Reactor Banks Research Articles

A novel method of overvoltage suppression due to de-energization of shunt reactor in high voltage system

<span lang="EN-US">Substations usually employ shunt reactors to reduce the reactive power of systems. Due to current chopping when the shunt reactor is shut off, a high frequency and amplitude overvoltage is generated. This study was aimed at eliminating switching-related overvoltages in shunt reactors so as to maintain the equipment, prevent insulation failure, and avoid reignition. Therefore, the circuit was modified according to the suggested mitigation strategy to verify that transient overvoltages are suppressed by the circuit breaker and shunt reactor. With a view to evaluate the existing chopping caused by the switching of reactor bank, the alternative transients program (ATP-Draw) model was used to simulate the transients resulting from switching a shunt reactor. This work has been put into practice for various current chopping values. The collected results of the simulation showed that the proposed model was significantly highlighted for the suppression of overvoltages, with the voltage across the circuit breaker being reduced from 679 KV to 478 KV at a current chopping value of 5 A and from 351 KV to 152 KV across the shunt reactor.</span>

Energy saving through load balancing of 3-wire loads

<span lang="EN-US">In this paper, static var compensators (SVCs) and many load compensation techniques are reviewed. A continuously and linearly controlled compensating susceptance is devised from a switched capacitor bank and a switched reactor bank. The switched capacitor bank is built of four binary weighted thyristor switched capacitors, while the switched reactor bank is built of three binary weighted thyristor switched reactors. Although few switched capacitors and reactor are used, their binary weighted values beside their control scheme make them respond as a continuously and linearly controlled reactive device in capacitive and inductive modes of operation. A load balancing system is constructed of three identical devised compensating susceptances connected in delta-form. It is designed for balancing an 11 kV 50 Hz distribution station. The proposed system is designed and tested on PSpice which is a computer program equivalent in performance to real hardware design. The simulation results of the proposed system have showed significant treatment of severe imbalance conditions.</span>

Solving the Optimal Reactive Power Dispatch Problem through a Python-DIgSILENT Interface

The Optimal Reactive Power Dispatch (ORPD) problem consists of finding the optimal settings of reactive power resources within a network, usually with the aim of minimizing active power losses. The ORPD is a nonlinear and nonconvex optimization problem that involves both discrete and continuous variables; the former include transformer tap positions and settings of reactor banks, while the latter include voltage magnitude settings in generation buses. In this paper, the ORPD problem is modeled as a mixed integer nonlinear programming problem and solved through two different metaheuristic techniques, namely the Mean Variance Mapping Optimization and the genetic algorithm. As a novelty, the solution of the ORPD problem is implemented through a Python-DIgSILENT interface that combines the strengths of both software. Several tests were performed on the IEEE 6-, 14-, and 39-bus test systems evidencing the applicability of the proposed approach. The results were contrasted with those previously reported in the specialized literature, matching, and in some cases improving, the reported solutions with lower computational times.

Performance up gradation of static VAR compensator with thyristor binary switched capacitor and reactor using model reference adaptive controller

There are various static var compensator configurations are available and listed in the literature. Their performances are evaluated based on their voltage support, dynamic response, losses, cost, and additional filter requirement, if any. In this paper, efforts are made to improve the dynamic performance parameter such as rise time, settling time, and peak overshoots. A new topology with an adaptive controller is presented, in which capacitor and reactor banks are divided in their binary values and connected in the shunt. Capacitor and reactor banks are operated by thyristorised switches. Both these banks are operated in closed-loop form as a cascade control. Amongst these, capacitor bank operates as coarse control, and reactor bank acts as fine control. For the performance enhancement, a model reference adaptive controller is used. The system identification toolbox is used to evaluate the mathematical model of the plant with Matlab. The model's performance was analyzed deeply by the adaptive controller with different reference models such as critical, under, and overdamped. The performance parameters such as rise time, settling time, and peak overshoot in the form of reactive power swings, are evaluated and plotted for different adaptive gains using MIT rules. Abbreviations: : Peak overshoot; : Reactive power of capacitor; : Reactive power of inductor; : Reactive power of TBSC bank; : Reactive power of TBSR bank; : Rise time; : Settling time; e: Error; Gc(s): Transfer function of TBSC plant; Gl(s): Transfer function of Disturbance plant; Gr(s): Transfer function of TBSR plant; SVC: Static VAR Compensator; t:time; TBSC: Thyristor binary switched capacitor; TBSR: Thyristor binary switched reactor; TSC: Thyristor switched capacitor; TSR: Thyristor switched reactor; u(t): System input; v(t): System disturbance; y(t): System output; Ym: Reference model output; Yp: Plant output; γ: Adaptive gain; θ: Theta

