Superconducting Controllable Reactor Works And Prototyping Simulation Analysis

With the rapid development of China’s economy and the continuous improvement of people’s living standards, the demand for electrical energy, which is one of the most important forms of energy, is growing quickly. Under the circumstances, the EHV grid, the UHV gird has been put into operation in many parts of China. In order to limit the over-voltage, to do stratified reactive power balance, fixed parallel high-voltage reactors are generally configured on the line. With the line transmission power changes smoothly and automatically adjust their own capacity to absorb the remaining line inductive reactive power, to prevent the phenomenon of self-excitation of the generator no-load. When the circuit breakers action occurs, it can quickly adjust its reactance, compensate capacitive reactance of transmission lines, restrain the transient overvoltage. Various existing controllable reactor has problems including low accuracy, slow response, complex structure, unsatisfactory harmonic characteristics, lack of continuous and smooth adjustment, high costs more or less. Superconducting controllable reactor can simultaneously achieve three functions of detection, conversion and current-limiting, which needs short response time, and has self-recovery capabilities. Compared to the other similar devices, the superconducting controllable reactor as a kind of ideal devices has obvious advantages.Superconducting controllable reactor which is based on superconducting materials, can be divided into the superconducting controllable reactor with quench and superconducting controllable reactor without quench according to methods of adjust reactance. Superconducting controllable reactor with quench is the traditional superconducting fault current limiter, making the most of the transition characteristics of superconductors’superconducting state between normal state to achieve adjustment of reactance. The shortcoming is that the reactance can’t be adjusted continuously, what’s more, there exists quench protection and the quench recovery problems in practical applications. Superconducting controllable reactor without quench is divided into continuously adjustable superconducting controllable reactor and discontinuously adjustable superconducting controllable reactor. Saturated core superconducting controllable reactor as a discontinuously adjustable superconducting controllable reactor can change the DC bias voltage applied to the superconducting coil to adjust the saturation-core type reactor operating current, solving the problem of quench recovery by the use of two groups core effectively.According to the modeling and simulation of saturated core superconducting controllable reactor, the paper focuses on the steady-state control characteristics, the harmonic characteristics and over-voltage characteristics of short-circuit state. The author shows that changing the DC excitation, adjusting the current of AC winding to change the capacity of the reactor, achieving the purpose of regulating system reactive power. With the continuous increasing the DC voltage, the degree of saturation of the core and the current waveform of AC winding is increasing closing to a sine wave. When the DC voltage increasing to that the core during the week completely work in magnetization curve over saturation area, the current waveform of AC winding could be a sine wave. The harmonic content of AC winding decreases with increasing DC voltage, and finally approaches zero, indicating that the power grid will not cause harmonic pollution.The author research on simulation analysis on the racetrack-core type, the three-limb-core type and D-core saturated iron core superconducting controllable reactor electromagnetic designs. The racetrack-core type superconducting controllable reactor inductance value can be continuously adjustable, which is apply in high-voltage large-capacity conditions. The reaction rate is relatively fast, the capacity adjustment range is wide, but it requires the use of special wiring and control systems designed to reduce harmonics. The three-limb-core type superconducting controllable reactor can achieve the inductance value be continuously adjustable, and capacity adjustment range of the reactor can be wide, but the magnetic field lines of the reactor core distribution is very uneven, resulting in magnetic flux leakage of the reactor, which will cause a great impact on the quality of the electrical energy. In addition, the inductance value adjustment change linearity is not as good as the racetrack-core type superconducting controllable reactor. D-core saturated core controllable reactor inductance has better stability, lower harmonics, but the structure is complicated. It’s difficult to achieve machining process next to the yoke of the absolute symmetry. Apart from that, control of the DC control winding is complex.