03-05-2013, 02:15 PM
Transmission System Reactive Compensation and Stability Enhancement Using 48-pulse Static Synchronous Series Compensator (SSSC)
Transmission System.ppt (Size: 347 KB / Downloads: 25)
Paper Objectives
This paper presents the concept of Flexible Alternating Current Transmission Systems (Facts) and the Static Synchronous Series Compensator (SSSC) devicecomprising a 48 pulse-GTO DC-AC VSC converter model.
This SSSC-compensator device can provide a fully controllable series injected (Buck/Boost) compensating voltage over an identical specified capacitive and inductive range, independently of the magnitude of the transmission line current. In addition to series reactive/capacitive compensation using an external dc sustained power supply, it can also compensate for any feeder voltage drop across the inductive component
of the transmission line impedance.
This paper presents a novel d-q decoupled controller using Phase Locked Loop (PLL).
SSSC-Device Performance and Control Validation.
FACTS-Technology
Flexible AC Transmission System (Facts) is a new integrated concept based on power electronic switching converters and dynamic controllers to enhance the system utilization and power transfer capacity as well as the stability, security, reliability and power quality of AC system interconnections
Use
Power Flow Control
Series Compensation
Voltage Regulation of Long Transmission System
Economic Operation
Voltage Stability Enhancement
Harmonic SSR Torsional Mode Damping by Detuning Resonance Conditions
Basic Control Scheme of the SSSC
The direct power flow control is not effective
under some AC network contingencies. Therefore the equivalent (or injected voltage) control level that maintains the desired dynamic impedance of T.L is recommended.
Figure 5 shows the basic function of effective
decoupled control system to keep the SSSC voltage, Vc, in quadrature with the transmission line current, and only control the magnitude of Vc injection to meet the desired reactive capacitive compensation level.
Conclusions
1- The SSSC device is a controlled/injected voltage source that injects a near sinusoidal AC voltage in series with the transmission line.
2- This controlled voltage (Vs) is almost in quadrature with the transmission line current, thereby can effective as an inductive or a capacitive equivalent reactance in series with the transmission line.
3- The dynamic power flow in the Transmission line always decreases when the injected voltage by the SSSC in an inductive reactance mode and the power flow increases when the injected voltage by the SSSC in a capacitive reactance mode.
4- The Phase Locked Loop (PLL) has an block inherent time delay (about 8 millisecond). This has a great effect on the dynamic performance of the SSSC device.
5- The paper presents a novel high pulse 48 pulse GTO full model of the SSSC FACTS device as well as the new dynamic decoupled controller that minimizes the PLL-loop effect on controller fast response robustness.