Research And Application On An Adjustable Reactor Realized By Multi-winding Transformer

The adjustable reactances are general devices of FACTS, which have been widely used for improving the power flow distribution, regulating the reactive power in balanced, stable voltage, improving the stability of the system and so. This paper comprehensively summarizes the research on adjustable reactance at home and abroad status and development trend, and made a detailed introduction on neutral grounding via arc suppression coil. The research topic of this dissertation is multi-winding transformer adjustable reactance and its applications in resonance grounding, it focus on following five parts to carry out studying, these are:mathematical model of multi-winding transformer, the adjustable reactance realized by multi compensation windings with transformer, the graduated adjustable reactance realized by multi-winding transformer, and a novel adjustable reactance is proposed as well as the three kinds of structures reactances applications in neutral resonant grounding.According to the shortage of adjustable reactances realized by multi compensation windings with transformer, the graduated adjustable reactance realized by multi-winding transformer and the novel adjustable reactance are proposed, the main contents of the dissertation are as follows:Taking nine windings transformer for example, the polygon type equivalent circuit model of multi-winding transfomer is presented by resolving the branch-current equation of the multi-winding transformer, the multi-winding inductance matrix is presented by using of ANSYS three-dimensional static magnetic scalar potential value calculated, with the polygon type equivalent circuit model and multi-winding inductance matrix of multi-winding transformer, the mathematical model of multi-winding transformer is established in the Matlab.The simulation model of adjustable reactance implemented by multi compensation windings with transformer is proposed based on mathematical model of a multi-winding transformer, and in the detailed analysis the theory of adjustable reactance. The equivalent impedance of transformer's primary winding can be regulated arbitrarily by controlling the inverter's output current. Arbitrarily structures of transformer can be modeled as T-type equivalent circuit through two-port network control, and the control of multi-winding multi-module system is simple with definite physical meaning, experimental results are given to verify its good performance.Because of the cost high of the adjustable reactance implemented by m multi compensation windings with transformer and the reliability is decreased by the multi-inverter modules structure, the graduated adjustable reactance realized by multi-winding transformer is proposed. Using thyristors and voltage source PWM inverter to be the secondary load of linear transformer, the switched control of thyristors were used in coarse adjustment, by controlling the inverter's output current, which was used in fine adjustment. So that adjustable reactance can be continuously adjustable in each range. The adjustable reactance can be modeled as T-type equivalent circuit in each range through two-port network control, so that the control system is simple with definite physical meaning. In this structure, the capacity of inverter accounts for less percentage, so the whole device cost reduction. Making a close analysis of the reactor design and the selection of inverter parameters, a 3kV/150kVA experimental platform is built.The experimental results are given to verify the continuous-tuning, fast response and limited harmonics generation of the novel adjustable reactor.The resonance theory and the existing ground-to-ground capacitance detection methods is analysed, a novel adjustable reactor is proposed. Make a close analysis of its working principle and apply in arc-suppression coil, using displacement-voltage curve method to detect the capacitance. The adjustable reactor can be modeled as T-type equivalent circuit through two-port network control, so that the control system is simple with definite physical meaning. The simulation studies are given to verify the the novel arc-suppression apparatus has the characteristic of high precision in capacitance detection, When a single-phase grounding fault occurs, the new arc-suppression coil can quickly start the compensation. Experimental results proved that the novel adjustable reactor has the characteristic of continuous-tuning and few harmonics.The adjustable reactances realized by multi compensation windings with transformer and the graduated adjustable reactance realized by multi-winding transformer are both used in arc-suppression coil, the three-phase 10kV dynamic model experiments are carried out on the structure of the two kinds of arc-suppression coil system, The experimental results are given to verify the continuous-tuning, fast response and limited harmonics generation of the two kinds of arc-suppression coil system. Authorized by national professional identify institution, the performances of the both arc-suppression coils satify national standards. Now the lOkV series products of arc-suppression coil realized by multi compensation windings with transformer have been well running in the power utility.