Static Synchronous Series Compensator Research Articles

Optimal fractional SSSC auxiliary controller for power system low frequency oscillations damping improvement

This work presents a new controller design to improve inter-area low frequency electromechanical oscillations (LFEOs) damping and enhance the overall stability of the electrical network. The control strategy used the static synchronous series compensator (SSSC) based flexible AC transmission systems (FACTS) series-type device mainly performed for power flow and voltage regulation. Then, a fractional order proportional integral derivative (FOPID) is introduced as an auxiliary controller for the SSSC using the difference of rotor speed deviations of generators as input signal to improve the oscillations damping. Moreover, genetic algorithm (GA) is applied to seek for optimum controller gains. The proposed control approach is examined on two-area four-machine (2A4M) test system. The FOPID performance is compared with the integer order proportional integral derivative (PID). Obtained results show that the proposed SSSC-based FOPID controller achieves high performance for enhancement of inter-area low frequency oscillations damping.

Analysis of the combined effects of SVC and SSSC controllers to improve power system stability

The primary challenge facing the electricity transmission system in the aftermath of the disruption is reestablishing stability. Through adjustment of the transmission parameters, the Flexible AC Transmission System (FACTS) devices have the potential to bring the system back into stable operation. It has been shown that using many FACTS devices together is more effective than using any one device alone. In this paper, the concept of coordination control between a Static Var Compensator (SVC) and a Static Synchronous Series Compensator (SSSC) is suggested in order to make the system more stable. The equivalent impedance of the line may be reduced by using the SSSC, which will also result in improved active power transfer capabilities for the line. A static var compensator, often known as an SVC, is used for shunt compensation in order to keep the bus voltage magnitude stable. When compared to the use of a single device, the use of SVC and SSSC coordinated control results in a much quicker arrival to the steady state response of the system. Both of these devices are controlled by using the same signal input tracking. It has also been seen that the system has resumed its previous synchronized state.

Reliable protection for static synchronous series compensated double-circuit transmission lines based on positive sequence active power calculations using PMUs

Static Synchronous Series Compensator (SSSC) allows dynamic control capabilities of transmitted power. Unfortunately, inserting SSSC in transmission lines (TLs) disturbs impedance-based distance relays as their directionality and reachability are affected by overreaching or underreaching. This paper proposes an approach for protecting double-circuit TLs compensated with SSSC. It relies on the centralized wide-area protection architecture to calculate a proposed driven index: the rate of change of positive sequence active power difference. Phasor measurement units (PMUs) at TL ends estimate voltage and current phasors to calculate the positive sequence active power at TL ends and send them to the system protection center that evaluates the index and gives the trip decision or not. Ensuring the sensitivity, dependability, and security of the approach is essential. So, the overall scheme integrates two other algorithms. One is based on the polarities of the incremental power at both ends to determine whether the fault is internal or external. The other evaluates the phase angle of the integrated impedance to deactivate the power swing-blocking function for fault detection. The scheme's effectiveness is validated comprehensively through extensive simulation tests for fault and system conditions. The results show that the proposed approach is fast, secure, selective, and reliable.

Control of a transformerless static synchronous series compensator for unbalanced voltage compensation

AbstractThis paper explores a transformerless static synchronous series compensator (TL‐SSSC) for mitigating voltage distortion in a power distribution line with renewable generations. A novel deadbeat current control scheme with time delay compensation is proposed which models the a‐b‐c three phase line with TL‐SSSC plus its LC filters and predicts the compensating voltages to be injected by the TL‐SSSC. Without resolving measured voltages and currents into positive and negative sequences, the scheme is computationally efficient and effective in mitigating voltage distortion due to faults occurring at different locations along the distribution line. It also eliminates the problem of inaccurate compensation voltage caused by inverter filter choking voltage drop. The paper also analyses the power controllable ranges for a TL‐SSSC under different unbalanced voltage ratios. The proposed TL‐SSSC and control scheme is validated using Typhoon Hardware‐In –Loop (HIL) device. Experimental results on mitigation unbalanced voltages of a 11kV transmission line confirm the effectiveness and high performance.

