Stabilization of Wind Turbine Generator System by STATCOM

Like conventional power plants, wind power plants must provide the power quality required to ensure the stability & reliability of the power system. Increasing amount of wind turbine are connected to electrical power system in order to mitigate the negative environmental consequence of conventional electricity generation. While connecting wind turbine to grid it is important to understand source of disturbance that affect the power quality. In general voltage & frequency must be kept as stable as possible. This stability can be obtained by using FACTS devices. Recently voltage-source or current-source inverter based various FACTS devices have been used for flexible power flow control, secure loading and damping of power system oscillation. Some of those are used also to improve transient & dynamic stability of wind power generation system (WPGS). In this paper, we propose the static reactive compensator (STATCOM) based on voltage source converter (VSC) PWM technique to stabilize grid connected squirrel cage wind generator system. A simple control strategy of STATCOM is adopted where only measurement of rms voltage at the wind generator terminal is needed, there is no need of reactive power measurement. Fuzzy logic controller is used as the control a methodology of STATCOM, rather than conventional PI controller. The voltage sag and swell improvement of WPGS is compared with both fuzzy and PI controller. Moreover, the steady state capacitor value used with induction generator reduced by certain percentage when STATCOM is used with WPGS.

In this work, steady state characteristic and transient stability of wind turbine generator system (WTGS) are analyzed in detail with using a power system model, in which two wind farms are connected with multi-machine power system. At each wind farm terminal one three-level PWM based STATCOM is connected. Fuzzy logic controller (FLC) is used as the control methodology of the STATCOM. Since shaft system modeling of wind turbine has a significant effect on the transient stability analysis of WTGS, two-mass shaft model is adopted in this study. The capacitor bank capacity of wind generator is reduced by 15 percentages when STATCOM is installed at wind farm. As wind speed is always fluctuating, the terminal voltage of wind generator also fluctuates randomly, which has an adverse effect on the rest of the power system. It is reported that the STATCOM with reduced capacitor bank can decrease the voltage fluctuations of multi-machine power system as well as wind generator terminals. Moreover, it is shown that STATCOM can also enhance the transient stability of induction and synchronous generators when a network disturbance occurs in the power system. Both of the symmetrical and the unsymmetrical faults are analyzed. Both multi-wind generators wind farm and aggregated single generator wind farm models are used for the sake of detailed analyses. Finally, it is concluded that the STATCOM can enhance both of the steady state characteristic and transient stability of wind farms connected with multi-machine power system.

Power variation, voltage fluctuation and flicker are critical issues related to the connecting wind turbines with squirrel-cage induction generators (SCIG) into grid. This paper investigates the use of a static synchronous compensator (STATCOM) to mitigate the voltage fluctuations and improve power quality of wind turbine with SCIG. The experimental setup which contains STATCOM and wind turbine generation system (WTGS) with SCIG is designed. The control system of STATCOM is designed and implemented based on the fix-point DSP of SEED-DEC2812. The wind turbine simulator is composed of squirrel-cage induction motor (SCIM), converter ACS800, data acquisition card PCI-1710 and wind turbine model based on real time workshop of matlab/simulink. The experimental results show that STATCOM can mitigate voltage fluctuation and improve power quality of wind turbine with SCIG.

The purpose of this research is to optimize control and enhance performance for a variable speed constant frequency (VSCF) doubly-fed induction generator (DFIG) wind turbine generation system by using fuzzy logic controller. The control of the rotor-side converter is realized by stator flux oriented control and the fuzzy controller performs robust speed control. The control of the grid-side converter is carried out by a control strategy based on grid voltage orientation and it is controlled to maintain the DC link voltage stability. The results obtained from a system using the proposed fuzzy controller show more accurate control performance and faster dynamic response with almost no steady state error when compared to a system using conventional PI controller. Performances have been validated in this paper.

Comparative analysis of controllers for stability enhancement for wind energy system with STATCOM in the grid connected environment

The STATCOM (synchronous static compensator) operation can be adversely affected due to voltage source converter (VSC) over-currents and trips, during power system faults when its dynamic VAR support functionality is most required strict requirements of STATCOM losses and total system loss penalty preclude the use of PWM (pulse-width modulation) for VSC based STATCOM applications. This constraint of implementing VSC without PWM functionality, results in over- currents and trips of the STATCOM during and after system faults. In this paper, we propose an "emergency PWM" strategy to prevent over-currents (and trips) in the VSC during and after system faults, with slightly different B-H characteristics (due to manufacturing tolerances) for series connected transformers. Simulation results are presented for a 48-pulse VSC based plusmn100 MVAr STATCOM connected to a 2-bus power system. Simulation results validate the "emergency PWM" strategy to prevent VSC over-currents and to supply reactive power under all power system faults - single-line to ground, line-line and three-phase system faults.

