Extreme Bifurcation Interval With Deep PV Penetration Considering Correlated Net Bus Load Forecast Errors

The proliferation of photovoltaics (PV) in distribution systems brings about voltage stability problems. This paper proposes an algorithm to calculate extreme bifurcation intervals considering deep PV penetration levels. The paper applies the sandglass-hyper-ellipsoid-cone model to analyze the correlations among net bus loads representing bidirectional power flows for different PV penetration levels. Using the net bus load model, three extreme bifurcation points on voltage stability limit hypersurface are formulated where two of these points represent the voltage stability bifurcation interval in the forecasted net bus loading direction. An iterative method is applied to obtain bifurcation solutions. The validity of the proposed method is verified by using the IEEE 3-bus system, the IEEE 33-bus system and the IEEE 123-node test feeder. The numerical results demonstrate that the proposed sandglass-hyper-ellipsoid-cone net bus load model and solutions are effective in managing correlated net bus load forecast errors in distribution systems with PV integration.