Thyristor Switched Capacitor Research Articles

Voltage balancing using switched capacitors

Thyristor switched capacitors (TSCs) are a useful means of load balancing and reactive power support. The control of a general load by a binary weighted switched capacitor system is discussed in this paper along with a simple control scheme where the capacitor bank across a line pair is adjusted to control the fundamental voltage magnitude for that line pair. In a three-phase three-wire system, it is shown that an ideal reactive source can control positive sequence magnitude and cancel any negative phase sequence terms. With the quantized control levels available in a TSC, a ramping scheme with input hysteresis is shown to be effective in balancing in simulations and in a laboratory test with three banks in each phase. Low transient switching is employed with binary weighted capacitor banks to give a smooth variation of the reactive power supplied.

Detailed modeling of static VAr compensators using the electromagnetic transients program (EMTP)

A detailed model of static VAr compensators (SVC) has been developed for digital simulation of electrical transients. The model is applicable to SVC configurations employing thyristor-switched capacitors (TSCs) and thyristor-controlled reactors (TCRs). A modeling technique based on electromagnetic transients program (EMTP) data modularization is used to represent essential parts of the SVC main circuit and control system. To verify the model, an actual SVC is simulated with the EMTP and the results are compared with the transient-network-analyzer-type simulator using actual SVC controls.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A new power supply for superconductive magnetic energy storage system

A power supply for a superconductive magnetic energy storage system is presented. It permits fast independent regulation of the active and reactive power. The power supply was built with several units connected in parallel. Each unit consists of a 24-pulse bridge converter, thyristor-switched tap-changing transformer, and thyristor-switched capacitor bank. System operation was analyzed by computer simulation, and a feasible system realization is shown. A superconductive magnetic energy storage system with the proposed power supply has the capability of leveling the load variation, damping the low-frequency oscillation, and improving the transient stability in the power system. This power supply can be built with commercially available components using well-proven technologies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A static compensator model for use with electromagnetic transients simulation programs

A static VAr compensator (SVC) model based on state variable techniques is presented. This model is capable of being interfaced to a parent (or host) electromagnetic transients program, and, in particular a stable method of interfacing to the EMTDC program is described. The model is primarily that of a thyristor-controlled reactor. (TCR) and a thyristor-switched capacitor (TSC). Capacitor switchings within the TSC have been handled in a novel way to simplify storage and computation time requirements. During thyristor switching, the child SVC model is capable of using a smaller timestep than the one used by the parent electromagnetic transients program; after the switching, the SVC model is capable of reverting back to a (larger) timestep compatible with the one used by the parent program. Other features considered include the modeling of a phase-locked-loop-based, valve firing system. An application of this model to the simulation of a SVC controlling the AC voltage of the inverter bus of a back-to-back HVDC (high-voltage direct current) tie is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design and operational testing on thyristor modules for the SVC Kemps Creek

The design and operational testing of valves for the SVC (static Var compensator) to be installed at Kemps Creek substation in Australia are discussed. The most important design principles and features of the thyristor modules are given. Operational tests carried out on the thyristor modules are described; for this test program, noteworthy test circuits have been set up to perform both TSR (thyristor switched reactor) and TSC (thyristor switched capacitor) fault current tests with high test values and special waveforms. Test results and test circuits are presented. >

Optimal control of a static VAR compensator for minimization of line loss

Abstract A fast calculation method to calculate the firing angle of a thyristor-controlled reactor (TCR) and/or the number of thyristor-switched reactor (TSR) ‘switch-ons’ and/or the number of thyristor-switched capacitor (TSC) ‘switch-ons’ for four types of static VAR compensator (SVC) is proposed in this paper. The calculation is an optimal compensation problem that is written in terms of the minimization of power line loss by minimizing the line currents. The three-phase unbalanced line currents after installation of an optimal reactive power compensator will become three-phase balanced line currents. In this paper, theoretical derivations and the computation procedures are formulated. A numerical example for real-time simulation is discussed to demonstrate the performance of the proposed method and to support the application capability.

Power electronics in electric utilities: static VAR compensators

The author deals with dynamic VAR compensation of electric power systems, applying power electronics for reactive power generation and control. After an overview of the emergence and status of modern, solid-state VAR compensators in utility and industrial applications, it is shown how dynamic VAR compensation increased transmittable power by providing voltage support, transient stability improvement, and power oscillation damping in electric power transmission systems. Methods of reactive power generation and control using thyristor-controlled reactors, with fixed and thyristor-switched capacitors or modern gate-turn-off (GTO) power converters that can function without AC capacitors or reactors, are described. A summary is included of the control structure and operation to provide the desired characteristics and performance in power systems applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation of Static-Var System (SVS) Performance on a Transient Network Analyzer

A real-time hybrid static-var system model designed to aid in efficiently analyzing the performance of static, thyristor-controlled compensation schemes on a transient network analyzer is described. The types of studies required to develop a static-var system specification are outlined. Use of the real-time, hybrid model to evaluate different compensation schemes, including thyristor-controlled reactors and thyristor-switched capacitors, and to optimize control system characteristics based on the response to system disturbances is delineated. Results of transient network analyzer simulations for tra nsmission system application are presented in the form of plots of the controlled bus voltage, the controlled reactor currents, the error voltage calculated by the control system, and the control system output. A parametric anaylsis of the control system response for a particular system disturbance is also illustrated.

Simulation of Static-Var System (SVS) Performance on a Transient Network Analyzer

A real-time hybrid static-var system model designed to aid in efficiently analyzing the performance of static, thyristor-controlled compensation schemes on a transient network analyzer is described. The types of studies required to develop a static-var system specification are outlined. Use of the real-time, hybrid model to evaluate different compensation schemes, including thyristor-controlled reactors and thyristor-switched capacitors, and to optimize control system characteristics based on the response to system disturbances is delineated. Results of transient network analyzer simulations for tra nsmission system application are presented in the form of plots of the controlled bus voltage, the controlled reactor currents, the error voltage calculated by the control system, and the control system output. A parametric anaylsis of the control system response for a particular system disturbance is also illustrated.

Shunt-connected reactors and capacitors controlled by thyristors

Two basic schemes for thyristor-controlled static compensators are described, namely, thyristorswitched capacitors (TSC) and thyristor-controlled reactors (TCR). A more advanced scheme using a combination of TSC and TCR is presented. It is shown that this combination gives a greater degree of flexibility in the designing of a compensator. The paper also briefly describes the control system in a compensator comprising both thyristor.controlled reactors, thyristor-switched capacitors and reactors (TSR). One method to damp power oscillations, using TSC with a certain control strategy, is presented. The problem of unbalanced loads and load balancing methods using TSC and TCR aie discussed. It is shown that the combined system (TSC/TCR) generates very low harmonics, because the TSC does not generate any harmonics. Finally, some pictures from the first installations comprising both TSC and TCR are shown