Static Synchronous Compensator Controller Research Articles

Stability Enhancement of a Multimachine System Using STATCOM with Supplementary Controller

This paper investigates the improvement in the stability of a multi-machine power system using Static Synchronous Compensator (STATCOM). A systematic procedure for modelling, simulation and optimal tuning of the parameters of a STATCOM controller for stability enhancement is presented. The design of the proposed supplementary controller is formulated as an optimization problem, and adopts the particle swarm optimisation (PSO) algorithm for the optimal tuning of the controller parameters. The performance of the proposed controller is tested in a multimachine power system and results are compared with and without controller. Simulation results under different operating conditions are presented to highlight the effectiveness of the proposed controller

A Review of Static Synchronous Compensators (STATCOM)

This paper reviews the development of static synchronous compensator (STATCOM), and analylizes the structure of its main circuit, its working principles and control strategies. At last, this paper comes to a conclusion of technical characteristics of STATCOM and outlook of its development trends. Fast acting STATCOM, a representative of FACTS family, is a promising technology which is extensively used as state-of-the-art dynamic shunt compensator for reactive power control in transmission and distribution system. STATCOM controller employs various solid-state converter topologies, magnetics configurations, control algorithms, and switching techniques and so on. The development of STATCOM controller has been well reported in literature with its versatile application in power system. Thus deep investigation of STATCOM from the perspective of its intelligent control and the configuration of STATCOM’s main circuit is valuable.

Design of Multicarrier Pulse Width Modulation based Cascaded Multilevel Inverter for STATCOM using Bats Echolocation Controller

A Static Synchronous Compensator (STATCOM) is one of the Flexible AC Transmission System (FACTS) device which plays an vital role in power system network in alleviation of small and large transient disturbances and better voltage regulation. This paper proposed a self tuning Proportional-Integral (PI) controller for STATCOM which provided a voltage support at point of common coupling (PCC). Self tuning of PI controller was achieved by adapting PI controller gains with system parameters by using Bats Echolocation controller which mimics the Bats Echolocation behavior. In the proposed controller, the system voltage (parameter) at point of common coupling compared with reference voltage and then Bats Echolocation Controller updates the PI controller gains according to the variation obtained between them. This paper also proposed a Cascaded Multilevel Inverter (CMLI) instead of conventional Voltage Source Inverter (VSI) for STATCOM to obtain better voltage regulation at point of common coupling. The voltage imbalance between H-bridge cells in CMLI was rectified by prosing Multicarrier Pulse Width Modulation (PWM) techniques, The proposed controller was validated by comparing the simulation results with fixed gain PI controller and Self tuning PI controller using Neural controller and Particle Swarm Optimization.

Improved low-voltage-ride-through capability of fixed-speed wind turbines using decentralised control of STATCOM with energy storage system

The design and implementation of a new control scheme for reactive power compensation, voltage regulation and transient stability enhancement for wind turbines equipped with fixed-speed induction generators (IGs) in large interconnected power systems is presented in this study. The low-voltage-ride-through (LVRT) capability is provided by extending the range of the operation of the controlled system to include typical post-fault conditions. A systematic procedure is proposed to design decentralised multi-variable controllers for large interconnected power systems using the linear quadratic (LQ) output-feedback control design method and the controller design procedure is formulated as an optimisation problem involving rank-constrained linear matrix inequality (LMI). In this study, it is shown that a static synchronous compensator (STATCOM) with energy storage system (ESS), controlled via robust control technique, is an effective device for improving the LVRT capability of fixed-speed wind turbines.

Harmony search algorithm for STATCOM controllers tuning in a multi machine environment

This paper presents the application of static synchronous compensator (STATCOM) to voltage support in a multimachine electric power system. Harmony Search (HS) Algorithm as a meta-heuristic optimization method is considered for tuning the parameters of STATCOM. In order to evaluate the performance of STATCOM in voltage support, a multi-machine electric power system installed with STATCOM is considered as case study. The system under study is IEEE 14 bus standard system testing. The results are compared with the system without STATCOM. Several nonlinear time-domain simulation tests visibly show the ability of STATCOM in voltage support.

