Power Flow Modeling to Doubly-Fed Induction Generators (DFIGs) Under Power Regulation

Generalized State Estimation of Flexible AC Power Systems Considering Wind Generators and Primary Frequency Control

“…The DFIG's power flow model proposed in [11], based on the equivalent circuit shown in Figure 3 [11], has been adopted in this paper for estimating the seven state variables associated with these WTGs and two network's state variables. The former set of variables are θ m , V m , θ r , V r , θ g , V g , and s, where subscripts m, r, and g represent the magnetization branch, the rotor, and the grid side converter variables, respectively.…”

“…The detailed equations of these power flows are reported in Appendix A of [11]. In addition, if a PMU measures the current phasor at the DFIG's terminals, this measurement is represented by the real and imaginary components of the estimated measurements of currents by …”

“…These constraints correspond to the mismatch equations of active power in the stator winding (23), active and reactive powers at node m (24) and (25), active power at the back-to-back converter (26), reactive power setting at the grid-side converter (27), and the electromagnetic torque (28), respectively [11]. …”

“…In this context, a unified approach to compute the state variables of WTGs along with the nodal voltage magnitude and angles of the entire network was suggested in [8], and implemented in [9,10] for several types of WTGs, within the power flow problem perspective; accordingly a similar idea has been adopted in this paper for estimating the state variables related to the network and WTGs. Since the development of steady state models of WTGs is not new by any means, the detailed steady state mathematical models of WTGs included in the estimator are those previously reported in [9][10][11] for the FSWG, the semi-variable speed wind generator (SSWG) as well as two variable-speed wind generators (VSWGs) based on a doubly-fed induction generator (VSWG-DFIG) and on a permanent magnet synchronous generator (PMSG), respectively.…”

Minimum number of permanent-magnet synchronous generators for coordinated low-voltage ride-through of induction generators in hybrid wind farms

“…The focus is on coordinated LVRT to the IGs using the excessive reactive power of the PMSGs. The var capability of variable-speed WTGs is given by a grid-side converter (GSC) and is wider than IGs [12], especially under dispatch mode [13]. If the PMSGs are installed after the IGs to form a hybrid wind farm, the excessive reactive power of the former may be utilized to improve the voltage profile at PCC and help the LVRT of the IGs.…”