Research On Dynamic Characteristic Optimization Of Magnetically Controlled Reactors

Magnetically controlled reactor (MCR) is a kind of static var compensator with a variable inductance. The core magnetic saturation degree can be changed by controlling the direct current with thyristors. MCR has advantages of simple control, continuous adjustment over the traditional static var compensator. However, there is still some optimized space, such as losses, response time, control and harmonic characteristic etc. In this paper, the ontology structure design of MCR and its dynamic transition process are studied. In addition, the methods of modifying its performance are researched.Based on the basic circuit principle, this paper derives the electromagnetic equations and the mathematical model. Then the control characteristic, response characteristics, and loss of MCR have been researched. A software is compiled in Matlab to provide a theoretical basis for practical engineering MCR designing.Based on the electromagnetic field theory, the model of a parameter-known reactor is enstablished in the field-circuit coupled simulation system of ANSYS Maxwell and Simplorer which are the finite element simulation softwares. The loss characteristic of MCR is studied. The magnetic flux density distribution field plot is obtained by simulation. It is verified that two core limb of MCR saturated alternatively in one power frequency cycle. After the simulation results of the magnetic field are analyzed, the factors that influence the loss of reactor is studied. The simulation results of model with several modified core construction is compared. The result illustrates that using an internal segmented magnetic valve structure can reduce the edge effect and horizontal component of the magnetic flux leakage. It can also be used as a feasible measure to minimize the loss.The general model of the reactor was established in Matlab/Simulink. The response characteristic of MCR is verified by simulink. A fast excitation circuit composed of a PWM rectifier is designed. It makes the reactor increase the direct voltage control rapidly in the process of excitation. The simulation verifies the response speed of the fast excitation circuit is superior to the ordinary reactor with self-coupled, its reaponse time decreases from 0.28s to 0.12s.Aiming at the electrified railway reactive power shortage phenomenon, this paper establishes a dynamic reactive compensation system simulation model with MCR. The simulation results show that the line side power factor is improved obviously after inputting the compensation device. But it takes a long time to start. The discharge of Active Power Filter (APF) direct side capacitor can increase the MCR direct control voltage, which can shorten the response time. The combined compensation system with MCR and small capacity APF to optimize the response characteristics of MCR is put forward. The simulation results show that the response time of MCR can reduce from 10 power frequency cycles to 3. The superiority of the comprehensive compensation system is verified.