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.

Static synchronous compensators (STATCOM): a review

A simple and novel approach in the design of an extended Kalman filter (EKF) for the measurement of power system frequency has been presented in this paper. The design principles and the validity of the model have been outlined. The performance of this filter has been compared with some of the existing methods for estimating the frequency of a signal under noisy conditions. The feasibility of the proposed filter has been tested in the laboratory under worst-case measurement and network conditions, which might occur in a typical power system. Also, the proof of the stability for the proposed filter has been discussed for a single sinusoid. It has been found that the proposed algorithm is suitable for real-time applications especially when the frequency changes are abrupt and the signal is corrupted with noise and other disturbances due to harmonics.

A novel Kalman filter for frequency estimation of distorted signals in power systems

The hysteresis loop of the core material in a test current transformer is simulated using the Jiles-Atherton theory. Comparisons are made between recorded and simulated waveforms and it is found necessary to replace the modified Langevin function used by Jiles and Atherton. Using an alternative function described in the paper, good agreement is achieved between test and simulated waveforms.

A current transformer model based on the Jiles-Atherton theory of ferromagnetic hysteresis

One of the weakest components of modern transient simulation software is the transformer model. Many opportunities exist to improve the simulation of its complicated behaviors, which include magnetic saturation of the core, frequency-dependency, capacitive coupling, and topologically correctness of core and coil structure. This paper presents a review of transformer models for simulation of low- and mid-frequency transients. Salient points of key references are presented and discussed in order to give an accessible overview of development, implementation and limitations of the most useful models proposed to date. Techniques for representation of the most important behaviors are examined, with the intent of providing the needed foundation for continued development and improvement of transformer models.

Transformer modeling for low- and mid-frequency transients - a review

This paper reviews a number of mathematical models used to represent the nonlinear behavior of the magnetic core of in- strument transformers. Models of instrument transformers using these core representations are presented. The transient response of the instrument transformer is compared to actual test results recorded in the laboratory. The paper provides practical guidelines as to which of the physical elements of instrument transformers are important to model during transient studies and which elements could be ignored without sacrificing the accuracy of the simulation results. The electromagnetic transients program (EMTP) data files used to generate the models are also provided in the appendix to help new EMTP users model instrument transformers for evalua- tion of high-speed protective relaying systems.

Mathematical Models for Current, Voltage, and Coupling Capacitor Voltage Transformers Working Group C-5 of the Systems Protection Subcommittee of the IEEE Power System Relaying Committee,

Improved models for current transformers (CT), potential transformers, and capacitive voltage transformers (CVT) for a relay software library are presented. The magnetizing characteristic in each of these transformers is based on the nonlinear power curve formulation of J.R. Lucas (1988). The flux-current loops of the transformer core are self-generated rather than predetermined or based on look-up tables. The results presented show that the models developed for the transformers behave as expected, and agree with reported field investigations. Models for the CT and CVT give acceptable results, including those under remanent conditions and ferroresonant conditions. These models are thus necessary components for relay studies carried out with electromagnetic transient programs whether offline or in real time. >

Improved simulation models for current and voltage transformers in relay studies

The paper describes a technique to control the harmonic output of a static synchronous compensator (STATCOM) using a pulse width modulation (PWM) scheme with a minimal number of additional switchings. A neural network algorithm is developed to define the switching instants. This technique offers an alternative to the multi-pulse techniques that require complex magnetic circuit arrangements as well as to the conventional PWM technology that requires a large number of switchings.

A neural network controlled optimal pulse-width modulated STATCOM

This paper describes the development of a mathematical model of an air gapped current transformer. Air gapped current transformers are widely used in generator protection since these have the capability to overcome some of the problems encountered when using conventional current transformers. The model developed here is validated by comparing simulation results with recorded waveforms from a manufacturer's synthetic test plant.

Simulation model of an air gapped current transformer

This paper describes the development of a mathematical model of three current transformers which are connected in a delta configuration as part of a differential protection scheme. The delta connected configuration is typically found in transformer differential protection schemes for star-delta transformers. This model can be used in real time algorithms for testing of relays and can also be used to study differential protection schemes off-line. The accuracy of the model is validated by comparing the simulations with waveforms recorded at a synthetic test plant.

P.G. McLaren

Papers

A current transformer model based on the Jiles-Atherton theory of ferromagnetic hysteresis

Improved simulation models for current and voltage transformers in relay studies

A neural network controlled optimal pulse-width modulated STATCOM

Simulation model of an air gapped current transformer

Simulation of delta connected current transformers in a differential protection scheme