HTS Controllable Reactor Research Articles

Structure Design and Multiprocess Stress Calculation of HTS Double Pancake of a 35-kV/3.5-MVA Single-Phase HTS-Controllable Reactor

Stress calculation is a key link in evaluating whether the structure of a superconducting magnet is safe. A 35-kV/3.5-MVA single-phase high temperature superconductivity-controllable reactor (HTS-CR) with the HTS winding wound by HTS double pancakes is being developed. The effect on the local stress and temperature rise of HTS double pancakes, which determines the design of the strengthening structure of the HTS double pancake, is studied in this paper. Furthermore, the multiprocess stress development for HTS double pancakes from manufacturing to power-on is also investigated, which discloses the model and the results of the stress calculation. This study can provide a reference for developing HTS-CR with large capacity in the future.

Study on AC Loss Characteristics in HTS Windings of a HTS Controllable Reactor With Orthogonally Configured Core

The controllable reactor is one of the most effective methods for compensating reactive power, which can smoothly and fleetly adjust its output reactance with the change of transmitted power. A high temperature superconducting (HTS) controllable reactor with an orthogonally configured core has been proposed and developed. The HTS windings with direct current (DC) are adopted as the control windings to improve the excitation efficiency. However, under high level excitation condition, especially in the case of fast adjusting process, ac losses will occur and lead to reduction of thermal stability in the HTS windings. The E-J characteristics of HTS windings, magnetization characteristics of iron-core, and 3-D asymmetric structure of the reactor make it difficult to estimate ac loss of the HTS windings based on traditional finite-element methods. This paper proposes a new method to estimate ac loss for the HTS controllable reactor with orthogonally configured core. The ac losses and the critical current of the HTS windings in the reactor are presented and discussed, which has great guiding significance for prototype design.

Saturation and Hysteresis Characteristics Analysis of a HTS Controllable Reactor With Orthogonally Configured Core

The saturated controllable reactor is developed in order to compensate the reactive power in the power system. The traditional reactors have some limitations in the regulation range or induced voltage of control winding. A high temperature superconducting controllable reactor (HTSCR) with orthogonally configured core was proposed and studied, which can overcome some shortcomings of traditional reactors. However, simulation accuracy of the saturation characteristic of the iron core poses a major challenge in the reactor. In this paper, the structure of the reactor is explained and a precise finite element method (FEM) model aims to analyze the saturation and hysteresis characteristics has been modified. The anisotropic feature of the orthogonally configured core has been fully considered. Finite-element analysis simulations based on the anisotropic core model and Jiles-Atherton hysteresis model are performed using COMSOL Multiphysics and compared with verification experiments, proving that the HTS controllable reactor is efficient in reactance regulation, harmonic suppression, and induced voltage reduction.

Excitation Effect Analysis of a Novel HTS Controllable Reactor With Orthogonally Configured Core Based on Dynamic Inductance Matrix

The controllable reactor is one of the most effective methods for compensating reactive power. A novel type of high temperature superconducting (HTS) controllable reactor with orthogonally configured core has been proposed, analyzed, and developed. However, for the controllable reactor with dynamic inductance, the excitation analysis based on field circuit coupled method is inefficient and the excitation parameters optimization is more difficult. In this paper, an excitation system containing a voltage source converter and buck–boost converter is established. The reactor is built as a self-defined nonlinear element in the system model based on the dynamic inductance. The inductance matrix, core saturation, leakage magnetic field at HTS winding, and total magnetic flux in the excitation core are included in the self-defined element. The parameters of the excitation system have been optimized easily. The simulation result of the output characteristic of the reactor is consistent with the experimental observations of the prototype. The dynamic inductance method is proved to be fast and effective.

Development of a New Type of HTS Controllable Reactor With Orthogonally Configured Core

Controllable reactor is widely applied as reactive power compensation device to improve the stability of the power grid. In this paper, a new type of HTS controllable reactor with orthogonally configured core structure has been developed in detail. The basic idea of the reactor is to divide the core into two segments, the working segment on which an ac working winding was wound and the control segment formed by two parallel rectangular magnetic yokes. The dc HTS control windings were wound around the excitation, the impedance of the reactor could be controlled by applying different dc currents to the control coils without the risk of inducing voltage. An optimization algorithm based on the simplified model has been proposed and a prototype has been developed. Laboratory tests were taken under different conditions. Experiment results show that the harmonic content of the inducted current is less than 2% and the adjustable impedance range of the working winding is over 55%.

Electromagnetic Calculation of a 35 kV/3.5 MVA Single-Phase HTS Controllable Reactor With Field–Circuit Coupled-FEM

A controllable reactor is able to compensate a flexible reactive power in a long-distance and an ultrahigh-voltage system. A high-temperature superconductivity controllable reactor (HTS-CR) is a potential equipment in the power system. A method to accomplish the electromagnetic calculation of the HTS-CR is proposed, wherein the field-circuit coupled finite-element method (FCC-FEM) is introduced. Test results of the steady-state current of all the windings of an HTS-CR prototype is compared with the calculation results, which proves the reliability of FCC-FEM. Based on FCC-FEM, the accuracy of the four-probe method, which is used to measure the dc critical current of HTS winding with the criterion 10 -6 V/cm, is studied. Contrary to the four-probe method, a new method based on FCC-FEM, which has better accuracy, is designed to calculate critical current. With FCC-FEM, distributions of the current in the parallel-connected HTS tapes and the ac critical current of the HTS windings for a 35 kV/3.5 MVA single-phase HTS-CR are presented.

