In recent years, the development of hydrogen energy has been widely discussed, particularly in combination with renewable energy sources, enabling the production of “green” hydrogen. With the significant increase in wind power generation, a promising solution for obtaining green hydrogen is the development of wind-to-hydrogen (W2H) systems. However, the high proportion of wind power and electrolyzers in a large-scale W2H system will bring about the problem of renewable energy consumption and frequency stability reduction. This paper analyzes the operational characteristics and economic feasibility of mainstream electrolyzers, leading to the proposal of a coordinated hydrogen production scheme involving both a proton exchange membrane (PEM) electrolyzer and an alkaline (ALK) electrolyzer. Subsequently, a coordinated control based on Model Predictive Control (MPC) is proposed for system frequency regulation in a large-scale W2H islanded microgrid. Finally, simulation results demonstrate that the system under PEM/ALK electrolyzers coordinated control not only flexibly accommodates fluctuating wind power but also maintains frequency stability in the face of large disturbances. Compared with the traditional system with all ALK electrolyzers, the frequency deviation of this system is reduced by 25%, the regulation time is shortened by 80%, and the demand for an energy storage system (ESS) is reduced. The result validates the effectiveness of MPC and the benefits of the PEM/ALK electrolyzers coordinated hydrogen production scheme.

As the power system develops towards a high proportion of renewable energy sources and power electronic devices, the power system suffers from poor frequency stability due to the lack of synthetic inertia. The grid-forming energy storage can not only improve the frequency dynamic response of the generator and enhance inertia support capability but can also realize the peak regulation and valley filling of the power system. But its relatively high configuration cost restricts its development and construction. Therefore, how to rationally configure the grid-forming energy storage and grid-following energy storage within the power system by means of corresponding technical approaches has become the focal point of academic research. This study proposes a method for evaluating the inertia distribution characteristics of the power system based on the network equations of the power system. Furthermore, the demand for grid-forming energy storage at each node of the power system under different operation scenarios can be quantified according to this method. Finally, an optimization configuration method for an energy storage system that can improve the inertia distribution characteristics of the power system is proposed, and its effectiveness is verified through the 39-bus system.

With the ongoing integration of renewable energy and energy storage into the power grid, the voltage safety issue has become a significant challenge for the distribution power system. Therefore, this study proposes a coordinated operation for energy storage systems with reactive power compensators. Taking into account the benefits of energy storage equipped with reactive power compensators and the market clearing process, a bi-level optimization model is formulated. In the proposed model, the upper-level model formulates the bidding strategy for energy storage and aims at maximizing the energy storage revenue; the lower-level model carries out a market-clearing process that takes into account various constraints for ensuring the safe operation of the grid. Afterward, by applying several math tricks such as the KKT optimality condition, the strong duality theorem, and the big M method, the bi-level equilibrium programming problem is transformed into an equivalent and tractable single-level mixed-integer linear programming problem. The results show that the coordinated operation of energy storage and reactive power compensators increases the benefit of energy storage by 3.47%. The benefit increment and security improvement brought by the collaborative operation of energy storage and reactive power compensators are verified.

To address the difficulty in accurately characterizing the fault current response of renewable energy grid-connected devices during high-/low-voltage ride-through, this paper proposes a fault current response modeling and parameter identification method based on adaptive nonlinear compensation. First, with the fault voltage and pre-fault operating point as input variables, a basic quadratic equivalent model is established to describe the main variation characteristics of active and reactive currents during high-/low-voltage ride-through. Second, nonlinear compensation terms are introduced into the basic model to correct the response deviation caused by the simplification of fast electromagnetic control links in the electromechanical transient equivalent process, thereby improving the representation capability of the model for complex fault current characteristics. Furthermore, considering that the structural parameters of the nonlinear compensation terms are difficult to directly identify using the traditional least squares method, a differential evolution–ridge regression (DE–Ridge) hierarchical identification method is proposed. In this method, the differential evolution algorithm is used in the outer layer to adaptively optimize the nonlinear structural parameters, while ridge regression is used in the inner layer to solve the corresponding linear coefficients. Case study results show that, compared with the traditional quadratic equivalent model and the fixed nonlinear compensation model, the proposed method further reduces the fault current identification error on the validation set and improves the identification accuracy and generalization capability of fault current responses during high-/low-voltage ride-through.