Performance enhancement of modified SVC as a thyristor binary switched capacitor and reactor banks by using different adaptive controllers

In this paper, a new topology with two shunts flexible AC transmission system (FACTs) devices, thyristor binary switched capacitors (TBSC), and thyristor binary switched reactors (TBSR) based SVC has been developed, which are working in parallel. Both TBSC and TBSR are designed, and simulation results are obtained for the dynamic loading condition. Switching of capacitor and reactor banks with thyristor as a switch is obtained at transient-free conditions so that the significant problem of switching harmonics is eliminated. The coarse control of reactive power is obtained by selecting switchable capacitor banks in binary mode. For fine control, the TBSR bank is designed with a total value equal to the lowest step value of the TBSC bank. It is discrete stepwise compensation at a period of one cycle, and this reactive power compensation is almost continuous as per requirement. It has near-to-zero switchings and zero steady-state harmonics. The mathematical model of TBSC + TBSR has been identified with the system identification toolbox. Different control strategies are implemented as PID controller, Model predictive control, and Model reference adaptive control. The proposed SVC topology performance is discussed based on the performance parameters such as rise time, settling time, and peak overshoot using adaptive controllers.

A novel adaptive single-phase reclosure scheme based on improved variational mode decomposition and energy entropy

The extended grading capacitor (GC) for multi-break circuit breaker is a cost-effective method to suppress secondary arc. Since the integration of GC alter the topology of the system, the existing adaptive auto-reclosure scheme should be changed. Considering the characteristics of line voltage waveforms under various faulty conditions, a novel adaptive single-phase reclosing scheme is proposed based on an improved variational mode decomposition (VMD) and energy entropy (EE). The voltage signal extracted from capacitive voltage transformer is decomposed into a series of finite bandwidth intrinsic mode functions (IMF), and then the energy entropy (EE) of each IMF component is computed. To avoid modal mixing, the concept of quality factor is raised. In the case of permanent fault, the natural component of the voltage attenuates fast due to the continuous discharge through the fault point. As time goes, such component approaches zero, and the total voltage becomes more smooth and regular. The EE value also decreases gradually. The EE value is considerably large for the transient fault due to the repetitive re-strike of electric arc, and the EE value has an oscillating trend. The fault type can be distinguished by setting a reasonable threshold. The performance of the proposed method is almost not affected by the installation mode of shunt reactor bank, the fault location, the shunt compensation degree, fault resistance, etc. Both the theoretical analysis and simulation results demonstrate that the proposed method can quickly and accurately identify the fault type.

Study and Simulation of Voltage Profile Recovery on a 200 km Transmission Line Using Shunt Static Var Compensator (SVC)

This article aims to clarify how Flexible Alternating Current Transmission Systems (FACTS) technology, for static operating devices, conditioned on application to long-distance transmission lines can solve problems related to voltage drop on paths known as “weak zones” of the power transmission system. Some technical aspects of the construction of the SVC Static Reactive Compensator in conjunction with thyristor switching devices such as TCR and TSC are described. The proposed scenario is similar to the Brazilian interconnected system, where much of the generator park is hundreds of miles from the country's major consumer centers, leading to the structure of this system longer transmission lines and consequently greater losses in the transmission paths. For the proposed simulations the MATLAB Simulink ® environment was used considering different voltage unbalance operating ranges caused by three-phase faults in the transmission lines. The conclusions show that the distance from the lines to the load has a great influence on the oscillatory effects of voltage, and the fact that the “loading” transmission lines can compensate for much of the path by generating wars through the circuit's natural capacitance. The allocation of capacitor and shunt reactor banks is a reliable option for the transmission system and can act as a support mechanism for voltage control maneuvers to circumvent abrupt changes in reactive demand. From the simulations output comparison, the transient effects showed greater stability in the voltage signal recovery in the stretches where the compensation blocks were located near the lowering substation bus, thus demonstrating the capacity of the applied technology.

