The Calculation Method Of Power System Static Angle Stability Reserve Factor Based On Resistance Margin

In recent years,the power Angle stability researches are mainly focused on the transient Angle stability.But in the practical power system operation dispatch,static Angle stability analysis and static Angle stability margin calculation should be more basic,at present,we still face some difficult problems cannot be solved.for example,since the power-angle characteristics of multi-motor system is a multi-variable function,so in theory,we cannot calculate its limit power,however,the key to solve multi-machine system static Angle stability reserve factor is to solve limit power.Look from PV node,apply relative comprehensive dynamic equivalence method to make equivalent simplify of power system,define resistance margin to evaluate PV nodes’ static power angle stability.The resistance margin index is arctangent function of active power increment and reactive power increment ratio which is injected into the PV node,its meaning is consistent with the overall power coefficient of simple system.Resistance margin is normalized sensitivity index,which can evaluate the current system power-angle stability very well.In the power system operation scheduling and planning design,according to the resistance margins we can sort strong and weak for PV nodes’ static angle stability.If system appears active power gaps,priority to raise active power of big resistance margin power PV nodes,and reduce the small resistance margin power PV nodes to send active power,which can improve running stability of system.resistance margin index only need local measurement information,so it has a high degree of online application value.Because power system is non-analytic complex system,if we use traditional Thevenin equivalence principle to make equivalence and simplification to system,then the system’s Thevenin equivalence parameter is not unique and without general complex meaning,so the Thevenin equivalent impedance is not used for the characteristic analysis of circuit.The text research shows that if the system’s thevenin equivalent impedance Angle is known when we see from PV node,the system’s thevenin equivalent parameters can be measured uniquely with local information.Based on thevenin equivalent parameters,make simplification of complicated power system into a simple 2 machine system,and analyze static Angle stability limit power of the nodes which have voltage support capacity in the power system,ulteriorly,to calculate static energy stability reserve factor of complex power system.Put forward the static power-angle stability reserve factor calculation method based on resistance margin.Combined with resistance margin index and thevenin equivalent circuit phasor diagram,deduced limit power calculation formula of PV node in consideration of system inner resistance.According to the characteristics of simple system transmission line resistance and internal parallel load,analyzed the range of system thevenin equivalent impedance angle’s residual angel theoretically,and an online identification method for this angle is proposed.In the system stable operation point,the nodes’ extreme power can be accurately estimated by the local measurement information,thus,the complex power system static Angle stability reserve factor calculation difficulty is overcome.The method of this text offered has clear physical meaning,and it is not dependent on the system detailed model,which provided a quantitative calculation method for power system transient stability’s and dynamic stability’s online assessment as well as control,this is also the most promising for application and valuable for research of resistance margin index development direction.