Fig 5. Flowchart for proposed Dual Functional DSTATCOM
Fig. 6 shows the control block diagram of dual functional DSTATCOM. The
source voltage of each phase is monitored continuously. If all the three
phases are at 1 p.u, DSTATCOM will continue to operate in CCM mode. Now,
if unbalance is experienced in the system voltage then the source
voltage in each of the three phases will now not be at 1 p.u. value
hence DSTATCOM switches itself from CCM to VCM mode of operation.
DSTATCOM will generate the reference signals such that the injected
current from the DSTATCOM maintains the load voltage in each phase at
1.pu even if the source voltage is unbalanced. The DSTATCOM will switch
from this mode to CCM only when the source voltages at each phase
restores to its normal value. Hence, using this control algorithm, only
single DSTATCOM can be used to serve against both current and voltage
related PQ problems.