Rotor angle stability improvement by coordinated control of SVC and SSSC controllers

After a disruption in the power transmission system, the most crucial challenge is restoring the system’s stability. The FACTS devices can manipulate the transmission parameters to bring the system back into stable operation. This paper discusses the operational concepts and applications of FACTS in power systems such as the Static Var Compensator (SVC) and the Static Synchronous Series Compensator (SSSC). When combined with the other devices, the effectiveness of each individual device is increased. This paper proposes the coordinated control of SVC and SSSC to improve system stability. The SSSC can be utilized to lower the line’s equivalent impedance and improve its operational power transfer capabilities. The SVC is used for shunt compensation to maintain bus voltage magnitude. Furthermore, the steady-state response of the system is faster when SVC and SSSC coordinated control is employed compared to a single device. The resultant variable signal of the SSSC controller is tracked to control the SVC controller. A significant fault is introduced in the tie-line of the inter-area system to analyse and validate the proposed coordinated control. MATLAB/Simulation results are presented for the proposed approach, and also a real-time simulator is used to validate the simulation results.

A preordainment approach for design of auxiliary damping controller and SSSC tuning to enhance SSR mode stability in DFIG based windfarm

ABSTRACT Sub-synchronous resonance (SSR) is a growing concern in wind turbine generators-based series capacitive compensated networks at low wind speed and peak compensation levels. It is feasible to increase the stability of SSR mode caused by a transmission line’s passive series compensation by providing active compensation using a flexible ac transmission system controller cooperating with an auxiliary damping controller. This paper presents preordainment and enhancement of SSR mode in DFIG-based series capacitive compensated line by incorporating an additional damping controller into the static synchronous series compensator (SSSC). The auxiliary damping controller modulates the reactive voltage injected by SSSC into the transmission line by considering the appropriate input control signal, reflecting the SSR instability, and giving the maximum damping to the SSR mode. The optimal input control signal is determined via residue analysis, and the design procedure of the auxiliary damping controller is presented using root locus plots. The root locus plots offer a visual representation of the loci for each mode and preordain eigenvalues for new stability, which aids in the design of the auxiliary damping controller. This feature allows to predetermine the SSR mode eigenvalue while before connecting it with SSSC. Accordingly, it provides a controlled dampening to SSR mode such that the desired damping ratio for SSR mode can be achieved without influencing the stability of other modes. The impact of the designed auxiliary damping controller is examined at high compensation levels and low wind speed. The eigenvalue analysis results show that the preordained eigenvalues found using root locus plots are correct and the proposed approach predominantly enhances the stability of SSR mode. The fast Fourier transform (FFT) analysis and transient simulations are used to show the detuning and dampening of SSR mode. The proposed work is executed using MATLAB/Simulink.

Squirrel search algorithm based intelligent controller for interconnected power system

ABSTRACT In this paper, a novel controller, namely fractional order fuzzy proportional-integral-derivative (FOFPID) has been proposed for the dual area power system of hydro-thermal-gas units (DAHTG). The squirrel search algorithm (SSA) is implemented to achieve the optimal values of the controller tuning parameters. Further, various non-linearity constraints, such as governor dead band (GDB), generation rate constraint (GRC) and communication time delays (CTDs) have also been considered to test the effectiveness of the proposed controller in a real-time environment. The step load of 10% is provided as the disturbance under the regulation. In addition, the coordinated strategy of a static synchronous series compensator (SSSC) device and superconducting magnetic energy storage (SMES) is employed in the proposed system to enhance the system’s performance. Further, the accuracy, effectiveness and robustness of the proposed controller are revealed through the comparative analysis with classical PID and traditional fuzzy PID controllers. Furthermore, presented controller efficacy is revealed with the other recently reported control techniques by implementing it on the two-area thermal system with GDB. The comparative analysis shows the better performance of the proposed controller than these two. Finally, the sensitivity analysis is performed to check the controller robustness.

