This Masters Thesis investigates the influence of the voltage phasor measurement unit placement in the power distribution system on the precision of distribution of state estimation results. Using simulations in software tools Matlab and C ++ the influence of such placement of the phasor measurement units on the precision of a three-phase distribution state estimator is demonstrated.
Sufficient number of pseudo measurements from smart meters were provided in the form of real and reactive power injections, in order to ensure the electric grid observabilty. In the Matlab software tool we mathematically modeled realistic measurements with added white Gaussian noise, contained by all measuring devices and which in fact causes the variance of state estimation results. It has been shown that the accuracy classes of measurements, which are predefined in all types of measurements in the simulation, influence the variance of the state estimator.
By using numerical calculations and graphical visualization it has been shown that the results highlight the relationship between the variance of the state estimator, angle Φ, voltage magnitude |U| and the placement of a number of PMU measurement devices in to the 13-bus radial feeder. It has been shown that by adding the PMU measuring devices, the variance of the static three-phase distribution state estimator is being significantlly decreased only for the angle Φ. Whereas, for the voltage magnitude |U|, the difference between 1 and 13 added PMU measurement devices is insignificant. Further on, by using a computer simulation it has been demonstrated that the relation between the added number of PMU measurement devices and the variance of the static three-phase distribution state estimator is represented by an exponential function.
The thesis concludes that for an acceptable variance of the static three-phase distribution state estimator 100% coverage of radial distribution network is needed, due to explicit non-linear relation between the estimated angles Φ of the voltage phasors and further power flow calculations in real-time. Consequently, it is difficult to address the optimization of the PMU measurement devices placement due to heuristic nature of the method, as all combinations of the measurements placement is too complex to be simluated.