Three‐phase thyristor controlled reactor using two sets of delta connected switches with low current harmonics

This work presents a three-phase thyristor-controlled reactor (TCR), which makes use of two constituent banks of controlled reactors, with coordinated control of the triggering angle of both the banks. The first reactor bank has a set of `delta' connected back-to-back thyristor switches with a balanced set of reactors in series with each switch, while the second reactor bank also has back-to-back thyristor switches in `delta' connection but with a balanced set of reactors in series with each line. It is demonstrated that this arrangement prevents some major current harmonics in the supply line by proper choice of the maximum kVAr ratio between the two reactor banks. The use of delta connected switches in both banks reduces the current rating of the switches. Hence, without using any phase-shifting isolation transformer or filters, the proposed technique permits control of reactive power over a reasonable range, with a low current total harmonic distortion meeting existing harmonics standards. Simple construction and operation of the proposed TCR make it an attractive and cheaper solution. The modelling, analysis and performance assessment of the new TCR are presented.

Harmonic Cancellation in a Three-Phase Thyristor Controlled Reactor Using Dual Banks

A three-phase three-wire thyristor controlled reactor (TCR) topology is presented comprising of two reactor banks, involving simultaneous firing angle control of both banks having maximum kVAr in the ratio of 60:40. The first reactor bank is “Δ” connected and has phase switching whereas the second reactor bank is either “Δ” or equivalent “Y” connected with line switching. Such an arrangement prevents the triplen harmonics from entering into the supply system and some major characteristic harmonics can also be eliminated from the TCR line current due to the selection of the ratings of the two reactor banks. Thus, without using any additional filters or phase shifting transformer, this scheme enables reactive power control with a low current total harmonic distortion (THD) over a reasonable range of control, meeting requisite harmonics standards. Simplicity in construction and operational requirements of the proposed topology makes it a viable and cost effective solution. Its modeling, analysis, and performance assessment are presented. Simulation and experimental results support the theoretical proposition.

Dual Delta Bank TCR for Harmonic Reduction in Three-Phase Static Var Controllers

The conventional “Delta” connected thyristor-controlled reactor (TCR) bank used for static var compensation and other applications is proposed to be split into two identical “Delta” banks each having kvar capacity half of the total TCR capacity. The study presented shows that such combination of two identical “Delta” connected reactor banks, one with phase switching by thyristors and the other with line switching thyristor arrangement can effectively reduce the harmonic generation of the TCR. Since both the three-phase banks are connected in delta, the zero sequence triplen harmonics generated due to phase control of thyristors remain trapped inside the delta, thus reducing the harmonic injection into the power system. Further, some other major characteristic harmonics are also minimized in the TCR line current. Thus, the proposed TCR yields a low current THD which meets the requisite harmonics standards and it can therefore be used as an economic solution for reactive power control over a reasonable range in high power grid without using any external harmonic filter or special phase shifting transformer. This paper describes in detail the modeling, analysis, and performance assessment of the proposed scheme. Simulation results are furnished to evaluate the output characteristics of the scheme under varying operating conditions. Finally, experimental results are presented, which proves the theoretical proposition.

A New Harmonic Reduced Three-Phase Thyristor-Controlled Reactor for Static VAr Compensators

A new thyristor-controlled reactor scheme is presented in this paper, in which the total bank is split into one Δ- and one Y-connected reactor bank with the addition of a low-rating zig-zag autotransformer, instead of the conventional scheme using a Δ-connected reactor bank with a harmonic current filter. This arrangement prevents the triplen harmonics generated by the Y bank from entering into the supply system and at the same time, the combination results in cancellation of some major characteristic harmonics from the source current. Thus, without using any additional filters or phase-shifting two-winding transformer, this scheme facilitates reactive power control over a wide range and also meets the requisite harmonics standards. The scheme is simple and provides a cost-effective solution to the VAr compensation problem. Simulation and experimental results are provided to validate the proposed concept.

