A modified Newton–Raphson load flow scheme for directly including generator reactive power limits using complementarity framework

• A modified NR load flow which automatically includes generator Q limits is proposed.
• Modelling Q–V relation at a PV bus using Mixed Complementarity Problem framework.
• Simultaneously solving conventional load flow equations along with the merit function.
• Extensive testing and comparison of the proposed method with conventional methods.

A modified Newton–Raphson (NR) load flow scheme which automatically incorporates generator reactive power limits is proposed. Traditionally, handling generator reactive power limits is considered as an adjusted load flow solution and this adjustment is carried out through bus type switching method. Incorporating bus type switching in a NR algorithm is not straight forward, as it involves several subjective decisions and hence, there is no commonly used implementation. The modified NR scheme proposed here combines this adjustment feature in the load flow problem formulation directly. This is achieved by augmenting the set of complementary reactive power relations at voltage controlled buses with the conventional set of active power balance equations at all buses and reactive power balance equations at load buses in a Mixed Complementarity Problem (MCP) framework. Effectiveness of the scheme has been demonstrated through extensive simulations considering a number of test systems.