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This paper presents improved indices to evaluate the contribution of reactive power compensators at HVdc converter terminals. The presence of such compensators impacts converter performance, such as the maximum available power (MAP) limit, susceptance to commutation failure, fault recovery time and temporary over voltage. Traditionally, the Effective Short Circuit Ratio (ESCR) has been used to indicate system strength. However, this index cannot be directly applied when power-electronics based converters are used to provide the reactive power support. The approach of this paper is to use an improved form of the ‘Apparent increase in Short Circuit Ratio’ (AISCR) index to quantify the impact of the compensator on the HVdc system. This index is evaluated by comparing the performance with the reactive power device with a system without the device, but having the same performance. The paper shows that a single AISCR index cannot quantify all behaviors and suggest modifications to AISCR for each of several HVdc phenomena. In this paper two types of compensators are considered – the Synchronous Compensator and the Static Synchronous Compensator (STATCOM). [ABSTRACT FROM AUTHOR]

This letter proposes an extended SVC model with thyristor firing angle law to improve transient performances of frequency and voltage of multi-machine power systems. A firing angle control synthesis framework for imposing any desired SVC susceptance value without linearization around a fixed operation point is proposed. In light of this method, the designed firing angle controller only requires local bus measures and parameters. The performance of the extended firing angle-controlled SVC model is evaluated on a 150-bus 27-machine power system and compared with conventional SVC model. [ABSTRACT FROM AUTHOR]

DC ice melting is an effective technical method against ice disaster on transmission lines. To satisfy the demand for simultaneous de-icing and reactive power compensation for substations, this paper proposed a large-capacity low-cost DC deicer with reactive power compensation, which is mainly composed of rectifier transformer, Static Var Generator (SVG) and diode rectifier. In the proposed topology, SVG and diode rectifier share the rectifier transformer, but rectifier transformer capacity is not increased compared with a single deicer. This paper firstly presents the proposed topology and analyzes its advantages. Then, the rectifier transformer design is introduced, and the SVG control strategy is presented. Simulation results for the proposed device are presented, and an engineering devices with a capacity of 21.8 MVA developed for the 220 kV Fuchong substation is described. The simulation and application results indicate that the proposed devices work well. [ABSTRACT FROM AUTHOR]

This paper presents application guidelines for a new generic plant controller model that can be used for renewable plant dynamic system analysis that may include the control of static compensators (STATCOMs), static var compensators (SVCs), and/or energy storage devices. The authors originally presented the need for such a model to the Western Electricity Coordinating Council (WECC) and contributed to various stages of the new model development led by WECC. As Independent System Operators (ISOs)/Regional Reliability Organizations (RTOs)/Transmission Service Providers (TSPs) are moving toward acceptance and use of generic models only the authors have for the first time applied this new model for an operating renewable plant. The new model was configured, parameterized, and tuned to control two STATCOMs and multiple switched capacitors/reactors to represent a master/auxiliary control strategy as implemented in the plant. Dynamic simulations show that the configured and parameterized model is performing properly as expected. This tuned model was submitted to the system operator for compliance with the interconnection requirements of the plant. This is the first submission of the new generic model for this type of control for a renewable project. The submitted model is appropriate for dynamic simulations, which are routinely performed by ISOs/RTOs/TSPs in system impact studies or transmission planning studies. This paper provides useful guidelines in applying this new model for similar projects. [ABSTRACT FROM AUTHOR]

An improved switching scheme for static VAr compensators (SVCs) that have fixed capacitor-thyristor-controlled reactors (FC-TCRs) for load balancing and power factor improvement has been addressed in this paper. The proposed control scheme can eliminate negative-sequence current caused by unbalanced load while improving the source power factor simultaneously. Thus total current supplied by the source can be minimized along with improvement of the load voltage profile. As the switching of TCR can introduce additional harmonics in the line, an optimized switching function is adopted in the proposed scheme for minimum injected harmonics without using an external filter. The gravitational search algorithm has been used for obtaining the optimized switching angle. The proposed scheme has been verified through proper simulations backed by suitable experimental results on a practical system. [ABSTRACT FROM PUBLISHER]

