An open-winding permanent magnet motor system with a common bus structure and its control method for suppressing zero-sequence current

Abstract

The invention discloses a permanent magnet motor system with a shared bus structure and an open winding. The permanent magnet motor system comprises a permanent magnet synchronous motor, two current inverters, a direct-current power supply and a controller. The permanent magnet synchronous motor is of an open winding structure. The current inverters are voltage source type three-phase full-bridge inverters. The direct-current sides of the two current inverters are connected to the same direct-current power supply. Due to the fact that the direct-current sides of the two current inverters are connected directly, three current loops are formed in the structure. The invention further discloses a control method for suppressing a zero-sequence current of the permanent magnet motor system. According to the control method, a voltage compensator is designed for correcting the given voltage of the current inverters so that the zero-sequence current can be reduced substantially. According to the permanent magnet motor system, since the two current inverters share the same direct-current power supply, the structure is simple, cost is low, and operating performance and efficiency are high under the condition that the zero-sequence current is well suppressed.

Description

technical field [0001] The invention belongs to the technical field of motors, and in particular relates to an open-winding permanent magnet motor system with a common bus structure and a control method for suppressing zero-sequence current. Background technique [0002] Due to the emergence of permanent magnet materials with high magnetic energy density such as AlNiCo, ferrite and NdFeB, permanent magnet motors have achieved unprecedented development and growth. At the same time, the permanent magnet motor abandons devices such as brushes and collector rings, and does not require excitation windings and excitation power supplies, which greatly reduces the loss of the motor and improves the operational reliability of the motor. Due to its high power density, high efficiency, simple structure and reliable operation, permanent magnet motors have been widely used in various fields such as aerospace, automobiles, national defense and power generation. [0003] In recent years, ...

AI Technical Summary

Problems solved by technology

The structure of the traditional open-winding permanent magnet motor system is as follows: figure 1 As shown, under this structure, the two converters are respectively connected to two isolated DC power supplies. Due to the isolation of the two DC power supplies, there is no zero-sequence current loop in the system. Even if there is a third harmonic in the voltage, no zero-sequence current loop will be generated sequence current, but since the system requires two isolated DC sources, it increases the complexity and cost of the system

However, when the two converters share the same DC power supply, there is a zero-sequence current loop in the corresponding structure, and because there is a back EMF third harmonic in the permanent magnet motor, there will be a zero-sequence current flowing in the system, resulting in low system efficiency and bearing Fever and other issues

[0004] Based on the above considerations, in order to suppress the zero-sequence current, some people propose to connect inductors in series with the three-phase circuit to suppress the magnitude of the third and higher harmonic currents. However, adding inductors in series will increase the hardware cost and complexity of the system. At the same time, it will Increase the loss and reactive power of the system

It has also been suggested that when using voltage space vector modulation, the vector without common-mode voltage is used for modulation to eliminate the zero-sequence voltage generated by the inverter. This method is suitable for induction motors, but for permanent magnet motors, the permanent magnet back EMF There is a third harmonic that cannot be suppressed. At the same time, this method is only based on open-loop control, which is easily affected by various disturbances and has large errors.

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