Supplementary control design of SVC and STATCOM using H/sub ∞/ optimal robust control

Electric arc furnace (EAF) is one of the largest loads in electric power systems. It is highly time varying and nonlinear. Its reactive power variations cause voltage fluctuations in nearby system which is known as flicker. On the other hand the nonlinear voltage-current characteristic causes strong voltage and current harmonics in EAF. To this end Flexible AC Transmission Systems (FACTS) technologies are used to mitigate the flicker and harmonics caused by EAF. The mostly used FACTS device in EAFss is Static VAr compensator (SVC) which can reduce the flicker and harmonics to some levels. Delays relevant to reactive power measurement and thyristor ignition reduce compensation capabilities of SVC. In order to prevent these delays, one can use faster compensation devices. Static Synchronous Compensator (STATCOM) may be considered as a high performance candidate for this purpose due to its fast and flexible response. In this article the performance of STATCOM is compared to SVC in EAFs plants. For this purpose the system is simulated with SVC and STATCOM in PSCAD/EMTDC using the practical EAF data records. Data records are the instantaneous EAF voltage and current recorded from EAFs in Mobarakeh steel company in Esfahan/Iran.

The bifurcation study of power system voltage stability has an important role in understanding the voltage unstable process deeply. Bifurcation theory includes both static and dynamic bifurcation. Static bifurcation study is the primary task of bifurcation theory. The bifurcation study can analyze the impact of dynamic control performance on voltage stability especially for flexible AC system(FACTS) such as static synchronous compensator(STATCOM) and static var compensator (SVC). The reactive power compensation effect of STATCOM is better than SVC. In this paper, a kind of toolbox of MATLAB, PSAT, is used for the comparative static bifurcation analysis for power system with and without STATCOM, and the bifurcation value on the point is studied. The studied results show that STATCOM can add load limit and delay static bifurcation to improve voltage stability.

Now-a-days renewable energy sources are playing a vital role in global energy systems. Wind energy conversion method is cheaper compared to other conversions such as solar and tidal etc. There are many power quality issues in wind farms such as voltage sag, swell and harmonics arise due to grid, nonlinear load and three phase faults. These voltage fluctuations can be eliminated with the help of advanced reactive power compensation devices such as SVC (Static Var Compensator), STATCOM (Static Synchronous Compensator) and DVR (Dynamic Voltage Restorer). To reduce such power quality issues, it is essential to design, model and analyse the FACTS (Flexible AC Transmission line) device. In this project, STATCOM is used as a compensating device. STATCOM is a static synchronous generator operated as a parallel connection static reactive compensator. It is capable of generating or absorbing real and reactive power. Also, the compensator performance is analysed with the help of Proportional Resonant (PR) controller device. The STATCOM is connected parallel with the transmission line. When fault occurs, it will inject or absorb the reactive power to the line through the transformer according to the voltage requirement. The whole system is simulated through MATLAB/SIMULINK application. The simulation gives the effective influence of STATCOM on the improvement of voltage profile as well as reduction of Harmonics in grid connected Wind Energy Conversion System.

Voltage sag is one of the power quality disturbances most frequently by customers because it can cause economic loss for the customers especially industries and commercial customers. The main source of voltage sags are faults in transmission and distribution beside two others namely motor large starting and transformer energizing, both the voltage sags have less effect on the equipment. Voltage sags can cause degradation performance of the equipment, and it depends on the magnitude and the duration. The voltage sags that occur in the power system can be compensated with installed Static VAR compensator (SVC) and Static synchronous compensator (STATCOM) in the distribution system bus. The purpose of the study is to compare both types of the device used to mitigate voltage sags in simulation using Alternative transient program (ATP) software. The voltage sag results from the short circuit faults. The method proposes the installation of the two compensator devices alternatively at one of the IEEE thirteen busses systems. The result shows the STATCOM is better than the SVC to handle mitigation of voltage sags compared with the SVC.

Matlab SimPowerSystems is a modern design tool that allows scientists and engineers to rapidly and easily build models that simulate power systems. Not only can you draw the circuit topology rapidly, but your analysis of the circuit can include its interactions with mechanical, thermal, control, and other disciplines. The paper covers some case studies that provide detailed, realistic examples of how to use SimPowerSystems in power system analysis. The following types of studies is coverted on the paper:1. Thyristor‐Based Static Var Compensator: Study the steady‐state and dynamic performance of a static var compensator (SVC) on a transmission system.2. Transient Stability of a Power System with SVC and PSS: Study of the application of static var compensator (SVC) and power system stabilizers (PSS) to improve transient stability and power oscillation damping of the system.3. GTO‐Based STATCOM: Study the steady‐state and dynamic performance of a static synchronous compensator (STATCOM) on a transmission system.4. Control of load flow using UPFC: Study the steady‐state and dynamic performance of a unified power flow controller (UPFC).5. Chopper‐Fed DC Motor Drive: Study of a DC motor drive with armature voltage controlled by a GTO thyristor chopper.6. VSC‐Based HVDC Link: Modeling of a forced‐commutated Voltage‐Sourced Converter high‐voltage direct current (VSC‐HVDC) transmission link.7. Three‐Phase Network with Electrical Machines: Simulation of a three‐phase power system containing electrical machines and other three‐phase models.8. Variable‐Frequency Induction Motor Drive: Study of a PWM inverter‐driven variable‐frequency AC induction motor in variable‐voltage, variable‐speed operation.