This paper presents a fault detection and classification scheme for a shunt [static var compensator (SVC)] compensated line. The proposed relaying scheme is based on the concept of superimposed sequence components-based integrated impedance (SSCII). For an internal fault, the magnitude of SSCII is small and for an external fault, it is very large. In the SVC compensated line, a fault forces SVC to vary its impedance. Superimposed components are injected due to this impedance variation, along with the fault components. These SVC-injected components are treated as fault-injected components and, therefore, even the sound phases are detected as faulty phases. To avoid such failure, fault-injected superimposed components have been extracted by using the modified prefault data, which is estimated according to SVC impedance variations. The superimposed components measured using the modified prefault data consist of fault-injected superimposed components only. The proposed scheme has been tested for all types of faults, different values of fault resistances, and several fault locations and SVC locations. The results demonstrate that the proposed scheme successfully detects and classifies the faults. Also, the proposed scheme is robust against variations in fault resistance, source impedance, and SVC location. [ABSTRACT FROM AUTHOR]

To solve problems of catenary icing, this paper presents an online antiicing technique using the Joule effect on the catenary of the high-speed electric railway. According to its scheme, a couple of static var generators (SVGs) are, respectively, placed at the traction power substation and sectioning post to automatically generate an adjusted current, varying with the change of temperature, wind speed, and traction load, which will be obtained by online monitoring. The online antiicing current is not only determined by the developed heat balance equation for the contact wire, but also the developed relationship of the distributed current on catenary and the voltage of the traction network. The simulation and experimental results on an autotransformer (AT) traction power-supply system illustrate that the temperature of the contact wire can be maintained above 0 ^\circC with the antiicing current and the voltage of traction network also in the normal range. [ABSTRACT FROM AUTHOR]

In electrical arc furnaces (EAFs), an unstable arc leads to unfavorable operation of the EAF, which can be rectified by using series reactors. Installation of the series inductor affects some electrical parameters of the EAF, such as arc stability, power factor, arc length, and the EAF efficiency. Furthermore, it reduces the effective transferred power to the EAF. To achieve desired transferred power after installation of the series reactors, the secondary voltage of the EAF transformer should be increased. However, after any tap changing of the EAF transformer, arc stability and other relevant parameters are affected. So the impact on the EAF electrical magnitudes caused by changes in the series reactor and in the EAF transformer tap should be simultaneously studied. This research deals with a new method for optimal setting of the series reactor and EAF transformer tap to achieve the EAF best performance. Using a nonlinear model for the EAF, its electrical characteristics, at nominal transformer current and for all of the possible transformer and reactor taps, are calculated and the results are tabulated. Using these tables, the optimal setpoint for transformer and series reactor taps is determined in different conditions. Finally, the method is investigated from an economic point of view. [ABSTRACT FROM AUTHOR]

Developed synthetic test circuits for thyristor valves of flexible ac transmission systems (FACTS) are established in this paper. By controlling the thyristor valves of synthetic test circuits, it can reproduce test stresses, including, but not limited to, the forward high voltage before the thyristor valve withstanding overcurrent and reverse recovery voltage after thyristor valves withstanding overcurrent, on thyristor valves in FACTS equipment equal to or greater than those that appear in commercial projects. With corresponding test circuits and control strategies, the temperature-rise test, overcurrent test, and the synthetic test for thyristor valves can be performed, respectively. Then, a protection method of synthetic test circuits is presented. Finally, a temperature-rise test platform, overcurrent test platform, and synthetic test platform for thyristor valves have been set up, respectively. The test results show that the developed circuit and proposed control and protect strategies are available to test for thyristor valves used in FACTS. [ABSTRACT FROM PUBLISHER]

