PQ Decomposition Method for Power Flow Calculation

The PQ decomposition method for power flow calculation is a simplified Newton-Raphson approach widely used in power systems. This method leverages two key characteristics of electrical networks: active power primarily relates to bus voltage angles, while reactive power mainly depends on voltage magnitudes. This decoupling property allows the decomposition of the full Jacobian matrix into two independent subproblems, significantly improving computational efficiency.

In MATLAB implementation, the algorithm typically involves these key steps: First, the bus admittance matrix is constructed based on system topology. Then initial voltage profiles are established for all buses using system parameters. The program subsequently formulates separate correction equations for active and reactive power, solving for voltage angle and magnitude corrections through alternating iterations. After each iteration, power mismatches are checked against convergence criteria until errors fall below a predefined threshold. Critical functions include admittance matrix formation, mismatch calculation, and iterative solver implementation.

Correct execution results demonstrate successful implementation of the core algorithm concept: using P-Q decomposition to reduce computational complexity while maintaining sufficient accuracy. This method is particularly suitable for online analysis of large-scale power systems due to its faster convergence and lower memory requirements compared to the full Newton-Raphson method. Practical applications require careful handling of special boundary conditions for PV buses and slack buses, which is crucial for ensuring physical validity of calculation results. Code implementation should include proper bus type classification and constraint enforcement mechanisms.