Performance Analysis and Prototype Design of a D-Core-Type Single-Phase HTS Controllable Reactor

Controllable reactor is widely applied as a reactive power compensation device to improve the stability of power grid. This paper describes the principle and equivalent magnetic circuit of a new D-core-type HTS controllable reactor in detail. A D-shaped core was assembled with one straight limb, on which an alternating-current working winding was wound, with two parallel rectangular magnetic yokes and four excitation cores between the parallel yokes with direct-current HTS control windings wound around and connected in series with each other. In general, the magnetic flux of the windings for different purposes is orthogonal at the joint and parallel in the parallel yokes. Compared with traditional saturable controllable reactor, the proposed layout can weaken electromagnetic induction between working winding and control windings significantly. Meanwhile, the HTS windings were used to reduce the volume and supply a more effective excitation. In our studies, a 380-V/7.6-kVA single-phase controllable reactor was designed. The reactance, harmonic, and inductive voltage features were analyzed to demonstrate the performance of this type of reactor.

Current and Voltage Distribution Analysis of Control Winding in a 35-kV HTS-CR Considering AC Losses

A 35-kV/100-A high-temperature superconducting controllable reactor (HTS-CR) is under development based on the principle of adjusting the main magnetic flux density and the length of magnetic circuit. The control winding of the HTS-CR is made up of double pancakes (DPCs) that are wound with HTS tapes. In order to increase the current margin of HTS winding, a four-tape bundle conductor is adopted in DPCs. Although tape transportation is utilized to balance the inductance, the current of each parallel conductor should be calculated to get the critical current. In particular, the ac losses caused by the high leakage of flux density on HTS tapes may aggravate imbalance of current and voltage distribution. This paper builds the equivalent circuit model of the parallel conductor and calculates the distribution characteristic of ac losses. Current redistribution has been analyzed by importing the equivalent resistance. Meanwhile, voltages of parallel inductance have been detected to acquire a more intuitive reference, which will provide a basis and support for quench detection and protection.

Design of Superconductivity Windings of a 35-kV/3.5-MVA Single-Phase HTS-Controllable Reactor

In order to compensate flexibly reactive power, it is necessary to develop a controllable reactor in long-distance and ultrahigh-voltage system. High-temperature superconductivity-controllable reactor (HTS-CR) is a potential equipment in power system. A 35-kV/3.5-MVA single-phase HTS-CR is being developed. The HTS windings of the HTS-CR are made of double pancakes that are wound with HTS tapes connected in parallel. The relationship between the number of double pancakes and the number of HTS tapes, which has great effect on the current of each HTS tape, is studied. Furthermore, the solution that reduces the ac loss of the HTS winding is also investigated, which discloses the optimized design parameters and the calculation results of the HTS windings. The study here is believed to provide some references for developing HTS-CR with larger capacity in the future.

Stress Analysis and Bobbin Structure Optimization Design of a 35kV HTS-controllable Reactor

A 35kV high temperature superconducting controllable reactor (HTS-CR) is under development and the electromagnetic design has been completed. Due to the AC conditions, the thermal stress caused by AC losses can be so strong that the stress analysis should be carried out to verify that the maximum stress under different operating conditions is in appropriate range. In addition, Lorentz force of HTS windings will impact the bobbin structure of the HTS windings which will endanger the 35kV HTS-CR. Stress analysis is important for the design of a mechanically stable structure. This paper provides the analysis of the bobbin structure and its result of optimization design considering the requirements of safety and cooling.

Study of a Small-Scale Controllable Reactor and Conceptual Design of a 35kV/5Mvar HTS Reactor

Since Ultra High Voltage (UHV) transmission lines have the high charging capacitance, continuous reactive power compensation is vital for efficient operation of long transmission power lines or cables. A continuous reactive compensation will reduce the transmission losses and increase the transmission capacity of active power. In order to achieve the continuous reactive power compensation, we choose the magnetic saturable type reactor. The principle of a magnetic saturable reactor requires a high current ampere-turn coil as its dc bias, and this coil is necessary to use a high temperature superconducting (HTS) winding. As the first stage of the study, we have constructed a 220V small-scale prototype which the dc bias is made of copper coil instead of the HTS coil. The copper coil of the dc bias in small-scale reactor has the same ampere-turn with a 220V HTS controllable reactor (HCR), so its performance keeps the same except the HTS part. Based on this, we made a conceptual design for a 35kV/5Mvar HCR. The output property and harmonic property have been studied by simulation and experiment. The results prove that it can obtain a continuous controllable reactive power output.

Design and Prototype Test of a High Leakage Reactance Transformer-Based HTS Controllable Reactor

With the development of high voltage long distance transmission and expansion of the grid, continuous reactive power compensation devices, such as controllable reactor, become more and more important. This paper describes the design and prototype test of a high leakage reactance transformer-based high temperature superconducting controllable reactor (HLRT-HTSCR). Characteristics test results show the excellent impedance regulation characteristic of the prototype. DC critical current test of the superconducting winding shows that attention should be paid to the critical current of superconducting coil, avoiding over-current condition. This paper reveals the characteristics of HLRT-HTSCR by experiment, and will be of important practical significance to promote its development.