Coordinated Inertial Response Control Strategy for Modular Multilevel Matrix Converter and Low Frequency Offshore Wind Farm

The modular multilevel matrix converter (M3C) is a core component of low frequency transmission technology that decouples the offshore wind power system from the onshore alternate current (AC) system. This makes the offshore wind farm (OWF) unable to directly respond to the frequency change of the onshore system. Therefore, this paper utilizes the submodule capacitor voltage (SM-CV) of the M3C to transmit the grid frequency change, and proposes a control strategy in which the M3C is coordinated with the OWF to provide inertial response to the onshore AC system. The relationship between the SM-CV of the M3C and the grid frequency is established, which gives the M3C the capability of inertial response. The SM-CV variation of the M3C is utilized to obtain the desired variation information of the low frequency, and then the signal channel is utilized to transfer the frequency variation information of the low-frequency to the OWF. The model predictive control (MPC) is adopted for the OWF in order to achieve optimal control according to the operating conditions of the wind turbines (WTs). The proposed scheme does not require additional communication lines, which enhances the reliability and economy of the whole system operation. Finally, the effectiveness of the proposed scheme is verified by simulation in MATLAB/Simulink.