Harmony Search Algorithm for STATCOM Controllers Tuning in a Multi Machine Environment

This paper presents the application of static synchronous compensator (STATCOM) to voltage support in a multimachine electric power system. Harmony Search (HS) Algorithm as a meta-heuristic optimization method is considered for tuning the parameters of STATCOM. In order to evaluate the performance of STATCOM in voltage support, a multi-machine electric power system installed with STATCOM is considered as case study. The system under study is IEEE 14 bus standard system testing. The results are compared with the system without STATCOM. Several nonlinear time-domain simulation tests visibly show the ability of STATCOM in voltage support.

Analysis of integrated STATCOM-SMES based on three-phase three-level multi-pulse voltage source inverter for high power utility applications

This paper is aimed to investigate the operating characteristics of a static synchronous compensator (STATCOM) integrated with superconducting magnetic energy storage (SMES) for high power applications in the transmission network level. The STATCOM controller topology comprises multi-level multi-pulse neutral-point clamped-type (NPC) voltage source inverters (VSIs) using the harmonics cancellation technique, and incorporates a SMES coil. An innovative two-quadrant multi-level dc–dc converter is proposed to effectively interface the STATCOM with the superconducting coil using a buck-boost topology with neutral point voltage control capabilities; thus enabling to simultaneously control both active and reactive power exchange with the high voltage power system. A detailed analysis of major system variables is presented, including analytical results and digital simulations using the MATLAB/Simulink environment. Moreover, a three-level control scheme is designed, including a full decoupled current control strategy in the d– q reference frame with a novel controller to prevent the STATCOM dc bus capacitors voltage drift/imbalance and an enhanced power system frequency controller.

Design of Robust Current Controller for Two-Level 12-Pulse VSC-based STATCOM

The static synchronous compensator (STATCOM) is a shunt connected voltage source converter (VSC) based FACTS controller using GTOs employed for reactive power control. A typical application of a STATCOM is for voltage regulation at the midpoint of a long transmission line for the enhancement of power transfer capability and/or reactive power control at the load centre. The PI controller-based reactive current controller can cause oscillatory instability in inductive mode of operation of STATCOM and can be overcome by the nonlinear feedback controller. The transient response of the STATCOM depends on the controller parameters selected. This paper presents a systematic method for controller parameter optimization based on genetic algorithm (GA). The performance of the designed controller is evaluated by transient simulation. It is observed that the STATCOM with optimized controller parameters shows excellent transient response for the step change in the reactive current reference. While the eigenvalue analysis and controller design are based on D-Q model, the transient simulation is based on both D-Q and 3-phase models of STATCOM (which considers switching action of VSC).

Nonlinear Control Design of Shunt Flexible AC Transmission System Devices for Damping Power System Oscillation

Problem statement: The disturbance in the complicated network of power system may cause in nonlinear response. Static Synchronous Compensator (STATCOM) is a power electronic based device that has the capability of controlling the line current. This study applies the STATCOM to decrease the over line current in power system during dynamic state. Approach: This study proposes the control strategy of a STATCOM to enlarge the stability region of a simple power system. The control is determined very carefully to satisfy the Lyapunov’s stability criterion and is found to be a non-linear function of system states. The proposed nonlinear control of STATCOM for damping power system oscillation is investigated through the sample system. Results: The maximum generator rotor angle of the faulted system without a STATCOM is continuously oscillation and the maximum value is much more than the system with a STATCOM. Conclusion: STATCOM based the proposed nonlinear control can damp power system oscillation.

Robust STATCOM control for the stabilisation of fixed-speed wind turbines during low voltages

This paper presents a robust voltage control scheme for fixed-speed wind generators using a static synchronous compensator (STATCOM) controller. To enable a linear and robust control framework with structured uncertainty, the overall system is represented by a linear part plus a nonlinear part that covers an operating range of interest required to ensure stability during severe low voltages. The proposed methodology is flexible and readily applicable to larger wind farms of different configurations. The performance of the control strategy is demonstrated on a two area test system. Large disturbance simulations demonstrate that the proposed controller enhances voltage stability as well as transient stability of induction generators during low voltage ride through (LVRT) transients and thus enhances the LVRT capability.