Utilization of adaptive swarm intelligent metaheuristic in designing an efficient photovoltaic interfaced Static Synchronous Series Compensator

To cope with the growing load demand of power system due to world’s rapid socio-economic growth, the system compels to run with increased load. Hence, the system must sustain at maximum loading level, termed as the Maximum Loadability Limit (MLL) of the system, without violating its security limits. To increase the system-MLL further the Static Synchronous Series Compensator (SSSC) among existing Flexible AC Transmission Systems (FACTS) devices has been preferred here for its capability of compensating the real and reactive power losses simultaneously. Initially, the SSSC parameters are optimized which are further validated through the dynamic model of the Photovoltaic (PV) interfaced SSSC (PV-SSSC) in MATLAB/SIMULINK. To make the PV-SSSC more efficient, firstly, the maximum feasible power can be acquired from PV system using a robust Maximum Power Point Tracking (MPPT) technique. Secondly, Firing Angle Optimization (FAO) can improve the output power quality of the inverter in SSSC. Thus, this research handles three optimization problems separately i.e., the SSSC parameter optimization, the FAO (minimization), and the MPPT (maximization) problems. For solving such complex, nonlinear, and nonconvex engineering optimization problems, a recently developed swarm-based metaheuristic namely Levy Flight motivated Adaptive Particle Swarm Optimization (APSOLF) technique is employed. Moreover, the superiority of APSOLF is justified over contemporary state-of-the-art techniques using statistical analyses. The APSOLF-based-MPPT can achieve tracking-efficiency above 99.8% and the lowest settling-time. The APSOLF-based-FAO attains 6.7148% THD satisfying the IEEE-519 standard without any filter circuit The MLL point enhancement and bus voltage profile improvement are also the notable observations.

The Impact of Serial Controllable FACTS Devices on Voltage Stability

As the world's population continues to grow, the demand for electricity is also increasing rapidly. Ensuring the quality of power supply, voltage stability, unity power factor, and minimizing power losses is essential for delivering power to every user end. In order to achieve this, compensation techniques are needed. This project focuses on Serial controllable Flexible AC Transmission Systems (FACTS) devices, such as Controllable Series Compensator (CSC) and Static Synchronous Series Compensator (SSSC), which have a significant impact on the voltage and power stability of an electric power system (EPS). The mathematical derivation of the voltage dependency of CSC and SSSC is extracted for the single-load infinitive-bus model (SLIB). New analytical equations are developed to compare the impact of CSC and SSSC on voltage stability in a five-bus system. The results of the analysis are expected to reveal that CSC has a crucial role to play in enhancing voltage stability, and its impact is greater than that of SSSC when considering equal CSC and SSSC MVA ratings. When it comes to voltage controllability, SSSC (Static synchronous series compensator) is superior to CSC (Controllable Series Compensator), especially in situations where there are having low voltages or having low loads.

Oscillation Damping Neuro-Based Controllers Augmented Solar Energy Penetration Management of Power System Stability

The appropriate design of the power oscillation damping controllers guarantees that distributed energy resources and sustainable smart grids deliver excellent service subjected to big data for planned maintenance of renewable energy. Therefore, the main target of this study is to suppress the low-frequency oscillations due to disruptive faults and heavy load disturbance conditions. The considered power system comprises two interconnected hydroelectric areas with heavy solar energy penetrations, severely impacting the power system stabilizers. When associated with appropriate controllers, FACTs technology such as the static synchronous series compensator provides efficient dampening of the adverse power frequency oscillations. First, a two-area power system with heavy solar energy penetration is implemented. Second, two neuro-based controllers are developed. The first controller is constructed with an optimized particle swarm optimization (PSO) based neural network, while the second is created with the adaptive neuro-fuzzy. An energy management approach is developed to lessen the risky impact of the injected solar energy upon the rotor speed deviations of the synchronous generator. The obtained results are impartially compared with a lead-lag compensator. The obtained results demonstrate that the developed PSO-based neural network controller outperforms the other controllers in terms of execution time and the system performance indices. Solar energy penetrations temporarily influence the electrical power produced by the synchronous generators, which slow down for uncomfortably lengthy intervals for solar energy injection greater than 0.5 pu.

