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.

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.

To address the frequency fluctuations and exceeding limits caused by load changes when wind hydrogen coupling system is connected to the weak current grid, a grid type virtual synchronous generator (VSG) moment of inertia self-adaptive control strategy based on dynamic feedback of hydrogen storage system pressure is proposed. Firstly, a physical simulation model of the grid type wind hydrogen coupling system is established, the closed-loop transfer function of active power is derived, and the influence of rotational inertia and damping coefficient on the power frequency oscillation characteristics of the system is analyzed. Then, considering the dynamic changes in pressure of the hydrogen storage system, the moment of inertia calculation is optimized in real time to ensure stable operation of the wind hydrogen coupling system under grid frequency fluctuations and load active power fluctuations. Finally, the strategy is validated using MATLAB/SIMULINK platform. The results show that, using the grid type self-adaptive method can accelerate the frequency recovery of the system, significantly improve the dynamic response ability of the system, and achieve stable operation of the wind hydrogen coupling system.

With the high proportion of new energy connected to power grid, multi-machine parallel coordinated control of energy storage inverter has become a key problem. Virtual synchronous generator (VSG) algorithm can provide damping, inertial support and stable voltage frequency for grid-forming energy storage system. However, the parallel synchronization, stability, state of charge (SOC) of each stack and impedance of each line should be considered in the coordinated control of parallel operation of multiple energy storage inverters. To solve this problem, a parallel mathematical model of energy storage inverter is established, the methods of reactive power allocation considering virtual impedance and active power allocation considering SOC are analyzed, and an improved VSG control strategy combining self-adaptive virtual impedance and SOC equalization is proposed. Finally, a model is built on the MATLAB/Simulink simulation platform, and the coordination control of each energy storage inverter is analyzed under the discharge condition with the all vanadium redox flow battery pack as the energy storage system. The validity of the improved VSG control strategy is verified, and the problem of over-discharge caused by voltage drop, reactive power and SOC difference caused by impedance difference is solved effectively, the utilization efficiency of the battery and the energy storage inverter is improved, and the life loss of the battery is reduced.

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.

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.

Under the “dual-carbon” background, in order to realize low-carbon emission and maximize wind power consumption of the microgrid system, an optimal scheduling strategy with a two-layer model of integrated energy system (IES) containing carbon capture power plant (CCPP) and power-to-gas (P2G) coupling and vehicle into the grid (V2G) is proposed. Firstly, at the low-carbon technology level, to address the problem that the CCPP and P2G equipment operate out of sync in time, a liquid storage tank is added as a CO₂ buffer station in the middle of the CCPP and the P2G equipment, and a mathematical model containing the CCPP, the P2G equipment and the gas turbine is established. Moreover, a laddered carbon transaction is established to impose low-carbon emission constraints on the IES. Secondly, in order to fully utilize the dual characteristics of EV load and energy storage, strategies are formulated to guide EV charging and discharging during wind abandonment hours and peak hours of the IES to carry out energy time shifting. Finally, at the level of economic efficiency, the integrated operating cost minimization is taken as the objective function, and MATLAB is used to invoke the GUROBI solver to solve the problem. By setting up different scenarios for comparison, the results show that the scheduling strategy can improve the level of microgrid wind power consumption while realizing the low-carbon economic operation of the system.

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.

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.

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.