Fundamental Study On The Key Technology Of Rapid Soft Transfer For Induction Motor Power Supplies

The continuous and reliable power supply sources are needed for the induction motor in the important applications such as the shipboards and the power plants. And the key problems in current stages are how to switch the induction motor to the alternate power source rapidly without the large inrush currents when some faults or routine maintenance on the main power source occur. This dissertation has researched systematically the key technology problems such as rapid soft transfer for induction motor power supplies (RSTIMPS), the complex transient modeling and the control parameters calculation by using the combination method of theoretical analysis, simulation and experimental study. And the main achievements are as follows:1. The suppression mechanisms of the inrush currents during the soft transfer for induction motor power supplies are studied. Then, a rapid soft transfer control method of power supplies is proposed based on the solid state transfer switch (SSTS) for the large inertia induction motor or the light-load motor with the small inertia. And the method can not only realize the power transfer of the induction motor rapidly, but also suppress the inrush currents effectively under the different initial phase angle difference between the main and alternate sources.2. The change laws on the symmetrical and asymmetrical complex transients of motor are found by analyzing the control process of RSTIMPS. Then, the complex transient mathematical models of induction motor, which are favorable to the cohesion of operation states, are builded in the same coordinate system based on the space vector and coordinate transformation. And these models are very effective in the research of the transition process between the three-phase symmetrical and the two-phase asymmetrical operation states of motor.3. The transition processes of RSTIMPS are studied respectively by using the numerical and the analytical calculation method. And the control effectiveness of RSTIMPS under the different initial phase angle difference is explored. What is more, the analytical calculation method based on complex analytical transient vector models of motor is found to have more advantages in the research of this transition process by the comparative analysis of the two calculation methods.4. The stator residual voltage during the power disconnection process of the induction motor is studied accurately. And the variation laws of the stator residual voltage, the voltage difference and phase difference between the residual voltage and the alternate source voltage is revealed which provides the basis for the development of the power transfer schemes. On the basis, two calculation methods for establishing the key parameters of RSTIMPS are put forward with the consideration of the stator residual voltage. And the compensating calculation method of control parameters based on residual voltage vector is beneficial for parameters online calculation and the practical application of RSTIMPS under the different initial phase differences.5. The control prototype machine of RSTIMPS and the experimental platform are designed and developed. And the rapid power soft transfer and the direct transfer for the induction motor are tested abundantly under the different initial phase difference. As a result, the proposed RSTIMPS the complex transient modeling and control parameter calculation are verified to be correct.