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Static VAr compensators (SVCs) are the fastest and most widely applied FACTS devices at present. However, the SVC's high speed control can only be applied effectively if the type and size of the power components as well as the control and protection schemes are well matched to the specific network configuration and operation requirements. The combination of intensive computer and advanced real-time simulation is of great benefit for the design verification of new FACTS application. This paper presents the use of an RTDS simulator for the real-time testing of an SVC controller. It is a pure digital simulator for the SVC project and special measures have been taken to improve the precision of firing angle for TCRs. Some results of a SVC project study are presented.

The thyristor controlled series compensator (TCSC), composed of a capacitor in parallel with a thyristor controlled reactor (TCR), is a variant topology circuit. For such circuits there is no universal method to build the analytical mathematical model. The paper focuses on building an analytical model by the method of "topology" to describe the dynamic behavior of TCSC. Based on the model, the steady-state model is derived and the dynamic characteristics are discussed. The model is verified by digital simulation and the method can be extended to similar devices and be used for optimizing the control systems.

The first thyristor controlled series compensation (TCSC) project in China is expected to be applied to the Yimin-Fengtun 500 kV transmission line in the Year 2000 to improve its transmission capability. As a part of the project's feasibility study, this paper focuses on the steady-state and dynamic characteristics of TCSC based on digital simulations and physical experiments. It is necessary to comprehend the characteristics of TCSC devices for modeling TCSC correctly and proposing an effective transient control strategy. The paper studies the following several characteristics of TCSC: the steady-state characteristics in four typical operation modes; the operation symmetry under various control modes; the differences between closed-loop and open-loop impedance control; and the influences of different synchronizing signals on dynamic characteristics of impedance variations.

Thyristor controlled series compensation (TCSC) is expected to provide various benefits to power systems, including transient stability improvement, subsynchronous resonance (SSR) mitigation, power swings damping, fault current reduction, etc. Grasping the characteristics of TCSC installations and ending effective firing control strategies are essential to implement these advantages. This paper studies two important aspects of TCSC characteristics, the time constant of TCSC dynamic response and impacts of reference signals for thyristor firing angles on TCSC dynamic response. Closed-loop impedance control is proposed to speed the dynamic response of TCSC. A "two-stage" firing control method is presented to accomplish smooth switching between the capacitive region and inductive region. Both digital simulations with EMTDC/PSCAD software and physical experiments are employed in the study.

A desirable transient stability control scheme should be able to ensure the first-swing stability as well as provide effective damping. This paper presents a T-S model based fuzzy control scheme for thyristor controlled series compensation (TCSC) in power system transients. The nonlinear power system containing a TCSC is modelled as a fuzzy "blending" of a set of locally linearized models. A linear optimal control is designed for each local linear model. Different control requirements at different stages during power system transients can be considered in deriving the linear control rules. The resulting fuzzy controller is then a fuzzy "blending" of these linear controllers. Furthermore, a gradient descent algorithm is put forward to modify the rule truth factors for optimization. For convenient industrial realization of the fuzzy control scheme, a practical approach requiring only local signals is also described. Simulation with NETOMAC software has verified the effectiveness of the fuzzy control scheme.