In order to investigate the impacts of the integration of wind farms into utilities networks, it is necessary to analyze the transient characteristic of wind turbine generator system (WTGS). In most of the cases, the simple one mass lumped model is considered for stability analysis of wind generator. It is not analyzed yet which order shaft model is sufficient for transient stability analysis of WTGS. In this study, a detailed transient analysis has been done with the consideration of two mass and three mass shaft models of WTGS. Finally, it is concluded that two mass shaft model is sufficient enough for transient stability analysis of grid connected WTGS.

Flexible AC Transmission System (FACTS) controllers are advanced power electronic devices employed in electrical power systems to enhance system stability, reliability, and power transfer capabilities. These controllers enable dynamic and flexible control of various transmission parameters such as voltage, current, impedance, and phase angle, thereby improving the overall power system performance. FACTS devices are broadly classified into series, shunt, series- series, and series-shunt configurations, each designed to manage reactive power and regulate voltage either by injecting voltage in series or current in shunt with the transmission line. Well-known FACTS devices include Static Var Compensators (SVC), Static Synchronous Compensators (STATCOM), Thyristor Controlled Series Capacitors (TCSC), Static Synchronous Series Compensators (SSSC), and Unified Power Flow Controllers (UPFC), each serving specific roles in power flow control, voltage regulation, and transient stability enhancement. The integration of these controllers provides significant benefits such as increased transmission line capacity, improved voltage stability, minimized transmission losses, and damping of power system oscillations. They are capable of rapid response during transient disturbances, effectively mitigating voltage collapses and enhancing system resilience against faults and contingencies. FACTS controllers not only improve steady-state operational parameters but also address dynamic stability and transient conditions, enabling power systems to operate closer to their stability limits while maintaining security. Their deployment helps avoid costly infrastructural expansions by optimizing existing transmission assets, which is critical given environmental and economic constraints. Recent advances in semiconductor technologies and control algorithms have made FACTS devices more reliable, efficient, and adaptable to modern grids, including renewable integration and deregulated power markets. In summary, FACTS controllers play a vital role in modern power systems by providing flexible, efficient, and reliable solutions for power flow management, voltage control, and system stability enhancement, thereby supporting the evolving demands of today's complex electrical networks.

In electromechanical oscillation damping within power system, power system stabilizers (PSSs) are often deployed. However, a PSS is less effective in damping interarea oscillation and is limited by changes in network configuration due to weak tie-lines and load variations. Consequently, this paper presents a wide-area coordination approach that damps interarea oscillations using FACTS devices and phasor measurement units. We selected a static synchronous compensator (STATCOM) and static series synchronous compensator (SSSC) for realistic power system interarea oscillation damping. The performance of the coordinated FACTS installed in a power system depends on their suitable locations, sizes, tuned parameters, and remote input signal selection. Hence, we formulated a multiobjective problem to provide the STATCOM and SSSC's optimal solutions using multiobjective particle swarm optimization. In addition, we employed a participation factor to select suitable generator speed deviations as the wide area stabilizing signal. The proposed approach was tested on different configurations of the Kundur $2$-area $4$-machine test system within MATLAB and Psat environments. The outcome of the nonlinear simulation proved that the multimachine power system stability was enhanced.

FACTS devices have become significant tools for power flow study now-a-days. It has widely improved the power system reliability, operation capability and safety. It has also improved the robust control of power system. FACTS devices are generally made of power electronics devices and circuits. That’s why FACTS devices have appeared as the most outstanding innovation in the era of power electronics and power system. FACTS devices are of many types: TCSC, SVC, UPFC, IPFC, STATCOM etc. Among all the devices STATCOM has become one of the most important power system components for reactive compensation of power and Voltage stabilizing capability. In this paper we have a 6 BUS power system with a variable speed wind generator connected to a BUS. For the stochastic nature of the wind the BUS voltage becomes degraded. With the help of STATCOM, corresponding BUS voltage has been improved significantly which has been studied and simulated in our paper. We have simulated the whole system with MATLAB PSAT environment and analyzed the voltage response, rotor angle response, eigen values, participation factor etc.

