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

The modular multilevel matrix converter (M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>C) 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 M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>C to transmit the grid frequency change, and proposes a control strategy in which the M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>C is coordinated with the OWF to provide inertial response to the onshore AC system. The relationship between the SM-CV of the M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>C and the grid frequency is established, which gives the M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>C the capability of inertial response. The SM-CV variation of the M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>C 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.