Variable Series Capacitor Research Articles

Reduction of Reactive Power Compensation Efforts for Fusion Magnet Power Supplies Using Variable Series Capacitors

Reduction of Reactive Power Compensation Efforts for Fusion Magnet Power Supplies Using Variable Series Capacitors

Design Study on High-Frequency Magnets for Magnetic Hyperthermia Applications

The objective of this paper is to evaluate the engineering feasibility of high-frequency magnet systems for the magnetic hyperthermia cancer therapy. For the effective induction heating properties of the magnetic particles with a short-time cancer therapy, the target specifications of the magnet system are 0.06 T of the peak magnetic field with 200 kHz of the operating frequency and with 300 s (5 minutes) of the continuous or intermittent operation time. From the results, the magnet designed using 200-A copper Litz wires and a magnetic core enables the reduction of one turn voltage of the coil windings to 8.47 kV. The winding loss is 3.89 kW, which suggests that the magnet can be operated without a water cooling system. Single voltage source high-frequency inverter using commercially available SiC-MOSFET ( $ 1.2 kV) can drive the magnet with balancer circuits using variable series capacitors.

Low‐loss compact MEMS phase shifter for phased array antennas

A compact and low-loss MEMS-based phase shifter is proposed for microwave/millimetre-wave phased array antenna systems. The proposed phase shifter is an alumina-based CPW line, loaded with a variable series capacitor. The phase shifter uses an electromagnetic MEMS actuator to change the capacitor value. A simple three-mask surface micromachining process has been developed for device fabrication. The measurements at 26 GHz show a phase shift of 20°. The overall size of the phase shifter (including the actuator) is 0.5 × 1.5 mm. The measured average insertion loss is 0.75 dB with a variation of 0.4 dB for different phase shifts across the band from 24.5 to 26.5 GHz.

Compact Metamaterial-Based Tunable Phase Shifter at 2.4 GHz

A compact metamaterial (MTM)-based tunable phase shifter consisting of four unit cells with a simple DC bias circuit has been designed at 2.4 GHz. The variable series capacitors and shunt inductors that are required to be loaded periodically onto a host transmission line are realized employing only chip variable capacitors (varactors). In addition, the proposed phase shifter requires only one DC bias source to control the varactors, with the matching condition of the MTM line automatically satisfied. The measured phase shifting range is 285.2° (from —74.2° to 211°). The measured insertion loss is approximately 1.5 dB. The circuit/electromagnetic-simulated and measured results are in good agreement.

Controlling chaos and bifurcations of SMIB power system experiencing SSR phenomenon using SSSC

This paper presents the effect of Static Synchronous Series Compensation (SSSC) on the bifurcations of heavily loaded Single Machine Infinite Bus (SMIB) power system experiencing Subsynchronous Resonance (SSR). In SSR phenomenon, the series compensation increases the power transfer capability of the transmission line. However, Hopf bifurcation is depicted at certain compensation levels. The system then routes to chaos via torus breakdown scenario in case of conventional compensation (variable series capacitor) scheme. In this study, the effect of replacing the conventional compensation with SSSC is highlighted. Varying the SSSC controller reference voltage changes the compensation degree. The results show that the operating point of the system never loses stability at any realistic compensation degree in case of SSSC which means that all bifurcations of the system have been eliminated. Time domain simulations coincide with the results of the bifurcation analysis. The robustness of the SSSC compensation scheme and its controller is verified by subjecting a single-phase to ground fault at the end of the transmission line. The results are compared with the case of conventional compensation. Additionally, the effect of the SSSC controller gain on the location of the Hopf bifurcation is addressed.

Feasibility Study on Current Source Power Conversion for Superconducting Magnets Using Series Compensated Thyristor Converters

Thyristor converters are used as power conditioning systems for superconducting coils. The objective of this work is to discuss the series compensation of thyristor converters using variable series capacitors. Traditional thyristor converters operate with lagging power factor requiring large reactive compensation efforts. Similarly, the series capacitor can control the coil voltage through a unity power factor thyristor converter with a resulting leading power factor seen from the grid. Therefore, by combining the two, both leading and lagging reactive power control, and also the active power control of the superconducting coils can be achieved. In order to demonstrate the feasibility of the series compensation of the thyristor converter, a prototype converter using a gate-commuted series capacitor (GCSC) is developed. From the experimental results using a superconducting coil, the authors demonstrated the leading current control capability of the series compensated thyristor converter, and verified the leading, lagging, and unity power factor control capability based on thyristor converter systems. This feature leads to a potential reduction in reactive power compensation need of 50 percent of the conventional thyristor converter system.

