Active Power Reserve Range of DFIGs at the Fixed Power Factor Based on Sensitivity of Power System

With fast increase of the renewable energy, the wind turbine generators, such as the doubly-fed induction generator (DFIG), are expected to participate in active power balance and frequency stability of power system. Hence it is required to decide the active power reserve range of the DFIGs at a fixed power factor. In this paper, a method to decide the active power reserve range of the DFIG at a fixed power factor is given based on the overspeed mode. The power flow model with the DFIGs is derived. The constraints to the rotor speed and the capacity of the rotor-side converter are included to find the steady-state lower active power limit of the DFIG at a fixed power factor. Under this operation mode, the eigenvalue analysis is performed to the power system to find the critical modes. Since the slip s and reactive power of DFIG
$Q_\text{DFIG}$
affect the initial value and the state matrix, the Jacobian matrix is extended to derive the analytical expression of the sensitivities of the eigenvalues with respect to
$s$
and
$Q_\text{DFIG}$
, based on which the critical mode strongly correlated to
$s$
and
$Q_\text{DFIG}$
are found. With the support of reactive power compensation, the
$s$
and lower active power limit are adjusted to eliminate the critical modes. and the active power reserve range of DFIGs is decided. The simulation results validate the accuracy and effectiveness of the proposed methods.