## 2 Analysis of the Operating Mechanism of a Hybrid Plant Station Primary Frequency Regulation  
Figure 1 shows the structure of the proposed hybrid power station. Module I is the wind turbine unit, composed of the wind-storage integrated doubly-fed wind turbine unit shown in module II. The energy storage device is connected to the DC bus of the wind turbine through the DC-DC converter. The wind turbine blade captures the wind energy. It converts it into its rotational kinetic energy, which is then converted into electric energy by the double-fed induction generator and collected in the AC bus. Part of the electric energy is sent to the distribution network shown in module III for grid-connected power generation, and the other part flows to module IV for hydrogen production by wind curtailment. The wind curtailment to produce hydrogen modules includes the electric hydrogen production system and the hydrogen downstream industry. The downstream industry of hydrogen consumption shown in module V includes hydrogen compression, which is used in the hydrogen industry through transmission pipelines and the raw material supply of hydrogen energy vehicles. On the other hand, hydrogen can be used as a raw material to synthesize natural gas with carbon dioxide and then sold directly to the natural gas network to obtain economic benefits. A hybrid plant station's wind turbines run in accordance with the maximum wind power curve, and because the rotor speed is totally disconnected from the system frequency, it is unable to react to changes in the frequency of the system. Through the rotor speed-regulating mechanism, there exists a coupling relationship between the system frequency and the synchronous generator, which can enhance the power output in response to frequency variation. Therefore, the primary frequency regulation characteristics of a hybrid plant station combining energy storage, hydrogen production, and wind power generation are analyzed based on the primary frequency regulation method of the traditional synchronous set. The inertia response of the synchronous generator inhibits the frequency change rate. The drop characteristic reduces the frequency change value, and the frequency regulation mechanism is shown in Appendix A. Through frequency regulation, the synchronous generator restores the frequency to a reasonable range [6] (domestic technical indicators require a frequency fluctuation range of 47 Hz to 52 Hz). This analysis focuses on the power compensation technique of a hybrid plant station under the situation of frequency drop since a sudden increase in load typically produces a system frequency abrupt shift. Three processes are involved in the wind turbine simulated synchronous generators' response to changes in system frequency, as depicted in Figure 2. (1) The synchronous generators' inertia response; (2) The synchronous generators' inertia response and droop characteristics; (3) The synchronous generators' droop characteristics are simulated. 1. The inertia response energy source of the synchronous generator is the rotor kinetic energy. Assuming that the system frequency drops from 50 Hz to \(f_{1}\), the per-unit value of speed change is \(f_{1}\)/50\(\sim\)1 pu, and the kinetic energy of the rotor released by the synchronous generator is as shown in Equation (1) [25]: \[\Delta E_{\text{k\_max}}=\frac{1}{2}\Big{/}\Big{(}1^{2}-(f_{1}/50)^{2}\Big{)} \omega_{\text{S}}^{2}\] (1)  
In the equation, \(J\) is the moment of inertia of the generator; and \(\omega_{\text{s}}\) is the rated speed of the generator. Figure 1: Schematic diagram of the system architecture of the hybrid plant station. Figure 2: Types of power regulation when grid frequency changes.