DC‐side stability analysis of grid‐tied converter with different control modes based on electrical torque analysis

Abstract

AbstractThe DC‐side stability of the grid‐tied converter under different control modes is fully investigated using electrical torque analysis. The small‐signal model of a single converter connected to an ideal DC bus under various control modes is formulated. Accordingly, the damping and synchronising coefficient contributed by the DC network and controllers of grid‐tied converter are separately accessed using the electrical torque analysis method and the stabilising conditions of the grid‐tied converter operating under different control modes are further derived. The system stability mainly corresponds with DC network dynamics under constant active power control mode. On the contrary, the grid‐tied converter under constant DC‐link voltage control mode has no stability problem. Generally, elevating the DC‐link capacitance or decreasing the droop gain can greatly improve the stability margin reserve of the VSC‐HVDC links. In addition, the control gains of the classical PQ controller are proven to have limited impacts on DC‐side system stability. Finally, the results of numerical simulation prove the validity of the proposed stability analysis method and the stable boundary for the grid‐tied converter with different control modes.