| With the development of modern industry, power electronic technology, microelectronics technology and control technology are developing progressively. Three phase AC asynchronous motor with the advantages of simple structure, light volume and weight, low cost, reliable operation is used widely in many fields and plays an important role. The starting procedure of asynchronous motor affects the state grid directly and the disadvantage is arising for power device. The starting current can reach 4~ 8 times or even more times of the rated current of the motor. Large starting current will affect the safe operation of the state grid. Therefore, researching on new type of soft starter to reduce the starting current of motor starting, increase the starting torque, and reduce the impact on the grid has important economic value and social significance.This paper mainly studies how to use the principle of voltage space vector to improve the starting performance and starting torque of asynchronous motor, and studies the design of hardware and software control system of the soft starter based on voltage space vector.The main work as follows:1) The principle of asynchronous motor soft-starter is analyzed. The relationship of AC asynchronous motor electromagnetic torque and the stator voltage, the power frequency, also working theory, merits and drawbacks and others of current soft starting methods are analyze one by one.2)The soft starting main circuit principle structure whose power device is all controlled device IGBT is designed. The performance of asynchronous motor is analyzed in detail and the control method to increase the starting torque with voltage space vector. The change of voltage frequency is realized by controlling the work time of switch trigger angle, and the asynchronous motor voltage space vector soft starting control model is established in the MATLAB/SIMULINK simulation platform, also the all vector control system is simulated and analyzed, then the simulation result is got and the feasibility of this design is verified.3)A new type of soft starter with voltage space vector control strategy based on dodecagon flux trajectory control is developed and the software and hardware of this new soft-starter is designed. The new type soft-starter use the dodecagon flux trajectory control of voltage space vector control algorithm, regulate the supply voltage and the frequency of the power supply at the same time, and keep the voltage/frequency ratio stable, keep the main magnetic flux of motor stable, get bigger starting torque while starting current is low. It can start with a certain load or high inertia load motor while the current is in a relatively small value, and the asynchronous motor starting with smaller current and bigger torque is realized.4) The hardware circuit of the fully controlled voltage space vector soft-starter is designed. It includes master chip STM32 circuit, communication circuit, current detection circuit, CPLD(Complex Programmable Logic Device)circuit, voltage detection circuit, drive circuit, power circuit and others. The CPU(STM32) mainly to complete the arithmetic operation and operation monitoring, and CPLD is mainly to combine the STM32 to produce soft-starter control trigger signals and extended the logic features of STM32 that make both excellent performance into full play. This approach allows CPLD resources are well used, and higher quality control trigger is obtained, then the high power and high reliability control requirements are met. Meanwhile, soft-stopping and system protection are achieved in this system.In this paper, the realization of the whole control system is accomplished in the voltage space vector, and completed the performance test, gives the corresponding results and comparison. Results show that this new type of soft starter on load capability is strong, has the advantages of small starting current and big starting torque. Finally, the paper analysis the disadvantages of the system, and give the improved method. |
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