Stability Enhancement of DFIG Wind Farm Using SSSC With FOPID Controller

The wind power generation has become more important nowadays to meet the increase in power demand. DFIG based wind power generation is the recent and used in many countries due to its better power controllability. The controllers like Proportional Integral (PI) are used for the stabilization of the waveforms of the supply system. The change in controllers produces better oscillation damping in recent days. The effect of varying the wind input to generate power using the wind turbine resulting in instability in the power system because of the control is done on a grid supply. This paper aims to proposes an optimum FOPID controller for damping power system instability using a Static Synchronous Series Compensator (SSSC) system that takes into account the dynamics of wind energy conversion systems (WECS) connected to a infinite grid. The WECS model, which includes variations in wind supply to the wind turbine, has been developed to test the durability of the optimized controller that was developed to damping power system oscillations. The controller used to take the power system dynamics into account. A new controller is being designed to include a corrective measure for the damping the oscillations to adjust the instability caused by wind supply variations. The controller helps to tune the controller settings that lead to the achievement of the power oscillation damping objectives. These results are compared with conventional PMSM based wind turbine system.

Enhanced Control Designs to Abate Frequency Oscillations in Compensated Power System

The interconnection of transmission, distribution, and generation lines has established a structure for the power system that is intricate. Uncertainties in the active power flow are caused by changes in load and a growing dependence on renewable energy sources. The study presented in this paper employs several controlling strategies to reduce frequency variations in series-compensated two-area power systems. Future power systems will require the incorporation of flexible AC transmission system (FACTS) devices, since the necessity for compensation in the power system is unavoidable. Therefore, a static synchronous series compensator (SSSC) is installed in both areas of our study to make it realistic and futuristic. This makes it easier to comprehend how series compensation works in a load–frequency model. With the integration of electrical vehicles (EVs) and solar photovoltaic (PV) systems, several control strategies are presented to reduce the frequency oscillations in this power system. Particle swarm optimization (PSO) is used to obtain the best PI control. To improve results, this work also covers the design of fuzzy logic control. In addition, the adoption of neural network control architecture is proposed for even better outcomes. The outcomes clearly show how well the proposed control techniques succeeded.

Transient stability enhancement using optimized PI tuning of static synchronous series compensator in wind power conversion system

Power systems are expanding comprehensively with the increase in load demand from both residential and industrial usage. Renewable energy is penetrating the power system to satisfy the power needs of the load demand. With its potential to generate power and compensate for a large portion of the load demand, wind generators make a major renewable power contribution. Power oscillations inherent in wind generator integration with the grid are a power quality issue to be addressed. Oscillation damping using flexible AC transmission system (FACTS) devices is a relevant solution for the power quality issue. There are multiple reasons for power oscillation. Mainly, power systems encounter fault conditions. The faults can be cleared, and the power system tries to retain stability. Sometimes, the system fails due to a longer settling time. A series-connected FACTS device utilized as a series compensator is referred to as a static synchronous series compensator (SSSC). Controlling the flow of electricity over a transmission line using this method is incredibly efficient. The capacity to switch between a capacitive and an inductive reactance characteristic is necessary. The SSSC regulates the flow of power in transmission lines to which it is linked by adjusting both the magnitude of the injected voltage and the phase angle of the injected voltage in series with the transmission line. This allows the SSSC to manage the power flow in the transmission lines. It does it by inserting a voltage that can be controlled into a transmission line in series with the fundamental frequency. This paper develops the optimally tuned SSSC in the wind-integrated grid system to dampen the oscillation. Teacher–learner-based optimization (TLBO) and gray wolf optimization (GWO) algorithms are used to tune the PI controller to improve the damping response. The obtained results show that the damping performance of the proposed controller is better than that of the other traditional controllers.

