Novel control for series power quality controller without external DC energy source

The ride through capability is a major index of the performance for series power quality controllers (SPQC), while a SPQC using traditional control, i.e. either in-phase control or energy optimized control, only provides limited maximal ride through time if no energy storage capacitor is employed. A novel control strategy for SPQC was proposed in this paper, which increased the ride through capability by automatically drawing certain amount of active power from the line input and supplied them to the SPQC to afford the power loss when compensating input line voltage disturbance, so no energy storage capacitor was required even for continuous compensation. A specific phasor diagram representation of SPQC was introduced. The load current phasor was chosen as reference phasor, leading to simple relationship among the related variables within SPQC. A phasor diagram was carried out accordingly, for both the input line voltage disturbance state and the normal state. The compensating voltage magnitude and the maximal depth of the line voltage sag that SPQC with such a control strategy could fully compensate was obtained quantitatively. The system detailed power flow was also discussed in a quantitative manner. A simple and unified implementation method was proposed and analyzed extensively based on system energy equilibrium. The computer simulation and prototype experimental results are shown to verify the validity of all the analysis of control.