A robust coordination approach for the controller design of multiple high-voltage direct-current (HVDC) and flexible ac transmission systems (FACTS) wide-area controls (WACs) is presented in this paper and has the aim of stabilizing multiple interarea oscillation modes in large-scale power systems. The suitable wide-area control signals, which are given to HVDC and FACTS wide-area controllers, respectively, are chosen from a large number of candidate items. Then, a sequential robust design approach is planned for the wide-area controller coordination of HVDC and FACTS devices. This approach is based on the robust control theory and is formulated as a standard problem of multiobjective mixed H2/H\infty output-feedback control with regional pole placement constraints. The linear matrix inequality (LMI) theory is applied to solve such a robust control problem. A case study on the 16-machine 5-area system, which is modified with one HVDC interconnected transmission, one shunt-FACTS device (SVC), and one series-FACTS device (TCSC), is performed to validate the robust performance in terms of multiple oscillations damping under various operating conditions. [ABSTRACT FROM AUTHOR]

Static var compensator (SVC) devices have been extensively utilized in modern substations to achieve high flexibility and wide tolerance to load variation. However, due to frequent switching of the thyristors in a static var compensator, large amounts of electromagnetic interference (EMI) are being generated, which may cause malfunction of the SVC or unaccepted response of victim devices positioned nearby. In this paper, an advanced acquisition system was established to implement onsite measurements in order to obtain the EMI data. A digital calibration technique for the antenna was applied to trace back the actual electromagnetic emissions. The radiated and conducted EMI data are comparatively analyzed to present detailed and useful information of the EMI levels. According to the configuration of an SVC and the dynamic performance of the random load, an equivalent model was established to simulate and predict the conducted EMI levels. Based on onsite measurements as well as theoretical analysis, pertinent immunity measures were put forward to reduce coupling impacts on the electronic units of the secondary side. [ABSTRACT FROM PUBLISHER]

Timely and accurate data with high resolutions holds great promise for more responsible and advanced power grid operations. The research has been focusing on design of monitoring and control scheme given the assumptions that the supporting information and communication technology (ICT) systems are capable of providing data and perform control with sufficient quality. A relatively less addressed aspect is the dependency of wide-area monitoring and control (WAMC) systems on their supporting ICT architecture which is usually a compromise between various concerns, such as data quality, interoperability, or security. Without an appropriate ICT architecture design, the projected WAMC system functionalities run the risk of being jeopardized. This paper begins with a presentation about possible delays brought by complex data-transfer and processing processes. Analytical experiments are conducted with purposes to quantify the maximum delay and input signal's sensitivity toward delay on a typical WAMC application where the control of static var compensation (SVC) is coordinated with generator excitations using phasor measurements. Given the characteristics of this particular control scheme, two possible ICT architectures that provide data with different qualities are compared concerning the reliability of this WAMC application. This paper concludes by proposing a generic ICT architecture, enabling efficient WAMC systems implementation in terms of data quality. [ABSTRACT FROM AUTHOR]

This paper presents an approach to optimally select and allocate flexible ac transmission (FACTS) devices in a distribution network in order to minimize the number of voltage sags at network buses. The method proposed is based on the optimization of a preselected objective function using simple and niching genetic algorithms (GA). The objective of the optimization is to achieve the improvement in overall system sag performance of the network. Using proposed GA-based optimization, the location, the type and the rating of six (in total) FACTS devices are optimized simultaneously. Three types of FACTS devices are implemented in this study, namely, static var compensator, static compensator, and dynamic voltage restorer. The performance of the proposed algorithm is tested and illustrated on 295-bus generic distribution system. [ABSTRACT FROM PUBLISHER]

