% when the rotation velocity is 0.10 r/min and the eccentric distance is increased from 3 mm to 9 mm. The study results can provide a new idea for performance optimization of horizontal shell and tube latent heat thermal energy storage exchangers in hydrogen storage field.

Virtual Synchronous Generator (VSG), as one of the primary technologies in grid-forming controls, provides inertia support to the power grid. However, due to the limited capacity of individual converters, when larger inertia support is required, multiple VSGs must run in parallel, making the coordinated control of multiple VSGs a subject of significant interest. In this regard, a state-space model for multiple VSGs in parallel is established, and the system stability is analyzed through the eigenvalues of the state variable matrix. Concurrently, a coordinated control strategy for multiple VSGs based on model predictive control is proposed, which introduces the angular frequency deviation and power angle difference as performance indicators to design the objective function. The optimal active power increment required is solved, and the output angular frequency is dynamically adjusted through the power-frequency coefficient, enabling active support for the output frequency and effectively suppressing system frequency fluctuations caused by VSG paralleling, thus the grid stability is enhanced. The results indicate that, compared with the conventional VSG paralleling systems, the proposed MPC-VSG parallel control method can shorten the transient response time of the system and improve its robustness under transient conditions. The simulation result confirms the effectiveness of the proposed approach.

The impedance inside weak current network is large, and when unbalanced loads are connected, it is unable to maintain the stability of its own voltage, resulting in three-phase voltage imbalance and output power fluctuations. Virtual synchronous generator (VSG) technology, as a grid-forming control, can provide support for voltage of the weak current network. However, under the connection of unbalanced loads, the VSG technology cannot maintain output voltage balance. To solve this problem, an improved VSG sequence decoupling control strategy is proposed. Firstly, the principle of three-phase imbalance and power fluctuation in VSG output voltage caused by unbalanced load connection is investigated. Secondly, a dual synchronous coordinate system decoupling (DDSRF) is adopted to separate the positive and negative sequence voltages of the power grid, and a positive and negative sequence control strategy is employed to control the negative sequence voltage component in dq rotating coordinate system. Finally, a VSG simulation model is built and the simulation results indicate that the proposed improved VSG sequential decoupling control strategy can suppress the unbalanced voltage output of the VSGs.

Against the conflict between carbon emission and operation cost in integrated energy systems, a multi-objective optimal scheduling method for wind-solar-thermal-storage integrated energy system considering carbon capture is proposed. It explores how carbon capture equipment affects the renewable energy consumption, carbon emissions, and operating costs. Taking the electric load data of a typical day in a specific area as a reference and the improved IEEE 30-bus system as the example, the system economy is optimized. The results show that, compared with the wind-solar-thermal and wind-solar-thermal-storage scenarios without carbon capture, the operating costs of the integrated energy system considering carbon capture reduces by 5.19% and 2.86% respectively on typical days, and the carbon emissions decrease by 1 159 t and 1 013 t, respectively. The consumption rate of wind and solar power generation increases by 5.01% and 2.82%, respectively. Moreover, with the minimum system operation cost and carbon emissions as the optimization objectives, the non-dominated sorting genetic algorithm II is used for multi-objective optimization, and the system scheduling optimization scheme under different target weights is obtained by combining with the linear weighted sum method. The study finds that, increasing the weight of carbon emission target reduces the carbon emissions but raises the system operation costs and the cost per unit of carbon emission reduction. Specifically, when the target weight of carbon emissions rises from 0 to 0.5, the carbon emissions decrease by 5 159 t and the operating costs increase by 205 466 yuan. The carbon emission reduction cost per unit increases the least when the target weight shifts from 0.4 to 0.5. The most significant emission reductions occur when the target weight is within [0.2, 0.4]. The multi-objective optimal scheduling method considering carbon capture proposed above provides a reference for decision makers when weighing system carbon emissions and operating economy.