Анализ электромагнитных процессов в устройстве компенсации реактивной мощности с переменной индуктивностью

Objective: To analyze transient processes when activating reactive power compensation unit with variable inductance and load bounce in electric traction alternating current network. To determine reactive power control range for possible structural variations of a unit. To choose the most power efficient variant of mutual connection of controlled reactor and capacitor bank with uncontrolled capacity in reactive power compensation unit. To make a conclusion, concerning feedback device application in control system. Methods: Connection diagrams of a unit to an alternating current monophase network. Mutual connection diagrams of controlled reactor and capacitor bank were chosen. Structural variations’ control range analysis of reactive power compensation unit was conducted. In MATLAB Simulink software package, simulation of different bucking out system circuitry was fulfilled. Simulation of compensation unit functioning was carried out for one variant with load bounce in electric traction. Results: It was established that, in case of series connection of controlled reactor and capacitor bank, control range may comprise no more than 15 % of nominal capacity. Starting current of a unit reaches twofold value. Parallel connection makes it possible to control reactive power in a broad band. Starting current in this case reaches fourfold excess of value. It is suggested to use uncontrolled reactor successively with capacitor bank as an additional unit. Such a variant makes it possible to reduce starting current and simultaneously provide filtration of the third current harmonics. Practical importance: A series-parallel variant of compensation unit circuitry seems to be the most perspective for application in electric traction alternating current network.

Hierarchical Two-Level Voltage Controller for Large Power Systems

This paper proposes a two-level voltage controller for large-scale power systems. The aim of the controller is to maintain a near-optimal voltage profile in the transmission network by coordinating discrete reactive power (var) control devices in the system. The controller is targeted for implementation in electric power transmission utility companies where most of the voltage controls are coordinated by switching of discrete var devices such as shunt capacitor and reactor banks and transformer banks load tap changers (LTCs). By effectively dividing the controller responsibilities between local substation controls and a central coordinator at control center level, the design is aimed at voltage control of large-scale power systems. At local level, the substation controllers maintain their respective substation bus voltages by local power-flow-like computations using mostly local PMU measurements. The central coordinator computes and provides the voltage set-points to the substation controllers and also coordinates by enabling or disabling the local controllers as needed. The controller is being designed towards prototype implementation in Southern California Edison (SCE), starting with local controllers at specific substations in the first stage. It is tested on real-time dynamic models and large-scale power-flow simulations of SCE transmission network.

Flujo Óptimo Reactivo para Minimización de Pérdidas: una Nueva Propuesta de Función de Adaptación y Manejo de Restricciones

This work presents a fitness function and constraint handling approach applied to the problem of optimal reactive power dispatch. This problem aims at the reduction of power losses by deciding on voltage setpoints of generators, transformers taps and switchable capacitor and reactor banks. The fitness function consist of a product of sub-functions that represent permissible limits on system variables and that also includes a specific goal on power loss reduction. The main advantage of the proposed fitness function is the fact that the global optimum of the problem is known beforehand. A genetic algorithm was used to solve the ORPD with both fitness functions. This fitness function was implemented and compared with a traditional fitness function by means of a genetic algorithm for three study IEEE cases: 57, 118 and 300 bus systems. It was found that the proposed fitness function showed better performance than the traditional one, guaranteeing the system operation within the feasible region.

Transient recovery voltages of circuit breakers in UHV transmission system

Circuit breakers are an important element in a substation, which is used for coupling of busbars, transformers, transmission lines, switching of shunt reactors, capacitor banks etc. The most important task of a circuit breaker is to interrupt fault currents and thereby protect various power system components. This task requires operation of the circuit breaker under different making and breaking conditions such as - faults in the vicinity of the circuit breaker, short-line faults, out-of-phase closing/ opening, switching of - capacitor /shunt reactor banks, no-load transformers/lines etc. During opening operation, after the arc extinction, the insulating medium between the breaker contacts has to withstand the rapidly increasing recovery voltage. This recovery voltage has a transient component (transient recovery voltage, TRV) caused by the system when current is interrupted. The TRV of the Circuit Breaker is a decisive parameter that limits the interrupting capability of the Circuit Breaker. The TRV to be adopted for system voltages of 1200 kV, towards which our country is migrating, needs to be estimated by transient studies as they cannot be extrapolated from lower voltage systems. This paper deals with the modeling and study results of TRV for typical 1200 kV networks and a sample 1200 kV Indian system using Electromagnetic Transient Programs (EMTP).

