Stabilizing control of long distance longitudinal power system by superconducting magnetic energy storage

Studies on steady-state stability of looped power systems and stabilization by SMES

“…Figure 2 shows the results for the 5-machine longitudinal power system. In the longitudinal power system, the oscillations are similar to those of a string both of whose ends are free (the generator model is a field winding model, and is shown in Appendix A along with the system parameters; hereafter it will be called the A Model) [3]. The mode number is attached in order of lower frequencies, and the number of nodes (the points which do not oscillate) agrees with the number of each node.…”

“…As a control scheme of SMES, the control angle of SMES is controlled by the scheme in which the SMES power is controlled by the angular velocity deviation of the generator (the electric power is absorbed at SMES when 'Z is positive), namely, by where 'D is the control angle deviation of the thyristor bridge and K s , T s are the gain and time constant of the control system. With this equation, the scheme of controlling the SMES power will be adopted [3,4].…”

“…proved by installing the SMES at the generator whose eigenvector elements are large [3]. When the SMES capacity becomes larger, the eigenvector will change due to the influence of the control of SMES power.…”

“…In particular, when the relative phase angle of the elements of the eigenvector corresponding to the generator where the SMES is installed with respect to the other elements changes, the conclusion of the case in which the capacity is small will not hold as it does sometimes; however, in order to improve the first mode (the mode in which both ends of the power system swing in opposite directions), which influences most largely the stability of the longitudinal power system, it is effective to install the SMES at the ends of the power system. Table 2 shows the results for a 5-machine longitudinal power system (B Model) [3]. The parameters of the control system assumed are K s = 0.5 and T s = 0.01 s; it is assumed that the SMES capacity is 12% of the generator output power (5000 MW).…”

“…It was found that the first mode of the longitudinal power system can be efficiently suppressed by installing SMES at the ends of the power system [3].…”