Shifeng Shen

Development of a Leakage Flux-Controlled Reactor

In order to flexibly compensate reactive power, it is necessary to develop a controllable reactor in long distance and ultrahigh voltage system. A leakage flux-controlled reactor (LFCR) is developed in this paper. The operation principles of LFCR are discussed in detail, and a 380 V single-phase LFCR prototype is developed. Relevant experiments have been done to test its performance. The results of the experiments indicate that LFCR has no harmonic and the reactance of LFCR is stable. Also, LFCR with two control windings can realize four kinds of reactance adjustment rates: 1.94%, 75.99%, 90.53%, and 99.05%.

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.

Evaluation of Three Designs for a 35-kV Class Superconducting Reactor

With the expansion of the grid, continuous reactive power compensation is vital for efficient operation of long transmission power lines or cables. Yunnan Electric Power Grid Company is planning to develop superconducting controllable reactors for 500-kV long-distance ac transmission lines. As the second stage of the development plan, a 35-kV class superconducting reactor will be designed and verified by experiments. In this paper, three design proposals, including the racetrack-core type, the three-limb-core type, and the D-core type, for the 35-kV class superconducting reactor are given. Then, their technical and economic feasibility is evaluated. This paper shows that the racetrack-core saturable reactor is a good choice from a technical and economic point of view.

The Effect of Flux Diverters on Energy Storage Capacity and Heat Losses in a HTS SMES

Energy storage capacity and the heat losses are key factors in superconducting magnetic energy storage (SMES). In this paper, the use of flux diverters to increase the energy storage capacity and reduce the heat losses is analyzed in a HTS SMES magnet. The analysis is carried out using a 100 kJ SMES model based on FEM. The location, the geometry shape and the material configuration of flux diverters are investigated. To get an accurate loss reduction, magnetic losses of flux diverters are considered in heat loss calculation. The results show flux diverters are effective in the rated condition. Because the flux distribution is affected by the saturation level of flux diverters, the effect is related to the operating current.

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.

Design of Cryogenic Cooling System 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 ultrahighvoltage systems. A 35-kV/3.5-MVA single-phase high-temperature superconductivity-controllable reactor (HTS-CR) is being developed. The control windings of the HTS-CR are made of HTS. The closed-cycle cooling method with the subcooled liquid nitrogen (LN) flowing in the cryogenic cooling system of the HTS-CR is introduced to cool down the HTS windings. The number and the layout of both the inlet pipes and the outlet pipes of the cooling system, which has great effect on the temperature rise of the HTS winding, are studied. Furthermore, the flow velocity of the subcooled LN of the inlet pipes is also investigated, which discloses the optimized structure design of the cryogenic cooling system. The study here is believed to provide some references for developing HTS-CR with larger capacity in the future.

Numerical Simulation of Coupled Heat Transfer, Stress, and Electromagnetic Properties in an SMES Magnet

This paper describes the analysis procedure and FEM model considering the parallel effects of stress and thermal problem coupled with the electromagnetic field problem of a 10 MJ Superconducting Magnetic Energy Storage (SMES) magnet. Since the coupled processes in most analyses are very simplified or even not considered, the general aim of this paper was to create, solve, and validate a numerical model of the coupled stress and thermal phenomena that occur within an SMES magnet. A finite element model has been developed to solve the coupling of the magnetic field, stress, and thermal problems. Temperature and stress distribution of the SMES magnet in two operating conditions are simulated, taking into account the eddy current, ac loss, and heat conduction. This provides useful insight for optimized coil design and condition assessment of SMES.

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.

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.