The Design of STATCOM Control System

The main characteristic of a multilevel inverter is able to reduce each power device voltage stress. Static Synchronous Compensator (STATCOM) is the major application of the inverter to compensate reactive power in power system. The proposed strategy is simple, high precision, fast response speed, while it has less fluctuation with the impact of load parameters, and good robust characteristics. STATCOM employing the multilevel inverter provides good performance such as enlarging capacity and decreasing even frequency harmonics, and the control of alternation working switch order based PWM can be applied in related research fields.

Control of static synchronous compensator with supplementary damping enhancement for wind farm voltage regulation

This study presents a new control design approach for the wind farm voltage regulation using static synchronous compensator (STATCOM). A mode decoupling proportional plus integral (PI) controller, in which the control gains are synthesised by eigenstructure assignment (EA), is proposed for the STATCOM. EA is a state-space approach, which is used to improve system damping by eigenvalue assignment and alter system mode shape by eigenvector assignment. To embed the physical PI control loops in the state-space model, an equivalent transformation is proposed to map the feedback gain matrix to the PI controller. Owing to the presence of the physical PI control loops, the control signals would not mire into saturation when appropriate limiter according to the STATCOM capacity is placed in the control variables. To further alleviate the undesired oscillation mode excited by transient disturbance, a lead-lag-based supplementary damping controller (SDC) is adopted. Simulation comparisons are provided to show that the proposed technique can be an effective method for mitigating the voltage fluctuation in the wind farm because of the load changes and the wind gust.

STATCOM Controller Design Based on MLP for Power Flow Control

The static synchronous compensator (STATCOM) is one of the developed converter-based flexible AC transmission systems (FACTS) controllers, recently. The STATCOM is shunts with power system and can absorb/deliver reactive power from/to power systems. In this paper, to power flow control in power system by STATCOM, a controller based on neural networks (NNs) have been designed; i.e. multilayer perceptron (MLP). The designed controller has been compared with two conventional controllers; i.e. PI and PID controllers. Influence of each controller on injected active power, injected reactive power and injected current by STATCOM have been analyzed. Three control parameters have used as decision criteria; i.e. peak time, fall time, peak value, fall value and site time. Simulations are performed in MATLAB/SIMULINK environment. compared with PID controller. In (6), STATCOM damping controller has been designed using the phase compensation technique to eliminate its negative influence to improvement of power system oscillations. Authors of reference (7) proposed a STATCOM controller with a fixed modulation index during the transient period and presented harmonic analysis of STATCOM based on Bessel functions. The proposed controller by the pole assignment method was used to regulate AC system bus voltage. The step load change was used to illustrate proposed controller. Wang, in (8), has reported negative interactions between STATCOM AC and DC control and then has proposed multiple control functions of the STATCOM. The designed single multivariable PI controller has used as a MIMO control system.

A New Fuzzy-neural STATCOM Controller for Transient Stability Improvement in

In this paper a neuro-fuzzy controller is proposed to enhance transient stability and increase critical clearing time (CCT) in the static synchronous compensator (STATCOM). For achieving this idea, first the controller is designed based on the Lyapunov energy function. In order to avoid complexity of computation and overcome system uncertainty a neuro-fuzzy controller is proposed. In this controller, neural network determines the system rules and membership functions. In order to design a neural network and its training patterns, the energy function controller is used under various system conditions. This controller has learning abilities due to its robust fuzzy controller and neural network. Simulation results on the single-machine infinite-bus (SMIB) show that the neuro-fuzzy controller damps electromechanical oscillations and increases the critical clearing time.

STATCOM-Based Indirect Torque Control of Induction Machines During Voltage Recovery After Grid Faults

This paper proposes a control method for limiting the torque of grid-connected cage induction machines during the recovery process after grid faults, by using a static synchronous compensator (STATCOM) connected at the machine terminals. When a STATCOM is used for transient stability improvement, common practice is to design the control system to keep reactive current at maximum level until the voltage has returned to its initial value. This will result in high torques during the recovery process after grid faults. The control method proposed in this paper is intended to limit such torque transients by temporarily defining a new voltage reference for the STATCOM control system. As torque is controlled through the voltage reference of the STATCOM, the method is labeled indirect torque control (ITC). The presented concept is a model-based approach derived from a quasi-static equivalent circuit of the induction machine, the STATCOM and a The?venin representation of the power system. For illustration and verification, time-domain simulations of a wind power generation system with a STATCOM at the terminals of an induction generator, are provided. As the objective of limiting the torque of the induction machine is achieved, the derivation of the concept proves to be reasonable. The approach is presented in its most general form, oriented to torque limitation of induction machines both in generating and motoring mode, and is not restricted to the presented example.