The use of numerical method in an electric grid coupled to a wind farm to compare different kinds of flexible AC transmission systems

The PSAT software was used in this study to analyse and compare the performance of hybrid compensators such as SSSC-STATCOM (controllers), TCSC-SVC (compensators), and UPFC in an electric grid coupled to a wind farm. The flexible AC transmission system (FACTS) technology is used to provide a continual power flow and to provide new ways to control the electric system network. In the FACTS devices, the UPFC (Unified Power Flow Controller) is one of the most adaptable, flexible, and complicated power electric devices. The active and reactive power flows and the local voltage on the bus can be regulated by UPFC; it can also resolve the problem of harmonics. The TCSC (Thyristor-Controlled Series Capacitor) consists as a series-compensating capacitor shunted by a thyristor-controlled reactor. The SVC (Static Var Compensator) is the first shunt generation FACTS controller. We can observe that the UPFC controller has an effective power flow control, shorter setting time and a shorter overshoot. The UPFC obtained a well-known reputation for high controllability in power systems. The multilevel Unified Power Flow Controller can be operated in Static Synchronous Compensator (STATCOM), in Static Synchronous Series Compensator SSSC and exactly in the UPFC compensator. The results of this research compare the hybrid controllers and investigate the effects of TCSC-SVC, SSSC-STATCOM, and UPFC on voltage, phase angle stability, and the active and reactive power in the tested system. The purpose of this comparison is to improve dynamic voltage regulation, especially when the utilisation of nonlinear loads and the presence of fault and breaker rise. These hybrid controllers have been shown to outperform series or shunt compensators; however, when compared to hybrid compensators SSSC-STATCOM, TCSC-SVC, and UPFC, the results employing the numerical method in the UPFC are more significant. The UPFC is the best hybrid controller in this study, and the compensators SSSC-STATCOM outperform the controllers TCSC-SVC.

Optimal fractional SSSC damping action for variable wind penetrations

An optimal fractional SSSC based control action has been proposed in this work for enhancing small signal stability of power system pertaining to intermittent variations in wind penetrations. The parameters of controllers are tuned by sailfish algorithm and ITAE based objective function has been chosen for minimization problem. A three machine system has been considered in this work with different operating conditions and step with random variations in wind penetrations have been executed with different machines and subject to which the system response and eigen values are analyzed. Based on system response it is observed that subject to intermittent variations in wind source the small signal stability is hampered due to increased power system oscillations and by properly tuning the fractional lead-lag control action based on static synchronous series compensator. These oscillations can be damped efficiently. The performance of proposed sailfish algorithm (SFA) tuned SSSC controlled action has been compared with PSO and DE algorithms subject to different case studies.

Wide-area damping control system for large wind generation with multiple operational uncertainty

• Illustrates the contribution of wind generation, and investigates the influence of the grid-forming mode-based VSWT-DFIGs. • Coordinated design of wide-area damping controller for utility-scale wind generation power plants considering time delays uncertainty. • Optimization is used to optimize the parameters of damping controller. • Contains case studies on a large power system, including FACTS, and wind generation. • MATLAB/Simulink-based nonlinear simulations are performed, for variable wind speed, 3-phase faults, and dynamic load model. The large integration of wind generation resources into power systems may causes low-frequency oscillations and deterioration in power system stability. This paper presents a novel coordinated approach-based Wide-Area Damping Control System (WADCS) for large wind generation integrated power system, while taking into consideration of the operational uncertainties. The coordinated WADCS approach is used to enhance the damping of inter-area oscillations while maintaining the voltage and frequency in the prescribed range. In a coordinated WADCS, a wide-area damping controller is coordinated with the rotor side converter model of wind generation resources (WGRs). The Static compensator (STATCOM) is used to enhance voltage and reactive power support for WGRs. To provide the additional damping, a static synchronous series compensator (SSSC) is also employed with the WADCS. The geometric measures of controllability/observability and residues method is utilized to select the appropriate input control signals and optimal location of wide-area damping controller. A multi-objective grey wolf optimizer (MOGWO) algorithm is used to optimize the parameters of the wide-area damping controller to enhance the damping. MATLAB/Simulink-based nonlinear simulations are performed considering operational uncertainties such as variable wind speed, 3-phase faults, variable load, and time delays to demonstrate the efficacy of the proposed coordinated control for modified WGRs integrated test power system.