Flexible ac transmission system (FACTS) devices or their subderivative custom power devices are efficient and often used and recommended power-electronics-based devices for mitigation of voltage sags in electrical power system. With FACTS devices installed, the overall system (and individual bus) sag performance could significantly change depending on the type of the device used. In order to assess this change in sag performance in realistic large power systems, the classical (essentially static) fault calculation procedure should be amended to incorporate the effects of these devices on bus voltages. This paper presents a new approach of quasistatic sag analysis using a system impedance (Z bus ) matrix that incorporates FACTS devices. Three types of FACTS devices which are most often used in practical applications are considered in this study: static compensator, static var compensator, and the dynamic voltage restorer. The case studies based on the 295-bus generic distribution system are used to illustrate the modeling method and the effectiveness of these devices in sag mitigation. [ABSTRACT FROM PUBLISHER]

This paper presents the first individual channel analysis and design (ICAD) of a high-order synchronous generator and a static VAr compensator (SVC) featuring a damping control loop. Particular emphasis is given to the closed-loop performance and robustness assessments. Fundamental analyses are carried out using ICAD and its frequency-domain approach to explain the dynamic behavior of the generator affected by an SVC with damping capabilities. A coordinated SVC voltage and damping control is achieved in a straightforward fashion owing to the transparent manner in which ICAD treats the complex interactions taking place between the synchronous generator and the SVC with a damping control loop. Using the ICAD framework, an indepth comparison is made between the competing abilities to provide system damping of the SVC and the power system stabilizer. [ABSTRACT FROM PUBLISHER]

Electrical distribution system suffers from various problems, such as reactive power burden, unbalanced loading, voltage regulation, and harmonic distortion. Though DSTATCOMS are ideal solutions for these systems, they can be costly and have complexity compared to other reactive power compensation solutions. Phasewise-balanced reactive power compensations are required for fast-changing loads needing dynamic power factor correcting devices leading to terminal voltage stabilization. Static var compensators (SVCs) are preferred for these loads due to low cost and simple control strategy. These SVCs, while correcting power factor, inherently create harmonics due to the nonsinusoidal currents caused by the operation of thyristor-controlled reactors. This paper proposes minimizing the harmonics injected into the distribution systems with the operation of TSC-TCR-type SVC used in conjunction with fast-changing loads at the LV distribution level. The fuzzy logic system and ANNare used to solve this nonlinear problem, giving optimum triggering delay angles used to trigger thyristors in TCR. The scheme is attractive and can be used at SVC installations in distribution systems for steady-state reactive power compensation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present an analytical, state-space model of an indirect, voltage-controlled cascaded-type multilevel static synchronous compensator (STATCOM) with "square wave control." The multilevel converter model is segmented into a dynamic and static part in order to accurately represent all internal feedback connections. Each voltage component is analyzed in detail and described mathematically by an averaged expression with an equivalent capacitance. The STATCOM model is linearized and linked with a DQ frame ac system model and the controller model, and implemented in MATLAB. The controller gains are selected by analyzing the root locus of the analytical model to give optimum responses. The validity and accuracy of the proposed model are verified against non-linear digital simulation PSCAD/EMTDC in the time and frequency domain. The model is very accurate in the subsynchronous range, and it is adequate for most control design applications and practical stability issues below 100 Hz. Furthermore, the developed model can be used for multilevel cascaded converters which exchange real power. [ABSTRACT FROM AUTHOR]

In this paper, an analytical framework for minimizing losses and harmonics is presented for the cascaded-type-based multilevel static synchronous compensator (STATCOM) with "square-wave control." The focus lays on low losses, low-voltage total harmonic distortion (THD), and low dc voltage ripple. All of the system parameters are studied, including buffer reactance, dc capacitance, transformer ratio, and transformer leakage inductance. The equivalent capacitance concept is used to represent the complex structure of the multilevel converter. It enables studies of the internal STATCOM resonances which have a significant influence on triplen harmonics and losses. The interactions between system parameter are investigated and analytical formulae for optimal parameters are derived. Detailed PSCAD digital simulations are used to confirm the analytical formulae. The summarized design steps are offered that are recommended to obtain optimum STATCOM system parameters. [ABSTRACT FROM AUTHOR]