To address the problem of grid connection failure caused by low frequency and voltage stability in power system during pre-synchronization process of grid-forming converters, a pre-synchronization control strategy for grid-forming converters based on improved linear active disturbance rejection control (LADRC) is proposed. Firstly, the phase locked loop (PLL) control strategy is used to synchronize the phase and amplitude of the grid voltage with the feedback control of phase deviation, which can avoid the stability problems caused by low precision of the PLL and the slow response speed. On this basis, introducing LADRC in angular frequency output of the active frequency branch module can effectively suppress the frequency oscillation of the system, so as to ensure the normal pre-synchronization process of the grid-forming converter and realize successful grid-connection. Finally, on the MATLAB/Simulink simulation platform, a pre-synchronization control model for grid-forming converters based on improved LADRC is established verified through simulation. The results show that, the proposed strategy can effectively suppress the system frequency oscillations and accelerate the pre-synchronization process of the system, ensuring safe operation of the grid-forming converter and ultimately achieving successful grid connection. The simulation results verify the effectiveness of the proposed method.

Integrated wind storage system, namely the wind power generation equipped with energy storage, has a black-start capability, which can be controlled to use the system as a black-start power source. On this basis, a black start program for the integrated wind storage system is developed based on a single wind turbine. Firstly, the energy storage device is started through grid-forming control, and to avoid the self-excitation generated by excitation inrush or resonance in the process of transformer input, the inertia link is added based on the original voltage-loop control to realize soft-start strategy. Then, the energy storage system establishes the AC frequency and voltage to realize restoration of the wind turbine generators and the loads. After the wind-storage integrated system is stably started, the electrical energy is transmitted to the 35 kV busbar through the main transformer and transmission line, to complete the black start process. Finally, a simulation model of the integrated wind-storage system is built on the PSCAD/EMTDC platform to validate the black-start scheme using the soft-start strategy, which keeps the voltage stable and the power balanced, and completes the start-up of the system, and at the same time suppresses the excitation inrush current effectively.

A combined reactive power control strategy for permanent magnet direct-drive wind turbine and distributed hybrid energy storage system is proposed. Firstly, the reactive power regulation capability of the permanent magnet direct-drive wind turbine and energy storage system is analyzed, and it is determined that both the wind turbine and energy storage system can participate in reactive power regulation through converter control. Secondly, the reactive power control strategy is put forward, which is presented in terms of signal reception, initial allocation, and internal allocation. In initial allocation, the equal margin allocation method is adopted. In internal allocation, the proportional allocation with the priority output of energy storage is considered. Finally, the effectiveness of the strategy is verified by simulation, it shows that the power grid voltage can be supported by fully utilizing the reactive capacity of the wind turbine and energy storage system.

With the increasing proportion of new energy in power grid system, the domestic capacity of peak regulation, frequency regulation and voltage regulation is increasing, which greatly affects the flexibility of the power grid. In this regard, the focus is on analyzing and researching the related fields of grid-forming energy storage. Firstly, the technical characteristics of grid-following and grid-forming control are compared and analyzed, and the development status of grid-forming energy storage in Xinjiang is summarized. At the same time, a demonstration project of a grid-forming energy storage power station in Xinjiang is selected to test the low voltage ride-through, inertia response and damping characteristics, and a grid-connected test method for grid-forming energy storage power stations covering multi-level and full-scale scenarios is proposed. The test results can provide reference for grid-connected performance evaluation of grid-forming energy storage. Finally, the development of grid-forming energy storage in Xinjiang is predicted and analyzed, and the development advantages of grid-forming energy storage in new energy-rich areas are summarized.

The use of grid-forming inverters for grid-connection of photovoltaic units is the key to stable operation of the new energy grid in desert and gobi. The conventional PV load-shedding operation is greatly affected by irradiance and inaccurate power retention. To solve these problems, a PV active standby control strategy based on grid-configuration inverter is proposed. Firstly, a PV grid-connected structure containing reference and backup arrays is designed. Secondly, based on the two-stage PV topology, an active backup control is introduced at the front stage DC/DC and a grid-forming control strategy is introduced at the back stage DC/AC to realize active participation of PV units in grid frequency regulation. The control strategy introduces a constant DC capacitor voltage control to maintain the DC voltage while enhancing the inertia characteristics of the PV unit. Finally, the PV small signal model of the grid-forming inverter is established, and the influence of DC capacitor value on the PV frequency response is analyzed through the root trajectory. The simulation results verify the correctness and feasibility of the proposed control strategy.