Estimation of Voltage Unbalance Attenuation Caused by Three-Phase Induction Motors: An Extension to Distribution System State Estimation
With the increased interest in controlling and man-aging voltage unbalance (VU), network operators are now increas-ingly being motivated to obtain the state of their networks withgreater details. Distribution system state estimation (DSSE) is aprominent tool that enables network operators to estimate the level,location, and related impacts of VU. DSSE techniques developed todate which use the polynomial or exponential load models are de-ficient in recognizing VU attenuation associated with three-phaseinduction motors (IMs) that are directly connected to the ac net-work. Adoption of adequate three-phase models of IMs, which areused in full unbalanced load flow, into the existing DSSE tech-niques is not feasible due to several factors including requirementof extensive data, additional computational efforts, and major con-straints related to incorporating the necessary modifications. Asa solution, this paper proposes a novel formulation for postpro-cessing the results of current DSSE techniques to reflect the afore-mentioned behavior of IMs. Simulations are carried out using theIEEE 13 bus distribution network for a range of scenarios to ver-ify the developed methodology. The work presented in relation toVU attenuation in interconnected networks also complements theexisting treatise in IEC documentation that only deals with radialnetworks.