Weak magnetic control method for high speed permanent magnet synchronous generator system
In view of the current development trend of generator system, this paper proposes a control strategy based on permanent magnet synchronous generator system, which can make the system run in a higher speed region. In the whole process of starting, the control strategy uses the current loop as the inner loop, and the speed loop and the bus voltage loop are respectively used as the outer loop. Aiming at the widening range of rotational speed, this paper focuses on a simplified analytical weak magnetic control method and verifies the feasibility of the bus voltage loop under the weak magnetic control method. Finally, the simulation results show that the control strategy can ensure the expected operation of the system during the whole process.
1 Introduction
In recent years, in the fields of aviation, high-speed trains, electric vehicles, ships, etc., generators have been used more and more widely, and gradually become the core part of the power generation system. The generator not only assumes the main role of the power supply in the power grid, but also plays the role of the starting prime mover by means of the external power supply. Combined with the above two functions, the generator will further enhance the competitiveness of its power generation system in terms of weight and volume. This paper mainly explores a control strategy based on permanent magnet synchronous generator system, and expands the range of speed change during the power generation stage in response to the development needs of the system.
In general, when the generator is running to high speed, the output voltage of the generator will rise correspondingly, so that the output voltage of the DC bus terminal is not controlled. Therefore, the weak magnetic control is needed to adjust the output voltage of the generator side. The traditional weak magnetic control methods mainly include analytical method, voltage feedback method, lead angle method and switching time feedback method. The latter three methods use the PI regulator in the process of generating the d-axis current reference value, and the parameter design of the PI regulator becomes more difficult in the widened speed range. In addition, the surface-mount permanent magnet is used in this paper. Synchronous motor as the generator, the analytical expression used in the analytical method will be greatly simplified, so for the research of this paper, it is more suitable to use the analytical method for weak magnetic control.
When the generator is running to high speed, it will enter the power generation phase. Depending on the structure of the system, the control strategy at this time can use the DC bus current or voltage as the outer loop control variable. The former is usually used when the system is running in parallel with other power supplies. In this paper, only the independent operation of the system is considered. Since the latter has better voltage output characteristics, the bus voltage is used as the outer loop control variable in the power generation phase. In the following paper, we will focus on the feasibility of the closed-loop voltage of the busbar when using the analytical field weakening control method in the widened speed range.
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