This work presents the development of analytical models for thyristor-controlled reactors (TCRs). A nonlinear model for the TCR was developed based on the use of Generalized Switching Functions and from this model, a detailed linear model was derived. The linear model allows for the analysis and precise understanding of the behavior of the TCR under small disturbances both in the time and frequency domains, for frequency ranges up to some tens of hertz. This model clearly shows that the TCR dynamics are operating point dependent. System parameter variations are also correctly considered in the model. With the proposed model, it is possible to design static var compensators (SVC) controllers in an integrated form, avoiding risks of instabilities and guaranteeing a good overall dynamic performance for the system. Validation of the models was done by comparing simulated results obtained with the proposed model with those obtained with a traditional electromagnetic transients program (EMTP). [ABSTRACT FROM AUTHOR]

Digital simulation of power systems containing power electronics apparatus is challenging due to the need to account multiple switching events within one simulation time-step. This paper describes a family of algorithms, with varying levels of computational complexity, for accounting such switching events in digital simulations. The proposed algorithms are applicable for both off-line and real-time simulations. A comparative study on their performance such as harmonic content, errors in fundamental component and simulation time requirement is presented. A Pulse Width Modulated (PWM) Voltage Source Converter (VSC) based D-STATCOM system is used as a case study for simulations. Simulation results indicate excellent performance (accuracy and efficiency) in comparison with a fixed time-step algorithm using a small step-size. [ABSTRACT FROM PUBLISHER]

The method of selective harmonic elimination is often used as an efficient means for obtaining harmonic-reduced waveforms from voltage sourced converters (VSC). However, the switching angles required for its implementation are usually pre-calculated on the basis of a fixed dc bus voltage. In practice, there are harmonics present in the dc source because of the finite dc bus capacitance and other realistic operating conditions, which can potentially introduce additional noncharacteristic harmonics. This paper examines the harmonic performance of a VSC-based static synchronous compensator as a function of design and operating parameters. These include the value of dc capacitor, the strength of the connected ac network and ac system unbalance. The results are generated using theoretical analysis for special cases and numerical simulation using electromagnetic transients simulation for the more general case. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel method for the mitigation of the voltage sag and voltage flicker by using Kalman filter and its derivatives (adaptive, and extended). The Kalman filter is used as a tool to extract both the instantaneous envelope of the voltage sags, and to extract the Instantaneous Flicker Level (IFL) of the voltage flicker. Also, this paper demonstrates the advantages of using the Kalman filter instead of the existing tools for tracking and extracting voltage disturbances. Digital simulation results are presented to illustrate the mitigation of unbalanced voltage sags, and the compensation of the cyclic and noncyclic voltage flicker by employing the proposed algorithm. [ABSTRACT FROM PUBLISHER]

STATCOM is a FACTS controller that is used in power systems to regulate the line voltage, enhance the power transmission capacity and extend the transient stability margin. STATCOM is conventionally realized by a voltage-source converter; however, being a current injection device, its performance can be improved when realized by a current-source converter (CSC) that can generate a controllable current directly at its output terminals. In this paper, a STATCOM based on the current-source converter topology is proposed. The nonlinear model of the current-source converter, which is the source of the difficulties in the controller design, has been modified to a linear model through a novel modeling technique. The proposed modeling technique is not based on the linearization of a set of nonlinear equations around an operating point. Instead, the power balance equation and a nonlinear input transformation are used to derive a linear model independent of the operating point. This model acts as the basis for the design of a decoupled state-feedback controller. The proposed STATCOM has been simulated using the PSCAD/EMTDC package. The simulation results show that a CSC-based STATCOM can result in excellent current and voltage waveforms as well as very short response time while operating at a low switching frequency. This makes the proposed scheme suitable for high power applications. [ABSTRACT FROM PUBLISHER]