05-07-2012, 04:48 PM
APPLICABILITY AND STRATEGY OF FACTs DEVICES IN ELECTRICAL SYSTEM
APPLICABILITY & STRATEGY OF FACTs DEVICES.docx (Size: 1.19 MB / Downloads: 37)
SSSC
In this Report the effects of a Static Synchronous Series Compensator, which is constructed with a 48-pulse inverter, on the power demand from the grid are studied. Extensive simulation studies were carried out in the MATLAB simulation environment to observe the compensation achieved by the SSSC and its effects on the line voltage, line current, phase angle and real/reactive
power. The designed device is simulated in a power system which is comprised of a three phase power source, a transmission line, line inductance and load. The system parameters such as line voltage, line current, reactive power Q and real power P transmissions are observed both when the SSSC is connected to and disconnected from the power system. The motivation for modelling a SSSC
from a multi-pulse inverter is to enhance the voltage waveform of the device and this is observed in the total harmonic distortion (THD) analysis performed at the end of the paper. According to the results, the power flow and phase angle can be controlled successfully by the new device through voltage injection. Finally a THD analysis is performed to see the harmonics content. The effect on the quality of the line voltage and current is acceptable according to international standards.
SIMULATION REWSULT:
The circuit is simulated to observe the free (uncontrolled) power flow over the line. The real power P demanded by the load is supplied by the three phase source and transmitted by the transmission line between B1 and B2. The simulations were performed to see the power demands, voltage and current supplied by the source, transmitted by the line and received by the load. Following these observations a Static Synchronous Series Compensator (SSSC) is operated to decrease the Q-flow over the line by compensating the reactive power demanded by the system.
First the simulations were carried out when the SSSC was switched off. The
three phase source voltage and current waveforms along with the real and reactive power flows were obtained as shown in Fig. 2. The same parameters were observed after switching on the SSSC and the waveforms shown in Fig. 3 were obtained. The signal over the feedback loop and the control signals for the closed loop control are given in Fig. 1
Analyzing the results and the waveforms it can be easily said that the synchronization and compensation are performed satisfactorily by the designed SSSC. The feedback signal which is generated from the line current flowing over the power line is used to generate the PWM signals. This way both synchronization and a 90 degree phase difference with the line current are achieved. In order to interpret the results, a comparative approach would be appropriate for the waveforms obtained before and after the SSSC is operated. The line voltage and current shown in Fig. 3 clearly depict the phase difference between them induced by the inductive current drawn by the system which
decreases the power factor of the source side. Accordingly the reactive power Q drawn from the source reaches considerable values. The level of the real power P should also be noted here in order to compare it with the value obtained under the compensation condition.