Modelling and Control of Synthetic Inertia Controller for Modular Multilevel Converter Fed HVDC Systems

Increasing inertia of the grid connected system using HVDC converter integrated wind farm system is a popular solution now-a-days. This paper deals with such a system with appropriate modelling and control of synthetic inertia of the grid connected system. VSC-HVDC based Modular Multilevel Converter (MMC) and its internal controllers (DC Voltage and current controller) are employed for the application along with inertia emulation control and generator emulation control. Coordinated control technique is implemented in which wind turbines participate in the frequency support of the main grid along with stored energy in the MMC DC link without the use of communication cables. This paper emphasizes the effect of the design of various control loops in the synthetic inertia modelling and a detailed frequency domain modelling is carried out for different control loops to analyse the performance of the system. The concept is validated through PLECS based back-to-back MMC interfacing main grid and wind system through 400km HVDC line.