Research On Reliability And Starting Current Control Methods Of AC Voltage-Regulating Soft-starter With Thyristor For Asynchronous Motor Of Squirrel-cage

Trigger method's reliability and starting current control strategies of AC voltage-regulate soft-starter is mainly researched in this paper.Firstly, based on the selecting of trigger methods' and ascertaining of the phase shift range of AC voltage-regulate soft starter, reliability of each trigger method is researched. Then, based on the finite state machine (FSM) models the trigger stability problem of AC voltage-regulate circuit is brought forward. Within this frame, the reliability of existing trigger methods is analyzed and compared, including: (1) double-pulse trigger method synchronized by line voltage, (2) wide-pulse trigger method synchronized by line voltage and (3) double-pulses trigger method synchronized by stator current. The conclusion is obtained that the wide-pulse trigger method synchronized by line voltage with 6-gate triggering separately is the best one, the double-pulses trigger method synchronized by stator current is less reliability than the former, and the double-pulses trigger method synchronized by line voltage can not ensure the circuit work reliability. The simulations and experiments prove the conclusion gained above, which has directive significance for research work on 3-phases AC voltage-regulate soft-starter.Secondly, the three models of AC voltage-regulate soft starter are researched in the paper, including: (1) 3 phase conducting model, (2) 2 phase conducting model and (3) none-phase conducting model (disconnect model). Then the mathematic formula of each state (i.e. the state equation of AC voltage-regulate soft-starter) is derived. In deriving formula of 2 phase conducting model, it is the first time that the method of rotating coordinates is adopted to solve coupling successfully. Meanwhile, the formatting methods of simulating programs of the AC voltage-regulate soft-starter are researched and analyzed emphatically, including program with MATLAB / Simulink / Power System Blockset, program with MATLAB/M-file and program with MATLAB / Stateflow, the latest is a novel approach.In the last part of this paper, several control methods are applied to control the starting current of AC voltage-regulate soft-starter. Furthermore, a double-closed-loops control system with current loop and current-close- angle loop is proposed based on single-closed-loop system, and then these two kindsof systems are analyzed and compared. In order to improve the performance of traditional PID controller, fuzzy PID controller is applied to the AC voltage-regulate soft-starter, and a more excellent simulation performance is achieved by this controller than that by the traditional PID controller.