Power Flow Calculation for Grid-Connected DFIG Wind Turbines Using PQ Decoupling Method

The PQ decoupling method is an efficient power flow calculation technique particularly suitable for analyzing grid-connected systems containing doubly-fed induction generators (DFIGs). This approach significantly reduces computational complexity while ensuring result accuracy by decoupling active power (P) and reactive power (Q) in the power flow calculation process. In code implementation, this typically involves separate iterative solvers for P-θ and Q-V relationships.

In grid-connected DFIG systems, the generator achieves flexible active and reactive power control through rotor-side converters and grid-side converters. Under steady-state conditions, DFIGs can be modeled as PQ nodes in power flow calculations. The core principle of the PQ decoupling method establishes that node voltage magnitude primarily correlates with reactive power, while voltage phase angle mainly relates to active power. This enables the decomposition of nonlinear equations into two relatively independent subproblems solved through separate iterations. Algorithm implementation typically involves Jacobian matrix modifications where off-diagonal elements are neglected to simplify computations.

This method proves particularly practical for wind power integration analysis, as DFIG dynamic characteristics can be simplified into power injection models during steady-state power flow calculations. Combined with the efficiency of PQ decoupling, it enables rapid assessment of key grid indicators including voltage stability and power distribution, providing crucial foundations for system planning and operation. The computational approach often incorporates Newton-Raphson iterations with decoupled power flow equations for faster convergence.