This paper examines the deployment of a 25 MVA Static Synchronous Compensator (STATCOM) to improve voltage stability in a real 66 kV 525 MVA transmission network in the Middle Egypt Electricity Zone. A MATLAB/Simulink model is developed to assess the performance of the STATCOM in both normal and fault conditions, including single-phase and three-phase faults. The STATCOM regulates the voltage by adjusting it within ±10% of the nominal value and is connected to a shunt with the bus B11. Four control strategies are implemented: a proportional–integral (PI) controller, an adaptive neuro-fuzzy inference system (ANFIS), a fuzzy logic controller (FLC), and an FLC combined with a supercapacitor. FLCs outperform PI controllers in maintaining voltage stability; however, they exhibit limitations regarding their responsiveness to dynamic changes within the network. The findings demonstrate that the STATCOM enhances the voltage and current stability compared to the system without this component. The ANFIS controller demonstrates optimal performance characterized by minimal waveform fluctuations. Under standard conditions, a single STATCOM integrated with an ANFIS elevates the bus voltages to 100.382% (B10) and 101.953% (B11), surpassing the performance of the FLC (100.314% and 101.246%) and the FLC–supercapacitor combination (100.326% and 101.392%). The deployment of two STATCOM units alongside an ANFIS improves the voltage levels to 102.122% (B10) and 102.200% (B11). The findings demonstrate that the AN-FIS-controlled STATCOM enhances system performance under normal operating conditions, voltage source fluctuations, and fault scenarios. The deployment of two STATCOM units, each rated at 25 MVA and controlled by an ANFIS, significantly enhances voltage stability compared to a single unit.

Summary This paper presents a new control method for a stand-alone wind-based induction generator system with constant frequency and adjustable output voltage. The proposed generator system consists of a six-phase cage-rotor induction machine with two separate three-phase stator windings and a three-phase static synchronous compensator (STATCOM). The first stator winding is fed by STATCOM and is used to excite the machine, while the second stator winding is connected to the generator external load. The main frequency of STATCOM is determined to be constant and equal to load-requested-frequency. Because the frequency of the induced emf in the second stator winding is same as this constant frequency, the generator output frequency is independent of the load power demand and rotor speed. The conventional PI controllers are used to regulate both the generator output terminal and STATCOM dc-link voltages. Some simulation and experimental results are presented to prove the validity and effectiveness of the proposed control method. Copyright © 2016 John Wiley & Sons, Ltd.

With the expansion of electric power systems, the size and complexity of the network is increased. One of the most important drawbacks of network expansion is the reduction in the damping torque of the whole system. The lack of damping torque can lead to fluctuations and instability in the power system. With regard to this problem, power system stabilizers (PSSs) have been widely utilized to improve power system stability. However, due to some drawbacks of the conventional PSSs, the need for finding a better substitution still remains. Therefore, in this paper, the application of a static synchronous compensator (STATCOM) to improve dynamic stability of a multimachine electric power system is presented and a supplementary stabilizer based on the STATCOM is incorporated. Intelligence optimization methods such as particle swarm optimization and genetic algorithms are considered for tuning the parameters of the proposed stabilizer. Several nonlinear time-domain simulation tests visibly show the ability of the STATCOM in damping power system oscillations.

This paper describes the modeling and analysis of a 3-level Static Synchronous Compensator(STATCOM) based on space vector pulse width modulation(SVPWM). The STATCOM is configured using a 3-level Voltage Source Converter(VSC). For high power applications the 3-level VSC is surpassed the commonly used two-level VSC in several aspects such as: harmonic components, dc link voltage and semiconductor devices switching frequency. It is important to keep the voltage constant in the power system, therefore voltage regulation is needed in the power system. VSC-based STATCOM regulate voltage in the connected bus by absorbing/supplying the required reactive power. The operating characteristics of the STATCOM is validated by simulation using PSCAD/EMTDC.

This paper presents a case study for selection of Wind Turbine Generator (WTG) system based on higher reliability and economic viability. The methodology consists of evaluation of reliability, initial cost and payback period for three different hub heights of WTG system. Total reliability is calculated considering power output and components failure of WTG system. Initial cost estimation includes the land cost, permission cost, machine cost and hub height tower cost. Payback period of WTG system is estimated considering initial cost, maintenance cost and energy cost. Wind speed data from Kappadgudda wind site, Gadag, Karnataka, India is considered for the study. Reliability analysis and cost evaluation are done for seven different types of turbines at 30m, 50m and 70m hub height of WTG system. A load curve from Rampur power station, Karnataka is considered for the study. It is found from the analysis that NEPC MICON type of turbine is found to be more reliable and economical for the considered site. The proposed methodology helps financial investors to select more reliable and economical WTG system for a site.