Compensation Of Voltage Sags Case Study

SIMULATION RESULTS AND DISCUSSION
4.5.1 Compensation of Voltage Sags All the proposed controllers performed to the IEEE standard. Table 4.5 shows voltage sag compensation of the proposed intelligent controllers. Compensated SS value shows the voltage sag compensation capability of the each proposed controller under different fault types and load conditions. In case 1, performance of DVR with proposed fuzzy logic controller has the sag score 0.5056pu observed at sensitive load before compensation. It indicates 50% voltage sag and after injection it is -0.006pu which indicates -0.6%. Here (-) negative sign indicates that the compensation is slightly above 1pu.It is evident from Table 4.5 that the compensated …show more content…
In this fault type Phase A voltage alone drops to 50% and the other phase remains unchanged. The DVR compensates the sensitive load voltage after injection with SS value being -0.004pu. Similarly all the proposed controller respond to the condition and inject the required voltage to maintain the load voltage to its predetermined value. From Table 4.6, for case 4, performance of DVR with the proposed ANFIS optimized fuzzy controller has the sag score of 0.2728pu at sensitive load before compensation due to insertion of non-linear load and after compensation the SS value is 0.025 pu. Simulation results have revealed that voltage sag compensation can be better in ANFIS optimized Fuzzy controller.

Table 4.5 Voltage sag compensation under various fault conditions
Voltage sag compensation during three phase to ground fault
Control method Voltage at sensitive load in pu
(uncompensated) Voltage at sensitive load in pu (compensated) Phase A Phase B Phase C …show more content…
(SS)
Conventional
PI 0.4944 0.4884 0.4890 0.5056 1.007 1.006 1.006 -0.006
Fuzzy Logic Control 0.4955 0.4897 0.4900 0.5082 1.002 1.004 1.004 -0.0033
ANN control 0.4948 0.4889 0.4894 0.509 1.002 1.003 1.003 -0.004
ANFIS optimized PI control 0.4951 0.4891 0.4895 0.5088 1.004 1.001 1.003 -0.002
ANFIS optimized fuzzy control 0.4956 0.4893 0.4897 0.4915 0.9802 0.9824 0.9804 0.019
Voltage sag compensation during double line to ground fault
Conventional
PI 0.4974 0.4906 0.9843 0.3425 1.006 1.003 1.003 -0.004
Fuzzy Logic Control 0.4983 0.4910 0.9889 0.3406 1.010 1.006 0.9979 -0.004
ANN control 0.4973 0.4904 0.9842 0.3427 1.001 1.002 1.003 -0.0023
ANFIS optimized PI control 0.4970 0.4906 0.9843 0.3427 1.003 1.000 1.003 -0.002
ANFIS optimized fuzzy control 0.4979 0.4909 0.9857 0.3419 0.9877 0.9823 0.9963 0.0112
Voltage sag compensation during single line to ground fault
Conventional
PI 0.4991 0.9854 0.9840 0.1772 1.006 1.002 1.004 -0.004
Fuzzy Logic Control 0.5002 0.9908 0.9879 0.1737 1.002 0.9980 0.9985 0.0029
ANN control 0.4988 0.9825 0.9845 0.1781 1.001 1.003 1.004 -0.0026
ANFIS optimized PI control 0.4991 0.9831 0.9841 0.1779 1.001 1.002 1.004 -0.0023
ANFIS optimized fuzzy control 0.4996 0.9857 0.9852 0.1765 0.9982 0.9976 0.9959