Statcom Case Study

CHAPTER 4
OPTIMAL PLACEMENT & SIZING OF STATCOM USING FUZZY HYBRID PSO-GS
ALGORITHM
4.1 Introduction
As discussed in chapter 1, placement of StatCom in power system has numerous positive impacts, but these impacts can be further enhanced if the StatCom is installed at a proper place and in a proper size. The optimal placement and sizing of StatCom is handled as an optimization problem. The problem of finding optimal placement and capacity (size) of StatCom, for improving voltage profile of load buses and also improving the voltage stability margin, is a multi-objective optimization problem. Fuzzy formulation is used to convert multi-objective optimization problem into a single objective optimization problem, is also discussed in Chapter

The value of Eigen value is 0.2005 for line outage 36, which is lowest. Therefore it is most severe from the viewpoint of voltage stability margin.
Out of various load buses, weakest buses were selected as potential buses for placement of a StatCom. Participation Factors of load buses for critical mode I, II and III, as obtained from modal analysis, were considered for selection and ranking of weakest buses following a contingency. For line outage 36(the most severe line outage under normal loading Case A), the 9 weakest buses thus selected are bus nos. 18, 19, 20, 23, 25, 26, 27, 29 and 30, which were considered as possible locations for placement of a StatCom. Table 4.3 depicts the weakest buses along with their Participation Factors for line outage 36.
This has been observed from load flow analysis for outage of line nos. 33, 37, 38 and 14, the voltage at various buses is within security limit. Also, the minimum Eigen values corresponding to outage of line nos. 33, 37, 38 and 14 are more as compared to that of outage of line (LO) 36. Thus, it seems that there is no need of StatCom placement during outage of line nos. 33 37, 38 and 14. Hence, these line outage cases were not considered for finding the optimal location and size of

In this line outage contingency, the minimum Eigen value is least and total voltage deviation is largest as compared to that in other line outages. During the line outage (LO) 36, voltage security limits at bus nos. 25, 26, 27, 29 and 30 were violated.
Using the proposed approach i.e. Fuzzy Hybrid PSO-GS Algorithm, the optimal location for StatCom is found to be bus no. 30 with its size as 13.2179 MVAR. After placement of StatCom of rating 13.2179 MVAR at bus no. 30, the system is found to be in secured state and voltage stability has been improved. The results of optimal placement and sizing problem using PSO, GSA and PSO-GSA are summarized in Table 4.4. All these three algorithms provided the same location of StatCom, which is bus no. 30.
Convergence characteristics of PSO, GSA and Hybrid PSO-GSA for LO 36 have been shown in Figure 4.1, which clearly shows the fast convergence of Hybrid PSO-GS algorithm. Voltage profile of the IEEE 30-bus system in base case condition and during the 5 most critical single line outage contingencies have been shown graphically in Figure 4.2. The voltage profile as obtained after placement of StatCom at bus no. 30 has been compared with the case when no StatCom was connected following LO36 in Figure