Controlling SSR of the IEEE Second Benchmark Model Using TCSC and SSSC: a Comparativestudy

This paper investigates the effect of using two types of flexible alternating current transmission system (FACTS) devices on sub-synchronous resonance (SSR) phenomenon in power system. The devises are thyristor controlled series capacitor (TCSC) and static synchronous series compensator (SSSC .)The system under study, which is the first system of the IEEE second benchmark model of SSR, is modified such that the conventional variable series capacitor is replaced by TCSC and SSSC. The effects of TCSC and SSSC controllers are studied in terms of stability and damping. The stability of the operating point of TCSC- and SSSC-compensated systems is analysed using eigenvalue analysis of the linearized model. Time domain simulations based on the nonlinear model have also been carried out. It is found that both TCSC and SSSC have increased the operating point stability regions.

On the Effect of TCSC and TCSC-Controller Gain on Bifurcations of Subsynchronous Resonance in Power Systems

The effect of thyristor-controlled series capacitor (TCSC) and its controller gain on bifurcations of subsynchronous resonance (SSR) in power system are studied. Single machine infinite bus (SMIB) power system is considered for the numerical investigations. The series compensation of the transmission line is done by either conventional variable series capacitor or TCSC . The effect of the dynamics of the damper windings is investigated. The results show that in all cases, the operating point of the system loses stability via Hopf bifurcation. Hopf bifurcation comes either in subcritical or supercritical type. Supercritical Hopf bifurcation is depicted when the dynamics of the damper windings are neglected and the line is compensated by conventional series capacitor. With the same compensation scheme i.e., conventional series capacitor, supercritical Hopf bifurcation is addressed when the dynamics of the damper windings are included. On the other hand, subcritical Hopf bifurcation is predicted when the compensation is carried out by TCSC for both cases of including and neglecting the dynamics of the damper windings. In case of supercritical Hopf bifurcation, the system routes to chaos via torus breakdown. Additionally, it is found that when the compensation is done by TCSC, the stable operating point region is enlarged. Moreover, the stable operating point region increases when the damper windings are neglected. The effect of the TCSC controller gain on the locations of the Hopf bifurcation has also been studied.

03/02312 Improvement of multi-machine power system stability with variable series capacitor using on-line learning neural networl: Senjyu, T. International Journal of Electrical Power & Energy Systems 2003, 25, (5), 403–409

03/02312 Improvement of multi-machine power system stability with variable series capacitor using on-line learning neural networl: Senjyu, T. International Journal of Electrical Power & Energy Systems 2003, 25, (5), 403–409

Improvement of multi-machine power system stability with variable series capacitor using on-line learning neural network

This paper presents an adaptive control technique for the variable series capacitor using a recurrent neural network (RNN). Since, the parameters of the controller are determined by Genetic Algorithm (GA), which is one of the optimization algorithms, they are optimum only for that operating point and it is not possible to obtain good control performance against variations in the operating and fault point. The adaptive controller proposed in this paper consists of an optimum controller using GA and an RNN. As the RNN was on-line training, robust control performance can be achieved for various operating conditions. The effectiveness of this control method is demonstrated by considering simulation of a multi-machine power system.

オンライン学習型NNを用いた可変直列コンデンサによる電力系統の安定化制御法

オンライン学習型NNを用いた可変直列コンデンサによる電力系統の安定化制御法

Transient stability enhancement using self adjusting-flexible variable series capacitor compensation

The paper presents a novel flexible, self-adjusting variable series capacitor compensation(VSrC) scheme to enhance transient stability of an interconnected AC system. The scheme is regulated by an error-driven, error-scaled non-linear transigmoid controller.

ファジー適応制御器を用いた可変直列コンデンサによる電力系統の安定化制御法

ファジー適応制御器を用いた可変直列コンデンサによる電力系統の安定化制御法

Optimal flexible AC transmission systems (FACTS) devices allocation

This paper presents the development of mathematical model representations of variable series capacitors and static phase shifters which are also known as Flexible AC Transmission Systems (FACTS) in power system economic dispatch. The objective of this research is to find the optimal locations of FACTS devices for improved economic dispatch. The proposed approach is based on the decomposition-coordination method and the network compensation technique. Taking advantage of accumulated experience in power system optimization and the existence of the Optimal Power Flow (OPF) software, the software development cost for implementing the proposed algorithm is reduced. In this paper, digital simulation studies on small power systems under different network parameters, with and without FACTS devices, were conducted. The purpose of the simulation studies was to assess the effectiveness of the proposed algorithm in minimizing the operating cost and enhancing the system performance. The results of the simulation studies and the proposed algorithm will be presented and discussed in detail in this paper.

