Advanced Static VAr Compensator Research Articles

State feedback control of advanced static var compensator using a five-level NPC inverter topology

This paper deals with the modeling and control of an advanced static var compensator (ASVC) using a five-level neutral point-clamped (NPC) voltage source inverter (VSI). The nonlinear state space model of the five-level ASVC is obtained from the d-q axis frame. The effectiveness of this compensator highly depends on the choice of the control strategy. The proposed state feedback control (SFC) technique is applied to adjust the ASVC Var flow with the AC transmission network and achieve DC voltage capacitor balance. The dynamic performance of the ASVC based SFC controller is evaluated under several operating conditions. The simulation results demonstrate that the proposed SFC control strategy is highly robust compared to the conventional Proportional-Integral (PI) control.

Design and experimental analysis of an advanced static VAR compensator with computer aided control

This study presents integration of a real-time energy monitoring and control system with an advanced reactive power compensation unit based on fixed capacitor-thyristor controlled reactor (FC-TCR). Firing angles of the thyristors located in the FC-TCR are controlled by a microcontroller in order to keep the power factor within the limits. Electrical parameters of the system are measured by specially designed circuits and simultaneously transferred to the computer via a data acquisition board. Thus, real time data of the system can be observed through a visual user interface. The data obtained is not only analyzed for control process, but also regularly saved into a database. The system has been tested in laboratory conditions under different load characteristics and experimental results verified that the system successfully and accurately achieves compensation process against the all operational conditions.

Voltage Swell Mitigation Using Flexible AC Transmission Systems Based on Evolutionary Computing Methods

The main subject of these paper deals with enhancing the steady-state and dynamics performance of the power grids by using new idea namely Advanced Flexible AC Transmission Systems based on Evolutionary Computing Methods. Control of the electric power system can be achieved by using the new trends as Particle Swarm Optimization applied to this subject to enhance the characteristics of controller performance. This paper studies and analyzes Advanced Flexible AC Transmission System to mitigate only one of power quality problems is voltage swell. The Advanced Flexible AC Transmission System, which will be used in this paper, is the most promising one, which known as Advanced Thyristor Controlled Series Reactors, and Advanced Static VAR Compensator were utilized in this research to mitigate the voltage swell aiming to reach. This paper focuses on the operation of the AFACTS device under turning off heavy load that may causes transformer damaged, as no research covers this problem by this technique. Particle Swarm Optimization is used to determine the value of series inductor connected to the Advanced Flexible AC Transmission System. The proposed algorithm formatting, deriving, coding and programming the network equations required to link AFACTS during steady-state and dynamic behaviors to the power systems tested on the IEEE 30 bus system as well as IEEE 14 bus system, and 9 bus system.

A Multi-Variable LQG Controller-based Robust Control Strategy Applied to an Advanced Static VAR Compensator

In this paper, an Advanced Static VAR Compensator (ASVC) based on a voltage type inverter is presented and analysed. The ASVC, which uses the Pulse Width Modulation (PWM) technique, will be modelled in the Park system. Moreover, a low pass filter is introduced at the output of the inverter in order to eliminate the high order harmonics. The proposed system may compensate inductive or capacitive reactive power. The mathematical model thus obtained will be used for the design of a linear quadratic Gaussian (LQG) multivariable (MIMO: Multiple Input Multiple Output) control strategy. The simulation results obtained with MATLAB software are included and will be thoroughly discussed in this paper.

An advanced static var compensator based on a three level IGBT inverter modelling analysis and active power filtering

This paper presents the dynamic performance analysis of an Advanced Static Var Compensator (ASVC) using three-level neutral point-clamped voltage source inverter. The paper presents the principles of operating and the method of reference currents generation. The dynamic behaviour of the system is further analysed using Matlab/Simulink with SimPower Systems toolbox through a set of simulation tests. The results obtained have been applied to an active power filter which might lead to the design of a robust controller for current harmonics and reactive power applications

Effect of Advanced Static VAR Compensator on Control of Power System Load Shedding

This paper investigates the effect of Static VAR Compensator (SVC) on power system load shedding. SVC is mainly used in power system stability improvement. This paper proposes a new use of SVC to reduce load shedding. An algorithm of Newton Raphson method (NR) to reduce the load shedding for installing SVC in the system is proposed in this paper. 5 bus test system example is used to demonstrate the effect on load shedding. The test results show that the effect of SVC is significant, in this Static VAR compensator (SVC) is incorporated in Newton Raphson method in which Power Flow Solution is a solution of the network under steady state conditions subjected to certain constraints under which the system operates. The power flow solution gives the nodal voltages and phase angles given a set of power injections at buses and specified voltages at a few, the model of SVC i.e. SVC Susceptance model is discussed. It is also shown that the power system losses are decreased after incorporating the SVC in this N-R method. The results are generated for 5-Bus system. By incorporating the SVC the amount of load shedding is reduced to get the voltages in their limits.

