The Conditional Diagrams Between the Electric Generator and the Electric Grid to Which it is Connected

摘要

This article presents five types of important diagrams with the parameters of electric generators and the parameters of the electric grid to which they are connected. The PQ diagram (active power -reactive power) of electric generators is an important tool for the use of electric generators connected to an electric grid. The PQ diagram defines the operating region of a generator in the P - active power and Q- reactive power space, while connected to an electric grid. The space is conditioned on one side by the parameters of the generator and on the other side by the parameters of the transport grid. Also, secondary zones for the voltage regulation system service are outlined in this space. There is a theoretical PQ diagram, and on-line PQ diagram and a real PQ diagram. The Q generator - Ugrid diagram (generator reactive power - grid voltage) represents the power variation curves of the reactive power generated or absorbed by the generator as a function of the grid voltage in the connection point, for various constant parameters of the generator (rotor current, stator current, output voltage, internal angle). The entire family of curves defines the operating region of the generator as the reactive power as a function of the grid voltage. The Ugrid - cosρ generator diagram (grid voltage - generator power factor) shows the operating region of the generator at nominal power or different power when the grid voltage and generator and network power factor are varied. This region is bounded by the minimum and maximum grid voltage, the inductive and capacitive power factor bounds, the maximum and minimum output votlage of the generator and the bounds of the stator and nominal excitation currents. The Ugenerator - fgrid diagram (generator voltage - grid frequency) shows the operating condition of the generator in the rated frequency domain of the grid to which it is connected. The domain is bounded by the rated normalized generator voltage and grid frequency at the connection point. The Pgenerator -fgrid diagram (generator power - grid frequency) is an availability curve for a generator to reduce its output power when operating with an already low grid frequency. This diagram represents the operating condition of the generators in the extended domain of the frequency of the network. The article presents the theoretical fundamentals for each diagram, as well as an example for a 210MW turbogenerator connected to a 220kV grid through a 250MW transformer.