电励磁同步电机具有调速范围宽、过载能力强、功率因数可调等优点，广泛应用于大功率传动领域。为此,介绍了一种中性点钳位型（NPC）三电平高压变频器的系统结构及中性点电压平衡控制策略。采用电流频率（IF）控制和滑模观测器（SMO）相结合的无速度传感器矢量控制策略，控制电励磁同步电机变频起动与运行。MATLAB仿真结果验证了采用所提控制策略的变频器具有良好的起动和运行性能，为高压大功率传动应用领域提供了技术保障。

Electrically excited synchronous motor has the advantages of wide speed range, strong overload capability and adjustable power factor. It is widely used in the field of high power transmission. The system structure and the neutral point voltage balance control strategy of a neutral point clamped (NPC) three-level high voltage converter are introduced for this purpose. Speed sensorless vector control strategy based on current frequency (IF) control and sliding mode observer (SMO) is used to control the variable frequency starting and speed regulating of electrically excited synchronous motor. The MATLAB simulation results show that the converter has good startup and operation performance due to the adoption of the proposed control strategy. It provides technical support for high voltage and high power transmission applications.