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 the transition towards renewable energy systems, the integration of large-scale renewable energy sources (RES) introduces significant operational challenges due to their intermittent nature and lack of physical inertia. This paper explores the efficacy of two Flexible AC Transmission System (FACTS) devices, the Static Synchronous Compensator (STATCOM) and the Static VAR Compensator (SVC), in mitigating the destabilizing effects associated with high levels of RES integration. Through simulation of various contingencies at a Real Time modeled 400kV Pooling Substation, the performance of STATCOM and SVC, each rated at 150 MVAr, is analyzed in maintaining grid stability. Findings highlight STATCOM’s superior dynamic response in managing voltage fluctuations and enhancing system damping compared to SVC. Specifically, STATCOM demonstrates a quicker and more robust capability to inject reactive power during disturbances, thereby ensuring rapid stabilization of grid operations. This research underscores the critical role of advanced FACTS devices in sustaining grid reliability and offers strategic insights for grid operators and policymakers aiming to optimize renewable energy integration without compromising grid stability.

A SMES (Superconducting Magnetic Energy Storage System) system with converter composed of self-commutated valve devices such as GTO and IGBT is available to control active and reactive power simultaneously. A SVC (Static Var Compensators) or STATCOM (Static Synchronous Compensator) is widely employed to reduce reactive power in power plants and substations. Owing to progress of power electronics technology using GTO and IGBT devices, power converters in the SMES system and the SVC can easily control power flow in few milliseconds. Moreover, since the valve devices for the SMES are equivalent to those for the SVC, the device cost must be reduced. In this paper the basic control system combined with the SMES and SVC is designed for large pulsed loads of a nuclear fusion power plant. This combined system largely expands the reactive power control region as well as the active one. The simulation results show that the combined system is effective and prospective for the nuclear fusion power plant.

According to the grid codes, on wind farm for reactive power compensation and voltage stability requirements, this paper analyzes the extent of a static synchronous compensator (STATCOM) to voltage stability of doubly fed induction generator (DFIG) wind farm, compared to a static VAR compensator (SVC), and proposes a new scheme for coordinated control of reactive power between DFIG and STATCOM, to do this, DFIG stator, grid-side converter (GSC) and STATCOM supply reactive power to the grid coordinately, where the advantages and disadvantages of rotor-side converter (RSC) and GSC are taken into more consideration, and the reactive power control ability of DFIG is fully utilized. Based on test system, research results show that, STATCOM can provide more reactive power than SVC for voltage stability under the same capacity, especially during the serious voltage sag; The coordinated control scheme can not only improve the transient voltage stability, but also help reducing the capacity of STATCOM so that save the cost of investments in wind farms.

Today, dc arc furnaces are supplied by thyristor rectifiers. Because of the phase control strategy on the rectifiers, the arc voltage swings induce large reactive power variations on the power network and a static VAr compensator (SVC) or a static synchronous compensator (STATCOM) is always added to avoid flicker effect. In this paper, the authors present a new control strategy which suppresses the flicker effect and increases the furnace productivity. To supply the dc arc furnace, the ac/dc converter is based on diode rectifiers and choppers with a constant power control strategy. Consequently, the ac/dc converter can operate without a STATCOM or an SVC. To evaluate the gain in flicker and furnace productivity, simulations are done with Matlab software. These simulations take into account arc voltage measurements on a 100-MW dc arc furnace and allow for comparison of the different solutions.

