# Research on Robust Day-Ahead Dispatch Considering Primary Frequency Response of Wind Turbine
## 1 Introduction  
With the rapid development of the power system and the increasing demand of countries across the globe to protect the environment, renewable energy represented by wind power and the photovoltaic turbine has received more and more attention. As a major power consumer, the Chinese government attaches great importance to the development and utilization of renewable energy. Recent years have seen remarkable progress in the wind power and photovoltaic industries and the installed capacity in China. In 2017, the installed capacity for wind power in China reached 163,670 MW, up by 10.5%, while the installed photovoltaic capacity was 130,250 MW, up by 68.7% compared with the year before [1]. It is worth noting that the large-scale integration of renewable energy to the power system poses a challenge to its frequency stability. As an example, take the wind power that cannot be dispatched; its influence on the control of the system frequency is demonstrated in the following areas [2,3]:1. The converter decouples the turbine's rotor from the system frequency, which indicates that the mechanical power of the wind turbines and the electromagnetic power of the system are decoupled; in this way, the fan will not be able to provide an inertial response. Moreover, as the wind turbines usually run in a maximum power point tracking (MPPT) mode, the primary frequency reserve could not be retained;
2. With a large-scale wind integrated power system taking the place of some conventional synchronous generator units with the frequency regulation capability, the inertia of the wind turbine will be 0 with no reserve in the case of frequency fluctuations due to power loss and other reasons, which will harm the inertial response ability and primary frequency reserve capacity. Scholars have conducted extensive and in-depth research into this issue. In [3], the influence of the large-scale replacement of conventional synchronous generators by wind turbines is analyzed, and based on this the author proposes the primary reserve strategy for conventional synchronous generators to avoid load shedding while ensuring the system frequency stability. The work in [4] has analyzed the impact of implementing high-penetration renewable energy sources on frequency and active power. The idea of combining the energy storage with a wind farm and making full use of the features of quick response and control flexibility of the energy storage for the frequency regulation of the system through charge and discharge in the peak-to-valley period is proposed in [5; 6]. However, limited by the storage technology and costs, the electric energy cannot be stored in large quantity. Some scholars and engineering experts therefore put forward the virtual synchronous generator (VSG) technology, which makes it possible for the grid connection of the new energy units using the power controller containing power electronic converters to share the features of the grid-connected synchronous generator, such as inertia, damp, frequency regulation and voltage regulation [7; 8; 9]. During this process, the rotor motion equations for the VSG and primary frequency regulation are also introduced. [PERSON], et al. [10] compares VSG with droop control and draws the conclusion that VSG can provide greater inertia and system frequency stability. Therefore, the VSG in wind turbines plays a role in the frequency regulation during the operation of the system. The primary frequency regulation of conventional synchronous generators in the system dispatch strategy, which often appears as the primary reserve, is the second-level reserve triggered automatically by the fluctuation of the frequency. The work in [11] establishes a system frequency response model in the economic dispatch which contains a large number of nonlinear and non-convex constraints, while in [12], the primary reserve constraint is taken into account in the conventional unit commitment problem, which is later solved through the mixed integer linear programming method.