Static synchronous compensators (STATCOM): a review

Fast acting static synchronous compensator (STATCOM), a representative of FACTS family, is a promising technology being extensively used as the state-of-the-art dynamic shunt compensator for reactive power control in transmission and distribution system. Over the last couple of decades, researchers and engineers have made path-breaking research on this technology and by virtue of which, many STATCOM controllers based on the self-commutating solid-state voltage-source converter (VSC) have been developed and commercially put in operation to control system dynamics under stressed conditions. Because of its many attributes, STATCOM has emerged as a qualitatively superior controller relative to the line commutating static VAR compensator (SVC). This controller is called with different terminologies as STATic COMpensator advanced static VAR compensator, advanced static VAR generator or static VAR generator, STATic CONdenser, synchronous solid-state VAR compensator, VSC-based SVC or self-commutated SVC or static synchronous compensator (SSC or S2C). The development of STATCOM controller employing various solid-state converter topologies, magnetics configurations, control algorithms, switching techniques and so on, has been well reported in literature with its versatile applications in power system. A review on the state-of-the-art STATCOM technology and further research potential are presented classifying more than 300 research publications.

Evaluation of UPFC and ASVC applied to nonlinear load model

PurposeUnified power flow controller (UPFC) and advanced static VAR compensator (ASVC) devices are now recognized as the most important flexible AC transmission systems (FACTS) devices. This paper aims to focus on this.Design/methodology/approachThe effects of the location of such installation FACTS devices are examined.FindingsThe UPFC as a voltage regulator and ASVC devices applied to a non‐linear load are modeled and analyzed. It was found that the optimum installation position for a UPFC device is at the sending end bus where wide range of receiver terminal line voltage and active power can be controlled. However, it was also found that the optimum installation position for an ASVC device is at the receiving end bus where a wide range of receiver terminal line voltage and active power can be controlled. In both cases, it was found that a wider range of reactive power could be controlled when the devices are installed closer to the receiving end bus.Originality/valueShows that the mid‐point of a transmission line is the optimal location for some FACTS devices or reactive power support. The proof is based on a fixed receiving end voltage magnitude, which is practically not valid.

Optimal location of advanced static VAR compensator (ASVC) applied to non-linear load model

The advanced static VAR compensator (ASVC) device is now recognized as one of the most important Flexible Alternating Current Transmission Systems (FACTS) devices. It has been proven that the mid-point of a transmission line is the optimal location for some FACTS devices or reactive power support, and the proof is based on the linear load, which is not valid practically. The validity of the optimal location of Pulse Width Modulation (PWM) based ASVC device is investigated when the non-linear load model is considered. In this paper, the ASVC applied to a non-linear load is modeled and analyzed. It was found that the optimum installation position for this device is at the sending end bus, where the wide range of receiver terminal line voltage and active power can be controlled. It was found that a wider range of reactive power could be controlled when the device is installed close to the receiving end bus.

Custom Power Devices: An Interaction Study

This paper presents a simulation study about the coordination and interaction of advanced power electronic devices working in close electrical proximity. In particular, three major power quality devices (PQDs)-an advanced static VAR compensator, a dynamic voltage restorer, and a high-speed transfer switch as well as their combined performance-are modeled and studied in detail using ATP-EMTP. The paper addresses potential problems related to the PQD's combined operation, in addition to coordination issues. Comparison between simulation results and field measurements of individual PQD's are also presented.

STATCOM controller design for power system stabilization with sub-optimal control and strip pole assignment

This paper solves the problem of power system stabilization by using the advanced static VAR compensator (STATCOM) to increase the damping of the electromechanical and exciter modes of the power system. The dynamic oscillations are repressed by the proposed STATCOM controller, which is designed using a two-level optimization output feedback control and the strip poles assignment method. The linear quadratic regulator method does not require pre-specified weighting matrices. The two output feedback control schemes, designed using the direct and minimum error excitation methods, respectively, are compared. To show the effectiveness of the dynamic oscillation suppression, eigenvalue analysis and nonlinear simulation were used to demonstrate that the proposed STATCOM controller significantly improves the dynamic performance of the power system.

Robust synchronous voltage sources designed controller for power system oscillation damping

The advanced static Var compensator (ASVC), also known as STATCON, has a superior inherent characteristic to the SVC in providing voltage support and in damping power system oscillations. However, it is known that the ASVC system for damping control may suffer from unstable zeroes or a pair of complex zeroes on the imaginary axis, and also parameter uncertainty which can degrade the control performance. To cope with these problems, this paper proposes an improved robust H ∞-ASVC controller for increasing the robustness as well as the dynamic performance of the power system, where the bilinear transform is combined with the standard H ∞-approach. Uncertainties in a system model, such as modeling errors coming from a model reduction, linearization, change in operating conditions are successfully taken into consideration at the design stage of controller. The time delay uncertainty in the input signal of the controller is effectively treated. It is demonstrated that the new control system increases the performance and robustness of a power system under a wide range of operating conditions.

