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The neighboring wind farms have great frequency support potential. The wind turbine generators (WTGs) in these wind farms are influenced by wake effects and have different frequency support capabilities. In order to fully utilize the WTGs' support capabilities under different operating states, this paper proposes a two-level distributed consensus (TLDC) control to cooperate all the WTGs. Level I is leader-follower control, which is equipped within the wind farms. Level II is leaderless control which is used among the wind farms. This method is able to assign different values of power commands to different WTGs in the system to achieve better frequency support effect and stability. Based on MATLAB/Simulink and Opal-RT real-time simulation platforms, the two-area power system and Guangshui system (100% renewable energy power system) are analyzed, respectively. Simulation results show that the proposed TLDC method has a better effect compared with other frequency support methods. It can also flexibly respond to communication interruptions and delays.

The frequency support capability of each wind turbine (WT) within a wind farm varies based on factors such as location, wind direction, operating conditions, and wake effect. To fully utilize the frequency support capability of a wind farm, output power should be allocated to each WT based on its individual states. This article proposes a distributed adaptive leaderless consensus control (DALC) scheme for wind farms to achieve fast frequency support. The leaderless consensus algorithm is utilized among WTs to exchange operating information with neighbors and ensure reasonable power allocation. Additionally, frequency regulation coefficients adaptively change to ensure safe WT operation. After the frequency support stage, a preset recovery control is proposed to alleviate the second frequency drop (SFD) during the restoration stage. Case studies are conducted based on a two-area power system using MATLAB/Simulink and opal-RT real-time simulation platforms. Simulation results demonstrate the effectiveness and universality of the proposed DALC control scheme in both over-frequency and under-frequency events. Furthermore, the proposed control is found to be more reliable than leader-follower consensus-based control in the event of communication failure.

This paper proposes an adaptive dual droop control (ADDC) scheme, it can provide the disturbed onshore system with fast frequency support from both other undisturbed onshore systems, and voltage source converter-based multi-terminal direct current (VSC-MTDC) integrated offshore wind farms (OWFs). With conventional droop control at onshore converters, the DC voltage and power flow will change once frequency events occur, it will lead to frequency variations in other undisturbed systems. The proposed ADDC scheme firstly detects the disturbed and undisturbed systems, and then makes the undisturbed onshore system provide more frequency support power, while ensuring safe operation by settling the support power limitation and regulating the droop coefficients. Moreover, the offshore stations will estimate the onshore DC voltage as the control signal for fast frequency support. After that, the OWFs will recover their rotor speed with an asymptotic control scheme to reduce the second frequency drop. Case studies are carried out on 3-terminal and 5-terminal test systems, and the Opal-RT real-time simulation platform, respectively. Different control schemes are compared, and the parameter uncertainty and noise disturbance are considered to illustrate the performance and effectiveness of the proposed ADDC scheme.