Subsynchronous resonance performance tests of the Slatt thyristor-controlled series capacitor

A thyristor-controlled series capacitor (TCSC) has been designed, installed, and field tested on the Bonneville Power Administration 500 kV transmission system. The Slatt TCSC is a variable series capacitor with high control bandwidth. Field test results demonstrate that this TCSC does not participate in or contribute to subsynchronous resonance (SSR). It is SSR neutral in itself, and it can reduce SSR effects due to other nearby conventional series capacitors.

ファジィ制御を適用した可変直列コンデンサによる電力系統の安定化制御

電力系統は, 大規模化・複雑化が進行しており、そのような状況で電力を需要家に安定供給するためには電力系統の安定度向上が重要な課題である.近年, 交流系統の安定度向上策としてFACTS(Flexible AC Transmission System)構想が提唱され注目を集めている.本論文では, ファジィ制御器によりFACTS機器の一つである可変直列コンデンサ(Variable Series Capacitor : VSrC)を制御し, 電力系統を安定化する一手法を提案している.本制御の特徴は, これまで電力系統のファジィ制御で考慮されていなかった安定性をスライディングモード導入により考慮できるため、ファジィ制御規則を系統的に構成できることである。電力系統を正確にモデル化することは一般に困難であるが、本制御法のようにシステムのあいまいさを取り扱えるファジィ制御は電力系統制御に有益である。本制御法の有効性は, 一機無限大母線系統ならびに三機六母線電力系統で構成された多機電力系統を対象としたシミュレーションにより検証している。本制御を用いれば、系統中の発電機の回転子角速度の振動が短時間で抑制できることを示している。

Stabilization of inter‐area and/or oscillatory modes in large‐scale power system by voltage impedance power system (VIPS) apparatus based on decentralized control scheme

AbstractNew technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high‐speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors.This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter‐area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large‐scale power system based on a Lyapunov function.Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large‐scale power system.

Design and application of a fuzzy logic control scheme for transient stability enhancement in power systems

A fuzzy logic controller is designed to implement variable series capacitor compensation in the transmission network of interconnected power systems. This compensation scheme is one of the most widely accepted as a solution to limitations created by overstretched generation and transmission systems. This is one facet of flexible AC transmission systems (FACTS) employed to enhance the stability of the system. The effectiveness of the fuzzy logic controller to properly control such a variable series capacitor under different types of system disturbance is demonstrated through simulation studies on a single-machine infinite-bus system. The results of these simulation studies show that the controller can contribute tremendously to the enhancement of power system transient stability during such disturbances. Considerable increase in power throughput and significant improvement in the damping of the electromechanical oscillations are achieved by implementing this device in the transmission system.

A method for identification of effective locations of variable impedance apparatus on enhancement of steady-state stability in large scale power systems

Variable impedance apparatus such as a static VAr compensator (SVC) and a variable series capacitor (VSC) can improve the steady-state stability of a power system if they are located appropriately. The present paper proposes an index for identifying the location of SVC and VSC in large scale power systems for effective damping. The index is called LIED (location index for effective damping) by the authors. Since LIED can be computed quickly for large scale power systems which have more than two hundred generators without conducting a number of digital simulations and eigenvalue analyses, it is valuable for the system planner who needs to identify the effective location of SVC and VSC. The proposed index is applied to the New England test system and its validity is demonstrated through digital simulations. >

A bilinear self-tuning controller for multimachine transient stability

Bilinear time-series model-based self-tuning control is proposed for a multimachine power system, controlled by a single variable series capacitor. When the faults of concern are large and DC-stabilizing, it is proposed that nonlinear model-based controllers can enhance the region of stability of the power system, and return the states to their stable equilibrium. A simple predictive nonlinear self-tuning controller using local measurements of relative rotor angles is examined. It is shown to perform well in stabilizing different faults on a 45-bus, 17-generator low order model with the dynamic characteristics of the Western System Coordinating Council (WSCC) system. >