Advanced SVC models for Newton-Raphson load flow and Newton optimal power flow studies

Advanced load flow models for the static VAr compensator (SVC) are presented in this paper. The models are incorporated into existing load flow (LF) and optimal power flow (OPF) Newton algorithms. Unlike SVC models available in open literature the new models depart from the generator representation of the SVC and are based instead on the variable shunt susceptance concept. In particular, a SVC model which uses the firing angle as the state variable provides key information for cases when the load flow solution is used to initialize other power system applications, e.g., harmonic analysis. The SVC state variables are combined with the nodal voltage magnitudes and angles of the network in a single frame-of-reference for a unified, iterative solution through Newton methods. Both algorithms, the LF and the OPF exhibit very strong convergence characteristics, regardless of network size and the number of controllable devices. Results are presented which demonstrate the prowess of the new SVC models.

Suitable configuration of ASVC for power transmission application

In this paper, a study of suitable configuration of advanced static var compensator (ASVC) for power transmission application has been carried out. The suitability of an ASVC configuration is primarily judged from the harmonic generation point of view. The possibility of employing different switching scheme, like pulse width modulation (PWM) switching technique in ASVC for reduction in harmonic generation has also been investigated. All of the studies have been carried out through detail digital dynamic simulation using the PSCAD/EMTDC software.

Experimental investigation of voltage sag mitigation by an advanced static VAr compensator

A laboratory model of an advanced static VAr compensator (ASVC) was constructed to examine its capability for voltage sag mitigation. In this paper, the main structure of the laboratory ASVC is described briefly. Its mitigation effect on voltage sags of different magnitude is then demonstrated. The influences of its initial operation point, system impedance, and DC capacitance are considered. The behaviour of this laboratory ASVC during a phase-angle jump associated with a voltage sag is examined.

Mathematical models of a three-level advanced static VAr compensator

Two mathematical models of an advanced static VAr compensator (ASVC) are described. One model was obtained using time-domain analysis of the ASVC circuit and then developed into an s-domain model which was used to study the compensator's control system. Both models were validated using a three phase, 4 kVAr hardware model of a three-level ASVC. The time-domain model was also validated using computer simulations carried out with the EMTDC program. Two switching strategies were considered in the study: fundamental frequency modulation (FFM) and selective harmonic elimination modulation (SHEM). The time domain model was used to predict the waveforms at various parts of the ASVC circuit, for both switching strategies.

Dynamic performance of a STATCON at an HVDC inverter feeding a very weak AC system

This paper investigates the dynamic performance of the advanced static VAr compensator or STATCON at a high voltage direct current (HVDC) converter terminal where the AC system has a very low short circuit ratio (SCR). The STATCON is based on a nine-level GTO thyristor inverter. The studies include operating characteristics of the STATCON under various AC and DC disturbances. The simulation results are compared with other types of reactive power compensation options available for such applications. It is shown that the STATCON has clear advantages over the other compensators, in areas such as: fault response time; voltage support ability; and DC recovery, while operating with very weak AC systems.

A three-level advanced static VAr compensator

An advanced static VAr compensator (ASVC) employing a three-level inverter has been investigated for three-phase applications. The paper describes the operating principles of the ASVC using an elementary single phase ASVC circuit. The construction of a hardware model of the three-phase, three-level ASVC is then presented. The performance of the ASVC is obtained from an experimental study carried out on this laboratory model. The use of the selective harmonic elimination modulation (SHEM) technique to minimize harmonics is explored. Experimental studies have been carried out to determine the speed of response of the scheme by controlling it in a closed loop.

Transient analysis of an advanced static var compensator using quad‐series voltage‐source PAM inverters

AbstractThis paper deals with an advanced static Var compensator (ASVC) using quad‐series voltage‐source PAM inverters. The ASVC consists of four three‐phase voltage‐source inverters with a common dc capacitor and four three‐phase transformers, each primary winding of which is connected in series with each other. Each inverter outputs a square‐wave voltage, while the synthesized output voltage of the ASVC has a 24‐step wave shape. This results not only in a great reduction of harmonic currents and dc voltage ripples but also in fewer switching and snubbing losses.In this paper, transient analysis is performed with the focus on the response of reactive power and the resonance between the dc capacitor and ac reactors. Experimental results obtained from a small‐rated laboratory model of 10 kVA are also shown to verify analytical results based on the p‐q transformation. The analytical results help in the design of system parameters such as the capacity of the dc capacitor and feedback gains.

Advanced static compensation using a multilevel GTO thyristor inverter

This paper investigates the possibility of using the multilevel gate turn-off (GTO) thyristor inverter as an advanced static VAr compensator (STATCON). The studies have indicated that the design shows promise and that the fundamental frequency switching of the GTO thyristors is superior to various forms of pulse-width modulation. The main advantages of the multilevel STATCON over other types of STATCON is that each individual GTO thyristor is clamped to a DC voltage and can be switched independently. Hence a staircase type of output voltage can be used to reduce the harmonics, the filtering requirements and the switching losses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>