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.