Power System Stability Enhancement Using Robust FACTS-Based Stabilizer Designed by a Hybrid Optimization Algorithm

Improving the stability of power systems using FACT devices is an important and effective method. This paper uses a static synchronous series compensator (SSSC) installed in a power system to smooth out inter-area oscillations. A meta-heuristic optimization method is proposed to design the supplementary damping controller and its installation control channel within the SSSC. In this method, two control channels, phase and magnitude have been investigated for installing a damping controller to improve maximum stability and resistance in different operating conditions. An effective control channel has been selected. The objective function considered in this optimization method is multi-objective, using the sum of weighted coefficients method. The first function aims to minimize the control gain of the damping controller to the reduction of control cost, and the second objective function moves the critical modes to improve stability. It is defined as the minimum phase within the design constraints of the controller. A hybrid of two well-known meta-heuristic methods, the genetic algorithm (GA) and grey wolf optimizer (GWO) algorithm have been used to design this controller. The proposed method in this paper has been applied to develop a robust damping controller with an optimal control channel based on SSSC for two standard test systems of 4 and 50 IEEE machines. The results obtained from the analysis of eigenvalues and nonlinear simulation of the power system study show the improvement in the stability of the power system as well as the robust performance of the damping in the phase control channel.

Transient stability increase of multi-machine power system by using SSSC and DFIG control with TEF technique and super twisting differentiator

This paper suggests a nonlinear controller of a Static Synchronous Series Compensator (SSSC) and a doubly-fed induction generator (DFIG) for transient stability enhancement by transient energy function (TEF) technique and super-twisting differentiator in the multi-machine power system. Initially, the TEF approach is employed to damping control and stability enhancement in a multi-machine power system including an SSSC, DFIG, and synchronous generator (SG). Then, the signals of time-derivative in the controller with a super-twisting differentiator are estimated. The significance and novelty of this work are the employs of the TEF method obtained for the multi-machine power system containing DFIG and SG. Another novelty is the use of the DFIG and SSSC simultaneous control whose uncertain parameters are estimated with a super-twisting differentiator. The feature of the nonlinear control approach is robust versus modifications in the topology of the system. Simulation is performed on the IEEE 9-bus system to appraise the operation of the nonlinear controller approach compared to back-stepping and sliding mode control. The simulation results demonstrate that the nonlinear controller approach satisfactorily reduces the first swing of oscillations.

Design and Analysis of FOPID-Based Damping Controllers Using a Modified Grey Wolf Optimization Algorithm

This study proposes a novel modified grey-wolf optimization algorithm (MGWOA) to enhance power system stability. The power system stabilizer and static synchronous series compensator (SSSC) are used as damping controllers. Additionally, fractional-order PID (FOPID) controller is used to handle the system nonlinearities and thus achieve better performance. The control parameters are tuned using the proposed MGWOA method which has been verified on unimodal and multimodal functions. Single-machine infinite bus (SMIB) and multimachine power system (MMPS) are taken as case studies to analyze the efficacy of the proposed controller. Minimization of rotor speed deviation is considered an objective function. The results obtained from the MGWOA-tuned FOPID-based damping controllers are compared with those obtained using recently developed efficient and competitive heuristic algorithms. It was observed that the MGWOA method is well-suited for damping low-frequency oscillations. Furthermore, statistical analysis is performed on the obtained results to justify the superiority of the MGWOA method. The simulation results suggest that the MGWOA exhibits superior performance characteristics when applied to a real power system.

Power system transient stability improvement with FACTS controllers using SSSC-based controller

Early power systems were rudimentary and local in nature. Power consumption has risen quickly in recent years, resulting in more complicated systems. However, expansion of transmission and generating is limited due to limited resource availability and tight environmental regulations. As a result, today's power systems are increasingly loaded and running under stress, putting them close to their transient stability limits. The study discussed in this paper focuses on employing contemporary PSS to improve power system reliability. The work presented in this thesis mainly focuses on power system stability improvement using modern PSS. In modern power systems trend of using wide area damping controllers and wide area signals are increasing. Also Flexible AC Transmission Systems (FACTS) based controllers are most suitable for stability enhancement and power control. This method proposed tie line power as a broad area control signal for the Static Synchronous Series Compensator (SSSC) based controller based on the geometric measure of joint index value. Kundur's two-area, four-machine system is controlled by this controller. For this system, the effectiveness of the selected signal is applied to an SSSC-based controller. The results reveal that the picked signal performs better than the non-selected signal (rotor speed deviation).