Voltage Control of Static Var Compensator for a Remote System Interconnected by Long‐Distance AC Cables

SUMMARYThe voltage variation in a remote system is large when the system is connected by long‐distance AC cables due to the cable capacitance. In Japan, the longest 54‐km 66‐kV AC submarine cable interconnection between the Kyushu mainland and Goto Islands was commissioned in 2005. It was requested to mitigate the voltage variation caused by switching off and on one circuit of the two circuits in the AC cables when a fault occurs. Since the conventional voltage control methods such as transformer tap changer or shunt capacitor and reactor banks are not sufficient because of their slow response time, a static var compensator (SVC) was installed on the Goto Islands. In such an application, an SVC control method should be developed so as not to override the existing voltage control systems. This paper describes the SVC control method developed for the Goto Islands AC interconnection project, which can be applied to similar situations. The effectiveness of the control method was verified by the results of effective value simulation and of field testing, which was implemented before the SVC was commissioned in 2007. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 19–30, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22337

A Voltage Control Method of Static Var Compensator for the Remote System Interconnected by Long Distance AC Cables

The voltage variation in the remote system is large when the system is connected by long distance AC cables due to the cable capacitance. In Japan, the longest 54km 66kV AC submarine cable interconnection between Kyushyu mainland and Goto-islands was commissioned in 2005. It is requested to mitigate the voltage variation caused by switching off and on of one circuit of AC cables out of two circuits when a fault occurs. Since the conventional voltage control methods such as transformer tap changer or shunt capacitor and reactor banks are not sufficient because of their slow response time, therefore an SVC (Static Var Compensator) was installed in Goto-islands. In such application, SVC control method should be developed not to override the existing voltage control systems. This paper describes the SVC control method developed for Goto-islands AC interconnection project, which can be applied to similar applications. The effectiveness of the control method was verified by effective-value-based simulation results and field test results of which implemented before SVC commissioning in 2007.

ANN for multi-objective optimal reactive compensation of a power system with wind generators

In this paper, we develop a method aimed to impose an acceptable voltages profile and to reduce active losses of an electrical supply network including wind generators in real time. These tasks are ensured by acting on capacitor and reactor banks implemented in the load nodes. To solve this problem, we minimize multi-objective functions associated to the active losses and the compensation devices cost under constraints imposed on the voltages and the reactive productions of the various banks. The minimization procedure was realised by the use of evolutionary algorithms. After a training phase, a neural model has the capacity to provide a good estimation of the voltages, the reactive productions and the losses for actual curves of the load and the wind speed, in real time.

Optimal Placement of Reactive Power Compensation Banks for the Maximization of New Generation Capacity

The aim of this paper is to present a novel method for the optimal placement of capacitor and reactor banks, with the objective of maximizing network capacity to absorb new generation. The method is an extension of the Optimal Power Flow used as a tool for network capacity analysis. It can be used to a) plot graphs of the bank investment cost with respect to the increase in network capacity and b) find the optimum investment for the network operator in order to maximize his revenue. A 12-bus low voltage network was used as a test case. The results demonstrate the efficiency of the method to allocate new banks. At a small investment cost, network capacity could nearly double.

Transmission System Parameters Optimization— Sensitivity Analysis of Secondary Arc Current and Recovery Voltage

This paper shows the importance of optimizing the transmission system parameters from its conception, considering the relevant options and possibilities, in order to have a better cost-performance result. The presented results were obtained in the study of a real transmission system expansion, based on a 865-km long line. The single-phase auto-reclosing (SPAR) procedure was one of the aspects carefully studied, in order to assure adequate transmission reliability. The secondary arc current was mitigated through the traditional solution of using the neutral reactor on the existing shunt reactor banks, which permitted the reduction of the secondary arc current to acceptable values, assuring natural arc extinction and successful SPAR. The method of obtaining the optimized value for the neutral reactor and its implications on the system performance are important aspects, and are discussed in this paper.