Reactive Power Absorption Capability of Dual-Excited Condenser With Symmetric Excitation Scheme

The integration of renewable energy and ultra-high-voltage direct current (UHVDC) systems into the power grid introduces challenges such as commutation failure and transient overvoltage issues. This paper explores the reactive power absorption capability of dual-excited synchronous condensers with a symmetric excitation scheme, which can address these challenges more effectively than conventional synchronous condensers. The dual-excited synchronous condensers, equipped with two sets of excitation windings, can operate with negative excitation, thus enhancing reactive power absorption. The study delves into the basic principles of operation; the excitation winding structure; and the reactive power capability of dual-excited synchronous condensers. Compared to an asymmetric dual excitation scheme, the rotor with a symmetric dual excitation scheme offers a broader range of excitation emf adjustment and is easier to design and manufacture. The stability of the dual-excited condenser is improved through the coordinated regulation of d-axis and q-axis excitation. A detailed electromagnetic transient simulation model developed in PSCAD demonstrates that dual-excitation synchronous condensers can stably absorb over 2 p.u. of reactive power, a performance level that surpasses the limitations of conventional synchronous condensers.