Decentralized robust static synchronous compensator control for wind farms to augment dynamic transfer capability

This paper presents an algorithm to design a decentralized robust controller for static synchronous compensators (STATCOMs) using minimax linear quadratic output-feedback control design approach. There is an increase in the available (dynamic) transfer capability of power systems with fixed-speed wind generators due to the designed decentralized controllers. The effects of the integration of various types of wind generators into power systems based on transfer limit have also been analyzed in this paper. The effectiveness of the suggested control strategy is validated by simulations on a benchmark two area power system. The performance of the designed controller is also compared to a conventional proportional-integral-based STATCOM controller. Simulation results show that both the dynamic voltage stability and the transient stability can be improved by using the robust STATCOM control proposed in this paper.

Robust state feedback controller design of STATCOM using chaotic optimization algorithm

In this paper, a new design technique for the design of robust state feedback controller for static synchronous compensator (STATCOM) using Chaotic Optimization Algorithm (COA) is presented. The design is formulated as an optimization problem which is solved by the COA. Since chaotic planning enjoys reliability, ergodicity and stochastic feature, the proposed technique presents chaos mapping using Lozi map chaotic sequences which increases its convergence rate. To ensure the robustness of the proposed damping controller, the design process takes into account a wide range of operating conditions and system configurations. The simulation results reveal that the proposed controller has an excellent capability in damping power system low frequency oscillations and enhances greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions shows that the phase based controller is superior compare to the magnitude based controller.

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.

Modeling, control and simulation of a chain link STATCOM in EMTP-RV

This paper describes an alternative STATic synchronous COMpensator (STATCOM), by connecting a number of gate turn off (GTO) thyristor converters in series on the ac side of the system. Each GTO converter forms one ‘link’ of a 1-phase, full-bridge voltage–source-converter (VSC) and is referred to as a ‘Chain Link Converter’ (CLC). Each GTO of a chain link STATCOM (CLS), is switched ‘ON/OFF’ only once per cycle of the fundamental frequency by using a sinusoidal pulse width modulation (SPWM) technique. Approximate models of a 3-phase CLS using dq-transformation are derived to design two controllers for controlling reactive current and ac voltage to stabilize the system voltage at the point of common coupling (PCC). A novel technique, called the rotated gate signal pattern (RGSP), is used for balancing the voltages of the link dc capacitors. The performance investigation of the CLS system when used in a radial line is carried out under steady- and transient-state operating conditions by means of the simulation package; EMTP-RV and the results are presented.

STATCOM Impact Study on the Integration of a Large Wind Farm into a Weak Loop Power System

Recently, renewable wind energy is enjoying a rapid growth globally to become an important green electricity source to replace polluting and exhausting fossil fuel. However, with wind being an uncontrollable resource and the nature of distributed wind induction generators, integrating a large-scale wind-farm into a power system poses challenges, particularly in a weak power system. In the paper, the impact of static synchronous compensator (STATCOM) to facilitate the integration of a large wind farm (WF) into a weak power system is studied. First, an actual weak power system with two nearby large WFs is introduced. Based on the field SCADA data analysis, the power quality issues are highlighted and a centralized STATCOM is proposed to solve them, particularly the short-term (seconds to minutes) voltage fluctuations. Second, a model of the system, WF, and STATCOM for steady state and dynamic impact study is presented, and the model is validated by comparing with the actual field data. Using simulated PV and QV curves, voltage control and stability issues are analyzed, and the size and location of STATCOM are assessed. Finally, a STATCOM control strategy for voltage fluctuation suppression is presented and dynamic simulations verify the performance of proposed STATCOM and its control strategy.