A Study On Power System Static Voltage Security Region

In recent years, the electric power supply has become tighter in our country andgrids at all levels are generally at the state of near steady limit and heavy load. Inorder to ensure the normal operation of power system, a comprehensive understandingand evaluation for the security and stability of power system is necessary. In securitymonitoring, assessment and control of power system, the calculation method ofsecurity region in decision making space has very important significance. As the nodevoltage constraint is one of the basic security constraints in actual grid operation, thispaper defines the power system static voltage security region in decision makingspace. The calculation method and availability of the approximate boundary of powersystem static voltage security region is studied.First, as the voltage amplitudes at all generator nodes are often seen as controlvariables, the variables in the decision making space include the active powerinjections at the nodes of all generators and loads, the reactive power injections at allload nodes and the voltage amplitudes at all generator nodes, and thus themathematical expression of the power system static voltage security region in such adecision making space is given.Based on AC power flow model, the hyperplane expression of the boundary ofstatic voltage security region of power system in decision making space is derived.Lots of illustrative examples show that, for a given upper limit (or lower limit) ofvoltage at a node, the engineering practical part of the corresponding boundary ofstatic voltage security region, can be described by a hyperplane in decision makingspace approximately. The computation burden of the approach proposed in this paperis much less than that of the approximation method based on lots of voltage securitycritical points obtained by AC power flow simulation, and the precision is acceptablefrom engineering point of view.Finally, as more and more wind farms are connected into power system, thispaper gives a calculation method of the approximate boundary of power system staticvoltage security region in decision making space including the active power injectionof wind power. The approximate boundary of static voltage security region iscompared with that in power system without wind power, and thus this paper analyzesthe affects of wind power on power system static voltage security region.