基于多步模型预测控制的多电平交流调速系统具有电机转矩脉动小、高动态性能、电压变化率小和控制灵活等优点在电力牵引等中高压调速系统得到广泛的关注和应用。然而，常规多电平交流调速系统的多步模型预测控制存在计算复杂和输出开关频率不固定等问题。本项目通过球形译码算法和目标函数调制算法分别实现多电平交流调速系统多步模型预测控制的快速和定频。主要研究内容如下：①建立多电平调速系统多步预测模型和目标函数。②研究基于球形译码算法多电平调速系统快速的多步模型预测算法，确定多步模型预测算法局部寻优和全局寻优内在联系和等效条件。③研究基于目标函数调制算法多电平调速系统定频的多步模型预测算法。④融合快速多步预测算法和定频多步预测算法，进一步建立混合钳位六电平调速系统数字化实验平台。本项目的开展，构建多电平交流调速系统快速定频的多步预测理论与方法，对促进电力牵引等中高压调速系统的发展和应用具有重要的理论与实践意义。

The multi-level AC variable speed system based on multi-step model predictive control (MPC) has many advantages such as small motor torque ripple, high dynamic response, small voltage change rate, flexible control and so on, which has been received extensive concerns and applications in medium-high voltage variable speed systems such as electric tractions. However, the traditional multi-step MPC for multi-level AC variable speed systems has disadvantages such as computational complexity and unfixed switching frequency. The project achieves fast and fixed switching frequency (FSF) for multi-level AC variable speed systems by the sphere decoding algorithm and the objection function modulation algorithm, respectively. The main research contents of the project are as follows: ① Establish the multi-step predictive models and the objection function for multi-level variable speed systems. ② Study the fast multi-step MPC based on the sphere decoding algorithm for multi-level variable speed systems, and ensure the intrinsic relationship and equivalent conditions for the local optimization and the global optimization of the multi-step MPC. ③ Research the FSF multi-step MPC based on the objection function modulation algorithm for multi-level variable speed systems. ④ Combine the fast multi-step MPC and the FSF multi-step MPC, and further establish digital experimental platform for hybrid-clamped six-level variable speed systems. A multi-step predictive theories and methods of the fast and FSF MPC for multi-level AC variable speed systems by developing the project will be constructed, which has important theoretical and practical significances for promoting the development and application of medium-high voltage variable speed systems such as electric tractions.