Schematic diagram of SSSC 

Contexts in source publication

Context 1

... line current I abc and the line voltage V abc are sensed at the point B 2 on the transmission line of Figure 1 and are converted into d-q components using Parks’ transformation. The desired current references namely I dref and I qref are compared with actual current components I d and I q respectively and the error signals are processed in the FLC. This FLC is a nonlinear controller and not so sensitive to system topology, parameter and operating condition change as the conventional linear controller. These features make it attractive for power system applications [11, 12]. The degree of membership function used for fuzzification and defuzzzification for both the fuzzy logic controllers are shown in Figure 4 . The corresponding rules set for this process is shown in Table 3. Based on this rules set the required small displacement angle β to control the angle of the injected voltage with respect to the line current has been derived. A phase locked loop (PLL) is used to determine the instantaneous angle θ of the three-phase line voltage V abc . The current components I d and I q of the three phase line currents are used to determine the angle θ ir relative to the voltage V abc . Depending upon the instantaneous reactive power with respect to the desired value either π /2 is added (inductive) or subtracted (capacitive) with β . Thus the required phase angle is derived as θ ref = θ + θ ir + β ± ( π /2). The modulation index m derived from the active power control part of the circuit and the phase angle θ ref are applied to the PWM modulator to generate the SSSC compensating voltage. Using θ ref and m, the fundamental component of PWM inverter output voltage is obtained as ...

Context 2

... recent years, it has become more difficult to construct new generation facilities and transmission lines due to energy and environmental problems. Hence it is advisable to enhance the power transfer capability of the existing transmission lines instead of constructing new one. Flexible AC transmission systems (FACTS) provide proven technical solutions to address these new operating challenges [ 1, 2, 3]. The static synchronous series compensator (SSSC) is one of the FACTS controllers connected in series with the transmission line is used to control the power flow in it without generating classical network resonance and oscillations [4]. High performance and cost effective high power voltage source inverters (VSI) are a prerequisite for the realization of SSSC. Since conventional two-pulse inverters are not available with higher ratings, multipulse inverters [5] with higher operating range are used to cater the need in SSSC. These multi-pulse inverters can be operated at lower switching frequencies, generating symmetrical output voltages having very low harmonic components. The power converters which are the main elements in FACTS devices have complex models in which the Proportional-Integral-Derivate (PID) family of controllers failed to perform satisfactorily under parameter variations, non-linearity, load disturbances, etc [6, 7]. Moreover precise linear mathematical models are mandatory for Proportional-Integral (PI) controllers. Fuzzy logic controllers (FLC) does not need accurate mathematical model and are able to compensate the effects of uncertainties, disturbances and unmodelled system dynamics. Hence in this paper a closed loop control scheme using FLC has been developed for operating the SSSC in its most powerful control mode namely automatic power flow control mode. The performance of SSSC is verified on a single machine infinite bus power system subjected to wide range of operating conditions like faults and load variations. The SSSC is a power electronic-based synchronous voltage source that generates three phase ac voltages of controllable magnitude and phase angle. This voltage, which is injected in series with the transmission line, is almost in quadrature with the line current and hence emulates an equivalent inductive or capacitive reactance in series with the transmission line. When the series injected voltage leads the line current, it emulates an inductive reactance causing the power flow and the line current to decrease. When the line current leads the injected voltage it emulates a capacitive reactance thereby enhancing the power flow over the line. The basic schematic diagram of the static synchronous series compensator with its test system [8] is shown in Figure 1. The specifications of the test system are shown in Table 1. The feeding network is represented by a Thevenin’s equivalent circuit at bus B 1 where the voltage source is a 230×1.03 kV with a short circuit power level of 10,000 MVA and an X/R = 8. The SSSC is placed between two sections B 1 and B 2 of the transmission line as shown in Figure 1. The compensator is equipped with a source of energy, which helps in supplying or absorbing active power to or from the transmission line along with the control of reactive power ...

Context 3

... recent years, it has become more difficult to construct new generation facilities and transmission lines due to energy and environmental problems. Hence it is advisable to enhance the power transfer capability of the existing transmission lines instead of constructing new one. Flexible AC transmission systems (FACTS) provide proven technical solutions to address these new operating challenges [ 1, 2, 3]. The static synchronous series compensator (SSSC) is one of the FACTS controllers connected in series with the transmission line is used to control the power flow in it without generating classical network resonance and oscillations [4]. High performance and cost effective high power voltage source inverters (VSI) are a prerequisite for the realization of SSSC. Since conventional two-pulse inverters are not available with higher ratings, multipulse inverters [5] with higher operating range are used to cater the need in SSSC. These multi-pulse inverters can be operated at lower switching frequencies, generating symmetrical output voltages having very low harmonic components. The power converters which are the main elements in FACTS devices have complex models in which the Proportional-Integral-Derivate (PID) family of controllers failed to perform satisfactorily under parameter variations, non-linearity, load disturbances, etc [6, 7]. Moreover precise linear mathematical models are mandatory for Proportional-Integral (PI) controllers. Fuzzy logic controllers (FLC) does not need accurate mathematical model and are able to compensate the effects of uncertainties, disturbances and unmodelled system dynamics. Hence in this paper a closed loop control scheme using FLC has been developed for operating the SSSC in its most powerful control mode namely automatic power flow control mode. The performance of SSSC is verified on a single machine infinite bus power system subjected to wide range of operating conditions like faults and load variations. The SSSC is a power electronic-based synchronous voltage source that generates three phase ac voltages of controllable magnitude and phase angle. This voltage, which is injected in series with the transmission line, is almost in quadrature with the line current and hence emulates an equivalent inductive or capacitive reactance in series with the transmission line. When the series injected voltage leads the line current, it emulates an inductive reactance causing the power flow and the line current to decrease. When the line current leads the injected voltage it emulates a capacitive reactance thereby enhancing the power flow over the line. The basic schematic diagram of the static synchronous series compensator with its test system [8] is shown in Figure 1. The specifications of the test system are shown in Table 1. The feeding network is represented by a Thevenin’s equivalent circuit at bus B 1 where the voltage source is a 230×1.03 kV with a short circuit power level of 10,000 MVA and an X/R = 8. The SSSC is placed between two sections B 1 and B 2 of the transmission line as shown in Figure 1. The compensator is equipped with a source of energy, which helps in supplying or absorbing active power to or from the transmission line along with the control of reactive power ...