Flexible alternating current transmission systems (FACTS) are power electronics-based static controllers which control the transmission network parameters to improve system performance. They are used to solve various power system problems which include; voltage stability, voltage deviation and power losses. However, these devices need to be optimized to achieve desired results. This paper presents the application of firefly algorithm (FA) to optimize Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM) for voltage profile improvement and power loss minimization on IEEE 14 bus system. The results showed that the active and reactive power losses were minimized by 8.7 and 10.1%, respectively with FA optimized SVC and 10.7 and 14.7%, respectively with FA optimized STATCOM. Therefore, the optimal allocation of SVC and STATCOM improve the performance of the network which indicates the effectiveness of FA in optimizing SVC and STATCOM.KeywordsFACTSSTATCOMSVCFAVoltage magnitudePower loss

The surge in demand for electricity has driven the power system to operate at a lower efficiency level. With the many actions taken to improve the electric grid, voltage unbalance and line overload have become challenging problems to address. Voltage control can be determined in generation, transfer, and electricity usage. When the power system is under stress, reactive current unbalance significantly contributes to voltage instability. To maximize the efficiency of a power system, flexible transmission systems system (FACTS) devices must be used most effectively and feasible. FACTS devices like Static VAR Compensators (SVCs) and Static Synchronous Compensators (STATCOMs) can reduce instability in heavily burdened lines, resulting in lower system losses and more excellent network reliability. In this paper, FACTS controllers such as SVC and STATCOM are incorporated in the Kurdistan power system simulated by using PSAT software based on MATLAB for the improvement of voltage profile, minimization of the system losses, and cost of the system. Also, the graphical comparisons of the results are presented to investigate the effectiveness of the proposed methods.

This paper presents and compares the measured impedance at the relaying point in the presence of shunt connected flexible alternating current transmission system (FACTS) devices, i.e. static VAr compensator (SVC) and static synchronous compensator (STATCOM). The presence of the shunt connected FACTS devices on a transmission line greatly affects the measured impedance at the relaying point. The measured impedance itself depends on the power system structural conditions, pre-fault loading, and especially the ground fault resistance. In the presence of shunt connected FACTS devices, their structural and controlling parameters as well as their installation position, affects the measured impedance. Here, the measured impedance at the relaying point is calculated due to the mentioned affecting parameters, and compared in the two cases of SVC and STATCOM.

The wind farm based on Doubly Fed Induction Generator (DFIG) is built. Not only it can be as active power source to provide active power to network, but also as reactive power source to stabilize voltage or supply Var compensation (reactive power absorbed or generated). Therefore, Var coordinated control strategy is proposed, instead of expensive equipments, such as Static Var Compensator(SVC) or Static Synchronous Compensator (STATCOM), in order to provide sufficient reactive power to maintain system stability. DFIG comprehensive model is built based on correlation models in Dig SILENT/Power Factory. The eigen value analysis method is employed to verify its impact on low-frequency oscillation modes and small signal stability of power system integrated with wind farm. The results from eigen value analysis are elucidated the effectiveness of Var coordinated control in DFIG system.

The contribution of wind power in conventional generation is increasing rapidly now-a-days. Hence a better understanding of wind power plants is required. But the wind power plants generally containing induction generators exhibit a rather different behavior than the conventional power plants which use synchronous generators. The purpose of this paper is to analyze and study transient stability of a wind farm based on conventional fixed speed Induction generator when it has been integrated with a weak grid. A comparative analysis of the transient stability improvement of a FSIG wind plant has been done, when it is supported with FACTS like S.V.C and STATCOM of equal ratings. Single case of transient condition i.e. a three phase fault has been studied by simulation. With the increase in demand of power and decrease of fossil fuels, mankind has been forced to search alternative sources for the generation of electricity. Wind power in spite of being stochastic in nature has proved itself as a viable solution to this problem. As the wind turbine technology is developing at a good pace, more and more wind power plants are being integrated with the conventional form of generation. With the increase in the ratio of wind generation to conventional generation, several problems related with integration of wind farms have emerged. These problems are due to distinct properties of the generators used with the conventional form (Thermal & Hydro) of generation and wind based generation (1)-(4). In thermal and hydro power based generation synchronous generators are used while in wind based generation mostly induction generators are used. Induction and synchronous generators do not exhibit similar behavior during power system stresses (transients). Moreover, increase in wind power based generation requires a reliable transmission system for power evacuation to the load centers. As the wind farms are mainly concentrated in far flung and rural areas their interconnection with the grid becomes a problem. This problem is mainly due to the existence weak transmission grids in the rural areas (1)-(4). Earlier when the share of wind power generation as compared with the conventional generation was low, during transient conditions; whenever the power system reached on the verge of instability the wind farm was disconnected from the grid and was reconnected when transients passed away. But as the share of wind power in the conventional generation increased, the practice of disconnecting the wind farms from the rest of the grid led to the drop in frequency of the power system. So now-a- days even if a fault occurs in the power system somewhere near the wind farms, they still remain connected with the grid for a critical time period. This phenomenon is called fault ride through (FRT) in wind farms (5). This paper has studied a transient condition (fault) in a grid connected fixed speed induction generator based wind farm and its fault ride through performance. A comparison of the performance of fact devices like static var compensators (svc) and static synchronous compensators (statcom) in improving the transient stability of wind farms during fault is also done.