A Sensitivity Approach to Model Local Voltage Controllers in Distribution Networks

Local controllers are essential in distribution networks; they are employed in classical devices such as load tap-changing (LTC) transformers and switchable shunt capacitors, and more recently in distributed generation (DG). The effective use of distribution management system (DMS) applications requires an accurate model of the interaction between the local controllers through the distribution system. This paper presents a new sensitivity matrix approach for modeling such interactions, and demonstrates its application in the implicit ZBus Gauss method for power flow computation. The sensitivity method models both PV buses (for the connection of DG) and tap position adjustments through current source injections, and consequently avoids re-factorization of the network bus admittance matrix. Numerical results on distribution networks with up to 3145 buses show that the sensitivity-based power flow method for simulating the operation of local controllers is superior to a sequential control action adjustment approach previously proposed in the literature, and that its computing time is commensurate with the performance requirements in real-time DMS applications.